Sol-Gel Synthesis of Protoenstatite and a Study of the Factors That Affect Crystallization

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• 作者：Steven A. Jones ; James M. Burlitch ; J.C. Duchamp and T.M. Duncan
• 关键词：sol ; gel ; synthesis ; protoenstatite ; 29Si ; NMR ; freeze ; drying
• 刊名：Journal of Sol-Gel Science and Technology
• 出版年：1999
• 出版时间：1999
• 年：1999
• 卷：15
• 期：3
• 页码：201-209
• 全文大小：77 KB

文摘

Three different magnesium silicate sols were prepared from Mg(OMe)₂ and TEOS for which hydrolysis with H₂O₂ and H₂O was under stoichiometric, stoichiometric, or over stoichiometric. Xerogels were prepared from the sols by simple evaporation, spray-drying, or freeze-drying. The freeze-dried precursor formed mostly protoenstatite, a high-temperature polymorph of enstatite (MgSiO₃) that is generally not stable at room temperature; the other precursors formed mixtures of protoenstatite and clinoenstatite. The three xerogels and their calcined products were studied with XRD, HTXRD, BET, carbon analysis, TG/DTA and29 Si-NMR. Residual carbon was found to be an important factor in the crystallization, and 29Si-NMR spectroscopy was found to be a better tool than XRD to assess the phase purity of protoenstatite.