Strong Pinning Enhancement in MgB2 Using Very Small Dy2O3 Additions

0.5 to 5.0 wt.% Dy2O3 was in-situ reacted with Mg + B to form pinned MgB2. While Tc remained largely unchanged, Jc was strongly enhanced. The best sample (only 0.5 wt.% Dy2O3) had a Jc of 6.5 x 10^5 A/cm^2 at 6K, 1T and 3.5 x 10^5 A/cm^2 at 20K, 1T, around a factor of 4 higher compared to the pure sample, and equivalent to hot-pressed or nano-Si added MgB2 at below 1T. Even distributions of nano-scale precipitates of DyB4 and MgO were observed within the grains. The room temperature resistivity decreased with Dy2O3 indicative of improved grain connectivity.Comment: 13 pages, 4 figures and 1 tabl

Raising Bi-O bands above the Fermi energy level of hole-doped Bi2_2Sr2_2CaCu2_2O8+δ_{8+\delta} and other cuprate superconductors

The Fermi surface (FS) of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212) predicted by band theory displays Bi-related pockets around the $(\pi,0)$ point, which have never been observed experimentally. We show that when the effects of hole doping either by substituting Pb for Bi or by adding excess O in Bi2212 are included, the Bi-O bands are lifted above the Fermi energy ($E_F$) and the resulting first-principles FS is in remarkable accord with measurements. With decreasing hole-doping the Bi-O bands drop below $E_F$ and the system self-dopes below a critical hole concentration. Computations on other Bi- as well as Tl- and Hg-based compounds indicate that lifting of the cation-derived band with hole doping is a general property of the electronic structures of the cuprates.Comment: 4 pages, 4 figures; PRL (2006, in press

Introducing creativity techniques and software apps to the care of people with dementia

This poster reports research to introduce creative problem solving techniques and software to the care for people with dementia in residential homes

Improved Current Densities in MgB2 By Liquid-Assisted Sintering

Polycrystalline MgB2 samples with GaN additions were prepared by reaction of Mg, B, and GaN powders. The presence of Ga leads to a low melting eutectic phase which allowed liquid phase sintering and produces plate-like grains. For low-level GaN additions (5% at. % or less), the critical transition temperature, Tc, remained unchanged and in 1T magnetic field, the critical current density, Jc was enhanced by a factor of 2 and 10, for temperatures of \~5K and 20K, respectively. The values obtained are approaching those of hot isostatically pressed samples.Comment: 12 pages, 1 table, 4 figures, accepted in Applied Physics Letter

Evaluating coefficient of performance and rate of moisture loss of some biomass humidifiers materials with a developed simple direct stand-alone evaporative cooling system for farmers

© 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)The purpose of this study was to investigate the feasibility of deploying direct evaporative cooler with Jute fiber, palm fruit mesocarp fiber and wooden charcoal as humidifier in Nigeria. High cost of imported evaporative coolers and humidifiers can discourage farmers and limited adoption of evaporative cooling technology. For this purpose an experimental direct evaporative cooling test rig was developed and assembled in south western Nigeria with biomass humidifier. The evaluation parameters were the humidifying efficiency, the rate of moisture loss, coefficient of performance and sensible heat ratio. The humidifier presented average cooling efficiency of 55.9 to 78.62 %, average rate of moisture loss of 1.37 × 10 -3 to 2.61 × 10 -3 kg/s, average COP of 8.48 to 23.42 (EER of 11 to 78) and average sensible heat ratio of 1.28 × 10 -4 to 4.06 × 10 -4 for the air velocity of 3.0 to 4.5 m/s. The obtain performance can be better in a dryer month or nearly impossible in a very wet month as the humidifying efficiency of direct evaporative coolers are found to diminish at high humidity. To avoid casting doubt on the effectiveness of direct evaporative cooler by farmers, it should only serve as stop gap preservation equipment and deployed during the favorable weather condition especially during the winter when the air is dry. These can be identified from the metrological charts of the chosen location.Peer reviewe

Thin-Film Trilayer Manganate Junctions

Spin-dependent conductance across a manganate-barrier-manganate junction has recently been demonstrated. The junction is a La$_{0.67}$Sr$_{0.33}$MnO$_3$% -SrTiO$_3$-La$_{0.67}$ Sr$_{0.33}$MnO$_3$ trilayer device supporting current-perpendicular transport. Large magnetoresistance of up to a factor of five change was observed in these junctions at 4.2K in a relatively low field of the order of 100 Oe. Temperature and bias dependent studies revealed a complex junction interface structure whose materials physics has yet to be understood.Comment: 20 pages, 14 figures. To appear in Phil. Trans. R. Soc. Lond. A vol.356 (1998

Lithium outdiffusion in LiTi<inf>2</inf>O<inf>4</inf> thin films grown by pulsed laser deposition

We report surface chemical cation composition analysis of high quality superconducting LiTi$_{2}$O$_{4}$ thin films, grown epitaxially on MgAl$_{2}$O$_{4}$ (111) substrates by pulsed laser deposition. The superconducting transition temperature of the films was ~13.8 K. Surface chemical composition is crucial for the formation of a good metal/insulator interface for integrating LiTi$_{2}$O$_{4}$ into full-oxide spin-filtering devices in order to minimize the formation of structural defects and increase the spin polarisation efficiency. In consideration of this, we report a detailed angle resolved x-ray photoelectron spectroscopy analysis. Results show Li segregation at the surface of LiTi$_{2}$O$_{4}$ films. We attribute this process due to outdiffusion of Li toward the outermost LiTi$_{2}$O$_{4}$ layers.The research leading to these results has received funding from the European Union Seventh Framework Programme ([FP7/2007–2013] [FP7/2007–2011]) under Grant agreement 316657 (SpinIcur), the European Research Council AdG (291442 “Superspin”), European Research Council AdG (247276 “NOVOX”) and the EPSRC (Equipment Account Grant EP/K035282/1).This is the final version of the article. It first appeared from Elsevier via https://doi.org/10.1016/j.jcrysgro.2016.09.01

Normal state properties of high angle grain boundaries in (Y,Ca)Ba2Cu3O7-delta

By lithographically fabricating an optimised Wheatstone bridge geometry, we have been able to make accurate measurements of the resistance of grain boundaries in Y1-xCaxBa2Cu3O7-d between the superconducting transition temperature, Tc, and room temperature. Below Tc the normal state properties were assessed by applying sufficiently high currents. The behaviour of the grain boundary resistance versus temperature and of the conductance versus voltage are discussed in the framework charge transport through a tunnel barrier. The influence of misorientation angle, oxygen content, and calcium doping on the normal state properties is related to changes of the height and shape of the grain boundary potential barrier.Comment: 17 pages, 1 table, 5 figures, submitted to PR