用高岭土制备片状氧化铝粉体

Preparation of flaky alumina powder using kaolinite

以高岭土和硫酸铝为原料,以硫酸钠为熔盐法的反应介质,按混合料中Al和Si的摩尔比为3,硫酸钠的质量分数为50%配料,经球磨混合均匀后置于刚玉坩埚内,分别于800、900、1 000、1 100和1 200℃下保温3 h,冷却后用蒸馏水浸取熔块,过滤,洗涤,烘干后得到最终产物。XRD分析表明:900℃制备产物的主要物相为莫来石;随着温度的升高,莫来石逐渐分解;1 200℃制备产物的主要物相为α-Al2O3和硅铝酸钠。用氢氟酸溶去产物中的硅铝酸钠和杂质相后进行的SEM分析表明,该产物中的α-Al2O3晶体为规则的六角形片状晶,片晶的边长为1.5～4.5μm,厚度为50～100 nm,且片晶间交错生长。

Flaky alumina powder was prepared using kaolinite and aluminum sulfate as starting materials with AI/Si molar ratio of 3,50 wt% of sodium sulfate as reaction medium,mixing them well in the ball mixer,putting into a corundum crucible and firing at 800,900, 1 000,1 100 and 1 200 ℃ for 3 h, respectively,then filtering, washing with distilled water,and finally drying. The XRD analysis results indicate the main phase of the flaky alumina powder fired at 900 ℃ for 3 h is mullite. As the firing temperature rises,the mullite phase gradually decomposes. The main phases of the product fired at 1 200 ℃ are α-All2O3 and sodium alumJnosilicate. The SEM of the products using HF acid to dissolve sodium aluminosilicate and impurity phase shows that the α-All2O3 crystal is interlocked flaky hexagon with side length ranging from 1.5μm to 4.5 μm and thickness ranging from 50 nm to 100 nm.