Ceramics

CERAMICS

INTRODUCTION

A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous (e.g., a glass). Because most common ceramics are crystalline, the definition of ceramic is often restricted to inorganic crystalline materials, as opposed to the noncrystalline glasses.

The earliest ceramics were made from clay, either by itself or mixed with other materials, hardened in fire. Later ceramics were glazed and fired to create a colored, smooth surface. Ceramics now include domestic, industrial and building products and art objects. In the 20th century, new ceramic materials were developed for use in advanced ceramic engineering; for example, in semiconductors.

The ceramic products are broadly divided into three categories1. Clay products2. Refractories3. Glass

Clay Products – Tiles

1. Common tiles – These tiles have different shapes and sizes. They are mainly used for paving, flooring and roofs.

2. Encaustic tiles – These tiles are used for decorative purposes in floors, walls, ceilings and roofs.

Characteristic features of a good tile;

3. It should be free from any cracks, flaws and bends.4. It should be in regular shape and size.5. It should be hard and durable.6. It should be well burnt.7. It should fit properly when placed in position.8. It should possess uniform color

Common tiles

Drain tiles – used in water logged areas to convey irrigation water.

Floor /paving tiles – available in different colors, easier to lay, lighter than marble, scratch proof, anti-slip, and do not require polishing.

Roof tiles – they are used to serve as covering for pitched roof. The varieties are;

Allahabad Tiles

Corrugated tiles

Flat tiles

Flemish tiles

Guna tiles

Mangalore tiles

Pan tiles

Terra-Cotta

Strong, Durable, Colors, Cheaper, Easily cleaned, Easily moulded, light in weight, fire-proof, resistant to weathering.

Refractories

Firebricks for furnaces and ovens. Have high Silicon or Aluminium oxide content.Brick products are used in the manufacturing plant for iron and steel, non-ferrous metals, glass, cements, ceramics, energy conversion, petroleum, and chemical industries.

Used to provide thermal protection of other materials in very high temperature applications, such as steel making (Tm=1500°C), metal foundry operations, etc.

They are usually composed of alumina (Tm=2050°C) and silica along with other oxides: MgO (Tm=2850°C), Fe2O3, TiO2, etc., and have intrinsic porosity typically greater than 10% by volume.

Specialized refractories, (those already mentioned) and BeO, ZrO2, mullite, SiC, and graphite with low porosity are also used.