keywords： Alumina ceramic Zirconia ceramics
At present, it can be divided into high-purity type and common type. The ceramic material with Al2O3 content of more than 99.9% in high-purity alumina ceramic system of wear-resistant plate is generally made into molten glass to replace platinum crucible due to its sintering temperature of 1650-1990 ℃ and transmission wavelength of 1-6 μ M. it can be used as sodium lamp tube by its light transmittance and alkali resistant metal corrosion resistance; it can be used as integrated circuit substrate and high-frequency insulating material in electronic industry.
According to the content of Al2O3, ordinary alumina ceramics can be divided into 99, 95, 90 and 85 ceramics. Sometimes, alumina ceramics with Al2O3 content of 80% or 75% can also be classified as ordinary alumina ceramics. Among them, 99 alumina ceramic materials are used to make high temperature crucible, fire-resistant furnace tube and special wear-resistant materials, such as ceramic bearing, ceramic seal and water valve plate, etc.; 95 alumina ceramic is mainly used as corrosion-resistant and wear-resistant parts; 85 ceramics can be sealed with molybdenum, niobium, tantalum and other metals, and some of them can be used as electric vacuum devices. The manufacturing process is as follows:
According to different product requirements and forming processes, the aluminum oxide powder is prepared into powder materials. The particle size of the powder is less than 1 μ m μ M. if the high purity alumina ceramic products are manufactured, the purity of alumina is 99.99%, and the ultrafine grinding is needed to make the particle size distribution uniform. When the wear-resistant plate is extruded or injection molded, the binder and plasticizer shall be introduced into the powder, generally the thermoplastic plastic or resin with the weight ratio of 10-30%. The organic binder and alumina powder shall be evenly mixed at the temperature of 150-200 ℃ to facilitate the molding operation.
The raw materials of powder formed by hot pressing process need not be added with binder. If semi-automatic or automatic dry pressing is used, there is a special technological requirement for the powder. Spray granulation is needed to treat the powder and make it appear round spherical, so as to improve the fluidity of the powder and facilitate the automatic filling of the mould wall. In addition, in order to reduce the friction between powder and die wall, 1-2% lubricant, such as stearic acid and PVA binder, should be added. For dry pressing, powder granulation is needed, and polyvinyl alcohol is used as binder.