镍铁氧体/聚苯胺复合材料的制备及其性能

采用超声场下原位聚合法制备镍铁氧体/聚苯胺复合材料,并采用x射线衍射仪(XRD)和HP8510网络分析仪研究其结构和电磁性能.结果表明:十二烷基苯磺酸(DBSA)掺杂后的聚苯胺是部分结晶的,镍铁氧体与聚苯胺分子链之间存在某些相瓦作用;与聚苯胺相比,镍铁氧体/聚苯胺复合材料的介电损耗角正切值tanδ<,ε>与磁损耗角正切值tanδ<,m>都增大;镍铁氧体含量为5%和15%(质量分数)的复合材料分别具有最大的tanδ<,ε>暝值和最大tanδ<,m>值;镍铁氧体含量为15%的试样在8～18 GHz范围内综合吸波性能最好,具有最大衰减-23.4 dB,-8 dB带宽为5.73 GHz.     

The mechanical properties of nickel oxide and their relationship to the morphology of thick oxide scales formed on nickel

The oxidation of metals that form P-type semiconducting oxide scales, such as NiO on nickel and CoO on cobalt, takes place by outward cation diffusion and inward vacancy diffusion. The large number of cation vacancies precipitate in the scale near the oxide-metal interface and may coalesce to form macroscopic pores, resulting in a transition from a dense, columnar scale to a duplex scale which contains an inner, fine-grained, equiaxed, porous layer. Increasing temperature and/or purity eliminate the transition, which has been found to depend upon oxide plasticity. The mechanical properties of bulk nickel oxides having a range of porosities have been studied in compression. Three regimes were observed: (1) brittle at low temperatures, (2) ductile at elevated temperatures, and (3) a transition region at intermediate temperatures. Fracture strength in the brittle region was strongly dependent on porosity due to the effect of pores on the elastic modulus and the size of fracture-initiating flaws. The plastic flow stress in the ductile region depended primarily on grain size and impurity content except for very porous materials in which porosity substantially reduced the plastic flow stress. The development of the duplex structure in scales during oxidation has been shown to depend upon inhibition of slip on the {110} 110 system in the highly textured grains rather than by diffusion-controlled processes such as creep. The duplex structure forms when the rate of deformation of the scale is less than the rate of void formation. Grain size, porosity, and impurities play an important role; all of these effects are discussed in detail.Research sponsored by the Office of Naval Research, Mathematics and Information Sciences Division, under Contract ONR N00014-69-A-0200-4021, NR-048-239.     

The mechanical properties of in-situ composites

Because in-situ composites offer such a wide selection of reinforcement types, size, and volume fractions, understanding the mechanisms controlling mechanical properties will allow more intelligent decisions to be made when tailoring a composite system for a specific application. This article provides an overview of the mechanical properties of discontinuously reinforced metal-ceramic and intermetallic-ceramic composites produced by in-situ techniques. Systems for which the mechanisms controlling mechanical properties are known are emphasized. Editor’s Note: A hypertext-enhanced version of this article can be found at http://www.tms.org/pubs/journals/JOM/9708/Aikin-9708.html. Robert M. Aikin, Jr., earned his Ph.D. in metallurgical engineering at Michigan, Technological University in 1987. He is currently an associate professor at Case Western Reserve University. Dr. Aikin is also a member of TMS.     

Intermetallic compounds and their mechanical behavior

Available information on the mechanical behavior of intermetallic compounds and its relation to relevant metallurgical phenomena and test parameters is reviewed. Brittleness at low homologous temperatures is indicated to be the most serious shortcoming of these compounds. But the room-temperature impact strength of intermetallic compounds is high compared to the refractory interstitial compounds. Furthermore, there are indications that the ductility of intermetallic compounds can be improved.     

Microstructure and mechanical properties of SiC-nanowire-augmented tungsten composites

The effect of an addition of SiC nanowire on the microstructure and mechanical properties of tungsten-based composites is investigated in this study. SiC-nanowire-augmented tungsten composites were prepared by a spray-drying process and an in situ spark plasma sintering process. Three distinctive reaction phases, tungsten, tungsten carbide (W₂C) and rod-type tungsten silicide (W₅Si₃) were formed during the sintering process. The flexural strength was significantly increased from 706 MPa to 924 MPa in tungsten composites augmented with SiC nanowires, as was the formation of W₂C and W₅Si₃ phases. The rod-type W₅Si₃ bears significant stress by both sharing a portion of the load and providing a bridging mechanism. Furthermore, a high ablation resistance at an elevated temperature was observed for tungsten composites augmented with SiC nanowires.     

Structural and mechanical properties of heat-resistant granular nickel alloys

Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 8–11, December, 1991.     

The mechanical behavior of in-situ NiAl-refractory metal composites

This article summarizes the mechanical bahavior of the in-situ NiAl-refractory metal composites at room and elevated temperatures, with particular emphasis placed on the NiAl?Cr(Mo) composite with lamellar structure. Comparisons with other NiAl-refractory metal composites are also made wherever possible.     

Modeling the dislocation properties and mechanical behavior of Ir,Rh, and their refractory alloys

While interest is growing in iridiumand rhodium-based refractory alloys as new materials for ultra-high-temperature applications, very little is known about the fundamental factors controlling their mechanical properties. Experimental difficulties with in-situ investigations of these alloys emphasize the need for theoretical modeling as an important tool for accelerated progress in this field. This article presents results of an investigation of the brittle/ductile behavior and dislocation properties in iridium, rhodium, and their L1₂ intermetallic alloys based on first-principles total energy calculations. For more information, contact Oleg Y. Kontsevoi, Northwestern University, Department of Physics and Astronomy, 2145 N. Sheridan Road, Room F251, Evanston, IL 60208-3112; (847) 491-8637; fax (847) 491-5082; e-mail ok@mars.phys.northwestern.edu.     

Microstructure, mechanical properties and thermal shock behavior of h-BN-AlN ceramic composites prepared by combustion synthesis

h-BN-SiC-AlN-TiN ceramic composites with volume content of AlN-TiN ranging from 20% to 70% were prepared by combustion synthesis from powder compacts of B₄C, Si, Al and TiN under 100 MPa nitrogen pressure. The volume fraction of AlN-TiN was found to have a significant influence on the microstructure, mechanical properties and thermal shock resistance of the composites. With the increasing volume content of AlN-TiN, the mechanical properties of the composites were improved remarkably, while thermal shock resistance decreased. Thermal shock tests showed that the critical thermal shock temperature (ΔT) was higher than 1200 °C for the composites with AlN-TiN contents of 30 vol%; while it was decreased to 850 and 670 °C for the composites with AlN-TiN contents of 50 and 70 vol%, respectively.     

Oxidation behavior of molybdenum silicides and their composites

A key materials issue associated with the future of high-temperature structural silicides is the resistance of these materials to oxidation at low temperatures. Oxidation tests were conducted on Mo-based silicides over a wide temperature range to evaluate the effects of alloy composition and temperature on the protective scaling characteristics and pesting regime for the materials. The study included Mo₅Si₃ alloys that contained several concentrations of B. In addition, oxidation characteristics of MoSi₂–Si₃N₄ composites that contained 20–80 vol.% Si₃N₄ were evaluated at 500–1400°C.     

Comparison of titanium silicide and carbide reinforced in situ synthesized TiAl composites and their mechanical properties

This study explored a synthesizing route involving in situ development of reinforcements of titanium silicides in a series of TiAl-based matrices. The main features of this processing route are: (1) Incorporating a small quantity of mechanically alloyed Ti–Al–Si and Ti–Al–Si–C powders, referred to as precursors, into Ti–Al–X (X stands for Cr, Mn, Nb, or their combination) powder mixtures that act as matrices; and (2) Hot isostatic pressing (HIPing) of the cold compacted mixture at a temperature of 1100 °C for 4 h. A series of composites based on different Ti–Al–X matrix were synthesized. The structural evolution in these composites was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The mechanical properties and compression tests at room and elevated temperatures (600 °C and 800 °C) have been investigated. In addition, the influence of alloying elements in the matrix has been evaluated from their stress–strain responses.     

Microstructure and mechanical properties of Al-Fe-V-Si/SiCp composites

The characteristics of microstructures and mechanical properties of the multi-layer spray deposited SiCp/A1-6.SFe-0.6V-1.3Si, SiCp/A1-8.SFe-1.3V-1.7Si and SiCp/Al-10Fe-1.3V-2Si composite sheets obtained by rolling after extruding were investigated. The evolution of the grain and phases of these composites during processing were examined, and the influence of the microstructures on the mechanical properties was analyzed. The experimental results show that the ultimate tensile strengths σb of the three kinds of composite sheets are 420, 535, 470 MPa respectively at room temperature, and 232, 285, 300 MPa at 315℃ and 148, 180, 200 MPa at 400 ℃. The excellent mechanical properties can be attributed to the high solid solubility, fine grain size, Al12（Fe,V）3Si precipitation particles and the SiC particles. And the composition of the matrix alloy has an obvious effect on the mechanical properties of the as-rolled sheets.     

HA/UHMWPE复合材料的微观组织及力学性能

采用机械球磨法对羟基磷灰石(HA)/超高分子量聚乙烯(UHMWPE)粉末进行混合处理,通过热压将混合粉末制成复合材料.通过X射线衍射、SEM观察及力学性能测试对混合粉末及复合材料进行微观组织和力学性能的分析.结果表明:球磨使HA颗粒得到了细化,而UHMWPE有粗化的趋势,同时HA/UHMWPE混合粉末组织更加均匀.球磨后HA没有发生分解,也没有新的物质产生.复合材料断面形貌呈网状结构,球磨时间越长,这种网状组织越均匀.随着球磨时间的增加,HA/UHMWPE复合材料的拉伸强度、冲击强度呈上升趋势.经球磨时间40 h后的复合材料具有较好的综合力学性能,同时又具有较理想的微观组织.     

Fabrication and mechanical properties of FeAl/TiC composites

1　INTRODUCTIONOver the past few decades, considerable inves tigations have been carried out to identify alterna tive binders for cermets in order to improve theirmechanical properties and also to overcome certainshortcomings, such as high cost and density, lowoxidation and corrosion resistance, and environ mental toxicity[1, 2]. Iron aluminides are of particu lar interest due to their low cost and density, highspecific strength, environmental friendliness andexcellent oxidati…     

Microstructure and mechanical properties of iron-containing titanium metal-metal composites

Titanium-based metal-metal composites show promises in many applications. In this work, iron-containing titanium-based composites were fabricated by using powder metallurgy method and rotary swaging process. Titanium-based composites with steel addition were sintered at temperature below TiFe eutectic temperature. Increase of the steel addition to 23% resulted in formation of TiFe intermetallic and density decrease in the composites. Further, the as-sintered composites present relatively good workability so hot rotary swaging of the as-sintered composites can be conducted. Steel particles were diffused into the Ti matrix and the composite transformed to a discontinuous β-Ti fiber-reinforced structure. As a result, mechanical properties (in axial direction) of the swaged composites were significantly improved. The tensile strength and elongation reached 1360 MPa and 9.3%, respectively.     

Synthesis and properties of nickel nanoparticles and their nanocomposites

For the first time, nickel nanoparticles are synthesized in reverse micelles by a radiation-chemical method. The particles are shown to be spherical with sizes of an order of magnitude of 1–100 nm. Nickel particles are oxidized by air oxygen to nickel oxide nanoparticles, retaining their shape and nanoscale dimensions. Adsorption of nickel-metal nanoparticles on silica is studied by spectrophotometry.

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Original Russian Text ? S.V. Gornostaeva, A.A. Revina, L.D. Belyakova, O.G. Larionov, 2008, published in Fizikokhimiya Poverkhnosti i Zashchita Materialov, 2008, Vol. 44, No. 4, pp. 400–403. An erratum to this article can be found online at http://dx.doi.org/.     

辅助磨擦对镍电铸层力学性能的影响

在磨擦辅助电铸镍过程中,通过改变游离微珠对电铸层表面的磨擦强弱,制备不同力学性能的镍电铸层。对所制备镍电铸层的表面形貌、织构等微观结构和显微硬度、抗拉强度及伸长率等性能进行测试和分析。结果表明:采用卧式放置的阴极能制得材料组织结构均匀的电铸层。且随着阴极表面线速度的提高,游离微珠对电铸层的整平作用和晶粒细化作用增强。在不同线速度下采用旋转阴极可以制备大范围力学性能的镍电铸层,其表面粗糙度为0.15~0.03μm、硬度为185~410HV、抗拉强度为525~1 020 MPa、伸长率为24%~4%。     

Bending-fatigue behavior of bulk metallic glasses and their composites

Amorphous alloys with high glass-forming ability and thermal stability were discovered in the 1990s. In the following years, the alloy design increased the critical casting thickness to several centimeters, and a homogeneous dispersion of nanoscale particles was found to improve the ductility. Therefore, bulk metallic glasses (BMGs) are being studied widely because of their potential as structural materials. The fatigue behavior is an important characteristic of structural materials. The current review documents the bending-fatigue studies of BMGs and their composites. The fatigue characteristics of these alloys in different loading conditions and environments are summarized and compared in this paper. The factors affecting the fatigue behavior of BMGs and their composites are discussed. The mechanisms of fatigue-crack initiation and propagation in BMGs are addressed in this review. In order to broaden the scope of applications of BMGs, a fundamental understanding of the fatigue behavior is critical for the design of new alloy systems and the development of the processing techniques.