Xiaobing REN and Xiaotian WANG (College of Materials Science and Engineering
,
Xi'an Jiaotong University Xi'an 710049
,
China)K.Shimizu and T.Tadaki (Institute of Scientific and Industrial Research
,
Osaka University
,
8-1
,
Mihoga-oka
,
Ibaraki
,
Osaka
,
567
,
Ja
材料科学技术（英文）
A theoretical study is developed on the evolution and mechanism of an ordering coupled phase separation, and on the origin of a resultant tweed microstructure. It is found that long-range elastic interaction among atoms with different atomic sizes plays a key role in the phase sep aration, and that the evolution of the phase separation is very similar to that Of conventional spinodal decomposition except that the separation is dependent on an elastic interaction order ing (EIO). This "EIO coupled spinodal decomposition" is shown to exhibit a periodical or tweed microstructure being accompanied by an EIO. It is also found that a large atomic size factor yields a large positive contribution of EIO to spinodal decomposition. Generally it is thermodynamically and kinetically favorable for the EIO to precede the onset of spinodal decomposition,though the former is not separable from the latter as a whole. We suggest that an initially disordered solid solution undergoes an EIO first, and then the partially ordered solid solution starts to decompose via a spinodal mechanism. Solute-enriched regions increase their degree of order along with an increase in solute content, and solute-depleted regions decrease their degree of order together with a decrease of solute content. The final microstructure is characterized by a periodical array of highly ordered solute-enriched regions and nearly disordered solute-depleted regions. The notion of EIO coupled spinodal decomposition is in general agreement with the transformation behaviour of a large number of alloy systems.
关键词:
黄庚
,
王文继
功能材料
以Li4SiO4为母体,叶蜡石为原料的Li8Al1-xSi2xP1-xO8系统的锂快离子导体,经高温固相反应制得.X射线衍射分析结果表明该系统在0.5＜x＜0.9的组成范围内形成单一的固溶体相,其空间群为P21/m,导电性能测试结果表明x=0.6的合成物具有最高的电导率,在673K时其电导率达到2.6×10-2S/cm,其活化能为60.73kJ/mol(温度区间373～673K).
关键词:
锂快离子导体
,
叶蜡石
,
矿物快离子导体
梁娅
,
刘秀明
,
陈苏战
,
魏荣宝
应用化学
doi:10.3969/j.issn.1000-0518.2007.06.004
利用1,3-环己二酮和1,4-苯二甲醛为原料,在微酸介质中通过羟醛缩合和脱水反应,合成了9,9'-(1,4-亚苯基)-2H,2'H,3H,3'H,4H,4'H,5H,5H',6H, 6'H,7H,7'H,9H,9'H-十四氢-二-吖啶-1,1',8,8'-四酮(化合物Ⅰ). 提出了化合物Ⅰ生成的反应机理. 将化合物Ⅰ与季戊四醇在I2催化下反应,生成了目标化合物9,9'-(1,4-亚苯基)-2H,2'H,3H,3'H,4H, 4'H,5H,5H',6H,6'H,7H,7'H,9H,9'H-十四氢-二-吖啶-1,1',8,8'-四酮缩双季戊四醇(化合物Ⅱ),收率为40%. 产物和中间体用IR、1H NMR、MS和元素分析进行了结构表征. 在含有螺环单元的化合物Ⅱ1H NMR中,亚甲基中的8个氢由于受手性轴和苯环的影响而裂分成8重峰.对影响反应的因素特别是副产物生成的原因进行了探讨
关键词:
对苯二甲醛
,
季戊四醇
,
螺环化合物
,
环己二酮
沈容
,
王聪
,
王天民
,
熊常健
稀有金属
doi:10.3969/j.issn.0258-7076.2003.03.002
采用固相化学反应的方法,成功合成了立方结构的Zr1-xHfxW2O8(x=0,0 3, 0 5, 0 7, 1 0)系列材料.X射线衍射结果表明,Hf4+能替代Zr4+形成二元固溶体,固溶体的晶胞参数与体积随着Hf4+含量x的增加而降低.采用高、低温X射线衍射的方法测定晶胞参数和体积随温度的变化关系,结果表明:Zr1-xHfxW2O8化合物在实验温度范围具有强烈的负热膨胀效应,但其负热膨胀系数不随Hf4+含量x变化.在298～973K,Zr1-xHfxW2O8线膨胀系数α1约为-6×10-6 K-1;在83～298K,Zr 0.5Hf0.5W2O8的α1-9.6×10-6 K-1.变温XRD研究还表明Zr1-xHfxW2O8化合物从α-ZrW2O8相向β-ZrW2O8相的转变温度随Hf4+含量x的增加而略有升高,热重分析(TGA)研究结果表明,Zr1-xHfxW2O8在室温大气条件下不吸水.
关键词:
无机非金属材料
,
负热膨胀
,
Zr1-xHfxW2O8
,
X射线衍射
,
骨架结构
曹笃盟
,
李志友
,
周科朝
稀有金属材料与工程
采用固相反应法制备了Li1+xV3-yMyO8(M=Mo,P;0≤y≤0.4),研究了不同Mo和P含量对Li1+xV3O8相的影响,并首次对其进行了高温阴极放电性能的研究.结果表明:Mo和P掺杂量分别为y≤0.2和y＜0.2时可获得纯Li1+xV3O8相;Mo掺杂使Li1+xV3O8峰值电压提高0.3 V,比容量提高25%,嵌入的Li+量最高可达x=3.8;P掺杂(y≤0.20)对Li1+xV3O8的峰值电压和比容量影响较小.化学嵌锂实验也证实掺杂后的材料具有更快的Li+嵌入速度.
关键词:
Li1+xV3O8
,
热电池
,
掺杂
,
比容量
宋福生
,
李月明
,
沈宗洋
,
谢志翔
,
王竹梅
,
廖润华
人工晶体学报
采用传统的固相反应合成法制备了Zn1-xMgx ZrNb2O8(x=0-0.4)微波介质陶瓷.研究了Mg2+的取代量x对Zn1-xMgxZrNb2O8陶瓷的烧结特性、物相组成、显微结构以及微波介电性能的影响.结果表明:Zn1-xMgxZrNb2O8陶瓷的烧结温度随着Mg2+取代量x的增加,略有提升;当x=0-0.3时,体系形成了单相的(Zn,Mg) ZrNb2O8固溶体,而当x=0.4时,体系除了形成(Zn,Mg) ZrNb2O8固溶体外,还有少量未知杂相生成;随着Mg2+的取代量的增加,Zn1-xMgxZrNb2O8陶瓷的微波介电性能呈现不同的变化规律.当x=0.2时,组分为Zn0.8Mg0.2ZrNb2O8的陶瓷在1230℃烧结4h,可获得较佳的微波介电性能:εr=27.55,Q ×f=58731 GHz,τf=-66.7×10-6/℃.
关键词:
Zn1-xMgxZrNb2O8
,
固溶体
,
物相组成
,
微波介电性能
Molecular Physics
The geometrical structures, relative stabilities, electronic and magnetic properties of calcium-doped gold clusters Au(n)Ca (n = 1-8) have been systematically investigated by employing density functional method at the BP86 level. The optimised geometries show that the ground-state structures are planar structures for Au(n)Ca (n = 3-8) clusters. Ca-substituted Au(n+1) clusters, as well as Au-capped Au(n-1)Ca clusters, are dominant growth patterns for the AunCa clusters. The relative stabilities of Au(n)Ca clusters for the ground-state structures are analysed based on the averaged binding energies, fragmentation energies and second-order difference of energies. The calculated results reveal that the Au(2)Ca isomer is the most stable structure for small size Au(n)Ca (n = 1-8) clusters. The HOMO-LUMO energy gaps as a function of the cluster size exhibit a pronounced even-odd alternation phenomenon. Subsequently, charge transfers and magnetic moment of Au(n)Ca (n = 1-8) clusters have been analysed further.
关键词:
Au(n)Ca clusters;geometrical configuration;density function method;bonding properties;basis-set;potentials;transition;molecules;anions;atoms
冯秋元
,
方波
,
陈志勇
,
马宏刚
,
李渭清
,
张平辉
,
窦立军
,
王清江
钛工业进展
为满足我国航空发动机对高温钛合金的需求，开展了TC8-1钛合金铸锭及其大规格棒材的研制。结果表明，研制的φ820 mm TC8-1钛合金大型铸锭成分均匀、冶金质量良好。制备的φ130～φ200 mm 大规格棒材的室温及高温力学性能、热稳定性能、持久性能、蠕变性能和显微组织均符合技术标准要求，能够满足某型号发动机用材需求，填补了国内空白。同时测定了TC8-1钛合金的线膨胀系数、热导率等物理性能数据，为该合金的应用提供参考。
关键词:
TC8-1钛合金
,
大规格棒材
,
显微组织
,
力学性能
,
物理性能
贾玉鑫
,
黄金亮
,
冯剑
材料热处理学报
采用Gleeble-1500D热模拟机对Mg-8Li-2Al-1Zn合金进行热压缩实验,研究了变形温度为523 ～ 723 K、应变速率为0.01 ～10 s-1条件下的合金热变形行为,并建立了合金的流变应力本构方程及热加工图.结果表明:Mg-8Li-2Al-1Zn合金的流变曲线均属于动态再结晶型,流变应力随着温度升高(应变速率降低)而减小.显微组织的变化验证了动态回复和动态再结晶的发生.Mg-8Li-2Al-1Zn合金流变应力本构关系可以用双曲正弦函数和Z参数准确的描述,平均应力指数为4.62,平均热激活能为139.35 J/mol.根据建立的加工图,预测合金热变形的最佳工艺参数为:523 ～573 K,0.1～1 s-1.
关键词:
镁锂合金
,
热变形
,
动态再结晶
,
本构方程
,
微观组织
Journal of Physics-Condensed Matter
The electronic structure of Ti8C12 and Zr8C12, in both D2d and T(h) symmetry, are investigated by the first-principles DV-Xalpha SCC method. The calculated binding energies of the D2d structure are stronger than those of the T(h) structure. It reveals that the D2d cluster is more stable than the T(h) cluster. Strong interactions between C-C and Ti-C, Zr-C covalent bonding are observed. When the transition-state procedure is used, ionization potentials of 7.04 eV and 6.58 eV are obtained for D2d Ti8C12 and Zr8C12 molecules, respectively.
关键词:
cluster;c-60;fe
