微型薄膜电阻的制备及研究

将具有优异特性的碳纳米管（CNTS）与负性感光胶（SU-8 2002）混合得到复合材料,将不同比例的碳纳米管通过超声工艺分散到SU-8 2002感光胶中,通过UV-LIGA加工工艺,热压处理后实现了微型电阻的快速制备。对复合薄膜电阻的性能进行测试,测试结果表明复合薄膜电阻率随着碳纳米管比例的增加而减小,当碳纳米管的比例为12%时,电阻率减小到0.06 ,复合材料达到逾渗阈值,频率小于1.2GHz时,电阻值的变化范围小于5%,为快速制备微型电阻提供了新的方法。     

聚合物/石墨纳米复合材料及其电学特性研究进展

从热固性树脂/石墨、热塑性树脂/石墨、橡胶/石墨和导电聚合物/石墨等几个方面综述聚合物/石墨纳米复合材料的研究现状。详细介绍了聚合物/石墨纳米复合材料的逾渗特性、伏安特性和压阻特性。对聚合物/石墨纳米复合材料的发展进行了展望。     

网络状碳纳米管薄膜应变传感器的机理研究

计算并评估了应力对网络状碳纳米管薄膜力学和本征电阻各参数的影响,结合逾渗理论分析了碳纳米管薄膜的应变传导机理,建立了模型并推导了碳纳米管薄膜在应力下整体电阻变化率的计算公式,最后将理论计算结果与实验数据进行了比较验证,发现碳纳米管含量变化是引起薄膜电阻变化的关键因素。     

界面残余应变场的会聚束电子衍射测定

用两种会聚束电子衍射(CBED)技术研究了复合材料界面残余应变场.常规正焦CBED方法中,用优化算法使计算的高阶Laue带(HOLZ)线图与实验图达到最佳拟合,进而确定残余应变.给出了一种减少优化计算中可调参数数目的方法.残余应变与表面弛豫引起的界面附近点阵平面面间距的变化、点阵平面的旋转与弯曲使得离焦的大角度会聚束电子衍射(LACBED)图中的衍射线移位、分裂与弯曲.表面弛豫引起的点阵平面的旋转也决定于本征应变.通过使动力学理论计算的LACBED图与实验图达最佳拟合,可以确定本征应变.用该方法研究了颗粒增强复合材料Al2O3/Al与晶须增强复合材料 (K2O@6TiO2) w/Al的界面残余应变场.     

结构和缺陷对二维光子晶体传输性质的影响

用转移矩阵方法计算了二维光子晶体的传输性质，讨论了不同极化光的透射行为，比较了正方点阵、有心正方点阵、含缺陷有心正方点阵光子能带对透射特性的影响，获得了第一禁带特性与光子晶体结构的一些基本关系。     

CaCu_3Ti_4O_(12)-ZnNb_2O_6复合材料的介电逾渗及固相反应

以低εr的ZnNb2O6为基体,以高εr的CaCu3Ti4O12(CCTO)为增强体,研究了CCTO-ZnNb2O6复合材料体系的介电逾渗行为以及高温下的固相反应。结果表明:当CCTO体积分数超过51.0%时,εr突然跃迁,达到5600,表现为介电逾渗。CCTO与ZnNb2O6在900℃以上会发生固相反应,生成Cu0.5Ti0.5NbO4、CaNb2O6、Zn2TiO4及一种与CCTO衍射峰相似、晶格常数比CCTO略大的未知物质,分析认为该未知物质是Nb5+取代CCTO中部分Ti4+而形成的固溶体。     

多梯度下洁净室区域的渗透风量计算与新风量之探讨

主要探讨在多梯度环境下计算一个洁净室区域内的总体渗风量的计算方法并和已有的方法进行对比,提出"房间群"的概念且进一步从工程实际测试角度明确渗透风量的比较准确的算法,从而获得新风的风量优选方式。     

热处理对SiCp／Al尺寸稳定性的影响

采用真空压力浸渗技术制备了两种不同体积分数的SiCp／Al复合材料,研究了热处理工艺对复合材料尺寸稳定性的影响,并对其影响因素进行了分析。结果表明：残余应力的存在对复合材料的尺寸稳定性有着重要的影响;退火和固溶时效处理能提高复合材料的尺寸稳定性,与铸态相比,在100MPa下复合材料的残余应变降低了60％,而淬火处理对复合材料的尺寸稳定性不利。     

电子封装用AlSiC复合材料热导率影响因素探讨

采用模压成型和真空压力浸渗工艺制备了高体积分数SiC增强Al基复合材料(AlSiC)。物相和显微结构研究结果表明,此种方法制备的AlSiC复合材料,组织致密且大小两种粒径的SiC颗粒均匀分布于Al基质中,界面结合强度高;SiC增强颗粒与Al基质界面反应控制良好,未出现Al4C3等脆性相。在此基础上,研究了基体金属、粘结剂用量、粗细SiC颗粒比例对复合材料热导率的影响。结果表明,以1A90高纯铝为基体的复合材料的热导率高于以6061铝合金为基体的复合材料的热导率;粘结剂用量减少时,复合材料热导率提高;当SiC体积分数一定时,AlSiC复合材料的热导率随增强体中粗颗粒SiC比例增大而增大。     

LED点阵动态显示系统设计及仿真

设计了一种基于AT89C51单片机的16×16LED点阵动态显示系统,给出了LED点阵动态显示原理和汉字取模方法;在Proteus环境下进行了点阵显示系统行、列驱动电路硬件设计,同时采用Keil软件完成了系统主程序、显示驱动程序的设计;最后进行了系统Proteus仿真,降低了成本,提高了开发效率,并获得了良好的显示效果。     

Simulation and research of percolation phenomenon in T-ZnOw resin matrix composite

A novel three-dimensional lattice model of tetrapod-like zinc oxide whisker (T-ZnOw) resin matrix composite with a coordination number of 12 is constructed based on the special structure of T-ZnOw; the percolation phenomenon of the system is simulated by the Monte Carlo method,and the percolation threshold is obtained at 23.2%.The critical mixing ratio of T-ZnOw is calculated by considering the practical factors,and the result basically agrees with the reported one.Theoretical calculation shows that the critical mixing ratio mainly depends on the L/D ratio of T-ZnOw,and is also related to the size of T-ZnOw as well as the preparation method of the composite.The microwave absorbing mechanism of T-ZnOw composite is discussed,and conductivity loss and point discharge caused by the polarization effect are regarded to be two important means of energy dissipation.     

Facile synthesis of Cu/tetrapod-like ZnO whisker compounds with enhanced photocatalytic properties

Cu/tetrapod-like ZnO whisker (T-ZnOw) compounds were successfully synthesized using N₂H₄·H₂O as a reducing agent by a simple reduction method without any insert gas at room temperature. The crystal phase composition and morphology of the as-prepared samples were investigated by XRD, SEM and FESEM tests. The photocatalytic property of the as-prepared samples was detected by the degradation of methyl orange (MO) aqueous solution under UV irradiation. It can be found that Cu nanoparticles (CuNPs) dispersed on the surface of T-ZnOw increased with the increasing of Cu/Zn molar ratios (Cu/Zn MRs), and an octahedral structure of CuNPs was obtained when the sample was prepared with less than and equal to 7.30% Cu/Zn MR, but tended to a spherical or nanorod structure of CuNPs densely arranged on the surface of T-ZnOw, which is prepared by Cu/Zn MRs up to 22.00%. All the compounds exhibited excellent photocatalytic activity in decomposing of MO than T-ZnOw, the photocatalytic property of the samples increased with the increasing of Cu/Zn MRs up to 7.30%, while it decreases when further increasing the Cu/Zn MRs. The Schottky barrier of the Cu/T-ZnOw compound can effectively capture photoinduced electrons from the interface and enhanced the photocatalytic property of T-ZnOw.     

Tuneable Piezoresistance of Graphene-Based 2D:2D Nanocomposite Networks

Piezoresistive nanocomposites are an important class of materials that allow the production of very sensitive strain sensors. Herein, a new class of piezoresistive nanocomposites prepared by mixing different types of 2D nanosheets is explored. In this way, three distinct types of nanocomposite are produced by mixing conducting and insulating nanosheets (graphene, Gr and boron nitride, BN), conducting and semiconducting nanosheets (graphene and tungsten diselenide, WSe₂ or tungsten disulfide, WS₂) as well as mixing two different types of conducting nanosheets (graphene and silver, Ag). For each nanocomposite type, a different dependence of composite conductivity on filler volume fraction is observed although all behaviors can be fully described by percolation theory. In addition, each composite type shows different piezoresistive properties. Interestingly, while the conductor insulator composites show the standard monotonic relationship between gauge factor and conductivity, both conductor:semi-conductor and conductor:conductor composites show very unusual behavior, in each case displaying a peak engage factor at the percolation threshold. In each case, percolation theory is used to develop simple equations for gauge factor as a function of both volume fraction and conductivity that fully describes all experimental data. This work expands the understanding of piezoresistive nanocomposites and provides a platform for the engineering of high-performance strain sensors.     

Effect of a critical percolation threshold in purified short carbon nanotube-polymer/ZnS:Cu,Cl composite on electroluminescence

AC driven inorganic electroluminescence (EL) of the carbon nanotube (CNT)-polymer/phosphor composite was fabricated to investigate the effect of the critical percolation threshold by CNT concentration on EL performance. In order to control the appropriate CNT condition in EL device, CNTs were shortened by cryogenic crushing and purified by thermal treatment. Among various CNT concentrations in the composite film, the critical percolation threshold can be found to be 0.0925 wt.% by fitting conductivity data of the composite film. Near the critical percolation threshold of a CNT concentration, the EL performances of the composite EL were greatly increased compared to the reference EL. The tunneling barrier thickness at the ZnS–Cu_xS contact could become thin to induce more charge carrier tunneling into ZnS host lattice by the local field enhancement of CNTs, resulting in increased electron–hole recombination to produce more light emission.     

柔性导电硅橡胶复合材料的制备及其压阻性能

将镀银导电纤维填料与硅橡胶复合,制备了柔性导电橡胶复合材料。研究了导电橡胶电导率、电阻蠕变行为及压阻性能随填料长径比、含量的变化。结果表明:导电橡胶的渗流阈值,随着镀银导电纤维填料长径比的增大而减小;恒定应力下,导电橡胶的电阻蠕变表现为电导率随时间非线性增加;在1.0MPa应力范围内,导电橡胶电导率的变化呈现出正压阻变化效应(PPCR);随着填料质量分数的增大,压应力的增加,导电橡胶的压阻效应变得不明显。     

Crossover of critical behaviour of electric failure in metal-non-metal systems near the percolation threshold

The critical behaviour of electric current and field in three-dimensional composite media is examined. On the basis of a weak-link model, critical exponents above and below the percolation threshold are calculated taking into consideration different failure criteria. Depending on the set of parameters chosen, a cross over of the main role in electric failure played by the high and low conductivity components, respectively, is predicted.     

Percolation dominated electron transport in Tetracyanoquinodimethane mixed 4,7-diphenyl-1,10-phenanthroline thin films

Highly conducting and electron transporting organic semiconductor tetracyano-quinodimethane (TCNQ) has been added to the well known electron transporting material 4,7-diphenyl-1,10-phenanthroline (BPhen) in various mixing percentages. Electron only devices exhibited a distinctive transition from low to high conductivity. The results have been found to be in good agreement with classical percolation theory with a percolation threshold of 3.8 wt.% and a critical exponent value of 1.3. This demonstrates the formation of a morphologically stable 2D percolating network that has been supported by AFM analysis. The composition thus formed indicates a promising electron injecting material for optoelectronic devices.     

四针状氧化锌晶须的电磁波损耗机理

分析了四针状氧化锌晶须（T—ZnOw）的电磁波损耗机理,首先从T—Znow形成立体导电网及其感应涡流损耗和品须内部散射电场计算等宏观角度讨论了入射电磁波损耗机制;其次,从针尖电荷集中和界面极化的角度分析了该晶须的电磁波损耗机理;最后,用量子力学的观点讨论了T—ZnOw与电磁波作用机理,发现隧道效应和量子势阱理论都可用于解释该晶须在2～18GHz频率范围内的电磁波损耗。     

Evolution of a Magnetoresonance Line Near to a Limit of Percolation in Dilute Magnetics

In paper the results of numerical modeling of a magnetic resonance in dilute magnetics near to a threshold of a percolation are discussed. The classical equation of motion of magnetic moments is used in view of an exchange interaction such as RKKI and imitation of spin-phonon interaction by Monte-Carlo method. It is shown, that cluster structure of a magnetic and threshold of percolation are determined by critical distance, on which there is a change of a sign of an exchange interaction. In an examination of percolation phase transition the jump change of breadth of a line of a magnetic resonance is set, that can form the basis for experimental definition of a threshold percolation and parameters of an exchange interaction by methods of a radiospectroscopy.