U.S. patent application number 09/891655 was filed with the patent office on 2004-11-04 for metal oxide powder and method for the production of the same.
Invention is credited to Hasegawa, Akira, Koike, Hironobu, Mohri, Masahide, Saegusa, Kunio, Tanaka, Shinichiro, Umeda, Tetsu, Watanabe, Hisashi.
Application Number | 20040219087 09/891655 |
Document ID | / |
Family ID | 27476974 |
Filed Date | 2004-11-04 |
United States Patent
Application |
20040219087 |
Kind Code |
A1 |
Mohri, Masahide ; et
al. |
November 4, 2004 |
Metal oxide powder and method for the production of the same
Abstract
A metal oxide powder except .alpha.-alumina, comprising
polyhedral particles having at least 6 planes each, a number
average particle size of from 0.1 to 300 .mu.m, and a
D.sub.90/D.sub.10 ratio of 10 or less where D.sub.10 and D.sub.90
are particle sizes at 10% and 90% accumulation, respectively from
the smallest particle size side in a cumulative particle size curve
of the particles. This metal oxide powder contains less
agglomerated particles, and has a narrow particle size distribution
and a uniform particle shape.
Inventors: |
Mohri, Masahide; (Tsukuba,
JP) ; Koike, Hironobu; (Tsukuba, JP) ; Tanaka,
Shinichiro; (Tsukuba, JP) ; Umeda, Tetsu;
(Tsukuba, JP) ; Watanabe, Hisashi; (Tsukuba,
JP) ; Saegusa, Kunio; (Tsukuba, JP) ;
Hasegawa, Akira; (Tsukuba, JP) |
Correspondence
Address: |
SUGHRUE, MION, ZINN, MACPEAK & SEAS
2100 Pennsylvania Avenue, N.W.
Washington
DC
20037
US
|
Family ID: |
27476974 |
Appl. No.: |
09/891655 |
Filed: |
June 27, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09891655 |
Jun 27, 2001 |
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08416738 |
Jun 9, 1995 |
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6303091 |
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08416738 |
Jun 9, 1995 |
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PCT/JP94/01329 |
Aug 11, 1994 |
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Current U.S.
Class: |
423/263 ;
423/260; 423/605; 423/606; 423/607; 423/608; 423/610; 423/617;
423/618; 423/624; 423/632; 423/635 |
Current CPC
Class: |
C01P 2002/72 20130101;
C01P 2004/30 20130101; C01B 13/32 20130101; C01P 2004/54 20130101;
C01B 13/185 20130101; C01P 2004/62 20130101; C01P 2002/30 20130101;
C01G 25/02 20130101; C01F 17/34 20200101; C01G 19/02 20130101; C01P
2002/02 20130101; C01P 2002/50 20130101; C01P 2004/03 20130101;
C01G 15/00 20130101; C01G 23/047 20130101; C01P 2004/50 20130101;
C01B 13/14 20130101; C01F 17/235 20200101; C01P 2004/61 20130101;
C01P 2006/12 20130101; C01G 49/06 20130101; C01F 5/02 20130101;
C01P 2004/52 20130101; C01P 2004/51 20130101; C01F 5/06 20130101;
C01B 13/18 20130101; C01G 49/0054 20130101; C09K 3/1436
20130101 |
Class at
Publication: |
423/263 ;
423/608; 423/632; 423/610; 423/635; 423/624; 423/618; 423/617;
423/607; 423/606; 423/605; 423/260 |
International
Class: |
C01G 023/047; C01G
001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 11, 1993 |
JP |
220715/1993 |
Sep 9, 1993 |
JP |
249924/1993 |
Oct 28, 1993 |
JP |
294528/1993 |
Nov 9, 1993 |
JP |
304639/1993 |
Claims
1. A metal oxide powder except .alpha.-alumina, comprising
polyhedral particles having at least 6 planes each, a number
average particle size of 0.1 to 40 .mu.m and a D.sub.90/D.sub.10
ratio of 5 or less where D.sub.10 and D.sub.90 are particle sizes
at 10% and 90% accumulation, respectively from the smallest
particle size side in a cumulative particle size curve of the
particles, and wherein a ratio of agglomerated particle size to a
primary particle size is from 1 to 6, and the metal oxide is a
metal oxide of a metal element selected from the group consisting
of the metal elements of the Group Ib, II, III, V, VI, VII and VIII
of the Periodic Table.
2-3. (canceled).
4. The metal oxide powder according to claim 1, wherein said ratio
of a primary particle size to an agglomerated particle size is from
1 to 3.
5. (canceled).
6. The metal oxide powder according to any one of claims 1 and 4,
wherein said metal oxide is a simple metal oxide titanium.
7. The metal oxide powder according to any one of claims 1 and 4,
wherein said metal oxide is a simple metal oxide of a metal
selected from the group consisting of magnesium, zirconium and
iron.
8. The metal oxide powder according to any one of claims 1 and 4,
wherein said metal oxide is a simple metal oxide of cerium.
9. The metal oxide powder according to any one of claims 1 and 4,
wherein said metal oxide is a simple metal oxide of a metal
selected from the group consisting of indium and tin.
10. The metal oxide powder according to any one of claims 1 and 4,
wherein said metal oxide is a simple metal oxide of a metal
selected from the group consisting of zinc, cadmium, gallium,
germanium, niobium, tantalum, antimony, bismuth, chromium,
molybdenum, manganese, cobalt, nickel and uranium.
11. A rutile type titanium oxide powder comprising polyhedral
particles each having at least 8 planes, a number average particle
size of from 0.1 to 300 .mu.m, a D.sub.90/D.sub.10 ratio of 5 or
less where D.sub.10 and D.sub.90 are particle sizes at 10% and 90%
accumulation, respectively from the smallest particle size side in
a cumulative particle size curve of the particles, and a ratio of
agglomerated particle size to primary particle size of the
particles is from 1 to 6.
12. The rutile type titanium oxide powder according to claim 11,
wherein a ratio of an agglomerated particle size to a primary
particle size is from 1 to 2, and a BET specific surface area is
from 0.1 to 10 m.sup.2/g.
13. A method for producing a calcined metal oxide powder having a
narrow particle size distribution except .alpha.-alumina,
comprising calcining a metal oxide powder or a metal oxide
precursor powder in the presence or absence of a seed crystal in an
atmosphere containing at least one gas selected from the group
consisting of (1) a hydrogen halide, (2) a component prepared from
a molecular halogen and steam and (3) a molecular halogen.
14. The method according to claim 13, wherein said calcination is
carried out in the presence of a seed crystal.
15. The method according to claim 13 or 14, wherein said gas
contained in said atmosphere gas is a hydrogen halide.
16. The method according to claim 15, wherein said hydrogen halide
is hydrogen chloride or hydrogen bromide.
17. The method according to claim 15, wherein said hydrogen halide
is hydrogen fluoride.
18. The method according to claim 15, wherein a concentration of
said hydrogen halide is at least 1 vol. % of said atmospheric
gas.
19. The method according to claim 13 or 14, wherein said gas
contained in said atmosphere gas is said component prepared from a
molecular halogen and steam.
20. The method according to claim 19, wherein said molecular
halogen is chlorine or bromine.
21. The method according to claim 19, wherein said molecular
halogen is fluorine.
22. The method according to claim 19, wherein said component is
prepared from at least 1 vol. % of said molecular halogen and at
least 0.1 vol. % of steam, both based on said atmosphere gas.
23. The method according to claim 13 or 14, wherein said gas
contained in said atmosphere gas is a molecular halogen which is
chlorine or bromine, and a concentration of said molecular halogen
in said atmosphere gas is at least 1 vol. %.
24. The method according to claim 13, wherein said metal oxide
powder or metal oxide precursor powder has a bulk density of 40% or
less of a theoretical value.
25. The method according to claim 14, wherein said seed crystal had
a bulk density of 40% or less of a theoretical value.
26. The method according to claim 13 or 14, wherein said metal
oxide having a narrow particle size distribution except
.alpha.-alumina is formed on a site where said metal oxide powder
or metal oxide precursor powder to be calcined is present.
27. The method according to claim 13 or 14, wherein said metal
oxide powder or metal oxide precursor powder to be calcined is a
metal oxide powder or metal oxide precursor powder of a metal
element selected from the group consisting of the metal elements of
the Groups Ib, II, III, IV, V, VI, VII and VIII of the Periodic
Table.
28 The method according to claim 13 or 14, wherein said metal oxide
powder or metal oxide precursor powder is a metal oxide powder or
metal oxide precursor powder of a metal selected from the group
consisting of magnesium, titanium, and iron.
29-30. (canceled).
31. The method according to claim 13 or 14, wherein said metal
oxide powder or metal oxide precursor powder is a metal oxide
powder or metal oxide precursor powder of a metal selected from the
group consisting of zinc, cadmium, gallium, germanium, niobium,
tantalum, antimony, bismuth, chromium, molybdenum, manganese,
cobalt, nickel and uranium.
32. A method for producing a calcined metal oxide powder having a
narrow particle size distribution except .alpha.-alumina,
comprising calcining a metal oxide powder or a metal oxide
precursor powder in the presence or absence of a seed crystal in an
atmosphere containing at least one gas selected from the group
consisting of (1) a hydrogen halide, and (2) a component prepared
from a molecular halogen and steam.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a metal oxide powder which
is used as a raw material powder of an oxide ceramic that is used
as a functional material or a structural material, a metal oxide
powder which is used in a dispersed state as a filler or a pigment,
or a metal oxide powder which is used as a raw material powder for
the production of a single crystal or for flame spray coating, and
a method for the production thereof.
PRIOR ART
[0002] In general, an oxide ceramic which is used as a functional
material or a structural material is produced through a molding
step and a calcination step from a metal oxide powder as a raw
material. Properties of the metal oxide powder to be used as the
raw material have a large influence on the production steps, and
functions and physical properties of the ceramic product. Then, it
is highly desired to provide a metal oxide powder having powder
properties which are precisely controlled so that they are suitable
for an intended application.
[0003] When a metal oxide powder is used in a dispersed state such
as a magnetic fine powder, a filler or a pigment, since properties
of each particle are reflected directly on the dispersed state, the
control of the properties of the powder is more important.
[0004] The required properties of the metal oxide powder vary with
a kind and application form of the metal oxide. Commonly required
properties are a uniform particle size of the metal oxide powder,
that is, a narrow particle size distribution, and a weak bond among
primary particles, that is, less agglomeration and good
dispersibility.
[0005] For example, a titanium oxide powder is widely used as a raw
material of a white pigment, a raw material of a filler to be added
to a resin, a raw material of a material having a high refractive
index, a raw material of a UV light absorber, a raw material of a
single crystal, a raw material of a photocatalytic active
semiconductor, a raw material of a catalyst support, a raw material
of an abrasive, a raw material of a dielectric material, and so
on.
[0006] A zirconium oxide powder is useful as a material to be used
in a high temperature material or a mechanical structural material,
an ion conductive material, a piezoelectric material and so on, and
is used as a raw material of a calcined body and a raw material for
melt spray coating.
[0007] A magnesium oxide powder is a useful as a raw material of a
refractory ceramic, a raw material of a functional ceramic such as
an electronics material or an optical material, and the like.
[0008] A cerium oxide powder is one of oxides of rare earth
elements, and useful as an electrical conductive material, an
optical material, or an abrasive.
[0009] A tin oxide powder is a valuable material used as an
electronics material, a pigment, a catalyst or an abrasive.
[0010] Hitherto, these metal oxides are produced by a liquid phase
method, a gas phase method, a hydrothermal synthesis method, a
direct oxidation method, an electrical fusion method, and the like.
The produced metal oxide powders have some problems such as
formation of agglomerates, nonuniformity in the particles, a wide
particle size distribution, and so on, and they are not necessarily
satisfactory. Further, the above production methods themselves have
problems such as complicated procedures, problems of apparatuses,
costs of raw materials, and so on. Then, it has been desired to
develop a metal oxide powder which contains less agglomerated
particles and have a narrow particle size distribution, and to
develop a method for producing such metal oxide powder generally
and advantageously in an industrial production.
SUMMARY OF THE INVENTION
[0011] An object of the present invention is to provide a metal
oxide containing less agglomerated particles and having a narrow
particle size distribution and a uniform particle shape, which is
preferably used as a metal oxide powder to be used as a raw
material powder of an oxide ceramic that is used as a functional
material or a structural material, a metal oxide powder to be used
in a dispersed state as a filler or a pigment, or a metal oxide
powder to be used as a raw material powder for the production of a
single crystal or for flame spray coating.
[0012] Another object of the present invention is to provide a
production method which can be generally employed in the production
of such metal oxide powder and is excellent industrially.
[0013] As a result of the extensive study on the metal oxide
powders, it has been found that, when a raw material is calcined in
a specific atmosphere gas, the above described metal oxide
containing less agglomerated particles and having a narrow particle
size distribution and a uniform particle shape is obtained, and
that such method can be employed generally in the production of
various metal oxide powders and excellent industrially, and the
present invention has been completed after further
investigations.
[0014] That is, according to a first aspect of the present
invention, there is provided a metal oxide powder except
.alpha.-alumina, comprising polyhedral particles having at least 6
planes each, a number average particle size of from 0.1 to 300
.mu.m, and a D.sub.90/D.sub.10 ratio of 10 or less where D.sub.10
and D.sub.90 are particle sizes at 10% and 90% accumulation,
respectively from the smallest particle size side in a cumulative
particle size curve of the particles.
[0015] According to a second aspect of the present invention, there
is provided a rutile type titanium oxide powder comprising
polyhedral particles each having at least 8 planes.
[0016] According to a third aspect of the present invention, there
is provided a method for producing a metal oxide powder except
.alpha.-alumina, having a narrow particle size distribution,
comprising calcining a metal oxide powder or a metal oxide
precursor powder in the presence or absence of a seed crystal in an
atmosphere containing at least one gas selected from the group
consisting of (1) a hydrogen halide, (2) a component prepared from
a molecular halogen and steam and (3) a molecular halogen.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a scanning electron microscopic photograph (x 850)
showing a particle structure of a titanium oxide powder observed in
Example 1,
[0018] FIG. 2 is a scanning electron microscopic photograph (x
1700) showing a particle structure of a titanium oxide powder
observed in Example 7,
[0019] FIG. 3 is a scanning electron microscopic photograph (x
1700) showing a particle structure of a titanium oxide powder
observed in Example 9,
[0020] FIG. 4 is a scanning electron microscopic photograph (x
4300) showing a particle structure of a titanium oxide powder
observed in Example 15,
[0021] FIG. 5 is a scanning electron microscopic photograph (x
1700) showing a particle structure of a titanium oxide powder
observed in Comparative Example 1,
[0022] FIG. 6 is a scanning electron microscopic photograph (x 430)
showing a particle structure of a zirconium oxide powder observed
in Example 20,
[0023] FIG. 7 is a scanning electron microscopic photograph (x 430)
showing a particle structure of a zirconium oxide powder observed
in Example 21,
[0024] FIG. 8 is a scanning electron microscopic photograph (x 430)
showing a particle structure of a zirconium oxide powder observed
in Example 22,
[0025] FIG. 9 is a scanning electron microscopic photograph (x
1720) showing a particle structure of a zirconium oxide powder
observed in Comparative Example 3,
[0026] FIG. 10 is a scanning electron microscopic photograph (x
430) showing a particle structure of a magnesium oxide powder
observed in Example 23,
[0027] FIG. 11 is a scanning electron microscopic photograph (x
850) showing a particle structure of a magnesium oxide powder
observed in Example 24,
[0028] FIG. 12 is a scanning electron microscopic photograph (x
850) showing a particle structure of a magnesium oxide powder
observed in Example 25,
[0029] FIG. 13 is a scanning electron microscopic photograph (x
1720) showing a particle structure of a magnesium oxide powder
observed in Comparative Example 6,
[0030] FIG. 14 is a scanning electron microscopic photograph (x
1720) showing a particle structure of an iron oxide powder observed
in Example 26,
[0031] FIG. 15 is a scanning electron microscopic photograph (x
1720) showing a particle structure of an iron oxide powder observed
in Comparative Example 8,
[0032] FIG. 16 is a scanning electron microscopic photograph (x
8500) showing a particle structure of a cerium oxide powder
observed in Example 27,
[0033] FIG. 17 is a scanning electron microscopic photograph (x
4300) showing a particle structure of a cerium oxide powder
observed in Comparative Example 9,
[0034] FIG. 18 is a scanning electron microscopic photograph (x
8000) showing a particle structure of a tin oxide powder observed
in Example 28,
[0035] FIG. 19 is a scanning electron microscopic photograph (x
8000) showing a particle structure of a tin oxide powder observed
in Comparative Example 10,
[0036] FIG. 20 is a scanning electron microscopic photograph (x
15500) showing a particle structure of an indium oxide powder
observed in Example 29, and
[0037] FIG. 21 is a scanning electron microscopic photograph (x
15500) showing a particle structure of a cerium oxide powder
observed in Comparative Example 11.
DETAILED DESCRIPTION OF THE INVENTION
[0038] The present invention will be explained in detail.
[0039] The metal oxide powder having the narrow particle size
distribution is a compound of a single metal element and oxygen
consisting of polyhedral particles each having at least 6 planes
(excluding complex oxides and .alpha.-alumina powder), which is
distinguished from a metal oxide which is produced by the
conventional methods and contains may agglomerated particles.
Hereinafter, a compound of a single metal element and oxygen will
be sometimes referred to as a "simple metal oxide".
[0040] The method of the present invention produces a metal oxide
except .alpha.-alumina, having a narrow particle size distribution,
by calcining a metal oxide powder or a metal oxide precursor powder
in the presence or absence of a seed crystal in an atmosphere
containing at least one gas selected from the group consisting of
(1) a hydrogen halide, (2) a component prepared from a molecular
halogen and steam and (3) a molecular halogen.
[0041] When the metal oxide powder having the narrow particle size
distribution is produced by the method of the present invention, a
metal oxide precursor powder is exemplified as a raw material.
[0042] Herein, the metal oxide precursor powder is intended to mean
a material which gives the metal oxide consisting of the single
metal and oxygen by a decomposition reaction or an oxidation
reaction in calcination, and includes, for example, metal
hydroxides, hydrated metal oxides, metal oxyhydroxide, metal
oxyhalides, and so on.
[0043] When the metal oxide powder having the narrow particle size
distribution is produced by the method of the present invention, a
known metal oxide powder can be used as a raw material depending on
the kind of the intended metal oxide powder.
[0044] As the raw material metal oxide powder, one having an
average primary particle size of less than 0.1 .mu.m is preferably
used. As the average primary particle size of the raw material
metal oxide powder, a particle size calculated from a BET specific
surface area can be used. It is possible to produce the intended
metal oxide powder having the narrow particle size distribution and
the larger particle size than that of the raw material metal oxide
powder, from the raw material metal oxide powder having the above
particle size. When the average primary particle size of the raw
material powder is larger than 0.1 .mu.m, the production of the
metal oxide powder containing less agglomerated particles and
having the narrow particle size distribution may become
difficult.
[0045] A seed crystal which may be used in the present invention is
intended to mean a crystal which functions as a growing site for
the crystal growth of the intended metal oxide. Around the seed
crystal, the metal oxide grows. Any seed crystal can be used
insofar as it has this function. For example, when the metal oxide
precursor is used as the raw material, the metal oxide powder is
preferably used. Further, when the metal oxide powder having the
average primary particle size of less than 0.1 .mu.m is used as the
raw material, a metal oxide powder having a larger particle size
than the average particle size of the raw material metal oxide
powder, for example, a particle size at least 5 times larger than
the average primary particle size of the raw material is used.
[0046] When a crystal phase of the metal oxide as the raw material
is changed to a more stable crystal phase by calcination, the metal
oxide having the more stable crystal phase is preferred as the seed
crystal.
[0047] There is no limitation on a manner for adding the seed
crystal to the raw material powder. For example, a mixing manner
such as ball milling, ultrasonic dispersing, and the like can be
used.
[0048] The above described metal oxide precursor powder, the raw
material metal powder, for instance, the metal oxide powder having
the average primary particle size of 0.1 .mu.m or less, and those
raw materials to which the seed crystal is added are generally
named as the raw material metal oxide powder.
[0049] Examples of the metal element contained in the raw material
metal oxide powder are the metal elements of the Group Ib of the
Periodic Table such as copper, etc.; the metal elements of the
Group II such as magnesium, zinc, etc.; the metal elements of the
Group III such as yttrium, cerium, gallium, indium, uranium, etc.;
the metal elements of the Group IV such as titanium, zirconium,
germanium, etc.; the metal elements of the Group V such as
vanadium, niobium, tantalum, bismuth, etc.; the metal elements of
the Group VI such as chromium, the metal elements of the Group VII
such as manganese; and the metal elements of the Group VIII such as
iron, cobalt, nickel, etc. (except aluminum).
[0050] Preferred examples of the metal elements are magnesium,
titanium, zirconium, iron, cerium, indium, and tin.
[0051] In the method of the production of the metal oxide powder
according to the present invention, the raw material metal oxide
is; not limited, and the powder produced by the conventional method
can be used. For example, the metal oxide powder or metal oxide
precursor powder produced by the liquid phase method, or the metal
oxide powder produced by the gas phase method or the solid phase
method may be used.
[0052] In the present invention, the raw material metal oxide
powder is calcined in the atmosphere gas containing at least 1 vol.
%, preferably at least 5 vol. %, more preferably at least 10 vol. %
of the hydrogen halide based on the whole volume of the atmosphere
gas.
[0053] As the hydrogen halide, hydrogen chloride, hydrogen bromide,
hydrogen iodide and hydrogen fluoride are used independently or as
a mixture of two or more of them.
[0054] As a component of the atmosphere gas other than the hydrogen
halide, that is, a diluent gas, nitrogen, inert gas such as argon,
hydrogen, steam or an air can be used.
[0055] A pressure of the atmosphere gas containing the hydrogen
halide is not limited, and selected from a pressure range which is
industrially used.
[0056] It is possible to carry out the calcination in the
atmosphere gas containing a component prepared from the molecular
halogen and steam, in place of the hydrogen halide.
[0057] As the molecular halogen, molecular chlorine, bromine,
iodine and fluorine are used independently or as a mixture of two
or more of them.
[0058] The component gas is prepared from at least 1 vol. %,
preferably at least 5 vol. %, more preferably at least 10 vol. % of
the molecular halogen and at least 0.1 vol. %, preferably at least
1 vol. %, more preferably at least 5 vol. % of the steam, both
based on the whole volume of the atmosphere gas.
[0059] In place of the hydrogen halide, the molecular halogen may
be used. The raw material metal oxide powder is calcined in the
atmosphere gas containing at least 1 vol. %, preferably at least 5
vol. %, more preferably at least 10 vol. % of the molecular halogen
based on the whole volume of the atmosphere gas. As the molecular
halogen, at least one of molecular chlorine, bromine and iodine can
be used.
[0060] As a component of the atmosphere gas other than the
component prepared from the molecular halogen and steam, or the
molecular halogen, that is, a diluent gas, nitrogen, inert gas such
as argon, hydrogen, steam or an air can be used.
[0061] A pressure in the reaction system is not limited, and freely
selected from a pressure range which is industrially used.
[0062] A manner for supplying the atmosphere gas is not critical
insofar as the atmosphere gas can be supplied to the reaction
system in which the raw material metal oxide powder is present.
[0063] A source of each component of the atmosphere gas and a
manner for supplying each component are not critical either.
[0064] For example, as the source of each component of the
atmosphere gas, a gas in a bomb can be used. Alternatively, it is
possible to prepare the atmosphere gas comprising the hydrogen
halide or the molecular halogen using the evaporation or
decomposition of a halogen compound such as an ammonium halide, or
a halogen-containing polymer such as a vinyl chloride polymer. The
atmosphere gas may be prepared by calcining a mixture of the raw
material metal oxide and the halogen compound or halogen-containing
polymer in a calcination furnace.
[0065] The hydrogen halide and the molecular halogen are preferably
supplied from the bomb directly in the calcination furnace in view
of the operability. The atmosphere gas may be supplied in a
continuous manner or a batch manner.
[0066] According to the present invention, when the raw material
metal oxide powder is calcined in the above atmosphere gas, the
metal oxide grows at a site where the raw material metal oxide
powder is present through the reaction between the raw material
metal oxide powder and the atmosphere gas, so that the metal oxide
powder having the narrow particle size distribution, but not
agglomerated particles, is generated. Accordingly, the desired
metal oxide powder can be obtained, for example, by simply filling
the raw material metal oxide powder in a vessel and calcining it in
the atmosphere gas.
[0067] As the raw material metal oxide powder to be used in the
present invention, any material which is in a powder form may be
used, and a bulk density of the powder is preferably at least 40%
or less based on a theoretical density. When a molded material
having the bulk density exceeding 40% based on the theoretical
density is calcined, a sintering reaction proceeds in the
calcination step, whereby grinding is necessitated to obtain the
metal oxide powder, and the metal oxide powder having the narrow
particle size distribution may not be obtained in some cases.
[0068] A suitable calcination temperature is not necessarily
critical since it depends on the kin of the intended metal oxide,
the kinds and concentrations of the hydrogen halide, the molecular
halogen and the component prepared from the molecular halogen and
steam, or the calcination time. It is preferably from 500 to
1500.degree. C., more preferably from 600 to 1400.degree. C. When
the calcination time is lower than 500.degree. C., a lo time is
necessary for calcination. When the calcination temperature exceeds
1500.degree. C., many agglomerated particles tend to be con med in
the produced metal oxide powder.
[0069] A suitable calcination time is not necessarily critical
since it depends on the kind of the intended metal oxide, the kinds
and concentrations of the hydrogen halide, the molecular halogen
and the component prepared from the molecular halogen and steam, or
the calcination temperature. It is preferably at least 1 minute,
more preferably at least 10 minutes, and selected from a range in
which the intended metal oxide powder is obtained. As the
calcination temperature is higher, the calcination time is
shorter.
[0070] When the raw material metal oxide powder containing the seed
crystal is calcined, the calcination temperature can be lower and
the calcination time can be shorter than those when no seed crystal
is used, since the metal oxide grows around the seed crystals as
the growing sites.
[0071] A type of a calcination apparatus is not limited, and a
so-called calcination furnace may be used. The calcination furnace
is preferably made of a material which is not corroded by the
hydrogen halide or the halogen, and preferably comprises a
mechanism for adjusting the atmosphere.
[0072] Since the acidic gas such as the hydrogen halide or the
halogen is used, the calcination furnace is preferably an airtight
one. In the industrial production, preferably the calcination is
carried out continuously, and a tunnel furnace, a rotary kiln, or a
pusher furnace can be used.
[0073] As a vessel used in the calcination step in which the raw
material metal oxide powder is filled, preferably a crucible or a
boat made of alumina, quartz, acid-resistant brick, graphite, or a
noble metal such as platinum is used, since the reaction proceeds
in the acidic atmosphere.
[0074] When the metal oxide powder is produced with the addition of
the seed crystal to the raw material powder, the particle size and
the particle size distribution of the metal oxide powder as the
product can be controlled by changing a particle size and an added
amount of the seed crystal. For example, when the amount of the
seed crystal is increased, the particle size of the produced metal
oxide powder is decreased. When the seed crystal having the smaller
particle size is used, the particle size of the produced metal
oxide powder is decreased.
[0075] By the above described method, as shown in the attached
photographs, the metal oxide powder which is not agglomerated
particles, and has the narrow particle size distribution and
uniform particle size can be obtained, and the particle size can be
controlled.
[0076] Though the metal oxide powder may be agglomerated particles
or contain agglomerated particles, a degree of agglomeration is
small, and therefore the metal oxide powder which contains no
agglomerated particle is easily produced by simple grinding.
[0077] A number average particle size of the metal oxide powder
obtained by the method of the present invention is not necessarily
limited. In general, it is possible to obtain the metal oxide
powder having the particle size of 0.1 to 300 .mu.m.
[0078] The metal oxide powder obtained by the method of the present
invention has, as the particle size distribution, a
D.sub.90/D.sub.10 ratio of 10 or less, preferably 5 or less, where
D.sub.10 and D.sub.90 are particle sizes at 10% and 90%
accumulation, respectively from the smallest particle size side in
a cumulative particle size curve of the particles.
[0079] When a particle size distribution is measured by a
centrifugal sedimentation method or a laser diffraction scattering
method, the obtained value is a particle size distribution of the
agglomerated particles. When the particle size distribution
measured by such method is narrow but the powder contains the
agglomerated particles, the dispersibility is deteriorated, and
such powder is not suitable as an industrial raw material. In the
present invention, as a criterion of agglomeration of the powder, a
primary particle size is measured, as a number average value, from
a scanning electron microscopic photograph, and the obtained value
is compared with an agglomerated particle size, that is, a particle
size at 50% accumulation in a cumulative particle size curve of the
particles (D.sub.50).
[0080] That is, the degree of agglomeration is evaluated by a ratio
of the agglomerated particle size to the primary particle size.
When this ratio exceeds 1 (one), the powder is in the ideal state
containing no agglomerated particle. With the actual powder, this
ratio exceeds 1. When this ratio is 6 or less, the powder can be
preferably used as the industrial raw material.
[0081] The metal oxide powder obtained by the method of the present
invention has the ratio of the agglomerated particle size to the
primary particle size of, preferably from 1 to 6, more preferably
from 1 to 3, most preferably from 1 to 2.
[0082] Each of the particles of the metal oxide powder of the
present invention has a polyhedral form having at least 6 planes.
The number of the planes is usually from 6 to 60, preferably from 6
to 30.
[0083] Concrete examples of the metal oxide powder of the present
invention will be explained.
[0084] The particle of the rutile type titanium oxide powder of the
present invention comprises a polyhedron having at least 8 planes
with a crystal plane being exposed. The particle of the rutile
titanium oxide powder of the present invention preferably comprises
a polyhedron having 8 to 60 planes, more preferably 8 to 30 planes.
This is because the inside of the particle is uniform, and the
powder has less grain boundaries and less lattice defects in the
particle. In particular, the particle is preferably a single
crystal particle. When the number of the planes of the polyhedron
is less than 8, the growth of the crystal is incomplete. When the
number of the polyhedron exceeds 60, the number of the lattice
defects in the particle tends to increase. When a large step may be
present on one crystal plane of the particle, such plane is
regarded as one plane in the present invention.
[0085] The rutile type titanium oxide is characterized in that the
particle size distribution is narrow, and the number of the
agglomerated particles is small. The ratio of the agglomerated
particle size to the primary particle size is preferably from 1 to
2. The D.sub.90/D.sub.10 ratio is 10 or less, preferably 5 or
less.
[0086] When the BET specific surface area is large, the powder
contains many agglomerated particles and is not suitable as the
industrial raw material. Then, the BET specific surface area is
preferably 10 m.sup.2/g or less. When the BET specific surface area
is less than 0.1 m.sup.2/g, the primary particle size is too large
and the particles cause sedimentation when they are dispersed in a
solvent. Therefore, the BET specific surface area is preferably
from 0.1 to 10 m.sup.2/g, more preferably 0.1 to 5 m.sup.2/g.
[0087] The zirconium oxide particles of the present invention are
characterized in that their shape and particle size are uniform.
The particle shape is a polyhedron having at least 8 planes. Their
particle size and particle size distribution are controlled in the
specific ranges. The particle size is usually controlled in the
range from about 1 .mu.m to several hundred .mu.m. This control of
the particle size can be done by the selection of the raw material
and the calcination conditions in the method of the present
invention.
[0088] As the raw material powder for the flame spray coating, one
having the large particle size is preferred. As the powder
preferred for this use, the zirconium oxide powder comprising the
particles having, preferably at least 20 .mu.m, more preferably
about 40 .mu.m is selected.
[0089] That is, the above described method can produce the
zirconium oxide powder having the relatively large average particle
size suitable as the raw material for the flame spray coating, by
the industrially advantageous steps.
[0090] The zirconium oxide powder of the present invention has the
D.sub.90/D.sub.10 ratio of 10 or less, preferably 5 or less.
Further, the ratio of the agglomerated particle size to the primary
particle size is preferably from 1 to 3, more preferably from 1 to
2.
[0091] The magnesium oxide particles of the present invention are
characterized in that their shape and particle size are uniform.
The particle shape is a polyhedron having at least 8 planes. Their
particle size and particle size distribution are controlled in the
specific ranges. The particle size is usually controlled in the
range from about 1 .mu.m to several hundred .mu.m. This control of
the particle size can be done by the selection of the raw material
and the calcination conditions in the method of the present
invention.
[0092] The manganese oxide powder of the present invention has the
D.sub.90/D.sub.10 ratio 10 or less, preferably 5 or less. Further,
the ratio of the agglomerated particle size to the primary particle
size is preferably from 1 to 3, more preferably from 1 to 2.
[0093] The cerium oxide particles of the present invention are
characterized in that their shape and particle size are uniform. As
is clear from the attached photographs, they are the cerium oxide
cubic particles having the uniform shape and particle size.
[0094] The tin oxide particles of the present invention are
characterized in that their shape and particle size are uniform. As
is clear from the attached photograph, they are the polyhedrons
having at least 8 planes with the uniform shape and particle
size.
[0095] The indium oxide particles of the present invention are
characterized in that their shape and particle size are uniform. As
is clear from the attached photograph, they are the polyhedrons
having at least 8 planes with the uniform shape and particle
size.
[0096] According to the present invention, it is possible to obtain
the various metal oxide powders which are not agglomerated
particles but have the narrow particle distribution that cannot be
hitherto achieved.
[0097] In many cases, the obtained metal oxide powder is a mass of
the uniform polyhedral particles, and can be used in the variety of
applications such as the raw materials of the metal oxide base
ceramics which are used as the functional material or the
structural material, as the filler or the pigment, or the raw
material powder for the production of a single crystal or for flame
spray coating. By the selection of the particle size and amount of
the seed crystal, the metal oxide having the above properties and
the arbitrarily controlled particle size can be obtained.
Examples
[0098] Hereinafter, the present invention will be explained in
detail by examples, which do not limit the scope of the present
invention in any way.
[0099] The measurements in the examples were carried out as
follows:
[0100] 1. Number Average Particle Size of Metal Oxide Powder
[0101] A scanning electron microscopic photograph of a metal oxide
powder was taken using an electron microscope (T-300 manufactured
by Nippon Electron Co., Ltd.). From the photograph, 80 to 100
particles were selected and image analyzed to calculate an average
value of equivalent circle diameters of the particles and the
distribution. The equivalent circle diameter is a diameter of a
circle having the same area as that of each particle in the
photograph.
[0102] 2. Particle Size Distribution of Metal Oxide Powder
[0103] The particle size distribution was measured using a master
sizer (manufactured by Malvern Instrument, Inc.) or a laser
diffraction type particle size distribution analyzer (SALD-1100
manufactured by Shimadzu Corporation).
[0104] The metal oxide powder was dispersed in an aqueous solution
of polyammonium acrylate or a 50 wt. % aqueous solution of
glycerol, and particle sizes at 10%, 50% and 90% accumulation,
respectively from the smallest particle size side in a cumulative
particle size curve of the particles were measured as the D.sub.10,
D.sub.50 and D.sub.90. The D.sub.50 was used as the agglomerated
particle size, and the D.sub.90/D.sub.10 ratio was calculated as
the criterion of the particle size distribution.
[0105] 3. Crystal Phase of Metal Oxide Powder
[0106] The crystal phase of the metal oxide powder was measured by
the X-ray diffraction method (RAD-C manufactured by Rigaku Co.,
Ltd.)
[0107] 4. BET Specific Surface Area of Metal Oxide Powder
[0108] A BET specific surface area of a metal oxide powder was
measured by FLOWSORB-11 (manufactured by Micromelitics).
[0109] 5. Measurement of Primary Particle Size
[0110] A primary particle size d (.mu.m) was calculated according
to the formula of:
d=6/(S.times..rho.)
[0111] wherein S (m.sup.2/g) is a BET specific surface area of the
powder, and .rho. (g/cm.sup.3) is a density of the powder, provided
that the primary particle size d is a diameter of a particle with
the assumption that it were a sphere.
[0112] As the hydrogen chloride gas, bomb hydrogen chloride
(purity: 99.9%) supplied by Tsurumi Soda Co., Ltd. or a
decomposition gas of ammonium chloride (WAKO JUNYAKU, Special Grade
Chemical) was used. When the decomposition gas of ammonium chloride
was used, sublimation gas of ammonium chloride prepared by heating
ammonium chloride at a temperature higher than its sublimation
point was introduced in the furnace muffle to prepare the
atmosphere gas. Ammonium chloride was completely decomposed at
1100.degree. C. to provide a gas consisting of 33 vol. % of
hydrogen chloride gas, 17 vol. % of nitrogen gas and 50 vol. % of
hydrogen gas.
[0113] As the hydrogen bromide gas, a decomposition gas of ammonium
bromide (WAKO JUNYAKU, Special Grade Chemical) was used.
Sublimation gas of ammonium bromide prepared by heating ammonium
bromide at a temperature higher than its sublimation point was
introduced in the furnace muffle to prepare the atmosphere gas.
Ammonium bromide was completely decomposed at ad 1100.degree. C. to
provide a gas consisting of 33 vol. % of hydrogen bromide gas, 17
vol. % of nitrogen gas and 50 vol. % of hydrogen gas.
[0114] As the hydrogen fluoride gas, a decomposition gas of
ammonium fluoride (WAKO JUNYAKU, Special Grade Chemical) was used.
Sublimation gas of ammonium fluoride prepared by heating ammonium
fluoride at a temperature higher than its sublimation point was
introduced in the furnace muffle to prepare the atmosphere gas.
Ammonium fluoride was completely decomposed at 1100.degree. C. to
provide a gas consisting of 33 vol. % of hydrogen fluoride gas, 17
vol. % of nitrogen gas and 50 vol. % of hydrogen gas.
[0115] As the chloride gas, bomb chlorine gas (purity: 99.4%)
supplied by Fujimoto Industries, Co., Ltd.) was used.
[0116] The metal oxide power or the metal oxide precursor powder
was filled in an alumina or platinum vessel. When the halogen gas
was used, the powder was filled in the alumina vessel. A depth of
the filled powder was 5 mm. The calcination was carried out in a
cylindrical furnace having a quartz muffle or an alumina muffle
(manufactured by Motoyama Co., Ltd.). With flowing the nitrogen
gas, temperature was raised at a heating rate of from 300.degree.
C./hr. to 500.degree. C./hr., and when the temperature reached an
atmosphere gas introduction temperature, the atmosphere gas was
introduced.
[0117] A concentration of the atmosphere gas was adjusted by
controlling gas flow rates by flow meters. The flow rate of the
atmosphere was adjusted to a linear velocity of 20 mm/min. The
total pressure of the atmosphere was always 1 atmosphere.
[0118] After the temperature reached the predetermined temperature,
the powder was maintained at that temperature for a predetermined
period of time. They will be referred to as "maintaining
temperature" (calcination temperature) and "maintaining time"
(calcination time).
[0119] After the predetermined maintaining time, the powder was
spontaneously cooled to obtain the intended metal oxide powder.
[0120] The partial pressure of steam was adjusted by the change of
saturated steam pressure depending on water temperature, and the
steam was introduced in the furnace with the nitrogen gas.
Example 1
[0121] A metatitanic acid slurry (30 wt. % as reduced to titanium
oxide weight. A product obtained in an intermediate step of the
sulfuric acid method) was concentrated by an evaporator and then
dried in an air at 200.degree. C. to obtain raw material titanium
oxide powder. This powder had a BET specific surface area of 183
m.sup.2/g (a primary particle size calculated from the BET specific
surface area=0.008 .mu.m). According to the X-ray diffraction
analysis, the powder was found to be anatase type titanium oxide,
and no other peak was observed.
[0122] The raw material titanium oxide powder (1.2 g) was filled in
an alumina vessel. Its bulk density was 19% of the theoretical
density. Then, the powder was placed in the quartz muffle, and
heated from room temperature at a heating rate of 500.degree.
C./hr. while flowing the atmosphere gas consisting of 100 vol. % of
hydrogen chloride at a linear velocity of 20 mm/min., and calcined
at 1100.degree. C. for 30 minutes, followed by spontaneous cooling
to obtain a titanium oxide powder. The weight of the titanium oxide
powder in the alumina vessel after calcination was 85% of that of
the powder before calcination.
[0123] The obtained titanium oxide powder was the rutile type
titanium oxide according to the result of the X-ray diffraction
analysis, and no other peak was observed. The BET specific surface
area was 0.2 m.sup.2/g. According to the result of the observation
by the scanning electron microscope, the rutile type titanium oxide
consisted of polyhedral particles having 8 to 20 planes, and had
the number average particle size of 9 .mu.m. The agglomerated
particle size (D.sub.50) according to the particle size
distribution measurement was 14.2 .mu.m, and the D.sub.90/D.sub.10
ratio was 3, which indicated the narrow particle size distribution.
The ratio of the agglomerated particle size to the number average
particle size was 1.6.
[0124] The obtained particles were observed by a transmission
electron microscope. No defect was observed in the particles, and
it was found that the particle was a single crystal. The results
are shown in Table 1. An electron microscopic photograph of the
obtained rutile type titanium oxide is shown in FIG. 1.
Example 2
[0125] In the same manner as in Example 1 except that an atmosphere
gas consisting of 10 vol. % of hydrogen-chloride and 90 vol. % of
nitrogen was used in place of the atmosphere gas of 100 vol. %
hydrogen chloride, the rutile type titanium oxide was obtained. The
results are shown in Table 1.
Example 3
[0126] In the same manner as in Example 1 except that an atmosphere
gas consisting of 30 vol. % of hydrogen chloride, 10 vol. % of
steam and 60 vol. % of nitrogen was used in place of the atmosphere
gas of 100 vol. % hydrogen chloride, the rutile type titanium oxide
was obtained. The results are shown in Table 1.
Example 4
[0127] In the same manner as in Example 1 except that an atmosphere
gas consisting of 30 vol. % of hydrogen chloride and 70 vol. % of
an air was used in place of the atmosphere gas of 100 vol. %
hydrogen chloride, the rutile type titanium oxide was obtained. The
results are shown in Table 1.
Example 5
[0128] The raw material titanium oxide powder as used in Example 1
was filled in the alumina vessel and placed in the quartz muffle,
and heated at a heating rate of 500.degree. C./hr. When the
temperature reached 600.degree. C., the decomposed gas of
sublimated ammonium chloride was introduced, and the powder was
heated in the decomposed gas atmosphere at 1100.degree. C. for 30
minutes, followed by spontaneous cooling to obtain the rutile type
titanium oxide. At 1100.degree. C., the components of the
decomposed gas were hydrogen chloride gas, nitrogen and hydrogen,
and their volume ratio was 33:17:50. The results are shown in Table
1.
Example 6
[0129] In the same manner as in Example 5 except that ammonium
bromide was used in place of ammonium chloride, the rutile type
titanium oxide was obtained. At 1100.degree. C., the components of
the decomposed gas of ammonium bromide were hydrogen bromide gas,
nitrogen and hydrogen, and their volume ratio was 33:17:50. The
results are shown in Table 1.
Example 7
[0130] In the same manner as in Example 5 except that anatase type
titanium oxide (MC 90 manufactured by Ishihara Industries, Co.,
Ltd. The BET specific surface area of 104 m.sup.2/g, and the
primary particle size calculated from the BET specific surface
area=0.013 .mu.m) was used as the raw material oxide powder,
ammonium fluoride was used in place of ammonium chloride, and the
alumina muffle was used in place of the quartz muffle, the rutile
type titanium oxide was obtained. At 1100.degree. C., the
components of the decomposed gas of ammonium fluoride were hydrogen
fluoride gas, nitrogen and hydrogen, and their volume ratio was
33:17:50. The electron microscopic photograph of the obtained
rutile type titanium oxide is shown in FIG. 2. The results are
shown in Table 1.
Example 8
[0131] In the same manner as in Example 1 except that an atmosphere
gas consisting of 30 vol. % of chlorine, 10 vol. % of steam and 60
vol. % of nitrogen was used in place of the atmosphere gas of 100
vol. % hydrogen chloride, the rutile type titanium oxide was
obtained. The results are shown in Table 1.
Example 9
[0132] In the same manner as in Example 1 except that the anatase
type titanium oxide powder as used in Example 7 was used as the raw
material titanium oxide powder, and an atmosphere gas of 100 vol. %
of chlorine was used in place of the atmosphere gas of 100 vol. %
hydrogen chloride, the rutile type titanium oxide was obtained. The
results are shown in Table 1. The electron microscopic photograph
of the obtained rutile type titanium oxide powder is shown in FIG.
3.
Example 10
[0133] In the same manner as in Example 1 except that an atmosphere
gas of 100 vol. % of chlorine was used in place of the atmosphere
gas of 100 vol. % hydrogen chloride, the rutile type titanium oxide
was obtained. The results are shown in Table 1.
1 TABLE 1 Calcination conditions Gas Ex. Atmosphere gas (vol. %)
introduction Maintaining Maintaining No. Oxide HCl HBr HF Cl.sub.2
N.sub.2 H.sub.2O H.sub.2 Air temp. (.degree. C.) temp. (.degree.
C.) time (min.) 1 TiO.sub.2 100 Room temp. 1100 30 2 TiO.sub.2 10
90 Room temp. 1100 30 3 TiO.sub.2 30 60 10 Room temp. 1100 30 4
TiO.sub.2 30 70 Room temp. 1100 30 5 TiO.sub.2 33 17 50 600 1100 30
6 TiO.sub.2 33 17 50 600 1100 30 7 TiO.sub.2 33 17 50 600 1100 30 8
TiO.sub.2 30 60 10 Room temp. 1100 30 9 TiO.sub.2 100 Room temp.
1100 30 10 TiO.sub.2 100 Room temp. 1100 30 Number Particle size
distribution BET Number of average Agglomerated Ratio of D.sub.50
to specific planes of Ex. particle particle size No. Av. particle
surface area polyhedron No. size (.mu.m) D.sub.50 (.mu.m) size
D.sub.90/D.sub.10 (m.sup.2/g) particles 1 9 14.2 1.6 3 0.2 8-20 2 5
7.3 1.5 3 0.2 8-20 3 5 9.0 1.8 3 8-20 4 5 8.0 1.6 4 8-20 5 4 8-20 6
8 12 1.5 5 0.2 8-20 7 2 8-20 8 5 8-20 9 3.3 6.2 1.9 4 8-20 10 5
11.4 2.3 4 8-20
Example 11
[0134] In the same manner as in Example 1 except that metatitanic
acid TH-30 (trade name) manufactured by TEIKA Co., Ltd. was used as
the raw material powder, and the calcination temperature was
changed to 800.degree. C., the rutile type titanium oxide was
obtained. The results are shown in Table 2.
Example 12
[0135] In the same manner as in Example 1 except that an anatase
titanium oxide powder KA-10 (trade name) manufactured by Titanium
Industries Co., Ltd. was used as the raw material powder, and an
atmosphere gas consisting of 45 vol. % of hydrogen chloride, 45
vol. % of an air and 10 vol. % of steam was used, the rutile type
titanium oxide was obtained.
[0136] As the result of the observation using the scanning electron
microscope, it was found that the polyhedral particles having 8 to
20 planes were produced, the length of the primary particles was
about 10 .mu.m and the diameter was about 1 .mu.m. The agglomerated
particle size was 7.5 .mu.m. When the average value 6 .mu.m of the
average length and the average diameter of the primary particles
was employed as a number average particle size, the ratio of the
agglomerated particle size to the number average primary particle
size was 1.3. The results are shown in Table 2.
Example 13
[0137] To the raw material titanium oxide powder of Example 1
(10.00 g), a rutile type titanium oxide powder (TTO-55, a trade
name, manufactured by Titanium Industries Co., Ltd. A BET specific
surface area of 38.6 m.sup.2/g) (0.30 g corresponding to 3 wt. %)
was added as the seed crystal. The addition manner comprised
dispersing the raw material titanium oxide powder and the seed
crystal by ultrasonic in isopropanol to prepare a slurry and drying
the slurry with an evaporator and a vacuum drier.
[0138] In the same manner as in Example 1 except that the above raw
material titanium oxide powder containing the seed crystal was
used, the rutile titanium oxide was produced. The results are shown
in Table 2.
Example 14
[0139] To the raw material titanium oxide powder of Example 1, 3
wt. % of a high purity rutile powder (CR-EL manufactured by
Ishihara Industries Co., Ltd. A BET specific surface area of 6.8
m.sup.2/g. A primary particle size calculated from the BET specific
surface area=0.20 .mu.m) was added as the seed crystal. The
addition manner comprised dispersing the raw material titanium
oxide powder and the seed crystal were dispersed by ultrasonic in
isopropanol to prepare a slurry and drying the slurry with an
evaporator and a vacuum drier. This raw material titanium oxide
powder containing the seed crystal was filled in the alumina
vessel. Its bulk density was 19% of the theoretical value.
[0140] Then, the powder was placed in the quartz muffle, and heated
from room temperature at a heating rate of 500.degree. C./hr. while
flowing nitrogen gas. When the temperature reached 800.degree. C.,
the nitrogen gas was changed to an atmosphere gas of 100 vol. %
hydrogen chloride, and the powder was calcined at 1100.degree. C.
for 30 minutes while flowing the hydrogen chloride gas at a linear
velocity of 20 mm/min., followed by spontaneous cooling to obtain a
titanium oxide powder. The weight of the titanium oxide powder in
the alumina vessel after calcination was 85 wt. % of that of the
powder before calcination. The results are shown in Table 2.
Example 15
[0141] In the same manner as in Example 14 except that an
atmosphere gas consisting of 30 vol. % of hydrogen chloride and 70
vol. % of nitrogen was used in place of the atmosphere gas of 100
vol. % hydrogen chloride, the rutile type titanium oxide was
obtained. The results are shown in Table 2. The electron
microscopic photograph of the obtained rutile titanium oxide powder
is shown in FIG. 4.
Example 16
[0142] In the same manner as in Example 14 except that an
atmosphere gas consisting of 30 vol. % of chlorine and 70 vol. % of
an air was used in place of the atmosphere gas of 100 vol. %
hydrogen chloride, the rutile type titanium oxide was obtained. The
results are shown in Table 2.
Example 17
[0143] In the same manner as in Example 14 except that an
atmosphere gas consisting of 30 vol. % of hydrogen chloride, 10
vol. % of steam and 60 vol. % of nitrogen was used in place of the
atmosphere gas of 100 vol. % hydrogen chloride, the rutile type
titanium oxide was obtained. The results are shown in Table 2.
Example 18
[0144] In the same manner as in Example 14 except that an
atmosphere gas of 100 vol. % chlorine gas was used in place of the
atmosphere gas of 100 vol. % hydrogen chloride, the rutile type
titanium oxide was obtained. The results are shown in Table 2.
Example 19
[0145] In the same manner as in Example 18 except that an amount of
the seed crystal was changed to 1 wt. %, the rutile type titanium
oxide was obtained. The results are shown in Table 2.
Comparative Example 1
[0146] Using the same raw material and the furnace as used in
Example 1, the raw material powder was calcined in an air with
opening the both ends of the furnace. The raw material powder was
calcined at 1100.degree. C. for 180 minutes, followed by
spontaneous cooling to obtain a titanium oxide powder.
[0147] The obtained titanium oxide powder was analyzed by X-ray
diffraction to confirm that it was a rutile type titanium oxide. No
other peak was observed. The BET specific surface area was 1.5
m.sup.2/g. According to the observation of the powder by the
scanning electron microscope, no polyhedron particle was formed,
and spherical particles were in the agglomerated state, and their
number average particle size was 0.5 .mu.m.
[0148] The agglomerated particle size (D.sub.50) according to the
particle size distribution measurement was 1.5 .mu.m, and the
D.sub.90/D.sub.10 ratio was 21, which indicated the broad particle
size distribution. A ratio of the agglomerated particle size to the
number average particle size was 3. When the obtained particles
were observed by the scanning electron microscope, defects were
found in the particle, and the particle was not a single crystal.
The results are shown in Table 2. The scanning electron microscopic
photograph of the obtained rutile titanium oxide powder is shown in
FIG. 5.
Comparative Example 2
[0149] In the same manner as in Comparative Example 1 except that
the same raw material powder as used in Example 14 was used, the
rutile titanium oxide was obtained. The results are shown in Table
2.
2 TABLE 2 Calcination conditions Gas Ex. Atmosphere gas (vol. %)
introduction Maintaining Maintaining No. Oxide HCl HBr HF Cl.sub.2
N.sub.2 H.sub.2O H.sub.2 Air temp. (.degree. C.) temp. (.degree.
C.) time (min.) 11 TiO.sub.2 100 Room temp. 800 30 12 TiO.sub.2 45
10 45 Room temp. 1100 30 13 TiO.sub.2 100 Room temp. 1100 30 14
TiO.sub.2 100 800 1100 30 15 TiO.sub.2 30 70 800 1100 30 16
TiO.sub.2 30 70 800 800 30 17 TiO.sub.2 30 60 10 800 1100 30 18
TiO.sub.2 100 45 800 1100 30 19 TiO.sub.2 30 60 10 800 1100 30 C. 1
TiO.sub.2 100 Room temp. 1100 180 C. 2 TiO.sub.2 100 Room temp.
1100 180 Number Particle size distribution BET Number of average
Agglomerated Ratio of D.sub.50 to specific planes of Ex. particle
particle size No. Av. particle surface area polyhedron No. size
(.mu.m) D.sub.50 (.mu.m) size D.sub.90/D.sub.10 (m.sup.2/g)
particles 11 13 15.3 1.2 5 0.1 8-20 12 6 7.5 1.3 5 0.4 8-20 13 1
1.9 1.9 4 1.4 8-24 14 1.2 5.3 4.4 5 8-24 15 1.1 4.2 3.8 5 8-24 16
0.9 2.8 3.1 4 8-24 17 1.0 4.3 4.3 5 8-24 18 1.0 3.6 3.6 5 8-24 19
1.3 4.7 3.6 5 8-24 C. 1 0.5 1.5 3.0 21 Bulk C. 2 0.4 5.8 14.5 44
Bulk
Example 20
[0150] Zirconium oxychloride octahydrate (WAKO JUNYAKU, Special
Grade Chemical) (78.3 g) was dissolved in pure water (400 g) to
obtain an aqueous solution of a zirconium salt. In aqueous ammonia
(25 wt. %. WAKO JUNYAKU, Special Grade Chemical) contained in a 2
liter beaker, the above aqueous solution of the zirconium salt was
added over 2 hours while stirring to neutralize the salt and
coprecipitate them. The precipitate was filtered through a filter
paper and washed with pure water, followed by drying in vacuo at
100.degree. C. to obtain a zirconium oxide precursor powder. The
BET specific surface area of this precursor powder was 255
m.sup.2/g.
[0151] The zirconium oxide precursor powder was precalcined in the
air at 500.degree. C. to obtain a raw material powder.
[0152] According to the X-ray diffraction analysis, peaks assigned
to monoclinic zirconium oxide and tetragonal zirconium oxide were
observed. The BET specific surface area was 79.4 m.sup.2/g, and the
primary particle size calculated from the BET specific surface area
was 0.013 .mu.m.
[0153] The raw material powder was filled in a platinum vessel. Its
bulk density was 15% of the theoretical value.
[0154] Then, the powder was placed in the quartz muffle, and with
flowing an atmosphere gas of 100 vol. % hydrogen chloride at a
linear velocity of 20 mm/min., the powder was heated from room
temperature at a heating rate of 300.degree. C./hr., and calcined
at 1100.degree. C. for 60 minutes, followed by spontaneous cooling
to obtain a zirconium oxide powder. The weight of the zirconium
oxide powder in the platinum vessel after calcination was 95 wt. %
of that of the powder before calcination.
[0155] According to the X-ray diffraction analysis, the obtained
zirconium oxide powder was monoclinic zirconium oxide, and no other
peak was observed. According to the observation by the scanning
electron microscope, the polyhedral particles having 8 to 24 planes
each were formed, and the number average particle size was 12
.mu.m. The agglomerated particle size (D.sub.50) according to the
particle size distribution measurement was 15 .mu.m, and the
D.sub.90/D.sub.10 ratio was 3, which indicated the narrow particle
size distribution. A ratio of the agglomerated particle size to the
number average particle size was 1.3. The results are shown in
Table 3. The scanning electron microscopic photograph of the
obtained powder is shown in FIG. 6.
Example 21
[0156] Zirconium tetrachloride (Merk. Purity, 98%) (56.8 g) was
dissolved in pure water (500 g) to obtain an aqueous solution of a
zirconium salt. In pure water (760 g) contained in a 2 liter
beaker, the above aqueous solution of the zirconium salt was added
over 3 hours while stirring. During the addition, aqueous ammonium
(25 wt. %. WAKO JUNYAKU, Special Grade Chemical) was added with
maintaining pH constant at 4.0 with a pH controller (FC-10
manufactured by Tokyo Rika Kiki Co., Ltd.) to neutralize the salt
and obtain a precipitate. An amount of the added aqueous-ammonia
was 58.2 g. The precipitate was filtered through a filter paper and
washed with pure water, followed by drying in vacuo at 100.degree.
C. to obtain a zirconium oxide precursor powder. The BET specific
surface area of this precursor powder was 15 m.sup.2/g, and the
primary particle size calculated from the BET specific surface area
was 0.07 .mu.m.
[0157] The zirconium oxide precursor powder was calcined in the air
at 500.degree. C. to obtain a raw material powder.
[0158] According to the X-ray diffraction analysis, peaks assigned
to monoclinic zirconium oxide and tetragonal zirconium oxide were
observed. The BET specific surface area was 18.2 m.sup.2/g, and the
primary particle size calculated from the BET specific surface area
was 0.05 .mu.m.
[0159] The raw material powder was filled in a platinum vessel. Its
bulk density was 25% of the theoretical value.
[0160] Thereafter, the raw material powder was calcined in the same
manner as in Example 20 to obtain the zirconium oxide powder. The
weight of the zirconium oxide powder in the platinum vessel after
calcination was 95 wt. % of that of the powder before calcination.
The results are shown in Table 3. The electron microscopic
photograph of the obtained powder is shown in FIG. 7.
Example 22
[0161] As a raw material zirconium oxide powder, high purity
zirconia powder (ZP 20 manufactured by Chichibu Cement Co., Ltd. A
BET specific surface area=93 m.sup.2/g. A primary particle size
calculated from the BET specific surface area=0.01 .mu.m) was used.
To this raw material zirconium oxide powder, 2 wt. % of a powder
which was obtained by sintering the above zirconia powder in an air
at 1400.degree. C. for 3 hours and milling it in a ball mill (A BET
specific surface area=2.8 m.sup.2/g. A primary particle size
calculated from the BET specific surface area=0.36 .mu.m) was added
as a seed crystal. The addition manner comprised dispersing the raw
material zirconium oxide powder and the seed crystal by ultrasonic
in isopropanol to prepare a slurry and drying the slurry with an
evaporator and a vacuum drier.
[0162] The raw material powder containing the seed crystal was
filled in a platinum vessel. Its bulk density was 25% of the
theoretical value.
[0163] Thereafter, the raw material powder was calcined in the same
manner as in Example 20 to obtain the zirconium oxide powder. The
results are shown in Table 3. The electron microscopic photograph
of the obtained zirconium oxide powder is shown in FIG. 8.
Comparative Example 3
[0164] In the same manner as in Example 20 except that an
atmosphere gas of 100 vol. % air was used in place of the
atmosphere gas of 100 vol. % hydrogen chloride, the zirconium oxide
powder was obtained. According to the observation by the scanning
electron microscope, no polyhedron particle was formed, and the
spherical particles were in the agglomerated state, and their
number average particle size was 0.2 .mu.m.
[0165] The agglomerated particle size (D.sub.50) according to the
particle size distribution measurement was 11 .mu.m, and the
D.sub.90/D.sub.10 ratio was 22, which indicated the broad particle
size distribution. A ratio of the agglomerated particle size to the
number average particle size was 55. The results are shown in Table
3. The scanning electron microscopic photograph of the obtained
zirconium oxide powder is shown in FIG. 9.
Comparative Example 4
[0166] In the same manner as in Comparative Example 3 except that
the raw material powder of Example 22 but containing no seed
crystal was used, the zirconium oxide powder was obtained. The
results are shown in Table 3.
Comparative Example 5
[0167] In the same manner as in Comparative Example 3 except that
the raw material powder of Example 22 containing the seed crystal
was used, the zirconium oxide powder was obtained. The results are
shown in Table 3.
Example 23
[0168] As a raw material powder, a magnesium oxide powder having
the BET specific surface area of 132 m.sup.2/g (A primary particle
size calculated from the BET specific surface area=0.01 .mu.m) was
used and filled in a platinum vessel. Its bulk density was 2% of
the theoretical value.
[0169] Then, the powder was placed in the quartz muffle, and with
flowing nitrogen gas at a linear velocity of 20 mm/min., the powder
was heated from room temperature at a heating rate of 300 AC/hr.
When the temperature reached 800.degree. C., the nitrogen gas was
changed to an atmosphere gas of 100 vol. % hydrogen chloride. While
flowing this atmosphere gas at a linear velocity of 20 mm/min., the
powder was calcined at 1000.degree. C. for 30 minutes, followed by
spontaneous cooling to obtain a magnesium oxide powder.
[0170] According to the observation by the scanning electron
microscope, the polyhedral particles having 8 to 24 planes were
formed, and the number average particle size was 30 .mu.m. The
results are shown in Table 3. The scanning electron microscopic
photograph of the magnesium oxide powder is shown in FIG. 10.
Example 24
[0171] To the raw material magnesium oxide powder of Example 23,
0.1 wt. % of a magnesium oxide powder having the BET specific
surface area of 8.0 m.sup.2/g (the primary particle size calculated
from the BET specific surface area=0.20 .mu.m) was added as a seed
crystal.
[0172] The addition manner comprised dispersing the raw material
magnesium oxide powder and the seed crystal by ultrasonic in
isopropanol to prepare a slurry and drying the slurry with an
evaporator and a vacuum drier. The raw material magnesium oxide
powder containing the seed crystal was filled in the platinum
vessel. Its bulk density was 3% of the theoretical value.
Thereafter, in the same manner as in Example 23, the magnesium
oxide powder was obtained.
[0173] According to the observation by the scanning electron
microscope, the number average particle size was 8 .mu.m. The
agglomerated particle size (D.sub.50) according to the particle
size distribution measurement was 11 .mu.m, and the
D.sub.90/D.sub.10 ratio was 3, which indicated the narrow particle
size distribution. A ratio of the agglomerated particle size to the
number average particle size was 1.4. The results are shown in
Table 3. The scanning electron microscopic photograph of the
obtained powder is shown in FIG. 11.
Example 25
[0174] In the same manner as in Example 24 except that the amount
of the seed crystal was changed to 3 wt. %, the magnesium oxide
powder was obtained. The results are shown in Table 3. The scanning
electron microscopic photograph of the obtained zirconium oxide
powder is shown in FIG. 12.
Comparative Example 6
[0175] In the same manner as in Example 23 except that the
atmosphere gas of 100 vol. % air was supplied from the room
temperature in place of the atmosphere gas of 100 vol. % hydrogen
chloride, the magnesium oxide powder was obtained. According to the
observation by the scanning electron microscope, no polyhedral
particle was formed, spherical particles were in the agglomerated
state, and the number average particle size was 0.4 .mu.m. The
agglomerated particle size (D.sub.50) according to the particle
size distribution measurement was 1 .mu.m, and the
D.sub.90/D.sub.10 ratio was 17, which indicated the broad particle
size distribution. The results are shown in Table 3. The scanning
electron microscopic photograph of the obtained magnesium oxide
powder is shown in FIG. 13.
Comparative Example 7
[0176] In the same manner as in Comparative Example 6 except that
the raw material powder of Example 25 was used, the magnesium oxide
powder was obtained. The results are shown in Table 3.
3 TABLE 3 Calcination conditions Gas Ex. Atmosphere gas (vol. %)
introduction Maintaining Maintaining No. Oxide HCl HBr HF Cl.sub.2
N.sub.2 H.sub.2O H.sub.2 Air temp. (.degree. C.) temp. (.degree.
C.) time (min.) 20 ZrO.sub.2 100 Room temp. 1100 60 21 ZrO.sub.2
100 Room temp. 1100 60 22 ZrO.sub.2 100 Room temp. 1100 60 C. 3
ZrO.sub.2 100 Room temp. 1100 60 C. 4 ZrO.sub.2 100 Room temp. 1100
60 C. 5 ZrO.sub.2 100 Room temp. 1100 60 23 MgO 100 800 1000 30 24
MgO 100 800 1000 30 25 MgO 100 800 1000 30 C. 6 MgO 100 Room temp.
1000 60 C. 7 MgO 100 Room temp. 1000 30 Number Particle size
distribution BET Number of average Agglomerated Ratio of D.sub.50
to specific planes of Ex. particle particle size No. Av. particle
surface area polyhedron No. size (.mu.m) D.sub.50 (.mu.m) size
D.sub.90/D.sub.10 (m.sup.2/g) particles 20 12 15 1.3 3 8-24 21 40
59 1.5 5 8-24 22 10 19 1.9 4 8-24 C. 3 0.2 11 55 22 Bulk C. 4 0.2
11 55 22 Bulk C. 5 0.2 15 77 52 Bulk 23 30 8-24 24 8 11 1.4 3 8-24
25 4 6 1.5 4 8-24 C. 6 0.4 1 2.5 17 Bulk C. 7 0.2 5 23 11 Bulk
Example 26
[0177] Gamma iron (III) oxide (A BET specific surface area of 34.4
m.sup.2/g. A primary particle size calculated from the BET specific
surface area of 0.03 .mu.m) was filled in a platinum vessel. Its
bulk density was 16% of the theoretical value.
[0178] Then, the powder was placed in the quartz muffle, and with
flowing nitrogen gas at a linear velocity of 20 mm/min., the powder
was heated from room temperature at a heating rate of 300.degree.
C./hr. When the temperature reached 600.degree. C., the nitrogen
gas was changed to an atmosphere gas of 100 vol. % hydrogen
chloride. While flowing this atmosphere gas at a linear velocity of
20 mm/min., the powder was calcined at 800.degree. C. for 30
minutes, followed by spontaneous cooling to obtain an iron oxide
powder. The weight of the iron oxide powder in the platinum vessel
was 92% of that of the powder before calcination.
[0179] According to the X-ray diffraction analysis, the obtained
iron oxide powder was alpha iron (III) oxide, and no other peak was
observed.
[0180] According to the observation by the scanning electron
microscope, the polyhedral particles having 8 to 20 planes were
formed, and the number average particle size was 5 .mu.m. The
agglomerated particle size (D.sub.50) according to the particle
size distribution measurement was 6 .mu.m, and the
D.sub.90/D.sub.10 ratio was 4, which indicated the narrow particle
size distribution. The ratio of the agglomerated particle size to
the number average particle size was 1.3. The results are shown in
Table 4. The scanning electron microscopic photograph of the
obtained alpha iron (III) oxide powder is shown in FIG. 14.
Comparative Example 8
[0181] In the same manner as in Example 26 except that an
atmosphere gas of 100 vol. % air was supplied from the room
temperature in place of the atmosphere gas of 100 vol. % hydrogen
chloride, the alpha iron (III) oxide powder was obtained.
[0182] According to the observation by the scanning electron
microscope, no polyhedral particle was formed, the spherical
particles were in the agglomerated state, and their number average
particle size was 0.2 .mu.m. The agglomerated particle size
(D.sub.50) according to the particle size distribution measurement
was 7 .mu.m, and the D.sub.90/D.sub.10 ratio was 100, which
indicated the narrow particle size distribution. The ratio of the
agglomerated particle to the number average particle size was 35.
The results are shown in Table 4. The scanning electron microscopic
photograph of the obtained alpha iron (III) oxide powder is shown
in FIG. 15.
Example 27
[0183] Cerium (IV) sulfate (WAKO JUNYAKU, Special Grade Chemical)
(100 g) was dissolved in pure water (900 g) to obtain an aqueous
solution of a cerium (IV) sulfate. To this aqueous solution, a 2N
aqueous solution of sodium hydroxide (WAKO JUNYAKU, Special Grade
Chemical) was added till pH reached 10 to neutralize the solution
and precipitate the salt. The precipitate was separated by
centrifugation and stirred in pure water. These procedures were
repeated several times to wash the precipitate with water. The
precipitate washed with water was dried at 120.degree. C. to obtain
a cerium oxide precursor powder. According to the X-ray diffraction
analysis, a broad peak assigned to cubic system cerium oxide was
observed. The BET specific surface area of this precursor powder
was 208.7 m.sup.2/g, and the primary particle size calculated from
the BET specific surface area was 0.004 .mu.m.
[0184] The cerium oxide precursor powder was filled in a platinum
vessel. Then, it was placed in the quartz muffle, and with flowing
an air at a linear velocity of 20 mm/min., the powder was heated
from room temperature at a heating rate of 300.degree. C./hr. When
the temperature reached 400.degree. C., the air was changed to an
atmosphere gas of 100 vol. % hydrogen chloride. While flowing this
atmosphere gas at a linear velocity of 20 mm/min., the powder was
calcined at 1100.degree. C. for 60 minutes, followed by spontaneous
cooling to obtain a cerium oxide powder.
[0185] According to the X-ray diffraction analysis, the obtained
iron oxide powder was cubic system cerium oxide, and no other peak
was observed.
[0186] According to the observation by the scanning electron
microscope, the polyhedral particles having 6 planes, that is, the
cubic particles were formed, and the number average particle size
was 1.5 .mu.m. The results are shown in Table 4. The scanning
electron microscopic photograph of the obtained powder is shown in
FIG. 16.
Comparative Example 9
[0187] In the same manner as in Example 27 except that, as an
atmosphere gas, an air was used in place of hydrogen chloride, the
cerium oxide powder was obtained.
[0188] According to the observation by the scanning electron
microscope, no polyhedral particle was formed, and the spherical
particles were in the agglomerated state. The results are shown in
Table 4. The scanning electron microscopic photograph of the
obtained cerium oxide powder is shown in FIG. 17.
Example 28
[0189] As a raw material powder, a metastannic acid powder (Nippon
Chemical Industries Co., Ltd. A BET specific surface area=75.4
m.sup.2/g) was used.
[0190] The metastannic acid powder was filled in an alumina vessel.
Then, it was placed in the quartz muffle, and with flowing an air
at a linear velocity of 20 mm/min., the powder was heated from room
temperature at a heating rate of 300.degree. C./hr. When the
temperature reached 600.degree. C., the air was changed to an
atmosphere gas consisting of 50 vol. % of hydrogen chloride and 50
vol. % of the air. While flowing this atmosphere gas at a linear
velocity of 20 mm/min., the powder was calcined at 1050.degree. C.
for 60 minutes, followed by spontaneous cooling to obtain a tin
oxide powder.
[0191] According to the X-ray diffraction analysis, the obtained
tin oxide powder was tin dioxide, and no other peak was observed. a
According to the observation by the scanning electron microscope,
the polyhedral particles having 8 to 24 planes were formed, and the
number average particle size was 0.4 .mu.m. The results are shown
in Table 4. The scanning electron microscopic photograph of the
obtained powder is shown in FIG. 18.
Comparative Example 10
[0192] In the same manner as in Example 28 except that, as an
atmosphere gas, an air was used in place of hydrogen chloride, the
tin oxide powder was obtained.
[0193] According to the observation by the scanning electron
microscope, no polyhedral particle was formed, and the spherical
particles were in the agglomerated state. The results are shown in
Table 4. The scanning electron microscopic photograph of the
obtained powder is shown in FIG. 19.
Example 29
[0194] Indium (III) chloride tetrahydrate(WAKO JUNYAKU, Special
Grade Chemical) (14.67 g) was dissolved in pure water to obtain an
aqueous solution of indium (Ill) sulfate (100 g). To this aqueous
solution, a 1N aqueous ammonia (25% aqueous ammonia. WAKO JUNYAKU.
Prepared by diluting Special Grade Chemical with pure water) was
added till pH reached 8 to neutralize the solution and precipitate
the salt. The precipitate was separated by filtration and stirred
in pure water. These procedures were repeated several times to wash
the precipitate with water. The precipitate washed with water was
dried at 130.degree. C. to obtain an indium oxide precursor
powder.
[0195] According to the X-ray diffraction analysis, peaks assigned
to indium hydroxide and indium oxyhydroxide were observed. The BET
specific surface area of this precursor powder was 70.4
m.sup.2/g.
[0196] The indium oxide precursor powder was filled in an alumina
vessel. Then, it was placed in the quartz muffle, and with flowing
an air at a linear velocity of 20 mm/min., the powder was heated
from room temperature at a heating rate of 600.degree. C./hr. When
the temperature reached 1000.degree. C., the air was changed to an
atmosphere gas consisting of 20 vol. % of hydrogen chloride and 80
vol. % of the air. While flowing this atmosphere gas at a linear
velocity of 20 mm/min., the powder was calcined at 1000.degree. C.
for 30 minutes, followed by spontaneous cooling to obtain a cerium
oxide powder.
[0197] According to the X-ray diffraction analysis, the obtained
indium oxide powder was indium oxide, and no other peak was
observed. The results are shown in Table 4. The scanning electron
microscopic photograph of the obtained powder is shown in FIG.
20.
Comparative Example 11
[0198] In the same manner as in Example 29 except that, as an
atmosphere gas, an air was used in place of hydrogen chloride, the
indium oxide powder was obtained.
[0199] The results are shown in Table 4. The scanning electron
microscopic photograph of the obtained cerium oxide powder is shown
in FIG. 21.
4 TABLE 4 Calcination conditions Gas Ex. Atmosphere gas (vol. %)
introduction Maintaining Maintaining No. Oxide HCl HBr HF Cl.sub.2
N.sub.2 H.sub.2O H.sub.2 Air temp. (.degree. C.) temp. (.degree.
C.) time (min.) 26 Fe.sub.2O.sub.3 100 600 800 30 C. 8
Fe.sub.2O.sub.3 100 Room temp. 800 90 27 CeO.sub.2 100 400 1100 60
C. 9 CeO.sub.2 100 Room temp. 1100 60 28 SnO.sub.2 50 50 600 1050
60 C. 10 Sno.sub.2 100 Room temp. 1000 60 29 In.sub.2O.sub.3 20 80
1000 1000 30 C. 11 In.sub.2O.sub.3 100 Room temp. 1000 30 Number
Particle size distribution BET Number of average Agglomerated Ratio
of D.sub.50 to specific planes of Ex. particle particle size No.
Av. particle surface area polyhedron No. size (.mu.m) D.sub.50
(.mu.m) size D.sub.90/D.sub.10 (m.sup.2/g) particles 26 5 6 1.3 4
8-20 C. 8 0.2 7 35 100 Bulk 27 1.5 6 C. 9 0.2 8 40 150 Bulk 28 0.4
8-24 C. 10 <0.1 Bulk 29 0.2 8-24 C. 11 <0.1 Bulk
* * * * *