Fabrication And Performance Investigations Of YSZ-Ni Series Nanocomposite Cermet

YSZ-Ni (nickel - yttria stabilized zirconia) cermets have been widely used in the solid oxide fuel cells (SOFC) and functionally gradient materials (FGM) areas. Solid oxide fuel cells are electrochemical energy conversion device with high efficiency, low pollution and environmental friendship. SOFC is mainly composed of three parts: electrolyte, anode and cathode. The prime requirements for anode materials are good electrical properties, a poly-hole microstructure and compatibility with other fuel cell components. At present, YSZ-Ni cermets are usually used as anode of SOFC.ZrO2 and metal Ni show no wettability in vacuum with a contact angle of 117 . And how to improve the wetting of ceramics by liquid metals has great significance to the preparation of high performance YSZ-Ni cermets.Different from the general method of preparing ZrO2-Ni cermets in which Zr02 and NiO powder are mixed together, pressed, sintered and reduced, we adopt a novel coordination-gel method to prepare ZrO2-Ni nanocrystalline composite powder in this study. The preparing process is as follow: mixing the nickel salt, zirconium salt and stabilizer in the solvent (distilled water) to prepare mixing solution according to a certain ratio; commingling the mixing solution and coordination solution of carboxylic ammonia in accordance with a certain rate to form sol, drying the sol and turning it into gel, pre-sintering the gel to get the ZrO2-NiO powders and the ZrO2-Ni nanocrystalline composite powders were gained by reducing the ZrO2-NiO powders.The aim of this work is to study the influences of metal elements and their carbides on the performance and wettability of cermets by preparing the YSZ-Ni composite materials containing metal elements such as Cr , V, Mo, Ti and their carbides.The crystal phases were investigated by X-ray diffraction (XRD). The patterns showed that the YSZ-Ni-based powders contained mainly tetragonalZrO2. This is because the Y2O3 had entered into the clearance of ZrO2 crystal lattice to stabilize the ZrO2 The particle size distribution of YSZ-Ni, YSZ-Ni-Cr and YSZ-Ni-V composite powders were determined by X-ray small-angle diffraction. Results showed that they have a mean size of 72.3 nm, 63.4 nm and 42.2 nm separately.The fractured surface morphology of the cermets were observed by a scanning electron microscope (SEM). Results showed that the YSZ-Ni-Cr and YSZ-Ni-V cermets had a better wettability than the YSZ-Ni cermet while the wettability of YSZ-Ni-Mo cermet was worse. The grain sizes of the YSZ-Ni-based cermets sintered by hot-pressing technique were about 0.3 rn with a homogeneous microstructure and uniform distribution.The electrical conductivity were measured from room temperature to 800 掳C by using a four-probe method. Result showed that all the samples had a blend conductivity mechanism.