The word ‘ceramics’ has its origin in the Greek word Keramos, which means “potter’s clay”. Today the word refers to all types of pottery, whatever its composition or use. All ceramics are made from various clays, together with materials such as flint, felspar or china clay.
However, strictly speaking ceramics are compounds of silicon, carbon, oxygen and nitrogen combined with other elements like sodium, potassium, calcium, barium etc. The principal raw material used in the manufacture of ceramics is clay. These clays are formed by decomposing natural rocks which are exposed to the wearing action of air and water. Granite is the rock which provides the bulk of useful clays. It is composed of quartz, mica, felspar etc. These clays are crushed and ground into fine particles. The particles are mixed and moisted with right proportion of water, which makes the particles flexible for shaping. Different methods are used for getting the desired shape.
After the product has dried, it is heated. This process takes place in a special type of furnace called kiln. Ceramics are heated at temperatures ranging from 650°C to 1650°C. Firing makes the products hard in the desired shape and turns their glaze into a smooth coat. This process also makes the product leak-proof, durable and decorative.
Clay and shale are used to make building products, such as bricks and drain pipes. Calcium silicates are used in making the cement. Gypsum is used in the manufacture of plaster. Porcelain is used in making bath-tubs, sinks and toilets. Bowls, cups and plates are also made from porcelain. Artificial bone joints and false teeth are made from porcelain.
Some ceramics such as alumina and porcelain, do not conduct electricity and used as insulators in automobile spark plugs, electric power lines. Some types of capacitors are made from Barium titanate which is a ceramic material. Refractories are another important group of ceramic products used for lining furnaces. They resist heat and chemical action. Alumina, silica and magnesium compounds are used as refractories. Uranium oxide ceramics are used as fuel elements for nuclear reactors. Alumina in the form of ruby is used in the making of lasers, which produce extremely strong light beams.