Calcium manganite as oxygen electrode materials for reversible solid oxide fuel cell

The authors thank EPSRC for funding under the contract of H2FC hub EPSRC: EP/J016454/1 and Platform EPSRC: EP/K006800/1 and JTSI thanks Wolfson Merit of Royal Society: WRMA 2012/R2For an efficient high-temperature reversible solid oxide fuel cell (RSOFC), the oxygen electrode should be highly active for the conversion between oxygen anions and oxygen gas. CaMnO3-δ(CM) is a perovskite that can be readily reduced with the formation of Mn3+ giving rise to oxygen defective phases. CM is examined here as the oxygen electrode for a RSOFC. CaMn0.9Nb0.1O3-δ (CMN) with Nb doping shows superior electric conductivity (125 S cm-1 at 700 ºC) to CM (1-5 S cm-1 at 700 ºC) in air and is also examined for comparison. X-ray diffraction (XRD) data show that CM and CMN are compatible with the widely used yttria-stabilized zirconia (YSZ) electrolyte up to 950 oC. Both materials show a thermal expansion coefficient (TEC) close to 10.8-10.9 ppm K-1 in the temperature range between 100-750 ºC, compatible with that of YSZ. Polarization curves and electrochemical impedance spectra for both fuel cell and steam electrolysis modes were investigated at 700 ºC, showing that CM presented a polarization resistance of 0.059 Ωcm2 under a cathodic bias of -0.4 V while CMN gave a polarization resistance of 0.081 Ω cm2 under an anodic bias of 0.4 V. The phase stability up to 900 ºC of these materials was investigated with thermogravimetric analysis (TGA) and variable temperature XRD.Publisher PDFPeer reviewe

High-performance and durable alcohol-fueled symmetrical solid oxide fuel cell based on ferrite perovskite electrode

This work is supported by the NSFC (grant No. 51702264; 41371275) and National Key Research and Development Program of China (grant No. 2018FYD0200701) and research funding for central universities (XDJK2020B066). C.N. also thanks to the award of Chongqing Bayu Young Scholar from Chongqing Teaching Committee and Funding for Oversea Returnees, while J.N. thanks to the support from Chongqing Yingcai Talent.A solid oxide fuel cell utilizing bio-fuels such as methanol and ethanol could provide a carbon–neutral electricity generation and facilitate its applications in transport or stationary power unit. Herein, Ce4+ doping in SrFe0.95Ni0.05O3 imparts FeNi3 exsolution and CeO2 precipitation in a reducing condition, contributing to the fuel reforming, C-C bond cleavage and coke consumption in the anode chamber. The ferrite perovskites are stable in ethanol/steam at 800 °C, whereas they are unstable in ethanol vapor with the high C fugacity inducing the formation of Fe0 and carbides. However, the Ce0.2Sr0.8Fe0.95Ni0.05O3 anode maintains mostly the perovskite and is free from coke after the 300 h’ operation under C2H5OH fuel at 0.5 V or 0.7 V because of the dynamic balance between the carbon deposition and consumption since an operation for 10 h shows a clear carbon deposition. A maximum power density of 0.58 W cm−2 and a polarization resistance of 0.21 Ω cm2 at 800 °C can be obtained for the symmetrical solid oxide fuel cell with identical Ce0.2Sr0.8Fe0.95Ni0.05O3 cathode and anode under an ethanol fuel. The results demonstrate that the reversible and stable SrFeO3 with Ce/Ni co-doping has a bright prospect for alcohol fuel oxidation.PostprintPostprintPeer reviewe

Discovery of a rapid, luminous nova in NGC 300 by the KMTNet Supernova Program

We present the discovery of a rapidly evolving transient by the Korean Microlensing Telescope Network Supernova Program (KSP). KSP is a novel high-cadence supernova survey that offers deep ($\sim21.5$ mag in $BVI$ bands) nearly continuous wide-field monitoring for the discovery of early and/or fast optical transients. KSP-OT-201509a, reported here, was discovered on 2015 September 27 during the KSP commissioning run in the direction of the nearby galaxy NGC~300, and stayed above detection limit for $\sim$ 22 days. We use our $BVI$ light-curves to constrain the ascent rate, $-3.7(7)$ mag day$^{-1}$ in $V$, decay time scale, $t^{V}_{2}=1.7(6)$ days, and peak absolute magnitude, $-9.65\leq M_{V}\leq -9.25$ mag. We also find evidence for a short-lived pre-maximum halt in all bands. The peak luminosity and lightcurve evolution make KSP-OT-201509a consistent with a bright, rapidly decaying nova outburst. We discuss constraints on the nature of the progenitor and its environment using archival HST/ACS images and conclude with a broad discussion on the nature of the system.Comment: 7 pages in aastex6 two-column format, 4 figures; accepted in Ap

Endogenous asymmetric information and international equity home bias: The effects of portfolio size and information costs

Equity home bias is one of the major puzzles in international finance. This paper investigates the impact of asymmetric information on equity home bias in a rational expectation model where portfolio managers differ in their levels of initial portfolio size and information acquisition is endogenous. The model characterizes the information acquisition and investment decisions made by each portfolio manager, and the resulting equilibrium. We find that portfolio managers with larger portfolio size acquire information about the foreign asset; this is consistent with new evidence linking the degree of home bias across portfolio managers to portfolio size

Image analysis and modeling of the orientation of pores in a constrained film on a rigid substrate

The authors thank EPSRC and ONR for funding.The nature of porosity in functional materials is often a critical parameter in determining their functionality, for example, in structure materials and fuel cell electrodes. Here, we study the development of the anisotropy of porous yttria-stabilized zirconia (YSZ), focusing particularly upon the contribution of pore orientation to this anisotropy. Simulation from when the ink is deposited on the surface of a rigid substrate shows that platelike pores are found tend to align along the transverse direction of the substrate. Cross-sectional image analysis of the pores from the attendant pores of YSZ particles or pore-forming agent (PFA) matches with the simulated modeling when materials transport is insignificant in determining the shape of pores. The anisotropy created in the densification stage is separated from that in the green body by analyzing the image of porous structures formed with spherical glassy carbon which is unable to contribute to anisotropy during green-state processing.PostprintPeer reviewe

An Optical Tweezer Array of Ultracold Molecules

Arrays of single ultracold molecules promise to be a powerful platform for many applications ranging from quantum simulation to precision measurement. Here we report on the creation of an optical tweezer array of single ultracold CaF molecules. By utilizing light-induced collisions during the laser cooling process, we trap single molecules. The high densities attained inside the tweezer traps have also enabled us to observe in the absence of light molecule-molecule collisions of laser cooled molecules for the first time

Strength of Gamma Rhythm Depends on Normalization

Neuronal assemblies often exhibit stimulus-induced rhythmic activity in the gamma range (30–80 Hz), whose magnitude depends on the attentional load. This has led to the suggestion that gamma rhythms form dynamic communication channels across cortical areas processing the features of behaviorally relevant stimuli. Recently, attention has been linked to a normalization mechanism, in which the response of a neuron is suppressed (normalized) by the overall activity of a large pool of neighboring neurons. In this model, attention increases the excitatory drive received by the neuron, which in turn also increases the strength of normalization, thereby changing the balance of excitation and inhibition. Recent studies have shown that gamma power also depends on such excitatory–inhibitory interactions. Could modulation in gamma power during an attention task be a reflection of the changes in the underlying excitation–inhibition interactions? By manipulating the normalization strength independent of attentional load in macaque monkeys, we show that gamma power increases with increasing normalization, even when the attentional load is fixed. Further, manipulations of attention that increase normalization increase gamma power, even when they decrease the firing rate. Thus, gamma rhythms could be a reflection of changes in the relative strengths of excitation and normalization rather than playing a functional role in communication or control