Papers by Keyword: HP

Abstract: A four-layer functionally gradient material (FGM) of Cu/Ti₃SiC₂ was fabricated by hot pressing (HP) in vacuum. Oxidation behavior of Cu/Ti₃SiC₂ FGM was also investigated. The results show that the oxidation dynamics of Cu/Ti₃SiC₂ FGM at 600~800 °C for 30 h in air followed parabolic rate law. The hardness was increased with increasing content of Ti₃SiC₂. Thermal shock resistance was well owing to the effect of thermal stresses mitigated with FGM.

Abstract: Ti/Al/TiC mixed powders were used as the raw materials for the fabrication of functionally graded material (FGM) by hot pressing sintering. The sample was analyzed by SEM combined with Metallographic microscope and Energy Disperse Spectroscopy,The results show that each layer is composed of TiC and Ti₂AlC, without containing other phases. The size of TiC grains are about 3-6 μm. With TiC content in the layers increasing, Ti₂AlC grains gradually decrease. The lathy Ti₂AlC grains of the FGM have a length of about 10 μm and a width of about 4 μm. The interface of each layer has a good combination with a certain thickness transition layer.Microhardness tester is used to analyse the hardness of material.The results show that the Vickers hardness of every layer increases with TiC content increasing. The thermal shock performance test found that material has good thermal shock performance.

Abstract: Ceramics based on nanosized plasma chemistry Si3N4 powder compositions s (30-100 nm) is processed by activated pressureless sintering, hot pressing and hot isostatic pressing. Microstructure characterization of the obtained materials by means o light and scanning microscopy revealed no correlation between microstructure and the bulk consolidation method . Average grain size in all cases was 200-500 nm. Comparative characterization of the physical and mechanical behavior of the analyzed samples showed the following results: relative density - over 99 %, flexural strength – over 700 MPa, Vickers hardness - 16-17GPa, fracture toughness – 6.5-7.4 MPa·m1/2. The activated pressureless sintered samples demonstrated physical and mechanical behavior comparable to the samples consolidated by other methods. Activated pressureless sintering of nanosized plasma chemistry Si3N4 powders led to considerable economic advantages in processing Si3N4 spherical rotation bodies for hybrid roller bearings and cutting tools. Silicon nitride (Si3N4)-based structural ceramics is widely studied and used for over half a century due to its unique properties: low density, combined with high strength and wear-resistance, high decomposition temperature, high oxidation resistance, low friction coefficient and high resistance to chemical corrosion[1].

Abstract: Hybridization is a promising method for core/shell particles by a mechanical shock process involving dry blending and dry impact blending. In this paper, hybridization was used to prepare TiB2/Ni ceramics/metal and TiB2/Al2O3 ceramics/ceramics core/shell particles. The mechanism of the formation and the features of the core/shell particles were analyzed. The nano- Al2O3 particles can be coated on the surface of micron TiB2 particles directly by hybridization, The sub-micron Al2O3 particles can be coated on the surface of micron TiB2 particles, only with the introducing of PE-wax as transition layer. The mechanical properties of cermet sintered from TiB2/Ni core/shell ceramics/metal particles were compared with that from TiB2/Ni blended particles.

Abstract: P-type thermoelectric material Si0.8Ge0.2 was fabricated by mechanical alloying(MA) and Hot-Press Process(HP) The effect of Boron(0.25~2wt%) addition on the thermoelectric properties of p-type Si0.8Ge0.2 alloy was reported. Experiments showed that the electrical conductivity decreased with Boron content at temperature ranging from 500K to 1250K. The carrier concentration measured by the Hall effect measurement also decreased as a function of doping level. With increasing temperature, the Seebeck coefficient and the power factor increased with boron content. Based on measured results, the Figure of Merit (Z) value of 0.5 wt% Si0.8Ge0.2 alloy increased with the small addition of Boron, and reached maximum rapidly; the Z value was 0.9×10-3/K, the highest value among the prepared alloys.

Abstract: A novel approach was developed to prepare Ni-coated TiB2 cermet. Fine Ni particles with mean particle size of about 80 nm were impacted onto coarse TiB2 particles having a mean size of about 5 μm to form Ni-coated TiB2 powder by Hybridization. The conventional blended TiB2-Ni powder, as well as Ni-coated TiB2 powder, was sintered by hot pressing (HP) method and Spark Plasma Sintering (SPS) method. Compared with the conventional blended TiB2-Ni cermet, particle features and mechanical properties of the Ni-coated TiB2 cermet were investigated. The microstructure analysis reveals that the thickness of Ni film is around 4 nm. It is concluded that the mechanical properties of Ni-coated TiB2 cermet are superior to the blended TiB2-Ni cermet.