What Are The Common Firing Techniques For Alumina Ceramics?

The technical method of densifying granular ceramic bodies and forming solid materials is called sintering. Sintering is a method of removing voids between particles in the body of the billet, removing small amounts of gas and impurities organic matter, and allowing particles to grow and combine with each other to form new substances.

Electric furnaces are widely used as heating devices for firing. In addition to atmospheric sintering, which is also known as pressureless sintering, there are also hot press 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. Hot isostatic pressing sintering uses high-temperature and high-pressure gas as the pressure transfer medium, which has the advantage of uniformly heating in all directions and is very suitable for sintering complex shaped products. Due to its uniform structure, the material properties are improved by 30-50% compared to cold pressed sintering. Improved by 10-15% compared to conventional hot pressing sintering. Therefore, some high value-added alumina ceramic products or special components required for national defense and military industry, such as ceramic bearings, reflectors, nuclear fuel and gun barrels, are fired using hot isostatic pressing method.

In addition, microwave sintering, arc plasma sintering, and self propagating sintering technologies are also under development and research.

Precision machining and packaging processes

Some alumina ceramic materials still require precision processing after sintering. Products that can be used as artificial bones require a high surface finish, like a mirror, to increase lubrication. Due to the high hardness of alumina ceramic materials, it is necessary to use harder grinding and polishing brick materials for precision processing. Such as SIC, B4C, or diamond. Usually, grinding is carried out step by step with coarse to fine abrasives, and the final surface is polished. Generally,<1 can be used μ Grind and polish Al2O3 micro powder or diamond paste with a diameter of m microns. In addition, laser processing, ultrasonic processing, grinding, and polishing methods can also be used.

Strengthening process of alumina ceramics

In order to enhance alumina ceramics and significantly improve their mechanical strength, a new alumina ceramic strengthening process is proposed. This process is novel and simple. The technical means adopted are to use electron ray vacuum coating, sputtering vacuum coating or chemical vapor deposition methods on the surface of alumina ceramics, to deposit a layer of silicon compound thin film, and heat treatment at 1200 ℃ to 1580 ℃ to toughen the alumina ceramics.

The mechanical strength of reinforced alumina ceramics can be significantly increased on the original basis, resulting in alumina ceramics with strength.

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