The technical method of densifying the granular ceramic body and forming a solid material is called sintering. Sintering is a method of removing the voids between particles in the green body, removing a small amount of gas and impurity organic matter, so that the particles can grow and combine with each other to form a new substance.
The heating device used for firing is the most widely used electric furnace. In addition to atmospheric sintering, namely pressureless sintering, there are also hot pressing sintering and hot isostatic pressing sintering. Although continuous hot-pressing sintering increases the output, the equipment and mold costs are too high. In addition, due to the axial heating, the length of the product is limited. Hot isostatic pressing uses high temperature and high pressure gas as the pressure transmission medium, which has the advantage of uniform heating in all directions, and is very suitable for sintering products with complex shapes. Due to the uniform structure, the material performance is 30-50% higher than that of cold-pressed sintering. 10-15% higher than general hot pressing sintering. Therefore, some high value-added alumina ceramic products or special parts required by the national defense industry, such as ceramic bearings, reflectors, nuclear fuel and gun barrels, are fired by hot isostatic pressure.
In addition, microwave sintering, arc plasma sintering, and self-propagating sintering technologies are also under development and research.