CA1208414A - Process for the preparation of ceramic powders - Google Patents
Process for the preparation of ceramic powdersInfo
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- CA1208414A CA1208414A CA000455796A CA455796A CA1208414A CA 1208414 A CA1208414 A CA 1208414A CA 000455796 A CA000455796 A CA 000455796A CA 455796 A CA455796 A CA 455796A CA 1208414 A CA1208414 A CA 1208414A
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Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G25/00—Compounds of zirconium
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
- C01B13/14—Methods for preparing oxides or hydroxides in general
- C01B13/32—Methods for preparing oxides or hydroxides in general by oxidation or hydrolysis of elements or compounds in the liquid or solid state or in non-aqueous solution, e.g. sol-gel process
- C01B13/328—Methods for preparing oxides or hydroxides in general by oxidation or hydrolysis of elements or compounds in the liquid or solid state or in non-aqueous solution, e.g. sol-gel process by processes making use of emulsions, e.g. the kerosine process
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G25/00—Compounds of zirconium
- C01G25/02—Oxides
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/48—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zirconium or hafnium oxides, zirconates, zircon or hafnates
- C04B35/486—Fine ceramics
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/50—Solid solutions
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/02—Particle morphology depicted by an image obtained by optical microscopy
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/10—Solid density
Abstract
ABSTRACT
Sub-micron sized powders of the ceramic metal oxides such as zirconia, alumina, titania, etc. are produced by precipitation from substantially anhydrous solutions of salts of the corresponding metal(s) with substantially anhydrous solutions of alkali metal hydroxides. The precipitates are subsequently washed with water to remove any residual soluble salt and/or solvent, then are dried and usually calcined. The powders thus produced are readily sintered to high density ceramic bodies after conventional pressing into the desired shape.
The process is especially suited to the produc-tion of zirconia powders, either pure or doped with conventional stabilizing oxides such as yttria.
In a typical example, a zirconia powder doped with 5.4%
by weight of yttria is prepared by adding a solution of zirconium tetrachloride and yttrium chloride in anhy-drous ethanol to a solution of sodium hydroxide in anhydrous ethanol. After washing, drying at 105°C, and calcining at 500°C for two hours, the powder is pressed at 5000 psi into a green body with a density of 1.46 Mg/m3. After one hour of sintering at 1600°C, the fired body has a density of 5.84 Mg/m3, which is 96%
of the theoretical maximum.
Sub-micron sized powders of the ceramic metal oxides such as zirconia, alumina, titania, etc. are produced by precipitation from substantially anhydrous solutions of salts of the corresponding metal(s) with substantially anhydrous solutions of alkali metal hydroxides. The precipitates are subsequently washed with water to remove any residual soluble salt and/or solvent, then are dried and usually calcined. The powders thus produced are readily sintered to high density ceramic bodies after conventional pressing into the desired shape.
The process is especially suited to the produc-tion of zirconia powders, either pure or doped with conventional stabilizing oxides such as yttria.
In a typical example, a zirconia powder doped with 5.4%
by weight of yttria is prepared by adding a solution of zirconium tetrachloride and yttrium chloride in anhy-drous ethanol to a solution of sodium hydroxide in anhydrous ethanol. After washing, drying at 105°C, and calcining at 500°C for two hours, the powder is pressed at 5000 psi into a green body with a density of 1.46 Mg/m3. After one hour of sintering at 1600°C, the fired body has a density of 5.84 Mg/m3, which is 96%
of the theoretical maximum.
Description
Docket P-1871 PROCESS FOR THE PREPARATION OF CER~MIC POWDERS
BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to the production of uniform sub-micron size ceramic powders suitable for sintering after pressing to give solid ceramic bodies of near-theoretical density. The invention is particu-larly applicable to the production of such powders of pure zirconia and of 2irconia doped with known stabi-lizing oxides such as yttria, but it is also applicable to production of sub-micron sized powders of alumina, silica, titania, and mixtures of these with a variety of other oxides.
Description of the Prior Art The most common method for the production of sub-micron sized powders of the ceramic oxides is precipitation or co-precipitation of an oxide precursor from aqueous solution of a salt of the metal or metals to be used~ Commonly, oxides, hydroxides, oxycar~on-ates, oxalates, etc., all usually with varying degrees of hydration~ are precipitated at an appropriate pH~
In all these cases, the precipitate normally has the form of a gel, which presents serious practical pro-cessing problems:
First, filtration is very difficult because of clogging of the pores of the filter. Second, desalting of the gel by washing is very tedious as a result of the filtration problem; moreover, gradual peptization of the gel to sol results from the gradual drop in elec-trolyte concentration induced by washing and worsens the fil~ration problem still further. Third, oven drying of the purified gel often yields unsinterable powders. (The worst adverse effects of drying can be avoided by replacing the water in the gel with an organic liquid before drying, but this requires exten-sive and expensive refluxing with the organic liquid in most cases and still produces powders with less than optimal sinterability.) Other established prior art method for the production of sinterable zirconia powders include high temperature oxidation of zirconium chloride with oxygen and/or water vapor, hydrolysis or thermal decomposition of zirconium alkoxides, and hydrothermal reaction of ~irconium metal or its alloys. These methods, however, require complex and expensive e~uipment and/or expen-sive starting materials and thus find relatively little industrial use.
The recent U. S. Patent 4,365,011 to Bernard et al. discloses an alternative precipitation method for the preparation of sinterable zirconia powders.
According to the Bernard tPaching, a solution of appropriate metal salt precursors is formed in alcohol rather than in water. A precipitate is formed by the action of ammonia on such a solution; the precipitate is washed with a hydrophilic solvent to eliminate most 3L2~
residual water, dried, and calcined. The drying step is preferably accomplished by azeotropic distillation with a third solvent such as benzene which is capable of displacing both water and the alcohol used. From this and other indications in the Bernard specifica-tion, I have concluded that the precipitate formed according to their teachings is a gel, and therefore is subject to all the processing difficulties for gels described above.
SUMMARY OF THE INVENTION
I have discovered that a precipitate well suited to eventual conversion to ceramic bodies by sintering can be formed in alcoholic or other organic solvents without any evidence of gellation and the processing difficulties associated therewith. This result is achieved by the preparation of separate solutions in organic solvent of soluble salts of the metal or metals desired in the final ceramic powders and of substan-tially anhydrous alkali metal hydroxides, then adding the soluticn of the ceramic metal compounds to that of the hydroxides. A precipitate of a precursor of the ceramic oxide, usually mixed with an alkali metal salt which is also relatively insoluble in the organic solvent used, is quickly formed and may be separated from the solvent by any conventional means, such as filtration, centrifugation, or the like. The separated precipitate is then dried to remove substantially all of the organic solvent. Any undesirable residual salt may be removed by washing the dried precipitate with water, preferably hot, without the processing diffi-culties associated with gellation which are experienced ~2~8~
when the precipitate is formed in the presence of more water. Washing with water is obviously more economical than washing with organic solvents as is required b~
the Bernard teachings.
The precipitate thus produced is dried at a temperature slightly above the boiling point of water, and is then usually calcined at a temperature of a few hundred degrees Celsius to remove adsorbed and otherwise physically bound water and/or organic solvent without impairing sinterability of the powder.
BRIEF DESCRIPTION OF THE DRAWINGS
The figures are photomicrographs made with a scanning electron microscope of the powders prepared according to this invention.
Figure 1 illustrates zirconia powder prepared according to the invention, dried in an oven at a 105C;
Figure 2 shows zirconia powder containing 5 n 4 w/O
yttrium oxide prepared according to the invention and dried in an oven at 105C;
Figure 3 shows zirconia powder containing 5.4 wjo yttrium oxide, dried in an o~en at 105C and subsequently calcined one hour in air at 500C;
Figure 4 shows a polished thermally etched section of a sintered disc of zirconia containing 5.4 w/o yttrium oxide, powder calcined at 500C, disc pressed at 34 MPa, sintered in air, one hour at 1600C;
Figure 5 i~ a view similar to Figure 4 where powder supplied by Toyo-Soda Co~, Japan is used as a receiver;
Figure 6 is a view similar to Figures 4 and 5 where powder is supplied by ZIRCAR Corp., Florida, New York used as a receiver; and Figure 7 is a view similar to Figures 4 through 6 buk shows a thermally etched section of a disc of 2irconia containing 12 w/o yttrium oxide, powder supplied by ZIRCAR 5 Corp., Florida, New York used as a receiver.
~84~
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The organic solvent which I have found mostsuitable for the practice of my invention is com~ercial anhydrous ekhanol. Commercial anhydrous methanol was also suitable. Other alcohols, ketones and other organic solvents may also be used, alone or in mix-tures.
My preferred source of zirconium in solution was zirconium tetrachloride, which is readily soluble in ethancl. Yttrium chloride hexahydrate was used as the primary source of yttrium in alcohol solution~ Yttrium nitrcte can also be used. In general, any salt of the desired metal or metals with adequate solubility in the desired solvent and without adverse interactions with the other metal salts in the same solution may be used.
When articles pximarily of zirconia are to be prepared, it is normally advantagPous, as generally -4a-known in the art, to add small amounts of yttrium, magnesium, calcium, or other known stabilizing oxides to promote the crystallization of zirconia in the cubic phase. This applies to the powders prepared by the methods of my invention as it does to those prepared by other means, except that calcium hydroxide, which is slightly soluble in water, is likely to be partially leached from the precipitate by washing~
Primarily because of its relatively low cost, sodium hydroxide is my preferred source of hydroxide ions for use in the precipitation. However, other hydroxides which are suf~iciently soluble in the solvent to be used would be expected to work as well.
The am~unt of water in the hydroxide should be no more than 2% by weight, and less is preferable. The amount of hydroxide used is preferably that ~ust sufficient stoichiometrically to accomplish the precipitation of the m~tal salts used as hydroxides.
After precipitation of the powders according to
BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to the production of uniform sub-micron size ceramic powders suitable for sintering after pressing to give solid ceramic bodies of near-theoretical density. The invention is particu-larly applicable to the production of such powders of pure zirconia and of 2irconia doped with known stabi-lizing oxides such as yttria, but it is also applicable to production of sub-micron sized powders of alumina, silica, titania, and mixtures of these with a variety of other oxides.
Description of the Prior Art The most common method for the production of sub-micron sized powders of the ceramic oxides is precipitation or co-precipitation of an oxide precursor from aqueous solution of a salt of the metal or metals to be used~ Commonly, oxides, hydroxides, oxycar~on-ates, oxalates, etc., all usually with varying degrees of hydration~ are precipitated at an appropriate pH~
In all these cases, the precipitate normally has the form of a gel, which presents serious practical pro-cessing problems:
First, filtration is very difficult because of clogging of the pores of the filter. Second, desalting of the gel by washing is very tedious as a result of the filtration problem; moreover, gradual peptization of the gel to sol results from the gradual drop in elec-trolyte concentration induced by washing and worsens the fil~ration problem still further. Third, oven drying of the purified gel often yields unsinterable powders. (The worst adverse effects of drying can be avoided by replacing the water in the gel with an organic liquid before drying, but this requires exten-sive and expensive refluxing with the organic liquid in most cases and still produces powders with less than optimal sinterability.) Other established prior art method for the production of sinterable zirconia powders include high temperature oxidation of zirconium chloride with oxygen and/or water vapor, hydrolysis or thermal decomposition of zirconium alkoxides, and hydrothermal reaction of ~irconium metal or its alloys. These methods, however, require complex and expensive e~uipment and/or expen-sive starting materials and thus find relatively little industrial use.
The recent U. S. Patent 4,365,011 to Bernard et al. discloses an alternative precipitation method for the preparation of sinterable zirconia powders.
According to the Bernard tPaching, a solution of appropriate metal salt precursors is formed in alcohol rather than in water. A precipitate is formed by the action of ammonia on such a solution; the precipitate is washed with a hydrophilic solvent to eliminate most 3L2~
residual water, dried, and calcined. The drying step is preferably accomplished by azeotropic distillation with a third solvent such as benzene which is capable of displacing both water and the alcohol used. From this and other indications in the Bernard specifica-tion, I have concluded that the precipitate formed according to their teachings is a gel, and therefore is subject to all the processing difficulties for gels described above.
SUMMARY OF THE INVENTION
I have discovered that a precipitate well suited to eventual conversion to ceramic bodies by sintering can be formed in alcoholic or other organic solvents without any evidence of gellation and the processing difficulties associated therewith. This result is achieved by the preparation of separate solutions in organic solvent of soluble salts of the metal or metals desired in the final ceramic powders and of substan-tially anhydrous alkali metal hydroxides, then adding the soluticn of the ceramic metal compounds to that of the hydroxides. A precipitate of a precursor of the ceramic oxide, usually mixed with an alkali metal salt which is also relatively insoluble in the organic solvent used, is quickly formed and may be separated from the solvent by any conventional means, such as filtration, centrifugation, or the like. The separated precipitate is then dried to remove substantially all of the organic solvent. Any undesirable residual salt may be removed by washing the dried precipitate with water, preferably hot, without the processing diffi-culties associated with gellation which are experienced ~2~8~
when the precipitate is formed in the presence of more water. Washing with water is obviously more economical than washing with organic solvents as is required b~
the Bernard teachings.
The precipitate thus produced is dried at a temperature slightly above the boiling point of water, and is then usually calcined at a temperature of a few hundred degrees Celsius to remove adsorbed and otherwise physically bound water and/or organic solvent without impairing sinterability of the powder.
BRIEF DESCRIPTION OF THE DRAWINGS
The figures are photomicrographs made with a scanning electron microscope of the powders prepared according to this invention.
Figure 1 illustrates zirconia powder prepared according to the invention, dried in an oven at a 105C;
Figure 2 shows zirconia powder containing 5 n 4 w/O
yttrium oxide prepared according to the invention and dried in an oven at 105C;
Figure 3 shows zirconia powder containing 5.4 wjo yttrium oxide, dried in an o~en at 105C and subsequently calcined one hour in air at 500C;
Figure 4 shows a polished thermally etched section of a sintered disc of zirconia containing 5.4 w/o yttrium oxide, powder calcined at 500C, disc pressed at 34 MPa, sintered in air, one hour at 1600C;
Figure 5 i~ a view similar to Figure 4 where powder supplied by Toyo-Soda Co~, Japan is used as a receiver;
Figure 6 is a view similar to Figures 4 and 5 where powder is supplied by ZIRCAR Corp., Florida, New York used as a receiver; and Figure 7 is a view similar to Figures 4 through 6 buk shows a thermally etched section of a disc of 2irconia containing 12 w/o yttrium oxide, powder supplied by ZIRCAR 5 Corp., Florida, New York used as a receiver.
~84~
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The organic solvent which I have found mostsuitable for the practice of my invention is com~ercial anhydrous ekhanol. Commercial anhydrous methanol was also suitable. Other alcohols, ketones and other organic solvents may also be used, alone or in mix-tures.
My preferred source of zirconium in solution was zirconium tetrachloride, which is readily soluble in ethancl. Yttrium chloride hexahydrate was used as the primary source of yttrium in alcohol solution~ Yttrium nitrcte can also be used. In general, any salt of the desired metal or metals with adequate solubility in the desired solvent and without adverse interactions with the other metal salts in the same solution may be used.
When articles pximarily of zirconia are to be prepared, it is normally advantagPous, as generally -4a-known in the art, to add small amounts of yttrium, magnesium, calcium, or other known stabilizing oxides to promote the crystallization of zirconia in the cubic phase. This applies to the powders prepared by the methods of my invention as it does to those prepared by other means, except that calcium hydroxide, which is slightly soluble in water, is likely to be partially leached from the precipitate by washing~
Primarily because of its relatively low cost, sodium hydroxide is my preferred source of hydroxide ions for use in the precipitation. However, other hydroxides which are suf~iciently soluble in the solvent to be used would be expected to work as well.
The am~unt of water in the hydroxide should be no more than 2% by weight, and less is preferable. The amount of hydroxide used is preferably that ~ust sufficient stoichiometrically to accomplish the precipitation of the m~tal salts used as hydroxides.
After precipitation of the powders according to
2~ this invention and subsequent drying, the powder should be thoroughly washed to remove not only any salt, but any residual organic solvent, which may oth~rwise be converted to objectionable carbon residue on calcina-tion. If the calcination is to be carried out in vacuum or in flowing oxygen, more solvent residue can be tolerated after washing, as it will be more readily removed during calcination.
For sintering, a little carbon can be tolerated because it will be converted to fugitive gases at a sufficiently low temperature so that it can escape through the remaining open pore structure of the 8~
incompletely sintered body. Larger amounts may give rise to retention in the final sintered body, however, and such retention is generally undesirable.
Although the description has been given primarily in terms of the preparation of zirconia powders, it should be understood that it is equally applicable to the preparation of powders of silica, titania, alumina, and many other oxides and mixtures thereof.
The invention may be illustrated by the following examples:
Example 1: Preparation of Undoped_Zirconia Twenty grams of ZrCl4 powder (99.6% purity product of Alfa Products) was dissolved in about 500 ml of anhydrous ethanol ~Baker Analyzed Reagent Grade~ to form the first solution. The second solution consisted of 13.7 gm of NaOH (Baker Analyzed Reagent Grade) pellets dissolved in about 500 ml of the same alcohol.
The first solution was poured slowly into the second, with constant stirring. A very fine precipi-tate formed very rapidly and slowly settled to give aclear supernatant liquid. The li~uid was decanted and the precipitate dried in a stainless steel pan on a laboratory hot plate. The dried powder was then washed with distilled water until no chloride ions were detectable in the wash water when it was tested with a nitric acid solution saturated with silver nitrate.
The powder was then dried a~ about 105~C in an oven, and then subjected to examination with a scanning electron microscope. The resulting photomicrograph is shown as Figure 1 of the drawings. The powder is clea~ly sub-micron in size and would be expected to ~2~
sinter readily. Indeed, the powder was closely compa-rable in all properties tested to one prepared by the prior art method of hydrolysis of zirconium n~propox-ide, a technique which is generally recognized as yielding some of the purest and highest quality zir-conia powders now available.
Example 2: Preparation of Yttria-Doped Zirconia Amounts of 50 gm of ZrC14 and 4.05 gm of YC13 6H2O (both reagent grade products from Alfa products) were dissolved in about 500 ml of anhydrous ethanol as in Example 1. NaOH pellets as in Example 1 weighing 35.85 gm were dissolved in about ~00 ml of the same alcohol to form the second solution. The warm first solution was slowly poured into the hot second solution while stirring, and a precipitate formed rapidly. Stirring was continued for five minutes, after which time there was no evidence of additional precipitation. (A sample of the liquid was removed and diluted with water to test its pH, which was 6.
Additional NaOH pellets were added to another sample of the supernatant liquid without evidence of further precipitation,) The prPcipitate was separated and prepared for microscopic examination as in Example 1.
The resulting photomicrograph is shown as Figure 2 of --the drawings. As in Example 1, the powder is sub-micron in size.
A sample of the powder as prepared for micro-scopic examination was prepared for sintering by calcining in air at 500C for two hours. The calcined powder was mixed with a conventional binding aid ~5% by weight of the powder of an aqueous solution of 1% by weight methyl cellulose) and then pressed with a force of 5000 pounds per ~quare inch (psi), equivalent to 34 megapascals (MPa), into a circular disc 2.5 cm in diameter ~r test firing. The green density of the disc was 1.58 megagrams per cubic meter ~Mg/m ). The green disc was sintered in air in a convent.ional furnace at 1600DC for one hour, along with green discs made by identical processing of three commercial powders: *~oyo-Soda powder with 5.4 % yttria by weight, designated T S;*~IRCAR 5.4 % yttria by weight, desig-nated Z-5; and ZIRCAR 12 ~ yttria by weight, desisnated Z-12. The powder prepared ac~ording to this Example is designated E-~. Results of sintering these four typ~s of green discs are shswD in the table beiow.
.. _ . _ .......................... .. _ .
Table Effec~ of Sintering Y2O3-Doped ZrO~ Green Ware . . . _ ._ Desig- Densities, M~/M Percent Chan~es on Firin~:
nation ~reen Fired Weight Volume Diameter . . . _ . .
T S 2.59 ~.99 6.1 58 25 20 Z-5 l.gl 5.75 ~.3 66 28 Z-12 1.~9 5~94 6.~ 6S 29 ~-2 1.46 5.84 7.4 75 37 _, .. . . . .
The results in this table show that the product of the present invention makes lower densi~y green ware but comparable density fired ware/ compared with conventional powders.
* Trade Mark -8-, .
Example 3 _ Change in Solvent The starting materials and processing for thisexample were identical to those for Example 2, except that commercial grade methanol, containing up to 1.5%
of water, was used as the solvent rather than anhydrous ethanol. The fired density of discs made with powders prepared by this variation was 5.53 Mg/m , signifi-cantly less than that for the powders prepared in ahydrous alcohol but still acceptable for some pur-poses.
I claim:
For sintering, a little carbon can be tolerated because it will be converted to fugitive gases at a sufficiently low temperature so that it can escape through the remaining open pore structure of the 8~
incompletely sintered body. Larger amounts may give rise to retention in the final sintered body, however, and such retention is generally undesirable.
Although the description has been given primarily in terms of the preparation of zirconia powders, it should be understood that it is equally applicable to the preparation of powders of silica, titania, alumina, and many other oxides and mixtures thereof.
The invention may be illustrated by the following examples:
Example 1: Preparation of Undoped_Zirconia Twenty grams of ZrCl4 powder (99.6% purity product of Alfa Products) was dissolved in about 500 ml of anhydrous ethanol ~Baker Analyzed Reagent Grade~ to form the first solution. The second solution consisted of 13.7 gm of NaOH (Baker Analyzed Reagent Grade) pellets dissolved in about 500 ml of the same alcohol.
The first solution was poured slowly into the second, with constant stirring. A very fine precipi-tate formed very rapidly and slowly settled to give aclear supernatant liquid. The li~uid was decanted and the precipitate dried in a stainless steel pan on a laboratory hot plate. The dried powder was then washed with distilled water until no chloride ions were detectable in the wash water when it was tested with a nitric acid solution saturated with silver nitrate.
The powder was then dried a~ about 105~C in an oven, and then subjected to examination with a scanning electron microscope. The resulting photomicrograph is shown as Figure 1 of the drawings. The powder is clea~ly sub-micron in size and would be expected to ~2~
sinter readily. Indeed, the powder was closely compa-rable in all properties tested to one prepared by the prior art method of hydrolysis of zirconium n~propox-ide, a technique which is generally recognized as yielding some of the purest and highest quality zir-conia powders now available.
Example 2: Preparation of Yttria-Doped Zirconia Amounts of 50 gm of ZrC14 and 4.05 gm of YC13 6H2O (both reagent grade products from Alfa products) were dissolved in about 500 ml of anhydrous ethanol as in Example 1. NaOH pellets as in Example 1 weighing 35.85 gm were dissolved in about ~00 ml of the same alcohol to form the second solution. The warm first solution was slowly poured into the hot second solution while stirring, and a precipitate formed rapidly. Stirring was continued for five minutes, after which time there was no evidence of additional precipitation. (A sample of the liquid was removed and diluted with water to test its pH, which was 6.
Additional NaOH pellets were added to another sample of the supernatant liquid without evidence of further precipitation,) The prPcipitate was separated and prepared for microscopic examination as in Example 1.
The resulting photomicrograph is shown as Figure 2 of --the drawings. As in Example 1, the powder is sub-micron in size.
A sample of the powder as prepared for micro-scopic examination was prepared for sintering by calcining in air at 500C for two hours. The calcined powder was mixed with a conventional binding aid ~5% by weight of the powder of an aqueous solution of 1% by weight methyl cellulose) and then pressed with a force of 5000 pounds per ~quare inch (psi), equivalent to 34 megapascals (MPa), into a circular disc 2.5 cm in diameter ~r test firing. The green density of the disc was 1.58 megagrams per cubic meter ~Mg/m ). The green disc was sintered in air in a convent.ional furnace at 1600DC for one hour, along with green discs made by identical processing of three commercial powders: *~oyo-Soda powder with 5.4 % yttria by weight, designated T S;*~IRCAR 5.4 % yttria by weight, desig-nated Z-5; and ZIRCAR 12 ~ yttria by weight, desisnated Z-12. The powder prepared ac~ording to this Example is designated E-~. Results of sintering these four typ~s of green discs are shswD in the table beiow.
.. _ . _ .......................... .. _ .
Table Effec~ of Sintering Y2O3-Doped ZrO~ Green Ware . . . _ ._ Desig- Densities, M~/M Percent Chan~es on Firin~:
nation ~reen Fired Weight Volume Diameter . . . _ . .
T S 2.59 ~.99 6.1 58 25 20 Z-5 l.gl 5.75 ~.3 66 28 Z-12 1.~9 5~94 6.~ 6S 29 ~-2 1.46 5.84 7.4 75 37 _, .. . . . .
The results in this table show that the product of the present invention makes lower densi~y green ware but comparable density fired ware/ compared with conventional powders.
* Trade Mark -8-, .
Example 3 _ Change in Solvent The starting materials and processing for thisexample were identical to those for Example 2, except that commercial grade methanol, containing up to 1.5%
of water, was used as the solvent rather than anhydrous ethanol. The fired density of discs made with powders prepared by this variation was 5.53 Mg/m , signifi-cantly less than that for the powders prepared in ahydrous alcohol but still acceptable for some pur-poses.
I claim:
Claims (14)
1. A process for the preparation of sinterable metal oxide ceramic powders, comprising the steps of:
(a) forming a substantially anhydrous first solution of salts of all the metals whose oxides are present in said metal oxide ceramic powders in the proportions therein and forming a substan-tially anhydrous second solution of alkali metal hydroxides in the amount stoichiometrically re-quired to react with the metal content of said first solution;
(b) mixing said first solution and said second solution so as to form a solid precipitate containing substantially all the ceramic metal content originally in said first solution;
(c) separating said solid precipitate from the bulk of its supernatant liquid;
(d) heating said solid precipitate to re-move residual solvent;
(e) washing said solid precipitate with water sufficiently to remove substantially all water-soluble salts therefrom; and (f) drying said washed solid precipitate at a temperature in excess of the boiling point of water.
(a) forming a substantially anhydrous first solution of salts of all the metals whose oxides are present in said metal oxide ceramic powders in the proportions therein and forming a substan-tially anhydrous second solution of alkali metal hydroxides in the amount stoichiometrically re-quired to react with the metal content of said first solution;
(b) mixing said first solution and said second solution so as to form a solid precipitate containing substantially all the ceramic metal content originally in said first solution;
(c) separating said solid precipitate from the bulk of its supernatant liquid;
(d) heating said solid precipitate to re-move residual solvent;
(e) washing said solid precipitate with water sufficiently to remove substantially all water-soluble salts therefrom; and (f) drying said washed solid precipitate at a temperature in excess of the boiling point of water.
2. A process according to Claim 1, comprising the additional step of calcining said dried precipitate at a temperature of at least 500°C to remove physically bound water and solvents.
3. A process according to Claim 2, wherein said first solution comprises a zirconium salt.
4. A process according to Claim 3, wherein said first solution comprises an yttrium salt in an amount equal to at least 3% by weight of the content of said zirconium salt.
5. A process according to Claim 1, wherein said first solution comprises a zirconium salt
6. A process according to Claim 5, wherein said first solution comprises an yttrium salt in an amount equal to at least 3% by weight of the content of said zirconium salt.
7. A process according to Claim 1, wherein said first solution or said second solution is formed with anhydrous ethanol as the solvent.
8. A process according to Claim 2, wherein said first solution or said second solution is formed with anhydrous ethanol as the solvent.
9. A process according to Claim 3, wherein said first solution or said second solution is formed with anhydrous ethanol as the solvent.
10. A process according to Claim 4, wherein said first solution or said second solution is formed with anhydrous ethanol as the solvent.
11. A process according to Claim 1, wherein said alkali metal hydroxide is sodium hydroxide.
12. A process according to Claim 2, wherein said alkali metal hydroxide is sodium hydroxide.
13. A process according to Claim 3, wherein said alkali metal hydroxide is sodium hydroxide.
14. A process according to Claim 4, wherein said alkali metal hydroxide is sodium hydroxide.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/511,058 US4501818A (en) | 1983-07-05 | 1983-07-05 | Process for the preparation of ceramic powders |
| US511,058 | 1983-07-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1208414A true CA1208414A (en) | 1986-07-29 |
Family
ID=24033282
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000455796A Expired CA1208414A (en) | 1983-07-05 | 1984-06-04 | Process for the preparation of ceramic powders |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4501818A (en) |
| EP (1) | EP0130480B1 (en) |
| JP (1) | JPS6036307A (en) |
| CA (1) | CA1208414A (en) |
| DE (1) | DE3476376D1 (en) |
Families Citing this family (31)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4627966A (en) * | 1984-03-19 | 1986-12-09 | General Motors Corporation | Formation of fine particle sinterable ceramic powders |
| US4605631A (en) * | 1984-03-19 | 1986-08-12 | Norton Company | Advanced preparation of ceramic powders |
| US4619817A (en) * | 1985-03-27 | 1986-10-28 | Battelle Memorial Institute | Hydrothermal method for producing stabilized zirconia |
| US4649037A (en) * | 1985-03-29 | 1987-03-10 | Allied Corporation | Spray-dried inorganic oxides from non-aqueous gels or solutions |
| US4834928A (en) * | 1985-08-01 | 1989-05-30 | Gte Laboratories Incorporated | Doped silicon nitride article |
| US4814128A (en) * | 1985-08-01 | 1989-03-21 | Gte Laboratories Incorporated | Process for making a homogeneous doped silicon nitride article |
| US4639356A (en) * | 1985-11-05 | 1987-01-27 | American Cyanamid Company | High technology ceramics with partially stabilized zirconia |
| FR2593166A1 (en) * | 1986-01-20 | 1987-07-24 | Solvay | PROCESS FOR PRODUCING A METAL OXIDE POWDER FOR CERAMIC MATERIALS AND ZIRCONIA POWDER OBTAINED THEREBY |
| FR2600550B1 (en) * | 1986-05-30 | 1990-10-19 | Meridional Oenologie Centre | METHODS OF MAKING THIN MEMBRANE COMPOSED OF A MINERAL ARRAY OF TITANIUM OXIDES AND SILICON AND POWDER COMPOSED OF SUBMICRONIC GRAINS IN MIXED OXIDES OF TITANIUM AND SILICON |
| CA1262813A (en) * | 1986-06-26 | 1989-11-14 | Corning Glass Works | Preparation of high purity, homogeneous zirconia mixtures |
| JPS63156057A (en) * | 1986-12-19 | 1988-06-29 | 科学技術庁無機材質研究所長 | Manufacture of high density perovskite ceramics |
| US4927622A (en) * | 1987-06-19 | 1990-05-22 | Manville Corporation | Process for producing zirconium based granules |
| US5053214A (en) * | 1987-06-19 | 1991-10-01 | Manville Corporation | Process for producing zirconium based granules |
| US4771950A (en) * | 1987-07-06 | 1988-09-20 | Norton Company | Hydrothermal comminution or zirconia or hafnia |
| US4882014A (en) * | 1988-02-24 | 1989-11-21 | Union Oil Company Of California | Electrochemical synthesis of ceramic films and powders |
| US5032555A (en) * | 1988-05-16 | 1991-07-16 | Allied-Signal Inc. | Process for making zirconia-alumina |
| US4920083A (en) * | 1988-05-18 | 1990-04-24 | Research Triangle Institute | Novel process for the production of ceramic flakes |
| US4937212A (en) * | 1988-12-19 | 1990-06-26 | Minnesota Mining And Manufacturing Company | Zirconium oxide fibers and process for their preparation |
| DK0395912T3 (en) * | 1989-05-02 | 1993-12-06 | Lonza Ag | Sintered zirconia powder and process for its preparation |
| IT1240321B (en) * | 1990-02-23 | 1993-12-07 | Eniricerche Spa | PROCEDURE FOR THE PREPARATION OF MIXED ZIRCONIUM AND YELLOW OXIDE POWDERS |
| IT1241403B (en) * | 1990-03-02 | 1994-01-14 | Eniricerche Spa | PROCEDURE FOR THE PREPARATION OF MIXED ZIRCONIUM AND YELLOW OXIDES |
| US5312613A (en) * | 1991-07-09 | 1994-05-17 | Akzo N.V. | Process for producing ceramic precursor powders without gel formation |
| US5421523A (en) * | 1992-12-21 | 1995-06-06 | Mcmahon; David J. | Physio-chemical communication with expansive solidifiers |
| DE4317174A1 (en) * | 1993-05-22 | 1994-11-24 | Bosch Gmbh Robert | Composite system with at least two inorganic ceramic layers and process for their production |
| US5439580A (en) * | 1993-11-05 | 1995-08-08 | The Ohio State University | Solid-state gas sensor for carbon monoxide and hydrogen |
| JP2007191354A (en) * | 2006-01-19 | 2007-08-02 | Tokyo Univ Of Science | Method for producing calcium zirconate by sol-gel process |
| US8679995B1 (en) | 2012-07-25 | 2014-03-25 | Superior Technical Ceramics Corporation | Addition of magnesium oxide to zirconia toughened alumina |
| WO2014100984A1 (en) * | 2012-12-26 | 2014-07-03 | Essilor International (Compagnie Generale D'optique) | Method for producing zirconia colloids |
| CN107382326B (en) * | 2017-08-24 | 2020-11-17 | 江苏思麦尔生命科技有限公司 | Method for improving sintering activity of micron zirconia powder |
| CN107445202B (en) * | 2017-08-30 | 2019-08-06 | 华能国际电力股份有限公司 | A kind of small size, super-dispersed nano zirconium oxide base coating raw powder's production technology |
| CN113371756B (en) * | 2021-07-13 | 2023-04-25 | 河南工业大学 | La-Sc-ZrO2 nano crystal material and preparation method thereof |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT200109B (en) * | 1957-08-28 | 1958-10-25 | Goldschmidt Ag Th | Process for the production of zirconium oxide from zirconium tetrachloride |
| US3334962A (en) * | 1962-10-08 | 1967-08-08 | Nat Lead Co | Process for the production of cubic crystalline zirconia |
| US3254949A (en) * | 1962-10-08 | 1966-06-07 | Nat Lead Co | Process for the production of zirconia |
| US3514252A (en) * | 1967-07-07 | 1970-05-26 | Grace W R & Co | Process for the preparation of stabilized zirconia powders |
| FR2475531A1 (en) * | 1980-02-08 | 1981-08-14 | Commissariat Energie Atomique | PROCESS FOR THE PREPARATION OF STABILIZED ZIRCONIC SOLID ELECTROLYTE PARTS AND THE PARTS OBTAINED THEREBY |
-
1983
- 1983-07-05 US US06/511,058 patent/US4501818A/en not_active Expired - Fee Related
-
1984
- 1984-06-04 CA CA000455796A patent/CA1208414A/en not_active Expired
- 1984-06-20 DE DE8484107094T patent/DE3476376D1/en not_active Expired
- 1984-06-20 EP EP84107094A patent/EP0130480B1/en not_active Expired
- 1984-07-03 JP JP59136654A patent/JPS6036307A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| EP0130480A2 (en) | 1985-01-09 |
| EP0130480A3 (en) | 1987-01-07 |
| US4501818A (en) | 1985-02-26 |
| JPH0476923B2 (en) | 1992-12-07 |
| EP0130480B1 (en) | 1989-01-25 |
| DE3476376D1 (en) | 1989-03-02 |
| JPS6036307A (en) | 1985-02-25 |
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