Phase behavior of ternary blends containing dimethylpolycarbonate,tetramethylpolycarbonate and poly[styrene‐co‐(methyl methacrylate)] copolymers (or polystyrene)

The miscibility and phase behavior of ternary blends containing dimethylpolycarbonate (DMPC), tetramethylpolycarbonate (TMPC) and poly[styrene‐co‐(methyl methacrylate)] copolymer (SMMA) have been explored. Ternary blends containing polystyrene (PS) instead of SMMA were also examined. Blends of DMPC with SMMA copolymers (or PS) did not form miscible blends regardless of methyl methacrylate (MMA) content in copolymers. However, DMPC blends with SMMA (or PS) blends become miscible by adding TMPC. The miscible region of ternary blends is compared with the previously determined miscibility region of binary blends having the same chemical components and compositions. The region where the ternary blends are miscible is much narrower than that of binary blends. Based on lattice fluid theory, the observed phase behavior of ternary blends was analyzed. Even though the term representing the Gibbs free energy change of mixing for certain ternary blends had a negative value, blends were immiscible. It was revealed that a negative value of the Gibbs free energy change of mixing was not a sufficient condition for miscible ternary blends because of the asymmetry in the binary interactions involved in ternary blends. Copyright © 2004 Society of Chemical Industry     

地下水污染试验研究进展

本文在总结国内外众多学者有关污染物在含水层中的运移规律研究成果的基础上，介绍了地下水污染试验研究的最新进展；并据此认为，三维弥散，各向异性含水层介质中污染物的迁移，非饱和土层中的污染物多相迁移和吸力的关系等将成为今后地下水污染传播研究的主要问题。     

掺杂VO2的特性、制备方法及应用

VO2在68℃时发生从低温的单斜相向高温四方相转变，同时伴随着光、电、磁性能的突变。通过掺入其它杂质元素，能有效改变其相变温度和光、电性能，这些优异特性使其具有更好的应用前案。本文综述了掺杂的原理，掺杂对VO2相变影响、常用的掺杂方法及目前的应用情况，这对其进一步的研发应用具有重要的意义。     

Electrical conductivity of ferroelectric sodium vanadate,rubidium vanadate,cesium vanadate and their solid solutions

The d.c. electrical conductivity of sodium vanadate, rubidium vanadate, cesium vanadate and their solid solutions sodium-rubidium vanadate and sodium-cesium vanadate were studied by a two-probe method in the temperature range covering their transition points. The electrical conductivity shows sharp change at the phase transition temperature of these materials. In NaVO₃, RbVO₃ and CsVO₃, increase in d.c. conductivity is observed in the ferroelectric region while nonlinearities are observed above transition temperatures. In solid solutions, the activation energy in the paraelectric state is higher than that in the ferroelectric state and depends upon sodium concentration.     

Al/Fe2O3反应合成材料热力学

运用CALPHAD技术，基于多组元多相复杂平衡体系的吉布斯自由能最小化原理，用大型集成数据库F^*A^*C^*T系统，考察了铝和氧化铁经典反应体系的热力学规律。针对材料的反应合成技术，计算了化学计量铝和氧化铁体系以及各种产物中物种的相变情况；分析了原料初始温度、配料比和SiO2含量对绝热温度和平衡组成的影响。     

用纳米棒ZnO作模板生长无支撑的AlN纳米晶

用金属有机物气相外延在纳米棒ZnO模板上沉积AlN薄膜.SEM测试表明该薄膜形成了一种倾倒纳米棒的表面.而GIXRD测试进一步证实它是纤锌矿结构的AlN,晶粒尺度约为12nm,接近于ZnO纳米棒的直径(30nm).这意味着纳米棒结构的ZnO能限制AlN的横向生长.此外,高温下用H2刻蚀ZnO直接在生长中实现了外延层的剥离.最终得到了无支撑的AlN纳米晶,完整无破损的区域约为1cm×1cm.定义这个生长机制为"生长-刻蚀-合并"过程.     

Influence of nano-scaled dispersed second phase on substructure of deformed dispersion strengthened copper alloy

The deformation behavior of dispersion strengthened copper alloy Cu-Al2O3 was studied by TEM. The results show that nano-scaled dispersed second phase not only increases dislocation density in matrix, but also has an important influence on the dislocation substructure. The presence of fine dispersed Al2 O3 particles results in a uniform and random dislocation distribution in matrix copper and causes the difficulty in formation of dislocation cell structure and the decrease in the amount of cell structure during deformation. Deformation gives rise to much more dislocations and dislocation cells form more difficultly and the decrease in the cell size with the increase of dispersion degree.     

Preparation of BaMgAl10O17∶Eu2+ and Its Phase Behavior in Microemulsion System

BaMgAl10O17∶Eu2 (BAM) was prepared in the microemulsion system and its phase behavior was studied. There exists a small region in the reverse microemulsion system where the dispersed particles are of spherical form. In this way, BAM blue phosphor with good dispersion can be synthesized. The microemulsion phase diagrams of the pseudo-ternary system (Triton X-100/cosurfactant-oil-BAM brine) were first established intuitively by the dilution method. The microstructure of microemulsions was determined through eyeballing, conductance technique, and polar optical microscopy. Its phase behavior is affected by various factors, such as temperature (room temperature, 30, 40 ℃), oil, surfactants, and cosurfactants in microemulsions. According to the phase diagrams, the microemulsion system of Triton X-100/1-hexanol-hexane-BAM brine was chosen to prepare the precursor. The BAM phosphor can be obtained via sintering the precursor at a comparatively low temperature. The phosphors were characterized by XRD and vacuum ultraviolet (VUV) spectra.     

Nanostructured titanium aluminides prepared by mechanical alloying and subsequent thermal treatment

Ternary Ti-Al-Nb elemental powder blends with minor addition of SiC were synthesized in a high energy ball mill in order to understand the structural evolution during mechanical alloying (MA) and subsequent thermal treatment. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) techniques were employed to study the structural development during MA. Ti-48%Al-4%Nb-3%SiC and Ti-48%Al-8%Nb-3%SiC blends milled to 20 h were subjected to thermal treatment at 750 °C for 1 h in vacuum. Repeated cold welding and fracturing events of MA resulted in nanocrystalline structure with supersaturated solid solution and amorphous phase. The powder particles were also refined to submicron size due to high energy collision. The nanocrystalline supersaturated solid solution evolved by MA was sustained for prolonged milling time. There was no evidence of intermetallics formation even after early solid solubility extension and formation of nanocrystalline structure. However, nanostructured TiAl and Ti₃Al intermetallic compounds were observed after giving thermal treatment to MA powder blend. Since their surface area and energy were enhanced to a great extent, the dispersed ceramic particles reacted with titanium and formed nanosilicide particles.     

SHS of shape memory CuZnAl alloys

Aiming at preparation of shape memory alloys (SMAs), we explored the SHS of Cu_{1 − x} Zn_{1 − y} Al_{1 − z} alloys (0.29 < x < 0.30, 0.74 < y < 0.75, and 0.83 < z < 0.96). The most pronounced shape memory effect was exhibited by the alloys of the following compositions (wt %): (1) Cu(70.6)Zn(25.4)Al(4.0), (2) Cu(70.1)Zn(25.9)Al(4.0), and (3) Cu(69.9)Zn(26.1)Al(4.0). The effect of process parameters on the synthesis of CuZnAl alloys was studied by XRD, optical microscopy, and scanning electron microscopy (SEM). The grain size of CuZnAl was found to depend on the relative amount of the primary CuZn and AlZn phases. Changes in the transformation temperature and heat of transformation are discussed in terms of ignition intensity and compaction. Mechanism of the process depends on the level of the temperature attained relative to the melting point of components. At the melting point of AlZn, the process is controlled by the solid-state diffusion of AlZn into a product layer. The ignition temperature for this system depends on the temperature of the austenite-martensite transformation in CuZnAl alloys. The composition and structure of the products was found to markedly depend on process parameters. The SHS technique has been successfully used to prepare a variety of SMAs.