Study On Preparation And Sinterng Properties Of High Purity Alumina Ceramic

Al2O3ceramic has been become the largest-scale production and widest applied advanced ceramic materials, due to its high mechanical strength, outstanding of corrosion performance and rich raw materials. High-purity alumina ceramic has little amorphous phase and can obtain high-density Al2O3translucent ceramic which has high transmittance in the visible and infrared light. Al2O3translucent ceramic has a widespread application in high pressure sodium lamp tube and infrared window materials.Currently, alkoxide hydrolysis method is the traditional method to prepare high-purity alumina powders. However, there will form aggregates in hydrolysis process and have negative effect in sintering process. In this paper, AlF3is usually used as mineralizer, was introduced as one of the raw materials to mix with AlOOH, respectively. And milling time, sintering temperature and sintering time are all considered the factors to affect the microstructure and grain size of Al2O3powders which are characterized by SEM and Particle size analysis. From the experiment results, we can make the conclusion that the parameters of processing mentioned above have obvious effect on microstructure and grain size of Al2O3powders. Superfine, high-dispersion and subsphaeroidal high-purity Al2O3powders can obtained by adding0.5wt%AIF3and6hours milling time at1200℃for6h.The high-density and high-purity Al2O3ceramics using the modified powders through isostatic pressing are prepared by liquid phase sintering method. In this paper, we focus on the effect of sintering temperature, sintering time and the amounts and kinds of additives. Meanwhile, we also investigate the dynamics of liquid phase sintering and the grain growth kinetics.Densification process of Al2O3ceramic is controlled by many parameters, such as increasing sintering temperature, extending sintering time and composite additives. The sintering mass transfer mainly belongs to dissolution-precipitation process and the active energy is below to371.89kJ/mol at1500℃for4h in0.7wt%MgO-0.125wt%La2O3liquid phase sintering system. Meanwhile, in this system, the migrate-rate of crystal interface and liquid content are contributing to the process of grain growth and eliminating pore, as a result of increasing the density of alumina body. However, the excessive migrate-rate and liquid content will lead to the abnormal grain growth.