AlF3晶种系数和煅烧温度对制备六边形片状α-Al2O3的影响

Effects of AlF3 and calcination temperature on preparation of hexagonal-shaped α-Al2O3

以一水软铝石作为前驱体,AlF3晶种为添加剂,在较低煅烧温度下制备结晶度好和形貌规整的六边形片状α-Al2O3.在晶种系数为2%的条件下,对煅烧产物的差热-热重-质荷（DSC-TG-MS）分析验证了气固反应的成核机理,结果表明：AlO-F气体通过气固反应促进α-Al2O3成核相变,同时释放出HF.实验同时研究了AlF3晶种和煅烧温度对煅烧产物物相、形貌、粒度和比表面的影响.结果表明：微量AlF3晶种（晶种系数为0.5%）即可促进α-Al2O3相变成核,随着晶种系数的增加,这种效果越明显,但同时也会增大其粒度,减少比表面积;煅烧最佳条件为：温度850℃,晶种系数2%,煅烧时间4 h,在此条件下,一水软铝石可以全部转化为结晶度良好的α-Al2O3,其形貌为规整的六边形片状结构.

A hexagonal α-Al2O3 with good crystallinity and regular morphology was prepared at lower calcination temperature by using boehmite（Al OOH） as precursor and AlF3 seed as additive. The possible mechanisms were investigated by DSC-TG-MS analysis under the condition of AlF3 seed coefficient 2%,which indicates that a transition compound（Al-O-F） promotes the nucleation phase transition of α-Al2O3 through gas-solid reaction,and releases HF simultaneously. Furthermore,the effects of AlF3 coefficient and calcination temperature（T） on the phase,morphology,size,and specific surface area were investigated. Results show that light AlF3 seeds can enhance the crystallinity of α-Al2O3. When the AlF3 coefficient increases from 0. 5% to 10%,the hexagonal-shaped structure becomes clear,but its size increases and its specific surface area decreases. Boehmite can completely change into high-crystallinity,hexagonal-shaped α-Al2O3 under the best condition of T = 850 ℃,AlF3 seed coefficient 2%,and constant calcination time of 4 h.