Papers by Author: Zhi Guo Ye

Abstract: Diamond-copper composites are fabricated by spark plasma sintering (SPS). The effects of particle size, original properties and coatings of diamond on the thermal conductivity (TC) of diamond-copper composites have been investigated, respectively. The results indicate that thermal conductivity of composites enhances with an increase in particle size and original properties of diamond. Composites with Cr, Ti or Ni coatings on diamond surface appear remarkably higher TC than that which without any coatings. The improvements of TC of diamond/copper composites are mainly due to the large particle size diamond decreasing the interfacial area in composites, the high original properties diamond possessing higher original TC, and coatings on diamond surface declining the interfacial thermal resistance and improving the wetting properties between diamond and copper.

Abstract: Different phase compositions and microstructures of oxide scales were formed on the surface of SS400 hot rolled alloys by employing various heat treatment processes. Cyclic wet-dry immersion corrosion test, electrochemical impedance spectroscopy were used to investigate the corrosion resistance of strips with scales fabricated by different heat treatment processes. The results reveal that difference in the corrosion resistance of the various scales is due to the difference in the grain size of Fe₃O₄ phase. Furthermore, the difference in the corrosion resistance of different oxide phases, exhibited by various scales, also render the strips to give various corrosion behaviors. It is surmised that the strip with oxide scale, which consist of a small mount of the outer layer Fe₂O₃ phase distributed continuously and a large quantity of the inner layer Fe₃O₄ phase with the fine grain size, and possess nice compactness, continuity, integrity in the morphology structure, has the best corrosion resistance.

Abstract: Nanostructured elements, including: manganese-molybdenum (Mn-Mo) oxide, manganese-molybdenum-tungsten (Mn-Mo-W) oxide, manganese-molybdenum-iron (Mn-Mo-Fe) oxide, manganese-molybdenum-cobalt (Mn-Mo-Co) oxide, manganese-vanadium-tungsten (Mn-V-W) oxide, manganese-vanadium-iron (Mn-V-Fe) oxide and manganese-iron (Mn-Fe) oxide, have been anodically deposited onto titanium substrates by employing an iridium dioxide interlayer (Ti/IrO₂ anode). The electrochemical characteristics of the resultant oxide deposits have been investigated by cyclic voltammetry (CV) in an aqueous 0.1 M Na₂SO₄ solution. The voltammetric behaviors of the oxide deposits observed are significantly influenced by the doped elements. Molybdenum doping is found to be advantageous at improving the capacitance characteristics of anodically deposited manganese oxide. Comparatively, iron and vanadium doping are found to be unfavorable. The structure and crystallinity of these deposits have been identified by X-ray diffraction (XRD). The surface morphologies of these oxides were acquired from field emission scanning electron microscopes (FESEM). The high values of electrical parameters for the doped deposits are attributed to the net-like and sponge-like nanostructure, and low crystallinity of the doped manganese oxides. The deposit of Mn-Mo oxides exhibits an excellent capacitive-like behavior, possessing the maximum specific capacitance of 810 F g^-1 at a CV scan rate of 5 mV s^-1 in aqueous 0.1 M Na₂SO₄ solution.

Abstract: SiCp/Al composites were fabricated by ceramic mold freedom infiltration and pressureless infiltration, respectively. The microstructure and phases are analyzed by metallurgical microscope and coefficient of thermal expansion of SiCp/Al composites were tested by thermal dilatometer. The results show that SiCp/Al composites are compact and uniform. SiC particles were dispersed uniformly in Al matrix, and SiCp segregation was not found in composites. Under a certain SiCp size range, space between SiCp decreases with decreasing of SiCp size, and CTE of SiCp/Al composites also decreases with decreasing of particles size. Compared with CTE of composite with pure aluminum as matrix, CTE of composite with ZL101 as matrix is less. Under the annealing process, CTE of SiCp/Al composites with ZL101 as matrix is less than that with the solution and aging, which indicated that its dimensional stability of resisting to temperature fluctuation is better, and thermal expansion behavior and characteristic of SiCp/Al composites are also better.