高性能β″-Al2O3陶瓷压型粉料的制备

本工作研究了β″－Ａｌ２Ｏ３陶瓷压人料的化学组成,制备方法对其密度１电导及显微结构的影响。     

不同重力环境对AlN-玻璃复相陶瓷显微结构的影响

采用SHS化学炉为热源,在抛物线飞行飞机上进行了一系列不同重力环境下的A1N－玻璃复相材料的液相烧结,研究了烧结过程中,不同重力水平对材料显微结构和扩散行为的影响。研究结果表明：超重力条件下物相会发生偏析,而策重力条件下,物质扩散均匀,可促进晶粒的正常发育,有利于材料显微结构的均匀性。     

Mo-MgO金属陶瓷的性能与应用

我国首创的M。一MgO金属陶瓷问世以来,使得高温熔体连续测温有了很大进展。索提高金属陶瓷保护管使用寿命的途径,成、电阻率等主要物理性能、以及对金属为探了抗震性能,对金属陶瓷进行了性能测试。分别测定了化学组、炉渣熔体的润湿性,观察了显微结构特点,探讨较系统地研究了化学稳定性,扼要地介绍了应用情况。     

C／C复合材料的显微结构及其与工艺、性能的关系

对化学气相渗透（CVI）C／C复合材料在偏振光下的显微结构（偏光显微结构）类型、结构的形貌特征及对应炭的基本物理性能、材料的制备工艺参数－结构－性能之间的关系进行了综述。C／C复合材料具有三种基本偏光显微结构,即RL、SL和ISO。这三种基本偏光结构的炭对应于不同的形貌特征,可从消光十字形、旋光性、光学反射性、生长特征、表面织构、择优取向性和环形裂纹等特征将其分辨出来。工艺参数对沉积炭偏光显微结构的影响没有一成不变的规律可循,影响因素除了温度、压力、气体成分、气体流速外,还与炉子的几何尺寸及试样的堆积尺寸有关,对不同的CVI体系,都应当摸索出一套适合其运行的最佳工艺参数。C／C复合材料的偏光显微结构与材料的性能有着密切的联系,不同的结构下,材料的物理性能、力学性能和热性能都表现出明显的差异。通过归纳与分析,获得了对C／C复合材料偏光显微结构全面、系统的认识,明确了它在C／C复合材料研究中的重要性,为制备具有单一、均匀偏光显微结构及所需性能的C／C复合材料指明了方向。     

高性能β"-Al2O3陶瓷压型粉料的制备

本工作研究了β"-Al2O3陶瓷压型粉料的化学组成,制备方法对其密度、电导及显微结构的影响. 与水基料浆喷雾干燥相比,酒精基料浆稳定性好,易于调制,其喷雾干燥粉料收获率高,化学组成均匀, 耐大气湿气性好,粉体颗粒可在较低压力下被压碎,生坯压实密度较高. 采用Li2O-Al2O3和Na2O-Al2O3混合物的高温煅烧产物为组元, 配成化学组成为0.69～0.75wt%Li2O, 8.85～9.10wt%Na2O,其余为Al2O3的酒精基料浆喷雾干燥粉料, 可获得密度、电导和显微结构俱佳的高性能β"-Al2O3陶瓷.     

溶胶-凝胶法制备金属基铝硅酸盐陶瓷涂层

采用溶胶－凝胶法,在不锈钢基体上制备铝硅酸盐陶瓷涂层,对涂层微观结构进行了分析,研究了涂层化学组成、涂最度对抗热震性、抗氧化性的影响,结果表明：涂氢化学组成为３Ａｌ２Ｏ３．２ＳｉＯ２、厚度２μｍ时,制备的涂层材料与基体结合紧密、显微结构致密均匀,有良好的抗热震、抗氧化性能。     

自加热化学气相法制备连续碳纤维增强碳化硅复合材料

通过自加热化学气相渗积法制备了Cf/SiC复合材料，对其力学性能进行了测试与分析，运用SEM对复合材料显微结构和断口形貌进行了分析，研究表明：自加热化学气相渗积法具有较快的渗积速率；气体流量的适度增加可改善复合材料的性能；碳涂层的厚度对复合材料的力学性能有较大的影响，适合的涂层厚度在0.35～0.55μm之间。     

多孔陶瓷的显微结构与性能

综述了多孔陶瓷的显微结构及其性能.多孔陶瓷的力学性能、热性能和电性能等均依赖于固体在孔壁和孔棱的分布方式,其微观组织结构直接影响着多孔陶瓷的物理及化学性能,进而影响到它的应用场合.通过研究多孔陶瓷的显微结构,可以改善其制造工艺、优化结构参数,使其更好地在化工、能源、环保等多个领域得到广泛应用.     

碳纤维表面处理对生物骨水泥结合性能的影响

以碳纤维为增强材料对具有较高孔隙率的骨水泥进行补强,利用FTIR 、SEM和EDS对骨水泥的显微结构和碳纤维表面晶体组分进行了观察和分析.试验结果表明,硝酸氧化处理提高了骨水泥对碳纤维的浸润性和碳纤维的表面化学活性,增加了界面粘结性能,改善了骨水泥和碳纤维之间的界面结合.     

合成工艺对ZnVSb基压敏陶瓷性能的影响

研究了三种合成工艺对ZnVSb系压敏电阻烧结、显微结构和性能的影响。通过对陶瓷密度、显微结构及电学特性的检测、分析发现：化学计量比相同情况下，与V2O5＋Sb2O3预热处理工艺相比，以SbVO4取代Sb2O3合成工艺及传统氧化物合成工艺逐步加剧了尖晶石相在材料中的形成和掺杂元素在晶界的偏聚；导致材料内部晶界势垒逐渐升高，材料的非线性系数及压敏电压逐渐上升。研究结果为ZVSb系压敏电阻材料的设计、制备提供了新的思路。     

Surface alloying of pure iron by molybdenum and tin by a continuous wave CO2 laser

It is now well established that considerable improvement in the mechanical/chemical properties of near surface regions of materials can be achieved by the process of laser surface alloying. The change in chemistry at the surface is attained through the process of melting and mixing of a predeposited coating and a thin layer of the substrate. Rapid solidification of this molten region at the surface then results in the development of very interesting microstructural features. In the present work, an attempt was made to surface alloy pure iron by molybdenum and/or tin by using a continuous wave CO₂ laser. Morphology of the resulting microstructural features was examined by optical as well as scanning electron microscopy and the compositional details were determined using an electron probe microanalyser. Microhardness measurements were carried out as a function of depth from the laser-treated surface. This paper discusses the results of these investigations and delineates the roles of the various parameters on the chemistry and microstructure of the surface alloys formed as a result of laser treatment.     

Microstructure-property relationships of GRP

Fibre-reinforced composite materials are being used increasingly in critical applications, when the primary function of the material is to support loads, but very high safety margins are commonly used for such applications. Such large safety margins arise from the uncertainties regarding the mechanical behaviour of composite materials. The authors believe that the lack of microstructural definition of composite materials may make a substantial contribution to these uncertainties. In this initial study, relationships are sought between microstructure and properties of a model microstructure. The methods used are applicable to a very wide range of composite materials.     

Effect of the microstructure of titanium alloys on the fatigue strength characteristics

The fatigue test results and the mechanical characteristics in static tension are obtained for specimens of titanium alloys belonging to the known classes of materials with a reference globular or bimodal microstructure and the so-called fine-grained β-transformed microstructure provided by the rapid heat treatment technique. The microstructure of the materials under study is analyzed. The microstructural parameters responsible for the fatigue strength of particular material have been found. The comparison is made between the fatigue limits obtained experimentally and calculated using the models previously developed by one of the authors.     

Image analysis and modeling of spherical and channel microstructures of fuel-cell materials

The development of novel fuel-cell materials demands accurate and flexible microstructure characterization techniques. Conventional electron microscopy-based microstructural morphology analysis is carried out through the conceptual interpretation of transmission electron microscope images. With this method, only qualitative information on material morphologies can usually be obtained. This paper presents a digital image analysis system that deals with the automatic measurement and quantitative characterization of the microstructural morphologies of polymer electrolyte membrane fuel-cell materials. In this approach, two types of essential microstructural morphologies (spheral particles and interconnected graft channels) are modeled based on statistical geometry theory, and the statistical analysis schemes of the microstructural morphologies are designed and applied to the characterization of the phase-separated microstructures in fuel-cell components such as solid electrolyte ionomers, catalyst layers, and gas diffusion layers. Experimental results on real fuel-cell materials specimens demonstrate the effectiveness of the method.     

2D Real Microstructure Simulation Method for Metal Materials

Strength of Materials - The method of constructing a 2D simulation model based on the real microstructure is developed to simulate the microstructural evolution of materials. Microstructure...     

The significance of carbon nanotubes on styrene butadiene rubber (SBR) and SBR modified mortar

A New approach is introduced to incorporate multi-walled carbon nanotubes (MWCNTs) in cementitious materials. The MWCNTs are dispersed in styrene butadiene rubber (SBR) matrix before mixing the matrix with cement. Surfactants have been successfully applied to enhance the dispersion and functionalization of MWCNTs in SBR. The significance of using this MWCNTs–SBR nanocomposite on the mechanical characteristics including compressive and tensile strengths and microstructural features of latex modified mortar (LMM) were examined. Subsequently, the significance of the functionalized MWCNTs on surface chemistry, microstructure and thermal stability of SBR were characterized. MWCNTs were found to be a useful additive for enhancing the mechanical response and thermal stability of SBR. MWCNTs–SBR nanocomposite was observed to be able to bridge micro-cracks in the LMM which helped enhancing its mechanical properties. The ability of MWCNTs to enhance the mechanical response of SBR polymer matrix might be attributed to chemical bond that functionalized MWCNTs can establish with the SBR polymer matrix. The enhanced MWCNTs–SBR nanocomposite gave rise to improved microstructural features of the LMM. Microstructural investigations showed MWCNTs were well dispersed in and bonded to the SBR matrix.     

Microstructural design for thermal creep and radiation damage resistance of titanium aluminide alloys for high-temperature nuclear structural applications

Microstructure plays an important role in strengthening of metallic materials. Various microstructures can be developed in titanium aluminide (TiAl) alloys, which can enable different combinations of properties for various extreme environments in advanced nuclear systems. In the present paper the mechanisms for microstructural strengthening and the effects of various microstructural features on thermal creep and radiation damage resistance of TiAl alloys are reviewed and compared. On the basis of the results, the evidence-based optimum microstructure for the best combination of thermal creep and radiation damage resistance of TiAl alloys is proposed. The heat treatment processes for manufacturing the optimal microstructure are also discussed.     

Microstructural modeling in f.c.c. crystalline materials in a unified dislocation-density framework

A unified physically based microstructural representation of f.c.c. crystalline materials, has been developed such that evolving microstructural behavior at different physical scales can be accurately predicted. This microstructural framework is based on coupling a multiple-slip crystal plasticity formulation to three distinct dislocation densities, which pertain to statistically stored dislocations, geometrically necessary dislocations, and grain boundary dislocations. This interrelated dislocation-density formulation is then used with specialized finite-element modeling techniques to predict the evolving heterogeneous microstructure and the localized phenomena that can contribute to failure initiation as a function of inelastic deformation.     

Directionally solidified eutectic ceramic oxides

The processing, structure and properties (mechanical and functional) of directionally solidified eutectic ceramic oxides are reviewed with particular attention to the developments in the last 15 years. The article analyzes in detail the control of the microstructure from the processing variables, the recently gained knowledge on their microstructure (crystallographic orientation, interface structure, residual stresses, etc.), the microstructural and chemical stability at high temperature, the relationship between the eutectic microstructure and the mechanical properties, and the potential of these materials as patterning substrates for thin films, templates to manufacture new composite materials, photonic materials and electroceramics. The review highlights the achievements obtained to date, the current limitations and the necessary breakthroughs.     

Three-dimensional reconstruction of a solid-oxide fuel-cell anode

The drive towards increased energy efficiency and reduced air pollution has led to accelerated worldwide development of fuel cells. As the performance and cost of fuel cells have improved, the materials comprising them have become increasingly sophisticated, both in composition and microstructure. In particular, state-of-the-art fuel-cell electrodes typically have a complex micro/nano-structure involving interconnected electronically and ionically conducting phases, gas-phase porosity, and catalytically active surfaces. Determining this microstructure is a critical, yet usually missing, link between materials properties/processing and electrode performance. Current methods of microstructural analysis, such as scanning electron microscopy, only provide two-dimensional anecdotes of the microstructure, and thus limited information about how regions are interconnected in three-dimensional space. Here we demonstrate the use of dual-beam focused ion beam-scanning electron microscopy to make a complete three-dimensional reconstruction of a solid-oxide fuel-cell electrode. We use this data to calculate critical microstructural features such as volume fractions and surface areas of specific phases, three-phase boundary length, and the connectivity and tortuosity of specific subphases.