Abstract: Milled form of mesophase pitch-based graphite fibers were coated with a chromium layer using chemical vapor deposition technique, and Cr-coated graphite fiber/Cu composite with 50 vol.% fibers was fabricated by hot-pressing. The composite was characterized with scanning/transmission electron microscopies and by measuring thermal properties, including thermal conductivity and coefficient of thermal expansion (CTE). The results showed that the milled fibers were preferentially oriented in a plane perpendicular to the pressing direction, leading to anisotropic thermal properties of the composite. The Cr coating reacted with graphite fiber and formed to a continuous and uniform Cr3C2 layer. This carbide layer established a good metallurgical interfacial bonding in the composite, which can improve the thermal properties effectively. The in-plane thermal conductivity and CTE of the composite reached to 392 W/mK and 6.5 ppm/K respectively, making the composite suitable for being electronic packaging materials.
Abstract: This paper mainly aimed at uniform microstructure generally of particulate reinforced metal matrix composites and put forward the method, which was severe plastic deformation, for microstructure homogenization of particulate reinforced metal matrix composites. Basis on introducing origin of severe plastic deformation and the theory of cumulative extrusion severe plastic deformation, the paper researched the microstructure homogenization of silver metal oxide by cumulative extrusion severe plastic deformation. The result showed that microstructure homogenization of silver metal oxide could be uniformed by cumulative extrusion severe plastic deformation. The results also showed that condition of microstructure homogenization was obtained fine or nanometer second phase particles in fabrication and selected intensity of severe plastic deformation according to system and character of particulate reinforced metal matrix composites.
Abstract: Based mainly on SiC aggregate and fine powder, silicon powder, flake graphite (300 μm, 45 μm), α-Al2O3 micro-powder and AlN powder, Graphite-SiAlON bonded SiC composite were prepared. The influence of graphite addition, which varied from 0 to 9.7%, and its grain size on the oxidation resistance was investigated at 1 150 °C under air atmosphere. The results show that: 1) mass change rate reduces with the increase of graphite addition, the mass change rate of sample with 45 μm graphite is higher than that of sample with 300 μm graphite; 2) the cold modulus of rupture of sample with 45 μm graphite after oxidation is higher than that of sample with 300 μm graphite; 3)the oxidation resistance declines along with the increase of graphite addition, additionally, the oxidation resistance of sample with 45 μm graphite is superior to that of sample with 300 μm graphite; 4) 7.5% graphite is recommended as the proper addition.
Abstract: Using the steel containing 0.45 percent of carbon as matrix, high carbon ferrochrome as cast-penetrated agent, the steel-based surface composites were fabricated by conventional cast-penetrating process combined with the thermite reaction. The influence of thermite reaction on the microstructures and properties of cast-infiltration layer was researched. The results show that the interfacial bonding is metallurgical fusion between cast-infiltration layer and the matrix under the suitable technological parameters, the thermite reaction during the process of cast-penetrated realizes thermal compensation for liquid metal and improves the mobility of liquid steel by reducing oxidation film of liquid steel surface, consequently increase the thickness of cast-infiltration layer; The ceramic phase of Al2O3 which is generated during the thermite process improves the microhardness of cast-infiltration in a certain extent.
Abstract: In this paper, the tensile and bending strengths of T-300 carbon fiber three dimensional braided/epoxy resin composites at 23 oC and 150 oC were researched. The results indicate that the effect of temperature on the tensile strength and bending strength of three dimensional braided composites is sentitive. However high temperature makes bending strength of 3D braided composites lost more than that of tensile strength of 3D braided composites. The average tensile strength of 3D braided composites at 150 oC is 65.06% of average tensile strength of 3D braided composites at 23 oC. The average bending strength of 3D braided composites at 150 oC is only 11.44% of average bending strength of 3D braided composites at 23 oC. This means that application temperature should be taken into account when 3D braided composites are used.
Abstract: Carbon fiber and glass fiber composites impregnated with aspartimide oligomer were fabricated and their structure-property correlation was studied. Experimental results reveal that with increasing chain length of aspartimide oligomer, mechanical properties of composites increase, but thermal properties decrease. With decreasing chain length, storage modulus and loss tan delta peak temperature of composite increase as a consequence of increased rigidity of matrix polymer resin resulted from crosslink density increase, concurrently, loss modulus and tan delta value of composites undergo a decrease.
Abstract: In order to study the curing characteristics of common resins including bisphenol-A epoxy vinyl ester resin, phenolic epoxy vinyl ester resin and unsaturated polyester resin, the curing time of three resins was tested using cobalt naphthenate as accelerator and methyl ethyl ketone peroxide as curing agent. The results showed that the resin curing time reduces with the experimental temperature rising; in order to control the curing time at about 25 minutes when the experimental temperature is 23°C, the curing agent adding proportion of bisphenol-A epoxy vinyl ester resin, unsaturated polyester resin and phenolic epoxy vinyl ester resin are respective about 0.7%, 0.5% and 1.8%. The composites made by bisphenol-A epoxy vinyl ester resin have excellent tensile strength and composites made by phenolic epoxy vinyl ester resin have best bending strength.
Abstract: The adsorption of H2S molecule on Si-doped and Ag supported Si-doped graphene is studied by first-principles calculations. We find that the H2S floats on the Si-doped graphene sheet, indicating a weak physisorption. The calculated net charge transfer, charge density difference and density of states give evidence that the adsorption of H2S on Ag supported Si-doped graphene is by chemisorption. Moreover, the desorption and dissociation of H2S adsorbed on Ag supported Si-doped graphene occur at the external electric field of 1.4 and -0.8 V/Å, respectively. Therefore, the Ag supported Si-doped graphene can be expected to be a novel sensor for the detection of H2S gas.
Abstract: To improve the poor mechanical properties of resin mineral composite, molybdenum fibers reinforced technology and mechanism are researched. The micro-surface morphology of new and wire electrical discharge machining used molybdenum fibers are analyzed, and the cohesive reinforce mechanism is deduced respectively. Two-dimensional simplified finite element model of resin mineral composite reinforced by molybdenum fibers is established for the simulation analysis of bond-slip of interface between fiber and resin matrix. Tests on the internal stress distribution of resin mineral composite without fibers and resin mineral composite reinforced by molybdenum fibers are carried out. Research results show that the addition of molybdenum fibers can effectively restrict the deformation of composite, and the randomly distributed pits on the surface of wire electrical discharge machining used molybdenum fibers can enhance the strengthening effect and reduce the cost of composite.