JPH0292825A - Production of zirconium oxide fine powder - Google Patents

Abstract

PURPOSE:To provide the subject fine powder reduced in coarse particles and coaggulated particles thereof, having a sharp particle distribution and useful for obtaining sintered products having high densities by reacting a mixture of a Zr salt and a C powder with heating in an atmosphere containing N2 gas and subsequently oxidizing the reaction product in an atmosphere of O2 gas. CONSTITUTION:A mixture of zirconium oxychloride preferably free of metal impurities and a C powder (e.g., acetylene black) preferably having a particle size of <=1mum and an ash content of <=0.3wt.% is reacted with heating (e.g., 1300-1700 deg.C) in an atmosphere (e.g., N2) containing N2 and the reaction product is heated (e.g., 600-1400 deg.C) in an atmosphere (e.g., air) containing O2 to oxidize the reaction product and to oxidatively remove excess C powder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing fine zirconium oxide powder with few agglomerated particles and a sharp particle size distribution.

[Conventional technology]

Zirconium oxide has a high melting point of 2720'C and has been used as a raw material for high-temperature refractories.

In addition, oxygen sensors that take advantage of its properties and composite oxides made with other substances are widely used in optical glasses, capacitors, piezoelectric materials, etc. Furthermore, zirconium oxide includes CaO, MgO, Y@02. Partially stabilized zirconia (hereinafter referred to as PSZ) has been developed which has achieved high strength and toughness by adding Ce01 etc. to cause stress-induced transformation, and dispersion strengthening by adding zirconium oxide to alumina, spinel, etc. Zirconium oxide is attracting attention as a powerful substance for developing ceramics for structural materials.

Zirconium oxide powder can be synthesized by mixing zircon sand and carbonaceous material, heating it to high temperature in an arc furnace, and discharging the silicate portion as Si0g gas outside the furnace to obtain zirconium oxide. A known method is to neutralize or hydrolyze a zirconium acid salt to obtain zirconium hydroxide, which is then fired. However, the former method uses an arc furnace, which requires a large amount of thermal energy, and the resulting powder has a large particle size, making it unsuitable for use in applications other than furnace materials and abrasive materials. This method was developed to obtain finer powder suitable for the production of ceramics, but since the precipitated zirconium hydroxide obtained by neutralization and hydrolysis is fired, agglomerated particles are likely to be formed ( Normally, the particle size is adjusted by pulverization after firing.Also, because the secondary particles are too fine, strong agglomerated particles are likely to be generated during calcination, and even if pulverization is performed, only powder with a broad particle size distribution is obtained. The current situation is that there is no such thing.

[Invention tries to solve! ! ! Title]

It is well known that when sintering is performed using a powder with a wide particle size distribution including many coarse particles and agglomerated particles as a raw material, it is generally easy to obtain a sintered body containing many pores.

PS is attracting attention as a high-strength, high-toughness ceramic
It has been pointed out that it becomes difficult to obtain a high-density sintered body as the agglomerated particle size increases in Z. Raw material powder is requested. It has also been pointed out that in zirconia dispersion-strengthened ceramics, zirconium oxide has many agglomerated particles and has a broad particle size distribution, so that it cannot be sufficiently dispersed and mixed with other ceramic powders such as alumina.

An object of the present invention is to provide a new method for producing fine zirconium oxide powder with a sharp particle size distribution and fewer coarse particles and agglomerated particles.

[Means to solve the problem]

That is, the present invention heats and reacts a mixture of zirconium salt and carbon powder in an atmosphere containing nitrogen, and then heats the reaction product in an atmosphere containing oxygen to oxidize the reaction product and oxidize excess carbon. An object of the present invention is to provide a method for producing zirconium oxide@ powder, which is characterized by removing zirconium oxide powder.

The present invention will be explained in detail below.

Examples of the zirconium salt used in the present invention include zirconium oxychloride, zirconyl nitrate, zirconyl sulfate, zirconium phosphate, zirconium carbonate, zirconium acetate, ammonium zirconium carbonate, zirconium octylate, and zirconium stearate. Among these, zirconium oxychloride, zirconyl nitrate, and zirconyl sulfate are preferred, and zirconium oxychloride is most preferred in terms of availability and price. Since zirconium oxide remains in the zirconium oxide produced, it is preferable to use zirconium oxychloride of as high a purity as possible. When using zirconium oxychloride, it is usually preferable to use one that has been repeatedly recrystallized to remove metal impurities.

The carbon powder used in the present invention is as pure and fine as possible. Preferably, the primary particle size is 1 μm or less and the ash content is 0.3% by weight or less. As such carbon powder, acetylene black, channel black, furnace black, etc. are known, and among these, acetylene black is preferable from the viewpoint of higher purity, and from the viewpoint of handling, if it is easy to disperse, 0. 3
It is advantageous to use granules granulated to ~1°5 m or powder compressed by press.

The mixing ratio of zirconium salt and carbon powder is carbon/
The molar ratio of zirconium is preferably in the range of 2 to 10. If the molar ratio is less than 2, zirconium nitride is not sufficiently produced, and as a result, it becomes difficult to obtain zirconium oxide with a uniform particle size. On the other hand, if it exceeds IO, the amount of unreacted carbon remaining will increase, making it difficult to remove it and increasing the cost, which is not preferable.

As a method for mixing and dispersing the zirconium salt and carbon powder, a general method such as an ultrasonic dispersion method or various mixers such as a ball mill or a particle granulator can be used. Preferably, a method capable of uniformly dispersing the carbon powder in a solution of a zirconium salt in water or the like, a wet ball mill, a dispersion method using ultrasonic waves, or the like is used. At this time, when using an aqueous solution of zirconium salt, a nonionic surfactant such as polyoxyethylene alkyl phenyl ether or polyoxyethylene alkyl ether or an alcohol such as isopropyl alcohol is added to the aqueous zirconium salt solution. is effective for better dispersion of carbon powder.

In addition, it is desirable to use equipment parts that come into direct contact with these raw materials from materials that do not contain metal impurities; such materials include synthetic resins such as polyethylene, nylon, and urethane, natural resins, It is preferable to use materials made of synthetic rubber, alumina or zirconia, or materials lined or coated with these materials.

Normal industrial methods can be used to dry the mixture, but if the slurry viscosity during mixing is low (there is a risk that carbon powder will settle during drying), spray drying, freeze drying, rotary evaporation etc. It is preferable to use a method such as the above, and if necessary, it can also be granulated into particles with a size of about 20 μm to 31 m along with mixing and drying, and granulation has the advantage that subsequent handling becomes easier. be.

The mixture (powder or granules) obtained in this way is heat-treated in an atmosphere containing nitrogen to perform a reductive nitriding reaction, and the atmosphere includes N2 gas, NH3 gas, N, -11t+3 mixed gas. , Ng-1h mixed gas, N8-^ "Mixed gases can be used.

Among these, N and gas atmospheres are preferred.

The heat treatment temperature is generally in the range of 1300 to 1700°C, preferably 1400 to 1600°C, 1300°C.
If it is less than 1,700°C, it will take a long time to sufficiently proceed with the reductive nitriding reaction, and if it exceeds 1,700°C, coarse particles will be produced in large quantities, which is undesirable.
It is most suitable to hold at a temperature of 2 to 6 hours.

Furthermore, the product mainly composed of zirconium nitride produced by the reductive nitriding reaction is oxidized to zirconium oxide, and a heat treatment is performed in an atmosphere containing oxygen for the purpose of removing the remaining excess carbon. The term "in an atmosphere containing carbon" means in air or in an oxygen atmosphere, and the treatment must be carried out at a temperature higher than that at which carbon is reliably burnt and removed, and a temperature of 600 to 1400 DEG C. for 1 to 5 hours is appropriate. If the heat treatment temperature is less than 6θ0°C, it will take a long time to completely burn the carbon, while if it exceeds 1400°C, sintering of the zirconium oxide powder will occur in some parts.
It is also economically unfavorable.

In addition, by adding an appropriate amount of calcium oxide, magnesium oxide, cerium oxide, yttrium oxide, calcium salt, magnesium salt, cerium salt, indolium salt, etc. when mixing zirconium salt and carbon powder, the crystal phase can be improved. Controlled zirconia fine powder can be synthesized.

(Effect of the invention) The zirconium oxide powder obtained by the method of the present invention is a fine powder with few coarse particles and agglomerated particles and a sharp particle size distribution. It is useful as a raw material for producing high-strength, high-toughness zirconia-based sintered bodies, capacitors, and piezoelectric materials.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Example Zirconium oxychloride [Zr0Ch ・811! OF
Take 64.4g in a beaker and add 200g of ion exchange water.
Add 2 g of isopropyl alcohol and stir to dissolve. This solution was placed in 12 polyethylene pots containing 500 ml of nylon coated balls each having a diameter of 15 g, and 12 g of acetylene black was added thereto, followed by ball mill mixing at a rotational speed of 60 rpm for 5 hours. Thereafter, the mixed slurry was taken out from the pot and dried in a rotary evaporator to obtain a raw material powder.

10 g of this raw material powder was placed in a graphite container and heated at 1500°C for 5 hours while flowing nitrogen gas at a rate of 200 cm/win using a tubular electric furnace to perform a reductive nitriding reaction. 800℃ in air
The mixture was heated for 3 hours to obtain 5 g of zirconium oxide powder.

Sedigraph (Micro) of this zirconium oxide powder
Seritics 5edi Graph 5000E
The particle size distribution curve according to T) is shown in FIG. This zirconium oxide powder has a center particle size of 0.65 μm and 2 μm.
m or less was 95χ, and the powder had a coarse particle size distribution with almost no coarse particles or agglomerated particles.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the particle size distribution curve of the zirconium oxide powder obtained in the example, determined by Sedigraph.

Claims (1)

[Claims] After heating and reacting a mixture of zirconium salt and carbon powder in an atmosphere containing nitrogen, the reaction product is heated in an atmosphere containing oxygen to oxidize the reaction product and oxidize and remove excess carbon powder. A method for producing fine zirconium oxide powder characterized by