Why does the volume decrease during ceramic sintering process?

 

1. Gas loss and reduction of pores: Wear resistant ceramics are sintered with aluminum oxide powder, which contains a large amount of gas and pores in both the oxide powder and ceramic preform. Under high temperature sintering at 1600 ℃, a large amount of gas will be lost in the preform, and pores will decrease or even disappear, leading to a decrease in ceramic volume and an increase in density.

2. Moisture and impurity evaporation: The amount of impurities contained in aluminum oxide powder used for firing ceramics varies, but even high-purity Australian imported aluminum oxide powder used by Jingcheng still contains a small amount of impurities, although the impurity content is relatively low. Some impurities will also decompose and evaporate at high temperatures, making the aluminum oxide bond more tightly and causing the ceramic volume to shrink.