Preparation And Application Of Al₂O₃-SiO₂ Sol-Gel

Al₂O₃-SiO₂ xerogel was prepared by using the sol-gel with vacuum freeze-drying technology (VFD) through three different Sol-agents of ammonia, ammonium carbonate and urea. The influence of OH- on aluminum silica sol-gel was analyzed in the text. The influence of pH, temperature treated on the grain size of mullite was analyzed through phase,surface morphology and performance of mullite ultrafine powder. The influence of Al-Si ultrafine powder on mullite castable was analyzed by the conventional detection of castable properties. The thermodynamic of mullite formed by Sol-Gel-VFD was analyzed too and the apparent activation energy,the apparent factor of mullite formed by Al-Si xerogel was concluded in the final. There were some conclusions as follow as:1.Through the analysis of XRD,TG-DSC, when OH- was accessed uniformly to the Al-Si precursor solution, and Lower alkalinity was obtained in the solution, the single-phase gel made of homogeneous Al-O-Si-O network was formed and xerogel was transformed directly to mullite in heat treatment process. When OH- was entered nonuniformly the Al-Si precursor solution, so dropping caused local high alkalinity or was entered uniformly, but higher alkalinity was got in overall solution, the Al-Si gel included the rich-Al₂O₃ and rich-SiO₂. Al-Si spinel was generated at the first, and then converted into mullite in heat treatment process.2.Through the analysis of SEM,XRD,BET, the size of mullite powder produced by Sol-Gel-VFD technology was in the nanometer range and the particles was uniform.3.Through the performance analysis of castable, when the Al-Si ultrafine powder activated in 400℃at ratio of 0.5% was entered mullite castable, the properties of the castable were improved.4.Through the TG curves applied Kissinger equation, the apparent activation energy and apparent factor of mullite generated by Al-Si xerogel were got. Their values were E k=838.69kJ?mol-1,ln A k=65(A k=1.7×1028/s-1)...