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本文是一篇综述,讨论在熔融铝硅酸盐和铝酸盐中Al的两性行为。这是7台金学和岩石学中一个至今尚无可靠结论的问题。作者认为:每个四配位的Ala都含一个配位键,例如Al—O(^Ca Si)或Al—O(^Ca Al)。相应的非桥氧Onb并没有消失,而是变成了三价氧离子。碱性Alb能否出现取决于该体系的酸碱平衡。构筑硅酸盐的键合结构模型时,作者建议用5种Si-O四面体(Qn)作为微结构单元。即,用它们的相对量和微观化学位描述其宏观物性(如组元活度)。为了沟通铝硅酸盐的微观结构与宏观物性,仍可用5种Qn作为微结构单元。其中所含Ala的影响用各种Qn微观化学位的相应变化来反映。对于铝酸盐,建议用Ala-O四面体(Tn)作为微结构单元。 相似文献
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Discrete, well-ordered, single-phase crystals (the Hanic phase) form when powders the bulk composition of Ca5Al6MgSiO17 are allowed to react in the absence of a melt. If, on the other hand, either the powders or crystals of Ca5Al6MgSiO17 are molten and then cooled, complex intergrowths form. These intergrowths consist of modules having the composition and structure
of Ca3Al4MgO10 and gehlenite (Ca2Al2SiO7), forming a polysomatic series in which the modules occur in varied proportions. High-resolution transmission electron microscope
(HRTEM) images reveal the details of these intergrowths. Mass balance is achieved by the formation of this polysomatic series
together with Mg-substituted mayenite (Ca12−xMgxAl14O33). The tetrahedral sheets in gehlenite have close structural similarities to those of Ca5Al6O14. Based on our HRTEM images, we hypothesize chemical substitutions between gehlenite and Ca5Al6O14, resulting in gehlenite-like modules that are depleted in Si and correspondingly enriched in Al and Ca.
Received: 2 August 2000 / Accepted: 18 January 2001 相似文献
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