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以CaCO3和CaHPO4·2H2O为前驱体,采用水热法制备了羟基磷灰石(HAP)晶体,利用X射线衍射(XRD)、扫描电镜(SEM)及X射线能谱分析仪(EDS)系统研究了pH值、水热温度、反应时间、Ca2+浓度等条件对合成HAP晶体微结构及晶体生长的影响,同时对其生长机理进行了探讨.结果表明:随着水热合成温度的升高、时间的延长、Ca2浓度的增加,晶体发育越完整,HAP晶体的长径比呈增大趋势;体系的pH值对HAP晶体的生长有较大的影响,随着pH值的增加HAP晶粒的大小、长径比减小趋势明显;在水热温度为200℃,pH值=10,时间8h的条件下,可得到结晶度高、晶形完整清晰,端面尺寸在50~ 70 nm,生长极性明显的六方柱状的一维n-HAP晶体.EDS分析结果证实合成的HAP平均钙磷比约为1.70左右,同理论值比较相符.点分析研究表明晶体端面的钙磷比比平均的略高,钙磷比约为1.75,从而证明了Ca2+的浓度直接影响着HAP晶体的极性生长. 相似文献
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采用扫描电子显微镜(SEM)和X射线衍射(XRD)方法,比较研究了防石药物柠檬酸钾(K3cit)在尿石患者尿液和正常人尿液制备的凝胶中对草酸钙(CaOxa)晶体生长的影响.没有加入K3cit时,CaOxa晶体均以一水草酸钙(COM)为主要晶相,加入K3cit后,不但COM晶体变得圆钝,比表面积减小,而且诱导了二水草酸钙(COD)生成.随着K3cit浓度从0.10增加到0.20 mol/L,在正常人尿液凝胶中COD晶体的百分含量从20;增加到45;,而在CaOxa结石患者尿液凝胶中,不但COD含量从10;增加到25;,而且K3cit可诱导草酸钙成核,从而产生大量的小尺寸草酸钙晶体,这有利于阻止草酸钙晶体变大形成尿石.本结果可为临床上治疗CaOxa结石提供启示. 相似文献
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本文采用水热法,以3mol/L KOH为矿化剂,填充度35%,温度430℃,通过添加适量比例的MgCl2.7H2O和CaO,合成了非极性生长的ZnO晶体。当Mg2 :Zn2 =2%和Ca2 :Zn2 =2~3%时,晶体c轴方向生长速度明显减弱,{0001}方向的极性生长得到控制,所合成的晶体大面积显露正极面 c{0001},同时显露负极面-c{1001-}、正锥面 p{101-1}、负锥面-p{101-1-}和柱面m{101-0}。X光能谱(EDS)没有检测到晶体中含有碱土金属离子。 相似文献
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在LiNbO3晶体中掺进0.1wt?O2和0.03wt?2O3以Czochralski技术生长不同Li/Nb比(0.94、1.20、1.40)Ce:Fe:LiNbO3晶体,其中Li/Nb=1.40的Ce:Fe:LiNbO3晶体是化学计量比.测试了不同Li/Nb比Ce:Fe:LiNbO3晶体抗光损伤能力,得到随着Li/Nb比的增加,晶体的抗光损伤能力增加.研究了晶体抗光损伤能力增强的机理.随着Li/Nb比的增加,晶体的响应速度和光折变灵敏度增加.测试不同Li/Nb比Ce:Fe:LiNbO3晶体位相共轭效应,利用产生的位相共轭光波消除图像的位相共轭畸变.利用Li/Nb=1.40的Ce:Fe:LiNbO3晶体做记录介质,Li/Nb=1.20的Ce:Fe:LiNbO3晶体作位相共轭镜进行全息关联存储实验.实验结果表明,存储系统具有实时处理,成像质量好,信噪比高和可反复使用的优点. 相似文献
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Crystallography Reports - The relationship of morphological spectra (sets of data on the morphological types of real polyhedral crystals and their probabilities under current physicochemical... 相似文献
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S. S. Batsanov 《Crystallography Reports》2001,46(6):891-897
The evolution of the geometric characteristics introduced by Pauling and their dependence on the specific features of the structure and chemical bonds have been considered. The values of the covalent and van der Waals radii are given as well as their relationships and mutual transitions. 相似文献
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Measurements of thermophysical properties of Si melt and supplementary study of X-ray scattering/diffraction by the authors' group were reviewed. The values obtained differed variously from those of literature. Density was 2–3% larger, surface tension 20–30% smaller, viscosity up to 40% larger, electrical conductivity 8% smaller, spectral emissivity more or less in good agreement with literature values, and thermal diffusivity a few percent larger. An anomalous density jump was found near the melting point. Surface tension and viscosity also showed anomaly. A strange time-dependent change of density was observed over 3 h after melting. X-ray analyses suggested a slight change in local atom ordering, but showed no sign of cluster formation. An addition of 0.1 at% gallium caused the density jump to disappear, while that of boron caused no change. An EXAFS study of the former melt indicated a strong interaction between Ga and Si atoms as if molecules of GaSi3 existed. The implications of the measured properties are a possibility of soft-turbulence in an Si melt in a relatively large crucible, a more complicated manner of intake of oxygen depleted molten Si from the free surface region to underneath the growing crystal, and a relaxation of the melt after melting arising from trapped gas species. 相似文献
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Within the method of discrete modeling of packings, an algorithm of generation of possible crystal structures of heteromolecular compounds containing two or three molecules in the primitive unit cell, one of which has an arbitrary shape and the other (two others) has a shape close to spherical, is proposed. On the basis of this algorithm, a software package for personal computers is developed. This package has been approved for a number of compounds, investigated previously by X-ray diffraction analysis. The results of generation of structures of five compounds—four organic salts (with one or two spherical anions) and one solvate—are represented. 相似文献
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Shibkov A. A. Kochegarov S. S. Denisov A. A. Zolotov A. E. Gasanov M. F. Shuklinov A. V. 《Crystallography Reports》2022,67(2):156-165
Crystallography Reports - Macroscopic jumps of plastic deformation (few percent in amplitude) on creep curves of aluminum–magnesium alloy, caused by a local effect of concentrated solution of... 相似文献
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I. Avramov 《Journal of Non》2011,357(22-23):3841-3846
The temperature dependence of viscosity of silicate melts is discussed in the framework of the Avramov–Milchev (AM) equation. The composition is described by means of two parameters: the molar fraction, x, and the “lubricant fraction”, l. The molar fraction is the sum of the molar parts xi of all oxides dissolved in SiO2, the molar fraction of the latter being 1 ? x. It is shown that, with sufficient precision, two of the parameters of the AM equation can be presented as unique functions of the molar fraction. On the other hand, x is not sufficient to determine properly the reference temperature Tr , at which viscosity is ηr = 1013 [dPa.s]. Therefore, additional parameter, “lubricant fraction” l, is introduced. For each of the components, li is a product of molar part xi and a specific dimensionless coefficient 0 ≤ ki ≤ 1 accounting for the specific contribution of this component to the increased mobility of the system. It is demonstrated that, for l > 0, the reference temperature is related to the “lubricant fraction” l through the reference temperature Tr,SiO2 of pure SiO2. 相似文献
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V. A. Nepochatenko 《Crystallography Reports》2004,49(5):828-831
Two types of domain-wall equations are analyzed: the equations derived by the Sapriel method and the equations obtained by interface matching of the thermal-expansion tensor. It is shown that, for W-type domain walls, these methods yield the same equations. For W′-type domain walls, the equations obtained by different methods coincide for proper ferroelastics and differ for improper ferroelastics. 相似文献
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Crystal chemical characteristics of the α and β modifications of Zn2V2O7 are calculated based on in situ high-temperature X-ray measurements. The expansion of the structure is found to be strongly anisotropic up to the negative volumetric thermal expansion of the α-Zn2V2O7 unit cell in the temperature range of 300–600°С, α V =–17.94 × 10–6 1/K. The transformations of the “hard” and “soft” sublattices with an increase temperature and at the phase transition are considered in detail. It is shown that the negative volumetric thermal expansion of α-Zn2V2O7 is due to the degeneracy of the zigzag-like shape of zinc–oxygen columns at constant distances between their vertices. 相似文献
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SAXS in situ experiments on the evolution of TMOS solutions during hydrolysis and polycondensation lead to power laws with scaling exponents ≈ 2. It is suggested that this could be the result of the polydispersity of the samples and that only an apparent fractal dimension can be obtained in this way. Kinetic studies tend to indicate that agglomeration in the sol is the result of a diffusion-controlled process. 相似文献