ZHOU Yuan-xin, XIA Yuan-ming. Effect of Strain Rate on Mechanical Behavior of Cf/Al Composites[J]. Journal of Materials Engineering, 2000, 0(9): 3-6.
Tensile impact tests of Cf/Al metal matrix composite were carried out by a self-designed tensile impact apparatus.The stress/strain curves of composites in strain rate range from 0.001s-1 to 1300s-1 were obtained.The experimental results indicate that the Cf/Al composite is a rate-sensitive material,namely the strength,failure strain and residual strength of composite all are depending on strain rate.According to the statistical analysis and models,mechanical parameters for the composites and their relationship with strain rate are obtained from experimental results.The simulated stress/strain curves from the model are in good agreement with the test data.
XIE Zheng-fang, CHEN Zhao-hui, LI Yong-qing, ZHENG Wen-wei, HU Hai-feng, XIAO Jia-yu. Application of Tantalum in the Preparation of Polycarbosilane Derived Ceramics[J]. Journal of Materials Engineering, 2000, 0(9): 7-10.
The application of tantalum in the preparation of polycarbosilane derived ceramics was investigated.The results show that Ta can decrease the porosity of the green compact and,since Ta could react with gas volatile of PCS during pyrolysis and/or free carbon to produce carbide and N2 to produce nitride,increase the ceramic yield of PCS.However,Ta can not restrain the linear shrinkage of the green compact upon pyrolysis.The linear shrinkage is increased with increasing the volume ratio of ψ(Ta:PCS).
YANG Xiao-ping, RONG Hao-ming, LU Ze-dong. A Study of the Electrical Properties of Carbon Fiber Conductive Composite[J]. Journal of Materials Engineering, 2000, 0(9): 11-14.
The electrical properties of carbon fiber facial heating-sheet made of carbon fiber conductive paper laminated with FR-4 brominated epoxy prepreg glass cloth have been studied.The results show that the curing of FR-4 prepreg influences the changes of electrical properties.Different kinds of conductive paper samples have different decrease ratios.The resistance and temperature (R-T) relationship of facial heating sheet during the heating and cooling recycling process present some difference between the heating curve and the cooling curve.The samples exhibit PTC or NTC effect,but the resistance at room temperature keeps stable after several times of heat treatment.Resistance of facial heating sheet decreases slightly and keeps stable after use for several hours.This kind of facial heating sheet has constant power under long use.Power density and surface temperature curve show linear behavior.
XIANG Yong, XIE Dao-hua. Structure and Characteristic of ABO3-Type Oxide and Its Application[J]. Journal of Materials Engineering, 2000, 0(9): 15-18.
All kinds of ABO3-type oxides are summarized,including various crystal structure and their electrical,optical,acoustics properties.It is discussed that ABO3-type crystal and ceramic materials are applied and developed widely in the fields about modern electronics and information,aerospace,defense and military.
HAN Zhao-hui, ZHAO Zi-qiang, DU Qing-li. Study on the Optical Properties of Embedded Cluster Ge:CaF2 Films[J]. Journal of Materials Engineering, 2000, 0(9): 19-20,24.
Embedded cluster Ge:CaF2 films with different cluster sizes ranging from 2.1nm to 7.8nm have been produced by evaporation method and studied.Electron diffraction reveals that the clusters' microstructure belongs to microcrystalline structure and the lattice constant expands about 4.8% compared with balk Germanium.Absorption properties show good agreement with the Quantum-Confinement-Effect theory.With the decreasing of the size,blueshifts of the absorption edges are observed and the corresponding band gaps become wider.Strong absorption indicates that in the cluster states,conversion from indirect-band gap to direct-band gap has been realized.
YANG Shi-qing, PENG Bin, JIANG Hong-chuan, ZHANG Wen-xu, WANG Hao-cai. Fabrication and Rheological Properties on Composite Intelligent Magnetorheological Fluids[J]. Journal of Materials Engineering, 2000, 0(9): 21-24.
Fine bimetallic Co-Ni alloy powders were prepared by polyos method.The composite magnetic particles were obtained by crushing and grinding the mixtures of ferromagnetic material,the microporous material and the binder.In order to overcome the sedimentation and separation of ferromagnetic and non-ferromagnetic phase,the density of the composite particles equal to that of dispersing liquid was set.The advantage of the present magnetorheological fluid (MRF) are the absence of sedimentation.In the absence of magnetic field,the variations of shear stress τy with shear rate is satisfies the constitutive equation,i.e.,τ=11.4γ0.7.The variations of shear stress and apparent viscosity with the magnetic field strength and temperature are discussed,The present MRF manifests the higher-sensitivity of rheological properties under low magnetic strength and greater temperature stability.
ZHAO Hong-sheng, ZHU Dong-mei, ZHOU Wan-cheng, WU Jing-bo. Synthesis and Characterization of the PbBr2-PbCl2-P2O5 Glasses with Different Melting Temperature[J]. Journal of Materials Engineering, 2000, 0(9): 25-27,6.
A series of PbBr2-PbCl2-P2O5 glasses were prepared and characterized to research the effect of melting temperature on the properties of glasses.The glass-forming regions were explored and the stability of the glasses against crystallization studied.The density,characteristic temperatures,chemical analysis compositions,and infrared absorption spectra of the glasses were measured.The results show that the PbBr2-PbCl2-P2O5 ternary system melted at 530～540℃ has a broader glass-forming region which extended to the side of PbBr2 than that melted at 450～470℃.The density of PbBr2-PbCl2-P2O5 glasses can be up to 5.51 g·cm-3 with a Tg of 200℃.Glasses melted at 450～470℃ contain a large amount of hydroxyl and ammonium because of the uncompleted decomposition of NH4H2PO4.When the melting temperature is increased to 530～540℃,the absence of the hydroxyl and ammonium increases both the glass transition temperature and the density.The results of infrared absorption spectra show that the decomposition of NH4H2PO4 of some glasses melted at 530～540℃ is more complete than that of glasses melted at 450～470℃.
GONG Rong-zhou, GUAN Jian-guo, YUAN Run-zhang. Characterization of in situ Synthesizing Polyaniline/Barium Titanate Nanocomposites[J]. Journal of Materials Engineering, 2000, 0(9): 28-30.
Polyaniline-barium titanate(PAn-BaTiO3) nanocomposite particles have been prepared in situ.The PAn-BaTiO3 nanocomposites particles were characterized with IR,SEM,TG and DTA etc..The results show that the process of polyaniline is similar as by the oxidative polymerization of aniline with H2O2 in 1M HCl solution,and the surfaces of BaTiO3 nanoparticles which are 5～10nm in diameter are completely coated by polyaniline,while the average diameter of the particles is less than 2～3μm.PAn-BaTiO3 nanocomposites (when the ratio of BaTiO3 to PAn is 0.91) have a thermally stable temperature of more than 540℃,well above 60℃ higher than PAn particles.The conductivity of PAn-BaTiO3 nanocomposite particles is transformable from 100 to 10-11S/cm by dedoping(or doping) them with various concentrated NaOH,ammonia water or HCl solutions using an equilibrium method.
Electroplating aluminium onto NdFeB magnets from organic solution of aluminium chloride and lithium aluminium hydride in tetrahydrofuran benzene solvent is studied.The best deposits can be obtained at current densities of 1～5A/dm2.The electroplating rates are 72μm/h at current densities of 10A/dm2.The corrosion resistance of the Al electroplated magnets in 3% NaCl solutions is much better than Ni,Zn electroplated,and highly enforced by anodic oxidation and chromate treatment.The results prove that electroplating aluminum protective deposits from organic solutions is effective for NdFeB magnets.
ZENG Peng, HU She-jun, XIE Guang-rong, HUNG Na-can, WU Qi-bai. Microstructure and Properties of (Ti,W)xN Alloy Coatings Deposited by Multi-Arc Ion Plating[J]. Journal of Materials Engineering, 2000, 0(9): 33-35,41.
(Ti,W)xN coatings were deposited by multi-arc ion plating using the Ti/W composite cathode target,The microstructure and properties of the coatings were studied,The results showed that the coatings consisted of (Ti,W)2N mainly had low porosity and high micro-hardness and oxidation resistance.The composition demixing phenomena between coatings and composite target was analyzed.
ZHAO Yu-xin. Cold Deformation Behaviors of GH625 Alloy and Their Effects on the Mechanical Properties[J]. Journal of Materials Engineering, 2000, 0(9): 36-37.
The effects of cold deformation on the mechanical properties of sheet superalloy GH625 and the mechanism of cold work hardening were investigated.It is indicated that the tensile strength of GH625 is increased but the ductility is decreased with increasing the degree of cold deformation.Significant effects of cold deformation on the stress rupture and thermal mechanical fatigue properties of the alloy are revealed;the best combination of stress rupture and fatigue properties and great overall mechanical properties are achieved after 20% cold deformation.The cold work hardening is affected by both the recovery and recrystalization after cold work and by the solid solution temperature.
WANG Jun, YAO Min, WANG Juan, CHEN Ge, SONG Yong-cai, FENG Chun-xiang. Preparation of Shaped Polycarbosilane Fibers[J]. Journal of Materials Engineering, 2000, 0(9): 38-41.
By trilobal spinning subassembly,the shaped polycarbosilane fibers were prepared from polycarbosilane by melt spinning.The effects of spinning temperature,spinning pressure and drawing velocity on the degree of profile and effective diameter of the fibers were studied and the preparation processing of shaped polycarbosilane were determined.
YU Gui-lin, ZHAO Xin. The Casting Process of Large Closed Annular Castings Made of High Strength Al-Cu Alloy[J]. Journal of Materials Engineering, 2000, 0(9): 42-43.
Casting properties of alloy ZL205A and its advantages were introduced in this paper.At the same time,the main points of casting process of large closed annular casting made of ZL205A were discussed and analysed.
LIU Hai-feng, XU Yong-li, TIAN Shi. Research Progress on the Fatigue Properties of Perovskite Ferroelectric Thin Films[J]. Journal of Materials Engineering, 2000, 0(9): 44-46.
Perovskite ferroelectric thin films have been extensively studied because of their applications in nonvolatile memories.However,the fatigue problem is the main hindrance to their applications.In this paper,the recent progresses on the fatigue mechanisms and the methods to mitigate fatigue of perovskite ferroelectric thin films are reviewed briefly.
