The ceramic materials which might be used in place of other engineering materials such as metals, wools or plastics are termed as engineering ceramics. These materials withstand high temperatures, resist greater pressures have superior mechanical properties and can protect against corrosive chemicals.
BASIC RAW MATERIALS
The three main raw materials used for ceramic industry are clay, feldspar and sand.
It is hydrated aluminum silicate. Some common clays are:
(i) Kaolinite (AI2O3.2SiO2.2H2O0 )
(ii) Montmorillortite (Mg, (Ca ) O, Al2O3.5SiO2.nH2O)
(iii) Illite (K2O, MgO, Al2O3. SiO2.H2O all in variable amounts).
There are three common types of feldspar,:
(i) Potash feldspar. (K2O. Al2O3. 6SiO2)
(ii) Soda feldspar. (Na2O. Al2O3• 6SiO2)
(iii) Lime feldspar. (CaO. Al2O3. 6SiO2).
Sand or flint (SiO2) is the main constituent of ceramic industry. It is used as an opener for reducing the shrinkage of the clay. In addition to the principal raw materials, a wide variety of other minerals, salts and oxides are used as fluxing agents and special refractory ingredients. Some common fluxing agents which lower temperatures are borax, boric acid, soda ash, sodium nitrate, pearl ash, apatite, cryolite, iron, lead oxide etc