Advanced Materials Research Vol. 628

Abstract: The influences of solution treatment, deformation strain, and nanometric Al₂O₃ particulate on dry wear properties for nanometric Al₂O₃ particulate reinforced Al alloy matrix Composites manufactured by casting were investigated. The result showed that both the wear resistance of AL matrix and the composites increased rapidly with increasing solution temperatures. The wear resistance increased slightly with increasing deformation strain for the composites. The wear resistance of the composites is higher than the AL matrix after the same deformation and heat treatment. Microstructure observation revealed that the grain sizes of the composites increased with increasing solution temperature and decreased with more severe deformation. Abrasive wear was the main wear mechanism both for the AL matrix and the composites.

Abstract: The flow stress behavior and constitutive equation of the nanometric Al₂O₃ particulate reinforced Al alloy matrix composites were investigated in the temperature range from 590k-710k, and at the strain rates range from 0.01s^-1-1s^-1. Hot compression tests were carried out with thermal simulation machine Gleeble-1500. The results showed that the values of the true stresses rose rapidly and then held constant to some extent after attaining the peak values with the increasing strains at different deformation condition. The flow stress for the composites increased with increasing strain rate, which means that the experimental material is a sensitive material of positive strain rate, and decreased with decreasing temperature. Dynamic recovery and dynamic recrystallization occurred during hot compression of the composites. The constitutive equation represented by a Zener-Hollomon parameter in an exponent-type and the deformation activation energy are as follows respectively: σ=71.43ln{(Z/4.37×10¹¹)^1/5.94+[(Z/4.37×10¹¹)^2/5.94+1]^1/2}, Q=197KJ mol^-1.

Abstract: The purpose of this paper is to prepare nickel particles by arc plasma method with hydrogen addition. The effect of anode jet formation on the nanoparticle production was investigated by high-speed camera observations. The high-speed camera system with appropriate band-pass filters successfully provides the observation of anode jet image without cathode jet image. The areas of the anode jet and the cathode jet were separately estimated from the high-speed images. From these observations, the periodical fluctuation of the anode jet was confirmed. Higher hydrogen concentration leads to larger anode jet area, resulting from the enhanced evaporation of the anode material.

Abstract: In this study, mechanical properties of composite laminates reinforced with various forms of glass fibers have been investigated. Tensile testing, impact testing and optical microscopy and SEM analysis results were discussed. The results of glass fiber reinforced novel composite material have been compared with the results of a commercial car front bumper material tests performed in same conditions. Study concluds that glass fiber has positive hybridization effect and increased tensile strengths, elastic modules and impact strengths in laminar hybrid composites.

Abstract: Highly ordered nano crystallized Ag₂Se nanowires of diameter 200 nm have been successfully prepared through direct chemical method using Anodic Alumina Membrane (AAM) as a template; AgNO₃ as cation precursor agent and Na₂SeSO₃ as Se precursor, respectively at room temperature. The qualitative analysis of the EDAX spectrum of nanowires shows that the atomic composition of Ag and Se in synthesized nanowires is close to 2:1 stoichiometry. XRD spectrum confirms orthorhombic structure. UV-Vis absorption spectrum provides estimation of the optical band gap 1.41 eV of nanowires.

Abstract: In this paper, glass fibers were prepared by centrifugal-spinneret-blow(CSB)process. The diameter and microstructure of glass fibers have been investigated by scanning electron microscopy(SEM)and vertical optical microscope(VOM).The thermal conductivity and the thickness of glass fiber samples were determined by heat flow meter thermal conductivity instrumentation.The results indicated that the diameter of glass fibers prepared by CSB process can reach the ultrafine grade by adjusting the ratio of raw materials and process parameters.The thermal conductivity of glass fiber sample was 0.0298W/(m·K)when the diameter was 3μm and the density was 62kg/m³.The thermal conductivity of glass fiber sample decreased with the reduction of fiber diameter when the density of glass fiber sample is constant.

Abstract: The influence of density on the thermal conductivity of fiberglass felt is studied by experiment.Experimental data obtained using the coefficient of thermal conductivity measuring instrument(Germany Netzsch HFM 436).The results show that the thermal conductivity of the low-density fiberglass felt increases with the increasing of density，when the density of fiberglass felt is below a certain value,the thermal conductivity is tend to a stable value.At last the conclusion that using the heat-transfer mechanism of the porous materials explains this phenomenon has also been drawn by experiment.

Abstract: The optimum ratio of rhenium and cobalt in Co-Re binder of a cemented carbides based on the analysis of phase diagrams and studying the carbides properties is defined.It is shown that properties of carbide binder at the same ratio of rhenium and cobalt are also the same, and the carbide properties are determined by the amount of carbide binders.Researches of wear resistance of the tool from carbides with Co-Re binder at machining of a constructional steel and hard-to-machining alloys have confirmed their high efficiency.

Abstract: A simpleand inexpensive top down approach to fabricate micropatterned carbon micro- and nano-fibers has been developed combiningCarbon-MEMS technology, Low Voltage Near-Field Electrospinning (LVNFES),and isotropic dry etching.A multitude of applications can take advantage of these patterned carbon nanofibers especially in the field of electrochemical sensors and nanoelectronics. In particular, wehave developed a novel polymeric ink that exhibits excellent electrospinning capability in a LVNFES setup and that does survive the pyrolysis process. To illustrate the potential of this new ink, we have fabricated carbon fiberssuspended on Carbon-MEMS structures.The fiber thickness can be controlled by adjusting the LVNFES voltage and using isotropic oxygen plasma based dry etching.