Ceramics can be defined as heat-resistant, non-metallic, inorganic solids that are made up of compounds from metallic and non-metallic elements. The word ceramic is derived from the Greek word keramos, meaning burnt earth.
Traditional ceramics are made from natural materials such as clay (often mixed with other raw materials into the desired shape) that have been hardened by heating at high temperatures in special ovens called kilns. Binders such as bone ash are sometimes added to the clay to promote strong bond formation which makes the ceramic resistant to breakage. The common clay used to make flower pots and roof tiles is usually red-orange due to the presence of iron oxides. White ceramics are made from rarer (and thus more expensive) white clays, primarily kaolin.
Raw Materials of CeramicsRaw materials used to manufacture ceramics include silica, sand, quartz, flint, silicates and aluminosilicates (e.g., clay and feldspar).
General Classification of Ceramics
Pottery: It is a generic term for ceramics that contain clay and are not used for structural, technical or refractory purposes.
Whiteware: It refers to ceramic ware that is white, ivory or light grey in colour after firing. Whiteware is further classified as earthenware, stoneware, chinaware, porcelain and technical ceramic.
Earthenware: It is defined as a glazed or unglazed non-vitreous (porous) clay-based ceramic ware. Applications for earthenware include artware, kitchenware, ovenware, tableware and tile.
Stoneware: It is a vitreous or non-vitreous ceramic ware of fine texture, made primarily from non-refractory fire clay or some combination of clays, fluxes, and silica that, when fired, has properties similar to stoneware made from fire clay. Applications include artware, chemicalware, cookware, drainpipe, kitchen ware, tableware and tile.
Chinaware: It is a vitreous ceramic ware of zero or low absorption after firing that are used for non-technical applications. Applications for chinaware include artware, ovenware, sanitaryware and tableware.
Porcelain: It is defined as a glazed or unglazed vitreous ceramic ware for technical purposes. Applications for porcelain include artware, chemicalware, insulators and tableware.
Technical ceramics: These include vitreous ceramic whiteware that is used for products such as electrical insulation or for products such as chemical, mechanical, structural or thermal applications.
Properties of Ceramics
Ceramics are hard, chemically inert, refractory (can withstand very high heat without deformation) and poor conductors of heat and electricity. They also have low densities.
Uses of Ceramics
- It is used as refractories in furnaces and as durable building materials.
- It is used as common electrical and thermal insulators in the manufacture of spark plugs, telephone poles, electronic devices and the nose cones of space craft.