Thermal expansion and Young's modulus evolution of fused silica and crystalline silica-containing materials

Fused silica bricks (FSBs) with exceptional thermal shock resistance are frequently used to repair localized damage in coke ovens and are hold promising candidates for the efficient construction of new coke ovens. To maximize their utilization, the effects of thermal history on the thermal expansion and Young's modulus evolution of FSBs were investigated in comparison to crystalline silica bricks (CSBs). Due to the gradual phase transformation of fused silica into cristobalite, the thermal expansion of FSBs are sensitive to the thermal cycle; both silica materials exhibit an increase in thermal expansion after five cycles at 1200 degrees C, whereas the thermal expansion of CSBs is five times greater than that of FSBs. When the testing temperature is less than 1000 degrees C, Young's modulus of CSBs is more sensitive to the thermal history, which is caused by phase transformation-induced microcracks. This sensitivity reduces when the testing temperature is 1200 degrees C, as microcracks healed by liquid phase as well as the softening of residual glass phase. By contrast, when the testing temperature is 1200 degrees C, Young's modulus of fused silica specimens is sensitive to the thermal history owing to the microcracks caused by the gradual phase transformation of fused silica to cristobalite.