Neutralization Precipitation Method
The neutralization precipitation method, also known as chemical coprecipitation, is controlled by adding the appropriate alkali solution into the mixed solution of soluble salt and zirconium salt of stabilizer. It controls the formation of zirconium dioxide gel by coprecipitation and precipitation of pH (8~9), and obtains stable zirconia powder by filtration, drying and heat treatment (600~900 degree). This method is simple, easy to add trace elements, does not need expensive raw materials, and can make stabilizers evenly dispersed in zirconia, with large output. However, the coprecipitation process is difficult to control, and it is easy to form coagulation, encapsulation and adsorption impurities. Solid-liquid separation and washing are difficult. The caking during calcination is serious, which needs to be crushed and treated. It is easy to cause secondary pollution. If suitable dispersant can be found, the disadvantage of easy agglomeration of powder can be overcome.
2.2.2 The advantage of heating hydrolysis method is that it can hydrolyze the mixed solution of zirconium salt and soluble stabilizer without adding alkali, so there are no harmful anions and alkali metal ions. It can be divided into salt solution adding water hydrolysis method and alkoxide adding water hydrolysis method.
2.2.3 zirconium alkoxy compound was prepared by sol-gel method using sol-gel method. The stabilized zirconia powder was prepared by controlling the hydrolysis conditions of the two zirconium oxide compounds. This method can obtain stable zirconia powders with fine particle size and excellent monodispersity, and the process is easy to control, which overcomes the problem of intermediate phase change in the decomposition of alkoxy compounds. However, the production capacity is small, the preparation cycle is long, the process conditions are harsh, and expensive metal alkoxide is needed as raw material, the production cost is high, and it is not easy to carry out large-scale industrial production.
2.2.4 Solid phase method, also known as sintering method, mechanical method or powder mixing method, is based on zirconium dioxide and stabilizer powder as raw materials, according to a certain proportion, using ball milling and other grinding equipment to mix evenly, high temperature solid phase reaction, time is about 6 hours, high temperature sintered blocks will be crushed to the required size of zirconium dioxide. The finished product produced by this method has large particle size, wide distribution range and is easy to mix impurities, which can not meet the high-level requirements of new material development.
2.2.5 There are two methods to produce stable zirconia by electrofusion: primary electrofusion method and secondary electrofusion method.