Ceramics

Ceramics are basically inorganic crystalline materials characterised by low ductility & high melting point. These materials are processed through methods other than melting. Ceramics consist of metallic & non-metallic elements that are bonded together by ionic and/or covalent bonds. They are generally generated by powder compacting and sintering at high temperatures.

In general ceramic materials are hard and brittle with very little toughness and ductility. Their inability to deform plastically is mainly due to directional ionic and/or covalent bonds which leave no free electrons. Because of some reason the ceramics are bad conductors of heat and electricity. Their engineering application makes use of electrical and thermal insulating properties. The inherent chemical stability & strong bonding make ceramic quite capable of surviving in hostile environment. High temperature application is one of such situation.

Clay, silica (flint) & feldspar form the basic ingradients of traditional ceramics. Main constituents of clay are hydrated aluminium silicate (Al₂O₃, SiO₂, H₂O). Small amounts of other oxides such as those of Fe, Ti, Ca, Mg, Na and K are also present. While SiO₂ provides stability against high temperature feldspar, (K₂O, Al₂O₃, 6SiO₂) produces glass bond between of refractory components. Traditional ceramics are normally utilized in form of tiles and bricks for construction or as electrical porcelain for electrical insulators. In its latter form this material is highly standardised for electrical industry and large variations are available. Still another class of ceramics recognized as engineering ceramics typically are made up of pure compounds like silicon carbide (SiC), aluminium oxide (Al₂O₃), and silicon nitride (Si₃N₄). These engineering ceramics are utilized for high temperature applications.