Fabrication of Macroporous Ni/YSZ Compound Derived From Ordered PMMA Microspheres as Template

• Main Authors: Kai-HsingChang, 張凱興
• Other Authors: Kuan-Zong Fung
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/73050018282925717036

碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 99 === SOFC have many advantages such as higher efficiency, low pollution, no noise, etc among several advanced energy technologies. In the structure of SOFC, ordered porous structure will enhance the transport of gas and then facilitate the electrochemical reaction. In this study, the macroporous Ni/YSZ cermet were fabricated by using PMMA microspheres as a template and Ni(CH3COO)2 methanol solution as a nickel source. The monodisperse PMMA spheres were filled with NiO/YSZ precursor solution by impregnation method. Subsequently, NiO/YSZ with ordered and porous structure was obtained by removing the PMMA spheres followed heat treatment from 800oC to 1100oC. In this study, the effect of heat-treatment temperature and the reducing atmosphere on the macroporous structure of NiO/YSZ was discussed. The result shows that the diameter of PMMA spheres were 0.15μm、0.3μm、0.5μm and 1μm which were fabricated successfully using emulsifier-free emulsion polymerization method. PMMA microspheres were used as the template of macroporous structure. According to the analysis of TG/DTA. The PMMA spheres had significant exothermic curve from 260oC to 380oC and apparent loss of weight at about 260oC. The loss of weight reached 100% at 380oC matched the results of DTA. After calcining at 1100oC for 4 hours, the macroporous structure of NiO/YSZ collapsed due to the minimization of surface tension. However, the macroporous structure of NiO/YSZ remained stable at 1000oC. Due to the volume reduction accompanied the reduction of NiO into metallic Ni, the strength of macroporous Ni/YSZ is lower than its oxide counterpart. When using the PMMA spheres with diameter of 0.3μm and 0.5μm spheres as template, the 3-D ordered macroporoud structure with diameters of 0.15μm and 0.37μm was obtained. The BET specific surface area of macroporous Ni/YSZ with pore diameter of 0.15μm and 0.37μm was found to be 21.64m2/g and 15.32 m2/g. Results of the methane reforming over the catalyst showed that the conversion increased with the operating temperature from 600oC to 900oC. The Ni/YSZ with the smaller pore size had the excellent methane conversion rate due to the catalyst on the support with the smaller pore size and large surface area. Thus, macroporous Ni/YSZ catalyst possessed higher activity. The methane conversion of anode Ni/YSZ fabricated from 300nm PMMA spheres achieved 79% at 900oC. The metallic conductivity in Ni/YSZ cermet was increased with the vol.% of NiO to YSZ. From the results could observed that the vol.% of NiO to YSZ equal to 100%, the Ni/YSZ specimen exhibited a conductivity value 55.94 Scm-1 at room temperature improved the electrical property of 90vol.% NiO to YSZ was 0.44Scm-1. The nickel content in Ni/YSZ increased the contact point between the two neighboring grains or interconnectivity between the grains increased and it resulted in highering in the conductivity of the specimen. The pore occupied the space where actually nickel particles would have been to provide electron connection.