Papers by Author: Ying Hu Dong

Abstract: The fabrication of porous diamond preforms is a key step for obtain diamond/metal copposites with high proporties by liquid infiltration. In order to prepare porous diamond preforms with high strength and excellent compatibility with liquid metal. The diamond metallization should be treated first usually.In this paper, the microstructure, composition, phase structure and bond strength of tungsten coating on diamond surface by using salt-bath method were observed and analyzed experimentally including scanning electron microscope (SEM), energy spectrometer analysis (EDS), X-ray diffraction (XRD). The results show that tungsten start to react with carbon atoms on the surface of diamond at 1100°C while a dense and completely covered coating can be obtained at the temperature of 1150°C with 10-120 minutes dwell time. With this process, the layer on diamond surface can be regulated in the range of 1.18 to 3.24μm. The phase structure of coating from outside to inside is W, W₂C and WC phase, respectively. Thermal shock experiments also show that the coatings on diamond surface have excellent bond strength as well as high temperature resistance.

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: A binder comprising of 60% PW (paraffin wax), 10% HDPE (high-density polyethylene), 12% PS (polystyrene), 13% PPR (random-polypropylene), and 5% SA (stearic acid) has been selected and successfully employed to fabricate the diamond preforms possessing high strength and well shape retention capability. Various effects of processing methods on the properties of the diamond preforms have been investigated. The results indicate that the binder consisting of PW-HDPE-PS-PPR-SA possesses excellent comprehensive rheological properties and is more appropriate as the organic vehicle for fabricating porous diamond preform. It has been evaluated that the mixing of 140m size diamond particles with 20m size diamond particles in the weight proportion of 3:1 provides the best particle size distribution for preparation of diamond preforms. It is also observed that impregnation of preform with 1.7wt (SiO2)% water glass and subsequently heat-treated in vacuum at 800°C for 40min yields in high strength (with the strength of 7.1 MPa) diamond preform for infiltration. The strengthened preforms have been observed to possess an excellent shape maintaining capability. It is concluded that the diamond-copper composites fabricated by utilizing this high strength preform through hot-press infiltration method have high relative density of 96.4% and thermal conductivity of 300W.m-1.K-1.