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首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Phase segregation of non-stoichiometric aluminosilicate gels characterized by Al-27 and Si-29 MAS-NMR
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Phase segregation of non-stoichiometric aluminosilicate gels characterized by Al-27 and Si-29 MAS-NMR

机译：以Al-27和Si-29 MAS-NMR为特征的非化学计量铝硅酸盐凝胶的相分离

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摘要

Polymeric aluminosilicate gels with Al2O3/SiO2 molar ratios of 1.3/2, 2.5/2, 3/2 and 4.7/2 were prepared by gelling a mixture of tetraethoxysilane and ethyl acetoacetate aluminium diisopropoxide. Mullite, without any other crystalline phase, directly crystallizes from the gel matrix at about 1000 degreesC for all investigated samples. The Al2O3 or SiO2 crystalline phase can only be detected at relatively high temperatures accompanying the modification of mullite in the lattice structure. Al-27 and Si-29 MAS-NMR studies indicate that segregation of Al and Si atoms occurs in all samples below 900 degreesC in the amorphous state, regardless of the gel composition. However, the species of segregated units are very different and strongly dependent on the composition of the starting gels. This segregation may not cause the exothermic effect in differential thermal analysis examination, but it appears to be responsible for the composition change behavior of crystalline mullite with different heat treatment. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 19]
机译：通过使四乙氧基硅烷和乙酰乙酸乙酯乙基二异丙醇铝的混合物胶凝来制备Al 2 O 3 / SiO 2摩尔比为1.3 / 2、2.5 / 2、3 / 2和4.7 / 2的聚合铝硅酸盐凝胶。对于所有研究的样品，莫来石没有任何其他结晶相，直接在约1000℃下从凝胶基质中结晶。 Al2O3或SiO2晶相只能在相对高的温度下伴随着莫来石在晶格结构中的改性而被检测到。 Al-27和Si-29 MAS-NMR研究表明，在900℃以下的所有样品中，非晶态的Al和Si原子都会发生偏析，而与凝胶组成无关。但是，分离单元的种类非常不同，并且强烈取决于起始凝胶的组成。这种偏析可能不会引起差示热分析检查中的放热效应，但似乎是造成了采用不同热处理的结晶莫来石成分变化行为的原因。 （C）2002 Elsevier Science B.V.保留所有权利。 [参考：19]

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