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1.
硫酸盐类晶体中[SO_4]~(2-)四面体的结晶方位与晶体的形貌   总被引:2,自引:0,他引:2  
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.  相似文献   

2.
若干晶体中氧八面体结晶方位与晶体形貌   总被引:1,自引:0,他引:1  
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。  相似文献   

3.
硫酸盐类晶体中[SO4]2-四面体的结晶方位与晶体的形貌   总被引:1,自引:1,他引:0  
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  相似文献   

4.
磷酸盐晶体中络阴离子结晶方位与晶体形态   总被引:1,自引:0,他引:1  
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.  相似文献   

5.
若干晶体结晶习性的形成机理   总被引:4,自引:0,他引:4  
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。  相似文献   

6.
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.  相似文献   

7.
掺Yb^3+闪烁晶体是新近发展起来的一类闪烁体,有可能用于探测太阳中微子。本文简要介绍了掺Yb^3+闪烁晶体的电荷迁移发光的机理以及基质晶体对温度猝灭与浓度猝灭的影响。综述了具有石榴石结构和钙钛矿结构的两类掺Yb^3+闪烁晶体的研究进展,特别是Yb:YAG和Yb:YAP晶体的生长、闪烁性能以及应用前景。最后,对掺Yb^3+闪烁晶体的未来研究方向做了展望。  相似文献   

8.
闪烁晶体的生长与宏观缺陷研究   总被引:1,自引:1,他引:1  
用提拉法生长了Lu2Si2O7:Ce晶体,讨论了晶体生长过程中的几个问题;(1)熔体挥发;(2)晶体开裂;(3)层状包裹.生长过程中LPS和SiO2均存在挥发,其中后者占主导;LPS挥发不会造成组分偏析,因此对生长过程没有负面的影响.接种温度偏低导致晶体出现多晶化和晶体中较大的热应力是促使开裂发生的主要原因.层状包裹现象的出现主要是由于该晶体的结晶温度范围狭窄,熔体容易出现组分过冷,以及生长设备的温控系统精度不高等造成的.  相似文献   

9.
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。  相似文献   

10.
在恒定磁场的诱导下,恒电流电沉积制备了氧化亚铜(Cu2O)晶体。X射线衍射(XRD)和X射线光电子能谱仪(XPS)的测定结果表明,电沉积制备的氧化亚铜(Cu2O)为纯净、立方晶系的Cu2O晶体;扫描电子显微镜(SEM)分析结果表明,有无磁场电沉积时,氧化亚铜均表现为多面体聚集,但电结晶行为表现不同,在磁诱导下Cu2O电结晶径向生长的速率明显优于轴向生长,并出现孔洞现象。  相似文献   

11.
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.  相似文献   

12.
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.  相似文献   

13.
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.  相似文献   

14.
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.  相似文献   

15.
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.  相似文献   

16.
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.  相似文献   

17.
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.  相似文献   

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