Ceramic materials are inorganic and non-metallic materials. The crystal structure of ceramics is more complex because at least two elements are involved in making a ceramic compound. The ceramic materials exhibit useful properties like strength and hardness, high melting temperatures, chemical resistance, low thermal, and electrical conductivity. However, they also display brittleness and sensitivity to flaws. Ceramics include a wide variety of substances such as brick, stone, concrete, glass, abrasives, porcelain enamels, dielectric insulator, and high-temperature refractories.
Ceramic materials are obtained by firing them at high temperatures. Traditional ceramics products are made from common naturally occurring minerals such as clay and sand for the pottery, bricks, porcelain, etc. The clay materials are the end result of a chemical reaction between the constituents of the earth and its environment. They are used as structural materials where there is resistance to high temperature and oxidation, such as in steel and glass manufacture.
Ceramics materials that withstand high temperatures under various environments are termed as ‘refractories’. Refractories such as carbides, nitrides, and oxides (SiO2, Al2O3, SiC, and MgO) having a high melting point and wear resistance. They are used in extractive metallurgy, cement kilns and glass manufacturing industries as protected lining materials.
CLASSIFICATION OF CERAMICS
The ceramics consist of compounds of metallic and non-metallic elements. Many combinations of metallic and non-metallic atoms are possible and several structural arrangements of each combination are produced. A wide range of ceramic materials are found in nature and are used for various engineering applications.
The general classification of ceramics is as follows:
- Plain concrete
- Rocks and stones
- Clay and clay products
PROPERTIES OF CERAMICS
The following are the properties of ceramic materials:
- High hardness and are resistant to wear.
- Low tensile strength; hence, generally fail due to stress concentration on cracks.
- Higher compressive strength.
- Low fracture strength and fail in a brittle manner.
- Majorly highly resistant to all chemicals except hydrofluoric acid and, to some extent, hot caustic solutions.
- Oxides of ceramics are completely resistant to oxidation even at very high temperatures.
- Favorable properties at high temperatures and under oxidizing conditions.
- Jindal, U. C. (2012). Material Science and Metallurgy. Pearson Education India.