Mineralogical Composition Of Silica Brick

Silica brick is a type of acid refractory material, mainly composed of tridymite, cristobalite and a small amount of residual quartz and glass phase. It has good resistance to acid slags, high softening temperature under load up to 1640 ~ 1670 ℃ and good volume stability at high temperature after long-term use. 

The mineralogical composition of silica brick mainly includes tridymite and cristobalite, as well as a small amount of quartz and glass phase. Tridymite, cristobalite and residual quartz have big volume changes at low temperature due to the change of crystal phase, thus it has bad thermal stability. During use, under 800℃, it should be heated and cooled slowly to avoid cracks. 

 

SiO2 has seven crystal variants and a amorphous variant. Those variants can be divided into two types. One is quartz, tridymite and cristobalite. Their crystal structure is very different, and transformation between each other is very slow. The other is subspecies of variants mentioned above. They have similar structure and the transformation between each other is fast. 

 

Its properties and manufacturing process is closely related to the transformation of SiO2 crystal. True specific gravity is an important indicator of the quality. Common silica brick should be under 2.38 and high quality silica brick should be under 2.35 or less. A low true specific gravity means a high content of tridymite and cristobalite and a low content of residual quartz. Silica brick with a low true specific gravity has small residual linear expansion and the strength will not decease too much during use. 

 

Silica brick is widely used in the carbonization chamber and the combustion chamber of coke ovens, the crown of glass furnaces and firing kilns of silicate products.