The Effect of Firing Temperature on the Properties of Silica Refractory Bricks Containing Nano-silica Sol Prepared by Gel-casting

In this study, the silica refractory brick containing nano-silica sol was prepared via gel casting method and then, the effect of firing temperature on the properties of this brick was investigated. The firing temperature and thermal behavior of composition were evaluated by use of STA. Besides, the physical properties, mechanical strength, phase composition and microstructure of these refractory bricks were evaluated after firing at 1150-1400 °C range. The results showed that the firing temperature has a great effect on the properties of these bricks. The nano silica sol transforms from amorphous to cristobalit phase at 1200 °C due to its high surface area. The formation of needle-like particles of cristobalit at 1200 °C leads to increasing of porosity. Microstructural evaluations revealed that cristobalit acts as bonding phase between silica particles which, leads to increasing of mechanical strength. The increasing of firing temperature above 1200 °C leads to improvement of sintering process, decreasing of porosity and then, improvement of mechanical strength. According to results, the suitable firing temperature was found at 1300 °C.