Virtually, the process of sintering is powder grains are heated in appropriate condition, after a series of physical and chemical changes, and qualitative changes generated between powder particles, strength and density of the blank increase rapidly, other physical and chemical performance also improve obviously. Pressed blanked is not usable directly, so sintering is one of the necessary processes of ceramic production, also as the last step, it decides the performance of final product, so it’s very important to control the sintering process cautiously.   

 In terms of thermodynamics, sintering is a process of energy loss for the system. Compared with clumps, powder has very large surface area, and atoms in surface has much higher energy than those inside. Meanwhile, during the process of powder manufacture, there are various of lattice imperfection. The tendency of energy loss exist for any system, which will provide motive force of sintering process, that is for the system, the transformation from pressed blank to sintered blank is also a process that system becomes stable. However, the sintering can not be implemented spontaneously, since the energy of pressed blank is not enough to overcome the energy barrier, should be heated up to a certain temperature.  

Sintering is a complex physical and chemical change, long-term study shows that the mechanism of sintering can be summarized as: 1. viscous flow; 2. evaporation and agglomeration; 3. volume diffusion; 4. surface diffusion; 5.grain boundary diffusion; 6. plastic flow, etc. Practice shows that it’s difficult to explain the sintering by any single mechanism, sintering is complex and multi-mechanism process, therefore “comprehensive action sintering theory” arised.