Ceramics are materials made from stony or earthy material taken from the ground. Some ceramics, such as pottery and bricks, are moulded into shape and then baked (fired) to make them set. Glass is a type of ceramic that is heated first and then moulded into shape. Some ceramic materials are able to with-stand very high temperatures and are used for specialist application in industry and engineering.
Ceramic materials are special because of their properties. They typically possess high melting points, low electrical and thermal conductivity values, and high compressive strengths. Also they are generally hard and brittle with very good chemical and thermal stability. Ceramic materials can be categorized as traditional ceramics and advanced ceramics. Ceramic materials like clay are categorized as traditional ceramics and normally they are made of clay, silica, and feldspar. As its name suggests, traditional ceramics are not supposed to meet rigid specific properties after their production, so cheap technologies are utilized for most of the production processes.
Ball clay, China clay, Feldspar, Silica, Dolomite, Talc, Calcite and Nepheline are the common materials used for most of the ceramic products. Each raw material contributes a certain property such as dry strength, plasticity, shrinkage, etc. to the ceramic body. Therefore, by careful selection of materials, desired properties are acquired for the final output. Powder preparation is a major consideration in the ceramic industry. Surface area, particle size and distribution, particle shape, density, etc. each have their own effect on production. Powder has to be prepared to meet required particle size, particle shape, and other requirements for a particular industry. Milling is done to get the desired particle size. Unlike in the, advanced ceramics industry the purity of ceramic powder is not an issue in traditional ceramics.
The traditional ceramics industry originated long ago. Even thousands of years ago it was a well-established practice in many parts of the world. Today there are many divisions of this industry. Pottery, tableware, sanitary ware, tiles, structural clay products, refractories, blocks, and electrical porcelain are some of the products of traditional ceramics.
Advanced ceramics are special type of ceramics used mainly for electrical, electronic, optical, and magnetic applications. This sector is different from traditional ceramics due to the fact that ceramic powder preparation is quite important. Advanced production techniques are employed to assure that the produced ceramic powders possess sufficient purity. Generally chemical reactions are used to produce the ceramic powder such as Sol-gel processing and liquid-gas reactions like NH3 gas and SiCl4 liquid to produce Si3N4. Many of these methods are very costly. Therefore, powder preparation is always a cost factor in the advanced ceramics industry.
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