石墨烯基有序介孔金属氧化物复合材料的制备及研究进展

综述了以石墨烯作为载体,利用有序介孔金属氧化物特殊的3D结构,以及两者共存产生的协同效应,开发系列新型石墨烯基有序介孔金属氧化物复合材料的最新研究进展。介绍了本课题组在有序介孔金属氧化物的可控合成、与石墨烯的有效复合以及复合材料的光电性能等方面的探索性研究。着重对石墨烯基有序介孔金属氧化物复合材料的制备方法、形成机理及其在催化、电化学、传感和能量储存等领域的最新应用进行概述,并展望了其未来的发展趋势。     

Formation of ZnO/metal composites by rapid oxidation of Zn melts

A novel ZnO-based composite material is fabricated by oxidation of Zn alloy melts, in which outward growth of the reaction products and rapid reaction kinetics are observed. Additions of Na and Bi to the Zn melts are found to be essential to increase the matrix growth rate to a practical level. Optimum reaction rates are observed for Zn-3Na-5Bi alloys oxidized at temperatures between 450 and 550°C in pure oxygen. Processing parameters, such as alloy composition and oxygen activity, also have a profound impact on the resulting microstructure and reaction kinetics. The evidences supported that the continuous outward growth of the matrix is achieved via modification of the ZnO defect structure and partial wetting of the growing oxide by the melts.     

Separation of matrix alloy and reinforcement from aluminum metal matrix composites scrap by salt flux addition

Separation of matrix alloy and reinforcements from pure Al-SiC_p composite scrap by salt flux addition has been theoretically predicted using interface free energies. Experiments performed confirm the theoretical prediction. Complete separation of matrix aluminum and reinforcement from metal matrix composites (MMCs) scrap has been achieved by addition of 2·05 wt% of equimolar mixture of NaCl-KCl salt flux with a metal and particle yield of 84 and 50%, respectively. By adding 5 wt% of NaF to equimolar mixture of NaCl-KCl, metal and particle yield improved to 91 and 73%, respectively. Reusability of both the matrix aluminum and the SiC separated from Al-SiC_p scraps has been analysed using XRD, SEM and DTA techniques. The matrix alloy separated from Al-SiC_p scraps can be used possibly as a low Si content Al-Si alloy. However, the interfacial reaction that occurred during the fabrication of the composites had degraded the SiC particles.     

Formation and relative stability of interstitial solid solutions at interfaces in metal matrix composites

On the example of Cu-C composite material the way to calculate the occupation of the interstitial positions and its temperature dependence is shown. The results obtained on the basis of non-empirical calculations indicate the preferable occupation of octahedral positions up to T1200 K. This confirms the structure of the interstitial solid solution. Within this model the influence of the alloying on the height of the diffusion barrier and on the temperature dependence of carbon diffusion in copper is calculated.     

Cast metal matrix composites

Abstract

Metal matrix composites have been available in certain forms for at least two decades, e.g. boron fibre reinforced aluminium and various dispersed phase alloys and cermets. Recently, a range of alumina and silicon carbide fibres, whiskers, and particles with diameters <20 μm have become available. The possibilities of incorporating these materials into metals to improve stiffness, wear resistance, and elevated temperature strength without incurring weight penalties have attracted the attention of design engineers in the aerospace and automobile industries. The aim of the present paper is to outline the manufacturing processes for such composites, in particular those based upon liquid metal technology, e.g. squeeze casting and spray forming. Some of the mechanical and physical properties which have been determined for these materials are described. An analysis of how matrix alloy selection may influence tensile and fracture behaviour of short fibre and particle reinforced composites is attempted.

MST/770     

Fatigue of metal matrix composites

One unidirectional and two laminated 6061-0 A-B composite plates were tested under various cyclic loading conditions. Three types of material response to cyclic loading were identified; No evidence of damage at relatively low cyclic loads, damage accumulation caused primarily by growth of long matrix cracks parallel to the fibers in off-axis layers at higher loads, and sudden localized failure of the fibers. Quantitative analysis of the results shows that the extent of internal damage, demonstrated by a reduction in axial elastic modulus, depends on the applied stress range and is independent of mean stress. The stress range at which damage first starts to appear coincides with the shakedown range of the laminate.

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Résumé On a testé sous des conditions de contrainte cyclique variable des plaques constituées d'une part par des alliages 6061-0 A-B unidirectionnels et d'autre part du même alliage composite bilaminé. On a identifié trois types de réponse du matériau aux contraintes cycliques, à savoir la non-évidence d'un dommage pour des cycles de charge à faible amplitude relative, une accumulation du dommage causé principalement par la croissance de longues fissures matricielles parallèles aux fibres dans les couches éloignées du plan médian à des contraintes plus élevées, et une fissure soudainement localisée des fibres. L'analyse quantitative des résultats montre que 1'extension du dommage interne telle qu'elle est dóntree par une réduction du module axial d'élasticité, dépend de l'amplitude des contraintes appliquées et est indéndante de la contrainte moyenne. L'amplitude de contrainte auquelle un dommage commence à apparaître coíncide avec l'amplitude de l'adaptation plastique du laminé telle qu'établie par le théorème de Melan.

     

低密度高阻尼金属/金属复合材料

采用快速凝固 /粉末冶金法制备了Al-7Fe -1 .4Mo -1 .4Si(FMS0 71 4)合金及其复合材料FMS0 71 4/xAl(x=1 0～ 2 0 )和FMS0 71 4/y(Zn-3 0Al) (y =1 0～ 2 0 )w(B) / % .运用三点弯曲法、拉伸试验和阿基米德法分别测试了其阻尼性能、拉伸性能和密度 .结果表明 :FMS0 71 4合金本身即具有较好的阻尼性能 .添加纯Al粉对其阻尼性能影响不大 ;而添加Zn-3 0Al合金粉则显著提高其阻尼性能 .FMS0 71 4合金及其复合材料的阻尼性能与拉伸强度均优于LD7CS合金 .其中 ,FMS0 71 4/ 1 5 (Zn-3 0Al)具有最佳的综合性能 ,在航空和航天领域显示出良好的应用前景 .     

Hot isostatic pressing of metal reinforced metal matrix composites

Metal reinforced Metal Matrix Composites (MMMCs) made by combining an aluminium alloy matrix with stainless steel reinforcing wires are potentially cheaper and tougher than continuous fibre ceramic reinforced Metal Matrix Composites (MMCs). Although they do not give as great enhancements in stiffness and strength, worthwhile gains are achieved. Such MMMCs can be produced by Hot Isostatic Pressing (HIPping), which reduces interfacial reactions in comparison with liquid metal routes. Here, stainless steel (316L) and commercial purity aluminium wires were used to make bundles which were inserted into mild steel cans for HIPping at 525 °C/120 min/100 MPa. Some stainless steel wires were pre-coated with A17Si, to examine the effect of coatings on mechanical properties. Specimens were evaluated in terms of their tensile and fatigue properties. During HIPping, cans collapsed anisotropically to give different cross-section shapes, and for larger diameter cans, there was also some longitudinal twisting. Wires tended to be better aligned after HIPping in the smaller diameter cans, which produced material having higher modulus and UTS. Higher volume fractions of reinforcement tend to give better fatigue properties. Composites with coated stainless steel wires gave higher composite elongation to failure than uncoated wires. Both uncoated and coated wires failed by fatigue during fatigue testing of the composite. This contrasts with ceramic reinforced MMCs where the fibres fracture at weak points and then pull out of the matrix.     

Design with metal matrix composites

Abstract

Applications for metal matrix composites (MMCs) have not emerged at the rate needed to justify the development costs. A reason for this may be that material developments have not been adequately linked to identified commercial needs. It is certainly true that some of the expectations raised about the potential offered by MMCs have been misguided. As the MMC business contracts, there is an ever greater need for a systematic method of linking material properties to the needs of engineering designers. This paper presents a methodology for evaluating materials in design, with the aim of linking MMCs to applications. The methodology has two main components: first, the use of performance indices and materials selection charts for specific design goals, to compare existing MMCs with competing materials; and secondly, the conceptual design of new MMC systems guided by those design goals. A selection of case studies illustrates that in mechanical applications the gains in using MMCs are frequently marginal, whereas in design for thermal management and vibration control, the materials can show very substantial improvements in performance. The methodology is general, and could be applied to other material systems.

MST/3094     

Spot welding of metal laminated composites

Composite materials of steel sheets joined by interlayers of zinc or lead- tin, show very good impact and corrosion resistance properties. Resistance spot-weld characteristics of these composite materials made of steel sheets and non-ferrous metals have been tested. Spot welds of composites with both zinc and lead- tin interlayers present good behaviour in peeling tests. Shear tests of the welds also show very high strength, probably as a consequence of simultaneous brazing because of the alloyed layer of non-ferrous material around the weld spot. This good welding behaviour enhances the possibilities of application of this composite.     

金属基复合材料的高应变速率超塑性

综述并评论了金属基复合材料的高应变速率超塑变形机制，描述了金属基复合材料在高应变速率超塑变形中的一些理化现象，说明了变形过程中的各种影响因素，总结了具有高应变速率超塑性能的金属基复合材料及其性能，并指出了在金属基复合材料的高应变速率超塑性研究方面的不足。     

Fabrication of CuSiC metal matrix composites

A CuSiC MMC heatspreader will offer high thermal conductivity between 250 and 325 W/mK and corresponding adjustable thermal expansion coefficient between 8.0 and 12.5 ppm/°C. The primary challenge of CuSiC manufacture was to prevent reaction between copper and silicon carbide during high temperature densification, which dramatically degraded the thermal conductivity. In this study, the key issue addressed was the Si attack of Cu at the temperatures necessary for CuSiC fabrication (850 to 1200°C). Decomposition of SiC in contact with copper will dissolve Si in Cu causing a dramatic decrease of Cu thermal conductivity. This diffusion of Si into Cu can be prevented by the application of reliable barrier layers to diminish mass transport through the diffusion path and thereby minimizing the chemical interaction. A reliable barrier coating was identified and used to fabricate the CuSiC composites. The CuSiC composites were then characterized by SEM, TEM, XRD and XPS. Chemical analysis and thermal conductivity by laser flash diffusivity measurement illustrated the effectiveness of the barriers. A CuSiC composite having thermal conductivity of 322.9 W/m-K was successfully fabricated.     

Specific heat of superconductor-normal metal composites

The specific heat of Th-Nb composites has been measured to determine the extent to which a dense array of Nb rods will enhance the superconducting energy gap of the surrounding Th matrix at temperatures well belowT _c of the Th. A directional solidification technique has been used to prepare an acicular composite having a triangular array of 500-nm-diameter Nb rods in a Th matrix with a center-to-center spacing of 1500 nm. At low temperatures, where both metals are superconducting, the specific heat indicates that the Th matrix has an energy gap about 10% larger than bulk Th, so there is some enhancement by the Nb rods. BetweenT _c of Nb andT _c of Th there is clear evidence of an induced energy gap in the Th, but as yet there is no theory for the specific heat in this regime. A field as small as 20 mT will quench all evidence of proximity-induced superconductivity in the Th, indicating a strong field dependence of the Cooper pair decay lengthK _N ^–1 .This work has been authored by a contractor of the U.S. Government under contract No. W-7405-eng-82. Accordingly, the U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so for U.S. Government purposes.Operated for the U.S. Department of Energy by Iowa State University under contract No. W-7405-Eng-82. This research was supported by the Director for Energy Research, Office of Basic Energy Sciences, WPAS-KC-02-02-02.     

Molten salt syntheses of alkali metal titanates

Submicrometer dispersions of rod-like alkali metal titanates were prepared by the flux method, from the reaction of TiOSO₄ or TiO₂ precursors in molten alkali metal nitrates, doped with carbonates or hydroxides. Mono-, di-, tetra-, and hexatitanates are formed as a function of the precursor nature and the melt composition. As a rule, in these syntheses poorly crystalline or amorphous solids are obtained, showing the structure of polytitanates on the nanoscopic level. Lamellar potassium hexatitanate can be exchanged by action of a diluted acid, leading to protonic form, free from the alkali metal but retaining initial morphology. Reactivity of TiOSO₄ and TiO₂ in molten alkali metal nitrates and their mixtures with the corresponding carbonates was studied by mass spectrometry of the gases evolved during heating of the reaction mixtures. For both pure and doped nitrates it changes in the expected row Li>Na>K, following the melts oxobasicity sequence.     

Synthesis of ordered mesostructured polymer-organosilica composites by the triconstituent co-assembly method

Ordered mesoporous polymer-organosilica composites have been synthesized through a triconstituent co-assembly strategy. These composites have ordered 2-D hexagonal mesostructures (space group p6m) with uniform pore size (6.2-7.3 nm), suitable surface areas (619-794 m² g⁻¹) and pore volumes (0.61-0.88 cm³ g⁻¹). With increasing BTSE (1,2-bis(triethoxysilyl)ethane) content, the surface area and pore volume reduce. The composites have homogeneous interpenetrating frameworks, in which both polymer and organosilica synergistically support the ordered mesostructure. The hybrid materials exhibit good adsorption capacities of benzene (up to 2.0 mmol g⁻¹), suggesting their use as a potential adsorbent for removal of volatile organic compounds.     

Dislocation-induced damping in metal matrix composites

The damping response of crystalline metals and alloys is generally associated with the presence of defects in the crystal lattice. The disturbance of these defects, usually in response to an applied cyclic load, dissipates energy, a mechanism known as internal friction. The various defects commonly found in crystalline materials include point defects (e.g. vacancies), line defects (e.g. dislocations), surface defects (e.g. grain boundaries) and volume defects (e.g. inclusions). Among these, dislocations are noteworthy because they play a critical role, not only in the damping response of crystalline materials, but also in the overall mechanical behaviour of the materials. Among the various structural materials actively being developed, metal matrix composites (MMCs) have received considerable attention as a result of their potential to combine reinforcement properties of strength and environmental resistance, with matrix properties of ductility and toughness. Of interest is the generally observed phenomenon that MMCs exhibit unusually high concentrations of dislocations, an observation typically attributed to the difference in coefficient of thermal expansion between matrix and reinforcement. The objectives of the present paper are to provide an overview of the sources of dislocation generation in MMCs, and to provide insight into the effects that dislocations have on the damping response of MMCs. The presence of dislocations in MMCs is highlighted on the basis of transmission electron microscopy studies, and the dislocation damping mechanisms are discussed in light of the Granato-Lücke theory.     

泡沫金属复合材料的研究进展EI北大核心CSCD

泡沫金属复合材料是一种轻质复合材料,具有低密度、高强度、高屏蔽性能、高阻尼性能等特性,其在航空航天、钻井隔水管浮筒、人工骨等多个领域具有广泛的应用前景,备受人们关注。本文通过对现有文献的研究,介绍了泡沫金属复合材料的制备方法,深入分析泡沫金属复合材料的显微结构对其性能的影响,综述了材料的力学性能、阻尼性能、屏蔽性能、隔热等性能和机制的进展以及其在相关领域的应用,为未来泡沫金属复合材料的开发提供一定的理论依据,并对其新制备工艺、建模研究、夹芯结构以及高性能泡沫空心球的制备等研究方向进行展望。