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Aman, Nurul Ashikin Mohd Nazrul,Muchtar, Andanastuti,Rosli, Masli Irwan,Baharuddin, Nurul Akidah,Somalu, Mahendra Rao,Kalib, Noor Shieela The Korean Electrochemical Society 2020 Journal of electrochemical science and technology Vol.11 No.2
Solid oxide fuel cells (SOFCs) are among one of the promising technologies for efficient and clean energy. SOFCs offer several advantages over other types of fuel cells under relatively high temperatures (600℃ to 800℃). However, the thermal behavior of SOFC stacks at high operating temperatures is a serious issue in SOFC development because it can be associated with detrimental thermal stresses on the life span of the stacks. The thermal behavior of SOFC stacks can be influenced by operating or material properties. Therefore, this work aims to investigate the effects of the thermal conductivity of each component (anode, cathode, and electrolyte) on the thermal behavior of samarium-doped ceria-based SOFCs at intermediate temperatures. Computational fluid dynamics is used to simulate SOFC operation at 600℃. The temperature distributions and gradients of a single cell at 0.7 V under different thermal conductivity values are analyzed and discussed to determine their relationship. Simulations reveal that the influence of thermal conductivity is more remarkable for the anode and electrolyte than for the cathode. Increasing the thermal conductivity of the anode by 50% results in a 23% drop in the maximum thermal gradients. The results for the electrolyte are subtle, with a ~67% reduction in thermal conductivity that only results in an 8% reduction in the maximum temperature gradient. The effect of thermal conductivity on temperature gradient is important because it can be used to predict thermal stress generation.
Daud, Siti Mariam,Daud, Wan Ramli Wan,Kim, Byung Hong,Somalu, Mahendra Rao,Bakar, Mimi Hani Abu,Muchtar, Andanastuti,Jahim, Jamaliah Md,Lim, Swee Su,Chang, In Seop Elsevier 2018 ELECTROCHIMICA ACTA Vol.259 No.-
<P><B>Abstract</B></P> <P>Ceramic membranes (CMs) with different pore sizes (0.14 μm CM1, 150 kDa CM2 and 5 kDa CM3) were tested as separators in two-chamber microbial fuel cells (MFCs). The performance and ionic gradient concentration of MFCs using CMs were compared with that of cation exchange membrane (CEM), Nafion 117. MFC with CMs exhibited a higher performance than that of CEM under batch operation. The highest power density of 1790 ± 60 mW/m<SUP>2</SUP>, columbic efficiency (CE) of 41 ± 10% and internal resistance of 102 ± 13 Ω were obtained for MFC with CM3 under batch mode operation. The highest power density, columbic efficiency and internal resistance of MFC with CEM were found to be 1225 ± 20 mW/m<SUP>2</SUP>, 21 ± 1% and 400 ± 10 Ω, respectively. The highest performance of MFC with CM3 was expected due to a higher porosity of CM3 (13.8%) compared with that of CM1 (11.0%) and CM2 (11.05%). MFCs operated with catholyte containing salt solution, phosphate buffer basal medium without carbon source and yeast extract (PBBM-SA), generated lower current than with phosphate buffer (PB) as catholyte. This difference was more significant in the MFCs with the CEM Nafion 117 than with ceramic membranes. The non-selective porous ceramic membranes improved the diffusion of protons in the presence of other high concentration cations and resulted in MFC with higher performance. Hence, the porous ceramic membrane is a potential candidate separator for the development of commercial scale MFCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Porous ceramics were tested as separators in two-chamber microbial fuel cell (MFC). </LI> <LI> MFC with porous ceramic membrane showed a higher power density than that of PEM. </LI> <LI> The main issue with PEM is higher cation transfer compared to proton in MFC. </LI> <LI> The non-selective porous ceramic membranes improved the diffusion of proton in MFC. </LI> <LI> The PBBM supported the electrochemically active bacteria growth in anode chamber. </LI> </UL> </P>
C.K. Ng,S. Ramesh,C.Y. Tan,C.Y. Ching,N. Lwin,A. Muchtar 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.5
In the present work, the effect of manganese oxide (MnO2) additions (0, 0.5, 1 and 5 wt%) on the properties of ceria-dopedscandia stabilized zirconia (10Sc1CeSZ) was investigated over the temperature range of 1400 oC to 1550 oC. The results showedthat the addition up to 1 wt% had negligible effect on the mechanical properties of the ceramic. The samples containing upto 1 wt% MnO2 attained above 97.5% relative density, Vickers hardness of 13-14 GPa and fracture toughness of about3 MPam1/2. In addition, it was revealed that the 0.5 wt% MnO2 addition was beneficial in suppressing the cubic zirconia graingrowth i.e. the highest average grain size was measured at 4.9 µm when sintered at 1550 oC as compared to 9.9 µm measuredfor the undoped zirconia when sintered at the same temperature. On the other hand, the addition of 5 wt% MnO2 was foundto be detrimental to the densification and properties of the zirconia, particularly when sintered at higher temperatures. Thiswas attributed to the accelerated grain growth of the doped samples, i.e. the grain size increased by 2 fold, to 18.6 µm whensintered at 1550 oC.