M.A. Faruk Öksüzömer

Ce0.8Sm0.2O1.9 synthesis for solid oxide fuel cell electrolyte by ultrasound assisted co-precipitation method

In this study, the synthesis of Ce(0.8)Sm(0.2)O(1.9) (SDC) solid electrolyte by the ultrasound assisted co-precipitation method was accomplished to explore the effects of ultrasound power, ultrasound pulse ratio and probe type upon the ionic conductivity of SDC as well as the lattice parameter, the microstructure and the density. Fine powders of uniform crystallite sizes (average 11.70±0.62nm) were obtained, needing lower sintering temperature. The SDC powders were successfully sintered to a relative density of over 95% at 1200°C (5°Cmin(-1)) for 6h. The micrograph of SDC pellets showed non-agglomerated and well-developed grains with average size of about 200nm. X-ray diffraction analysis showed that the lattice parameter increased with increasing acoustic intensity and reached a maximum for the 14.94Wcm(-2). Further, a linear relationship was detected between the lattice parameter and the ionic conductivity, inspiring a dopant like effect of US on the electrolyte properties. The highest ionic conductivity as σ(800°C)=3.07×10(-2)Scm(-1) with an activation energy E(a)=0.871kJmol(-1) was obtained with pulsed ultrasound for an acoustic intensity of 14.94Wcm(-2), using 19mm probe and 8:2 pulse ratio.

Studies on oxidative coupling of methane using Sm2O3-based catalysts

Abstract The effects of Mn/Na2WO4, Li, and CaO loading on the monoclinic Sm2O3 catalyst were investigated for the oxidative coupling of methane using O2 or N2O as an oxidant. The catalysts were prepared by wet impregnation method and characterized by XRD, BET, CO2-TPD, and XPS analysis. Impregnation of Mn/Na2WO4 on monoclinic Sm2O3 resulted in the formation of Sm2−xMnxO3 phase, decreasing the catalytic performance. Li impregnation increased the C2 selectivity but decreased the catalytic activity. The SmLiO2 formation increased the catalytic activity and selectivity. High amounts of CaO impregnation increased the C2 selectivity of monoclinic Sm2O3 without a loss in catalytic activity. 6Li/m-Sm2O3 were found unstable due to the Li loss from the catalyst. The 15CaO/m-Sm2O3 was quite stable and showed 8.2% ethylene yield with N2O use, much higher than that was obtained with the well-known 2Mn/5Na2WO4/SiO2 and 4Li/MgO catalysts. N2O was more selective than O2 as an oxidant and enhanced ethylene formation.