The word Ceramics is derived from the Greek word Keramos which means potter’s earth or clay. Therefore, ceramics may be considered to be material made from naturally occurring clay or earth. Scientifically, ceramics are compounds of metallic and non-metallic elements. There are also manufactured ceramic materials such as diamond, SiC and Si3N4 and so on. In modern applications, a broader definition applies to the term ceramic, that is everything that is not a metal or organic material. Ceramics are inorganic as well as non-metallic materials which have been processed or used at high temperatures.
The American Ceramic society has defined ceramic products as those manufactured “by the action of heat on raw materials, most of which are of an earthy nature — while of the constituents of these raw materials, the chemical element silicon, together with its oxide and the compounds thereof, occupies a predominant position.” That branch of knowledge which deals with the expertise of manufacturing and treatment of ceramic materials is called ceramic engineering.
There are various types of ceramic products which we have classed under four distinct categories-
1. Structural – it includes roof and floor tiles, pipes and bricks.
2. White wares – they include objects like decorative, sanitary ware, table ware and wall tiles. The examples of white ware ceramics are stone ware, porcelain, bone china and earthen ware.
3. Refractories like glass and steel building crucibles, gas fire radiant and kiln linings.
4. Technical or fine ceramics. such products include tiles applied in the space shuttle program, ballistic fortification, bio-medical implants, missile nose cones, nuclear fuel uranium oxide pellets and jet engine turbine.
The various properties of ceramics are discussed below-
1. MECHANICAL PROPERTIES- they are crystalline or amorphous and are usually covalently bonded or iconic substances. Ceramic materials also show plastic deformations.
2. ELECTRICAL PROPERTIES- they are semi conductors and most of them are transitional metal oxides. However under extremely low temperatures some ceramics become superconductors.
CLASSIFICATION OF CERAMICS-
They are classified as non -crystalline and crystalline ceramics. The non-crystalline ceramics are formed from melts and are called glass ceramic. They are produced after a great range of processing whereas the crystalline ceramics do not require much doling out.
Apart from the ones discussed above, ceramics have a wide range of usage
1. It is used in making knives and ceramic knives are sharper than steel knives. Though they are brittle, their blades are more durable.
2. Ceramics like alumina and boron carbide are used as “Small Arms Protective Inserts”
3. Steel can be replaced by ceramic balls in ball bearings. Due to their hardness they have a longer lifetime. Their electrical insulating capacities are also valuable in bearings but a major drawback is their high cost.
4. Ceramic engines can be used in laboratories due to their high fuel efficiency and they do not need any cooling system. However mass production is not possible because cracks can easily develop in ceramics which may result in dangerous equipment failure.
5. Nowadays bio-ceramics are made which include synthetic bones and dental implants.
6. High tech ceramic is also employed in making watch cases.