The technical method of densifying a granular ceramic body and forming a solid material is called sintering. Sintering is a method of removing voids between particles in a billet, excluding a small amount of gas and impurity organic matter, and causing the particles to grow and combine with each other to form a new substance.
In addition to pressureless sintering, there are also hot press sintering and hot isostatic pressing. Although continuous hot press sintering increases production, equipment and mold costs are too high, and product length is limited. The hot isostatic pressing uses high-temperature and high-pressure gas as the pressure transmission medium, and has the advantages of uniform heating in all directions, and is suitable for sintering of complicated shapes.
Therefore, some high-value-added alumina ceramic products or special components required for the defense industry, such as ceramic bearings, mirrors, nuclear fuel and barrels, often use hot isostatic pressing.
In addition, microwave sintering, arc plasma sintering, and self-propagating sintering are also being developed.