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Write preparation and properties of dolomite bricks and silicon carbide.
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DOLOMITE BRICKS

Preparation:

They are made by mixing calcined dolomite (CaO + MgO) with equimolar proportion of silica as binding material. They are fixed at 1500oC for about 24 hours

Properties:

Advantages: They can withstand a load of 3.5 kg/cm2 at 1650oc.’they are not much resistant to thermal variations.

Limitations: Less strong, more porous and have more softness and shrinkage.

Uses:

  • Open-hearth furnaces
  • Repair works
  • Electric furnace lining, Bassemer converter, ladle-lining etc.
  • Cheap substitute for magnesite bricks.

SILICON CARBIDE

Preparation:

They are made from sand and coke which are properly mixed and saw dust and a little salt are added to it. Mixture is then fired at $1500^oC$ in an electric furnace. After the further processes, the mixture is then finally shaped, dried and fired at a temperature of $2000^oC$.

$$SiO_2 + 3C → SiC + 2CO$$

Properties:

Superior strength, high density, high abrasion and chemical resistance, high thermal conductivity and low thermal expansion.

Uses:

  • Coke ovens
  • Muffle furnaces and floor of heat treatment furnace
  • Heating element in the form of rods and bars etc.
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