Papers by Author: Hai Gen He

Abstract: WC-Co tapes with different Co contents were prepared by rolling the mixtures of WC-Co powders and polymer binders, and layered WC-Co green compacts with discontinuous distribution of Co contents were obtained by laminating the green WC-Co tapes together. After burning off the binders and other organic composition in H2 atmosphere, the green compacts were sintered in vacuum. Microstructure of both the green and the sintered tapes were observed by scanning electron microscope. An electron probe microanalyser was used to measure the linear distribution of Co element in the layered WC-Co cemented carbides. Sintering densification and mechanical property of the multilayered WC-Co alloys were also investigated and compared with those of conventional WC-Co alloys with nominal Co contents of 8% and 12%, respectively. It was shown that by controlling sintering temperature and time, a continuous graded distribution of Co composition can be realized in the laminated WC-Co alloys, with more Co-rich phase in the original high Co content side (12%). Furthermore, the graded WC-Co cemented carbides can realize a combination of high hardness and high strength.

Abstract: NiO/Ce0.8Sm0.2O1.9 (NiO/SDC, 65wt.% NiO) composite powders were synthesized by a glycine-nitrate process (GNP) to fabricate Ni/SDC anode-supported solid oxide fuel cell (SOFC). The results show that the composite powders are composed of single cubic phases of NiO and SDC and have a particle size in nanometer range. NiO/SDC ceramics were prepared from the NiO/SDC powders and were converted into Ni/SDC cermets by reduction in H2, which were employed as anode materials for SOFC with SDC electrolyte. It is shown that Ni/SDC cermets from the NiO/SDC composite powders by the GNP have porous and homogeneous microstructures and show good electrical conductivity. A single SOFC based on Ni/SDC anode with about 50µm SDC electrolyte film and about 80µm La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode was constructed. Open circuit voltage (OCV) of the cell is about 0.8V and maximum power density is 361.42 and 394.78 mWcm-2 at 750 and 800°C, respectively.