Gap modulation in MCu[Q1−xQ′x]F (M=Ba, Sr; Q, Q′=S, Se, Te) and related materials

BaCuQF (Q=S, Se, Te) materials exhibit band gaps that allow transmission of much of the visible spectrum. BaCuSF is transparent in thin-film form with a band gap of 3.1 eV. Band gap estimates for powders of the solid solution series BaCuS_1−xSe_xF were obtained from wavelength-dependent diffuse-reflectance measurements using an integrating sphere. The band gap can be tuned by the substitution of Se for S to 2.9 eV for BaCuSeF. The decrease scales almost linearly with the increase in the volume of the tetragonal unit cell, which is determined primarily by the expansion of the a lattice parameter; the overall volume increase is 7.0% from x=0 to 1. Further reduction of the band gap is observed in BaCuSe_1−xTe_xF solid solutions, where a unit cell volume increase of 5.5% produces a band gap of 2.7 eV in BaCuSe_0.5Te_0.5F. Powders and films of BaCuSF exhibit strong red luminescence under ultraviolet excitation, which is suppressed by K doping. Additional tuning of band gap and electrical properties (the materials are p-type conductors) can be achieved by replacing Ba with Sr.     

Preparation and characterization of proton‐exchange hybrid membranes

Two types of composite were prepared, based on a thermoplastic polymer, polyvinylidene fluoride (PVDF), and an elastomer, ethylene‐propylene‐diene terpolymer (EPDM), respectively. We obtained both series by addition of an inorganic proton‐conducting antimonic acid derivative (HSb) and polystyrene crosslinked with a small percentage of divinylbenzene (PS‐co‐DVB). From these composites, membranes were obtained and subjected to a heterogeneous‐phase sulfonation reaction with chlorosulfonic acid. All experimental materials were characterized from a morphological and electrical point of view, by means of techniques such as differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), non‐isothermal crystallization and complex impedance analysis. Copyright © 2005 Society of Chemical Industry     

Nonlinear electrical transport in K-TCNQ at low temperatures

A remarkable nonlinearity has been observed for electric transport in K-TCNQ (potassium tetracyanoquinodimethane) quasi-one-dimensional conductor. The negative differential resistance region appears afterV _m (turn over voltage), beyond which voltage goes down with increase of current. A possible mechanism is discussed in terms of dynamics of charged solitons and domain walls in one-dimensional molecular stacks of these types of crystals.     

氯离子导体及其应用开发

本文围绕有希望实现实用化的PbCl_2基氯离子导体,着重从材料研制、应用探索及应用前景这三个方面概述了氯离子导体研究的状况和今后动向。     

Mechanosynthesis of complex oxides and preparation of mixed conducting nanocomposites for catalytic membrane reactors

Nanopowders of LaGaO₃- and LaMnO₃-based complex perovskites (P) and ceria-based fluorites (F) were prepared by mechanosynthesis. Compatible nanocomposites F + P and P + P with mixed ion and electron conducting (MIEC) properties were prepared and sintered at moderate temperatures up to dense ceramics. The obtained materials were studied by means of XRD, SEM, TEM, electrical conductivity measurements, temperature programmed (TP) reduction/oxidation and preliminary estimations of permeability were obtained. A new strategy based on the advantages of the mechanochemical ceramic approach is proposed to design multilayer ceramic membranes for CMR. Casting technology and one-step sintering were used for the production of thin film membranes with MIEC properties on porous substrates. The coarse fraction of as-milled powders from agglomerates with density 70% was used for the porous substrate, and fine fractions of aggregates with sizes <1 μm were used in preparation of composites for thin dense films. Ceria-based composites prepared by the Pechini route and/or mechanochemical method are proposed as materials for protecting thin films.     

全化学法制备缓冲层和YBaCuO超导涂层

用化学溶液沉积法,尤其是金属有机物沉积法（MOD）制备第二代超导带材,包括缓冲层和YBaCuO涂层,在当前超导带材研究中具有重要的意义．因为其成本低、操作简单、便于规模化生产,可能成为制备高温超导带材最有前途的方法．文内详述了用化学气相沉积,化学溶液沉积,电泳共沉积以及超声雾化热分解等方法制备YBaCuO超导涂层的国内外进展,介绍了在LaAlO3单晶上以及金属基带上制备钙钛矿结构缓冲层的主要种类和特征,也介绍了当前研究的热点之一,导电缓冲层的作用、制备方法和研究进展．     

质子交换膜燃料电池有序化膜电极研究进展

质子交换膜燃料电池的发展和应用是促进现代生活方式低碳环保化的最重要路径之一。膜电极是质子交换膜燃料电池的核心部件,实现膜电极结构的有序化是同时满足低铂载量和高电化学性能要求的关键。本文系统总结和分析了最近有关有序化膜电极的相关研究进展。与发展较为缓慢的质子导体有序化相比,以催化剂有序化和催化剂载体有序化为路径实现的有序化膜电极结构优化已经得到快速发展,对于促进质子交换膜燃料电池规模化应用表现出极大的发展潜力。     

基于传感器技术的导线舞动状态监测评估系统

导线舞动造成的危害一般主要是由于舞动幅值过大,造成相间气隙不够引起相间闪络造成。针对导线舞动的特点,基于传感器技术和虚拟仪器技术,开发了导线舞动状态监测评估系统。舞动监测终端实时测量现场舞动数据,经过单片机处理,通过GPRS无线传输模块发送至上位机完成图形化显示,利用上位机软件搭建的导线舞动状态评估模型实现导线舞动状态的评估。在实验室搭建了导线舞动模拟平台,引入舞动摆角,进行了运行试验。试验结果表明:该系统能有效监测导线舞动状态变化,较准确地完成导线舞动状态评估。     

互连寄生电容器中屏蔽导体的快速判断

应用层次式Ｚ缓冲区可视性算法的思想,实现了一种互连寄生电容器中屏蔽导体的快速判断算法,能准确地确定对电容值影响较小的导体,并加以消除,当用边界元法提取甚多环境导体对关键路径产生的寄生电容时,可在满足计算精度的条件下,显著地提高计算速度。