U.S. patent application number 12/323774 was filed with the patent office on 2009-03-19 for method and article from aluminum oxide glass and articles made therefrom.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Anatoly Z. Rosenflanz.
Application Number | 20090075807 12/323774 |
Document ID | / |
Family ID | 40294050 |
Filed Date | 2009-03-19 |
United States Patent
Application |
20090075807 |
Kind Code |
A1 |
Rosenflanz; Anatoly Z. |
March 19, 2009 |
METHOD AND ARTICLE FROM ALUMINUM OXIDE GLASS AND ARTICLES MADE
THEREFROM
Abstract
A method of making an article from an aluminum oxide glass is
disclosed. The aluminum oxide glass includes a rare earth oxide.
The aluminum oxide glass has a glass transition temperature and a
crystallization temperature, and these temperatures differ by at
least 25K. The method includes: providing a glass in a form
comprising particles, beads, microspheres, or fibers; heating the
glass above the T.sub.g such that the particles, beads,
microspheres, or fibers coalesce to form a coalesced shape; and
cooling the coalesced shape to form the article.
Inventors: |
Rosenflanz; Anatoly Z.;
(Maplewood, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
40294050 |
Appl. No.: |
12/323774 |
Filed: |
November 26, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10211491 |
Aug 2, 2002 |
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12323774 |
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09922526 |
Aug 2, 2001 |
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10211491 |
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Current U.S.
Class: |
501/77 ; 501/73;
65/36 |
Current CPC
Class: |
C03B 19/063 20130101;
C03B 19/01 20130101; C03B 19/102 20130101 |
Class at
Publication: |
501/77 ; 65/36;
501/73 |
International
Class: |
C03C 3/064 20060101
C03C003/064; C03B 23/00 20060101 C03B023/00; C03C 3/062 20060101
C03C003/062 |
Claims
1. A method of making an article, comprising: providing a glass in
a form comprising particles, beads, microspheres, or fibers; the
glass comprising: REO-Al.sub.2O.sub.3; 0 to less than 20% by weight
SiO.sub.2; 0 to less than 20% by weight B.sub.2O.sub.3; and 0 to
less than 40% by weight P.sub.2O.sub.5; the glass having a glass
transition temperature, T.sub.g, and a crystallization onset
temperature, T.sub.x, and the difference between T.sub.g and
T.sub.x is at least 25K; heating the glass above the T.sub.g such
that the particles, beads, microspheres, or fibers coalesce to form
a coalesced shape; and cooling the coalesced shape to form the
article.
2. The method of claim 1, the glass further comprising an
additional metal oxide selected from the group consisting of BaO,
CaO, Cr.sub.2O.sub.3, CoO, Fe.sub.2O.sub.3, GeO.sub.2, HfO.sub.2,
Li.sub.2O, MgO, MnO, NiO, Na.sub.2O, Sc.sub.2O.sub.3, SrO,
TeO.sub.2, TiO.sub.2, V.sub.2O.sub.3, Y.sub.2O.sub.3, ZnO, and
combinations thereof.
3. The method of claim 1, the glass further comprising
Y.sub.2O.sub.3.
4. The method of claim 1, the glass further comprising
TiO.sub.2.
5. The method of claim 1, the glass further comprising
HfO.sub.2.
6. The method of claim 1, the difference between T.sub.g and
T.sub.x being at least 35K.
7. The method of claim 1, the glass collectively comprising less
than 40% by weight of SiO.sub.2, B.sub.2O.sub.3, and
P.sub.2O.sub.5.
8. The method of claim 1, the glass collectively comprising less
than 10% by weight of SiO.sub.2, B.sub.2O.sub.3, and
P.sub.2O.sub.5.
9. The method of claim 1, the glass collectively comprising less
than 5% by weight of SiO.sub.2, B.sub.2O.sub.3, and
P.sub.2O.sub.5.
10. The method of claim 1, the glass collectively comprising at
least 80% by weight of REO-Al.sub.2O.sub.3.
11. An article prepared according to the method of claim 1.
12. A method of making an article, comprising: providing a glass in
a form comprising particles, beads, microspheres, or fibers; the
glass comprising: REO-Al.sub.2O.sub.3--ZrO.sub.2; 0 to less than
20% by weight SiO.sub.2; 0 to less than 20% by weight
B.sub.2O.sub.3; and 0 to less than 40% by weight P.sub.2O.sub.5;
the glass having a glass transition temperature, T.sub.g, and a
crystallization onset temperature, T.sub.x, and the difference
between T.sub.g and T.sub.x is at least 25K; heating the glass
above the T.sub.g such that the particles, beads, microspheres, or
fibers coalesce to form a coalesced shape; and cooling the
coalesced shape to form the article.
13. The method of claim 12, the glass further comprising an
additional metal oxide selected from the group consisting of BaO,
CaO, Cr.sub.2O.sub.3, CoO, Fe.sub.2O.sub.3, GeO.sub.2, HfO.sub.2,
Li.sub.2O, MgO, MnO, NiO, Na.sub.2O, Sc.sub.2O.sub.3, SrO,
TeO.sub.2, TiO.sub.2, V.sub.2O.sub.3, Y.sub.2O.sub.3, ZnO, and
combinations thereof.
14. The method of claim 12, the glass further comprising
Y.sub.2O.sub.3.
15. The method of claim 12, the glass further comprising
TiO.sub.2.
16. The method of claim 12, the glass further comprising
HfO.sub.2.
17. The method of claim 12, the difference between T.sub.g and
T.sub.x being at least 35K.
18. The method of claim 12, the glass collectively comprising less
than 40% by weight of SiO.sub.2, B.sub.2O.sub.3, and
P.sub.2O.sub.5.
19. The method of claim 12, the glass collectively comprising less
than 10% by weight of SiO.sub.2, B.sub.2O.sub.3, and
P.sub.2O.sub.5.
20. The method of claim 12, the glass collectively comprising less
than 5% by weight of SiO.sub.2, B.sub.2O.sub.3, and
P.sub.2O.sub.5.
21. The method of claim 12, the glass collectively comprising at
least 80% by weight of REO-Al.sub.2O.sub.3--ZrO.sub.2.
22. An article prepared according to the method of claim 12.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Ser. No.
10/211,491, filed Aug. 2, 2002, which is a continuation-in-part of
U.S. Ser. No. 09/922,526, filed Aug. 2, 2001, now abandoned. This
application is related to U.S. 2007/0135290 A1 filed Jan. 15, 2007.
This application is also related to U.S. Ser. No. ______ (Attorney
Docket No. 56938US018) and U.S. Ser. No. ______ (Attorney Docket
No. 56938US019) filed on even date herewith.
FIELD OF THE INVENTION
[0002] The present invention relates to a method of making an
article by coalescing a plurality of the glass particles. Examples
of articles include kitchenware (e.g., plates), dental brackets,
and reinforcing fibers, cutting tool inserts, abrasives, and
structural components of gas engines, (e.g., valves and
bearings).
DESCRIPTION OF RELATED ART
[0003] A large number of 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] Although a large number of metal oxides can be obtained in
an amorphous state by melting and rapidly quenching, most, because
of the need for very high quench rates to provide amorphous rather
than crystalline material, cannot be formed into bulk or complex
shapes. Generally, such systems are very unstable against
crystallization during subsequent reheating and therefore do not
exhibit typical properties of glass such as viscous flow. On the
other hand, glasses based on the known network forming oxides
(e.g., SiO.sub.2 and B.sub.2O.sub.3) are generally relatively
stable against crystallization during reheating and,
correspondingly, the "working" range where viscous flow occurs can
be readily accessed. Formation of large articles from powders of
known glass (e.g., SiO.sub.2 and B.sub.2O.sub.3) via viscous
sintering at temperatures above glass transition temperature is
well known. For example, in the abrasive industry, grinding wheels
are made using vitrified bond to secure the abrasive particles
together.
[0005] It is desirable to provide large articles and/or complex
shapes comprising non-traditional glass and glass-ceramics
compositions.
SUMMARY OF THE INVENTION
[0006] The present invention provides a method of making articles
from glass. Optionally, the articles may be a composite of two or
more different glass compositions or formulations. In some
embodiments the glass is optionally heat-treated to at least
partially crystallize the glass.
[0007] One embodiment of the present invention provides a method of
making an article from glass comprising: [0008] providing a
substrate (e.g., ceramics, metals, intermetallics, and composites
thereof) including an outer surface; [0009] providing at least a
first glass (e.g., sheets, particles (including microspheres), and
fibers), wherein the first glass comprises at least two different
metal oxides (i.e., the metal oxides do not have the same
cation(s)), wherein the first glass has a T.sub.g and T.sub.x, and
wherein the difference between the T.sub.g and the T.sub.x of the
first glass is at least 5K (or even, at least 10K, at least 15K, at
least 20K, at least 25K, at least 30K, or at least 35K), the first
glass containing less than 20% by weight SiO.sub.2 (or even less
than 15%, less than 10%, less than 5% by weight, or even zero
percent, by weight, SiO.sub.2), less than 20% by weight
B.sub.2O.sub.3 (or even less than 15%, less than 10%, less than 5%
by weight, or even zero percent, by weight, B.sub.2O.sub.3), and
less than 40% by weight P.sub.2O.sub.5 (or even less than 35%, less
than 30%, less than 25%, less than 20%, less than 15%, less than
1%, less than 5% by weight, or even zero percent, by weight,
P.sub.2O.sub.5); [0010] heating the first glass above the T.sub.g
such that at least a portion of the glass wets at least a portion
of the outer surface of the substrate; and [0011] cooling the glass
to provide an article comprising ceramic comprising the glass
attached to the at least a portion of the outer surface of the
substrate. In some embodiments, the ceramic is glass. Optionally,
the method can be practiced with a second, a third, or more,
different glass, including glasses having, respectively, a T.sub.g
and T.sub.x, and wherein the difference between each T.sub.g and
the T.sub.x of a glass is at least 5K (or even, at least 10K, at
least 15K, at least 20K, at least 25K, at least 30K, or at least
35K), one or more of the additional glasses optionally contain less
than 20% by weight SiO.sub.2 (or even less than 15%, less than 10%,
less than 5% by weight, or even zero percent, by weight,
SiO.sub.2), less than 20% by weight B.sub.2O.sub.3 (or even less
than 15%, less than 10%, less than 5% by weight, or even zero
percent, by weight, B.sub.2O.sub.3), and less than 40% by weight
P.sub.2O.sub.5 (or even less than 35%, less than 30%, less than
25%, less than 20%, less than 15%, less than 1%, less than 5% by
weight, or even zero percent, by weight, P.sub.2O.sub.5).
Preferably the glass, or if more than one glass is used, at least
one of the glasses, comprises less than 40 percent (preferably,
less than 35, 30, 25, 20, 15, 10, 5, or even 0) by weight glass
collectively SiO.sub.2, B.sub.2O.sub.3, and P.sub.2O.sub.5, based
on the total weight of the glass.
[0012] Another embodiment of the present invention provides a
method of making an article from glass comprising: [0013] providing
a substrate including an outer surface; [0014] providing at least a
first plurality of particles comprising glass (including glass
particles), wherein the glass comprises at least two different
metal oxides, wherein the glass has a T.sub.g and T.sub.x, and
wherein the difference between the T.sub.g and the T.sub.x of the
glass is at least 5K (or even, at least 10K, at least 15K, at least
20K, at least 25K, at least 30K, or at least 35K), the glass
containing less than 20% by weight SiO.sub.2 (or even less than
15%, less than 10%, less than 5% by weight, or even zero percent,
by weight, SiO.sub.2), less than 20% by weight B.sub.2O.sub.3 (or
even less than 15%, less than 10%, less than 5% by weight, or even
zero percent, by weight, B.sub.2O.sub.3), and less than 40% by
weight P.sub.2O.sub.5 (or even less than 35%, less than 30%, less
than 25%, less than 20%, less than 15%, less than 1%, less than 5%
by weight, or even zero percent, by weight, P.sub.2O.sub.5); [0015]
heating the glass above the T.sub.g such that at least a portion of
the glass of the first plurality of particles wets at least a
portion of the outer surface of the substrate; and [0016] cooling
the glass to provide an article comprising ceramic comprising the
glass attached to the at least a portion of the outer surface of
the substrate. In some embodiments, the ceramic is glass.
Optionally, the method can be practiced with a second, a third, or
more, different pluralities of particles comprising (different)
glasses, including glasses having, respectively, a T.sub.g and
T.sub.x, and wherein the difference between each T.sub.g and the
T.sub.x of a glass is at least 5K (or even, at least 10K, at least
15K, at least 20K, at least 25K, at least 30K, or at least 35K),
one or more of the additional glasses optionally contain less than
20% by weight SiO.sub.2 (or even less than 15%, less than 10%, less
than 5% by weight, or even zero percent, by weight, SiO.sub.2),
less than 20% by weight B.sub.2O.sub.3 (or even less than 15%, less
than 10%, less than 5% by weight, or even zero percent, by weight,
B.sub.2O.sub.3), and less than 40% by weight P.sub.2O.sub.5 (or
even less than 35%, less than 30%, less than 25%, less than 20%,
less than 15%, less than 1%, less than 5% by weight, or even zero
percent, by weight, P.sub.2O.sub.5). Preferably the glass, or if
more than one glass is used, at least one of the glasses, comprises
less than 40 (preferably, less than 35, 30, 25, 20, 15, 10, 5, or
even 0) percent by weight glass collectively SiO.sub.2,
B.sub.2O.sub.3, and P.sub.2O.sub.5, based on the total weight of
the glass.
[0017] Another embodiment of the present invention provides a
method of making an article comprising: [0018] providing at least a
first glass and second glass (e.g., sheets, particles (including
microspheres), and fibers), wherein the first glass comprises at
least two different metal oxides, wherein the first glass has a
T.sub.g1 and T.sub.x1, and wherein the difference between the
T.sub.g1 and the T.sub.x1 is at least 5K (or even, at least 10K, at
least 15K, at least 20K, at least 25K, at least 30K, or at least
35K), the first glass containing less than 20% by weight SiO.sub.2
(or even less than 15%, less than 10%, less than 5% by weight, or
even zero percent, by weight, SiO.sub.2), less than 20% by weight
B.sub.2O.sub.3 (or even less than 15%, less than 10%, less than 5%
by weight, or even zero percent, by weight, B.sub.2O.sub.3), and
less than 40% by weight P.sub.2O.sub.5 (or even less than 35%, less
than 30%, less than 25%, less than 20%, less than 15%, less than
1%, less than 5% by weight, or even zero percent, by weight,
P.sub.2O.sub.5); [0019] heating the first and second glasses above
at least T.sub.g1 and at least the first glass coalescing with the
second glass to provide the article. Optionally, the second glass
has a T.sub.g2 and T.sub.x2, wherein the difference between
T.sub.g2 and T.sub.x2 is at least 5K (or even, at least 10K, at
least 15K, at least 20K, at least 25K, at least 30K, or at least
35K). Optionally, the second glass contains less than 20% by weight
SiO.sub.2 (or even less than 15%, less than 10%, less than 5% by
weight, or even zero percent, by weight, SiO.sub.2), less than 20%
by weight B.sub.2O.sub.3 (or even less than 15%, less than 10%,
less than 5% by weight, or even zero percent, by weight,
B.sub.2O.sub.3), and less than 40% by weight P.sub.2O.sub.5 (or
even less than 35%, less than 30%, less than 25%, less than 20%,
less than 15%, less than 1%, less than 5% by weight, or even zero
percent, by weight, P.sub.2O.sub.5). Optionally, the method can be
practiced with a third, a fourth, glass, etc. including glasses
having, respectively, a T.sub.g and T.sub.x, and wherein the
difference between each T.sub.g and the T.sub.x of a glass is at
least 5K (or even, at least 10K, at least 15K, at least 20K, at
least 25K, at least 30K, or at least 35K), one or more of the
additional glasses optionally contain less than 20% by weight
SiO.sub.2 (or even less than 15%, less than 10%, less than 5% by
weight, or even zero percent, by weight, SiO.sub.2), less than 20%
by weight B.sub.2O.sub.3 (or even less than 15%, less than 10%,
less than 5% by weight, or even zero percent, by weight,
B.sub.2O.sub.3), and less than 40% by weight P.sub.2O.sub.5 (or
even less than 35%, less than 30%, less than 25%, less than 20%,
less than 15%, less than 1%, less than 5% by weight, or even zero
percent, by weight, P.sub.2O.sub.5). The glasses may have the same
composition, different composition, or combinations thereof.
Preferably at least one of the glasses comprise less than 40
(preferably, less than 35, 30, 25, 20, 15, 10, 5, or even 0)
percent by weight glass collectively SiO.sub.2, B.sub.2O.sub.3, and
P.sub.2O.sub.5, based on the total weight of the glass.
[0020] Another embodiment of the present invention provides a
method of making an article comprising: [0021] providing at least a
first glass and second glass (e.g., sheets, particles (including
microspheres), and fibers), wherein the first glass comprises at
least two different metal oxides, wherein the first glass has a
T.sub.g1 and T.sub.x1, and wherein the difference between the
T.sub.g1 and the T.sub.x1 is at least 5K (or even, at least 10K, at
least 15K, at least 20K, at least 25K, at least 30K, or at least
35K), the first glass containing less than 20% by weight SiO.sub.2
(or even less than 15%, less than 10%, less than 5% by weight, or
even zero percent, by weight, SiO.sub.2), less than 20% by weight
B.sub.2O.sub.3 (or even less than 15%, less than 10%, less than 5%
by weight, or even zero percent, by weight, B.sub.2O.sub.3), and
less than 40% by weight P.sub.2O.sub.5 (or even less than 35%, less
than 30%, less than 25%, less than 20%, less than 15%, less than
1%, less than 5% by weight, or even zero percent, by weight,
P.sub.2O.sub.5), and wherein the second glass comprises at least
two different metal oxides, wherein the second glass has a T.sub.g2
and T.sub.x2, and wherein the difference between the T.sub.g2 and
the T.sub.x2 is at least 5K (or even, at least 10K, at least 15K,
at least 20K, at least 25K, at least 30K, or at least 35K), the
second glass containing less than 20% by weight SiO.sub.2 (or even
less than 15%, less than 10%, less than 5% by weight, or even zero
percent, by weight, SiO.sub.2), less than 20% by weight
B.sub.2O.sub.3 (or even less than 15%, less than 10%, less than 5%
by weight, or even zero percent, by weight, B.sub.2O.sub.3), and
less than 40% by weight P.sub.2O.sub.5 (or even less than 35%, less
than 30%, less than 25%, less than 20%, less than 15%, less than
1%, less than 5% by weight, or even zero percent, by weight,
P.sub.2O.sub.5); [0022] heating the glasses above the higher of
T.sub.g1 or T.sub.g2 and coalescing the first and second glasses to
provide the article. Optionally, the method can be practices with a
third, a fourth, glass, etc. including glasses having,
respectively, a T.sub.g and T.sub.x, and wherein the difference
between each T.sub.g and the T.sub.x of a glass is at least 5K (or
even, at least 10K, at least 15K, at least 20K, at least 25K, at
least 30K, or at least 35K), one or more of the additional glasses
optionally contain less than 20% by weight SiO.sub.2 (or even less
than 15%, less than 10%, less than 5% by weight, or even zero
percent, by weight, SiO.sub.2), less than 20% by weight
B.sub.2O.sub.3 (or even less than 15%, less than 10%, less than 5%
by weight, or even zero percent, by weight, B.sub.2O.sub.3), and
less than 40% by weight P.sub.2O.sub.5 (or even less than 35%, less
than 30%, less than 25%, less than 20%, less than 15%, less than
1%, less than 5% by weight, or even zero percent, by weight,
P.sub.2O.sub.5). The glasses may have the same composition,
different composition, or combinations thereof. Preferably at least
one of the glasses comprise less than 40 (preferably, less than 35,
30, 25, 20, 15, 10, 5, or even 0) percent by weight glass
collectively SiO.sub.2, B.sub.2O.sub.3, and P.sub.2O.sub.5, based
on the total weight of the glass.
[0023] Another embodiment of the present invention provides a
method of making an article comprising: [0024] providing at least a
first plurality of particles comprising glass (including glass
particles), wherein the glass comprises at least two different
metal oxides, wherein the glass has a T.sub.g and T.sub.x, and
wherein the difference between the T.sub.g and the T.sub.x of the
glass is at least 5K (or even, at least 10K, at least 15K, at least
20K, at least 25K, at least 30K, or at least 35K), the glass
containing less than 20% by weight SiO.sub.2 (or even less than
15%, less than 10%, less than 5% by weight, or even zero percent,
by weight, SiO.sub.2), less than 20% by weight B.sub.2O.sub.3 (or
even less than 15%, less than 10%, less than 5% by weight, or even
zero percent, by weight, B.sub.2O.sub.3), and less than 40% by
weight P.sub.2O.sub.5 (or even less than 35%, less than 30%, less
than 25%, less than 20%, less than 15%, less than 1%, less than 5%
by weight, or even zero percent, by weight, P.sub.2O.sub.5); [0025]
heating the glass above the T.sub.g and coalescing at least a
portion of the first plurality of particles to provide the article.
In some embodiments, the ceramic is glass. Optionally, the method
can be practiced with a second, a third, or more, different
pluralities of particles comprising (different) glasses, including
glasses having, respectively, a T.sub.g and T.sub.x, and wherein
the difference between each T.sub.g and the T.sub.x of a glass is
at least 5K (or even, at least 10K, at least 15K, at least 20K, at
least 25K, at least 30K, or at least 35K), one or more of the
additional glasses optionally contain less than 20% by weight
SiO.sub.2 (or even less than 15%, less than 10%, less than 5% by
weight, or even zero percent, by weight, SiO.sub.2), less than 20%
by weight B.sub.2O.sub.3 (or even less than 15%, less than 10%,
less than 5% by weight, or even zero percent, by weight,
B.sub.2O.sub.3), and less than 40% by weight P.sub.2O.sub.5 (or
even less than 35%, less than 30%, less than 25%, less than 20%,
less than 15%, less than 1%, less than 5% by weight, or even zero
percent, by weight, P.sub.2O.sub.5). Preferably the glass, or if
more than one glass is used, at least one of the glasses, comprises
less than 40 (preferably, less than 35, 30, 25, 20, 15, 10, 5, or
even 0) percent by weight glass collectively SiO.sub.2,
B.sub.2O.sub.3, and P.sub.2O.sub.5, based on the total weight of
the glass.
[0026] Desirably, the ratio of a T.sub.g to T.sub.1 is at least
0.5. Examples of useful glass particles include those comprising
REO-Al.sub.2O.sub.3--ZrO.sub.2 and
REO-Al.sub.2O.sub.3--ZrO.sub.2--SiO.sub.2 glasses. Other useful
glasses may also include CaO--Al.sub.2O.sub.3,
CaO--Al.sub.2O.sub.3--ZrO.sub.2, BaO--TiO.sub.2,
La.sub.2O.sub.3--TiO.sub.2, REO (i.e., rare earth
oxide(s))-Al.sub.2O.sub.3 glasses.
[0027] Embodiments of the method according to the present
invention, including for certain ceramic compositions, allow for
the formation of article shapes and sizes that were obtainable from
conventional methods. Coalescence of the glass is typically
enhanced if the glass is under pressure during heating. In one
embodiment, a charge of glass (e.g., particles (including beads),
fibers, 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 an article.
[0028] In this application:
[0029] "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";
[0030] "ceramic" includes amorphous material, glass, crystalline
ceramic, glass-ceramic, and combinations thereof;
[0031] "glass" refers to amorphous material exhibiting a glass
transition temperature;
[0032] "glass-ceramic" refers to ceramic comprising crystals formed
by heat-treating amorphous material;
[0033] "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;
[0034] "REO" refers to rare earth oxide(s);
[0035] "T.sub.g" refers to the glass transition temperature as
determined in Example 1;
[0036] "T.sub.1" refers to the glass melting point; and
[0037] "T.sub.x" refers to crystallization onset temperature as
determined in Example 1.
[0038] 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. 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.
[0039] Optionally certain glass articles made according to the
present invention can be heat-treated at least partially
crystallize the glass to provide glass-ceramic.
BRIEF DESCRIPTION OF THE DRAWING
[0040] FIG. 1 is a DTA curve of Example 1 material; and
[0041] FIGS. 2-6 are DTA curves of Examples 2, 5, 6, 7, and 9
materials, respectively.
DETAILED DESCRIPTION
[0042] The following disclosures are incorporated herein by
reference: U.S. Ser. No. 10/211,491, filed Aug. 2, 2002; U.S. Ser.
No. 09/922,526, filed Aug. 2, 2001; U.S. 2007/0135290 A1, filed
Jan. 15, 2007; U.S. Ser. No. ______ (Attorney Docket No.
56938US018), filed on this same day; and U.S. Ser. No. ______
(Attorney Docket No. 56938US019), filed on this same day.
[0043] In general, ceramics according to the present invention 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 invention
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. 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)).
[0044] 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). 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.
[0045] In one method, glass useful for the present invention 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 determines the size of the resulting
glass particles/beads.
[0046] Examples of useful glass for carrying out the present
invention include those comprising CaO--Al.sub.2O.sub.3,
CaO--Al.sub.2O.sub.3--ZrO.sub.2, BaO--TiO.sub.2,
La.sub.2O.sub.3--TiO.sub.2, REO-Al.sub.2O.sub.3,
REO-Al.sub.2O.sub.3--ZrO.sub.2,
REO-Al.sub.2O.sub.3--ZrO.sub.2--SiO.sub.2, and
SrO--Al.sub.2O.sub.3--ZrO.sub.2 glasses. Useful glass formulations
include those at or near a eutectic composition. In addition to the
CaO--Al.sub.2O.sub.3, CaO--Al.sub.2O.sub.3--ZrO.sub.2,
BaO--TiO.sub.2, La.sub.2O.sub.3--TiO.sub.2, REO-Al.sub.2O.sub.3,
REO-Al.sub.2O.sub.3--ZrO.sub.2,
REO-Al.sub.2O.sub.3--ZrO.sub.2--SiO.sub.2, and
SrO--Al.sub.2O.sub.3--ZrO.sub.2 compositions disclosed herein,
other compositions, including eutectic compositions, will be
apparent to those skilled in the art after reviewing the present
disclosure. For example, phase diagrams depicting various
compositions, including eutectic compositions, are known in the
art.
[0047] Surprisingly, it was found that ceramics of present
invention could be obtained without limitations in dimensions. This
was found to be possible through a coalescence step performed at
temperatures above glass transition temperature. For instance, as
evident from FIG. 1, glass useful in carry out the present
invention 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).
This allows for bulk fabrication of articles of any dimensions from
relatively small pieces of glass. More specifically, for example,
an article according to the present invention, can be provided by
heating, for example, glass particles (including beads and
microspheres), fibers, etc. useful in carrying out the present
invention above the T.sub.g such that the glass particles, etc.
coalesce to form a shape and cooling the coalesced shape to provide
the article. In certain embodiments, heating is conducted at least
one temperature in a range of about 725.degree. C. to about
1100.degree. C.
[0048] Surprisingly, for certain embodiments according to the
present invention, coalescence may be conducted at temperatures
significantly higher than crystallization temperature (T.sub.x).
Although not wanting to be bound by theory, it s is believed the
relatively slow kinetics of crystallization allow access to higher
temperatures for viscous flow. Typically, the glass is under
pressure during coalescence to aid the coalescence of the glass. In
one embodiment, a charge of the glass 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. 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. It is
also within the scope of the present invention to conduct
additional coalescence to further improve desirable properties of
the article. 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. It is also within the scope of the present
invention to coalesce glass via hot-isostatic pressing, hot
extrusion, or other pressure assisted techniques.
[0049] 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 invention 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 invention 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.
[0050] Sources, including commercial sources, of metal oxides such
as Al.sub.2O.sub.3, BaO, CaO, rare earth oxides (e.g., CeO.sub.2,
Dy.sub.2O.sub.3, Er.sub.2O.sub.3, Eu.sub.2O.sub.3, Gd.sub.2O.sub.3,
Ho.sub.2O.sub.3, La.sub.2O.sub.3, Lu.sub.2O.sub.3, Nd.sub.2O.sub.3,
Pr.sub.6O.sub.11, Sm.sub.2O.sub.3, Th.sub.4O.sub.7,
Tm.sub.2O.sub.3, and Yb.sub.2O.sub.3, and combinations thereof),
TiO.sub.2, ZrO.sub.2 are known in the art. For example 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.)).
[0051] 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.)).
[0052] 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.
[0053] Sources, including commercial sources, of BaO include barium
oxide powders, barium-containing ores, barium salts, barium
nitrates, and barium carbonates. The barium oxide source may
contain, or only provide, barium oxide. Alternatively, the barium
oxide source may contain, or provide barium oxide, as well as one
or more metal oxides other than barium oxide (including materials
of or containing complex barium oxide).
[0054] Sources, including commercial sources, of CaO include
calcium oxide powders and calcium-containing ores. The calcium
oxide(s) source may contain, or only provide, calcium oxide.
Alternatively, the calcium oxide source may contain, or provide
calcium oxide, as well as one or more metal oxides other than
calcium oxide (including materials of or containing complex calcium
oxide).
[0055] 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 oxides (e.g.,
Dy.sub.3Al.sub.5O.sub.12, CeAl.sub.11O.sub.18, etc.)).
[0056] Sources, including commercial sources, of SiO.sub.2 include
silica powders, silicon metals, silicon-containing ores. The
silicon oxide source may contain, or only provide, silicon oxide.
Alternatively, the silicon oxide source may contain, or provide
silicon oxide, as well as one or more metal oxides other than
silicon oxide (including materials of or containing complex silicon
oxide other metal oxides).
[0057] Sources, including commercial sources, of SrO include
strontium oxide powders, strontium carbonates, and
strontium-containing ores. The strontium oxide source may contain,
or only provide, strontium oxide. Alternatively, the strontium
oxide source may contain, or provide strontium oxide, as well as
one or more metal oxides other than strontium oxide (including
materials of or containing complex strontium oxide).
[0058] Sources, including commercial sources, of TiO.sub.2 include
titanium oxide powders, titanium metals and titanium-containing
ores. The titanium oxide source may contain, or only provide,
titanium oxide. Alternatively, the titanium oxide source may
contain, or provide titanium oxide, as well as one or more metal
oxides other than titanium oxide (including materials of or
containing complex titanium oxide).
[0059] 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.
[0060] Optionally, ceramics according to the present invention
further comprise additional metal oxides beyond those needed for
the general composition. The addition of certain metal oxides may
alter the properties and/or the crystalline structure or
microstructure of ceramics made according to the present invention,
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 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 beyond those needed for
the general composition.
[0061] 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.
[0062] Further other glass compositions which may be used in
conjunction with the required glass(es) for carrying out the
present invention include those conventional glasses that are well
known in the art, including sources thereof.
[0063] For glasses that devitrify to form glass-ceramics,
crystallization may also be affected by the additions of materials
beyond those needed for the general composition. 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 invention 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.
[0064] Examples of optional metal oxides (i.e., metal oxides beyond
those needed for the general composition) may include, on a
theoretical oxide basis, Al.sub.2O.sub.3, BaO, CaO,
Cr.sub.2O.sub.3, CoO, Fe.sub.2O.sub.3, GeO.sub.2, HfO.sub.2,
Li.sub.2O, MgO, MnO, NiO, Na.sub.2O, P.sub.2O.sub.5, rare earth
oxides, 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, ZrO.sub.2, and combinations
thereof. Sources, including commercial sources, include the oxides
themselves, complex oxides, ores, carbonates, acetates, nitrates,
chlorides, hydroxides, etc. Further, for example, with regard to
Y.sub.2O.sub.3, sources, including commercial sources, of (on a
theoretical oxide basis) Y.sub.2O.sub.3 include yttrium oxide
powders, yttrium, yttrium-containing ores, and yttrium salts (e.g.,
yttrium carbonates, nitrates, chlorides, hydroxides, and
combinations thereof). The Y.sub.2O.sub.3 source may contain, or
only provide, Y.sub.2O.sub.3. Alternatively, the Y.sub.2O.sub.3
source may contain, or provide Y.sub.2O.sub.3, as well as one or
more metal oxides other than Y.sub.2O.sub.3 (including materials of
or containing complex Y.sub.2O.sub.3 (e.g.,
Y.sub.3Al.sub.5O.sub.12)).
[0065] 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, 50, 55, 60, 65, 70, 75, 80, 85, 90,
or even at least 95 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
invention 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 U.S. Pat.
No. 7,168,267 (Rosenflanz et al.), the disclosure of which is
incorporated herein by reference.
[0066] The particular selection of metal oxide sources and other
additives for making ceramics according to the present invention
typically takes into account, for example, the desired composition
and microstructure of the resulting 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.
[0067] The metal oxide sources and other additives can be in any
form suitable to the process and equipment utilized for the present
invention. 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.
[0068] Other techniques for forming melts, cooling/quenching melts,
and/or otherwise forming glass include vapor phase quenching,
plasma spraying, melt-extraction, and gas 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, U.S. Pat. No. 7,179,526 (Rosenflanz et al.), the
disclosure of which is incorporated herein by reference.
[0069] 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 are then recovered. 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 invention.
[0070] 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.
[0071] 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.
[0072] With regard to making particles, for example, the resulting
ceramic (e.g., glass or ceramic comprising glass may be larger in
size than that desired. The ceramic can be, and typically is,
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 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.
[0073] The shape of particles can depend, for example, on the
composition of the glass, the geometry in which it was cooled, and
the manner in which the glass is crushed (i.e., the crushing
technique used), if the particles were formed by crushing.
[0074] Certain articles according to the present invention
comprising glass can be heat-treated to increase or at least
partially crystallize the glass (including crystallize the glass)
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 invention should be able to provide
TTT curves for glasses according to the present invention,
determine the appropriate nucleation and/or crystal growth
conditions to provide crystalline ceramics, glass-ceramics, and
ceramic comprising glass according to the present invention.
[0075] Typically, glass-ceramics are stronger than the glasses from
which they are formed. Hence, the strength of the material may be
adjusted, for example, by the degree to which the glass 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.
[0076] For example, during heat-treatment of a glass such as a
glass comprising Al.sub.2O.sub.3, La.sub.2O.sub.3, and ZrO.sub.2
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 glass. For example, 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. Crystallite size
during this nucleation step may be on the order of nanometers. For
example, crystals as small as 10-15 nanometers have been observed.
Longer heat-treating temperatures typically lead to the growth of
crystallites and progression of crystallization. For at least some
embodiments, heat-treatment at about 1300.degree. C. for about 1
hour provides a full crystallization.
[0077] Certain ceramic articles made according to the present
invention contain less than less than 20% by weight SiO.sub.2 (or
even less than 15%, less than 10%, less than, 5% by weight, or even
zero percent, by weight, SiO.sub.2), less than 20% by weight
B.sub.2O.sub.3 (or even less than 15%, less than 10%, less than, 5%
by weight, or even zero percent, by weight, B.sub.2O.sub.3), and
less than 40% by weight P.sub.2O.sub.5 (or even less than 35%, less
than 30%, less than 25%, less than 20%, less than 15%, less than
10%, less than, 5% by weight, or even zero percent, by weight,
P.sub.2O.sub.5), based on the total metal oxide weight of the
ceramic.
[0078] 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.
[0079] 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.
[0080] 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.
[0081] 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.
[0082] 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.
[0083] 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.
[0084] Ceramic articles (including glass-ceramics) made according
to the present invention 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, ceramic articles (including glass-ceramics) made
according to the present invention 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 invention 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, ceramic articles
(including glass-ceramics) made according to the present invention
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. In another aspect,
ceramic articles (including glass-ceramics) made according to the
present invention may be free of at least one of eutectic
microstructure features (i.e., is free of colonies and lamellar
structure) or a non-cellular microstructure.
[0085] In another aspect, certain ceramic articles made according
to the present invention 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 glass. In another aspect,
certain ceramic articles made according to the present invention
may comprise, for example, 100 or 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.
[0086] Certain articles made according to the present invention
comprise glass comprising CaO and Al.sub.2O.sub.3, wherein at least
80 (85, 90, 95, 97, 98, 99, or even 100) percent by weight of the
glass collectively comprises the CaO and Al.sub.2O.sub.3, based on
the total weight of the glass.
[0087] In another aspect, certain articles made according to the
present invention provides a ceramic comprising glass (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 glass comprising CaO and Al.sub.2O.sub.3, wherein at least 80
(85, 90, 95, 97, 98, 99, or even 100) percent by weight of the
glass collectively comprises the CaO and Al.sub.2O.sub.3, based on
the total weight of the glass.
[0088] In another aspect, certain articles made according to the
present invention provides glass-ceramic comprising CaO and
Al.sub.2O.sub.3, wherein at least 80 (85, 90, 95, 97, 98, 99, or
even 100) percent by weight of the glass-ceramic collectively
comprises CaO and Al.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.
[0089] In another aspect, certain articles made according to the
present invention provides a 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,
wherein at least 80 (85, 90, 95, 97, 98, 99, or even 100) percent
by weight of the crystalline ceramic collectively comprises the CaO
and Al.sub.2O.sub.3, based on the total weight of the crystalline
ceramic. 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.
[0090] In another aspect, certain articles made according to the
present invention provides a 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 CaO and
Al.sub.2O.sub.3, wherein at least 80 (85, 90, 95, 97, 98, 99, or
even 100) percent by weight of the ceramic collectively comprises
CaO and Al.sub.2O.sub.3, based on the total weight of the ceramic.
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.
[0091] Certain articles made according to the present invention
comprise glass comprising CaO, Al.sub.2O.sub.3, and ZrO.sub.2,
wherein at least 80 (85, 90, 95, 97, 98, 99, or even 100) percent
by weight of the glass collectively comprises the CaO,
Al.sub.2O.sub.3, and ZrO.sub.2, based on the total weight of the
glass.
[0092] In another aspect, certain articles made according to the
present invention provides a ceramic comprising glass (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 glass comprising CaO, Al.sub.2O.sub.3, and ZrO.sub.2, wherein
at least 80 (85, 90, 95, 97, 98, 99, or even 100) percent by weight
of the glass collectively comprises the CaO and Al.sub.2O.sub.3,
and ZrO.sub.2, based on the total weight of the glass.
[0093] In another aspect, certain articles made according to the
present invention provides glass-ceramic comprising CaO,
Al.sub.2O.sub.3, and ZrO.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 CaO, Al.sub.2O.sub.3, and ZrO.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.
[0094] In another aspect, certain articles made according to the
present invention provides a 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,
wherein at least 80 (85, 90, 95, 97, 98, 99, or even 100) percent
by weight of the crystalline ceramic collectively comprises the
CaO, Al.sub.2O.sub.3, and ZrO.sub.2, based on the total weight of
the crystalline ceramic. 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.
[0095] In another aspect, certain articles made according to the
present invention provides a 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 CaO,
Al.sub.2O.sub.3, and ZrO.sub.2, wherein at least 80 (85, 90, 95,
97, 98, 99, or even 100) percent by weight of the ceramic
collectively comprises CaO, Al.sub.2O.sub.3, and ZrO.sub.2, based
on the total weight of the ceramic. 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.
[0096] Certain articles made according to the present invention
comprise glass comprising BaO and TiO.sub.2, wherein at least 80
(85, 90, 95, 97, 98, 99, or even 100) percent by weight of the
glass collectively comprises the BaO and TiO.sub.2, based on the
total weight of the glass.
[0097] In another aspect, certain articles made according to the
present invention provides a ceramic comprising glass (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 glass comprising BaO and TiO.sub.2, wherein at least 80 (85,
90, 95, 97, 98, 99, or even 100) percent by weight of the glass
collectively comprises the BaO and TiO.sub.2, based on the total
weight of the glass.
[0098] In another aspect, certain articles made according to the
present invention provides glass-ceramic comprising BaO and
TiO.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 BaO and TiO.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.
[0099] In another aspect, certain articles made according to the
present invention provides a 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,
wherein at least 80 (85, 90, 95, 97, 98, 99, or even 100) percent
by weight of the crystalline ceramic collectively comprises the BaO
and TiO.sub.2, based on the total weight of the crystalline
ceramic. 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.
[0100] In another aspect, certain articles made according to the
present invention provides a 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 BaO and
TiO.sub.2, wherein at least 80 (85, 90, 95, 97, 98, 99, or even
100) percent by weight of the ceramic collectively comprises BaO
and TiO.sub.2, based on the total weight of the ceramic. 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.
[0101] Certain articles made according to the present invention
comprise glass comprising La.sub.2O.sub.3 and TiO.sub.2, wherein at
least 80 (85, 90, 95, 97, 98, 99, or even 100) percent by weight of
the glass collectively comprises the La.sub.2O.sub.3 and TiO.sub.2,
based on the total weight of the glass.
[0102] In another aspect, certain articles made according to the
present invention provides a ceramic comprising glass (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 glass comprising La.sub.2O.sub.3 and TiO.sub.2, wherein at
least 80 (85, 90, 95, 97, 98, 99, or even 100) percent by weight of
the glass collectively comprises the La.sub.2O.sub.3 and TiO.sub.2,
based on the total weight of the glass.
[0103] In another aspect, certain articles made according to the
present invention provides glass-ceramic comprising La.sub.2O.sub.3
and TiO.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 La.sub.2O.sub.3 and TiO.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, 1,
or 5 percent by volume crystalline ceramic.
[0104] In another aspect, certain articles made according to the
present invention provides a 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,
wherein at least 80 (85, 90, 95, 97, 98, 99, or even 100) percent
by weight of the crystalline ceramic collectively comprises the
La.sub.2O.sub.3 and TiO.sub.2, based on the total weight of the
crystalline ceramic. 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.
[0105] In another aspect, certain articles made according to the
present invention provides a 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 La.sub.2O.sub.3
and TiO.sub.2, wherein at least 80 (85, 90, 95, 97, 98, 99, or even
100) percent by weight of the ceramic collectively comprises
La.sub.2O.sub.3 and TiO.sub.2, based on the total weight of the
ceramic. 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.
[0106] Certain articles made according to the present invention
comprise glass comprising REO and Al.sub.2O.sub.3, wherein at least
80 (85, 90, 95, 97, 98, 99, or even 100) percent by weight of the
glass collectively comprises the REO and Al.sub.2O.sub.3, based on
the total weight of the glass.
[0107] In another aspect, certain articles made according to the
present invention provides a ceramic comprising glass (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 glass comprising REO and Al.sub.2O.sub.3, wherein at least 80
(85, 90, 95, 97, 98, 99, or even 100) percent by weight of the
glass collectively comprises the REO and Al.sub.2O.sub.3, based on
the total weight of the glass.
[0108] In another aspect, certain articles made according to the
present invention provides glass-ceramic comprising REO and
Al.sub.2O.sub.3, wherein at least 80 (85, 90, 95, 97, 98, 99, or
even 100) percent by weight of the glass-ceramic collectively
comprises the REO and Al.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.
[0109] In another aspect, the present invention provides
glass-ceramic comprising REO and Al.sub.2O.sub.3, wherein, for
example, glass-ceramic exhibits a microstructure comprising
crystallites 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 or a non-cellular
microstructure. 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 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.
[0110] In another aspect, certain articles made according to the
present invention provides a 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,
wherein at least 80 (85, 90, 95, 97, 98, 99, or even 100) percent
by weight of the crystalline ceramic collectively comprises the REO
and Al.sub.2O.sub.3, based on the total weight of the crystalline
ceramic. 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.
[0111] In another aspect, certain articles made according to the
present invention provides a 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 REO and
Al.sub.2O.sub.3, wherein at least 80 (85, 90, 95, 97, 98, 99, or
even 100) percent by weight of the ceramic collectively comprises
REO and Al.sub.2O.sub.3, based on the total weight of the ceramic.
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.
[0112] Certain articles made according to the present invention
comprise glass comprising REO and Al.sub.2O.sub.3, wherein at least
80 (85, 90, 95, 97, 98, 99, or even 100) percent by weight of the
glass collectively comprises the REO and Al.sub.2O.sub.3, based on
the total weight of the glass.
[0113] In another aspect, certain articles made according to the
present invention provides a ceramic comprising glass (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 glass comprising REO, Al.sub.2O.sub.3, and ZrO.sub.2, wherein
at least 80 (85, 90, 95, 97, 98, 99, or even 100) percent by weight
of the glass collectively comprises the REO and Al.sub.2O.sub.3 and
ZrO.sub.2, based on the total weight of the glass.
[0114] In another aspect, certain articles made according to the
present invention provides glass-ceramic comprising REO,
Al.sub.2O.sub.3, and ZrO.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 REO and Al.sub.2O.sub.3 and ZrO.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.
[0115] In another aspect, the present invention provides
glass-ceramic comprising REO, Al.sub.2O.sub.3, and ZrO.sub.2,
wherein the glass-ceramic (a) exhibits a microstructure comprising
crystallites 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 or a non-cellular
microstructure. 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 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.
[0116] In another aspect, certain articles made according to the
present invention provides a 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,
wherein at least 80 (85, 90, 95, 97, 98, 99, or even 100) percent
by weight of the crystalline ceramic collectively comprises the
REO, Al.sub.2O.sub.3, and ZrO.sub.2, based on the total weight of
the crystalline ceramic. 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.
[0117] In another aspect, certain articles made according to the
present invention provides a 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 REO and
Al.sub.2O.sub.3 and ZrO.sub.2, wherein at least 80 (85, 90, 95, 97,
98, 99, or even 100) percent by weight of the ceramic collectively
comprises REO, Al.sub.2O.sub.3, and ZrO.sub.2, based on the total
weight of the ceramic. 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.
[0118] In another aspect, certain articles made according to the
present invention provides a ceramic comprising glass (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 glass comprising REO, Al.sub.2O.sub.3, ZrO.sub.2, and SiO.sub.2
wherein at least 80 (85, 90, 95, 97, 98, 99, or even 100) percent
by weight of the glass collectively comprises the REO and
Al.sub.2O.sub.3 and ZrO.sub.2, based on the total weight of the
glass.
[0119] In another aspect, certain articles made according to the
present invention provides glass-ceramic comprising REO,
Al.sub.2O.sub.3, ZrO.sub.2, and SiO.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 REO and Al.sub.2O.sub.3
and ZrO.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.
[0120] In another aspect, the present invention provides
glass-ceramic comprising REO, Al.sub.2O.sub.3, ZrO.sub.2, and
SiO.sub.2, wherein the glass-ceramic (a) exhibits a microstructure
comprising crystallites 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 or a non-cellular
microstructure. 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 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.
[0121] In another aspect, certain articles made according to the
present invention provides a 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,
wherein at least 80 (85, 90, 95, 97, 98, 99, or even 100) percent
by weight of the crystalline ceramic collectively comprises the
REO, Al.sub.2O.sub.3, ZrO.sub.2, and SiO.sub.2, based on the total
weight of the crystalline ceramic. 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.
[0122] In another aspect, certain articles made according to the
present invention provides a 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 REO and
Al.sub.2O.sub.3 and ZrO.sub.2, wherein at least 80 (85, 90, 95, 97,
98, 99, or even 100) percent by weight of the ceramic collectively
comprises REO, Al.sub.2O.sub.3, ZrO.sub.2, and SiO.sub.2, based on
the total weight of the ceramic. 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.
[0123] Crystalline phases that may be present in ceramics according
to the present invention include alumina (e.g., alpha and
transition aluminas), BaO, CaO, Cr.sub.2O.sub.3, CoO,
Fe.sub.2O.sub.3, GeO.sub.2, HfO.sub.2, Li.sub.2O, MgO, MnO, NiO,
Na.sub.2O, P.sub.2O.sub.5, REO, 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,
ZrO.sub.2, "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, at least one of REO or 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.
09/922,527, 09/922,528, and 09/922,530, filed Aug. 2, 2001; U.S.
2003/0115805 A1 (Rosenflanz et al.); U.S. 2003/0110707 A1
(Rosenflanz et al.); U.S. Pat. No. 7,168,267 (Rosenflanz et al.);
U.S. 2003/0126802 A1 (Rosenflanz); U.S. Pat. No. 7,147,544
(Rosenflanz et al.); and U.S. Pat. No. 7,101,819 (Rosenflanz et
al., the disclosures of which are incorporated herein by
reference.
[0125] Typically, and desirably, the (true) density, sometimes
referred to as specific gravity, of ceramic according to the
present invention is typically at least 70% of theoretical density.
More desirably, the (true) density of ceramic according to the
present invention is at least 75%, 80%, 85%, 90%, 95%, 96%, 97%,
98%, 99%, 99.5% or 100% of theoretical density.
[0126] Examples of articles according of the present invention
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. Further, for
example, ceramic according to the present invention can be used as
a matrix material. For example, ceramics according to the present
invention 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
invention can be used as binders may, for example, increase the
modulus, heat resistance, wear resistance, and/or strength of the
composite article.
[0127] Advantages and embodiments of this invention 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 invention. 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
[0128] A polyethylene bottle was charged with 27.5 grams of alumina
particles (obtained under the trade designation "APA-0.5" from
Condea Vista, Tucson, Ariz.), 22.5 grams of calcium oxide particles
(obtained from Alfa Aesar, Ward Hill, Mass.) and 90 grams of
isopropyl alcohol. About 200 grams of zirconia milling media
(obtained from Tosoh Ceramics, Division of Bound Brook, N.J., under
the trade designation "YTZ") were added to the bottle, and the
mixture was milled at 120 revolutions per minute (rpm) for 24
hours. 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).
[0129] 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.
Examples 2-9
[0130] Examples 2-9 glass beads were prepared as described in
Example 1, 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 Batch Example of components
amounts, g 2 CaO: 36 CaO: 18 Al.sub.2O.sub.3: 44 Al.sub.2O.sub.3:
22 ZrO.sub.2: 20 ZrO.sub.2: 10 3 La.sub.2O.sub.3: 45
La.sub.2O.sub.3: 22.5 TiO.sub.2: 55 TiO.sub.2: 27.5 4
La.sub.2O.sub.3: 36 La.sub.2O.sub.3: 18 TiO.sub.2: 44 TiO.sub.2: 22
ZrO.sub.2: 20 ZrO.sub.2: 10 5 BaO: 47.5 BaO: 23.75 TiO.sub.2: 52.5
TiO.sub.2: 26.25 6 La.sub.2O.sub.3: 48 La.sub.2O.sub.3: 24
Al.sub.2O.sub.3: 52 Al.sub.2O.sub.3: 26 7 La.sub.2O.sub.3: 40.9
La.sub.2O.sub.3: 20.45 Al.sub.2O.sub.3: 40.98 Al.sub.2O.sub.3:
20.49 ZrO.sub.2: 18.12 ZrO.sub.2: 9.06 8 La.sub.2O.sub.3: 43
La.sub.2O.sub.3: 21.5 Al.sub.2O.sub.3: 32 Al.sub.2O.sub.3: 16
ZrO.sub.2: 12 ZrO.sub.2: 6 SiO.sub.2: 13 SiO.sub.2: 6.5 9 SrO:
22.95 SrO: 11.47 Al.sub.2O.sub.3: 62.05 Al.sub.2O.sub.3: 31.25
ZrO.sub.2: 15 ZrO.sub.2: 7.5
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 Lanthanum oxide particles Obtained
from Molycorp Inc., Mountain (La.sub.2O.sub.3) Pass, CA Silica
particles (SiO.sub.2) Obtained from Alfa Aesar Barium oxide
particles (BaO) Obtained from Aldrich Chemical Co. Titanium dioxide
particles Obtained from Kemira Inc., Savannah, (TiO.sub.2) GA
Strontium oxide particles Obtained from Alfa Aesar (SrO)
Yttria-stabilized zirconium Obtained from Zirconia Sales, Inc. of
oxide particles (Y-PSZ) Marietta, GA under the trade designation
"HSY-3"
[0131] Various properties/characteristics of some of Examples 1-9
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
amorphous 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 an amorphous matrix. Phases detected in
various examples are reported in Table 3, below.
TABLE-US-00003 TABLE 3 Phases detected via Hot-pressing Example
X-ray diffraction Color T.sub.g, .degree. C. T.sub.x, .degree. C.
temp, .degree. C. 1 Amorphous* Clear 850 987 985 2 Amorphous* Clear
851 977 975 3 Amorphous* Clear 799 875 880 4 Amorphous* Clear 821
876 880 5 Amorphous* Clear 724 760 815 6 Amorphous* Clear 855 920
970 7 Amorphous* Clear 839 932 965 8 Amorphous* Clear 836 1002 970
9 Amorphous* Clear 875 934 975 *glass, as the example has a
T.sub.g
[0132] For differential thermal analysis (DTA), a material was
screened to retain glass beads within 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.
[0133] Referring to FIG. 1, line 375 is the plotted DTA data for
the Example 1 material. Referring to FIG. 1 line 375, the material
exhibited an endothermic event at a temperature around 799.degree.
C., as evidenced by the downward curve of line 375. It was believed
that this event was due to the glass transition (T.sub.g) of the
material. At about 875.degree. C., an exothermic event was observed
as evidenced by the sharp peak in line 345. 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.
[0134] FIGS. 2-6 are the plotted DTA data for Examples 2, 5, 6, 7,
and 9, respectively.
[0135] For each of Examples 1-9, about 25 grams of the glass beads
were placed in a graphite die and hot-pressed using uniaxial
pressing apparatus (obtained under the trade designation "HP-50",
Thermal Technology Inc., Brea, Calif.). The hot-pressing was
carried out in an argon atmosphere and 13.8 megapascals (MPa) (2000
pounds per square inch (2 ksi)) pressure. 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 Examples 1-9 in Table 3,
above.
[0136] Various modifications and alterations of this invention will
become apparent to those skilled in the art without departing from
the scope and spirit of this invention, and it should be understood
that this invention is not to be unduly limited to the illustrative
embodiments set forth herein.
* * * * *