莫来石微晶的溶胶-凝胶法制备及其表征

Preparation and Characterization of Mullite Microcrystallites by Sol-gel Method

以无机铝盐、正硅酸乙酯(TEOS)为主要原料,采用溶胶-凝胶法制备了莫来石微晶粉体,并运用X射线衍射(XRD)、扫描电子显微镜(SEM)以及综合热分析(TG-DSC)等方法对制备的莫来石粉体进行了表征。研究了原料种类、后处理温度以及前驱液pH值对莫来石粉体的相组成以及显微结构的影响。结果表明在本研究范围之内,发现Al(NO3)3.9H2O为Al盐时,比AlCl3.6H2O容易制备出纯相的莫来石粉体。热分析显示莫来石的开始形成温度为1250℃。XRD分析表明要制备纯相的莫来石粉体,后处理温度要达到1300℃。前驱液pH值对粉体的相组成和形貌有很大的影响。随着pH值的减小,莫来石粉体的纯度增加,相貌由片状向棒状和粒状转变。当pH=3时,可获得单一物相的莫来石粒状微晶。

Mullite microcrystallites were prepared by Sol-gel process using TEOS and inorganic aluminum salts as the raw materials. The phase composition and microstructures of prepared mierocrystallites were characterized by X-ray diffraction （XRD）, scanning electron microscopy analysis （SEM） and thermogravimetry-differential scanning calorimeter （TG-DSC）. The influence of the source material of aluminum salts and the later heat treatment temperature on the phases and microstructures of the powders were investigated. Results show that the initial temperature of the mullitization of gels is about 1250 ℃ according to TG-DSC analysis, but the temperature of preparation of pure mullites should be at 1300 ℃ from XRD analysis. The pH value has a important impact to the phase composition and the morphology of mullites. The purity of mullites increased and the morphology transformed from sheetlike to rodlike and grainlike with the pH vaule decreased. It is also show that the single phase microcrystallites can be obtained at pH value of 3