PbI2—PbBr2二组份玻璃的化学稳定性研究

本文获得了ＰｂＩ２－ＰｂＢｒ２二组份玻璃，并且在２５℃的恒定温度下，研究了组成为７０ＰｂＩ２３０ＰｂＢｒ２（ｍｏｌ％）的玻璃在静态去离子中的侵蚀过程，在去离子水中，玻璃中的各组份以分子形式溶解，这是一个选择性溶解过程。，溶解度较高的玻璃组份将优先溶解。由于ＰｂＸ２（Ｘ＝Ｉ，Ｂｒ）的水解，溶液的ＰＨ经历一个由快速下降到逐渐稳定的变化过程，通过比较发现，所得玻璃的化学稳定性与氟锆酸盐玻璃处于同一数量级     

PbX2（X：I,Br,Cl）基非氟卤化物玻璃的形成行为

为了获得具有实用意义的非氟卤化物玻璃，有必要探索新的玻璃形成系统，本文获得了 新的Ｃ ＰｂＸ２（Ｘ：Ｉ，Ｂｒ，Ｃｌ）为基质的三元非氟卤化物玻璃形成系统，并且首次发现ＰｂＩ２可以单独形成玻璃，所得的三元玻璃形成系统均表现出了良好的玻璃形成能力，此外，还从晶体结构，化学键的特怀，离了半径应电负性等角度探讨了各卤化物在玻璃形成过程中所坊的作用，结果表明，这些因素对玻璃形成均具有重要的作用。     

PbI2-PbCl2-KCl系统玻璃的形成及其析晶行为研究

本文从阳离子的配位数、化学键的特性等角度出发，探讨了ＰｂＩ２－ＰｂＣｌ２－ＫＣｌ三元系统的玻璃形成特性，并以ＤＳＣ、ＳＥＭ和ＸＲＤ等为手段研究了组成为５０ＰｂＩ２３０ＰｂＫＣｌ（ｍｏｌ％）的玻璃的析晶行为。析晶学研究表明，所得玻璃的高、３氏温相变机量彼此不同，所得玻璃的析经能接近于较稳定的氟锆酸盐玻璃，因此在析晶温度睛表现出了较慢的析晶速率，通过适当的热处理，可以工餐透过与原始玻璃一致的微晶玻璃，     

熔化过程中PbO-PbBr2-PbF2-P2O5系统玻璃成分的变化

为了研究ＰｂＯ－ＰｂＢｒ２－ＰｂＦ２－Ｐ２Ｏ５系统玻璃在熔化过程中成分的变化,本文应用定量化学分析法测出了玻璃在熔化后的成分,结果表明,ＰｂＯ－ＰｂＢｒ２－ＰｂＦ２－Ｐ２Ｏ５系统玻璃熔化时氟和磷的损失较大,铅的损失相对较小,溴的损失随配料中各元素呈的多少而变化,氧含量的受Ｐ２Ｏ４的挥发以及氧,水分与玻璃熔体中卤化物的反应程度两个因素影响,相关化学反应的热力学计算与分析结果相吻合。     

PbBr2-PbCl2-PbF2-PbO-P2O5系统玻璃的热性质和化学稳定性

重点研究了ＰｂＢｒ_２－ＰｂＣｌ_２－ＰｂＦ_２－ＰｂＯ－Ｐ_２Ｏ_５系统玻璃的热性质、耐水性和抗潮解性．结果表明：该系统玻璃的热膨胀系数较大,一般在 ２５×１０^－６°Ｃ^－１左右． ＰｂＢｒ_２－ＰｂＣｌ_２－Ｐ_２Ｏ_５系统的玻璃具有较低的玻璃转变温度,可低达 １４６℃．加入 ＰｂF_２和／或 ＰｂＯ可显著提高玻璃的转变温度和密度,其中 ＰｂＯ对试样的影响更为显著． ＰｂＢｒ_２－ＰｂＣｌ_２－ＰｂＦ_２－ＰｂＯ－Ｐ_２Ｏ_５系统玻璃的抗潮解性一般较好。多数玻璃在水中的溶解速率可达１０^－５ｍｍ／ｄａｙ,具有较好的耐水性．     

熔化过程中PbO-PbBr2-PbF2-P2O5系统玻璃成分的变化

了研究ＰｂＯ－ＰｂＢｒ_２－ＰｂＦ_２－Ｐ_２Ｏ_５系统玻璃在熔化过程中成分的变化,本文应用定 量化学分析法测出了玻璃在熔化后的成分．结果表明,ＰｂＯ－ＰｂＢｒ_２－ＰｂＦ_２－Ｐ_２Ｏ_５系统玻璃熔化 时氟和磷的损失较大,铅的损失相对较小;溴的损失随配料中各元素含量的多少而变化．氧含 量的变化受Ｐ_２Ｏ_５的挥发以及氧、水分与玻璃熔体中卤化物的反应程度两个因素影响．相关化 学反应的热力学计算与分析结果相吻合．     

PbO-PbBr2-PbF2-P2O5系统玻璃的性质

对新研制的ＰｂＯ－ＰｂＢｒ２－ＰｂＦ２－Ｐ２Ｏ５系铅卤磷权盐玻璃的化学成分以及玻璃转变温度、密度、抗潮解性和紫外光谱等性质进行了分析。结果表明,ＰｂＯ－ＰｂＢｒ２－ＰｂＦ２－Ｐ２Ｏ５系铅卤磷酸盐玻璃具有较低的玻璃转变温度,转好的抗潮解性,密度在５．０ｇ．ｃｍ＾－３以上,并且在可见了光区域具有较好的透光经。     

Bi_2O_3－PbO二元系相图

本文用差热分析（ＤＴＡ）和Ｘ射线衍射（ＸＲＤ）技术研究了Ｂｉ_２Ｏ_３－ＰｂＯ二元系相平衡．在该二元系中存在一个结构为体心立方，点阵常数ａ＝０．４３５０ｎｍ的新化合物，化合物的组成为２Ｂｉ_２Ｏ_３．３ＰｂＯ．该化合物是６Ｂｉ_２Ｏ_３·ＰｂＯ和α固溶体在５９０℃包晶反应形成的．温度为６１５℃，组成为Ｂｉ_２Ｏ_３：ＰｂＯ＝３：７发生共晶反应Ｌ６Ｂｉ_２Ｏ_３．ＰｂＯ＋α６１５℃时Ｂｉ_２Ｏ_３在。相中的最大固溶度大约是１０ｍｏｌ％．温度为７０２℃，Ｂｉ_２Ｏ_３：ＰｂＯ＝１９：１存在共析反应Ｃ_ｓｓβ＋６Ｂｉ_２Ｏ_３．ＰｂＯ高温型），６Ｂｉ_２Ｏ_３．ＰｂＯ高温型）的分解温度为７２０℃．     

溶胶－凝胶法制备Pb（Zr，Ti）O_3玻璃陶瓷过程中的结构变化

本文介绍溶胶－凝胶法制备均匀ＰｂＺｒ－Ｔｉ－Ｂ－Ｓｉ凝胶玻璃，并通过适当热处理在凝胶玻璃中原位生长Ｐｂ（Ｚｒ；Ｔｉ）Ｏ３微晶的新工艺·利用ＩＲ谱考察了凝胶玻璃中的元素键合结构随温度的变化．结合热分析和ＸＲＤ；ＳＥＭ技术，研究了Ｐｂ（Ｚｒ，Ｔｉ）Ｏ３微晶在凝胶玻璃中的生长过程及该材料的结构特点．发现Ｐｂ２（Ｚｒ，Ｔｉ）２Ｏ６＋ｘ立方焦绿石介稳过渡相的纳米微晶首先出现于该体系中，并在更高的温度下先后完全转变成三方和四方Ｐｂ（Ｚｒ，Ｔｉ）Ｏ３钙钛矿相．电子显微观察结果表明，该工艺制备的Ｐｈ（Ｚｒ；Ｔｉ）Ｏ３玻璃陶瓷具有均匀的细晶结构．     

Bi2O3—PbO二元系相图

本文用差热分析（ＤＴＡ）和Ｘ射线衍射（ＸＲＤ０技术研究了Ｂｉ２Ｏ３－ＰｂＯ二元相平衡；在该二元系中存在一个结构为体心立方，点阵常数ａ＝０．４３５０ｎｍ的新化合物，化合物的组成来２Ｂｉ２Ｏ３，３ＰｂＯ，该化合物是６Ｂｉ２Ｏ３－ＰｂＯ和ａ固溶体在５９０℃包晶反庆形成的，温度为６１５℃，组成为Ｂｉ２Ｏ３：ＰｂＯ＝３：７发生共晶反应Ｌ＝６Ｂｉ２ｏ３．ＰＢＯ＋α６１５℃时Ｂｉ２Ｏ３在α相中的最大固溶度大约是     

VLE data for CO2-CF2Cl2, N2-CO2, N2-CF2Cl2 and N2-CO2-CF2Cl

Knowledge about vapour-liquid (VLE) is required as a basis of reliable calculations for separation processes. Correlations available for the prediction of T, p, x, y data are less accurate for mixtures at high pressures and mixtures containing supercritical components. The results of VLE experiments are reported and compared with data calculated with equations of state.     

Preparation of ZrO2-CeO2 and HfO2-CeO2 nanopowders

We prepared weakly agglomerated powders of ZrO₂-CeO₂ and HfO₂-CeO₂ solid solutions 5–8 nm in particle size, consisting of monoclinic and tetragonal phases. After heat treatment at 1200°C, the crystallite size was 30 and 14 nm, respectively. We also examined the effect of precipitate freeze drying on the crystallization of hafnia-based solid solutions containing up to 20 mol % CeO₂.     

Thermal diffusion in binary mixtures H2-CCl2F2 and H2-CHClF2

Thermal diffusion coefficients were measured in two gaseous mixtures, in which one component was close to the critical temperature, in the pressure range (19.6–127.4)·10⁴ N/m² and at a freon concentration of 0.25–0.8.     

Comparison of the Electronic Structures of La2CuO4, Sr2CuO2Cl2, and Sr2CuO2F2

First-principles cluster calculations are reported of the local electronic structure of the three compounds: La₂CuO₄, Sr₂CuO₂Cl₂, and Sr₂CuO₂F₂. The copper ${\text{3d}}_{x^2 - y^2 } $ and the planar oxygen 2p _σ atomic orbitals exhibit a similar degree of covalency. The out-of-plane orbitals, however, are quite different with the ${\text{3}}d_{3z^2 - r^2 } $ atomic orbital lowered significantly in energy for chlorine and fluorine apical positions.     

Radial GRIN glasses in Li2O-Na2O-Al2O3-TiO2-SiO2 systems

A series of GRIN glass rods have been developed in Li2O-Na2O-Al2O3-TiO2-SiO2 systems. Negative radial refractive index profiles were generated by exchanging Na+ for Li+ ions in these glass rods. It has been observed that TiO2 plays a vital role in increase in the profile depth and maximum change in the refractive index because of its ambivalent nature. Change in the refractive index can be further increased by increasing the concentration of exchanging cation in the base glass.     

Thermoelectric power of single-phase samples of Tl2CaBa2Cu2O y and Ba2CaSr2Cu2O y

Single-phase 2122 samples of thallium and bismuth superconductors were made by the precursor matrix method. The thermopower of these samples was measured in the temperature range 250 K-T _c . The thermopower was positive and decreased linearly with increasing temperature aboveT _c (onset). The exponential enhancement of thermopower seen in the undoped and doped YBCO was not observed in these samples. The linear variation of thermopower can be explained on the basis of either a two-band model or a narrow band model.     

Si_2N_2O-Al_2O_3-La_2O_3和Si_2N_2O-Al_2O_3-CaO系统的亚固相关系

本文给出了 Si_2N_2O-Al_2O_3-La_2O_3和 Si_2N_2O-Al_2O_3-CaO 系统的亚固相图。实验结果表明:在 Si_2N_2O-Al_2O_3-CaO 系统中有一个未知结构的新化合物 CaO·Si_2N_2O,在3CaO·Si_2N_2O 和3CaO·Al_2O_3两化合物之间形成连续立方固溶体。而 Si_2N_2O-Al_2O_3-La_2O_3系统中则没有发现新化合物。在两个系统的富 Si_2N_2O区,过量的 Si_2N_2O 与 La_2O_3和 CaO 分别反应形成 Si_3N_4与 La_(10)[SiO_4]_(?)N_2(H-相)(和 CaSiO_3。所研究的这两个三元系统中,分别形成了如下几个四元相容性区。在 Si_2N_2O-Al_2O_3-La_2O_3系统内有:H-Si_3N_4-La_2O_3·Si_2N_2O-La_2O_3·Al_2O_3;H-Si_3N_4-La_2O_3·Al_2O_3-La_2O_3·11 Al_2O_3;H-Si_3N_4-La_2O_3·11 Al_2O_3-Al_2O_3;H-Si_3N_4-Al_2O_3-O′s.s;H-Si_3N_4-O′s.s-Si_2N_2O在 Si_2N_2O-Al_2O_3-CaO 系统内有:Si_3N_4-CaSiO_3-CaO·Si_2N_2O-3CaO·Al_2O_3;Si_3N_3-CaSiO_3-3CaO·Al_2O_3-2CaO·Al_2O_3·SiO_(?);Si_(?)N_(?)-CaSiO_3-2CaO·Al_2O_3·SiO_2-Al_2O_3;Si_3N_4-CaSiO_3-Al_2O_(?)-O′s.s;Si_3N_4-CaSiO_3-O′s.s-Si_(?)N_(?)O     

Elastic and Electronic Properties of Superconducting CaPd 2 As 2 and SrPd 2 As 2 vs. Non-superconducting BaPd 2 As 2

The first-principles calculations were performed to predict the elastic and electronic properties of the superconducting ThCr₂Si₂-type phases CaPd₂As₂ and SrPd₂As₂ in comparison with the non-superconducting CeMg₂Si₂-type phase BaPd₂As₂. Besides, the same properties were compared for CeMg₂Si₂- and ThCr₂Si₂-type polymorphs of BaPd₂As₂. We found that all these phases are mechanically stable and belong to soft materials with low hardness. The near-Fermi region is formed by the valence states of the blocks [Pd₂As₂] with decisive contributions of Pd 4d states. The values of N(E _F) increase in the sequence: CaPd₂As₂ < SrPd₂As₂ < BaPd₂As₂, i.e. in the reverse sequence relative to the transition temperatures T _C. Thus, the change in T _C cannot be explained by the electronic factor, i.e. by the simple correlation T _C～N(E _F). Most likely the decrease in T _C in the sequence CaPd₂As₂ → SrPd₂As₂ and the absence of a superconducting transition in BaPd₂As₂ are related to the structural factors and the peculiarities of the electron–phonon coupling mechanism.