材料期刊网

Effect of Cristobalite and Quartz on the Properties of Gypsum Bonded Investment

Yun-Jong Kim , Sang-Bae Kim , Hyun-Hye Park , Myeong-Deok Seo , Byoung-Cheon Lee , Man-So Han , Taik-Nam Kim , Sung-Baek Cho

材料科学技术（英文）

Generally the gold investment material consists of cristobalite, quartz and plaster. The physical property of gold investment materials depends on its thermal expansion coefficients, compressive strength, and particles size distribution. Since the thermal expansion coefficient of cristobalite and quartz are 2.6×10-6/℃ and 2.32×10-6/℃ respectively, the composition ratio of each components influence the thermal and physical properties of gold investment materials. For the clinical applications, it is necessary to improve the properties of gold investment materials such as homogeneous size distribution and thermal expansion coefficients. In the present study, effect of inorganic fillers such as cristobalite and quartz on gold alloy investment was investigated to improve the properties of it. The compressive strength and thermal expansion coefficients of the specimens were evaluated. The results showed that cristobalite and quartz were homogeneously distributed by milling. The optimum compressive strength was obtained at the ratio of 42:22 cristobalite and quartz, respectively.

关键词: Investment , null , null , null , null

反应合成温度对锂离子电池正极材料聚氧钼酸盐电化学性能的影响

李文良 , 倪尔福 , 李新海 , 郭华军

中国有色金属学报(英文版) doi:10.1016/S1003-6326(16)64396-0

为了改善聚氧钼酸盐 Na3[AlMo6O24H6](NAM)作为锂离子电池正极材料的电化学性能，通过升高反应溶液的温度，得到了小粒径的NAM材料，并对其进行了红外光谱、XRD、扫描电镜、EIS等分析和充放电性能测试。结果表明，当反应温度高于40°C时，粒径降低到10μm以下。当合成温度达到80°C时，NAM的粒径最小(~3μm)，且其电化学性能最佳，在首次循环过程中，0.04C下的首次放电容量高达409 mA·h/g，库伦效率达95%。

关键词: 聚氧钼酸盐 , 锂离子电池 , 正极材料 , 高容量

MgB2超导块材的非线性磁弛豫性质的研究

李光临 , 宋炜 , 孟立飞 , 冯庆荣 , 高政祥 , 张西祥 , 温戈辉 , 郑荣坤

低温物理学报 doi:10.3969/j.issn.1000-3258.2001.04.014

在32～34K温度和0.5T初始磁场中,MgB2超导块材的磁弛豫性质通过剩余磁化强度M随时间t的变化进行了研究.在初始阶段,M～lnt明显偏离线性,磁通运动接近Zeldov对数模型.足够长的时间后,M～lnt呈现很好的线性,磁通运动符合Anderson-Kim模型.

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矢量磁位法求解轴对称超导悬浮系统的电流分布

郭仁春 , 王金星

低温物理学报 doi:10.3969/j.issn.1000-3258.2008.01.012

矢量磁位是电磁涡流场常用的分析方法.本文利用矢量电位法建立了NdFeB永磁铁和超导体相互作用的电磁场数学方程.对在求解过程中采用Kim模型,通过伽辽金有限元离散,形成线性方程组,解出超导体电流密度分布.这些分析结果为改进超导悬浮系统提供了理论依据.

关键词: YBCO超导体 , 永磁铁 , 矢量磁位 , 有限元

熔融织构YBCO块材磁通动力学参量的磁光图像研究(Ⅱ)

罗康 , 刘蕴宏 , 谢旭 , 罗志全 , 高政祥 , 肖玲 , 任洪涛 , 焦玉磊 , 郑明辉

低温物理学报 doi:10.3969/j.issn.1000-3258.2000.05.004

由熔融织构YBCO块材表面剩余磁感应强度的磁光图像,推算出局域有效激活能U和电流密度j,进而研究磁通运动的局域效应.在样品的边缘区域,U(j)符合Zeldov对数模型,在样品中心区域,U(j)应该符合Anderson-Kim线性模型.在涡旋线向样品中心运动的前沿区域,可以观察到电流密度随时间先升后降.

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Phase relations in the system Y(2)O(3)-CaO-B(2)O(3)

Journal of Alloys and Compounds

The subsolidus phase relations of the system Y(2)O(3) -CaO-B(2)O(3) are investigated by means of X-ray diffraction (XRD) analyses. There are six binary compounds and three ternary compounds in this system. The phase diagram comprises 13 three-phase regions. The ternary compound CaYBO(4) is refined from powder XRD data by the Rietveld method. It has a warwickite-like structure with cell parameters a=10.4354(3) Angstrom, b=9.6126(2) Angstrom, c=3.5880(1) Angstrom and space group Nam. The rationality of the CaYBO(4) structure is examined by Brown bond valence model and IR spectra. (C) 2001 Elsevier Science BY. All rights reserved.

关键词: oxide materials;crystal structure;X-ray diffraction;phase diagram;crystal-structure

功能型聚羧酸系减水剂的合成及其性能研究

张栓红 , 张学强 , 王惠忠

硅酸盐通报

本文选择异戊烯醇聚氧乙烯醚2400 (TPEG2400)为大单体,以丙烯酸(AA),丙烯酸羟乙酯(HEA),丙烯酰胺(AM)、乙烯基膦酸(VPA)等为共聚单体,通过一定条件下的自由基聚合反应,合成一种同时具有缓凝和保坍作用的功能型聚羧酸系减水剂(PC),并对其性能进行检测.试验结果表明:共聚体系中nTPEG2400∶ nAM∶ nAA∶ nHEA∶nVPA的最佳配比为1∶0.35∶0.85∶3.20∶0.12时,合成的PC具有较好的保坍性能,2h坍落度基本无损失;缓凝作用较为显著;对不同水泥的适应性良好,具有较好的应用前景.

关键词: 功能型 , 聚羧酸系减水剂 , 缓凝 , 保坍性能

Liquid-vapour critical point behaviour: especially crossover from two to three dimensions via a magnetic analogy

Physics and Chemistry of Liquids

Motivation for this Letter comes from two experiments. The first, by Kim and Chan (Phys. Rev. Lett. 53, 170 (1984)), measured a two-dimensional (2D) liquid-vapour critical point exponent. The second studied, via the magnetism of ultrathin metal films, the crossover of the critical exponent beta from 2D to 3D. Here, the analogy between magnetic behaviour near criticality and the corresponding liquid-vapour behaviour is first used to discuss the 2D-3D crossover in the latter case. Finally, the experimentally observed magnetic behaviour near criticality is considered for the ferromagnet CrBr(3) to allow fingerprints of the 3D Ising Hamiltonian to be anticipated.

关键词: critical-point effects;critical exponents;crossover;Ising model;criticality;magnetic equation of state;critical exponents;ising-model;equation;crbr3;state

乙烯基笼型倍半硅氧烷/聚丙烯纳米复合材料热降解动力学

曹新鑫 , 高俊刚 , 杜永刚

高分子材料科学与工程

用热重分析(TGA)法研究了乙烯基笼型倍半硅氧烷(V-POSS)/聚丙烯纳米复合材料的热降解动力学.采用Kim-Park,Flynn-Wall-Ozswa和Friedman三种方法计算了共混物的降解反应活化能,结果说明,当V-POSS加入质量分数分别为4%、8%、12%和16%、升温速率为5℃/min时材料热降解起始温度分别提高了27.1℃、29.3℃、52.6℃和66.9℃,热降解反应活化能Ea提高了10 kJ/mol～50kJ/mol,反应级数n也随V-POSS加入量增多有所提高,材料热稳定性得到了改善.

关键词: 笼型聚倍半硅氧烷 , 聚丙烯 , 热重分析 , 降解动力学

垂直磁场中YBCO薄膜的磁通密度和电流密度分布

李志敏 , 覃孟军 , 姚希贤

低温物理学报 doi:10.3969/j.issn.1000-3258.1999.06.001

通过使用扩展后的Mikheenko等人提出的临界态模型，我们用数值计算方法找出了圆盘状超导薄膜在垂直外磁场中的磁通密度分布和电流密度分布.其中考虑到临界电流密度Jc会随外磁场Ha改变而变化，所以我们采用了Kim型表达式Jc(H)=J0/(1+(|H|/H0)n).计算出的初始磁化曲线和磁滞回线与YBCO薄膜的实验曲线（T=51～77K）符合得很好，说明这个方法在这段温区内比较成功.另外我们也得出并讨论了特征参数J0，H0随温度的变化关系.

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