碳纳米管-氧化铝陶瓷复合材料的研究进展

碳纳米管优异的力学性能以及纳米级尺寸,与工程材料复合可起到强化作用.采用碳纳米管作为增强相来改善氧化铝陶瓷材料的脆性成为一个重要的研究领域.本文综述了碳纳米管-氧化铝陶瓷复合材料的制备工艺,碳纳米管-氧化铝陶瓷复合材料的强韧化效果及机理,以及当前研究的焦点和存在的问题,材料的界面结合以及外场力传递效应是值得关注的课题,并对该领域工作做了一些讨论和展望.     

β″氧化铝与铝及铝基复合材料场致扩散连接机理的研究

以β″氧化铝(β″-Al2O3)与L2及铝基复合材料[SiC(p)/Al]为试验对象,采用SEM,EDX和XRD等手段分析了电解质陶瓷与金属基复合材料在场致扩散连接(field_assis ted diffusion bonding)条件下的接合机理及工艺特征.研究认为, 在实验条件下电解质陶瓷与金属或金属基复合材料的连接性较好;连接区为金属-过渡区-氧化铝结构模型, 电场作用下的离子导电及扩散是过渡层形成的基本条件;过渡区的氧化物形成及化合反应接合机制是形成连接的主要原因;电压、温度及材料的离子导电性是影响连接过程的主要因素.     

溶胶-凝胶法制备Al_2O_3f/Al_2O_3复合材料及其性能研究

本文采用化学气相渗透法(CVI)在三维氧化铝纤维预制体上沉积热解碳(PyC)界面层,通过溶胶-凝胶法制备氧化铝纤维/PyC/氧化铝基体复合材料和无界面复合材料。通过三点弯曲实验分析其力学性能,扫描电子显微镜观察其断口微观结构。结果表明,当热解碳界面层厚度分别为0.6μm和0.8μm时,复合材料所对应的弯曲强度分别为231.3 MPa和158.2 MPa,与无界面复合材料弯曲强度55.8 MPa相比,力学性能分别提高314.5%和183.5%。通过微观结构分析发现利用热解碳界面可充分发挥连续纤维拨出、界面脱粘和裂纹偏转等增韧机制,实现材料脆韧转变。     

三维网络氧化铝/钢复合材料的制备及性能

采用真空消失模铸造技术,将钢液浸渗到表面化学气相沉积了金属镍涂层的氧化铝泡沫陶瓷中制备三维网络氧化铝/钢复合材料。研究复合材料的结构、抗弯强度及磨粒磨损性能。结果表明,镍涂层可使钢液有效浸渗到陶瓷骨架中,成功制备出界面结合良好的三维网络氧化铝/钢复合材料。复合材料中陶瓷/钢界面为非反应型界面,断裂过程中,裂纹沿界面扩展,复合材料的抗弯强度随陶瓷相体积分数的增加而降低。复合材料的磨损机制为以钢被切削、陶瓷断裂–脱落为特征。随陶瓷相体积分数的增加,复合材料的体积磨损量降低。     

金属颗粒增韧氧化铝陶瓷研究现状

概述了金属颗粒增韧氧化铝陶瓷的研究进展,对氧化铝/金属复合材料的研究现状、增韧机理及制备方法进行了介绍,并对氧化铝/金属复合材料的主要发展方向进行了分析预测。     

“非汉字符号”氧化铝与铝及铝基复合材料场致扩散连接机理的研究

以 β″氧化铝 (β″-Al2 O3)与L2及铝基复合材料 [SiC(p) /Al]为试验对象 ,采用SEM ,EDX和XRD等手段分析了电解质陶瓷与金属基复合材料在场致扩散连接 (field_assisteddiffusionbonding)条件下的接合机理及工艺特征。研究认为 ,在实验条件下电解质陶瓷与金属或金属基复合材料的连接性较好 ;连接区为金属 -过渡区 -氧化铝结构模型 ,电场作用下的离子导电及扩散是过渡层形成的基本条件 ;过渡区的氧化物形成及化合反应接合机制是形成连接的主要原因 ;电压、温度及材料的离子导电性是影响连接过程的主要因素。     

金属陶瓷复合材料的电沉积

通过对金刚石、氧化铝、碳化硅等陶瓷材料与镍或铜锡合金共沉积的研究,证实了溶液中陶瓷微粒的有效表面电荷密度和电极与溶液界面间场强是影响金属陶瓷复合材料电沉积的关键性因素.镀层中金属与陶瓷微粒之间,无新相生成,不存在明显的化学作用.实验结果表明,电化学理论能够合理地解释金属陶瓷电镀层的形成机理.     

ZrO2和Ni复合掺杂对Al2O3陶瓷结构及性能的影响

利用非均相沉淀包覆-热还原工艺制备粒径分布均匀、表面光滑的球形Al2O3/ZrO2/Ni,Al2O3/Ni,Al2O3/ZrO2复合结构粉体,再经真空热压烧结得到相应的复合陶瓷.通过X射线衍射和扫描电镜对前躯体、热还原粉体及烧结陶瓷的成分及结构进行了表征,并对陶瓷的力学性能、介电常数进行了检测和分析.实验结果表明:金属Ni的引入抑制了Al2O3的致密化,细化了晶粒,强化了氧化铝晶界,使氧化铝发生穿晶断裂而起到增韧效果;ZrO2对Al2O3陶瓷致密化及细化晶粒作用不明显,但通过相变增韧或形成弱界面起到了较好的增韧作用;Al2O3/ZrO2/Ni复合材料的断裂韧性增加值并未高于Al2O3/Ni和Al2O3/ZrO2 2种复合材料断裂韧性增加值之和,但增强了空间电荷的极化,使复合材料具有较高的介电常数.     

SiC/金属界面固相反应与控制的研究进展

SiC／金属界面固相反应的研究是材料科学领域内一个极重要的理论研究课题。SiC／金属界面固相反应及界面状态决定着SiC／金属复合材料、SiC／金属复合构件、SiC／金属固相扩散焊接件的力学性能和使用性能。对SiC／金属界面固相反应进行了分类，就SiC／金属界面固相反应研究在反应热力学，反应区的组成、结构和性能，反应动力学及反应微观机制等方面取得的成果进行了综述。并归纳总结了几种类型的SiC／金属界面固相反应控制的方法。     

反应熔渗C_f/(ZrB_2)-ZrC-SiC超高温陶瓷基复合材料的优化制备及性能

受熔渗动力学控制,常规反应熔渗制备的超高温陶瓷基复合材料易存在纤维/界面损伤,基体大尺寸金属残留等问题,严重影响复合材料性能。近年来,中国科学院上海硅酸盐研究所建立了基于溶胶-凝胶预成型体孔隙结构设计的超高温陶瓷基复合材料反应熔渗新方法,揭示了预成型体孔隙结构对复合材料基体分布、界面损伤及性能的影响规律;发现反应熔渗超高温陶瓷基复合材料界面锆元素聚集现象,并首次提出反应-类熔融界面损伤机制;提出准连续ZrC界面保护结构设计思路,有效缓解了反应熔渗纤维/界面损伤,实现反应熔渗C_f/(ZrB_2)-ZrCSiC超高温陶瓷基复合材料性能大幅提升。     

氧化物纤维/氧化物陶瓷基复合材料研究概述

氧化物纤维，氧化物陶瓷基复合材料可以在高温氧化环境下长时间工作，是最有发展潜力的高温结构陶瓷材料之一。决定氧化物纤维，氧化物陶瓷基复合材料性能最主要的2个因素是氧化物纤维的性能和界面材料的组成与结构。笔者介绍了氧化物纤维和界面材料的发展，以及界面材料涂覆方法，并探讨了氧化物纤维，氧化物陶瓷基复合材料的发展趋势。     

Examining chemical structure at the interface between a polymer binder and a pharmaceutical crystal with neutron reflectometry

The mechanical properties of many composites are determined in part by the chemical structure and bonding at the interface between constituents in the microstructure. The study of these interfaces in molecular crystal - polymer composites is difficult using traditional techniques such as electron microscopy or X-ray scattering because of weak or detrimental interactions between the probe and materials. Here, the interface between acetaminophen and a poly(ester urethane) copolymer is analyzed using ellipsometry, infrared spectroscopy, and neutron reflectometry. These materials were chosen for their relevance to pharmaceutical tablets and plastic-bonded explosives. The acetaminophen was shown to dissolve into the polymer coating and creates an interphase region between the two materials; this mixing is almost certainly produced by typical formulation conditions, and likely affects mechanical response of the composite. Additionally, reflectometry shows that plasticizing the polymer alters this interphase region. These techniques can be applied to similar composites to reveal the relation between formulation conditions, constituent interface microstructure characteristics, and bulk mechanical response.     

纤维增强热塑树脂基复合材料界面问题

界面在高分子复合材料中占有很大比例,界面相互作用力的强弱决定着高分子复合材料的性能和应用,因此高分子复合材料的界面改性研究有着十分重要的意义。本文对树脂基复合材料中的结晶型热塑树脂复合材料界面和非结晶型热塑树脂复合材料界面问题进行了讨论和总结。     

纤维增强陶瓷基复合材料概述

连续纤维增强陶瓷基复合材料是最有前途的高温结构材料之一,以其优异的高韧性、高强度得到世界各国的高度重视。综述了纤维增韧陶瓷基复合材料的选材原则、主要的增韧机理、制备方法以及目前主要的界面改性方法。得到以下结论：纤维的选择必须满足工作环境的要求,纤维与基体之间要在热力学上相匹配;主要的增韧机理为载荷转移、微裂纹增韧、裂纹偏转、纤维脱粘和纤维拔出;复合材料的主要制备方法是热压法、CVI法和聚合物浸渍裂解法;目前最有效的界面改性方法是纤维表面涂层。用氧化物纤维作为增韧体,研究更加简单适用于大规模生产的制备方法,研究更加简单的涂层工艺是今后研究纤维增强陶瓷基复合材料的重点。     

Interface stability behaviors of methanol‐melamine‐formaldehyde shell microPCMs/epoxy matrix composites

Microcapsules containing phase change materials (microPCMs) have been widely applied in smart temperature‐controlling materials. Interface stability plays a key role in these microPCMs/matrix composites. The aim of this study was to investigate the interface stability behaviors of methanol‐melamine‐formaldehyde (MMF) shell microPCMs containing paraffin/epoxy matrix composites. MMF prepolymer can be applied to fabricated microcapsules with smooth shells. The average diameter of the microPCMs could be controlled in the range of 5–45 μm by stirring speed of 500–6,000 r min⁻¹. From the SEM morphologies of the interphase between the microPCMs and the epoxy‐matrix, it is concluded that the interaction may be enhanced by MMF graft structure due to the increasing of molecular interaction in the interface. During a repeated heat‐transmission process, not only the repeated‐times of thermal absorbing‐releasing process will damage the interface bonding, but also higher thermal conductive speed will make the interface bearing more debonding stress. Large microPCMs in matrix may supply better interface stability. Moreover, the numerical and experimental results are consistent to obtain a clear insight into the rule of interface debonding for microPCMs/matrix composites that the interface perfection can be enhanced by increasing the thickness of interphase. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Processing/structure/property relationships for artificial wood made from stretched PP/wood‐fiber composites

This article presents the processing/structure/property relationships for artificial wood made from stretched PP/wood‐fiber (WF) composites that have required strength and density. The die drawing of PP/WF composites causes a unidirectional orientation of the polymer molecules and enhances the mechanical properties significantly along the stretched direction. The drawing of the composites also lowers the density of artificial wood by generating voids at the WF and polymer matrix interface. The critical processing and materials parameters are identified. The effects of these parameters on the structure and the properties are also investigated. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers     

秸秆纤维增强热塑性树脂基复合材料界面改性研究新进展

秸秆纤维增强热塑性树脂基复合材料是一种用途广泛的新型环保性材料。复合材料的界面相容性会直接影响复合材料的性能,界面改性技术的研究成为近年来研究的热点。本文综述了国内外对秸秆纤维增强热塑性树脂基复合材料界面改性技术的研究现状和新进展,叙述了对于秸秆纤维的几种典型表面处理方法的研究进展;重点分析了等离子体处理和生物酶处理这两种新型处理方法在秸秆表面预处理中的应用情况,并着重阐述了以马来酸酐接枝聚烯烃为主的界面相容剂和以硅烷、钛酸酯为主的低分子量偶联剂对复合材料界面改性效果的影响。此外,论文简要分析了秸秆/树脂复合材料界面改性技术的发展趋势,指出深入研究针对秸秆纤维的复合处理方法以及开发高效、环保和高性价比的界面改性剂是未来进一步改善秸秆/树脂复合材料应用性能的关键。     

A positron annihilation spectroscopy study of carbon-epoxy composites

Many positron annihilation spectroscopy (PAS) studies have been carried out during the last several years for characterizing various polymeric materials. In this work, the PAS technique is used to investigate some positron annihilation characteristics of the combination of carbon fibers with epoxy polymers to form carbon-epoxy composites. These composites are receiving wide and increasing application in industrial markets where light-weight materials with high strength and excellent fatigue characteristics are required. We have found that PAS is capable of detecting different concentrations of carbon fiber in these composites and a relationship is shown to exist between fiber fractions found by PAS and apparent volume and weight fractions found by density measurements. Positron annihilation centers have also been found that we believe were created at the carbon-epoxy interface when the composite was prepared. Characterization of this interface is important for the development of composites with improved mechanical properties.     

Review on Shielding Mechanism and Structural Design of Electromagnetic Interference Shielding Composites

Conductive polymer composites (CPCs) for electromagnetic interference shielding have received significant attention and shown rapid development. According to the electromagnetic wave interface conduction theory of Schelkunoff, excellent conductive performance and perfect conductive network structure are prerequisites for high shielding efficiency of electromagnetic interference shielding composites. Effective multiple interface reflection absorption, dielectric loss, and hysteresis loss characteristics of the materials are crucial for realizing the regulation of the electromagnetic interference shielding performance of CPCs. Therefore, the structural design of conductive and magnetic network for CPCs is crucial for achieving high shielding performance. In this study, it is established that an electromagnetic shielding composite with a uniform structure is widely used because of its simple preparation process, but its inefficient conductive network causes a high percolation threshold. The inefficiency can be solved by designing a composite structure and improving the efficiency of the conductive network. Currently, common structural designs include segregated structural, layered structural, and foam structural designs. These structural designs effectively solve the problem of high percolation threshold of CPCs and coordinate the contradiction between the performance of electromagnetic interference shielding and other advantages.     

Fabrication and Characteristic of Nextel 720 Fiber‐Reinforced Silicon Nitride Matrix Composites by Chemical Vapor Infiltration Process

Most current processes for fiber‐reinforced silicon nitride composites are conducted at very high temperature, which is not possible to use oxide fiber as reinforcement. Here, low‐temperature process of chemical vapor infiltration (CVI) was utilized to fabricate Nextel 720 oxide fiber tow‐reinforced silicon nitride matrix composite with PyC as interphase. The tensile strength was analyzed by Weibull distribution. The microstructure showed that there were two types of interface bonding. The strong interface bonding determined the unexpected low strength of the composites. This indicated that the suitable interface design is the urgent issue for oxide fiber‐reinforced silicon nitride composite by CVI.