What are the characteristics of refractory material?

The characteristics of refractory material:
Mechanical property
Elasticity modulus of special common silica brick is large. Most have higher mechanical strength of corundum crucible, but compared with the metal material, due to brittleness, the impact strength of corundum mullite sag is very low. Most of the special refractory materials have higher hardness, therefore, wear resistance, resistance to air flow or dust scouring is better. Most of the special refractory material's high temperature creep is relatively small, the largest is molybdenum disilicide. The size of creep is related to crystal size, grain boundary material, porosity and so on.
Thermal property
Thermal expansion: often expressed as linear expansion or volume expansion coefficient. Most of the special refractory material's coefficient of linear expansion is relatively large, only linear expansion coefficient of fused silica, boron oxide, silicon oxide is relatively small.





Use property
Fire resistance: the melting point of special refractory material is almost above 2000 ℃, the highest hafnium carbide (HfC) and tantalum carbide (TaC) is 3887 ℃ and 3877 ℃. Refractoriness is also very high. In oxidizing atmosphere, the use temperature of oxide is even close to the melting point. Nitrides, borides, carbides have higher use temperature than the oxide in the neutral or reducing atmosphere, for example, TaC can be used up to 3000 ° C in N2 atmosphere, BN can be used up to 2800 ° C in Ar atmosphere.
Thermal shock resistance: In special refractory material, due to the low thermal conductivity of beryllium oxide, most of the boride's thermal conductivity is not high, linear expansion coefficient of fused silica is particularly small, so thermal shock resistance is good.
 Electrical property
Most of the high melting point oxide belongs to insulator, in which thorium oxide (ThO2) and stabilized zirconia (ZrO2) have conductivity under high temperature. The resistance of the carbide and boride are small. Some nitride is good conductors of electricity, while others are typical insulators.