Ceramics

 

Introduction

1. Ceramics are Inorganic and nonmetallic materials consisting of metallic and nonmetallic elements which are bonded together primarily by ionic and covalent bonds. Ceramic are generally based on an oxide, nitride, boride, or carbide, that are fired at a high temperature.
2. The word Ceramic has been derived from Ancient Greek word kéramos which means “potter’s clay”. Though the earliest ceramics were pottery, the term now encompasses a large group of materials.
3. Ceramics may be glazed prior to firing to produce a coating that reduces porosity and has a smooth, often colored surface.
4. Material Science is a branch of science and engineering that investigates the relationship between the structure of materials at the atomic or molecular level and their physical properties at the macroscopic level. Ceramics is the oldest branch of materials science.
5. Ceramography is the science of preparation and characterization of ceramics.
6. Cermet is a type of composite material containing ceramic and metal.

 

Properties

1. Since Ceramics include a wide variety of materials, hence it is difficult to generalize their characteristics. 
2. Most ceramics exhibit the following properties: 
   1. High hardness
   2. Usually brittle, with poor toughness
   3. High melting point
   4. Chemical resistance
   5. Poor electrical and thermal conductivity
   6. Low ductility
   7. High modulus of elasticity
   8. High compression strength
   9. Optical transparency to a variety of wavelengths
3. Exceptions include superconducting and piezoelectric ceramics.

 

Uses

1. White-wares –  cookware, pottery, and wall tiles. 
2. Structural ceramics – bricks, pipes, roofing tiles, and floor tiles. 
3. Technical ceramics – bearings, special tiles (e.g. spacecraft heat shielding), biomedical implants, ceramic brakes, nuclear fuels, ceramic engines, and ceramic coatings. 
4. Refractories are ceramics used to make crucibles, line kilns, and radiate heat in gas fireplaces.
5. Another classification is based on indoor and outdoor usage;
   1. Indoors – Refractory bricks, Tiles, Kitchenware, Porcelain enamels for appliances (for example, stock pot), Sanitary ware, Lighting fixtures, Decorative pottery
   2. Outdoors – Roof tiles, Garden items, Bridges and roads, Concrete tennis court, Sport items.