Sintering Technology of Alumina Ceramics

The technical method of densifying granular ceramic bodies and forming solid materials is called alumina sintering. Alumina sintering is a method of removing voids between particles in the green body, removing small amounts of gas and impurities, and combining particles to form new substances.

The heating device used for firing is the most widely used electric furnace. In addition to pressureless sintering of alumina under normal pressure, there are also hot pressing sintering and Hot isostatic pressing sintering. Although continuous hot pressing sintering increases production, the equipment and mold costs are too high. In addition, due to axial heating, the length of the product is limited. The Hot isostatic pressing sintering 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 the sintering of products with complex shapes. Due to its uniform structure, the material performance is improved by 30-50% compared to cold pressing sintering. Improved by 10-15% compared to conventional hot pressing sintering. Therefore, at present, some high value-added alumina ceramic products or special parts and components required by national defense and military industry, such as ceramic bearings, mirrors, nuclear fuel, gun barrels and other products, are fired by Hot isostatic pressing.

In addition, microwave sintering, arc plasma sintering, and self propagating sintering technologies are also being developed and studied. In order to enhance alumina ceramics and significantly improve their mechanical strength, a new strengthening process for alumina ceramics has been introduced abroad. This process is novel and simple, and the technical means adopted are to use electron ray vacuum coating, sputtering vacuum coating, or chemical vapor evaporation coating methods on the surface of alumina ceramics. A layer of silicon compound film is deposited, and heated at 1200 ℃~1580 ℃ to toughen the alumina ceramics. The mechanical strength of reinforced alumina ceramics can be significantly increased from the original foundation, resulting in ultra-high strength alumina ceramics.

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