Comparison of the Magnetic Ordering in Sr2Yb1Ru0.9Cu0.1O6 and Ru1Sr2Gd1Cu2O8 Superconductors

Ru1Sr2Gd1Cu2O8 and Sr2Yb1Ru0.9Cu0.1O6 were synthesized using a solid-state reaction. X-ray diffraction showed that Ru 1Sr2Gd1Cu2O8 crystallized into the tetragonal Ru-1212 structure (space group P4/mmm), whereas the Sr 2Yb1Ru0.9Cu0.1O6 had a monoclynic structure (space group P21/n). Sr2Yb 1Ru0.9Cu0.1O6 showed a possible magnetic transition (T m a g ) at 44 K with a superconducting transition temperature T c at 30 K. In contrast, Ru 1Sr2Gd1Cu2O8 showed a magnetic transition at 140 K with a T c at 25 K. The magnetization data for Sr2Yb1Ru0.9Cu0.1O 6 suggests that this sample exhibits antiferromagnetic ordering in zero-field-cooled (ZFC) magnetization, whereas it reveals a weak ferromagnetic component during field-cooled (FC) cycles. In addition, larger diamagnetic signals were observed during FC cycle compared to the ZFC. These results suggest that the valence state of the Yb ion have a significant effect on the magnetic state of the Sr2Yb1Ru0.9Cu0.1O 6 superconductor. © 2014 Springer Science+Business Media New York.

Superconducting Properties in Y-doped Semimetallic Bi3O2S3 Superconductors

We report the superconducting properties of Y-doped semimetallic Bi3O2S3 superconductors. From electrical resistivity measurements, the T-c,(zero) of the optimally Y-doped Bi3O2S3 was higher than that of pure Bi3O2S3. This Y content dependence of the superconducting properties in Bi3O2S3 is explained by the chemical pressure effect

Design and Analysis of Cryogenic Cooling System for Electric Propulsion System Using Liquid Hydrogen

As the demand for eco-friendly energy increases, hydrogen energy and liquid hydrogen storage technologies are being developed as an alternative. Hydrogen has a lower liquefaction point and higher thermal conductivity than nitrogen or neon used in general cryogenic systems. Therefore, the application of hydrogen to cryogenic systems can increase efficiency and stability. This paper describes the design and analysis of a cryogenic cooling system for an electric propulsion system using liquid hydrogen as a refrigerant and energy source. The proposed aviation propulsion system (APS) consists of a hydrogen fuel cell, a battery, a power distribution system, and a motor. For a lab-scale 5 kW superconducting motor using a 2G high-temperature superconducting (HTS) wire, the HTS motor and cooling system were analyzed for electromagnetic and thermal characteristics using a finite element method-based analysis program. The liquid hydrogen-based cooling system consists of a pre-cooling system, a hydrogen liquefaction system, and an HTS coil cooling system. Based on the thermal load analysis results of the HTS coil, the target temperature for hydrogen gas pre-cooling, the number of buffer layers, and the cryo-cooler capacity were selected to minimize the thermal load of the hydrogen liquefaction system. As a result, the hydrogen was stably liquefied, and the temperature of the HTS coil corresponding to the thermal load of the designed lab-scale HTS motor was maintained at 30 K

Bendable BiVO4-Based Photoanodes on a Metal Substrate Realized through Template Engineering for Photoelectrochemical Water Splitting

Unlike planar photoelectrodes, bendable and malleable photoelectrodes extend their application to mechanical flexibility beyond conventional rigid structures, which have garnered new attention in the field of photoelectrochemical water splitting. A bendable metal (Hastelloy), which has both bendability and compatibility with various oxide layers, allows high-temperature processes for crystallization; therefore it is far superior as a substrate than a conventional flexible polymer. In this study, we fabricate bendable BiVO4 crystalline thin films on the metal substrates by employing template layers (SrRuO3/SrTiO3) to reduce the structural misfits between BiVO4 and the substrate. The crystallinities were verified through X-ray diffraction and transmission electron microscopy, and photocatalytic performances were examined. The crystallinity of BiVO4 was significantly improved by utilizing similar lattice constants and affinities between BiVO4 and the oxide template layers. We also formed a type II heterojunction by adding a WO3 layer which complements the charge separation and charge transfer as a photoanode. The photocurrent densities of tensile-bent BiVO4/WO3 thin films with a bending radius of 10 mm are comparable to those of pristine BiVO4/WO3 thin film in various aqueous electrolytes. Moreover, photostability tests showed that the tensile-bent crystalline photoanodes retained 90% of their initial photocurrent density after 24 h, which proved their exceptional durability. Our work demonstrates that the bendable photoelectrodes with crystallinity hold great potential in terms of device structure for solar-driven water splitting.11Nsciescopu