The Effect of Sintering Temperature on Porous Silica Composite Strength

The effect of sintering temperature on porous silica composite strength was studied by discussing three factors, namely crystal phase, glassy phase and porosity. The fired products of clay and silica are composed of crystalline phase and glassy phase. The crystalline phases consist of alpha-quartz and mullite and the glassy phase contains a disordered silica network. With the increase of sintering temperature up to 1360°C, the crystalline silica decreased gradually. The disappearing silica dissolved into the glass and became a part of glass network and resulted in the enhancement of glass strength. This change in glass played an important role in the improvement of sample strength. At the same time, the increase of sintering temperature promoted the densification of samples and reduced the porosity of products, which also contribute to the increase of sample strength. When the sintering temperature is up to 1390°C, the silica in glass tended to convert to cristobalite with the expansion of glassy phase. This expansion weakened the connection of atoms in glass network and brought some closed pores into products, which led to the decrease of sample strength.