硫酸盐类晶体中[SO_4]~(2-)四面体的结晶方位与晶体的形貌

本文从硫酸盐类晶体中负离子配位多面体的结晶方位和相互联结的稳定性出发，探讨了硫酸盐类晶体中[SO4]2-结晶方位与晶体结晶形貌之间的关系;认为[SO4]2-四面体与金属阳离子（Ba2 、Ca2 、Mg2 …）结合时，由于晶体结构和生长条件（如温度、过饱和度等）的不同，在晶体各族晶面上的叠合速率和取向不同;晶体的结晶形貌迥然有别.晶体的结晶形貌与[SO4]2-四面体在晶体中的结晶方位密切相关，四面体的面和棱的法线（L2）所对向的晶面，生长速率慢，顽强显露，均属晶体的板面;四面体的顶角所指向的晶面，生长速率快，显露面积小，经常消失.     

若干晶体中氧八面体结晶方位与晶体形貌

本文从结晶化学角度出发，研究了ＡＢ和Ａ２Ｂ３和ＡＢＯ３型氧化物晶体中的氧配位八面体的结晶方位与晶体结晶形貌之间的关系，提出晶体的结晶形貌是受晶体中负离子配位多面体结构和结晶方位所制约的。配位多面体顶角所对向的晶面生长速率最快，而面所对向的晶面生长速率最慢，配位体的棱所对向的晶面，生长速率居于两者之间，负离子配位多面体在晶体中的各个面族上连接和稳定性，决定了晶面的显露程度和晶体的结晶形貌。     

硫酸盐类晶体中[SO4]2-四面体的结晶方位与晶体的形貌

本文从硫酸盐类晶体中负离子配位多面体的结和相互联结的稳定性出发，探讨了硫酸在晶体中「ＳＯ４」＾２－结晶方位与晶体结晶形貌之间的关系；认为「ＳＯ４」＾２－四面体与金属阳离子结合时，由于晶体结构和生长条件（如温度、过饱和度等）的不同，在晶体各族晶面上的叠合速率和取向不同，晶体的结晶形貌迥然有别。晶体的结晶形貌与「ＳＯ４」＾２－四面体在晶体中的结晶方位一密切相关，四面体的面和棱的法线（Ｌ＾２）所对向的对     

磷酸盐晶体中络阴离子结晶方位与晶体形态

研究了磷酸盐类晶体中的络阴离子[PO4]-和[CaP6O24]16-在晶体中的结晶方位,与[ClCa6]11 八面体相互联结的稳定性决定了各个面族的生长速率.根据磷灰石各族晶面显露的习性,提出了采用人工生长的磷灰石做人工关节时,应该注意磷灰石的取向问题．平行于C轴方向生长的磷灰石有利于与人体骨骼的快速愈合．     

若干晶体结晶习性的形成机理

本文根据在热液条件下生长水晶和钛酸钠晶体的电泳实验，提出热液条件下，上述晶体的生长基元具有负离子配位多面体的结构形式。由于溶液过饱和度在变化，这些生长基元的维度也随之变化。不同维度的生长基元往晶体各族晶面上叠合速率的比例也发生相应改变。它直接反映在晶体结晶形貌上。本文根据不同维度生长基元在各族晶面上的叠合速率解释了水晶和钛酸钠的结晶习性形成机理。     

稀土掺杂复式钨酸盐纳米晶体的制备及发光性能

应用水热合成技术制备了稀土掺杂复式钨酸盐NaRe（WO4）2（Re=La,Y,Gd）纳米晶体,水热合成温度随Re^3＋种类的不同而呈现较大的差异.稀土离子在NaRe（WO4）2纳米晶体中处于非反演对称中心位置.在980nm红外光激发下,Yb^3＋和Er^3＋共掺的NaRe（WO4）2纳米晶体可产生明显的绿色上转换发光,发光机理为双光子过程.     

TeO2晶体位错腐蚀形貌与晶体对称性

用化学腐蚀的方法研究TeO2晶体(110)面和(001)面位错蚀坑的形貌，结合晶面极图，并运用对称群理论进行分析论证，理论分析与实验结果相一致．实验结果同时显示，TeO2晶体位错腐蚀坑面由{110}面族构成，即{110}面族是晶体的习性面．     

钨酸铅晶体的生长及其闪烁性的研究

采用提拉法生长出直径 2 0 -2 5mm,长 2 5-3 0 mm优质 Pb WO4及 La3 +、Mg2 +、Mo6+和 Bi3 +掺杂 Pb WO4晶体。测试了晶体的 X射线衍射谱、透射光谱、激发发射光谱、光产额、抗辐照性能和发光衰减时间。总结并解释了掺杂对 Pb WO4晶体性能的影响以及氧退火对晶体抗辐照性能的影响 ,探讨了掺杂改善晶体闪烁性能的可能性。     

非完整形态KH2PO4晶体薄表面层生长特性

实时观察了非完整形态的KH2PO4 (KDP)晶体在过饱和溶液中以薄表面层生长形式恢复其结晶学形态的过程.提出了晶体形态恢复的“最小多面体原理”,即:在自由生长系统中,对于非完整形态的KDP晶体,当其以薄表面层形式恢复其结晶学完整形态时,薄表面层将选择相应的奇异面方向生长,使晶体形态最终恢复为一个由各结晶学显露面所围成的体积最小的凸多面体.利用PBC理论分析了生长基元在非结晶学显露面上的附着情况并阐述了锥顶处薄表面层倒垂生长的原因.结果表明,薄表面层形成与晶体非完整结晶学形态及不均匀水动力学条件相关联.柱面凹角与非正常棱边及Z切片正常棱角均可诱发产生薄表面层,且薄表面层生长终止于其所在奇异面的正常结晶学晶棱.     

非完整形态KH2PO4晶体薄表面层生长特性

实时观察了非完整形态的KH_2PO_4(KDP)晶体在过饱和溶液中以薄表面层生长形式恢复其结晶学形态的过程。提出了晶体形态恢复的"最小多面体原理",即:在自由生长系统中,对于非完整形态的KDP晶体,当其以薄表面层形式恢复其结晶学完整形态时,薄表面层将选择相应的奇异面方向生长,使晶体形态最终恢复为一个由各结晶学显露面所围成的体积最小的凸多面体。利用PBC理论分析了生长基元在非结晶学显露面上的附着情况并阐述了锥顶处薄表面层倒垂生长的原因。结果表明,薄表面层形成与晶体非完整结晶学形态及不均匀水动力学条件相关联。柱面凹角与非正常棱边及Z切片正常棱角均可诱发产生薄表面层,且薄表面层生长终止于其所在奇异面的正常结晶学晶棱。     

Elucidating the role of charge density on the growth of CaCO3 crystals underneath Calix[4]arene monolayers

The amphiphilic 5,11,17,23-tetrakis-(1,1,3,3-tetramethylbutyl)-25,26,27,28-tetra(2-hydroxyethoxy)calix[4]arene (1) forms stable monolayers at the air–water interface. The growth of CaCO₃ crystals underneath monolayers of 1 is strongly inhibited, in contrast to the corresponding carboxylic acid derivative 5,11,17,23-tetrakis-(1,1,3,3-tetramethylbutyl)-25,26,27,28-tetra(carboxymethoxy)calix[4]arene (2), the monolayers of which lead to growth of preferentially oriented calcite single crystals. The growth morphology of CaCO₃ crystals is correlated with the phase behaviour and surface potential of the monolayers. The investigations demonstrate that the average charge density is the dominant factor for heterogeneous nucleation of CaCO₃ crystals at the calixarene monolayer/solution interface.     

Self-assembled peanut-like Ln3+ (Ln = Tb, Sm, Eu) doped NaLa(WO4)2: phase control and its relevance to luminescence modification

Ln3+ (Ln = Tb, Sm, Eu) doped NaLa(WO4)2 peanuts were successfully self-assembled by a facile EDTA assisted hydrothermal treatment. EDTA played critical roles in the phase and morphology control, which regulated the phase transformation from monoclinic La2(WO4)3 flowers to tetrahedral NaLa(WO4)2 peanuts. La2(WO4)3:Tb3+ exhibited two broad excitation bands at 280 and 340 nm, which are related to the normal and perturb sites of WO4(2-). However, the excitation band for NaLa(WO4)2:Tb3+ shifted to near ultraviolet region and showed only one broad excitation band originating from perturb sites. Under ultraviolet excitation, La2(WO4)3:Tb3+ displayed green light and NaLa(WO4)2:Tb3+ showed blue-green light consisting of WO4(2-) self-activated blue emission and the characteristic Tb3+ emission. It can be clearly seen that the blue emission of WO4(2-) was not sufficiently quenched in NaLa(WO4)2 as that in La2(WO4)3, because the distortions of crystalline lattice for NaLa(WO4)2 may alter the energy migration processes. When doping with Sm3+ and Eu3+, NaLa(WO4)2 peanuts exhibited white color emission which may find practical applications in solid state lighting devices.     

Indentation creep surface morphology of nickel-based single crystal superalloys

The crystallographic orientation dependence of surface morphology of indentation creep on a nickel-based single crystal superalloy is investigated by using crystal plasticity slip theory with a three-dimensional (3D) finite element model. The numerical results show that the pile-up patterns developed around the indentation imprint exhibit four-, two-, and threefold symmetry on the surfaces of [0 0 1]-, [0 1 1]-, and [1 1 1]-oriented single crystals, respectively. The evolution of radial and hoop stresses around the crater provides important information for possible radial crack nucleation, whose critical locations depend on crystallographic orientations. These characteristics can be well explained in the viewpoint of crystallographic anisotropy. The findings may shed some light on understanding of the crystal structures and its time-dependent deformation mechanisms with the indentation method.     

Size- and shape-controlled conversion of tungstate-based inorganic-organic hybrid belts to WO3 nanoplates with high specific surface areas

Two-dimensional monoclinic WO(3) nanoplates with high specific surface areas are synthesized through a novel conversion process using tungstate-based inorganic-organic hybrid micro/nanobelts as precursors. The process developed involves a topochemical transformation of tungstate-based inorganic-organic hybrid belts into WO(3) nanoplates via an intermediate product of H(2)WO(4) nanoplates, utilizing the similarity of the W-O octahedral layers in both H(2)WO(4) and WO(3). The as-obtained WO(3) nanoplates show a single-crystalline nanostructure with the smallest side along the [001] direction. The WO(3) nanoplates are 200-500 nm x 200-500 nm x 10-30 nm in size, and their specific surface areas are up to 180 m(2) g(-1). Photocatalytic measurements of visible-light-driven oxidation of water for O(2) generation in the presence of Ag(+) ions indicate that the activity of the as-obtained WO(3) nanoplates is one order of magnitude higher than that of commercially available WO(3) powders.     

The morphology-dependent photocatalysis for rhodamine B degradation over Bi2WO6 hierarchical nanostructure

In this paper, the nanostructured Bi2WO6 with different hierarchical morphologies was synthesized via a warmly hydrothermal route. The structure and morphology of the as-prepared Bi2WO6 products were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), UV-vis absorption spectroscopy (UV-Vis) and N2-sorption analysis. The photocatalytic efficiency of Bi2WO6 was investigated by photodegradation of rhodamine B (RhB) under visible-light irradiation. The present work demonstrated that Bi2WO6 with four different hierarchical structures was effective visible-light-driven photocatalytic functional material for environmental purification. Moreover, the nest-like Bi2WO6 exhibited superior photocatalytic effects on rhodamine B degradation compared with other three Bi2WO6 morphologies. The excellent catalytic effect of the nest-like Bi2WO6 was attributed to its unique structural property and large surface area. The relationship between morphology and photocatalytic performance was discussed in detail. The photocatalytic mechanism for the degradation of RhB was also investigated, which revealed the important role of morphology in improving the photocatalyitc activities of Bi2WO6.     

Morphological aspects of some symmetrical ammonium hydrogen tartrate crystals grown by silica gel technique

Ammonium hydrogen tartrate single crystals have been prepared by the reaction of NH₄Cl and tartaric acid in silica gel. The morphology of some as-grown symmetrical crystals has been studied by optical microscopy. The growth morphology studies indicate that the grown crystals are needle-shaped, orthorhombic disphenoidal and tetrahedral disphenoidal. The growth mechanism has been assessed.     

Czochralski single crystal growth of Sr.61Ba.39Nb2O6 for surface acoustic wave applications

Ferroelectric Sr_.61Ba_.39Nb₂O₆ (SBN) single crystals approximately 2 cm. in diameter and 5–6 cm. long have successfully been grown by the Czochralski technique. All the crystals were grown in the [001] direction in argon or oxygen, and it was found that the degree of difficulty of growth increased as the diameter of the crystals increased. Temperature dependence measurements on the poled Z-cut SBN crystals showed that this composition has temperature compensated orientations which make this material useful for surface acoustic wave devices.