Au-Ag系统的扩散系数及其扩散激活能的研究

在银基底上蒸镀80nm的金薄膜,然后用不同温度和时间间隔对这些样品进行热处理。再用PHI 550型俄歇电子能谱仪测出上述样品金膜中银的浓度剖面分布。根据银的浓度剖面分布及Hall公式算出Au-Ag系统的互扩散系数。由Leclaire公式计算出该系统的晶界扩散系数。从Arrhenius方程得出互扩散及晶界扩散激活能。并对实验和计算结果进行了讨论。     

Optical, structural and surface characterization of CdO:Mg films

In this work, we have tried to improve some physical properties of CdO films by Mg doping. Ultrasonic spray pyrolysis technique has been used to obtain the films. Thicknesses and refractive indices of the films have been determined by Spectroscopic ellipsometry technique using Cauchy-Urbach model for fitting. Transmission and reflectance spectra have been taken by UV Spectrophotometer, and band gap values have been determined by optical method. X-ray diffraction patterns have been used to study the structural properties. Texture coefficient, grain size and lattice constants have also been determined. AFM images have been taken to see the effect of Mg doping on surface topography and roughness of CdO films. Finally, it has been concluded that Mg doped CdO films (especially at 4%) have improved properties and are good candidates for photovoltaic applications.     

A ceramic based on partially stabilized zirconia: Synthesis,structure, and properties under dynamic load

A ceramic based on zirconia partially stabilized by yttrium oxide has been prepared. The main properties of the prepared ceramic have been characterized: density, ultimate strength under twisting, microhardness, elasticity coefficients, etc. The microstructure and phase composition of the ceramic and its phase transformations under mechanical action have been studied. The properties of the ceramics under dynamic load have been studied, and the values of the dynamic elastic limit and splitting strength have been obtained. The results have been compared with the literature data.     

Recent Progress in the Synthesis of Porous Carbon Materials

In this review, the progress made in the last ten years concerning the synthesis of porous carbon materials is summarized. Porous carbon materials with various pore sizes and pore structures have been synthesized using several different routes. Microporous activated carbons have been synthesized through the activation process. Ordered microporous carbon materials have been synthesized using zeolites as templates. Mesoporous carbons with a disordered pore structure have been synthesized using various methods, including catalytic activation using metal species, carbonization of polymer/polymer blends, carbonization of organic aerogels, and template synthesis using silica nanoparticles. Ordered mesoporous carbons with various pore structures have been synthesized using mesoporous silica materials such as MCM‐48, HMS, SBA‐15, MCF, and MSU‐X as templates. Ordered mesoporous carbons with graphitic pore walls have been synthesized using soft‐carbon sources that can be converted to highly ordered graphite at high temperature. Hierarchically ordered mesoporous carbon materials have been synthesized using various designed silica templates. Some of these mesoporous carbon materials have successfully been used as adsorbents for bulky pollutants, as electrodes for supercapacitors and fuel cells, and as hosts for enzyme immobilization. Ordered macroporous carbon materials have been synthesized using colloidal crystals as templates. One‐dimensional carbon nanostructured materials have been fabricated using anodic aluminum oxide (AAO) as a template.     

Properties of optical spatial solitons in photorefractive crystals with special emphasis to two-photon photorefractive nonlinearity

We have reviewed recent developments of some aspects of optical spatial solitons in photorefractive media. Underlying principles governing the dynamics of photorefractive nonlinearity have been discussed using band transport model. Nonlinear dynamical equations for propagating solitons have been derived considering single as well as two-photon photorefractive processes. Fundamental properties of screening and photovoltaic solitons have been considered. For each type of solitons, three different configurations i.e., bright, dark and gray varieties have been considered. Mechanisms of formation of these solitons due to single as well as two-photon photorefractive processes have been considered and their self bending discussed. Vector solitons, particularly, incoherently coupled solitons due to single photon and two-photon photorefractive phenomena have been highlighted. Existence of some missing solitons have been also pointed out. In addition, incoherent solitons and discrete spatial solitons in optically-induced photorefractive lattices are also discussed.     

低摩擦系数固体润滑涂层研究进展

低摩擦系数固体润滑涂层在许多领域得到了广泛应用,探索新型固体润滑涂层体系及其制备技术是摩擦学研究的热点.本文综述了聚四氟乙烯自润滑涂层、二硫化钼自润滑涂层以及类金刚石薄膜作为自润滑减摩涂层的原理及其研究取得的进展,介绍了新型自润滑涂层的制备技术,同时还指出了固体润滑涂层有待进一步研究的问题.     

Various refined theories applied to damped viscoelastic beams and circular rings

In this work, a number of enhanced finite beam elements has been tested considering layered structures with viscoelastic layers. The viscoelastic properties have been defined with the complex modulus approach, and the equations of motion have been derived using the principle of virtual displacement. Higher-order theories, based on equivalent single-layer and the layerwise approaches, have been obtained with the Carrera unified formulation, which makes it possible to generate an infinite number of kinematic approximations. Both Lagrange-type elements and higher-order zigzag theories have been developed within the layerwise approach. On the other hand, Taylor-like expansions and Murakami-type zigzag functions have been used to conceive the equivalent single-layer models. Numerical simulations have been performed considering symmetric and asymmetric laminated structures with rectangular and circular cross sections. The results are reported in terms of frequencies, modal loss factors, and frequency responses. The obtained results have been compared with solutions published in the literature and with solid finite element models. The accuracy of the different formulations has been found to be problem dependent to a great extent.     

大跨度混凝土连续梁桥的病害成因分析

自20世纪80年代以来,我国建成了大量大跨度预应力混凝土连续体系桥梁,取得了辉煌成就,但随着桥梁建设数量与使用年限的增加,该类桥梁在施工与运营期陆续出现一些具有共性的病害:跨中挠度过大、箱梁开裂与跨中合龙段底板剥离等,而且有些病害已经导致桥梁重大的安全事故与经济损失。文章对国内数十座桥梁出现的病害随时间变化发展的趋势、在空间上分布的形态等进行了分析。根据现有的理论研究成果,分析了腹板斜裂缝、底板纵向裂缝、合龙段底板分层等病害的形成机理,提出了控制裂缝等病害发生的措施,并说明了这些控制措施在泰州大桥预应力桥梁上的应用情况。     

沸石分子筛半导体化合物簇复合材料

在沸石分子筛的微孔中应用化学反应生成具有纳米级粒子特征的半导体化合物簇,制得以无机微孔晶体为基质的化合物半导体复合材料。这类材料具有较其它超微粒子半导体材料优越的光学、光电子学和光化学特征。在同一种沸石中,生成的化合物簇具有尺寸单一、分布均匀的优点,控制反应条件可得到单簇或超簇,从而使材料性能可调控。由诸多种类的沸石可制得尺寸和结构各异的半导体簇。这类材料在光学信息存储和光传感元件等方面有较大应用前景,因此在近10年的发展过程中引起了国际科学界的很大兴趣,正在成为新功能材料领域的前沿课题之一。本文综述其合成原理、制备方法、结构表征、性能及应用前景,并试论其近期发展趋势。     

Growth and optical properties of nanostructured ZnS:Mn films

Nanostructured ZnS:Mn films have been grown and their structure, optical properties, and photoluminescence have been studied. The nanostructured ZnS:Mn films have been grown on silicon and glass substrates via hydrochemical deposition from solution. The crystal structure and microstructure of the films have been studied by X-ray diffraction and atomic force microscopy. The band gap of the nanostructured ZnS:Mn films has been determined. The intensity of their photoluminescence bands has been shown to increase with decreasing nanoparticle size.     

Preparation of AlFe nanoparticles by mechanical alloyed technique

Small metallic particles (1-3 nm) have been obtained using mechanical alloying techniques. Analytical techniques such as scanning electron microscopy have been used for the morphological and chemical characterization of the AlFe alloyed powders. B, Ni and Ti have been explored as reinforced elements to the initial AlFe mixture. X-ray diffraction patterns and transmission electron microscopy (TEM) techniques have been employed for the structural characterization of the small metallic particles. Theoretical simulations based on molecular dynamics have been used to interpret some of the experimental structural results. Furthermore, theoretical simulations of HREM images based on the dynamical theory of electron diffraction have also been obtained and comparisons with the experimental results have been carried out. The complementary analyses determined that the produced clusters are basically AlFe alloyed nanoparticles immersed in a matrix and with multiple defected structures.     

三源真空共蒸发沉积 CuInSe_2薄膜

用三源真空共蒸发沉积 CuInSe_2。调节三源的配方及蒸发速率,控制薄膜的组分,获得了具有单相黄铜矿结构的多晶 CuInSe_2薄膜。发现适当的热处理对薄膜的成相是必需的。研究了薄膜组分、结构、光学和电学性质与工艺条件的关系。     

Diamond polycrystalline composite material and its properties

The results of experimental studies on the development of a diamond polycrystalline material to equip drill bits have been considered. Angles of wetting graphite by sintering aids Ni, Co, and alloy of them have been defined. Among the composites, which have been tested, the longest durability and the highest strength have been exhibited by the composite of the Cd-Co-34Ni formulation.     

A generic approach for vertical integration of nanowires

We report on the collective integration technology of vertically aligned nanowires (NWs). Si?and ZnO NWs have been used in order to develop a generic technological process. Both mineral and organic planarizations of the as-grown nanowires have been achieved. Chemical vapour deposition (CVD) oxides, spin on glass (SOG), and polymer have been investigated as filling materials. Polishing and/or etching of the composite structures have been set up so as to obtain a suitable morphology for the top and bottom electrical contacts. Electrical and optical characterizations of the integrated NWs have been performed. Contacts ohmicity has been demonstrated and specific contact resistances have been reported. The photoconducting properties of polymer-integrated ZnO NWs have also been investigated in the UV-visible range through collective electrical contacts. A small increase of the resistivity in the ZnO NWs under sub-bandgap illumination has been observed and discussed. A comparison of the photoluminescence (PL) spectra at 300?K of the as-grown and SOG-integrated ZnO nanowires has shown no significant impact of the integration process on the crystal quality of the NWs.     

USB Sensor Network for Industrial Applications

This paper proposes a universal serial bus (USB) solution for sensor networking. First, network architecture has been presented to have, as its primary objective, its integration with existing infrastructure. For this reason, a USB-to-Ethernet gateway has been introduced. Then, many aspects of industrial applications have been considered to realize a suitable solution. Insulation problems and low-cost implementation have been tackled. Working prototypes of each network component have been defined and realized: USB host gateway, USB insulator, and USB hub. Several commercial USB devices can be used as sensors. Finally, some experiments have been carried out: Timing performances, network activities, and power consumption have been tested.     

Exothermic synthesis of cast nickel aluminide alloys with tungsten and molybdenum carbides

Cast NiAl–Mo₂C and NiAl–WC alloys have been prepared by self-propagating high-temperature synthesis involving the reduction of starting metal oxides. Synthesis conditions have been found experimentally. The elemental and phase compositions of the alloys have been determined and their microstructure has been studied. The composites have been shown to have higher microhardness than do NiAl intermetallic alloys containing Mo and W inclusions.     

Progress in III-nitrides: Process issue and purity perspective

The growth of good quality layers of gallium nitride (GaN) as suitable for epitaxial growth is of great technological importance. Chloride vapour phase epitaxy (Cl-VPE) has been employed to grow good quality layers of GaN. The grown layers have been extensively characterized for their structural and optical properties. MOVPE grown GaN layers have been used to address process issues on device structuring and fabrication. GaN samples with different transition metal dopants have been synthesized and their usefulness as semi-magnetic materials, which are also identified as dilute magnetic semiconductors (DMS), have been evaluated. Better results have been obtained on the magnetic characteristics of GaN with ruthenium as the dopant. Nano dimensional structures of GaN have been obtained with excellent control of the growth parameters.     

迷宫密封气流激振及其动力系数的研究

本文从流体力学基本方程出发,建立起一组描述在迷宫密封腔中气流流动情况的偏微分方程组,并应用特征线方法求得了其解.同时还按不同工作条件下密封腔内的压力分布,进行了迷宫装置刚度的计算.为了从实验方面也能对迷宫气流激振形成的迷宫装置的动力特性进行研究,设计并制造了一台可以在多种条件下进行试验的试验台.通过试验,测得了在不同工作条件下各密封腔内的压力分布,从而得到了以实测为基础的迷宫装置的刚度系数.实验还结合振动频谱分析,研究了各种参数对转子系统稳定性的影响.文中将实验结果与理论分析进行了比较,两者间的相符情况是令人满意的.     

The role of alloying elements in the design of nickel-base superalloys

The constituents of nickel-base superalloys have been classified into solid solution formers, precipitate formers, carbide formers and surface stabilizers. The characteristics of solutes which would make them most suitable in each category have been specified and appropriate alloying elements have been identified. Nickel-base superalloys are hardened primarily by the precipitation of Ni₃X type compounds. The occurrence and crystallography of precipitation of various kinds of Ni₃X type precipitates have been considered. The role of substitution by alloying elements on mismatch and stability of phases has been discussed. The free electron model and the Engel-Brewer model have been applied for evaluating the stabilities of precipitates, and the role of the alloying elements in determining the stabilities of external and internal surfaces such as grain boundaries have been briefly outlined.     

Cohesive zone modelling of fracture in polybutene

Fracture properties of isotactic polybutene-1 have been investigated. Fracture tests have been conducted and relevant properties at initiation have been determined according to linear elastic fracture mechanics. Two distinct fracture mechanisms have been identified, one of them causing partial instability during crack propagation. Numerical modelling has been performed using a cohesive zone approach. In particular, the identification of suitable cohesive laws has been tried using parametric identification and two different experimental methods. Results suggest that two different cohesive laws may be needed in order to describe crack initiation and crack propagation.