Study on Mullite Formation Mechanism in Acid and Alkaline

Using C8H20O4Si and Al(NO3)3·9H2O as main raw materials,pure mullite powders were prepared sucessfully by sol-gel method in acid and alkaline using NH3·H2O to control pH value.Endothermic,exothermic and the phase transformation process were obtained in heating process by differential thermal analysis;The course of crystallization was studied by XRD,The Si-O-Al bonds' existing and changing in powders were getted by infrared absorption spectra,Mullite powders' surface characterstics were received by environmental scanning electron microscopy.The result showed that mullite formation process experiences amorphous silicon and amorphous aluminum to Al-Si spinel to mullite.The mullite formation temperature is lower in alkaline than acid,and grain size is smaller in alkaline.