不同形态Cu2O枝晶的可控制备及形成机理

以酒石酸、铜盐以及碱为主要原料,在水热条件下通过控制相关的实验参数,制备了一系列不同形态的Cu2O晶体和枝晶.采用XRD、SEM等手段对不同形态的Cu2O晶体进行了表征,初步探讨了不同形态的Cu2O晶体和枝晶的成因.结果表明,晶体生长条件的改变主要是通过影响晶体的生长过程而影响晶体颗粒的大小及具体形貌.在低温(110 ℃)、高过饱和的碱性溶液中,所得Cu2O为形态稍有差异的粒状晶体;在高温(150℃)、较弱的碱性溶液中,只需较短的时间就可以获得三维十字枝状Cu2O晶体.     

利用辐射加热炉进行蓝宝石及其它高温氧化物的热物理和光学性能的研究

本文描述了一种特大的实验装置-辐射加热炉,获得了蓝宝石和其它高温氧化物在固相、液相时的光学、热学和物理性能.该装置和相应的技术使得在高于3500K温度下研究这些材料的粘度、熔点、热导率、发射率和吸收系数成为可能,并以此得到了高温下蓝宝石的分子热传导系数,以及不同降温速率下蓝宝石的过冷情况.此外,介绍了一种复合氧化物材料MgO-Al2O3-HfO在宽波段范围内的反射率.本文所给出的数据对于从事晶体和高温陶瓷方面研究的专家学者将很有用处.     

典型非线性光学晶体生长方法综述

非线性光学晶体具有多种生长方法,每种方法都有其独特的优势和适用的晶体,通过了解典型非线性光学晶体生长方法的特点,可以确定采用哪种方法获得高质量的晶体,达到预期的目的.本文主要对典型非线性光学晶体生长方法进行相关介绍,如水热法生长KTP晶体、水溶液法生长KDP晶体、有机溶液法生长DAST晶体、高温溶液法生长BBO、LBO、KBBF等晶体、泡生法生长CBO晶体、提拉法生长LiNbO3晶体、布里奇曼法生长CdSiP2、ZnGeP2、BaGa4 Se7等晶体,阐述典型非线性光学晶体的原料、溶液配制、温度压力的控制等实验制备条件,展示所生长出的晶体样品.通过对上述方法总结,为今后的晶体生长方法选取提供借鉴.     

退火温度对Ce:YAlO3单晶体的影响研究

将生长完成的Ce:YAlO2单晶体在1680℃的高温氢气气氛下退火,晶体颜色、吸收光谱和荧光光谱相对于未退火的样品均发生了变化.本文对此现象进行了分析.研究结果表明,1680℃高温氢气退火后,Ce:YAP晶体中同时包含YAP相和YAG相.     

Ca2+掺杂γ-La2S3多晶的制备

本文以气固反应硫化得到的γ-La2S3粉体为原料,采用热压烧结的方法制备出了γ-La2S3多晶体片.研究了不同Ca2+掺杂量对得到粉体相结构的影响,并分析了烧结温度、保温时间对多晶体γ-La2S3红外透过率的影响.结果表明:掺入碱土金属离子Ca2+有利于低温获得稳定的高温型γ-La2S3相,在Ca/La物质的量比为1:5～1:15时能得到纯相的γ-La2S3粉体.在烧结温度为1100 ℃,保温时间为1 h时制备出的γ-La2S3多晶体片,晶粒细小均匀,无明显气孔,在10～14 μm波段的最大红外透过率约为40;.     

倍半氧化物晶体及其1～3μm波段激光性能研究进展

倍半氧化物具有优异的热学性能、稳定的物化性能、低的最大声子能量和强的晶体场，是理想的高功率、大能量激光基质材料。倍半氧化物具有超高熔点，因此其高质量、大尺寸的晶体制备极其困难，研究人员对此进行了长期的研究探索。近年激光技术发展对高品质倍半氧化物单晶的迫切需求促使相关晶体的生长技术取得了突破。本文在简单介绍倍半氧化物性能与结构的基础上，详细综述了Lu₂O₃、Sc₂O₃、Y₂O₃倍半氧化物晶体的生长方法及缺陷种类，系统总结了稀土离子掺杂的倍半氧化物在1～3μm波段内的激光性能，最后对其未来的研究与发展方向进行了展望。     

新型非线性光学晶体BaAlBO3F2的生长及组分挥发的研究

采用高温熔液法生长BaAlBO3F2晶体(简称BABF)时,组分挥发严重.本文分析了晶体生长前后的组分中相关元素的重量损失,发现易挥发的物质可能是硼的氧化物和氟化物;X射线衍射分析确定挥发物中还含有少量的NaCl.通过改变助熔剂与熔质的配比,明显降低了晶体的生长温度,减少了组分挥发,优化了晶体生长条件,得到24mm×20mm×6mm尺寸的晶体.     

新型弛豫铁电晶体PIN-PT的单晶生长与性能表征

按照0.65Pb(In1/2Nb1/2)03-0.35PbTiO3的计量组成,应用高温固相分步合成方法制备出钙钛矿相PIN-PT多晶料,采用熔体坩埚下降法生长出尺寸φ20 mm × 50 mm的PIN-PT晶体毛坯.采用XRD、DTA/TG对PIN-PT晶体的结晶物相与热学性能进行了分析表征,测试了(111)取向PIN-PT晶片样品的介电温谱、压电常数和电滞回线.结果表明所生长晶体毛坯呈现具有显著特征的结晶相分布,即晶体毛坯中间部分为钙钛矿相而外围部分出现焦绿石相,且钙钛矿相晶体呈现沿晶体毛坯轴向逐渐发育生长趋势;取自晶体毛坯中上部的晶片基本为四方相,其(111)取向晶片的压电常数d33 ～415 pC/N,机电耦合系数k33～37.5;,室温介电常数ε～3095,介电损耗ta硒～1.0;,居里温度达266℃,矫顽电场Ee～11.04 kV/cm,剩余极化Pr～ 21.07 μC/cm2.     

新型非线性光学晶体BaAIBO3F2的生长及组分挥发的研究

采用高温熔液法生长BaAlBO3F2晶体(简称BABF)时,组分挥发严重.本文分析了晶体生长前后的组分中相关元素的重量损失,发现易挥发的物质可能是硼的氧化物和氟化物;X射线衍射分析确定挥发物中还含有少量的NaCl.通过改变助熔剂与熔质的配比,明显降低了晶体的生长温度,减少了组分挥发,优化了晶体生长条件,得到24mm×20mm×6mm尺寸的晶体.     

斜方晶系α-磷酸三钙晶体的制备及应用

磷酸三钙晶体是磷酸钙生物骨水泥原料的一种,由于它简便易得而得到广泛的研究和应用。将磷酸盐或磷酸盐与碳酸钙的混合粉体在1200～1400℃下煅烧,然后急冷获得单斜α相磷酸三钙晶体,磨细后即可为磷酸三钙骨水泥,虽然比较容易制备,但力学性能很低。本文所制备的磷酸三钙晶体与以往不同,而是通过添加少量的添加剂,制得以斜方α相磷酸三钙晶体为主要成份的固相反应产物,经磨细后与磷酸氢钙以一定的比例混合,得到新型高温型磷酸三钙生物骨水泥。用蒸馏水调和后置于温度为37℃,湿度为100％的条件下,24h后获得的固化体的抗折强度为9．31MPa,同样水化条件下常用的低温单斜a磷酸三钙骨水泥的抗折强度为5．81MPa,强度提高60％。通过x射线衍射对高温固相反应产物、水化产物的组成进行了分析,并用扫描电镜对两种骨水泥水化体的内部结构进行了对比观察。     

Relationship of Morphological Types of Dynamic Forms of Crystals

Crystallography Reports - The relationship of morphological spectra (sets of data on the morphological types of real polyhedral crystals and their probabilities under current physicochemical...     

A review of measurement of thermophysical properties of silicon melt

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.     

Generation of crystal structures of heteromolecular compounds by the method of discrete modeling of packings

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.     

Development of Pauling's concepts of geometric characteristics of atoms

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.     

Investigation of the Mechanism of Influence of Stress Corrosion on the Development of Macroplastic Instabilities of Aluminum–Magnesium Alloy

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...     

Comparative analysis of two methods of calculation of the orientation of domain walls in ferroelastics

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.     

Dependence of the parameters of equations of viscous flow on chemical composition of silicate melts

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 x_i 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 T_r , at which viscosity is η_r = 10¹³ [dPa.s]. Therefore, additional parameter, “lubricant fraction” l, is introduced. For each of the components, l_i is a product of molar part x_i and a specific dimensionless coefficient 0 ≤ k_i ≤ 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 T_r,SiO2 of pure SiO₂.     

A SAXS study of kinetics of aggregation of silica sols

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.     

Study of the possibility of interactive control of the surface profile of X-ray optical elements

We investigate the possibility of controlling the curvature parameters of parabolic mirrors that are modular elements of two types consisting of a base and thin inserts placed at the opposite side of the work surface. In the first type of modular elements, bending is controlled by the difference in the coefficients of the thermal expansion of the base and inserts. In the second type of elements, the profile is changed by the piezoelectric straining of the inserts under an electric field. A correlation is established between the parameters of modular elements and their surface curvature profile.