排序方式: 共有46条查询结果,搜索用时 15 毫秒
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在不同投料比(SiO2/Al2O3=13.8,19及21)条件下,合成了三种Ω型分子筛原粉.对投料比为13.8的原粉样品进行了四种不同方式的脱铝处理,即水热、SiCl4、EDTA和(NH4)2SiF6处理,而形成了系列脱铝Ω型分子筛样品.对原粉及其脱铝样品进行了29Si和27AlMASNMR测试,确定出样品骨架硅铝比和铝在两种晶体学不等价T位上的占据比率,以探索四种脱铝方法的效果.实验结果与分析表明:在所有样品中,铝原子的占据具有择优B位的倾向;且铝在TA与TB位上的占据比率与合成条件有关;四种处理方式对Ω型分子筛的脱铝效果不尽相同. 相似文献
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采用溶剂蒸发法,在不同的条件下分别获得了具有四次对称和二次对称的Na Cl枝晶、"Z"字形枝蔓晶以及主要由枝晶呈放射状分布的球粒晶。借助于X射线衍射仪、光学显微镜、扫描电镜以及电子背散射衍射仪(EBSD),对Na Cl枝状形貌进行了测试分析。结果表明,Na Cl球粒晶主要由主干沿着<111>方向生长的一系列枝晶组成。Na Cl晶体(111)面网由同号离子组成,且钠离子层与氯离子层相间分布,层与层之间的联结力强,且(111)的面网间距最小,是导致Na Cl枝晶优先沿<111>方向生长的主要原因。溶剂的蒸发速度等环境因素的变化对Na Cl枝状形貌的形成具有很大的影响。 相似文献
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A new compound of 4,4'-diamino-N,N'-diethyl bisbenzenesulfamide (C18H26N4O4S2,Fw = 426.55) has been synthesized and its structure was determined by X-ray crystallography method. The crystal belongs to the monoclinic system, space group P21/c with a = 10.0623(9), b =13.6759(13), c =15.5309(14) (A),β = 100.482(2)°, V= 2101.6(3)(A)3, Dc = 1.348 g/cm3, F(000) = 904,μ = 0.285 mm-1, Z = 4, the final R = 0.0512 and wR = 0.1363 for 3485 observed reflections with I >2σ(Ⅰ). The structure of the title compound is pseudo secondary axisymmetric, and the two sulfamide-groups show distorted tetrahedral configurations. 相似文献
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Molecular self-assembly behavior of mono[6-O-6-(4-carboxyl-phenyl)]-β-CD in solution and solid state
FANZhi ZHAOYanli LIUYu 《科学通报(英文版)》2003,48(15):1535-1538
A novel modified cyclodextrin, mono[6-O-6-(4-carboxyl-phenyl)]-]-β-CD (1), has been synthesized by the reaction of mono[6-(p-toluenesulfonyl)]-β-CD with 4-hydroxybenzoate, and its molecular self-assembly behavior in both solution and solid state was studied by means of crystallography, NMR spectroscopy and microcalorimetry. The results indicate that the bezoic acid groups are successively penetrated intermolecularly into the adjacent β-CD cavities to form helical columnar supramolecules in the solid state. As compared with crystal, the similar self-assembly behavior of 1 in aqueous solution has also been confirmed by the ^1H ROESY spectroscopy. Thermodynamically, the formation of polymeric supramolecules by modified CD in aqueous solution is mainly driven by entropy changes. 相似文献
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Di-Ab-An体系远离平衡枝状形貌的演化及枝体结晶学各向异性特征研究 总被引:2,自引:2,他引:0
对钠长石(Ab)-钙长石(An)-透辉石(Di)三元体系跨相界线的不同成分点在不同的降温速度条件下快速结晶形成的枝状形貌进行了研究.透辉石为枝晶,斜长石为球粒晶.当降温速度慢于1℃/min后,枝状形貌变为板-柱状形貌(即近平衡形貌).我们的实验结果中没有观察到如E.Brener 和H.Muller等人提出的形貌演化图一样的演化规律.当成分点靠近同结线后,出现两晶共结形成的"中空结构".通过光学显微镜下测试其光学性质发现,透辉石沿c轴方向延长,斜长石沿a轴延长,与晶体结构中的强键链方向一致,即快速结晶时晶体沿着结构中负离子配位多面体共角顶、共棱形成的强键链方向生长形成枝体. 相似文献