U.S. patent application number 13/278597 was filed with the patent office on 2012-02-09 for al2o3-rare earth oxide-zro2/hfo2 materials, and methods of making and using the same.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Anatoly Z. Rosenflanz.
Application Number | 20120035046 13/278597 |
Document ID | / |
Family ID | 25447167 |
Filed Date | 2012-02-09 |
United States Patent
Application |
20120035046 |
Kind Code |
A1 |
Rosenflanz; Anatoly Z. |
February 9, 2012 |
Al2O3-RARE EARTH OXIDE-ZrO2/HfO2 MATERIALS, AND METHODS OF MAKING
AND USING THE SAME
Abstract
Al.sub.2O.sub.3-rare earth oxide-ZrO.sub.2/HfO.sub.2 ceramics
(including glasses, crystalline ceramics, and glass-ceramics) and
methods of making the same. Ceramics according to the present
disclosure can be made, formed as, or converted into glass beads,
articles (e.g., plates), fibers, particles, and thin coatings. The
particles and fibers are useful, for example, as thermal
insulation, filler, or reinforcing material in composites (e.g.,
ceramic, metal, or polymeric matrix composites). The thin coatings
can be useful, for example, as protective coatings in applications
involving wear, as well as for thermal management. Certain ceramic
particles according to the present disclosure can be are
particularly useful as abrasive particles.
Inventors: |
Rosenflanz; Anatoly Z.;
(Maplewood, MN) |
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
25447167 |
Appl. No.: |
13/278597 |
Filed: |
October 21, 2011 |
Related U.S. Patent Documents
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Application
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Filing Date |
Patent Number |
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12773535 |
May 4, 2010 |
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13278597 |
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11768806 |
Jun 26, 2007 |
7737063 |
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12773535 |
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10211597 |
Aug 2, 2002 |
7563293 |
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11768806 |
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09922527 |
Aug 2, 2001 |
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10211597 |
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Current U.S.
Class: |
501/135 ;
501/134; 501/152 |
Current CPC
Class: |
C04B 2235/5427 20130101;
C04B 2235/3224 20130101; C04B 2235/3239 20130101; C03C 1/00
20130101; C04B 2235/3206 20130101; C04B 2235/3229 20130101; C04B
2235/401 20130101; Y10T 428/257 20150115; C04B 35/106 20130101;
C04B 2235/528 20130101; C04B 35/50 20130101; C04B 2235/3232
20130101; C04B 2235/96 20130101; C04B 2235/3251 20130101; C04B
2235/3244 20130101; C04B 2235/447 20130101; C04B 2235/3246
20130101; C04B 2235/445 20130101; Y10T 428/252 20150115; C04B
2235/3279 20130101; C03B 19/1005 20130101; C04B 2235/3262 20130101;
C09K 3/1409 20130101; C04B 2235/3409 20130101; C04B 2235/3265
20130101; C04B 2235/402 20130101; C03C 3/062 20130101; C04B 35/645
20130101; C04B 2235/3418 20130101; C04B 2235/3241 20130101; C04B
2235/3217 20130101; C04B 2235/3225 20130101; C04B 2235/3272
20130101; Y02P 40/57 20151101; C03C 12/00 20130101; C03C 3/125
20130101; C04B 35/44 20130101; C04B 2235/3208 20130101; C04B
2235/3213 20130101; C04B 2235/3248 20130101; C04B 2235/3222
20130101; C04B 2235/3275 20130101; C04B 35/62236 20130101; Y10T
428/26 20150115; C04B 2235/3281 20130101; C04B 2235/785 20130101;
C04B 2235/80 20130101; C03C 10/00 20130101; C09K 3/1427 20130101;
C04B 2235/9646 20130101; C04B 2235/3227 20130101; C09K 3/1418
20130101; C04B 2235/5436 20130101 |
Class at
Publication: |
501/135 ;
501/134; 501/152 |
International
Class: |
C04B 35/50 20060101
C04B035/50; C04B 35/505 20060101 C04B035/505 |
Claims
1. A pavement marking, comprising: transparent microspheres
comprising: between about 35 wt % to about 40 wt % of one or more
metal oxides selected from lanthanide series oxides and yttrium
oxide; at least about 30 wt % Al.sub.2O.sub.3; at least 30 wt % of
one or more metal oxides selected from the group consisting of
ZrO.sub.2, TiO.sub.2, BaO, SrO, CaO, and MgO and mixtures
thereof.
2. The pavement marking of claim 1, wherein the microspheres
comprise between about 5 wt % and about 30 wt % ZrO.sub.2.
3. The pavement marking of claim 2, wherein the microspheres
comprise at least 21 wt % of one or more metal oxides selected from
the group consisting essentially of TiO.sub.2, BaO, SrO, CaO, and
MgO.
4. The pavement marking of claim 1, wherein the microspheres
include at least 13 wt % of one or more metal oxides selected from
the group consisting essentially of TiO.sub.2 and CaO.
5. The pavement marking of claim 2, wherein the microspheres
include at least 10 wt % of CaO.
6. The pavement marking of claim 2, wherein the microspheres
comprise: 2 to 20 wt % TiO.sub.2; and at least 9 wt % of CaO.
7. A pavement marking, comprising: transparent microspheres
comprising: between about 35 wt % and about 41 wt % of one or more
metal oxides selected from lanthanide series oxides and yttrium
oxide; at least about 30 wt % Al.sub.2O.sub.3; between about 5 wt %
to about 30 wt % ZrO.sub.2, and at least 24 wt % of one or more
metal oxides selected from a group consisting essentially of
TiO.sub.2, BaO, SrO, CaO, and MgO.
8. A pavement marking, comprising: transparent microspheres
comprising: between about 20 wt % and about 39 wt % of one or more
metal oxides selected from lanthanide series oxides and yttrium
oxide; at least about 30 wt % Al.sub.2O.sub.3, and between about 5
and about 39 wt % ZrO.sub.2, and at least 8 wt % CaO.
9. The pavement marking of claim 8, wherein the transparent
microspheres comprise: between about 20 wt % and about 37 wt % of
one or more metal oxides selected from lanthanide series oxides and
yttrium oxide, between about 2 wt % and about 20 wt % TiO.sub.2,
and at least 19 wt % of one or more metal oxides selected from the
group consisting essentially of ZrO.sub.2, BaO, SrO, CaO, and
MgO.
10. The pavement marking of claim 8, wherein the transparent
microspheres comprise: between about 20 wt % and about 39 wt % of
one or more metal oxides selected from lanthanide series oxides and
yttrium oxide; between about 2 wt % and about 20 wt % TiO.sub.2,
and at least 6 wt % CaO.
11. The pavement marking of claim 8, wherein the pavement marking
is a pavement marking tape.
Description
[0001] This application is a division of U.S. patent application
Ser. No. 12/773,535, filed May 4, 2010; which is a division of U.S.
patent application Ser. No. 11/768,806, filed Jun. 26, 2007, now
U.S. Pat. No. 7,737,063; which is a continuation of U.S. patent
application Ser. No. 10/211,597, filed Aug. 2, 2002, now U.S. Pat.
No. 7,563,293; which is a continuation-in-part of U.S. patent
application Ser. No. 09/922,527, filed Aug. 2, 2001, now abandoned,
the disclosures of which are incorporated by reference in their
entirety herein.
TECHNICAL FIELD
[0002] The present disclosure relates to Al.sub.2O.sub.3-rare earth
oxide-ZrO.sub.2/HfO.sub.2 (including amorphous materials (including
glasses), crystalline ceramics, and glass-ceramics) and methods of
making the same.
DESCRIPTION OF RELATED ART
[0003] A large number of amorphous (including glass) and
glass-ceramic compositions are known. The majority of oxide glass
systems utilize well-known glass-formers such as SiO.sub.2,
B.sub.2O.sub.3, P.sub.2O.sub.5, GeO.sub.2, TeO.sub.2,
As.sub.2O.sub.3, and V.sub.2O.sub.5 to aid in the formation of the
glass. Some of the glass compositions formed with these
glass-formers can be heat-treated to form glass-ceramics. The upper
use temperature of glasses and glass-ceramics formed from such
glass formers is generally less than 1200.degree. C., typically
about 700-800.degree. C. The glass-ceramics tend to be more
temperature resistant than the glass from which they are
formed.
[0004] In addition, many properties of known glasses and
glass-ceramics are limited by the intrinsic properties of
glass-formers. For example, for SiO.sub.2, B.sub.2O.sub.3, and
P.sub.2O.sub.5-based glasses and glass-ceramics, the Young's
modulus, hardness, and strength are limited by such glass-formers.
Such glass and glass-ceramics generally have inferior mechanical
properties as compared, for example, to Al.sub.2O.sub.3 or
ZrO.sub.2. Glass-ceramics having any mechanical properties similar
to that of Al.sub.2O.sub.3 or ZrO.sub.2 would be desirable.
[0005] Although some non-conventional glasses such as glasses based
on rare earth oxide-aluminum oxide (see, e.g., PCT application
having publication No. WO 01/27046 A1, published Apr. 19, 2001, and
Japanese Document No. JP 2000-045129, published Feb. 15, 2000) are
known, additional novel glasses and glass-ceramic, as well as use
for both known and novel glasses and glass-ceramics is desired.
[0006] In another aspect, a variety of abrasive particles (e.g.,
diamond particles, cubic boron nitride particles, fused abrasive
particles, and sintered, ceramic abrasive particles (including
sol-gel-derived abrasive particles) known in the art. In some
abrading applications, the abrasive particles are used in loose
form, while in others the particles are incorporated into abrasive
products (e.g., coated abrasive products, bonded abrasive products,
non-woven abrasive products, and abrasive brushes). Criteria used
in selecting abrasive particles used for a particular abrading
application include: abrading life, rate of cut, substrate surface
finish, grinding efficiency, and product cost.
[0007] From about 1900 to about the mid-1980's, the premier
abrasive particles for abrading applications such as those
utilizing coated and bonded abrasive products were typically fused
abrasive particles. There are two general types of fused abrasive
particles: (1) fused alpha alumina abrasive particles (see, e.g.,
U.S. Pat. No. 1,161,620 (Coulter), U.S. Pat. No. 1,192,709 (Tone),
U.S. Pat. No. 1,247,337 (Saunders et al.), U.S. Pat. No. 1,268,533
(Allen), and U.S. Pat. No. 2,424,645 (Baumann et al.)) and (2)
fused (sometimes also referred to as "co-fused") alumina-zirconia
abrasive particles (see, e.g., U.S. Pat. No. 3,891,408 (Rowse et
al.), U.S. Pat. No. 3,781,172 (Pett et al.), U.S. Pat. No.
3,893,826 (Quinan et al.), U.S. Pat. No. 4,126,429 (Watson), U.S.
Pat. No. 4,457,767 (Poon et al.), and U.S. Pat. No. 5,143,522
(Gibson et al.)) (also see, e.g., U.S. Pat. No. 5,023,212 (Dubots
et. al) and U.S. Pat. No. 5,336,280 (Dubots et. al) which report
the certain fused oxynitride abrasive particles). Fused alumina
abrasive particles are typically made by charging a furnace with an
alumina source such as aluminum ore or bauxite, as well as other
desired additives, heating the material above its melting point,
cooling the melt to provide a solidified mass, crushing the
solidified mass into particles, and then screening and grading the
particles to provide the desired abrasive particle size
distribution. Fused alumina-zirconia abrasive particles are
typically made in a similar manner, except the furnace is charged
with both an alumina source and a zirconia source, and the melt is
more rapidly cooled than the melt used to make fused alumina
abrasive particles. For fused alumina-zirconia abrasive particles,
the amount of alumina source is typically about 50-80 percent by
weight, and the amount of zirconia, 50-20 percent by weight
zirconia. The processes for making the fused alumina and fused
alumina abrasive particles may include removal of impurities from
the melt prior to the cooling step.
[0008] Although fused alpha alumina abrasive particles and fused
alumina-zirconia abrasive particles are still widely used in
abrading applications (including those utilizing coated and bonded
abrasive products, the premier abrasive particles for many abrading
applications since about the mid-1980's are sol-gel-derived alpha
alumina particles (see, e.g., U.S. Pat. No. 4,314,827 (Leitheiser
et al.), U.S. Pat. No. 4,518,397 (Leitheiser et al.), U.S. Pat. No.
4,623,364 (Cottringer et al.), U.S. Pat. No. 4,744,802 (Schwabel),
U.S. Pat. No. 4,770,671 (Monroe et al.), U.S. Pat. No. 4,881,951
(Wood et al.), U.S. Pat. No. 4,960,441 (Pellow et al.), U.S. Pat.
No. 5,139,978 (Wood), U.S. Pat. No. 5,201,916 (Berg et al.), U.S.
Pat. No. 5,366,523 (Rowenhorst et al.), U.S. Pat. No. 5,429,647
(Larmie), U.S. Pat. No. 5,547,479 (Conwell et al.), U.S. Pat. No.
5,498,269 (Larmie), U.S. Pat. No. 5,551,963 (Larmie), and U.S. Pat.
No. 5,725,162 (Garg et al.)).
[0009] The sol-gel-derived alpha alumina abrasive particles may
have a microstructure made up of very fine alpha alumina
crystallites, with or without the presence of secondary phases
added. The grinding performance of the sol-gel derived abrasive
particles on metal, as measured, for example, by life of abrasive
products made with the abrasive particles was dramatically longer
than such products made from conventional fused alumina abrasive
particles.
[0010] Typically, the processes for making sol-gel-derived abrasive
particles are more complicated and expensive than the processes for
making conventional fused abrasive particles. In general,
sol-gel-derived abrasive particles are typically made by preparing
a dispersion or sol comprising water, alumina monohydrate
(boehmite), and optionally peptizing agent (e.g., an acid such as
nitric acid), gelling the dispersion, drying the gelled dispersion,
crushing the dried dispersion into particles, screening the
particles to provide the desired sized particles, calcining the
particles to remove volatiles, sintering the calcined particles at
a temperature below the melting point of alumina, and screening and
grading the particles to provide the desired abrasive particle size
distribution. Frequently a metal oxide modifier(s) is incorporated
into the sintered abrasive particles to alter or otherwise modify
the physical properties and/or microstructure of the sintered
abrasive particles.
[0011] There are a variety of abrasive products (also referred to
"abrasive articles") known in the art. Typically, abrasive products
include binder and abrasive particles secured within the abrasive
product by the binder. Examples of abrasive products include:
coated abrasive products, bonded abrasive products, nonwoven
abrasive products, and abrasive brushes.
[0012] Examples of bonded abrasive products include: grinding
wheels, cutoff wheels, and honing stones. The main types of bonding
systems used to make bonded abrasive products are: resinoid,
vitrified, and metal. Resinoid bonded abrasives utilize an organic
binder system (e.g., phenolic binder systems) to bond the abrasive
particles together to form the shaped mass (see, e.g., U.S. Pat.
No. 4,741,743 (Narayanan et al.), U.S. Pat. No. 4,800,685 (Haynes
et al.), U.S. Pat. No. 5,037,453 (Narayanan et al.), and U.S. Pat.
No. 5,110,332 (Narayanan et al.)). Another major type are vitrified
wheels in which a glass binder system is used to bond the abrasive
particles together mass (see, e.g., U.S. Pat. No. 4,543,107 (Rue),
U.S. Pat. No. 4,898,587 (Hay et al.), U.S. Pat. No. 4,997,461
(Markhoff-Matheny et al.), and U.S. Pat. No. 5,863,308 (Qi et
al.)). These glass bonds are usually matured at temperatures
between 900.degree. C. to 1300.degree. C. Today vitrified wheels
utilize both fused alumina and sol-gel-derived abrasive particles.
However, fused alumina-zirconia is generally not incorporated into
vitrified wheels due in part to the thermal stability of
alumina-zirconia. At the elevated temperatures at which the glass
bonds are matured, the physical properties of alumina-zirconia
degrade, leading to a significant decrease in their abrading
performance. Metal bonded abrasive products typically utilize
sintered or plated metal to bond the abrasive particles.
[0013] The abrasive industry continues to desire abrasive particles
and abrasive products that are easier to make, cheaper to make,
and/or provide performance advantage(s) over conventional abrasive
particles and products.
SUMMARY
[0014] The present disclosure provides ceramics comprising (on a
theoretical oxide basis; e.g., may be present as a reaction product
(e.g., CeAl.sub.11O.sub.18)), Al.sub.2O.sub.3, REO, and at least
one of ZrO.sub.2 or HfO.sub.2, including glass, crystalline ceramic
(e.g., crystallites of a complex metal oxide(s) (e.g., complex
Al.sub.2O.sub.3.REO) and/or ZrO.sub.2), and glass-ceramic
materials, wherein in amorphous materials not having a T.sub.g,
certain preferred embodiments have x, y, and z dimensions each
perpendicular to each other, and wherein each of the x, y, and z
dimensions is at least 5 mm (in some embodiments at least 10 mm),
the x, y, and z dimensions is at least 30 micrometers, 35
micrometers, 40 micrometers, 45 micrometers, 50 micrometers, 75
micrometers, 100 micrometers, 150 micrometers, 200 micrometers, 250
micrometers, 500 micrometers, 1000 micrometers, 2000 micrometers,
2500 micrometers, 1 mm, 5 mm, or even at least 10 mm. The x, y, and
z dimensions of a material are determined either visually or using
microscopy, depending on the magnitude of the dimensions. The
reported z dimension is, for example, the diameter of a sphere, the
thickness of a coating, or the longest length of a prismatic
shape.
[0015] Some embodiments of ceramic materials according to the
present disclosure may comprise, for example, less than 40 (35, 30,
25, 20, 15, 10, 5, 3, 2, 1, or even zero) percent by weight
traditional glass formers such as SiO.sub.2, As.sub.2O.sub.3,
B.sub.2O.sub.3, P.sub.2O.sub.5, GeO.sub.2, TeO.sub.2, V.sub.2,
O.sub.5, and/or combinations thereof, based on the total weight of
the ceramic. Ceramics according to the present disclosure may
comprise, for example, at least 1, 2, 3, 5, 10, 15, 20, 25, 30, 35,
40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or even 100 percent
by volume amorphous material. Some embodiments of ceramics
according to the present disclosure may comprise, for example, at
least 1, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65,
70, 75, 80, 85, 90, 95, 97, 98, 99, or even 100 percent by volume
crystalline ceramic, based on the total volume of the ceramic.
[0016] Typically, ceramics according to the present disclosure
comprises at least 30 percent by weight of the Al.sub.2O.sub.3,
based on the total weight of the ceramic. More typically, ceramics
according to the present disclosure comprise at least 30
(desirably, in a range of about 30 to about 60) percent by weight
Al.sub.2O.sub.3, at least 20 (desirably in a range of about 20 to
about 65) percent by weight REO, and at least 5 (desirably in a
range of about 5 to about 30) percent by weight ZrO.sub.2 and/or
HfO.sub.2, based on the total weight of the ceramic. The weight
ratio of ZrO.sub.2:HfO.sub.2 can range of 1:zero (i.e., all
ZrO.sub.2; no HfO.sub.2) to zero:1, as well as, for example, at
least about 99, 98, 97, 96, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50,
45, 40, 35, 30, 25, 20, 15, 10, and 5 parts (by weight) ZrO.sub.2
and a corresponding amount of HfO.sub.2 (e.g., at least about 99
parts (by weight) ZrO.sub.2 and not greater than about 1 part
HfO.sub.2) and at least about 99, 98, 97, 96, 95, 90, 85, 80, 75,
70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, and 5 parts
HfO.sub.2 and a corresponding amount of ZrO.sub.2. Optionally,
ceramics according to the present disclosure further comprise
Y.sub.2O.sub.3.
[0017] For ceramics according to the present disclosure comprising
crystalline ceramic, some embodiments include those wherein the
ceramic (a) exhibits a microstructure comprising crystallites
(e.g., crystallites of a complex metal oxide(s) (e.g., complex
Al.sub.2O.sub.3.REO) and/or ZrO.sub.2) having an average
crystallite size of less than 1 micrometer (typically, less than
500 nanometers, even less than 300, 200, or 150 nanometers; and in
some embodiments, less than 100, 75, 50, 25, or 20 nanometers), and
(b) is free of at least one of eutectic microstructure features
(i.e., is free of colonies and lamellar structure) or a
non-cellular microstructure. It is also within the scope of the
present disclosure for some embodiments to have at least one
crystalline phase within a specified average crystallite value and
at least one (different) crystalline phase outside of a specified
average crystallite value.
[0018] Some embodiments of the present disclosure include amorphous
material comprising Al.sub.2O.sub.3, REO, and at least one of
ZrO.sub.2 or HfO.sub.2, wherein at least 80 (85, 90, 95, 97, 98,
99, or even 100) percent by weight of the amorphous material
collectively comprises the Al.sub.2O.sub.3, REO, and at least one
of ZrO.sub.2 or HfO.sub.2, based on the total weight of the
amorphous material.
[0019] Some embodiments of the present disclosure include amorphous
material comprising Al.sub.2O.sub.3, REO, and at least one of
ZrO.sub.2 or HfO.sub.2, wherein at least 60 (65, 70, 75, 80, 85,
90, 95, 97, 98, 99, or even 100) percent by weight of the amorphous
material collectively comprises the Al.sub.2O.sub.3, REO, and at
least one of ZrO.sub.2 or HfO.sub.2, and less than 20 (preferably,
less than 15, 10, 5, or even 0) percent by weight SiO.sub.2 and
less than 20 (preferably, less than 15, 10, 5, or even 0) percent
by weight B.sub.2O.sub.3, based on the total weight of the
amorphous material.
[0020] Some embodiments of the present disclosure include amorphous
material comprising Al.sub.2O.sub.3, REO, and at least one of
ZrO.sub.2 or HfO.sub.2, wherein at least 60 (65, 70, 75, 80, 85,
90, 95, 97, 98, 99, or even 100) percent by weight of the amorphous
material collectively comprises the Al.sub.2O.sub.3, REO, and at
least one of ZrO.sub.2 or HfO.sub.2, and less than 40 (preferably,
less than 35, 30, 25, 20, 15, 10, 5, or even 0) percent by weight
collectively SiO.sub.2, B.sub.2O.sub.3, and P.sub.2O.sub.5, based
on the total weight of the amorphous material.
[0021] Some embodiments of the present disclosure include ceramic
comprising amorphous material (e.g., at least 5, 10, 15, 20, 25,
30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 97, 98, 99,
or even 100 percent by volume amorphous material), the amorphous
material comprising Al.sub.2O.sub.3, REO, and at least one of
ZrO.sub.2 or HfO.sub.2, wherein at least 80 (85, 90, 95, 97, 98,
99, or even 100) percent by weight of the amorphous material
collectively comprises the Al.sub.2O.sub.3, REO, and at least one
of ZrO.sub.2 or HfO.sub.2, based on the total weight of the
amorphous material.
[0022] Some embodiments of the present disclosure include ceramic
comprising amorphous material (e.g., at least 5, 10, 15, 20, 25,
30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 97, 98, 99,
or even 100 percent by volume glass), the amorphous material
comprising Al.sub.2O.sub.3, REO, and at least one of ZrO.sub.2 or
HfO.sub.2, wherein at least 60 (65, 70, 75, 80, 85, 90, 95, 97, 98,
99, or even 100) percent by weight of the amorphous material
collectively comprises the Al.sub.2O.sub.3, REO, and at least one
of ZrO.sub.2 or HfO.sub.2, and less than 20 preferably, less than
15, 10, 5, or even 0) percent by weight SiO.sub.2, and less than 20
(preferably, less than 15, 10, 5, or even 0) percent by weight
B.sub.2O.sub.3, based on the total weight of the amorphous
material. The ceramic may further comprise crystalline ceramic
(e.g., at least 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35,
30, 25, 20, 15, 10, 5, 3, 2, or 1 percent by volume crystalline
ceramic).
[0023] Some embodiments of the present disclosure include ceramic
comprising amorphous material (e.g., at least 5, 10, 15, 20, 25,
30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 97, 98, 99,
or even 100 percent by volume glass), the amorphous material
comprising Al.sub.2O.sub.3, REO, and at least one of ZrO.sub.2 or
HfO.sub.2, wherein at least 60 (65, 70, 75, 80, 85, 90, 95, 97, 98,
99, or even 100) percent by weight of the glass collectively
comprises the Al.sub.2O.sub.3, REO, and at least one of ZrO.sub.2
or HfO.sub.2, and less than 40 (preferably, less than 35, 30, 25,
20, 15, 10, 5, or even 0) percent by weight collectively SiO.sub.2,
B.sub.2O.sub.3, and P.sub.2O.sub.5, based on the total weight of
the amorphous material. The ceramic may further comprise
crystalline ceramic (e.g., at least 95, 90, 85, 80, 75, 70, 65, 60,
55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 3, 2, or 1 percent by
volume crystalline ceramic).
[0024] Some embodiments of the present disclosure include
glass-ceramic comprising Al.sub.2O.sub.3, REO, and at least one of
ZrO.sub.2 or HfO.sub.2, wherein at least 80 (85, 90, 95, 97, 98,
99, or even 100) percent by weight of the glass-ceramic
collectively comprises the Al.sub.2O.sub.3, REO, and at least one
of ZrO.sub.2 or HfO.sub.2, based on the total weight of the
glass-ceramic. The glass-ceramic may comprise, for example, at
least 1, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65,
70, 75, 80, 85, 90, or 95 percent by volume glass. The
glass-ceramic may comprise, for example, at least 99, 98, 97, 95,
90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10,
or 5 percent by volume crystalline ceramic.
[0025] Some embodiments of the present disclosure include
glass-ceramic comprising Al.sub.2O.sub.3, REO, and at least one of
ZrO.sub.2 or HfO.sub.2, wherein at least 60 (65, 70, 75, 80, 85,
90, 95, 97, 98, 99, or even 100) percent by weight of the
glass-ceramic collectively comprises the Al.sub.2O.sub.3, REO, and
at least one of ZrO.sub.2 or HfO.sub.2, and less than 20
(preferably, less than 15, 10, 5, or even 0) percent by weight
SiO.sub.2 and less than 20 (preferably, less than 15, 10, 5, or
even 0) percent by weight B.sub.2O.sub.3, based on the total weight
of the glass-ceramic. The glass-ceramic may comprise, for example,
at least 1, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60,
65, 70, 75, 80, 85, 90, or 95 percent by volume glass. The
glass-ceramic may comprise, for example, at least 99, 98, 97, 95,
90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10,
or 5 percent by volume crystalline ceramic.
[0026] Some embodiments of the present disclosure include
glass-ceramic comprising Al.sub.2O.sub.3, REO, and at least one of
ZrO.sub.2 or HfO.sub.2, wherein at least 60 (65, 70, 75, 80, 85,
90, 95, 97, 98, 99, or even 100) percent by weight of the
glass-ceramic collectively comprises the Al.sub.2O.sub.3, REO, and
at least one of ZrO.sub.2 or HfO.sub.2, and less than 40
(preferably, less than 35, 30, 25, 20, 15, 10, 5, or even 0)
percent by weight collectively SiO.sub.2, B.sub.2O.sub.3, and
P.sub.2O.sub.5, based on the total weight of the glass-ceramic. The
glass-ceramic may comprise, for example, at least 1, 2, 3, 5, 10,
15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95,
percent by volume amorphous material. The glass-ceramic may
comprise, for example, at least 99, 98, 97, 95, 90, 85, 80, 75, 70,
65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5 percent by
volume crystalline ceramic.
[0027] Some embodiments of the present disclosure include
glass-ceramic comprising Al.sub.2O.sub.3, REO, and at least one of
ZrO.sub.2 or HfO.sub.2, wherein the glass-ceramic (a) exhibits a
microstructure comprising crystallites (e.g., crystallites of a
complex metal oxide(s) (e.g., complex Al.sub.2O.sub.3.REO) and/or
ZrO.sub.2) having an average crystallite size of less than 1
micrometer (typically, less than 500 nanometers, or even less than
300, 200, or 150 nanometers; and in some embodiments, less than
100, 75, 50, 25, or 20 nanometers), and (b) is free of eutectic
microstructure features. Some embodiments of the present disclosure
include glass-ceramic comprising Al.sub.2O.sub.3, REO, and at least
one of ZrO.sub.2 or HfO.sub.2, wherein the glass-ceramic (a)
exhibits a non-cellular microstructure comprising crystallites
(e.g., crystallites of a complex metal oxide(s) (e.g., complex
Al.sub.2O.sub.3.REO) and/or ZrO.sub.2) having an average
crystallite size of less than 1 micrometer (typically, less than
500 nanometers, even less than 300, 200, or 150 nanometers; and in
some embodiments, less than 100, 75, 50, 25, or 20 nanometers). The
glass-ceramic may comprise, for example, at least 1, 2, 3, 5, 10,
15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95,
percent by volume amorphous material. The glass-ceramic may
comprise, for example, at least 99, 98, 97, 95, 90, 85, 80, 75, 70,
65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5 percent by
volume crystalline ceramic. It is also within the scope of the
present disclosure for some embodiments to have at least one
crystalline phase within a specified average crystallite value and
at least one (different) crystalline phase outside of a specified
average crystallite value.
[0028] Some embodiments of the present disclosure include ceramic
comprising crystalline ceramic (e.g., at least 1, 2, 3, 5, 10, 15,
20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 97,
98, 99, or even 100 percent by volume crystalline ceramic), the
crystalline ceramic comprising Al.sub.2O.sub.3, REO, and at least
one of ZrO.sub.2 or HfO.sub.2, wherein at least 80 (85, 90, 95, 97,
98, 99, or even 100) percent by weight of the crystalline ceramic
collectively comprises the Al.sub.2O.sub.3, REO, and at least one
of ZrO.sub.2 or HfO.sub.2, based on the total weight of the
crystalline ceramic. Some desirable embodiments include those
wherein the ceramic (a) exhibits a microstructure comprising
crystallites (e.g., crystallites of a complex metal oxide(s) (e.g.,
complex Al.sub.2O.sub.3.REO) and/or ZrO.sub.2) having an average
crystallite size of less than 1 micrometer (typically, less than
500 nanometers, or even less than 300, 200, or 150 nanometers; and
in some embodiments, less than 100, 75, 50, 25, or 20 nanometers),
and (b) is free of eutectic microstructure features. In another
aspect, some desirable embodiments include those wherein the
ceramic (a) exhibits a non-cellular microstructure comprising
crystallites (e.g., crystallites of a complex metal oxide(s) (e.g.,
complex Al.sub.2O.sub.3.REO) and/or ZrO.sub.2) having an average
crystallite size of less than 1 micrometer (typically, less than
500 nanometers, even less than 300, 200, or 150 nanometers; and in
some embodiments, less than 100, 75, 50, 25, or 20 nanometers). The
ceramic may comprise, for example, at least 99, 98, 97, 95, 90, 85,
80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 3,
2, or 1 percent by volume glass. It is also within the scope of the
present disclosure for some embodiments to have at least one
crystalline phase within a specified average crystallite value and
at least one (different) crystalline phase outside of a specified
average crystallite value.
[0029] Some embodiments of the present disclosure include ceramic
comprising crystalline ceramic (e.g., at least 1, 2, 3, 5, 10, 15,
20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 97,
98, 99, or even 100 percent by volume crystalline ceramic), the
crystalline ceramic comprising Al.sub.2O.sub.3, REO, and at least
one of ZrO.sub.2 or HfO.sub.2, wherein at least 60 (65, 70, 75, 80,
85, 90, 95, 97, 98, 99, or even 100) percent by weight of the
crystalline ceramic collectively comprises the Al.sub.2O.sub.3,
REO, and at least one of ZrO.sub.2 or HfO.sub.2, and less than 20
(preferably, less than 15, 10, 5, or even 0) percent by weight
SiO.sub.2 and less than 20 (preferably, less than 15, 10, 5, or
even 0) percent by weight B.sub.2O.sub.3, based on the total weight
of the crystalline ceramic. Some desirable embodiments include
those wherein the ceramic (a) exhibits a microstructure comprising
crystallites (e.g., crystallites of a complex metal oxide(s) (e.g.,
complex Al.sub.2O.sub.3.REO) and/or ZrO.sub.2) having an average
crystallite size of less than 1 micrometer (typically, less than
500 nanometers, or even less than 300, 200, or 150 nanometers; and
in some embodiments, less than 100, 75, 50, 25, or 20 nanometers),
and (b) is free of eutectic microstructure features. Some
embodiments of the present disclosure include those wherein the
ceramic (a) exhibits a non-cellular microstructure comprising
crystallites (e.g., crystallites of a complex metal oxide(s) (e.g.,
complex Al.sub.2O.sub.3.REO) and/or ZrO.sub.2) having an average
crystallite size of less than 1 micrometer (typically, less than
500 nanometers, even less than 300, 200, or 150 nanometers; and in
some embodiments, less than 100, 75, 50, 25, or 20 nanometers). The
ceramic may comprise, for example, at least 99, 98, 97, 95, 90, 85,
80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 3,
2, or 1 percent by volume amorphous material. It is also within the
scope of the present disclosure for some embodiments to have at
least one crystalline phase within a specified average crystallite
value and at least one (different) crystalline phase outside of a
specified average crystallite value.
[0030] Some embodiments of the present disclosure include ceramic
comprising crystalline ceramic (e.g., at least 1, 2, 3, 5, 10, 15,
20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 97,
98, 99, or even 100 percent by volume crystalline ceramic), the
crystalline ceramic comprising Al.sub.2O.sub.3, REO, and at least
one of ZrO.sub.2 or HfO.sub.2, wherein at least 60 (65, 70, 75, 80,
85, 90, 95, 97, 98, 99, or even 100) percent by weight of the
crystalline ceramic collectively comprises the Al.sub.2O.sub.3,
REO, and at least one of ZrO.sub.2 or HfO.sub.2, and less than 40
(preferably, less than 35, 30, 25, 20, 15, 10, 5, or even 0)
percent by weight collectively SiO.sub.2, B.sub.2O.sub.3, and
P.sub.2O.sub.5, based on the total weight of the crystalline
ceramic. Some desirable embodiments include those wherein the
ceramic (a) exhibits a microstructure comprising crystallites
(e.g., crystallites of a complex metal oxide(s) (e.g., complex
Al.sub.2O.sub.3.REO) and/or ZrO.sub.2) having an average
crystallite size of less than 1 micrometer (typically, less than
500 nanometers, or even less than less than 300, 200, or 150
nanometers; and in some embodiments, less than 100, 75, 50, 25, or
20 nanometers), and (b) is free of eutectic microstructure
features. Some embodiments of the present disclosure include those
wherein the ceramic (a) exhibits a non-cellular microstructure
comprising crystallites (e.g., crystallites of a complex metal
oxide(s) (e.g., complex Al.sub.2O.sub.3.REO) and/or ZrO.sub.2)
having an average crystallite size of less than 1 micrometer
(typically, less than 500 nanometers, even less than 300, 200, or
150 nanometers; and in some embodiments, less than 100, 75, 50, 25,
or 20 nanometers). The ceramic may comprise, for example, at least
99, 98, 97, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30,
25, 20, 15, 10, 5, 3, 2, or 1 percent by volume amorphous material.
It is also within the scope of the present disclosure for some
embodiments to have at least one crystalline phase within a
specified average crystallite value and at least one (different)
crystalline phase outside of a specified average crystallite
value.
[0031] Some embodiments of the present disclosure include ceramic
comprising crystalline ceramic (e.g., at least 1, 2, 3, 5, 10, 15,
20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 97,
98, 99, or even 100 percent by volume crystalline ceramic), the
ceramic comprising Al.sub.2O.sub.3, REO, and at least one of
ZrO.sub.2 or HfO.sub.2. Some desirable embodiments include those
wherein the ceramic (a) exhibits a microstructure comprising
crystallites (e.g., crystallites of a complex metal oxide(s) (e.g.,
complex Al.sub.2O.sub.3.REO) and/or ZrO.sub.2) having an average
crystallite size of less than 1 micrometer (typically, less than
500 nanometers, or even less than 300, 200, or 150 nanometers; and
in some embodiments, less than 100, 75, 50, 25, or 20 nanometers),
and (b) is free of eutectic microstructure features. Some
embodiments of the present disclosure include those wherein the
ceramic (a) exhibits a non-cellular microstructure comprising
crystallites (e.g., crystallites of a complex metal oxide(s) (e.g.,
complex Al.sub.2O.sub.3.REO) and/or ZrO.sub.2) having an average
crystallite size of less than 1 micrometer (typically, less than
500 nanometers, even less than 300, 200, or 150 nanometers; and in
some embodiments, less than 100, 75, 50, 25, or 20 nanometers). The
ceramic may comprise, for example, at least 99, 98, 97, 95, 90, 85,
80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 3,
2, or 1 percent by volume amorphous material. It is also within the
scope of the present disclosure for some embodiments to have at
least one crystalline phase within a specified average crystallite
value and at least one (different) crystalline phase outside of a
specified average crystallite value.
[0032] Some embodiments of the present disclosure include ceramic
comprising crystalline ceramic (e.g., at least 1, 2, 3, 5, 10, 15,
20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 97,
98, 99, or even 100 percent by volume crystalline ceramic), the
ceramic comprising Al.sub.2O.sub.3, REO, and at least one of
ZrO.sub.2 or HfO.sub.2, wherein at least 80 (85, 90, 95, 97, 98,
99, or even 100) percent by weight of the ceramic collectively
comprises m the Al.sub.2O.sub.3, REO, and at least one of ZrO.sub.2
or HfO.sub.2, based on the total weight of the ceramic. Some
desirable embodiments include those wherein the ceramic (a)
exhibits a microstructure comprising crystallites (e.g.,
crystallites of a complex metal oxide(s) (e.g., complex
Al.sub.2O.sub.3.REO) and/or ZrO.sub.2) having an average
crystallite size of less than 1 micrometer (typically, less than
500 nanometers, or even less than 300, 200, or 150 nanometers; and
in some embodiments, less than 100, 75, 50, 25, or 20 nanometers),
and (b) is free of eutectic microstructure features. Some
embodiments of the present disclosure include those wherein the
ceramic (a) exhibits a non-cellular microstructure comprising
crystallites (e.g., crystallites of a complex metal oxide(s) (e.g.,
complex Al.sub.2O.sub.3.REO) and/or ZrO.sub.2) having an average
crystallite size of less than 1 micrometer (typically, less than
500 nanometers, even less than 300, 200, or 150 nanometers; and in
some embodiments, less than 100, 75, 50, 25, or 20 nanometers). The
ceramic may comprise, for example, at least 99, 98, 97, 95, 90, 85,
80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 3,
2, or 1 percent by volume amorphous material. It is also within the
scope of the present disclosure for some embodiments to have at
least one crystalline phase within a specified average crystallite
value and at least one (different) crystalline phase outside of a
specified average crystallite value.
[0033] Some embodiments of the present disclosure include ceramic
comprising crystalline ceramic (e.g., at least 1, 2, 3, 5, 10, 15,
20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 97,
98, 99, or even 100 percent by volume crystalline ceramic), the
ceramic comprising Al.sub.2O.sub.3, REO, and at least one of
ZrO.sub.2 or HfO.sub.2, wherein at least 60 (65, 70, 75, 80, 85,
90, 95, 97, 98, 99, or even 100) percent by weight of the ceramic
collectively comprises the Al.sub.2O.sub.3, REO, and at least one
of ZrO.sub.2 or HfO.sub.2, and less than 20 (preferably, less than
15, 10, 5, or even 0) percent by weight SiO.sub.2 and less than 20
(preferably, less than 15, 10, 5, or even 0) percent by weight
B.sub.2O.sub.3, based on the total weight of the ceramic. Some
desirable embodiments include those wherein the ceramic (a)
exhibits a microstructure comprising crystallites (e.g.,
crystallites of a complex metal oxide(s) (e.g., complex
Al.sub.2O.sub.3.REO) and/or ZrO.sub.2) having an average
crystallite size of less than 1 micrometer (typically, less than
500 nanometers, or even less than 300, 200, or 150 nanometers; and
in some embodiments, less than 100, 75, 50, 25, or 20 nanometers),
and (b) is free of eutectic microstructure features. Some
embodiments of the present disclosure include those wherein the
ceramic (a) exhibits a non-cellular microstructure comprising
crystallites (e.g., crystallites of a complex metal oxide(s) (e.g.,
complex Al.sub.2O.sub.3.REO) and/or ZrO.sub.2) having an average
crystallite size of less than 1 micrometer (typically, less than
500 nanometers, even less than 300, 200, or 150 nanometers; and in
some embodiments, less than 100, 75, 50, 25, or 20 nanometers). The
ceramic may comprise, for example, at least 99, 98, 97, 95, 90, 85,
80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 3,
2, or 1 percent by volume glass. It is also within the scope of the
present disclosure for some embodiments to have at least one
crystalline phase within a specified average crystallite value and
at least one (different) crystalline phase outside of a specified
average crystallite value.
[0034] Some embodiments of the present disclosure include ceramic
comprising crystalline ceramic (e.g., at least 1, 2, 3, 5, 10, 15,
20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 97,
98, 99, or even 100 percent by volume crystalline ceramic), the
ceramic comprising Al.sub.2O.sub.3, REO, and at least one of
ZrO.sub.2 or HfO.sub.2, wherein at least 60 (65, 70, 75, 80, 85,
90, 95, 97, 98, 99, or even 100) percent by weight of the ceramic
collectively comprises the Al.sub.2O.sub.3, REO, and at least one
of ZrO.sub.2 or HfO.sub.2, and less than 40 (preferably, less than
35, 30, 25, 20, 15, 10, 5, or even 0) percent by weight
collectively SiO.sub.2, B.sub.2O.sub.3, and P.sub.2O.sub.5, based
on the total weight of the ceramic. Some desirable embodiments
include those wherein the ceramic (a) exhibits a microstructure
comprising crystallites (e.g., crystallites of a complex metal
oxide(s) (e.g., complex Al.sub.2O.sub.3.REO) and/or ZrO.sub.2)
having an average crystallite size of less than 1 micrometer
(typically, less than 500 nanometers, or even less than 300, 200,
or 150 nanometers; and in some embodiments, less than 100, 75, 50,
25, or 20 nanometers), and (b) is free of eutectic microstructure
features. Some embodiments of the present disclosure include those
wherein the ceramic (a) exhibits a non-cellular microstructure
comprising crystallites (e.g., crystallites of a complex metal
oxide(s) (e.g., complex Al.sub.2O.sub.3.REO) and/or ZrO.sub.2)
having an average crystallite size of less than 1 micrometer
(typically, less than 500 nanometers, even less than 300, 200, or
150 nanometers; and in some embodiments, less than 100, 75, 50, 25,
or 20 nanometers). The ceramic may comprise, for example, at least
99, 98, 97, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30,
25, 20, 15, 10, 5, 3, 2, or 1 percent by volume amorphous material.
It is also within the scope of the present disclosure for some
embodiments to have at least one crystalline phase within a
specified average crystallite value and at least one (different)
crystalline phase outside of a specified average crystallite
value.
[0035] Some embodiments of the present disclosure include
glass-ceramic comprising Al.sub.2O.sub.3, REO, and at least one of
ZrO.sub.2 or HfO.sub.2, wherein the glass-ceramic (a) exhibits a
microstructure comprising crystallites (e.g., crystallites of a
complex metal oxide(s) (e.g., complex Al.sub.2O.sub.3.REO) and/or
ZrO.sub.2) having an average crystallite size of less than 200
nanometers (150 nanometers, 100 nanometers, 75 nanometers, or even
50 nanometers) and (b) has a density of at least 90% (95%, 96%,
97%, 98%, 99%, 99.5%, or 100%) of theoretical density. Some
embodiments can be free of at least one of eutectic microstructure
features or a non-cellular microstructure. It is also within the
scope of the present disclosure for some embodiments to have at
least one crystalline phase within a specified average crystallite
value and at least one (different) crystalline phase outside of a
specified average crystallite value.
[0036] Some embodiments of the present disclosure include
glass-ceramic comprising Al.sub.2O.sub.3, REO, and at least one of
ZrO.sub.2 or HfO.sub.2, wherein the glass-ceramic (a) exhibits a
microstructure comprising crystallites (e.g., crystallites of a
complex metal oxide(s) (e.g., complex Al.sub.2O.sub.3.REO) and/or
ZrO.sub.2), wherein none of the crystallites are greater than 200
nanometers (150 nanometers, 100 nanometers, 75 nanometers, or even
50 nanometers) in size and (b) has a density of at least 90% (95%,
96%, 97%, 98%, 99%, 99.5%, or 100%) of theoretical density. Some
embodiments can be free of at least one of eutectic microstructure
features or a non-cellular microstructure. It is also within the
scope of the present disclosure for some embodiments to have at
least one crystalline phase within a specified crystallite size
value and at least one (different) crystalline phase outside of a
specified crystallite size value.
[0037] Some embodiments of the present disclosure include
glass-ceramic comprising Al.sub.2O.sub.3, REO, and at least one of
ZrO.sub.2 or HfO.sub.2, wherein the glass-ceramic (a) exhibits a
microstructure comprising crystallites (e.g., crystallites of a
complex metal oxide(s) (e.g., complex Al.sub.2O.sub.3.REO) and/or
ZrO.sub.2), wherein at least a portion of the crystallites are not
greater than 150 nanometers (100 nanometers, 75 nanometers, or even
50 nanometers) in size and (b) has a density of at least 90% (95%,
96%, 97%, 98%, 99%, 99.5%, or 100%) of theoretical density. Some
embodiments can be free of at least one of eutectic microstructure
features or a non-cellular microstructure. It is also within the
scope of the present disclosure for some embodiments to have at
least one crystalline phase within a specified crystallite value
and at least one (different) crystalline phase outside of a
specified crystallite value.
[0038] Some embodiments of the present disclosure include fully
crystallized glass-ceramic comprising Al.sub.2O.sub.3, REO, and at
least one of ZrO.sub.2 or HfO.sub.2, wherein the glass-ceramic (a)
exhibits a microstructure comprising crystallites (e.g.,
crystallites of a complex metal oxide(s) (e.g., complex
Al.sub.2O.sub.3.REO) and/or ZrO.sub.2) having an average
crystallite size not greater than 1 micrometer (500 nanometers, 300
nanometers, 200 nanometers, 150 nanometers, 100 nanometers, 75
nanometers, or even 50 nanometers) in size and (b) has a density of
at least 90% (95%, 96%, 97%, 98%, 99%, 99.5%, or 100%) of
theoretical density. Some embodiments can be free of at least one
of eutectic microstructure features or a non-cellular
microstructure. It is also within the scope of the present
disclosure for some embodiments to have at least one crystalline
phase within a specified crystallite value and at least one
(different) crystalline phase outside of a specified crystallite
value.
[0039] For ceramics according to the present disclosure comprising
crystalline ceramic, some embodiments include those comprising
Al.sub.2O.sub.3, REO, and at least one of ZrO.sub.2 or HfO.sub.2,
wherein the ceramic (a) exhibits a microstructure comprising
crystallites (e.g., crystallites of a complex metal oxide(s) (e.g.,
complex Al.sub.2O.sub.3.REO) and/or ZrO.sub.2) having an average
crystallite size of less than 200 nanometers (150 nanometers, 100
nanometers, 75 nanometers, or even 50 nanometers) and (b) has a
density of at least 90% (95%, 96%, 97%, 98%, 99%, 99.5%, or 100%)
of theoretical density. Some embodiments can be free of at least
one of eutectic microstructure features or a non-cellular
microstructure. It is also within the scope of the present
disclosure for some embodiments to have at least one crystalline
phase within a specified average crystallite value and at least one
(different) crystalline phase outside of a specified average
crystallite value.
[0040] For ceramics according to the present disclosure comprising
crystalline ceramic, some embodiments include those comprising
Al.sub.2O.sub.3, REO, and at least one of ZrO.sub.2 or HfO.sub.2,
wherein the ceramic (a) exhibits a microstructure comprising
crystallites (e.g., crystallites of a complex metal oxide(s) (e.g.,
complex Al.sub.2O.sub.3.REO) and/or ZrO.sub.2), wherein none of the
crystallites are greater than 200 nanometers (150 nanometers, 100
nanometers, 75 nanometers, or even 50 nanometers) in size and (b)
has a density of at least 90% (95%, 96%, 97%, 98%, 99%, 99.5%, or
100%) of theoretical density. Some embodiments can be free of at
least one of eutectic microstructure features or a non-cellular
microstructure. It is also within the scope of the present
disclosure for some embodiments to have at least one crystalline
phase within a specified crystallite value and at least one
(different) crystalline phase outside of a specified crystallite
value.
[0041] For ceramics according to the present disclosure comprising
crystalline ceramic, some embodiments include those comprising
Al.sub.2O.sub.3, REO, and at least one of ZrO.sub.2 or HfO.sub.2,
wherein the ceramic (a) exhibits a microstructure comprising
crystallites (e.g., crystallites of a complex metal oxide(s) (e.g.,
complex Al.sub.2O.sub.3.REO) and/or ZrO.sub.2), wherein at least a
portion of the crystallites are not greater than 150 nanometers
(100 nanometers, 75 nanometers, or even 50 nanometers) in size and
(b) has a density of at least 90% (95%, 96%, 97%, 98%, 99%, 99.5%,
or 100%) of theoretical density. Some embodiments can be free of at
least one of eutectic microstructure features or a non-cellular
microstructure. It is also within the scope of the present
disclosure for some embodiments to have at least one crystalline
phase within a specified crystallite value and at least one
(different) crystalline phase outside of a specified crystallite
value.
[0042] For ceramics according to the present disclosure comprising
crystalline ceramic, some embodiments include those comprising
Al.sub.2O.sub.3, REO, and at least one of ZrO.sub.2 or HfO.sub.2,
wherein the ceramic (a) exhibits a microstructure comprising
crystallites (e.g., crystallites of a complex metal oxide(s) (e.g.,
complex Al.sub.2O.sub.3.REO) and/or ZrO.sub.2) having an average
crystallite size not greater than 1 micrometer (500 nanometers, 300
nanometers, 200 nanometers, 150 nanometers, 100 nanometers, 75
nanometers, or even 50 nanometers) in size and (b) has a density of
at least 90% (95%, 96%, 97%, 98%, 99%, 99.5%, or 100%) of
theoretical density. Some embodiments can be free of at least one
of eutectic microstructure features or a non-cellular
microstructure. It is also within the scope of the present
disclosure for some embodiments to have at least one crystalline
phase within a specified crystallite value and at least one
(different) crystalline phase outside of a specified crystallite
value.
[0043] Some embodiments of the present disclosure include a
glass-ceramic comprising alpha Al.sub.2O.sub.3, crystalline
ZrO.sub.2, and a first complex Al.sub.2O.sub.3.REO, wherein at
least one of the alpha Al.sub.2O.sub.3, the crystalline ZrO.sub.2,
or the first complex Al.sub.2O.sub.3.REO has an average crystal
size not greater than 150 nanometers, and wherein the abrasive
particles have a density of at least 90 (in some embodiments at
least 95, 96, 97, 98, 99, 99.5, or even 100) percent of theoretical
density. In some embodiments, preferably at least 75 (80, 85, 90,
95, 97, or even at least 99) percent of the crystal sizes by number
are not greater than 200 nanometers. In some embodiments
preferably, the glass-ceramic further comprises a second, different
complex Al.sub.2O.sub.3.REO. In some embodiments preferably, the
glass-ceramic further comprises a complex
Al.sub.2O.sub.3.Y.sub.2O.sub.3.
[0044] Some embodiments of the present disclosure include a
glass-ceramic comprising a first complex Al.sub.2O.sub.3.REO, a
second, different complex Al.sub.2O.sub.3.REO, and crystalline
ZrO.sub.2, wherein for at least one of the first complex
Al.sub.2O.sub.3.REO, the second complex Al.sub.2O.sub.3.REO, or the
crystalline ZrO.sub.2, at least 90 (in some embodiments preferably,
95, or even 100) percent by number of the crystal sizes thereof are
not greater than 200 nanometers, and wherein the abrasive particles
have a density of at least 90 (in some embodiments at least 95, 96,
97, 98, 99, 99.5, or even 100) percent of theoretical density. In
some embodiments preferably, the glass-ceramic further comprises a
complex Al.sub.2O.sub.3.Y.sub.2O.sub.3.
[0045] Some embodiments of the present disclosure a glass-ceramic
comprising a first complex Al.sub.2O.sub.3.REO, a second, different
complex Al.sub.2O.sub.3.REO, and crystalline ZrO.sub.2, wherein at
least one of the first complex Al.sub.2O.sub.3.REO, the second,
different complex Al.sub.2O.sub.3.REO, or the crystalline ZrO.sub.2
has an average crystal size not greater than 150 nanometers, and
wherein the abrasive particles have a density of at least 90 (in
some embodiments at least 95, 96, 97, 98, 99, 99.5, or even 100)
percent of theoretical density. In some embodiments, preferably at
least 75 (80, 85, 90, 95, 97, or even at least 99) percent by
number of the crystal sizes are not greater than 200 nanometers. In
some embodiments preferably, the glass-ceramic further comprises a
second, different complex Al.sub.2O.sub.3.REO. In some embodiments
preferably, the glass-ceramic further comprises a complex
Al.sub.2O.sub.3.Y.sub.2O.sub.3.
[0046] Some embodiments of the present disclosure include abrasive
particles comprising a glass-ceramic, the glass-ceramic comprising
a first complex Al.sub.2O.sub.3.REO, a second, different complex
Al.sub.2O.sub.3.REO, and crystalline ZrO.sub.2, wherein for at
least one of the first complex Al.sub.2O.sub.3.REO, the second,
different complex Al.sub.2O.sub.3.REO, or the crystalline
ZrO.sub.2, at least 90 (in some embodiments preferably, 95, or even
100) percent by number of the crystal sizes thereof are not greater
than 200 nanometers, and wherein the abrasive particles have a
density of at least 90 (in some embodiments at least 95, 96, 97,
98, 99, 99.5, or even 100) percent of theoretical density. In some
embodiments preferably, the glass-ceramic further comprises a
complex Al.sub.2O.sub.3.Y.sub.2O.sub.3.
[0047] In another aspect, the present disclosure provides methods
for making ceramics according to the present disclosure. For
example, the present disclosure provides a method for making
ceramic according to the present disclosure comprising amorphous
material (e.g., glass, or glass and crystalline ceramic including
glass-ceramic), the method comprising: [0048] melting sources of at
least Al.sub.2O.sub.3, REO, and at least one of ZrO.sub.2 or
HfO.sub.2 to provide a melt; and [0049] cooling the melt to provide
ceramic comprising amorphous material. It is also within the scope
of the present disclosure to heat-treat certain amorphous materials
or ceramics comprising amorphous material described herein to a
ceramic comprising crystalline ceramic (including glass-ceramic)
(i.e., such that at least a portion of the amorphous material is
converted to a glass-ceramic).
[0050] In this application:
[0051] "amorphous material" refers to material derived from a melt
and/or a vapor phase that lacks any long range crystal structure as
determined by X-ray diffraction and/or has an exothermic peak
corresponding to the crystallization of the amorphous material as
determined by a DTA (differential thermal analysis) as determined
by the test described herein entitled "Differential Thermal
Analysis";
[0052] "ceramic" includes amorphous material, glass, crystalline
ceramic, glass-ceramic, and combinations thereof;
[0053] "complex metal oxide" refers to a metal oxide comprising two
or more different metal elements and oxygen (e.g.,
CeAl.sub.11O.sub.18, Dy.sub.3Al.sub.5O.sub.12, MgAl.sub.2O.sub.4,
and Y.sub.3Al.sub.5O.sub.12);
[0054] "complex Al.sub.2O.sub.3.metal oxide" refers to a complex
metal oxide comprising, on a theoretical oxide basis,
Al.sub.2O.sub.3 and one or more metal elements other than Al (e.g.,
CeAl.sub.11O.sub.18, Dy.sub.3Al.sub.5O.sub.12, MgAl.sub.2O.sub.4,
and Y.sub.3Al.sub.5O.sub.12);
[0055] "complex Al.sub.2O.sub.3.Y.sub.2O.sub.3" refers to a complex
metal oxide comprising, on a theoretical oxide basis,
Al.sub.2O.sub.3 and Y.sub.2O.sub.3 (e.g.,
Y.sub.3Al.sub.5O.sub.12);
[0056] "complex Al.sub.2O.sub.3.REO" refers to a complex metal
oxide comprising, on a theoretical oxide basis, Al.sub.2O.sub.3 and
rare earth oxide (e.g., CeAl.sub.11O.sub.18 and
Dy.sub.3Al.sub.5O.sub.12);
[0057] "glass" refers to amorphous material exhibiting a glass
transition temperature;
[0058] "glass-ceramic" refers to ceramic comprising crystals formed
by heat-treating amorphous material;
[0059] "T.sub.g" refers to the glass transition temperature as
determined by the test described herein entitled "Differential
Thermal Analysis";
[0060] "T.sub.x" refers to the crystallization temperature as
determined by the test described herein entitled "Differential
Thermal Analysis";
[0061] "rare earth oxides" refers to cerium oxide (e.g.,
CeO.sub.2), dysprosium oxide (e.g., Dy.sub.2O.sub.3), erbium oxide
(e.g., Er.sub.2O.sub.3), europium oxide (e.g., Eu.sub.2O.sub.3),
gadolinium (e.g., Gd.sub.2O.sub.3), holmium oxide (e.g.,
Ho.sub.2O.sub.3), lanthanum oxide (e.g., La.sub.2O.sub.3), lutetium
oxide (e.g., Lu.sub.2O.sub.3), neodymium oxide (e.g.,
Nd.sub.2O.sub.3), praseodymium oxide (e.g., Pr.sub.6O.sub.11),
samarium oxide (e.g., Sm.sub.2O.sub.3), terbium (e.g.,
Tb.sub.2O.sub.3), thorium oxide (e.g., Th.sub.4O.sub.7), thulium
(e.g., Tm.sub.2O.sub.3), and ytterbium oxide (e.g.,
Yb.sub.2O.sub.3), and combinations thereof;
[0062] "REO" refers to rare earth oxide(s).
[0063] Further, it is understood herein that unless it is stated
that a metal oxide (e.g., Al.sub.2O.sub.3, complex
Al.sub.2O.sub.3.metal oxide, etc.) is crystalline, for example, in
a glass-ceramic, it may be amorphous, crystalline, or portions
amorphous and portions crystalline. For example if a glass-ceramic
comprises Al.sub.2O.sub.3 and ZrO.sub.2, the Al.sub.2O.sub.3 and
ZrO.sub.2 may each be in an amorphous state, crystalline state, or
portions in an amorphous state and portions in a crystalline state,
or even as a reaction product with another metal oxide(s) (e.g.,
unless it is stated that, for example, Al.sub.2O.sub.3 is present
as crystalline Al.sub.2O.sub.3 or a specific crystalline phase of
Al.sub.2O.sub.3 (e.g., alpha Al.sub.2O.sub.3), it may be present as
crystalline Al.sub.2O.sub.3 and/or as part of one or more
crystalline complex Al.sub.2O.sub.3.metal oxides.
[0064] Further, it is understood that glass-ceramics formed by
heating amorphous material not exhibiting a T.sub.g may not
actually comprise glass, but rather may comprise the crystals and
amorphous material that does not exhibiting a T.sub.g.
[0065] Ceramics articles according to the present disclosure can be
made, formed as, or converted into glass beads (e.g., beads having
diameters of at least 1 micrometers, 5 micrometers, 10 micrometers,
25 micrometers, 50 micrometers, 100 micrometers, 150 micrometers,
250 micrometers, 500 micrometers, 750 micrometers, 1 mm, 5 mm, or
even at least 10 mm), articles (e.g., plates), fibers, particles,
and coatings (e.g., thin coatings). The glass beads can be useful,
for example, in reflective devices such as retroreflective
sheeting, alphanumeric plates, and pavement markings. The particles
and fibers are useful, for example, as thermal insulation, filler,
or reinforcing material in composites (e.g., ceramic, metal, or
polymeric matrix composites). The thin coatings can be useful, for
example, as protective coatings in applications involving wear, as
well as for thermal management. Examples of articles according of
the present disclosure include kitchenware (e.g., plates), dental
brackets, and reinforcing fibers, cutting tool inserts, abrasive
materials, and structural components of gas engines, (e.g., valves
and bearings). Other articles include those having a protective
coating of ceramic on the outer surface of a body or other
substrate. Certain ceramic particles according to the present
disclosure can be particularly useful as abrasive particles. The
abrasive particles can be incorporated into an abrasive article, or
used in loose form.
[0066] Abrasive articles according to the present disclosure
comprise binder and a plurality of abrasive particles, wherein at
least a portion of the abrasive particles are the abrasive
particles according to the present disclosure. Exemplary abrasive
products include coated abrasive articles, bonded abrasive articles
(e.g., wheels), non-woven abrasive articles, and abrasive brushes.
Coated abrasive articles typically comprise a backing having first
and second, opposed major surfaces, and wherein the binder and the
plurality of abrasive particles form an abrasive layer on at least
a portion of the first major surface.
[0067] In some embodiments, preferably, at least 5, 10, 15, 20, 25,
30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or even 100
percent by weight of the abrasive particles in an abrasive article
are the abrasive particles according to the present disclosure,
based on the total weight of the abrasive particles in the abrasive
article.
[0068] Abrasive particles are usually graded to a given particle
size distribution before use. Such distributions typically have a
range of particle sizes, from coarse particles fine particles. In
the abrasive art this range is sometimes referred to as a "coarse",
"control" and "fine" fractions. Abrasive particles graded according
to industry accepted grading standards specify the particle size
distribution for each nominal grade within numerical limits. Such
industry accepted grading standards (i.e., specified nominal
grades) include those known as the American National Standards
Institute, Inc. (ANSI) standards, Federation of European Producers
of Abrasive Products (FEPA) standards, and Japanese Industrial
Standard (JIS) standards. In one aspect, the present disclosure
provides a plurality of abrasive particles having a specified
nominal grade, wherein at least a portion of the plurality of
abrasive particles are abrasive particles according to the present
disclosure. In some embodiments, preferably, at least 5, 10, 15,
20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or
even 100 percent by weight of the plurality of abrasive particles
are the abrasive particles according to the present disclosure,
based on the total weight of the plurality of abrasive
particles.
[0069] The present disclosure also provides a method of abrading a
surface, the method comprising: [0070] contacting abrasive
particles according to the present disclosure with a surface of a
workpiece; and [0071] moving at least one of the abrasive particles
according to the present disclosure or the contacted surface to
abrade at least a portion of the surface with at least one of the
abrasive particles according to the present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0072] FIG. 1 is an X-Ray diffraction pattern of Example 1
material;
[0073] FIG. 2 is an SEM micrograph of a polished cross-section of
Comparative Example A material;
[0074] FIG. 3 is an optical photomicrograph of Example 2
material;
[0075] FIG. 4 is an optical photomicrograph of a section of Example
6 hot-pressed material;
[0076] FIG. 5 is an SEM photomicrograph of a polished cross-section
of heat-treated Example 6 material;
[0077] FIG. 6 is a DTA curve of Example 6 material;
[0078] FIG. 7 is an SEM photomicrograph of a polished cross-section
of Example 43 material;
[0079] FIG. 8 is an SEM photomicrograph of a polished cross-section
of Example 47 material;
[0080] FIG. 9 is a fragmentary cross-sectional schematic view of a
coated abrasive article including abrasive particles according to
the present disclosure;
[0081] FIG. 10 is a perspective view of a bonded abrasive article
including abrasive particles according to the present disclosure;
and
[0082] FIG. 11 is an enlarged schematic view of a nonwoven abrasive
article including abrasive particles according to the present
disclosure.
DETAILED DESCRIPTION
[0083] In general, materials according to the present disclosure
can be made by heating (including in a flame) the appropriate metal
oxide sources to form a melt, desirably a homogenous melt, and then
rapidly cooling the melt to provide amorphous materials or ceramic
comprising amorphous materials. Amorphous materials and ceramics
comprising amorphous materials according to the present disclosure
can be made, for example, by heating (including in a flame) the
appropriate metal oxide sources to form a melt, desirably a
homogenous melt, and then rapidly cooling the melt to provide
amorphous material. Some embodiments of amorphous materials can be
made, for example, by melting the metal oxide sources in any
suitable furnace (e.g., an inductive heated furnace, a gas-fired
furnace, or an electrical furnace), or, for example, in a plasma.
The resulting melt is cooled (e.g., discharging the melt into a
cooling media (e.g., high velocity air jets, liquids, metal plates
(including chilled metal plates), metal rolls (including chilled
metal rolls), metal balls (including chilled metal balls), and the
like)).
[0084] In one method, amorphous materials and ceramic comprising
amorphous materials according to the present disclosure can be made
utilizing flame fusion as disclosed, for example, in U.S. Pat. No.
6,254,981 (Castle), the disclosure of which is incorporated herein
by reference. In this method, the metal oxide sources materials are
fed (e.g., in the form of particles, sometimes referred to as "feed
particles") directly into a burner (e.g., a methane-air burner, an
acetylene-oxygen burner, a hydrogen-oxygen burner, and like), and
then quenched, for example, in water, cooling oil, air, or the
like. Feed particles can be formed, for example, by grinding,
agglomerating (e.g., spray-drying), melting, or sintering the metal
oxide sources. The size of feed particles fed into the flame
generally determine the size of the resulting amorphous material
comprising particles.
[0085] Some embodiments of amorphous materials can also be obtained
by other techniques, such as: laser spin melt with free fall
cooling, Taylor wire technique, plasmatron technique, hammer and
anvil technique, centrifugal quenching, air gun splat cooling,
single roller and twin roller quenching, roller-plate quenching and
pendant drop melt extraction (see, e.g., Rapid Solidification of
Ceramics, Brockway et. al., Metals And Ceramics Information Center,
A Department of Defense Information Analysis Center, Columbus,
Ohio, January, 1984, the disclosure of which is incorporated here
as a reference). Some embodiments of amorphous materials may also
be obtained by other techniques, such as: thermal (including flame
or laser or plasma-assisted) pyrolysis of suitable precursors,
physical vapor synthesis (PVS) of metal precursors and
mechanochemical processing.
[0086] Useful Al.sub.2O.sub.3-REO-ZrO.sub.2/HfO.sub.2 formulations
include those at or near a eutectic composition(s) (e.g., ternary
eutectic compositions). In addition to
Al.sub.2O.sub.3-REO-ZrO.sub.2/HfO.sub.2 compositions disclosed
herein, other such compositions, including quaternary and other
higher order eutectic compositions, may be apparent to those
skilled in the art after reviewing the present disclosure.
[0087] Sources, including commercial sources, of (on a theoretical
oxide basis) Al.sub.2O.sub.3 include bauxite (including both
natural occurring bauxite and synthetically produced bauxite),
calcined bauxite, hydrated aluminas (e.g., boehmite, and gibbsite),
aluminum, Bayer process alumina, aluminum ore, gamma alumina, alpha
alumina, aluminum salts, aluminum nitrates, and combinations
thereof. The Al.sub.2O.sub.3 source may contain, or only provide,
Al.sub.2O.sub.3. Alternatively, the Al.sub.2O.sub.3 source may
contain, or provide Al.sub.2O.sub.3, as well as one or more metal
oxides other than Al.sub.2O.sub.3 (including materials of or
containing complex Al.sub.2O.sub.3.metal oxides (e.g.,
Dy.sub.3Al.sub.5O.sub.12, Y.sub.3Al.sub.5O.sub.12,
CeAl.sub.11O.sub.18, etc.)).
[0088] Sources, including commercial sources, of rare earth oxides
include rare earth oxide powders, rare earth metals, rare
earth-containing ores (e.g., bastnasite and monazite), rare earth
salts, rare earth nitrates, and rare earth carbonates. The rare
earth oxide(s) source may contain, or only provide, rare earth
oxide(s). Alternatively, the rare earth oxide(s) source may
contain, or provide rare earth oxide(s), as well as one or more
metal oxides other than rare earth oxide(s) (including materials of
or containing complex rare earth oxide.other metal oxides (e.g.,
Dy.sub.3Al.sub.5O.sub.12, CeAl.sub.11O.sub.18, etc.)).
[0089] Sources, including commercial sources, of (on a theoretical
oxide basis) ZrO.sub.2 include zirconium oxide powders, zircon
sand, zirconium, zirconium-containing ores, and zirconium salts
(e.g., zirconium carbonates, acetates, nitrates, chlorides,
hydroxides, and combinations thereof). In addition, or
alternatively, the ZrO.sub.2 source may contain, or provide
ZrO.sub.2, as well as other metal oxides such as hafnia. Sources,
including commercial sources, of (on a theoretical oxide basis)
HfO.sub.2 include hafnium oxide powders, hafnium,
hafnium-containing ores, and hafnium salts. In addition, or
alternatively, the HfO.sub.2 source may contain, or provide
HfO.sub.2, as well as other metal oxides such as ZrO.sub.2.
[0090] Optionally, ceramics according to the present disclosure
further comprise other oxide metal oxides (i.e., metal oxides other
than Al.sub.2O.sub.3, rare earth oxide(s), and
ZrO.sub.2/HfO.sub.2). Other useful metal oxide may also include, on
a theoretical oxide basis, BaO, CaO, Cr.sub.2O.sub.3, CoO,
Fe.sub.2O.sub.3, GeO.sub.2, Li.sub.2O, MgO, MnO, NiO, Na.sub.2O,
Sc.sub.2O.sub.3, SrO, TiO.sub.2, ZnO, and combinations thereof.
Sources, including commercial sources, include the oxides
themselves, complex oxides, ores, carbonates, acetates, nitrates,
chlorides, hydroxides, etc. These metal oxides are added to modify
a physical property of the resulting ceramic and/or improve
processing. These metal oxides are typically are added anywhere
from 0 to 50% by weight, in some embodiments preferably 0 to 25% by
weight and more preferably 0 to 50% by weight of the ceramic
material depending, for example, upon the desired property.
[0091] In some embodiments, it may be advantageous for at least a
portion of a metal oxide source (in some embodiments, preferably,
10, 15, 20, 25, 30, 35, 40, 45, or even 50, percent by weight) to
be obtained by adding particulate, metallic material comprising at
least one of a metal (e.g., Al, Ca, Cu, Cr, Fe, Li, Mg, Ni, Ag, Ti,
Zr, and combinations thereof), M, that has a negative enthalpy of
oxide formation or an alloy thereof to the melt, or otherwise metal
them with the other raw materials. Although not wanting to be bound
by theory, it is believed that the heat resulting from the
exothermic reaction associated with the oxidation of the metal is
beneficial in the formation of a homogeneous melt and resulting
amorphous material. For example, it is believed that the additional
heat generated by the oxidation reaction within the raw material
eliminates or minimizes insufficient heat transfer, and hence
facilitates formation and homogeneity of the melt, particularly
when forming amorphous particles with x, y, and z dimensions over
150 micrometers. It is also believed that the availability of the
additional heat aids in driving various chemical reactions and
physical processes (e.g., densification, and spherodization) to
completion. Further, it is believed for some embodiments, the
presence of the additional heat generated by the oxidation reaction
actually enables the formation of a melt, which otherwise is
difficult or otherwise not practical due to high melting point of
the materials. Further, the presence of the additional heat
generated by the oxidation reaction actually enables the formation
of amorphous material that otherwise could not be made, or could
not be made in the desired size range. Another advantage of the
disclosure include, in forming the amorphous materials, that many
of the chemical and physical processes such as melting,
densification and spherodizing can be achieved in a short time, so
that very high quench rates be can achieved. For additional
details, see copending application having U.S. Ser. No. 10/211,639,
filed the same date as the instant application, the disclosure of
which is incorporated herein by reference.
[0092] The addition of certain metal oxides may alter the
properties and/or crystalline structure or microstructure of
ceramics according to the present disclosure, as well as the
processing of the raw materials and intermediates in making the
ceramic. For example, oxide additions such as MgO, CaO, Li.sub.2O,
and Na.sub.2O have been observed to alter both the T.sub.g and
T.sub.x (wherein T.sub.x is the crystallization temperature) of
glass. Although not wishing to be bound by theory, it is believed
that such additions influence glass formation. Further, for
example, such oxide additions may decrease the melting temperature
of the overall system (i.e., drive the system toward lower melting
eutectic), and ease of glass-formation. Complex eutectics in multi
component systems (quaternary, etc.) may result in better
glass-forming ability. The viscosity of the liquid melt and
viscosity of the glass in its "working" range may also be affected
by the addition of metal oxides other than Al.sub.2O.sub.3, rare
earth oxide(s), and ZrO.sub.2/HfO.sub.2 (such as MgO, CaO,
Li.sub.2O, and Na.sub.2O).
[0093] Typically, amorphous materials and the glass-ceramics
according to the present disclosure have x, y, and z dimensions
each perpendicular to each other, and wherein each of the x, y, and
z dimensions is at least 10 micrometers. In some embodiments, the
x, y, and z dimensions is at least 30 micrometers, 35 micrometers,
40 micrometers, 45 micrometers, 50 micrometers, 75 micrometers, 100
micrometers, 150 micrometers, 200 micrometers, 250 micrometers, 500
micrometers, 1000 micrometers, 2000 micrometers, 2500 micrometers,
1 mm, 5 mm, or even at least 10 mm. The x, y, and z dimensions of a
material are determined either visually or using microscopy,
depending on the magnitude of the dimensions. The reported z
dimension is, for example, the diameter of a sphere, the thickness
of a coating, or the longest length of a prismatic shape.
[0094] Crystallization of amorphous material and ceramic comprising
the amorphous material to form glass-ceramics may also be affected
by the additions of materials. For example, certain metals, metal
oxides (e.g., titanates and zirconates), and fluorides, for
example, may act as nucleation agents resulting in beneficial
heterogeneous nucleation of crystals. Also, addition of some oxides
may change nature of metastable phases devitrifying from the glass
upon reheating. In another aspect, for ceramics according to the
present disclosure comprising crystalline ZrO.sub.2, it may be
desirable to add metal oxides (e.g., Y.sub.2O.sub.3, TiO.sub.2,
CaO, and MgO) that are known to stabilize tetragonal/cubic form of
ZrO.sub.2.
[0095] The particular selection of metal oxide sources and other
additives for making ceramics according to the present disclosure
typically takes into account, for example, the desired composition
and microstructure of the resulting crystalline containing
ceramics, the desired degree of crystallinity, if any, the desired
physical properties (e.g., hardness or toughness) of the resulting
ceramics, avoiding or minimizing the presence of undesirable
impurities, the desired characteristics of the resulting ceramics,
and/or the particular process (including equipment and any
purification of the raw materials before and/or during fusion
and/or solidification) being used to prepare the ceramics.
[0096] In some instances, it may be preferred to incorporate
limited amounts of metal oxides selected from the group consisting
of: Na.sub.2O, P.sub.2O.sub.5, SiO.sub.2, TeO.sub.2,
V.sub.2O.sub.3, and combinations thereof. Sources, including
commercial sources, include the oxides themselves, complex oxides,
ores, carbonates, acetates, nitrates, chlorides, hydroxides, etc.
These metal oxides may be added, for example, to modify a physical
property of the resulting abrasive particles and/or improve
processing. These metal oxides when used are typically are added
from greater than 0 to 20% by weight, preferably greater than 0 to
5% by weight and more preferably greater than 0 to 2% by weight of
the glass-ceramic depending, for example, upon the desired
property.
[0097] The metal oxide sources and other additives can be in any
form suitable to the process and equipment being used to make
ceramics according to the present disclosure. The raw materials can
be melted and quenched using techniques and equipment known in the
art for making oxide glasses and amorphous metals. Desirable
cooling rates include those of 50K/s and greater. Cooling
techniques known in the art include roll-chilling. Roll-chilling
can be carried out, for example, by melting the metal oxide sources
at a temperature typically 20-200.degree. C. higher than the
melting point, and cooling/quenching the melt by spraying it under
high pressure (e.g., using a gas such as air, argon, nitrogen or
the like) onto a high-speed rotary roll(s). Typically, the rolls
are made of metal and are water cooled. Metal book molds may also
be useful for cooling/quenching the melt.
[0098] Other techniques for forming melts, cooling/quenching melts,
and/or otherwise forming glass include vapor phase quenching,
plasma spraying, melt-extraction, and gas or centrifugal
atomization. Vapor phase quenching can be carried out, for example,
by sputtering, wherein the metal alloys or metal oxide sources are
formed into a sputtering target(s) which are used. The target is
fixed at a predetermined position in a sputtering apparatus, and a
substrate(s) to be coated is placed at a position opposing the
target(s). Typical pressures of 10.sup.-3 torr of oxygen gas and Ar
gas, discharge is generated between the target(s) and a
substrate(s), and Ar or oxygen ions collide against the target to
start reaction sputtering, thereby depositing a film of composition
on the substrate. For additional details regarding plasma spraying,
see, for example, copending application having U.S. Ser. No.
10/211,640, filed the same date as the instant application, the
disclosure of which is incorporated herein by reference.
[0099] Gas atomization involves melting feed particles to convert
them to melt. A thin stream of such melt is atomized through
contact with a disruptive air jet (i.e., the stream is divided into
fine droplets). The resulting substantially discrete, generally
ellipsoidal glass particles (e.g., beads) are then recovered.
Examples of bead sizes include those having a diameter in a range
of about 5 micrometers to about 3 mm. Melt-extraction can be
carried out, for example, as disclosed in U.S. Pat. No. 5,605,870
(Strom-Olsen et al.), the disclosure of which is incorporated
herein by reference. Containerless glass forming techniques
utilizing laser beam heating as disclosed, for example, in PCT
application having Publication No. WO 01/27046 A1, published Apr.
4, 2001, the disclosure of which is incorporated herein by
reference, may also be useful in making glass according to the
present disclosure.
[0100] The cooling rate is believed to affect the properties of the
quenched amorphous material. For instance, glass transition
temperature, density and other properties of glass typically change
with cooling rates.
[0101] Rapid cooling may also be conducted under controlled
atmospheres, such as a reducing, neutral, or oxidizing environment
to maintain and/or influence the desired oxidation states, etc.
during cooling. The atmosphere can also influence glass formation
by influencing crystallization kinetics from undercooled liquid.
For example, larger undercooling of Al.sub.2O.sub.3 melts without
crystallization has been reported in argon atmosphere as compared
to that in air.
[0102] The microstructure or phase composition
(glassy/amorphous/crystalline) of a material can be determined in a
number of ways. Various information can be obtained using optical
microscopy, electron microscopy, differential thermal analysis
(DTA), and x-ray diffraction (XRD), for example.
[0103] Using optical microscopy, amorphous material is typically
predominantly transparent due to the lack of light scattering
centers such as crystal boundaries, while crystalline material
shows a crystalline structure and is opaque due to light scattering
effects.
[0104] A percent amorphous yield can be calculated for beads using
a -100+120 mesh size fraction (i.e., the fraction collected between
150-micrometer opening size and 125-micrometer opening size
screens). The measurements are done in the following manner. A
single layer of beads is spread out upon a glass slide. The beads
are observed using an optical microscope. Using the crosshairs in
the optical microscope eyepiece as a guide, beads that lay along a
straight line are counted either amorphous or crystalline depending
on their optical clarity. A total of 500 beads are counted and a
percent amorphous yield is determined by the amount of amorphous
beads divided by total beads counted.
[0105] Using DTA, the material is classified as amorphous if the
corresponding DTA trace of the material contains an exothermic
crystallization event (T.sub.x). If the same trace also contains an
endothermic event (T.sub.g) at a temperature lower than T.sub.x it
is considered to consist of a glass phase. If the DTA trace of the
material contains no such events, it is considered to contain
crystalline phases.
[0106] Differential thermal analysis (DTA) can be conducted using
the following method. DTA runs can be made (using an instrument
such as that obtained from Netzsch Instruments, Selb, Germany under
the trade designation "NETZSCH STA 409 DTA/TGA") using a -140+170
mesh size fraction (i.e., the fraction collected between
105-micrometer opening size and 90-micrometer opening size
screens). An amount of each screened sample (typically about 400
milligrams (mg)) is placed in a 100-microliter Al.sub.2O.sub.3
sample holder. Each sample is heated in static air at a rate of
10.degree. C./minute from room temperature (about 25.degree. C.) to
1100.degree. C.
[0107] Using powder x-ray diffraction, XRD, (using an x-ray
diffractometer such as that obtained under the trade designation
"PHILLIPS XRG 3100" from Phillips, Mahwah, N.J., with copper K
.alpha.1 radiation of 1.54050 Angstrom) the phases present in a
material can be determined by comparing the peaks present in the
XRD trace of the crystallized material to XRD patterns of
crystalline phases provided in JCPDS (Joint Committee on Powder
Diffraction Standards) databases, published by International Center
for Diffraction Data. Furthermore, an XRD can be used qualitatively
to determine types of phases. The presence of a broad diffused
intensity peak is taken as an indication of the amorphous nature of
a material. The existence of both a broad peak and well-defined
peaks is taken as an indication of existence of crystalline matter
within an amorphous matrix. The initially formed amorphous material
or ceramic (including glass prior to crystallization) may be larger
in size than that desired. The amorphous material or ceramic can be
converted into smaller pieces using crushing and/or comminuting
techniques known in the art, including roll crushing, canary
milling, jaw crushing, hammer milling, ball milling, jet milling,
impact crushing, and the like. In some instances, it is desired to
have two or multiple crushing steps. For example, after the ceramic
is formed (solidified), it may be in the form of larger than
desired. The first crushing step may involve crushing these
relatively large masses or "chunks" to form smaller pieces. This
crushing of these chunks may be accomplished with a hammer mill,
impact crusher or jaw crusher. These smaller pieces may then be
subsequently crushed to produce the desired particle size
distribution. In order to produce the desired particle size
distribution (sometimes referred to as grit size or grade), it may
be necessary to perform multiple crushing steps. In general the
crushing conditions are optimized to achieve the desired particle
shape(s) and particle size distribution. Resulting particles that
are of the desired size may be recrushed if they are too large, or
"recycled" and used as a raw material for re-melting if they are
too small.
[0108] The shape of particles can depend, for example, on the
composition and/or microstructure of the ceramic, the geometry in
which it was cooled, and the manner in which the ceramic is crushed
(i.e., the crushing technique used). In general, where a "blocky"
shape is preferred, more energy may be employed to achieve this
shape. Conversely, where a "sharp" shape is preferred, less energy
may be employed to achieve this shape. The crushing technique may
also be changed to achieve different desired shapes. For some
particles an average aspect ratio ranging from 1:1 to 5:1 is
typically desired, and in some embodiments 1.25:1 to 3:1, or even
1.5:1 to 2.5:1.
[0109] It is also within the scope of the present disclosure, for
example, to directly form articles in desired shapes. For example,
desired articles may be formed (including molded) by pouring or
forming the melt into a mold.
[0110] Surprisingly, it was found that ceramics of present
disclosure could be obtained without limitations in dimensions.
This was found to be possible through a coalescing step performed
at temperatures above glass transition temperature. This coalescing
step in essence forms a larger sized body from two or more smaller
particles. For instance, as evident from FIG. 7, glass of present
disclosure undergoes glass transition (T.sub.g) before significant
crystallization occurs (T.sub.x) as evidenced by the existence of
endotherm (T.sub.g) at lower temperature than exotherm (T.sub.x).
For example, ceramic (including glass prior to crystallization),
may also be provided by heating, for example, particles comprising
the amorphous material, and/or fibers, etc. above the T.sub.g such
that the particles, etc. coalesce to form a shape and cooling the
coalesced shape. The temperature and pressure used for coalescing
may depend, for example, upon composition of the amorphous material
and the desired density of the resulting material. For glasses
temperature should be greater than the glass transition
temperature. In certain embodiments, the heating is conducted at at
least one temperature in a range of about 850.degree. C. to about
1100.degree. C. (in some embodiments, preferably 900.degree. C. to
1000.degree. C.). Typically, the amorphous material is under
pressure (e.g., greater than zero to 1 GPa or more) during
coalescence to aid the coalescence of the amorphous material. In
one embodiment, a charge of the particles, etc. is placed into a
die and hot-pressing is performed at temperatures above glass
transition where viscous flow of glass leads to coalescence into a
relatively large part. Examples of typical coalescing techniques
include hot pressing, hot isostatic pressure, hot extrusion and the
like. For example, amorphous material comprising particles
(obtained, for example, by crushing) (including beads and
microspheres), fibers, etc. may formed into a larger particle size.
Typically, it is generally preferred to cool the resulting
coalesced body before further heat treatment. After heat treatment
if so desired, the coalesced body may be crushed to smaller
particle sizes or a desired particle size distribution.
[0111] It is also within the scope of the present disclosure to
conduct additional heat-treatment to further improve desirable
properties of the material. For example, hot-isostatic pressing may
be conducted (e.g., at temperatures from about 900.degree. C. to
about 1400.degree. C.) to remove residual porosity, increasing the
density of the material. Optionally, the resulting, coalesced
article can be heat-treated to provide glass-ceramic, crystalline
ceramic, or ceramic otherwise comprising crystalline ceramic.
[0112] Coalescing of the amorphous material and/or glass-ceramic
(e.g., particles) may also be accomplished by a variety of methods,
including pressureless or pressure sintering (e.g., sintering,
plasma assisted sintering, hot pressing, HIPing, hot forging, hot
extrusion, etc.).
[0113] Heat-treatment can be carried out in any of a variety of
ways, including those known in the art for heat-treating glass to
provide glass-ceramics. For example, heat-treatment can be
conducted in batches, for example, using resistive, inductively or
gas heated furnaces. Alternatively, for example, heat-treatment can
be conducted continuously, for example, using rotary kilns. In the
case of a rotary kiln, the material is fed directly into a kiln
operating at the elevated temperature. The time at the elevated
temperature may range from a few seconds (in some embodiments even
less than 5 seconds) to a few minutes to several hours. The
temperature may range anywhere from 900.degree. C. to 1600.degree.
C., typically between 1200.degree. C. to 1500.degree. C. It is also
within the scope of the present disclosure to perform some of the
heat-treatment in batches (e.g., for the nucleation step) and
another continuously (e.g., for the crystal growth step and to
achieve the desired density). For the nucleation step, the
temperature typically ranges between about 900.degree. C. to about
1100.degree. C., in some embodiments, preferably in a range from
about 925.degree. C. to about 1050.degree. C. Likewise for the
density step, the temperature typically is in a range from about
1100.degree. C. to about 1600.degree. C., in some embodiments,
preferably in a range from about 1200.degree. C. to about
1500.degree. C. This heat treatment may occur, for example, by
feeding the material directly into a furnace at the elevated
temperature. Alternatively, for example, the material may be feed
into a furnace at a much lower temperature (e.g., room temperature)
and then heated to desired temperature at a predetermined heating
rate. It is within the scope of the present disclosure to conduct
heat-treatment in an atmosphere other than air. In some cases it
might be even desirable to heat-treat in a reducing atmosphere(s).
Also, for, example, it may be desirable to heat-treat under gas
pressure as in, for example, hot-isostatic press, or in gas
pressure furnace. It is within the scope of the present disclosure
to convert (e.g., crush) the resulting article or heat-treated
article to provide particles (e.g., abrasive particles).
[0114] The amorphous material is heat-treated to at least partially
crystallize the amorphous material to provide glass-ceramic. The
heat-treatment of certain glasses to form glass-ceramics is well
known in the art. The heating conditions to nucleate and grow
glass-ceramics are known for a variety of glasses. Alternatively,
one skilled in the art can determine the appropriate conditions
from a Time-Temperature-Transformation (TTT) study of the glass
using techniques known in the art. One skilled in the art, after
reading the disclosure of the present disclosure should be able to
provide TTT curves for glasses according to the present disclosure,
determine the appropriate nucleation and/or crystal growth
conditions to provide glass-ceramics according to the present
disclosure.
[0115] Typically, glass-ceramics are stronger than the amorphous
materials from which they are formed. Hence, the strength of the
material may be adjusted, for example, by the degree to which the
amorphous material is converted to crystalline ceramic phase(s).
Alternatively, or in addition, the strength of the material may
also be affected, for example, by the number of nucleation sites
created, which may in turn be used to affect the number, and in
turn the size of the crystals of the crystalline phase(s). For
additional details regarding forming glass-ceramics, see, for
example, Glass-Ceramics, P. W. McMillan, Academic Press, Inc.,
2.sup.nd edition, 1979, the disclosure of which is incorporated
herein by reference.
[0116] For example, during heat-treatment of some exemplary
amorphous materials for making glass-ceramics according to present
disclosure, formation of phases such as La.sub.2Zr.sub.2O.sub.7,
and, if ZrO.sub.2 is present, cubic/tetragonal ZrO.sub.2, in some
cases monoclinic ZrO.sub.2, have been observed at temperatures
above about 900.degree. C. Although not wanting to be bound by
theory, it is believed that zirconia-related phases are the first
phases to nucleate from the amorphous material. Formation of
Al.sub.2O.sub.3, ReAlO.sub.3 (wherein Re is at least one rare earth
cation), ReAl.sub.11O.sub.18, Re.sub.3Al.sub.5O.sub.12,
Y.sub.3Al.sub.5O.sub.12, etc. phases are believed to generally
occur at temperatures above about 925.degree. C. Typically,
crystallite size during this nucleation step is on order of
nanometers. For example, crystals as small as 10-15 nanometers have
been observed. For at least some embodiments, heat-treatment at
about 1300.degree. C. for about 1 hour provides a full
crystallization. In generally, heat-treatment times for each of the
nucleation and crystal growth steps may range of a few seconds (in
some embodiments even less than 5 seconds) to several minutes to an
hour or more.
[0117] Examples of crystalline phases which may be present in
ceramics according to the present disclosure include: complex
Al.sub.2O.sub.3.quadrature.metal oxide(s) (e.g., complex
Al.sub.2O.sub.3.REO (e.g., ReAlO.sub.3 (e.g., GdAlO.sub.3
LaAlO.sub.3), ReAl.sub.11O.sub.18 (e.g., LaAl.sub.11O.sub.18,), and
Re.sub.3Al.sub.5O.sub.12 (e.g., Dy.sub.3Al.sub.5O.sub.12)), complex
Al.sub.2O.sub.3.Y.sub.2O.sub.3 (e.g., Y.sub.3Al.sub.5O.sub.12), and
complex ZrO.sub.2.REO (e.g., La.sub.2Zr.sub.2O.sub.7)),
Al.sub.2O.sub.3 (e.g., .alpha.-Al.sub.2O.sub.3), and ZrO.sub.2
(e.g., cubic ZrO.sub.2 and tetragonal ZrO.sub.2).
[0118] It is also with in the scope of the present disclosure to
substitute a portion of the yttrium and/or aluminum cations in a
complex Al.sub.2O.sub.3.metal oxide (e.g., complex
Al.sub.2O.sub.3.Y.sub.2O.sub.3 (e.g., yttrium aluminate exhibiting
a garnet crystal structure)) with other cations. For example, a
portion of the Al cations in a complex
Al.sub.2O.sub.3.Y.sub.2O.sub.3 may be substituted with at least one
cation of an element selected from the group consisting of: Cr, Ti,
Sc, Fe, Mg, Ca, Si, Co, and combinations thereof. For example, a
portion of the Y cations in a complex
Al.sub.2O.sub.3.Y.sub.2O.sub.3 may be substituted with at least one
cation of an element selected from the group consisting of: Ce, Dy,
Er, Eu, Gd, Ho, La, Lu, Nd, Pr, Sm, Th, Tm, Yb, Fe, Ti, Mn, V, Cr,
Co, Ni, Cu, Mg, Ca, Sr, and combinations thereof. Similarly, it is
also with in the scope of the present disclosure to substitute a
portion of the aluminum cations in alumina. For example, Cr, Ti,
Sc, Fe, Mg, Ca, Si, and Co can substitute for aluminum in the
alumina. The substitution of cations as described above may affect
the properties (e.g. hardness, toughness, strength, thermal
conductivity, etc.) of the fused material.
[0119] It is also within the scope of the present disclosure to
substitute a portion of the rare earth and/or aluminum cations in a
complex Al.sub.2O.sub.3.metal oxide (e.g., complex
Al.sub.2O.sub.3.REO) with other cations. For example, a portion of
the Al cations in a complex Al.sub.2O.sub.3.REO may be substituted
with at least one cation of an element selected from the group
consisting of: Cr, Ti, Sc, Fe, Mg, Ca, Si, Co, and combinations
thereof. For example, a portion of the Y cations in a complex
Al.sub.2O.sub.3.REO may be substituted with at least one cation of
an element selected from the group consisting of: Y, Fe, Ti, Mn, V,
Cr, Co, Ni, Cu, Mg, Ca, Sr, and combinations thereof. Similarly, it
is also with in the scope of the present disclosure to substitute a
portion of the aluminum cations in alumina. For example, Cr, Ti,
Sc, Fe, Mg, Ca, Si, and Co can substitute for aluminum in the
alumina. The substitution of cations as described above may affect
the properties (e.g. hardness, toughness, strength, thermal
conductivity, etc.) of the fused material.
[0120] The average crystal size can be determined by the line
intercept method according to the ASTM standard E 112-96 "Standard
Test Methods for Determining Average Grain Size". The sample is
mounted in mounting resin (such as that obtained under the trade
designation "TRANSOPTIC POWDER" from Buehler, Lake Bluff, Ill.)
typically in a cylinder of resin about 2.5 cm in diameter and about
1.9 cm high. The mounted section is prepared using conventional
polishing techniques using a polisher (such as that obtained from
Buehler, Lake Bluff, Ill. under the trade designation "ECOMET 3").
The sample is polished for about 3 minutes with a diamond wheel,
followed by 5 minutes of polishing with each of 45, 30, 15, 9, 3,
and 1-micrometer slurries. The mounted and polished sample is
sputtered with a thin layer of gold-palladium and viewed using a
scanning electron microscopy (such as the JEOL SEM Model JSM 840A).
A typical back-scattered electron (BSE) micrograph of the
microstructure found in the sample is used to determine the average
crystal size as follows. The number of crystals that intersect per
unit length (NL) of a random straight line drawn across the
micrograph are counted. The average crystal size is determined from
this number using the following equation.
Average Crystal Size = 1.5 N L M ##EQU00001##
[0121] Where N.sub.L is the number of crystals intersected per unit
length and M is the magnification of the micrograph.
[0122] In another aspect, ceramics (including glass-ceramics)
according to the present disclosure may comprise at least 1, 2, 3,
5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85,
90, 95, 97, 98, 99, or even 100 percent by volume crystallites,
wherein the crystallites have an average size of less than 1
micrometer. In another aspect, ceramics (including glass-ceramics)
according to the present disclosure may comprise less than at least
1, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75,
80, 85, 90, 95, 97, 98, 99, or even 100 percent by volume
crystallites, wherein the crystallites have an average size of less
than 0.5 micrometer. In another aspect, ceramics (including
glass-ceramics) according to the present disclosure may comprise
less than at least 1, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50,
55, 60, 65, 70, 75, 80, 85, 90, 95, 97, 98, 99, or even 100 percent
by volume crystallites, wherein the crystallites have an average
size of less than 0.3 micrometer. In another aspect, ceramics
(including glass-ceramics) according to the present disclosure may
comprise less than at least 1, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40,
45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 97, 98, 99, or even 100
percent by volume crystallites, wherein the crystallites have an
average size of less than 0.15 micrometer.
[0123] Crystalline phases that may be present in ceramics according
to the present disclosure include alumina (e.g., alpha and
transition aluminas), REO, HfO.sub.2 ZrO.sub.2, as well as, for
example, one or more other metal oxides such as BaO, CaO,
Cr.sub.2O.sub.3, CoO, Fe.sub.2O.sub.3, GeO.sub.2, Li.sub.2O, MgO,
MnO, NiO, Na.sub.2O, P.sub.2O.sub.5, Sc.sub.2O.sub.3, SiO.sub.2,
SrO, TeO.sub.2, TiO.sub.2, V.sub.2O.sub.3, Y.sub.2O.sub.3, ZnO,
"complex metal oxides" (including complex Al.sub.2O.sub.3, metal
oxide (e.g., complex Al.sub.2O.sub.3.REO)), and combinations
thereof.
[0124] Additional details regarding ceramics comprising
Al.sub.2O.sub.3, Y.sub.2O.sub.3, and at least one of ZrO.sub.2 or
HfO.sub.2, including making, using, and properties, can be found in
application having U.S. Ser. Nos. 09/922,526, 09/922,528, and
09/922,530, filed Aug. 2, 2001, and U.S. Ser. Nos. 10/211,598;
10/211,630; 10/211,639; 10/211,034; 10/211,044; 10/211,628;
10/211,640; and 10/211,684, filed the same date as the instant
application, the disclosures of which are incorporated herein by
reference.
[0125] Crystals formed by heat-treating amorphous to provide
embodiments of glass-ceramics according to the present disclosure
may be, for example, acicular equiaxed, columnar, or flattened
splat-like features.
[0126] Although an amorphous material, glass-ceramic, etc.
according to the present disclosure may be in the form of a bulk
material, it is also within the scope of the present disclosure to
provide composites comprising an amorphous material, glass-ceramic,
etc. according to the present disclosure. Such a composite may
comprise, for example, a phase or fibers (continuous or
discontinuous) or particles (including whiskers) (e.g., metal oxide
particles, boride particles, carbide particles, nitride particles,
diamond particles, metallic particles, glass particles, and
combinations thereof) dispersed in an amorphous material,
glass-ceramic, etc. according to the present disclosure, disclosure
or a layered-composite structure (e.g., a gradient of glass-ceramic
to amorphous material used to make the glass-ceramic and/or layers
of different compositions of glass-ceramics).
[0127] Certain glasses according to the present disclosure may
have, for example, a T.sub.g in a range of about 750.degree. C. to
about 860.degree. C. Certain glasses according to the present
disclosure may have, for example, a Young's modulus in a range of
about 110 GPa to at least about 150 GPa, crystalline ceramics
according to the present disclosure from about 200 GPa to at least
about 300 GPa, and glass-ceramics according to the present
disclosure or ceramics according to the present disclosure
comprising glass and crystalline ceramic from about 110 GPa to
about 250 GPa. Certain glasses according to the present disclosure
may have, for example, an average toughness (i.e., resistance to
fracture) in a range of about 1 MPa*m.sup.1/2 to about 3
MPa*m.sup.1/2, crystalline ceramics according to the present
disclosure from about 3 MPa*m.sup.1/2 to about 5 MPa*m.sup.1/2, and
glass-ceramics according to the present disclosure or ceramics
according to the present disclosure comprising glass and
crystalline ceramic from about 1 MPa*m.sup.1/2 to about 5
MPa*.sup.m.sup.1/2.
[0128] The average hardness of the material of the present
disclosure can be determined as follows. Sections of the material
are mounted in mounting resin (obtained under the trade designation
"TRANSOPTIC POWDER" from Buehler, Lake Bluff, Ill.) typically in a
cylinder of resin about 2.5 cm in diameter and about 1.9 cm high.
The mounted section is prepared using conventional polishing
techniques using a polisher (such as that obtained from Buehler,
Lake Bluff, Ill. under the trade designation "ECOMET 3"). The
sample is polished for about 3 minutes with a diamond wheel,
followed by 5 minutes of polishing with each of 45, 30, 15, 9, 3,
and 1-micrometer slurries. The microhardness measurements are made
using a conventional microhardness tester (such as that obtained
under the trade designation "MITUTOYO MVK-VL" from Mitutoyo
Corporation, Tokyo, Japan) fitted with a Vickers indenter using a
100-gram indent load. The microhardness measurements are made
according to the guidelines stated in ASTM Test Method E384 Test
Methods for Microhardness of Materials (1991), the disclosure of
which is incorporated herein by reference.
[0129] Certain glasses according to the present disclosure may
have, for example, an average hardness of at least 5 GPa (more
desirably, at least 6 GPa, 7 GPa, 8 GPa, or 9 GPa; typically in a
range of about 5 GPa to about 10 GPa), crystalline ceramics
according to the present disclosure at least 5 GPa (more desirably,
at least 6 GPa, 7 GPa, 8 GPa, 9 GPa, 10 GPa, 11 GPa, 12 GPa, 13
GPa, 14 GPa, 15 GPa, 16 GPa, 17 GPa, or 18 GPa; typically in a
range of about 5 GPa to about 18 GPa), and glass-ceramics according
to the present disclosure or ceramics according to the present
disclosure comprising glass and crystalline ceramic at least 5 GPa
(more desirably, at least 6 GPa, 7 GPa, 8 GPa, 9 GPa, 10 GPa, 11
GPa, 12 GPa, 13 GPa, 14 GPa, 15 GPa, 16 GPa, 17 GPa, or 18 GPa (or
more); typically in a range of about 5 GPa to about 18 GPa).
Abrasive particles according to the present disclosure have an
average hardness of at least 15 GPa, in some embodiments,
preferably, at least 16 GPa, at least 17 GPa, or even at least 18
GPa.
[0130] Certain glasses according to the present disclosure may
have, for example, a thermal expansion coefficient in a range of
about 5.times.10.sup.-6/K to about 11.times.10.sup.-6/K over a
temperature range of at least 25.degree. C. to about 900.degree.
C.
[0131] Typically, and desirably, the (true) density, sometimes
referred to as specific gravity, of ceramic according to the
present disclosure is typically at least 70% of theoretical
density. More desirably, the (true) density of ceramic according to
the present disclosure is at least 75%, 80%, 85%, 90%, 95%, 96%,
97%, 98%, 99%, 99.5% or even 100% of theoretical density. Abrasive
particles according to the present disclosure have densities of at
least 85%, 90%, 92%, 95%, 96%, 97%, 98%, 99%, 99.5% or even 100% of
theoretical density.
[0132] Articles can be made using ceramics according to the present
disclosure, for example, as a filler, reinforcement material,
and/or matrix material. For example, ceramic according to the
present disclosure can be in the form of particles and/or fibers
suitable for use as reinforcing materials in composites (e.g.,
ceramic, metal, or polymeric (thermosetting or thermoplastic)). The
particles and/or fibers may, for example, increase the modulus,
heat resistance, wear resistance, and/or strength of the matrix
material. Although the size, shape, and amount of the particles
and/or fibers used to make a composite may depend, for example, on
the particular matrix material and use of the composite, the size
of the reinforcing particles typically range about 0.1 to 1500
micrometers, more typically 1 to 500 micrometers, and desirably
between 2 to 100 micrometers. The amount of particles for polymeric
applications is typically about 0.5 percent to about 75 percent by
weight, more typically about 1 to about 50 percent by weight.
Examples of thermosetting polymers include: phenolic, melamine,
urea formaldehyde, acrylate, epoxy, urethane polymers, and the
like. Examples of thermoplastic polymers include: nylon,
polyethylene, polypropylene, polyurethane, polyester, polyamides,
and the like.
[0133] Examples of uses for reinforced polymeric materials (i.e.,
reinforcing particles according to the present disclosure dispersed
in a polymer) include protective coatings, for example, for
concrete, furniture, floors, roadways, wood, wood-like materials,
ceramics, and the like, as well as, anti-skid coatings and
injection molded plastic parts and components.
[0134] Further, for example, ceramic according to the present
disclosure can be used as a matrix material. For example, ceramics
according to the present disclosure can be used as a binder for
ceramic materials and the like such as diamond, cubic-BN,
Al.sub.2O.sub.3, ZrO.sub.2, Si.sub.3N.sub.4, and SiC. Examples of
useful articles comprising such materials include composite
substrate coatings, cutting tool inserts abrasive agglomerates, and
bonded abrasive articles such as vitrified wheels. The use of
ceramics according to the present disclosure can be used as binders
may, for example, increase the modulus, heat resistance, wear
resistance, and/or strength of the composite article.
[0135] Abrasive particles according to the present disclosure
generally comprise crystalline ceramic (e.g., at least 75, 80, 85,
90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.5, or even 100 percent
by volume) crystalline ceramic. In another aspect, the present
disclosure provides a plurality of particles having a particle size
distribution ranging from fine to coarse, wherein at least a
portion of the plurality of particles are abrasive particles
according to the present disclosure. In another aspect, embodiments
of abrasive particles according to the present disclosure generally
comprise (e.g., at least 75, 80, 85, 90, 91, 92, 93, 94, 95, 96,
97, 98, 99, 99.5, or even 100 percent by volume) glass-ceramic
according to the present disclosure.
[0136] Abrasive particles according to the present disclosure can
be screened and graded using techniques well known in the art,
including the use of industry recognized grading standards such as
ANSI (American National Standard Institute), FEPA (Federation
Europeenne des Fabricants de Products Abrasifs), and JIS (Japanese
Industrial Standard). Abrasive particles according to the present
disclosure may be used in a wide range of particle sizes, typically
ranging in size from about 0.1 to about 5000 micrometers, more
typically from about 1 to about 2000 micrometers; desirably from
about 5 to about 1500 micrometers, more desirably from about 100 to
about 1500 micrometers.
[0137] In a given particle size distribution, there will be a range
of particle sizes, from coarse particles fine particles. In the
abrasive art this range is sometimes referred to as a "coarse",
"control" and "fine" fractions. Abrasive particles graded according
to industry accepted grading standards specify the particle size
distribution for each nominal grade within numerical limits. Such
industry accepted grading standards include those known as the
American National Standards Institute, Inc. (ANSI) standards,
Federation of European Producers of Abrasive Products (FEPA)
standards, and Japanese Industrial Standard (JIS) standards. ANSI
grade designations (i.e., specified nominal grades) include: ANSI
4, ANSI 6, ANSI 8, ANSI 16, ANSI 24, ANSI 36, ANSI 40, ANSI 50,
ANSI 60, ANSI 80, ANSI 100, ANSI 120, ANSI 150, ANSI 180, ANSI 220,
ANSI 240, ANSI 280, ANSI 320, ANSI 360, ANSI 400, and ANSI 600.
Preferred ANSI grades comprising abrasive particles according to
the present disclosure are ANSI 8-220. FEPA grade designations
include P8, P12, P16, P24, P36, P40, P50, P60, P80, P100, P120,
P150, P180, P220, P320, P400, P500, P600, P800, P1000, and P1200.
Preferred FEPA grades comprising abrasive particles according to
the present disclosure are P12-P220. JIS grade designations include
JIS8, JIS12, JIS16, JIS24, JIS36, JIS46, JIS54, JIS60, JIS80,
JIS100, JIS150, JIS180, JIS220, JIS240, JIS280, JIS320, JIS360,
JIS400, JIS400, JIS600, JIS800, JIS1000, JIS500, JIS2500, JIS4000,
JIS6000, JIS8000, and JIS10,000. Preferred JIS grades comprising
abrasive particles according to the present disclosure are
JIS8-220.
[0138] After crushing and screening, there will typically be a
multitude of different abrasive particle size distributions or
grades. These multitudes of grades may not match a manufacturer's
or supplier's needs at that particular time. To minimize inventory,
it is possible to recycle the off demand grades back into melt to
form glass. This recycling may occur after the crushing step, where
the particles are in large chunks or smaller pieces (sometimes
referred to as "fines") that have not been screened to a particular
distribution.
[0139] In another aspect, the present disclosure provides a method
for making abrasive particles, the method comprising heat-treating
glass particles or glass-containing particles according to the
present disclosure to provide abrasive particles comprising a
glass-ceramic according to the present disclosure. Alternatively,
for example, the present disclosure provides a method for making
abrasive particles, the method comprising heat-treating glass
according to the present disclosure, and crushing the resulting
heat-treated material to provide abrasive particles comprising a
glass-ceramic according to the present disclosure. When crushed,
glass tends to provide sharper particles than crushing
significantly crystallized glass-ceramics or crystalline
material.
[0140] In another aspect, the present disclosure provides
agglomerate abrasive grains each comprising a plurality of abrasive
particles according to the present disclosure bonded together via a
binder. In another aspect, the present disclosure provides an
abrasive article (e.g., coated abrasive articles, bonded abrasive
articles (including vitrified, resinoid, and metal bonded grinding
wheels, cutoff wheels, mounted points, and honing stones), nonwoven
abrasive articles, and abrasive brushes) comprising a binder and a
plurality of abrasive particles, wherein at least a portion of the
abrasive particles are abrasive particles (including where the
abrasive particles are agglomerated) according to the present
disclosure. Methods of making such abrasive articles and using
abrasive articles are well known to those skilled in the art.
Furthermore, abrasive particles according to the present disclosure
can be used in abrasive applications that utilize abrasive
particles, such as slurries of abrading compounds (e.g., polishing
compounds), milling media, shot blast media, vibratory mill media,
and the like.
[0141] Coated abrasive articles generally include a backing,
abrasive particles, and at least one binder to hold the abrasive
particles onto the backing. The backing can be any suitable
material, including cloth, polymeric film, fibre, nonwoven webs,
paper, combinations thereof, and treated versions thereof. The
binder can be any suitable binder, including an inorganic or
organic binder (including thermally curable resins and radiation
curable resins). The abrasive particles can be present in one layer
or in two layers of the coated abrasive article.
[0142] An example of a coated abrasive article is depicted in FIG.
9. Referring to this figure, coated abrasive article 1 has a
backing (substrate) 2 and abrasive layer 3. Abrasive layer 3
includes abrasive particles according to the present disclosure 4
secured to a major surface of backing 2 by make coat 5 and size
coat 6. In some instances, a supersize coat (not shown) is
used.
[0143] Bonded abrasive articles typically include a shaped mass of
abrasive particles held together by an organic, metallic, or
vitrified binder. Such shaped mass can be, for example, in the form
of a wheel, such as a grinding wheel or cutoff wheel. The diameter
of grinding wheels typically is about 1 cm to over 1 meter; the
diameter of cut off wheels about 1 cm to over 80 cm (more typically
3 cm to about 50 cm). The cut off wheel thickness is typically
about 0.5 mm to about 5 cm, more typically about 0.5 mm to about 2
cm. The shaped mass can also be in the form, for example, of a
honing stone, segment, mounted point, disc (e.g. double disc
grinder) or other conventional bonded abrasive shape. Bonded
abrasive articles typically comprise about 3-50% by volume bond
material, about 30-90% by volume abrasive particles (or abrasive
particle blends), up to 50% by volume additives (including grinding
aids), and up to 70% by volume pores, based on the total volume of
the bonded abrasive article.
[0144] A preferred form is a grinding wheel. Referring to FIG. 10,
grinding wheel 10 is depicted, which includes abrasive particles
according to the present disclosure 11, molded in a wheel and
mounted on hub 12.
[0145] Nonwoven abrasive articles typically include an open porous
lofty polymer filament structure having abrasive particles
according to the present disclosure distributed throughout the
structure and adherently bonded therein by an organic binder.
Examples of filaments include polyester fibers, polyamide fibers,
and polyaramid fibers. In FIG. 11, a schematic depiction, enlarged
about 100.times., of a typical nonwoven abrasive article is
provided. Such a nonwoven abrasive article comprises fibrous mat 50
as a substrate, onto which abrasive particles according to the
present disclosure 52 are adhered by binder 54.
[0146] Useful abrasive brushes include those having a plurality of
bristles unitary with a backing (see, e.g., U.S. Pat. No. 5,427,595
(Pihl et al.), U.S. Pat. No. 5,443,906 (Pihl et al.), U.S. Pat. No.
5,679,067 (Johnson et al.), and U.S. Pat. No. 5,903,951 (Ionta et
al.), the disclosure of which is incorporated herein by reference).
Desirably, such brushes are made by injection molding a mixture of
polymer and abrasive particles.
[0147] Suitable organic binders for making abrasive articles
include thermosetting organic polymers. Examples of suitable
thermosetting organic polymers include phenolic resins,
urea-formaldehyde resins, melamine-formaldehyde resins, urethane
resins, acrylate resins, polyester resins, aminoplast resins having
pendant .alpha.,.beta.-unsaturated carbonyl groups, epoxy resins,
acrylated urethane, acrylated epoxies, and combinations thereof The
binder and/or abrasive article may also include additives such as
fibers, lubricants, wetting agents, thixotropic materials,
surfactants, pigments, dyes, antistatic agents (e.g., carbon black,
vanadium oxide, graphite, etc.), coupling agents (e.g., silanes,
titanates, zircoaluminates, etc.), plasticizers, suspending agents,
and the like. The amounts of these optional additives are selected
to provide the desired properties. The coupling agents can improve
adhesion to the abrasive particles and/or filler. The binder
chemistry may thermally cured, radiation cured or combinations
thereof Additional details on binder chemistry may be found in U.S.
Pat. No. 4,588,419 (Caul et al.), U.S. Pat. No. 4,751,138 (Tumey et
al.), and U.S. Pat. No. 5,436,063 (Follett et al.), the disclosures
of which are incorporated herein by reference.
[0148] More specifically with regard to vitrified bonded abrasives,
vitreous bonding materials, which exhibit an amorphous structure
and are typically hard, are well known in the art. In some cases,
the vitreous bonding material includes crystalline phases. Bonded,
vitrified abrasive articles according to the present disclosure may
be in the shape of a wheel (including cut off wheels), honing
stone, mounted pointed or other conventional bonded abrasive shape.
A preferred vitrified bonded abrasive article according to the
present disclosure is a grinding wheel.
[0149] Examples of metal oxides that are used to form vitreous
bonding materials include: silica, silicates, alumina, soda,
calcia, potassia, titania, iron oxide, zinc oxide, lithium oxide,
magnesia, boria, aluminum silicate, borosilicate glass, lithium
aluminum silicate, combinations thereof, and the like. Typically,
vitreous bonding materials can be formed from composition
comprising from 10 to 100% glass frit, although more typically the
composition comprises 20% to 80% glass frit, or 30% to 70% glass
frit. The remaining portion of the vitreous bonding material can be
a non-frit material. Alternatively, the vitreous bond may be
derived from a non-frit containing composition. Vitreous bonding
materials are typically matured at a temperature(s) in a range of
about 700.degree. C. to about 1500.degree. C., usually in a range
of about 800.degree. C. to about 1300.degree. C., sometimes in a
range of about 900.degree. C. to about 1200.degree. C., or even in
a range of about 950.degree. C. to about 1100.degree. C. The actual
temperature at which the bond is matured depends, for example, on
the particular bond chemistry.
[0150] Preferred vitrified bonding materials may include those
comprising silica, alumina (desirably, at least 10 percent by
weight alumina), and boria (desirably, at least 10 percent by
weight boria). In most cases the vitrified bonding material further
comprise alkali metal oxide(s) (e.g., Na.sub.2O and K.sub.2O) (in
some cases at least 10 percent by weight alkali metal
oxide(s)).
[0151] Binder materials may also contain filler materials or
grinding aids, typically in the form of a particulate material.
Typically, the particulate materials are inorganic materials.
Examples of useful fillers for this disclosure include: metal
carbonates (e.g., calcium carbonate (e.g., chalk, calcite, marl,
travertine, marble and limestone), calcium magnesium carbonate,
sodium carbonate, magnesium carbonate), silica (e.g., quartz, glass
beads, glass bubbles and glass fibers) silicates (e.g., talc,
clays, (montmorillonite) feldspar, mica, calcium silicate, calcium
metasilicate, sodium aluminosilicate, sodium silicate) metal
sulfates (e.g., calcium sulfate, barium sulfate, sodium sulfate,
aluminum sodium sulfate, aluminum sulfate), gypsum, vermiculite,
wood flour, aluminum trihydrate, carbon black, m metal oxides
(e.g., calcium oxide (lime), aluminum oxide, titanium dioxide), and
metal sulfites (e.g., calcium sulfite).
[0152] In general, the addition of a grinding aid increases the
useful life of the abrasive article. A grinding aid is a material
that has a significant effect on the chemical and physical
processes of abrading, which results in improved performance.
Although not wanting to be bound by theory, it is believed that a
grinding aid(s) will (a) decrease the friction between the abrasive
particles and the workpiece being abraded, (b) prevent the abrasive
particles from "capping" (i.e., prevent metal particles from
becoming welded to the tops of the abrasive particles), or at least
reduce the tendency of abrasive particles to cap, (c) decrease the
interface temperature between the abrasive particles and the
workpiece, or (d) decreases the grinding forces.
[0153] Grinding aids encompass a wide variety of different
materials and can be inorganic or organic based. Examples of
chemical groups of grinding aids include waxes, organic halide
compounds, halide salts and metals and their alloys. The organic
halide compounds will typically break down during abrading and
release a halogen acid or a gaseous halide compound. Examples of
such materials include chlorinated waxes like
tetrachloronaphtalene, pentachloronaphthalene, and polyvinyl
chloride. Examples of halide salts include sodium chloride,
potassium cryolite, sodium cryolite, ammonium cryolite, potassium
tetrafluoroboate, sodium tetrafluoroborate, silicon fluorides,
potassium chloride, and magnesium chloride. Examples of metals
include, tin, lead, bismuth, cobalt, antimony, cadmium, and iron
titanium. Other miscellaneous grinding aids include sulfur, organic
sulfur compounds, graphite, and metallic sulfides. It is also
within the scope of the present disclosure to use a combination of
different grinding aids, and in some instances this may produce a
synergistic effect. The preferred grinding aid is cryolite; the
most preferred grinding aid is potassium tetrafluoroborate.
[0154] Grinding aids can be particularly useful in coated abrasive
and bonded abrasive articles. In coated abrasive articles, grinding
aid is typically used in the supersize coat, which is applied over
the surface of the abrasive particles. Sometimes, however, the
grinding aid is added to the size coat. Typically, the amount of
grinding aid incorporated into coated abrasive articles are about
50-300 g/m.sup.2 (desirably, about 80-160 g/m.sup.2). In vitrified
bonded abrasive articles grinding aid is typically impregnated into
the pores of the article.
[0155] The abrasive articles can contain 100% abrasive particles
according to the present disclosure, or blends of such abrasive
particles with other abrasive particles and/or diluent particles.
However, at least about 2% by weight, desirably at least about 5%
by weight, and more desirably about 30-100% by weight, of the
abrasive particles in the abrasive articles should be abrasive
particles according to the present disclosure. In some instances,
the abrasive particles according the present disclosure may be
blended with another abrasive particles and/or diluent particles at
a ratio between 5 to 75% by weight, about 25 to 75% by weight about
40 to 60% by weight, or about 50% to 50% by weight (i.e., in equal
amounts by weight). Examples of suitable conventional abrasive
particles include fused aluminum oxide (including white fused
alumina, heat-treated aluminum oxide and brown aluminum oxide),
silicon carbide, boron carbide, titanium carbide, diamond, cubic
boron nitride, garnet, fused alumina-zirconia, and sol-gel-derived
abrasive particles, and the like. The sol-gel-derived abrasive
particles may be seeded or non-seeded. Likewise, the
sol-gel-derived abrasive particles may be randomly shaped or have a
shape associated with them, such as a rod or a triangle. Examples
of sol gel abrasive particles include those described U.S. Pat. No.
4,314,827 (Leitheiser et al.), U.S. Pat. No. 4,518,397 (Leitheiser
et al.), U.S. Pat. No. 4,623,364 (Cottringer et al.), U.S. Pat. No.
4,744,802 (Schwabel), U.S. Pat. No. 4,770,671 (Monroe et al.), U.S.
Pat. No. 4,881,951 (Wood et al.), U.S. Pat. No. 5,011,508 (Wald et
al.), U.S. Pat. No. 5,090,968 (Pellow), U.S. Pat. No. 5,139,978
(Wood), U.S. Pat. No. 5,201,916 (Berg et al.), U.S. Pat. No.
5,227,104 (Bauer), U.S. Pat. No. 5,366,523 (Rowenhorst et al.),
U.S. Pat. No. 5,429,647 (Larmie), U.S. Pat. No. 5,498,269 (Larmie),
and U.S. Pat. No. 5,551,963 (Larmie), the disclosures of which are
incorporated herein by reference. Additional details concerning
sintered alumina abrasive particles made by using alumina powders
as a raw material source can also be found, for example, in U.S.
Pat. No. 5,259,147 (Falz), U.S. Pat. No. 5,593,467 (Monroe), and
U.S. Pat. No. 5,665,127 (Moltgen), the disclosures of which are
incorporated herein by reference. Additional details concerning
fused abrasive particles, can be found, for example, in U.S. Pat.
No. 1,161,620 (Coulter), U.S. Pat. No. 1,192,709 (Tone), U.S. Pat.
No. 1,247,337 (Saunders et al.), U.S. Pat. No. 1,268,533 (Allen),
and U.S. Pat. No. 2,424,645 (Baumann et al.), U.S. Pat. No.
3,891,408 (Rowse et al.), U.S. Pat. No. 3,781,172 (Pett et al.),
U.S. Pat. No. 3,893,826 (Quinan et al.), U.S. Pat. No. 4,126,429
(Watson), U.S. Pat. No. 4,457,767 (Poon et al.), U.S. Pat. No.
5,023,212 (Dubots et al.), U.S. Pat. No. 5,143,522 (Gibson et al.),
and U.S. Pat. No. 5,336,280 (Dubots et al.), and applications
having U.S. Ser. Nos. 09/495,978, 09/496,422, 09/496,638, and
09/496,713, each filed on Feb. 2, 2000, and, Ser. Nos. 09/618,876,
09/618,879, 09/619,106, 09/619,191, 09/619,192, 09/619,215,
09/619,289, 09/619,563, 09/619,729, 09/619,744, and 09/620,262,
each filed on Jul. 19, 2000, and Ser. No. 09/772,730, filed Jan.
30, 2001, the disclosures of which are incorporated herein by
reference. In some instances, blends of abrasive particles may
result in an abrasive article that exhibits improved grinding
performance in comparison with abrasive articles comprising 100% of
either type of abrasive particle.
[0156] If there is a blend of abrasive particles, the abrasive
particle types forming the blend may be of the same size.
Alternatively, the abrasive particle types may be of different
particle sizes. For example, the larger sized abrasive particles
may be abrasive particles according to the present disclosure, with
the smaller sized particles being another abrasive particle type.
Conversely, for example, the smaller sized abrasive particles may
be abrasive particles according to the present disclosure, with the
larger sized particles being another abrasive particle type.
[0157] Examples of suitable diluent particles include marble,
gypsum, flint, silica, iron oxide, aluminum silicate, glass
(including glass bubbles and glass beads), alumina bubbles, alumina
beads and diluent agglomerates. Abrasive particles according to the
present disclosure can also be combined in or with abrasive
agglomerates. Abrasive agglomerate particles typically comprise a
plurality of abrasive particles, a binder, and optional additives.
The binder may be organic and/or inorganic. Abrasive agglomerates
may be randomly shape or have a predetermined shape associated with
them. The shape may be a block, cylinder, pyramid, coin, square, or
the like. Abrasive agglomerate particles typically have particle
sizes ranging from about 100 to about 5000 micrometers, typically
about 250 to about 2500 micrometers. Additional details regarding
abrasive agglomerate particles may be found, for example, in U.S.
Pat. No. 4,311,489 (Kressner), U.S. Pat. No. 4,652,275 (Bloecher et
al.), U.S. Pat. No. 4,799,939 (Bloecher et al.), U.S. Pat. No.
5,549,962 (Holmes et al.), and U.S. Pat. No. 5,975,988
(Christianson), and applications having U.S. Ser. Nos. 09/688,444
and 09/688,484, filed Oct. 16, 2000, the disclosures of which are
incorporated herein by reference.
[0158] The abrasive particles may be uniformly distributed in the
abrasive article or concentrated in selected areas or portions of
the abrasive article. For example, in a coated abrasive, there may
be two layers of abrasive particles. The first layer comprises
abrasive particles other than abrasive particles according to the
present disclosure, and the second (outermost) layer comprises
abrasive particles according to the present disclosure. Likewise in
a bonded abrasive, there may be two distinct sections of the
grinding wheel. The outermost section may comprise abrasive
particles according to the present disclosure, whereas the
innermost section does not. Alternatively, abrasive particles
according to the present disclosure may be uniformly distributed
throughout the bonded abrasive article.
[0159] Further details regarding coated abrasive articles can be
found, for example, in U.S. Pat. No. 4,734,104 (Broberg), U.S. Pat.
No. 4,737,163 (Larkey), U.S. Pat. No. 5,203,884 (Buchanan et al.),
U.S. Pat. No. 5,152,917 (Pieper et al.), U.S. Pat. No. 5,378,251
(Culler et al.), U.S. Pat. No. 5,417,726 (Stout et al.), U.S. Pat.
No. 5,436,063 (Follett et al.), U.S. Pat. No. 5,496,386 (Broberg et
al.), U.S. Pat. No. 5, 609,706 (Benedict et al.), U.S. Pat. No.
5,520,711 (Helmin), U.S. Pat. No. 5,954,844 (Law et al.), U.S. Pat.
No. 5,961,674 (Gagliardi et al.), and U.S. Pat. No. 5,975,988
(Christianson), the disclosures of which are incorporated herein by
reference. Further details regarding bonded abrasive articles can
be found, for example, in U.S. Pat. No. 4,543,107 (Rue), U.S. Pat.
No. 4,741,743 (Narayanan et al.), U.S. Pat. No. 4,800,685 (Haynes
et al.), U.S. Pat. No. 4,898,597 (Hay et al.), U.S. Pat. No.
4,997,461 (Markhoff-Matheny et al.), U.S. Pat. No. 5,037,453
(Narayanan et al.), U.S. Pat. No. 5,110,332 (Narayanan et al.), and
U.S. Pat. No. 5,863,308 (Qi et al.) the disclosures of which are
incorporated herein by reference. Further details regarding
vitreous bonded abrasives can be found, for example, in U.S. Pat.
No. 4,543,107 (Rue), U.S. Pat. No. 4,898,597 (Hay et al.), U.S.
Pat. No. 4,997,461 (Markhoff-Matheny et al.), U.S. Pat. No.
5,094,672 (Giles Jr. et al.), U.S. Pat. No. 5,118,326 (Sheldon et
al.), U.S. Pat. No. 5,131,926 (Sheldon et al.), U.S. Pat. No.
5,203,886 (Sheldon et al.), U.S. Pat. No. 5,282,875 (Wood et al.),
U.S. Pat. No. 5,738,696 (Wu et al.), and U.S. Pat. No. 5,863,308
(Qi), the disclosures of which are incorporated herein by
reference. Further details regarding nonwoven abrasive articles can
be found, for example, in U.S. Pat. No. 2,958,593 (Hoover et al.),
the disclosure of which is incorporated herein by reference.
[0160] The present disclosure provides a method of abrading a
surface, the method comprising contacting at least one abrasive
particle according to the present disclosure, with a surface of a
workpiece; and moving at least of one the abrasive particle or the
contacted surface to abrade at least a portion of said surface with
the abrasive particle. Methods for abrading with abrasive particles
according to the present disclosure range of snagging (i.e., high
pressure high stock removal) to polishing (e.g., polishing medical
implants with coated abrasive belts), wherein the latter is
typically done with finer grades (e.g., less ANSI 220 and finer) of
abrasive particles. The abrasive particle may also be used in
precision abrading applications, such as grinding cam shafts with
vitrified bonded wheels. The size of the abrasive particles used
for a particular abrading application will be apparent to those
skilled in the art.
[0161] Abrading with abrasive particles according to the present
disclosure may be done m dry or wet. For wet abrading, the liquid
may be introduced supplied in the form of a light mist to complete
flood. Examples of commonly used liquids include: water,
water-soluble oil, organic lubricant, and emulsions. The liquid may
serve to reduce the heat associated with abrading and/or act as a
lubricant. The liquid may contain minor amounts of additives such
as bactericide, antifoaming agents, and the like.
[0162] Abrasive particles according to the present disclosure may
be used to abrade workpieces such as aluminum metal, carbon steels,
mild steels, tool steels, stainless steel, hardened steel,
titanium, glass, ceramics, wood, wood like materials, paint,
painted surfaces, organic coated surfaces and the like. The applied
force during abrading typically ranges from about 1 to about 100
kilograms.
[0163] Advantages and embodiments of this disclosure are further
illustrated by the following examples, but the particular materials
and amounts thereof recited in these examples, as well as other
conditions and details, should not be construed to unduly limit
this disclosure. All parts and percentages are by weight unless
otherwise indicated. Unless otherwise stated, all examples
contained no significant amount of SiO.sub.2, B.sub.2O.sub.3,
P.sub.2O.sub.5, GeO.sub.2, TeO.sub.2, As.sub.2O.sub.3, and
V.sub.2O.sub.5.
EXAMPLES
Example 1
[0164] A polyethylene bottle was charged with 132.36 grams (g) of
alumina particles (obtained under the trade designation "APA-0.5"
from Condea Vista, Tucson, Ariz.), 122.64 grams of lanthanum oxide
particles (obtained from Molycorp, Inc.), 45 grams of zirconium
oxide particles (with a nominal composition of 100 wt-% ZrO.sub.2
(+HfO.sub.2); obtained under the trade designation "DK-2" from
Zirconia Sales, Inc. of Marietta, Ga.) and 150.6 grams of distilled
water. About 450 grams of alumina milling media (10 mm diameter;
99.9% alumina; obtained from Union Process, Akron, OH) were added
to the bottle, and the mixture was milled at 120 revolutions per
minute (rpm) for 4 hours to thoroughly mix the ingredients. After
the milling, the milling media were removed and the slurry was
poured onto a glass ("PYREX") pan where it was dried using a
heat-gun. The dried mixture was ground with a mortar and pestle and
screened through a 70-mesh screen (212-micrometer opening
size).
[0165] A small quantity of the dried particles was melted in an arc
discharge furnace (Model No. 5T/A 39420; from Centorr Vacuum
Industries, Nashua, N.H.). About 1 gram of the dried and sized
particles was placed on a chilled copper plate located inside the
furnace chamber. The furnace chamber was evacuated and then
backfilled with Argon gas at 13.8 kilopascals (kPa) (2 pounds per
square inch (psi)) pressure. An arc was struck between an electrode
and a plate. The temperatures generated by the arc discharge were
high enough to quickly melt the dried and sized particles. After
melting was complete, the material was maintained in a molten state
for about 10 seconds to homogenize the melt. The resultant melt was
rapidly cooled by shutting off the arc and allowing the melt to
cool on its own. Rapid cooling was ensured by the small mass of the
sample and the large heat sinking capability of the water chilled
copper plate. The fused material was removed from the furnace
within one minute after the power to the furnace was turned off
Although not wanting to be bound by theory, it is estimated that
the cooling rate of the melt on the surface of the water chilled
copper plate was above 100.degree. C./second. The fused material
were transparent glass beads (largest diameter of a bead was
measured at 2.8 millimeters (mm))
[0166] FIG. 1 is an X-Ray diffraction pattern of Example 1 glass
beads. The broad diffused peak indicates the amorphous nature of
the material.
Comparative Example A
[0167] Comparative Example A fused material was prepared as
described in Example 1, except the polyethylene bottle was charged
with 229.5 grams of alumina particles ("APA-0.5"), 40.5 grams of
lanthanum oxide particles (obtained from Molycorp, Inc.), 30 grams
of zirconium oxide particles ("DK-2"), 0.6 gram of a dispersing
agent ("DURAMAX D-30005"), and 145 grams of distilled water.
[0168] FIG. 2 is a scanning electron microscope (SEM)
photomicrograph of a polished section (prepared as described in
Example 6) of fused Comparative Example A material. The
photomicrograph shows a crystalline, eutectic-derived
microstructure comprising a plurality of colonies. The colonies
were about 5-20 micrometers in size. Based on powder X-ray
diffraction of a portion of Comparative Example A material, and
examination of the polished sample using SEM in the backscattered
mode, it is believed that the dark portions in the photomicrograph
were crystalline Al.sub.2O.sub.3, the gray portions crystalline
LaAl.sub.11O.sub.18, and the white portions crystalline,
monoclinic-ZrO.sub.2.
Example 2
[0169] Example 2 fused material was prepared as described in
Example 1, except the polyethylene bottle was charged with 109
grams of alumina particles ("APA-0.5"), 101 grams of lanthanum
oxide particles (obtained from Molycorp, Inc.), 9 grams of yttrium
oxide particles (obtained from H.C. Starck, Newton, Mass.), 81
grams of zirconium oxide particles ("DK-2"), 0.6 gram of a
dispersing agent ("DURAMAX D-30005"), and 145 grams of distilled
water. The fused material obtained was transparent greenish
glass.
[0170] Several Example 2 glass spheres were placed inside a furnace
between two flat Al.sub.2O.sub.3 plates. A 300-gram load was
applied to the top plate using a dead weight. The glass spheres
were heated in air at 930.degree. C. for 1.5 hours. The
heat-treated glass spheres were deformed with large flat caps on
both sides, illustrating that the glass spheres underwent viscous
flow during the heating. Referring to FIG. 3, the arc-melted
spheres are on the right, the deformed, heat-treated spheres on the
left.
Example 3
[0171] Example 3 fused material was prepared as described in
Example 1, except the polyethylene bottle was charged with 20.49
grams of alumina particles ("APA-0.5"), 20.45 grams of lanthanum
oxide particles (obtained from Molycorp, Inc.), 9.06 grams of
yttria-stabilized zirconium oxide particles (with a nominal
composition of 94.6 percent by weight (wt-%) ZrO.sub.2 (+HfO.sub.2)
and 5.4 wt-% Y.sub.2O.sub.3; obtained under the trade designation
"HSY-3" from Zirconia Sales, Inc. of Marietta, Ga.) and 80 grams of
distilled water. The fused material obtained was transparent
glass.
Example 4
[0172] Example 4 fused material was prepared as described in
Example 1, except the polyethylene bottle was charged with 21.46
grams of alumina particles ("APA-0.5"), 21.03 grams of cerium (IV)
oxide (CeO.sub.2) particles, (obtained from Aldrich Chemical
Company, Inc., Milwaukee, Wis.), 7.5 grams of zirconium oxide
particles ("DK-2") and 145 grams of distilled water. The fused
material obtained was dark-brown Semi-transparent.
Example 5
[0173] Example 5 fused material was prepared as described in
Example 1, except the polyethylene bottle was charged with 20.4
grams of alumina particles ("APA-0.5"), 22.1 grams of ytterbium
oxide particles, (obtained from Aldrich Chemical Company, Inc.,
Milwaukee, Wis.), 7.5 grams of zirconium oxide particles ("DK-2")
and 24.16 grams of distilled water. The fused material obtained was
transparent.
Example 6
[0174] Example 6 material was prepared as described in Example 1,
except the polyethylene bottle was replaced by a polyurethane-lined
mill which was charged with 819.6 grams of alumina particles
("APA-0.5"), 818 grams of lanthanum oxide particles (obtained from
Molycorp, Inc.), 362.4 grams of yttria-stabilized zirconium oxide
particles (with a nominal composition of 94.6 wt-% ZrO.sub.2
(+HfO.sub.2) and 5.4 wt-% Y.sub.2O.sub.3; obtained under the trade
designation "HSY-3" from Zirconia Sales, Inc. of Marietta, Ga.),
1050 grams of distilled water and about 2000 grams of zirconia
milling media (obtained from Tosoh Ceramics, Division of Bound
Brook, N.J., under the trade designation "YTZ").
[0175] After grinding and screening, some of the particles were fed
into a hydrogen/oxygen torch flame. The torch used to melt the
particles, thereby generating melted glass beads, was a Bethlehem
bench burner PM2D model B, obtained from Bethlehem Apparatus Co.,
Hellertown, Pa., delivering hydrogen and oxygen at the following
rates. For the inner ring, the hydrogen flow rate was 8 standard
liters per minute (SLPM) and the oxygen flow rate was 3 SLPM. For
the outer ring, the hydrogen flow rate was 23 (SLPM) and the oxygen
flow rate was 9.8 SLPM. The dried and sized particles were fed
directly into the torch flame, where they were melted and
transported to an inclined stainless steel surface (approximately
51 centimeters (cm) (20 inches) wide with the slope angle of 45
degrees) with cold water running over (approximately 8
liters/minute) the surface to form beads.
[0176] About 50 grams of the beads were placed in a graphite die
and hot-pressed using a uniaxial pressing apparatus (obtained under
the trade designation "HP-50", Thermal Technology Inc., Brea,
Calif.). The hot-pressing was carried out at 960.degree. C. in an
argon atmosphere and 13.8 megapascals (MPa) (2000 pounds per square
inch (2 ksi)) pressure. The resulting translucent disk was about 48
millimeters in diameter, and about 5 mm thick. Additional hot-press
runs were performed to make additional disks. FIG. 4 is an optical
photomicrograph of a sectioned bar (2-mm thick) of the hot-pressed
material demonstrating its transparency.
[0177] The density of the resulting hot-pressed glass material was
measured using
[0178] Archimedes method, and found to be within a range of about
4.1-4.4 g/cm.sup.3. The Youngs' modulus (E) of the resulting
hot-pressed glass material was measured using a ultrasonic test
system (obtained from Nortek, Richland, Wash. under the trade
designation "NDT-140"), and found to be within a range of about
130-150 GPa.
[0179] The average microhardnesses of the resulting hot-pressed
material was determined as follows. Pieces of the hot-pressed
material (about 2-5 millimeters in size) were mounted in mounting
resin (obtained under the trade designation "EPOMET" from Buehler
Ltd., Lake Bluff, Ill.). The resulting cylinder of resin was about
2.5 cm (1 inch) in diameter and about 1.9 cm (0.75 inch) tall
(i.e., high). The mounted samples were polished using a
conventional grinder/polisher (obtained under the trade designation
"EPOMET" from Buehler Ltd.) and conventional diamond slurries with
the final polishing step using a 1-micrometer diamond slurry
(obtained under the trade designation "METADI" from Buehler Ltd.)
to obtain polished cross-sections of the sample.
[0180] The microhardness measurements were made using a
conventional microhardness tester (obtained under the trade
designation "MITUTOYO MVK-VL" from Mitutoyo Corporation, Tokyo,
Japan) fitted with a Vickers indenter using a 500-gram indent load.
The microhardness measurements were made according to the
guidelines stated in ASTM Test Method E384 Test Methods for
Microhardness of Materials (1991), the disclosure of which is
incorporated herein by reference. The microhardness values were an
average of 20 measurements. The average microhardness of the
hot-pressed material was about 8.3 GPa.
[0181] The average indentation toughness of the hot-pressed
material was calculated by measuring the crack lengths extending
from the apices of the vickers indents made using a 500 gram load
with a microhardness tester (obtained under the trade designation
"MITUTOYO MVK-VL" from Mitutoyo Corporation, Tokyo, Japan).
Indentation toughness (K.sub.IC) was calculated according to the
equation:
K.sub.IC=0.016 (E/H).sup.1/2 (P/c).sup.3/2
wherein: E=Young's Modulus of the material; [0182] H=Vickers
hardness; [0183] P=Newtons of force on the indenter; [0184]
c=Length of the crack from the center of the indent to its end.
[0185] Samples for the toughness were prepared as described above
for the microhardness test. The reported indentation toughness
values are an average of 5 measurements. Crack (c) were measured
with a digital caliper on photomicrographs taken using a scanning
electron microscope ("JEOL SEM" (Model JSM 6400)). The average
indentation toughness of the hot-pressed material was 1.4
MPam.sup.1/2.
[0186] The thermal expansion coefficient of the hot-pressed
material was measured using a thermal analyser (obtained from
Perkin Elmer, Shelton, Conn., under the trade designation "PERKIN
ELMER THERMAL ANALYSER"). The average thermal expansion coefficient
was 7.6.times.10.sup.-6/.degree.C.
[0187] The thermal conductivity of the hot-pressed material was
measured according to an ASTM standard "D 5470-95, Test Method A"
(1995), the disclosure of which is incorporated herein by
reference. The average thermal conductivity was 1.15 W/m*K.
[0188] The translucent disk of hot-pressed
La.sub.2O.sub.3--Al.sub.2O.sub.3--ZrO.sub.2 glass was heat-treated
in a furnace (an electrically heated furnace (obtained under the
trade designation "Model KKSK-666-3100" from Keith Furnaces of Pico
Rivera, Calif.)) as follows. The disk was first heated from room
temperature (about 25.degree. C.) to about 900.degree. C. at a rate
of about 10.degree. C./min and then held at 900.degree. C. for
about 1 hour. Next, the disk was heated from about 900.degree. C.
to about 1300.degree. C. at a rate of about 10.degree. C./min and
then held at 1300.degree. C. for about 1 hour, before cooling back
to room temperature by turning off the furnace. Additional runs
were performed with the same heat-treatment schedule to make
additional disks.
[0189] FIG. 5 is a scanning electron microscope (SEM)
photomicrograph of a polished section of heat-treated Example 6
material showing the fine crystalline nature of the material. The
polished section was prepared using conventional mounting and
polishing techniques. Polishing was done using a polisher (obtained
from Buehler of Lake Bluff, Ill. under the trade designation
"ECOMET 3 TYPE POLISHER-GRINDER"). The sample was polished for
about 3 minutes with a diamond wheel, followed by three minutes of
polishing with each of 45, 30, 15, 9, and 3-micrometer diamond
slurries. The polished sample was coated with a thin layer of
gold-palladium and viewed using JEOL SEM (Model JSM 840A).
[0190] Based on powder X-ray diffraction of a portion of
heat-treated Example 6 material and examination of the polished
sample using SEM in the backscattered mode, it is believed that the
dark portions in the photomicrograph were crystalline
LaAl.sub.11O.sub.18, the gray portions crystalline LaAlO.sub.3, and
the white portions crystalline cubic/tetragonal ZrO.sub.2.
[0191] The density of the heat-treated material was measured using
Archimedes method, and found to be about 5.18 g/cm.sup.3. The
Youngs' modulus (E) of the heat-treated material was measured using
an ultrasonic test system (obtained from Nortek, Richland, Wash.
under the trade designation "NDT-140"), and found to be about 260
GPa. The average microhardness of the heat-treated material was
determined as described above for the Example 6 glass beads, and
was found to be 18.3 GPa. The average fracture toughness (K.sub.ic)
of the heat-treated material was determined as described above for
the Example 6 hot-pressed material, and was found to be 3.3
MPa*m.sup.1/2.
Examples 7-40
[0192] Examples 7-40 beads were prepared as described in Example 6,
except the raw materials and the amounts of raw materials, used are
listed in Table 1, below, and the milling of the raw materials was
carried out in 90 milliliters (ml) of isopropyl alcohol with 200
grams of the zirconia media (obtained from Tosoh Ceramics, Division
of Bound Brook, N.J., under the trade designation "YTZ") at 120 rpm
for 24 hours. The sources of the raw materials used are listed in
Table 2, below.
TABLE-US-00001 TABLE 1 Weight percent of Example components Batch
amounts, g 7 La.sub.2O.sub.3: 45.06 La.sub.2O.sub.3: 22.53
Al.sub.2O.sub.3: 34.98 Al.sub.2O.sub.3: 17.49 ZrO.sub.2: 19.96
ZrO.sub.2: 9.98 8 La.sub.2O.sub.3: 42.29 La.sub.2O.sub.3: 21.15
Al.sub.2O.sub.3: 38.98 Al.sub.2O.sub.3: 19.49 ZrO.sub.2: 8.73
ZrO.sub.2: 9.37 9 La.sub.2O.sub.3: 39.51 La.sub.2O.sub.3: 19.76
Al.sub.2O.sub.3: 42.98 Al.sub.2O.sub.3: 21.49 ZrO.sub.2: 17.51
ZrO.sub.2: 8.76 10 La.sub.2O.sub.3: 36.74 La.sub.2O.sub.3: 18.37
Al.sub.2O.sub.3: 46.98 Al.sub.2O.sub.3: 23.49 ZrO.sub.2: 16.28
ZrO.sub.2: 8.14 11 La.sub.2O.sub.3: 38.65 La.sub.2O.sub.3: 19.33
Al.sub.2O.sub.3: 38.73 Al.sub.2O.sub.3: 19.37 ZrO.sub.2: 22.62
ZrO.sub.2: 11.31 12 La.sub.2O.sub.3: 40.15 La.sub.2O.sub.3: 20.08
Al.sub.2O.sub.3: 40.23 Al.sub.2O.sub.3: 20.12 ZrO.sub.2: 19.62
ZrO.sub.2: 9.81 13 La.sub.2O.sub.3: 43.15 La.sub.2O.sub.3: 21.58
Al.sub.2O.sub.3: 43.23 Al.sub.2O.sub.3: 21.62 ZrO.sub.2: 13.62
ZrO.sub.2: 6.81 14 La.sub.2O.sub.3: 35.35 La.sub.2O.sub.3: 17.68
Al.sub.2O.sub.3: 48.98 Al.sub.2O.sub.3: 24.49 ZrO.sub.2: 15.66
ZrO.sub.2: 7.83 15 La.sub.2O.sub.3: 32.58 La.sub.2O.sub.3: 16.2
Al.sub.2O.sub.3: 52.98 Al.sub.2O.sub.3: 26.49 ZrO.sub.2: 14.44
ZrO.sub.2: 7.22 16 La.sub.2O.sub.3: 31.20 La.sub.2O.sub.3: 15.60
Al.sub.2O.sub.3: 54.98 Al.sub.2O.sub.3: 27.49 ZrO.sub.2: 13.82
ZrO.sub.2: 6.91 17 La.sub.2O.sub.3: 28.43 La.sub.2O.sub.3: 14.22
Al.sub.2O.sub.3: 58.98 Al.sub.2O.sub.3: 29.49 ZrO.sub.2: 12.59
ZrO.sub.2: 6.30 18 La.sub.2O.sub.3: 26.67 La.sub.2O.sub.3: 13.34
Al.sub.2O.sub.3: 55.33 Al.sub.2O.sub.3: 27.67 ZrO.sub.2: 18.00
ZrO.sub.2: 9.00 19 ZrO.sub.2: 5 ZrO.sub.2: 2.5 La.sub.2O.sub.3:
86.5 La.sub.2O.sub.3: 43.25 Al.sub.2O.sub.3: 8.5 Al.sub.2O.sub.3:
4.25 20 ZrO.sub.2: 10 ZrO.sub.2: 5.00 La.sub.2O.sub.3: 81.9
La.sub.2O.sub.3: 40.95 Al.sub.2O.sub.3: 8.1 Al.sub.2O.sub.3: 4.05
21 CeO.sub.2: 41.4 CeO.sub.2: 20.7 Al.sub.2O.sub.3: 40.6
Al.sub.2O.sub.3: 20.3 ZrO.sub.2: 18 ZrO.sub.2: 9.00 22
Al.sub.2O.sub.3: 41.0 Al.sub.2O.sub.3: 20.5 ZrO.sub.2: 17.0
ZrO.sub.2: 8.5 Eu.sub.2O.sub.3: 41.0 Eu.sub.2O.sub.3: 20.5 23
Al.sub.2O.sub.3: 41.0 Al.sub.2O.sub.3: 20.5 ZrO.sub.2: 18.0
ZrO.sub.2: 9.0 Gd.sub.2O.sub.3: 41.0 Gd.sub.2O.sub.3: 20.5 24
Al.sub.2O.sub.3: 41.0 Al.sub.2O.sub.3: 20.5 ZrO.sub.2: 18.0
ZrO.sub.2: 9.0 Dy.sub.2O.sub.3: 41.0 Dy.sub.2O.sub.3: 20.5 25
Al.sub.2O.sub.3: 40.9 Al.sub.2O.sub.3: 20.45 Er.sub.2O.sub.3: 40.9
Er.sub.2O.sub.3: 20.45 ZrO.sub.2: 18.2 ZrO.sub.2: 9.1 26
La.sub.2O.sub.3: 35.0 La.sub.2O.sub.3: 17.5 Al.sub.2O.sub.3: 40.98
Al.sub.2O.sub.3: 20.49 ZrO.sub.2: 18.12 ZrO.sub.2: 9.06
Nd.sub.2O.sub.3: 5.0 Nd.sub.2O.sub.3: 2.50 27 La.sub.2O.sub.3: 35.0
La.sub.2O.sub.3: 17.5 Al.sub.2O.sub.3: 40.98 Al.sub.2O.sub.3: 20.49
ZrO.sub.2: 18.12 ZrO.sub.2: 9.06 CeO.sub.2: 5.0 CeO.sub.2: 2.50 28
La.sub.2O.sub.3: 35.0 La.sub.2O.sub.3: 17.5 Al.sub.2O.sub.3: 40.98
Al.sub.2O.sub.3: 20.49 ZrO.sub.2: 18.12 ZrO.sub.2: 9.06
Eu.sub.2O.sub.3: 5.0 Eu.sub.2O.sub.3: 2.50 29 La.sub.2O.sub.3: 35.0
La.sub.2O.sub.3: 17.5 Al.sub.2O.sub.3: 40.98 Al.sub.2O.sub.3: 20.49
ZrO.sub.2: 18.12 ZrO.sub.2: 9.06 Er.sub.2O.sub.3: 5.0
Er.sub.2O.sub.3: 2.50 30 HfO.sub.2: 35.5 HfO.sub.2: 17.75
Al.sub.2O.sub.3: 32.5 Al.sub.2O.sub.3: 16.25 La.sub.2O.sub.3: 32.5
La.sub.2O.sub.3: 16.25 31 La.sub.2O.sub.3: 41.7 La.sub.2O.sub.3:
20.85 Al.sub.2O.sub.3: 35.4 Al.sub.2O.sub.3: 17.7 ZrO.sub.2: 16.9
ZrO.sub.2: 8.45 MgO: 6.0 MgO: 3.0 32 La.sub.2O.sub.3: 39.9
La.sub.2O.sub.3: 19.95 Al.sub.2O.sub.3: 33.9 Al.sub.2O.sub.3: 16.95
ZrO.sub.2: 16.2 ZrO.sub.2: 8.10 MgO: 10.0 MgO: 5.0 33
La.sub.2O.sub.3: 43.02 La.sub.2O.sub.3: 21.51 Al.sub.2O.sub.3: 36.5
Al.sub.2O.sub.3: 18.25 ZrO.sub.2: 17.46 ZrO.sub.2: 8.73
Li.sub.2CO.sub.3: 3.0 Li.sub.2CO.sub.3: 1.50 34 La.sub.2O.sub.3:
41.7 La.sub.2O.sub.3: 20.85 Al.sub.2O.sub.3: 35.4 Al.sub.2O.sub.3:
17.70 ZrO.sub.2: 16.9 ZrO.sub.2: 8.45 Li.sub.2CO.sub.3: 6.0
Li.sub.2CO.sub.3: 3.00 35 La.sub.2O.sub.3: 38.8 La.sub.2O.sub.3:
19.4 Al.sub.2O.sub.3: 40.7 Al.sub.2O.sub.3: 20.35 ZrO.sub.2: 17.5
ZrO.sub.2: 8.75 Li.sub.2CO.sub.3: 3 Li.sub.2CO.sub.3: 1.50 36
La.sub.2O.sub.3: 43.02 La.sub.2O.sub.3: 21.51 Al.sub.2O.sub.3: 36.5
Al.sub.2O.sub.3: 18.25 ZrO.sub.2: 17.46 ZrO.sub.2: 8.73 TiO.sub.2:
3 TiO.sub.2: 1.50 37 La.sub.2O.sub.3: 43.02 La.sub.2O.sub.3: 21.51
Al.sub.2O.sub.3: 36.5 Al.sub.2O.sub.3: 18.25 ZrO.sub.2: 17.46
ZrO.sub.2: 8.73 NaHCO.sub.3: 3.0 NaHCO.sub.3: 1.50 38
La.sub.2O.sub.3: 42.36 La.sub.2O.sub.3: 21.18 Al.sub.2O.sub.3:
35.94 Al.sub.2O.sub.3: 17.97 ZrO.sub.2: 17.19 ZrO.sub.2: 8.60
NaHCO.sub.3: 4.5 NaHCO.sub.3: 2.25 39 La.sub.2O.sub.3: 43.02
La.sub.2O.sub.3: 21.51 Al.sub.2O.sub.3: 36.5 Al.sub.2O.sub.3: 18.25
ZrO.sub.2: 17.46 ZrO.sub.2: 8.73 MgO: 1.5 MgO: 0.75 NaHCO.sub.3:
1.5 NaHCO.sub.3: 0.75 TiO.sub.2: 1.5 TiO.sub.2: 0.75 40
La.sub.2O.sub.3: 43.0 La.sub.2O.sub.3: 21.50 Al.sub.2O.sub.3: 32.0
Al.sub.2O.sub.3: 16.0 ZrO.sub.2: 12 ZrO.sub.2: 6 SiO.sub.2: 13
SiO.sub.2: 65
TABLE-US-00002 TABLE 2 Raw Material Source Alumina particles
(Al.sub.2O.sub.3) Obtained from Condea Vista, Tucson, AZ under the
trade designation "APA-0.5" Calcium oxide particles (CaO) Obtained
from Alfa Aesar, Ward Hill, MA Cerium oxide particles (CeO.sub.2)
Obtained from Rhone-Poulenc, France Erbium oxide particles
(Er.sub.2O.sub.3) Obtained from Aldrich Chemical Co., Milwaukee, WI
Europium oxide particles (Eu.sub.2O.sub.3) Obtained from Aldrich
Chemical Co. Gadolinium oxide particles Obtained from Molycorp
Inc., (Gd.sub.2O.sub.3) Mountain Pass, CA Hafnium oxide particles
(HfO.sub.2) Obtained from Teledyne Wah Chang Albany Co., Albany, OR
Lanthanum oxide particles (La.sub.2O.sub.3) Obtained from Molycorp
Inc. Lithium carbonate particles Obtained from Aldrich Chemical Co.
(Li.sub.2CO.sub.3) Magnesium oxide particles (MgO) Obtained from
Aldrich Chemical Co. Neodymium oxide particles Obtained from
Molycorp Inc. (Nd.sub.2O.sub.3) Silica particles (SiO.sub.2)
Obtained from Alfa Aesar Sodium bicarbonate particles Obtained from
Aldrich Chemical Co. (NaHCO.sub.3) Titanium dioxide particles
(TiO.sub.2) Obtained from Kemira Inc., Savannah, GA
Yttria-stabilized zirconium oxide Obtained from Zirconia Sales,
Inc. of particles (Y-PSZ) Marietta, GA under the trade designation
"HSY-3" Dysprosium oxide particles (Dy.sub.2O.sub.3 Obtained from
Aldrich Chemical Co.
[0193] Various properties/characteristics of some Example 6-40
materials were measured as follows. Powder X-ray diffraction (using
an X-ray diffractometer (obtained under the trade designation
"PHILLIPS XRG 3100" from PHILLIPS, Mahwah, N.J.) with copper K (1
radiation of 1.54050 Angstrom)) was used to qualitatively measure
phases present in example materials. The presence of a broad
diffused intensity peak was taken as an indication of the glassy
nature of a material. The existence of both a broad peak and
well-defined peaks was taken as an indication of existence of
crystalline matter within a glassy matrix. Phases detected in
various examples are reported in Table 3, below.
TABLE-US-00003 TABLE 3 Phases detected via X-ray T.sub.g, T.sub.x,
Hot-pressing Example diffraction Color .degree. C. .degree. C.
temp, .degree. C. 6 Amorphous* Clear 834 932 960 7 Amorphous* Clear
837 936 960 8 Amorphous* Clear 831 935 -- 9 Amorphous* Clear 843
928 -- 10 Amorphous* Clear 848 920 960 11 Amorphous* Clear 850 923
-- 12 Amorphous* Clear 849 930 -- 13 Amorphous* Clear 843 932 -- 14
Amorphous* Clear 856 918 960 15 Amorphous* and Clear/milky 858 914
965 crystalline 16 Amorphous* and Clear/milky 859 914 --
crystalline 17 Amorphous* and Clear/milky 862 912 -- crystalline 18
Amorphous* and Clear/milky 875 908 -- crystalline 19 Crystalline
and Milky/clear -- amorphous 20 Crystalline and Milky/clear --
amorphous 21 Amorphous* and Brown 838 908 960 crystalline 22
Amorphous* Intense 874 921 975 yellow/ Mustard 23 Amorphous* Clear
886 933 985 24 Amorphous* Greenish 881 935 985 25 Amorphous*
Intense pink 885 934 26 Amorphous* Blue/pink 836 930 965 27
Amorphous* Yellow 831 934 965 28 Amorphous* Yellow/gold 838 929 --
29 Amorphous* Pink 841 932 -- 30 Amorphous* Light green 828 937 960
31 Amorphous* Clear 795 901 950 32 Amorphous* Clear 780 870 -- 33
Amorphous* Clear 816 942 950 34 Amorphous* Clear 809 934 950 35
Amorphous* Clear/ 840 922 950 greenish 36 Amorphous* Clear 836 934
950 37 Amorphous* Clear 832 943 950 38 Amorphous* Clear 830 943 950
39 Amorphous* Clear/some 818 931 950 green 40 Amorphous* Clear 837
1001 -- *glass, as the example has a T.sub.g
[0194] For differential thermal analysis (DTA), a material was
screened to retain beads in the 90-125 micrometer size range. DTA
runs were made (using an instrument obtained from Netzsch
Instruments, Selb, Germany under the trade designation "NETZSCH STA
409 DTA/TGA"). The amount of each screened sample placed in a
100-microliter Al.sub.2O.sub.3 sample holder was 400 milligrams.
Each sample was heated in static air at a rate of 10.degree.
C./minute from room temperature (about 25.degree. C.) to
1200.degree. C.
[0195] Referring to FIG. 6, line 801 is the plotted DTA data for
the Example 6 material. Referring to FIG. 6 line 801, the material
exhibited an endothermic event at temperature around 840.degree.
C., as evidenced by the downward curve of line 801. It was believed
that this event was due to the glass transition (T.sub.g) of the
material. At about 934.degree. C., an exothermic event was observed
as evidenced by the sharp peak in line 801. It was believed that
this event was due to the crystallization (T.sub.x) of the
material. These T.sub.g and T.sub.x values for other examples are
reported in Table 3, above.
[0196] The hot-pressing temperature at which appreciable glass flow
occurred, as indicated by the displacement control unit of the hot
pressing equipment described above, are reported for various
examples in Table 3, above.
Example 41
[0197] Example 41 fused material was prepared as described in
Example 5, except the polyethylene bottle was charged with 20.49
grams of alumina particles ("APA-0.5"), 20.45 grams of lanthanum
oxide particles (obtained from Molycorp, Inc.), 9.06 grams of
yttria-stabilized zirconium oxide particles (with a nominal
composition of 94.6 wt-% ZrO.sub.2 (+HfO.sub.2) and 5.4 wt-%
Y.sub.2O.sub.3; obtained under the trade designation "HSY-3" from
Zirconia Sales, Inc. of Marietta, Ga.), and 80 grams of distilled
water.
[0198] The resulting amorphous beads were placed in a polyethylene
bottle (as in Example 1) together with 200 grams of 2-mm zirconia
milling media (obtained from Tosoh Ceramics Bound Brook, N.J. under
the trade designation "YTZ"). Three hundred grams of distilled
water was added to the bottle, and the mixture milled for 24 hours
at 120 rpm to pulverize beads into powder. The milled material was
dried using a heat gun. Fifteen grams of the dried particles were
placed in a graphite die and hot-pressed at 960.degree. C. as
described in Example 6. The resulting disk was translucent.
Example 42
[0199] Example 42 fused amorphous beads were prepared as described
in Example 5. About 15 grams of the beads were hot pressed as
described in Example 5 except the bottom punch of the graphite die
had 2 mm deep grooves. The resulting material replicated the
grooves, indicating very good flowability of the glass during the
heating under the applied pressure.
Comparative Example B
[0200] Comparative Example B fused material was prepared as
described in Example 5, except the polyethylene bottle was charged
with 27 grams of alumina particles ("APA-0.5"), 23 grams of
yttria-stabilized zirconium oxide particles (with a nominal
composition of 94.6 wt-% ZrO.sub.2 (+HfO.sub.2) and 5.4 wt-%
Y.sub.2O.sub.3; obtained under the trade designation "HSY-3" from
Zirconia Sales, Inc. of Marietta, Ga.) and 80 grams of distilled
water. The m composition of this example corresponds to a eutectic
composition in the Al.sub.2O.sub.3--ZrO.sub.2 binary system. The
resulting 100-150 micrometers diameter spheres were partially
amorphous, with significant portions of crystallinity as evidenced
by X-ray diffraction analysis.
Example 43
[0201] A sample (31.25 grams) of amorphous beads prepared as
described in Example 6, and 18.75 grams of beads prepared as
described in Comparative Example B, were placed in a polyethylene
bottle. After 80 grams of distilled water and 300 grams of zirconia
milling media (Tosoh Ceramics, Bound Brook, N.J. under the trade
designation "YTZ") were added to the bottle, the mixture was milled
for 24 hours at 120 rpm. The milled material was dried using a heat
gun. Twenty grams of the dried particles were hot-pressed as
described in Example 6. An SEM photomicrograph of a polished
section (prepared as described in Example 6) of Example 43 material
is shown in FIG. 7. The absence of cracking at interfaces between
the Comparative Example B material (dark areas) and the Example 6
material (light areas) indicates the establishment of good
bonding.
Examples 44-48
[0202] Examples 44-48 were prepared, including hot-pressing, as
described in Example 43, except various additives (see Table 4,
below) were used instead of the beads of Comparative Example B. The
sources of the raw materials used are listed in Table 5, below.
TABLE-US-00004 TABLE 4 Example Additive Batch, g 44
.alpha.-Al.sub.2O.sub.3 LAZ (see Ex. 6), 35
.alpha.--Al.sub.2O.sub.3, 15 45 PSZ (ZrO.sub.2) LAZ (see Ex. 6), 35
PSZ, 15 46 Si.sub.3N.sub.4 LAZ (see Ex. 6), 35 Si.sub.3N.sub.4, 5
47 Diamond (30 LAZ (see Ex. 6), 35 micrometers) Diamond, 15 48
Al.sub.2O.sub.3 abrasive LAZ (see Ex. 6), 35 Microparticles
Al.sub.2O.sub.3 abrasive Microparticles, 15
TABLE-US-00005 TABLE 5 Raw Material Source Alumina particles
(alpha-Al.sub.2O.sub.3) Obtained from Condea Vista, Tucson, AZ
under the trade designation "APA-0.5" Yttria-stabilized zirconium
Obtained from Zirconia Sales, Inc. of oxide particles (Y-PSZ)
Marietta, GA under the trade designation "HSY-3" Silicon nitride
particles (Si.sub.3N.sub.4) Obtained from UBE Industries, Japan
under the trade designation "E-10" Diamond microparticles Obtained
from the 3M Company, (30 micrometers) St. Paul Al.sub.2O.sub.3
abrasive microparticles Obtained from the 3M Company under (50
micrometers) the designation "321 CUBITRON"
[0203] The resulting hot-pressed materials of Examples 44-48 were
observed to be strong composite materials as determined by visual
observation and handling. FIG. 8 is an SEM micrograph of a polished
cross-section of Example 47 demonstrating good bonding between
diamond and the glass.
Examples 49-53
[0204] Examples 49-53 were prepared by heat-treating 15 gram
batches of Example 6 beads in air at temperatures ranging from
1000.degree. C. to 1300.degree. C. for 60 minutes. Heat-treating
was performed in an electrically heated furnace (obtained under the
trade designation "Model KKSK-666-3100" from Keith Furnaces of Pico
Rivera, Calif.). The resulting heat-treated materials were analyzed
using powder X-ray diffraction as described above for Examples
6-40. The results are summarized in Table 6, below.
[0205] The average microhardnesses of Examples 49-53 beads (about
125 micrometers in size) were measured as described in Example
6.
TABLE-US-00006 TABLE 6 Heat- treatment temperature, Phases detected
via Hardness, Example .degree. C. X-ray diffraction Color GPa 49
900 Amorphous Clear 7.5 .+-. 0.3 50 1000 LaAlO.sub.3;
La.sub.2Zr.sub.2O.sub.7 Clear/milky 8.4 .+-. 0.2 51 1100
LaAlO.sub.3; La.sub.2Zr.sub.2O.sub.7; Clear/milky 10.3 .+-. 0.2
Cubic/tetragonal ZrO.sub.2 52 1200 LaAlO.sub.3; Clear/milky 11.8
.+-. 0.2 Cubic/tetragonal ZrO.sub.2; LaAl.sub.11O.sub.18 53 1300
LaAlO.sub.3; Opaque 15.7 .+-. 0.4 Cubic/tetragonal ZrO.sub.2;
LaAl.sub.11O.sub.18
Grinding Performance of Examples 6 and 6A and Comparative Examples
C-E
[0206] Example 6 hot-pressed material was crushed by using a
"Chipmunk" jaw crusher (Type VD, manufactured by BICO Inc.,
Burbank, Calif.) into (abrasive) particles and graded to retain the
-25+30 mesh fraction (i.e., the fraction collected between
25-micrometer opening and 30-micrometer opening size sieves) and
-30+35 mesh fractions (i.e., the fraction collected between
30-micrometer opening size and 35-micrometer opening size sieves)
(USA Standard Testing Sieves). These two mesh fractions were
combined to provide a 50/50 blend. The blended material was heat
treated as described in Example 6. Thirty grams of the resulting
glass-ceramic abrasive particles were incorporated into a coated
abrasive disc. The coated abrasive disc was made according to
conventional procedures. The glass-ceramic abrasive particles were
bonded to 17.8 cm diameter, 0.8 mm thick vulcanized fiber backings
(having a 2.2 cm diameter center hole) using a conventional calcium
carbonate-filled phenolic make resin (48% resole phenolic resin,
52% calcium carbonate, diluted to 81% solids with water and glycol
ether) and a conventional cryolite-filled phenolic size resin (32%
resole phenolic resin, 2% iron oxide, 66% cryolite, diluted to 78%
solids with water and glycol ether). The wet make resin weight was
about 185 g/m.sup.2 Immediately after the make coat was applied,
the glass-ceramic abrasive particles were electrostatically coated.
The make resin was precured for 120 minutes at 88.degree. C. Then
the cryolite-filled phenolic size coat was coated over the make
coat and abrasive particles. The wet size weight was about 850
g/m.sup.2. The size resin was cured for 12 hours at 99.degree. C.
The coated abrasive disc was flexed prior to testing.
[0207] Example 6A coated abrasive disk was prepared as described
for Example 6 except the Example 6A abrasive particles were
obtained by crushing a hot-pressed and heat-treated Example 6
material, rather than crushing then heat-treating.
[0208] Comparative Example C coated abrasive discs were prepared as
described for Example 6 (above), except heat-treated fused alumina
abrasive particles (obtained under the trade designation "ALODUR
BFRPL" from Triebacher, Villach, Austria) was used in place of the
Example 6 glass-ceramic abrasive particles.
[0209] Comparative Example D coated abrasive discs were prepared as
described for Example 6 (above), except alumina-zirconia abrasive
particles (having a eutectic composition of 53% Al.sub.2O.sub.3 and
47% ZrO.sub.2; obtained under the trade designation "NORZON" from
Norton Company, Worcester, Mass.) were used in place of the Example
6 glass-ceramic abrasive particles.
[0210] Comparative Example E coated abrasive discs were prepared as
described above except sol-gel-derived abrasive particles (marketed
under the trade designation "321 CUBITRON" from the 3M Company, St.
Paul, Minn.) was used in place of the Example 6 glass-ceramic
abrasive particles.
[0211] The grinding performance of Example 6 and Comparative
Examples C-E coated abrasive discs were evaluated as follows. Each
coated abrasive disc was mounted on a beveled aluminum back-up pad,
and used to grind the face of a pre-weighed 1.25 cm.times.18
cm.times.10 cm 1018 mild steel workpiece. The disc was driven at
5,000 rpm while the portion of the disc overlaying the beveled edge
of the back-up pad contacted the workpiece at a load of 8.6
kilograms. Each disc was used to grind an individual workpiece in
sequence for one-minute intervals. The total cut was the sum of the
amount of material removed from the workpieces throughout the test
period. The total cut by each sample after 12 minutes of grinding
as well as the cut at the 12th minute (i.e., the final cut) are
reported in Table 6, below. The Example 6 results are an average of
two discs, where as one disk was tested for each of Example 6A, and
Comparative Examples C, D, and E.
TABLE-US-00007 TABLE 6 Example Total cut, g Final cut, g 6 1163 92
6A 1197 92 Comp. C 514 28 Comp. D 689 53 Comp. E 1067 89
[0212] Various modifications and alterations of this disclosure
will become apparent to those skilled in the art without departing
from the scope and spirit of this disclosure, and it should be
understood that this disclosure is not to be unduly limited to the
illustrative embodiments set forth herein.
* * * * *