JPH01230433A - Production of alumina-zirconia multiple powder - Google Patents

Abstract

PURPOSE:To obtain the subject powder capable of providing a calcined compact excellent in strength, by adding an alkaline solution to a Zr solution containing finely pulverized alumina particles dispersed therein, filtering suspended substances in the resultant slurry and washing the filtered substances with aqueous ammonia. CONSTITUTION:Finely pulverized alumina particles are dispersed in a solution of a Zr salt (e.g., zirconium oxychloride) at pH1-3 and an alkaline solution, such as aqueous ammonia, is then added to provide an alumina-zirconia multiple slurry at pH6-10. Suspended substances in the slurry, as necessary, are then pulverized and filtered to afford a filter cake, which is washed with aqueous ammonia to weaken cohesive force of Zr(OH)4, disperse part of alumina particles flocculated at the isoelectric point and simultaneously remove Cl ions in the precipitates.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing alumina-zirconia composite powder.

(Prior Art) It is known that adding zirconia to alumina strengthens the toughness of an alumina sintered body. The conventional method for adding zirconia has been to mix alumina powder and zirconia powder. However, whether it is alumina particles-r or zirconia particles, if they are fine particles with a particle size of 0.5 .mu.rrt or less, they have a high surface activity and are likely to form aggregates. This property is particularly remarkable for zirconia particles. Therefore, in order to uniformly disperse alumina fine particles and zirconia fine particles, it is necessary to stir and sufficiently crush the aggregated alumina and zirconia particles. However, these aggregates are difficult to disperse, and although various types of stirrers and crushers have been used to crush them, the results are still not satisfactory. On the other hand, in order to increase the hardness of alumina-zirconia, it is better to reduce the amount of zirconia added. In this case, it is necessary to disperse zirconia more finely and uniformly, and this uniform dispersibility is questioned. As described above, in the method of manufacturing an alumina-zirconia sintered body, the uniform dispersibility of fine zirconia powder has been highlighted as a technical problem. In view of these points, the present inventors previously proposed in Japanese Patent Application No. 62-223588 that the aluminum salt, zirconium JJ (,74, and in an aqueous solution of urea))H was raised to - in the range of 3 to 5. Recently, we invented and filed an application for a method for crystallizing zirco-1-niu-11 hydroxide around aluminum hydroxide particles.

(Problems to be Solved by the Invention) However, the alumina-zirconia composite powder produced by this method has a relative density of only about 90% even after being molded and fired, and its strength is still far from sufficient. I couldn't.

(Means for Solving the Problems) The present invention improves the method for producing alumina-zirconia composite powder by analyzing 11 zirconium hydroxide products. In addition, the first object of the present invention is to uniformly and uniformly disperse fine zirconia particles in alumina, and to form and sinter them to a high strength.
It is an object of the present invention to provide a method for producing an alumina-zirconia composite powder that has high functional properties.

That is, finely pulverized alumina powder is dispersed in a zirconium salt solution, an alkaline solution is added to the solution to make a slurry with a pH of 6 to 10, the slurry is filtered, and the filter residue is diluted with aqueous ammonia. This is a method for producing alumina-zirconia composite powder obtained by washing.

In the present invention, a zil':, lium solution and an acidic salt solution of (i, zirconium oxychloride, zirconia chloride 11, zirconia sulfate 11, etc.) are used.Also, as the alkaline solution, ammonia water, an ammonium carbonate solution, etc. are used. Or use a mixture of aqueous ammonia and ammonium carbonate.

In addition, in the present invention, by adding an alkaline solution, 1) 1
The reason for changing 1 to 6 to 10 is that l1
If lr is 6 or more, this is because the precipitate does not become finer in 11 minutes, whereas if it is I' II or more than 10, the reaction does not proceed further, and an alkaline solution such as ammonia is Because it would be wasted.

(Function) 11' I-I of the zirconium salt solution is 1-3 and is acidic. Therefore, the alumina powder does not aggregate due to the peptizing action of the zirconium salt solution, and the fine alumina particles (
Seal and disperse in the solution. When an alkaline solution such as aqueous ammonia is added to one volume of this alumina and stirred at +Y, ■]I■ increases by one level, and zirconium hydroxide is precipitated around the alumina fine particles at around 4.5. At this time,
The hydroxide zirconia 11 contains alumina fine particles and is a giant molecule chained with hydroxyl groups, forming a very viscous precipitate. Continuing to gradually add an alkaline solution to this chain-like precipitate and raising I-I to around 6 to 10, the hydrogen bonds of zirconium hydroxide in the chain-like precipitate are broken] and stirred. This loosens the giant precipitate. In this way, the alumina particles to which the zirconia hydroxide 11 is attached are separated to obtain a liquid mixture (alumina-zirconia composite slurry). However, at this point, the highly cohesive zirconia hydroxide 11 still remains, so it is desirable to grind it by bowl, lumill, or stir it for a long time. However, this operation differs depending on the type of filtration and vortex used in the subsequent process, such as a filter press, filtration accompanied by centrifugation, etc., and there is no need for a platform on which a high-density cake can be produced at t1↑. Filter this slurry. Next, by further washing the slag with aqueous ammonia, f! concentration becomes even weaker). At this time, the alumina particles that have aggregated at equal points are also partially dispersed, and the chlorine ions contained within the precipitate are also quickly and efficiently washed away from the filter dregs.

(Example) Next, examples of the present invention will be described.

Example” Alumina powder GO with average particle size 0, C; 7z m
Og was mixed in 800 mL of 33% silconium oxychloride t1 solution in terms of zirconia, and the volume was 1.00 Ont.
Stir with a ball mill. 5N aqueous ammonia is added to the alumina particle dispersion solution thus prepared.

With the addition of this ammonia water, it initially becomes white and bulky.
A huge precipitate about 5 mm in diameter is formed. Furthermore, when aqueous ammonia is gradually added, as I) H increases, this huge precipitate is loosened to form a cloudy alumina-zirconia composite slurry in which zirconium hydroxide-alumina particles are dispersed.

This human rally is ground in a ball mill, filtered through N 05 C filter paper, and the filter cake is washed with aqueous ammonia (0.2 to 5 normal) until no chlorine or ions are detected in the filtrate.

Thereafter, it is washed with alcohol such as methyl alcohol or ethyl alcohol to obtain a fine powder of 11 minutes. The washed filter cake is dried at 1'0°C for 1 hour, and then calcined at 600°C. Water and a dispersant were added to the resulting alumina-zirconia aggregates, and the mixture was dispersed in a bot mill for 16 hours.Additionally, small diameter balls of 1 mm were added and dispersed in a sand mill for 1 hour, and dried to form an alumina-zirconia composite powder. make.

The resulting alumina-zirconia composite powder is granulated with a spray dryer to a size of 0.7 mm or less and a moisture content of 8%. Next, it was filled into a 63 x G: 3 x 6 m TI mold, press-molded at 300 kK/(T12), then further pressurized by cold isostatic compression at 1,1300 kg/cm2, and then heated to 1550°C. The bending strength, wear test using +1~, and Vickers hardness of the resulting sintered body are as follows.For comparison, commercially available alumina powder alone was molded and fired in the same way, and alumina powder Measured values of the molded and fired body and zirconia powder are also shown.

Bending strength Plast Vickers abrasion test Hardness 1l-(, lil: reduction (kF/cm2m r/kg Fugocho 6060 18.3 1690 aluminum
4620 22, 4. 1760 Sumi Aluminum /1640 19.9 1700 Sumi Zirconia Powder In the table, the bending strength is the average value based on the test method of J]5l11601], plus 1-1! f
In the wear test, alumina abrasive grains with an average diameter of 100 μm were placed on the specimen at an angle of 45° with respect to the surface of the specimen.
1. Sprayed from the nostle of mm LE l, OK
It is expressed as the weight loss per unit test weight when blowing at g/cm2 for 2 minutes.

Example 2 Alumina-zirconia composite powder prepared in the same manner as in Example 1 was granulated and molded in the same manner as in Example 1.
It was fired at C. The measured values of the completed sintered body are as follows.

Bending strength: 64.30 kg/crn 2 TP weight loss due to blasting: 15.3 m g/crn
kg Vickers hardness 17 Example 3 The particle size of alumina powder was 0.3μIn in
Alumina-zirconia composite powder treated in the same manner as in Example 1 was granulated, molded, and fired in the same manner as in Example 1.
The bending strength of the resulting Ga-C assembly is 6,750 kg/aK, plus 1 to 16. :3mg/kg
Vickers hardness: 1790 Example 4 In Example 1, zirconium oxychloride was adjusted to contain 5% zirconia to produce an alumina-zirconia composite powder, and granulated, molded, and fired in the same manner as in Example. The bending strength of the completed sintered body is 6 (54Okg/
J'ff ril by a+f, plus 1-: decrease 1B
, 1mg/kg Vickers hardness: 680 I) F■ from 6 to 10+
In order to raise the temperature, the giant precipitate of zirconia hydroxide 11 that is generated is loosened to form a slurry. Further, since this slurry is filtered and the filter residue is washed with ammonia water, the zirconia fine particles are uniformly dispersed between the alumina grains 1 without agglomeration.

As described above, according to the present invention, a fine alumina-zirconia composite powder is produced, and if this is shaped and fired, it can be sintered even at a relatively low temperature. Moreover, the zirconia powder is uniformly dispersed between the alumina grains in the sintered body, suppressing the grain growth of the alumina grains in the sintered body, and making it possible to obtain a sintered body with high strength. Furthermore, the present invention enables fine zirconia particles to be uniformly and
Even when the zirconia content is extremely small, toughness is enhanced by the addition of zirconia, making it possible to obtain an ideal sintered body of alumina-zirconia.

Claims (1)

[Claims] Finely ground alumina particles are dispersed in a zirconium solution,
Adding an alkaline solution such as aqueous ammonia to the solution
A method for producing an alumina-zirconia composite powder by preparing H into a slurry of 6 to 10, pulverizing the suspension in the slurry or filtering it without pulverizing, and washing the filter residue with aqueous ammonia.