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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 >LAXS and Al-27 MAS NMR studies on the temperature-induced changes of non-crystalline single phase type mullite precursors
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LAXS and Al-27 MAS NMR studies on the temperature-induced changes of non-crystalline single phase type mullite precursors

机译：LAXS和Al-27 MAS NMR研究温度引起的非晶单相莫来石前体的变化

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摘要

The structural short-range-order of heat-treated non-crystalline precursors with stoichiometric mullite composition (72 wt% Al2O3, 28 wt% SiO2) has been analyzed by large angle X-ray spectroscopy (LAXS), and by Al-27 nuclear magnetic resonance (NMR) spectroscopy under magic angle spinning (MAS) conditions. The precursors were prepared from tetraethoxysilane (TEOS) and aluminium-sec-butoxide (Al(OBu(5))(3)) by a special slow hydrolysis method. Al-27 MAS NMR analyses reveal that the heat-treated mullite precursors have three different Al sites, which, according to literature data are assigned to tetrahedral (fourfold coordinated) Al-[4], pentahedral (fivefold coordinated) Al-[5], and octahedral (sixfold coordinated) Al-[6]. The fraction of Al-[5] increases with the calcination temperature, whereas the Al-[4] and Al-[6] percentage 27 decrease. The results of X-ray radial distribution function (RDF) calculations are consistent with the Al NMR data, The RDF indicates a gradually increasing degree of polymerization of TO4 (T=Al and Si), AlO5, and AlO6 polyhedra with the calcination temperature.
机译：具有化学计量莫来石成分（72 wt％Al2O3，28 wt％SiO2）的热处理非晶态前体的结构短程结构已通过大角度X射线光谱（LAXS）和Al-27核分析魔角旋转（MAS）条件下的磁共振（NMR）光谱。通过特殊的缓慢水解方法，由四乙氧基硅烷（TEOS）和仲丁醇铝（Al（OBu（5））（3））制备前体。 Al-27 MAS NMR分析显示，热处理的莫来石前体具有三个不同的Al位点，根据文献数据，这些位点分别为四面体（四重配位）Al- [4]，五面体（五重配位）Al- [5] ，以及八面体（六重配合）Al- [6]。 Al- [5]的比例随着煅烧温度的增加而增加，而Al- [4]和Al- [6]的百分比27降低。 X射线径向分布函数（RDF）的计算结果与Al NMR数据一致，RDF表示随着煅烧温度的升高，TO4（T = Al和Si），AlO5和AlO6多面体的聚合度逐渐增加。

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