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Introduction to Ceramics
Ceramics are special materials with many applications in almost all the engineering disciplines. But their importance has often been underestimated due to the fact that many people believe that ceramics are all about pottery and tiles. Today's ceramics industry is one of most rapidly advancing concerns in many parts of the world including USA, where the advanced ceramic market is over 13 billion US dollars. Ceramic industry began to expand as a modern industry with the attribution of new techniques and knowledge gained in the 1970s. Since then it has also been one of most competitive industries in the market.
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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.
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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, sanitaryware, tiles, structural clay products, refractories, blocks, and electrical porcelain are some of the products of traditional ceramics.
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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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Applications of Advanced Ceramics
In electronic and electrical industries advanced ceramic materials like Barium Titanate (BaTiO3), piezoelectric materials and semiconductor materials are heavily used for producing ceramic capacitors, vibratos, temperature sensors, oscillators, etc. Ceramics used for this type of applications are called functional ceramics. Specific properties of advanced ceramic materials are utilized for their industrial applications. Ferroelectricity is such property in materials like Lead Zirconate Titanate, Lead Titanate, Barium Titanate, etc. Ferroelectric materials have two properties. One is there should be a spontaneous polarization and the other is the polarization should be able to reorient. This property is used to produce applications like sensors, pumps, sonar, microphones, etc.
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There are a number of other applications that are found in the other areas too. Magnetic ceramics are another type of advanced ceramic material that is used for the production of antennas and inductors. Bioceramics like Alumina with high density and purity is used to dental implants. Eye glasses, chemical ware, and the replacement of hips and knees, etc. are some of the applications of bioceramic materials.
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Although traditional ceramics have been in use in ancient civilizations, advanced ceramics is a recently developed field. But they have some extremely important functions and have already shown a rapid growth. Both of these ceramic materials posses significant importance for the industry and it can be expected that the best is yet to come especially in the field of advanced ceramics.