Magneto-transport and magnetic susceptibility of SmFeAsO1-xFx (x = 0.0 and 0.20)

Bulk polycrystalline samples, SmFeAsO and the iso-structural superconducting SmFeAsO0.80F0.20 are explored through resistivity with temperature under magnetic field {\rho}(T, H), AC and DC magnetization (M-T), and Specific heat (Cp) measurements. The Resistivity measurement shows superconductivity for x = 0.20 sample with Tc(onset) ~ 51.7K. The upper critical field, [Hc2(0)] is estimated ~3770kOe by Ginzburg-Landau (GL) theory. Broadening of superconducting transition in magneto transport is studied through thermally activated flux flow in applied field up to 130 kOe. The flux flow activation energy (U/kB) is estimated ~1215K for 1kOe field. Magnetic measurements exhibited bulk superconductivity with lower critical field (Hc1) of ~1.2kOe at 2K. In normal state, the paramagnetic nature of compound confirms no trace of magnetic impurity which orders ferromagnetically. AC susceptibility measurements have been carried out for SmFeAsO0.80F0.20 sample at various amplitude and frequencies of applied AC drive field. The inter-granular critical current density (Jc) is estimated. Specific heat [Cp(T)] measurement showed an anomaly at around 140K due to the SDW ordering of Fe, followed by another peak at 5K corresponding to the antiferromagnetic (AFM) ordering of Sm+3 ions in SmFeAsO compound. Interestingly the change in entropy (marked by the Cp transition height) at 5K for Sm+3 AFM ordering is heavily reduced in case of superconducting SmFeAsO0.80F0.20 sample.Comment: 18 pages text + Figs: comments/suggestions welcome ([email protected]

An Ionic Molecular Glass as Electron Injection Layer for Efficient Polymer Light-Emitting Diode

An ionic molecular glass based on a dendronized monoammonium salt has been facilely synthesized and utilized as an interfacial electron-injection layer in a light-emitting diode (LED). The characterization of a yellow-green LED that involves an Al cathode and a thin layer of the new compound spin cast from a methanol solution has shown device performances comparable to those obtained with a Ba/Al cathode. Photovoltaic measurements under white light irradiation reveal that a thin layer of the new compound can significantly increase the built-in potential and thus facilitate electron injection from an Al cathode. Furthermore, it is interesting to observe that the new ionic salt could undergo reorganization on the emissive conjugated polymer layer, which leads to the formation of nearly uniform nanoaggregates

Influence of Stacking Fault Energy on the Microstructures and Grain Refinement in the Cu-Al Alloys during Equal-Channel Angular Pressing

The microstructural evolution and grain refinement of Cu-Al alloys with different stacking fault energies (SFEs) processed by equal-channel angular pressing (ECAP) were investigated. The grain refinement mechanism was gradually transformed from dislocation subdivision to twin fragmentation with tailoring the SFE of Cu-Al alloys. Concurrent with the transition of grain refinement mechanism, the grain size can be refined into from ultrafine region (1 m~100 nm) to the nanoscale (&lt;100 nm) and then it is found that the minimum equilibrium grain size decreases in a roughly linear way with lowering the SFE. Moreover, in combination with the previous results, it is proposed that the formation of a uniform ultrafine microstructure can be formed more readily in the materials with high SFE due to their high recovery rate of dislocations and in the materials with low SFE due to the easy formation of a homogeneously-twinned microstructure.</jats:p

Effects of design parameters on the performance of passive direct methanol fuel cells fed with concentrated fuel

Operating a passive direct methanol fuel cell (DMFC) with concentrated methanol is to achieve its inherently appealing feature of high specific energy. The objective of this work is to understand and identify key system design parameters that influence the performance of the passive DMFC operated with concentrated fuel at different operating temperatures. The design parameters that were investigated include the open ratios of the perforated polytetrafluoroethylene (PTFE) sheet, and the anode gas diffusion layers (GDL) and the cathode filters. Experimental results show that with the neat methanol operation, a medium open ratio is required to achieve high cell performance. It is interesting to find that unlike the passive DMFC operating with diluted fuel, an increase in the operating temperature from 40 to 60 degrees C results in a decrease in the cell performance due to water starvation. In addition, it is demonstrated that the anode GDL has little influence on the cell performance, but the effect of cathode filters is much more significant. Finally, the constant-current discharge test indicates that the supply of methanol becomes a key factor leading to performance degradation during the long-term operation. (C) 2014 Elsevier Ltd. All rights reserved

Application of Improved Interferometry on Low SNR Data to Auto-pick First Arrivals

Three improvements are added to the traditional super-virtual refraction interferometry. Inverse correlation functions are used to enhance the quality of near-offset traces. Interferometry in common-receiver gathers increases the stacking fold. Wavelet shaping effectively suppresses spurious events. The improved interferometry increases the SNR of first arrivals on both synthetic data and real exploration data. We then add two methods to distinguish the spurious events and real events on super-virtual data by event consecutiveness and inexistence of spurious events in raw data. With improved interferometry and improved auto-picking process, we can accurately auto-pick first arrivals over an expanded aperture of low SNR data.EI