The Experts below are selected from a list of 20109 Experts worldwide ranked by ideXlab platform
Alexandra Navrotsky - One of the best experts on this subject based on the ideXlab platform.
-
systematics of phase transition and mixing energetics in rare earth yttrium and scandium stabilized Zirconia and hafnia
Journal of the American Ceramic Society, 2007Co-Authors: Petra Simoncic, Alexandra NavrotskyAbstract:Energetics of rare earth, yttrium, and scandium stabilized Zirconia and hafnia have been systematically investigated by oxide melt solution calorimetry. The enthalpies of formation with respect to the oxide end members were simultaneously fit to a quadratic function to extract interaction parameters and enthalpies of transition of the oxide end members to the fluorite structure. ZrO 2 -SmO 1.5 and HfO 2 -SmO 1.5 show the most exothermic enthalpies of formation and interaction parameters, whereas ZrO 2 -ScO 1.5 has the least exothermic enthalpy of formation and interaction parameter. This suggests that the ZrO 2 -ScO 1.5 system shows the least short range order among all investigated systems, consistent with its high ionic conductivity. The extrapolated enthalpy of transition of the rare earth oxide end members to the cubic fluorite structure increase to more endothermic values with decreasing cation size. The γ-cubic fluorite phase transition in ZrO 2 -ScO 1.5 was investigated by differential scanning calorimetry (DSC). The phase transition is reversible, occurs at 1000°-1200'C and shows hysteresis (∼100°C). The enthalpy of transition is endothermic on heating and increases from 1.7±0.1 kJ/mol (22 mol% ScO 1.5 ) to 2.9±0.2 kJ/mol (30 mol% ScO 1.5 ).
Petra Simoncic - One of the best experts on this subject based on the ideXlab platform.
-
systematics of phase transition and mixing energetics in rare earth yttrium and scandium stabilized Zirconia and hafnia
Journal of the American Ceramic Society, 2007Co-Authors: Petra Simoncic, Alexandra NavrotskyAbstract:Energetics of rare earth, yttrium, and scandium stabilized Zirconia and hafnia have been systematically investigated by oxide melt solution calorimetry. The enthalpies of formation with respect to the oxide end members were simultaneously fit to a quadratic function to extract interaction parameters and enthalpies of transition of the oxide end members to the fluorite structure. ZrO 2 -SmO 1.5 and HfO 2 -SmO 1.5 show the most exothermic enthalpies of formation and interaction parameters, whereas ZrO 2 -ScO 1.5 has the least exothermic enthalpy of formation and interaction parameter. This suggests that the ZrO 2 -ScO 1.5 system shows the least short range order among all investigated systems, consistent with its high ionic conductivity. The extrapolated enthalpy of transition of the rare earth oxide end members to the cubic fluorite structure increase to more endothermic values with decreasing cation size. The γ-cubic fluorite phase transition in ZrO 2 -ScO 1.5 was investigated by differential scanning calorimetry (DSC). The phase transition is reversible, occurs at 1000°-1200'C and shows hysteresis (∼100°C). The enthalpy of transition is endothermic on heating and increases from 1.7±0.1 kJ/mol (22 mol% ScO 1.5 ) to 2.9±0.2 kJ/mol (30 mol% ScO 1.5 ).
Zongping Shao - One of the best experts on this subject based on the ideXlab platform.
-
a new carbon fuel cell with high power output by integrating with in situ catalytic reverse boudouard reaction
Electrochemistry Communications, 2009Co-Authors: Chunming Zhang, Ran Ran, Zongping ShaoAbstract:Abstract Solid carbon was investigated as the fuel for an intermediate-temperature solid oxide fuel cell (IT-SOFC). An innovative, indirect operating method involving internal catalytic gasification of carbon to gaseous carbon monoxide via the reverse Boudouard reaction (C(s) + CO 2 (g) → 2CO(g)) was proposed. The carbon gasification reaction rate was greatly enhanced by adopting Fe m O n –M x O (M = Li, K, Ca) as a catalyst. A peak power density of ∼297 mW cm −2 was achieved at 850 °C for an anode-supported SOFC with Scandium-Stabilized Zirconia electrolyte and a La 0.8 Sr 0.2 MnO 3 cathode by applying a catalyst-loaded, activated carbon as fuel. This peak power density was only modestly lower than that obtained using gaseous hydrogen as the fuel.
Zhang Jun - One of the best experts on this subject based on the ideXlab platform.
-
Electrolyte development for a SOFC operating at low temperature
Forschungszentrum Jülich GmbH Zentralbibliothek Verlag, 2020Co-Authors: Zhang JunAbstract:Solid oxide fuel cells (SOFCs) operating at low temperature ( 500 °C) enable applications, such as auxiliary power units (APUs) or portable devices. However, the state-of-the-art electrolyte material (yttria-stabilized Zirconia (YSZ)) used in intermediate-temperature SOFCs does not provide a sufficiently high ionic conductivity. Two approaches can therefore be taken to deal with that. First, an alternative electrolyte material to YSZ with a higher conductivity. However, when looking for alternatives, the conductivity values for each material found in widely-cited literature can be confusing, as the reported values are sometimes in conflict with each other. Second, an electrolyte film with thinner thickness. While spin coating is reported to be able to fabricate a YSZ electrolyte with thickness as thin as 1 μm, further thickness decrease by spin coating is a big challenge. Moreover, spin coating is very time consuming, needing multiple steps of coating, drying and heat-treatment, which could take several days. Therefore, in this study we present a systematic comparison of the conductivity of the three most popular electrolyte materials, i.e., YSZ, Scandium-Stabilized Zirconia (ScSZ), and gadolinium-doped ceria (GDC). Using electrochemical impedance spectroscopy (EIS) to characterize the ionic conductivity, we find that at 500 °C, GDC has a higher ionic conductivity (5.8e-3 S cm-1) than ScSZ (2.5e-3 S cm-1) and YSZ (1.1e-3 S cm-1). The properties of the starting powders, powder processing and the microstructure after sintering are all taken into account. Following up on this, a GDC electrolyte is developed on an industrial scale anode, with a dimension of 5 cmx5 cm, by screen printing. After sintering at 1400 °C for 5 h, a thin and dense GDC electrolyte, with thickness of 3.5 μm and air leakage rate of 3.54e-6 hPa dm2 s-1 cm-2, is achieved. The single cell test shows the cell has a high cell performance, a measured voltage of 0.84 V at a current density of 2Acm-2 and 750 °C (air,H2 with 10%H2O). According to the EIS, a quite low ohmic resistance is achieved, 125.2 milli ohm cm2 at 500 °C. This comparison of conductivity can be used as a guide when deciding on electrolyte materials for different SOFC applications, especially when the fabrication of the electrolyte layer of different thickness has to be considered, and rectify misleading information in the literature. The development of the thin and dense GDC electrolyte provides a strategy of using GDC as electrolyte for SOFC and confirms the advantage of using GDC while not YSZ for low temperature SOFC, which is the fabrication challenge can be decreased significantly
Chunming Zhang - One of the best experts on this subject based on the ideXlab platform.
-
a new carbon fuel cell with high power output by integrating with in situ catalytic reverse boudouard reaction
Electrochemistry Communications, 2009Co-Authors: Chunming Zhang, Ran Ran, Zongping ShaoAbstract:Abstract Solid carbon was investigated as the fuel for an intermediate-temperature solid oxide fuel cell (IT-SOFC). An innovative, indirect operating method involving internal catalytic gasification of carbon to gaseous carbon monoxide via the reverse Boudouard reaction (C(s) + CO 2 (g) → 2CO(g)) was proposed. The carbon gasification reaction rate was greatly enhanced by adopting Fe m O n –M x O (M = Li, K, Ca) as a catalyst. A peak power density of ∼297 mW cm −2 was achieved at 850 °C for an anode-supported SOFC with Scandium-Stabilized Zirconia electrolyte and a La 0.8 Sr 0.2 MnO 3 cathode by applying a catalyst-loaded, activated carbon as fuel. This peak power density was only modestly lower than that obtained using gaseous hydrogen as the fuel.
