Ultrathin petal-like NiAl layered double oxide/sulfide composites as an advanced electrode for high-performance asymmetric supercapacitors

Layered double hydroxide (LDH) is an important layer-structured material for supercapacitors because of its versatile compositions, high theoretical capacitance, environmental friendliness, and low cost. However, the high resistivity of this material results in capacity fading, limiting its application in energy storage. Herein, we develop a facile approach to synthesize ultrathin petal-like NiAl layered double oxide/sulfide (LDO/LDS) composites with high electrochemical activity using hydrothermal reaction followed by sulfidation process. Scanning electron micrograph shows that the petal-like NiAl LDO/LDS composites are as thin as ~10 nm with a mean lateral dimension of ~1 µm. The NiAl LDO/LDS electrode delivers remarkably high specific capacitance of 2250.5 F g−1 at 1 A g−1 compared with that of NiAl LDH (1740.5 F g−1 at 1 A g−1) and possesses good cycling ability of 88.9% capacitance retention over 5000 cycles at 5 A g−1. Asymmetric supercapacitor (ASC) is fabricated using NiAl LDO/LDS and graphene as positive and negative electrodes, respectively. NiAl LDO/LDS//G ASC exhibits specific capacitance of 153.3 F g−1 at 1 A g−1, high energy density of 47.9 Wh kg−1 at a power density of 750 W kg−1, and reliable cycling stability of 95.68% capacitance retention after 5000 cycles. Results highlight that NiAl LDO/LDS composites are promising materials for energy storage devices with long cycling stability

Facile synthesis of NiAl layered double hydroxide nanoplates for high-performance asymmetric supercapacitor

Layered double hydroxide (LDH) is a promising electrode material for supercapacitor owing to its versatility in compositions, high theoretical capacitance, environmental benignity, and low cost. However, capacity fading of LDH hinders its application in energy storage. Herein, we develop a facile approach to synthesize NiAl-LDH nanoplates possessing high electrochemical activity and desirable morphology to improve ion diffusion kinetics and reduce charge transfer resistance, leading to enhanced specific capacitance compared to pristine NiAl-LDH. Scanning electron microscopy shows that the LDH nanoplates are as thin as ∼30 nm with a mean lateral dimension of ∼150 nm. The NiAl-LDH nanoplates electrode delivers remarkably high specific capacitance of 1713.2 F g−1 at 1 A g−1 and good cycling ability of 88% capacitance retention over 5000 cycles compared to only 757.1 F g−1 at 1 A g−1 and 76.4% of the pristine NiAl-LDH. An asymmetric supercapacitor (ASC) is assembled using NiAl-LDH nanoplates and graphene as positive and negative electrodes, respectively. The ASC operating at 1.4 V delivers a high specific capacitance of 125 F g−1 at 1 A g−1 with a high energy density of 34.1 Wh kg−1 at a power density of 700 W kg−1 and outstanding cyclic stability (91.8% capacitance retention after 5000 cycles)

Nematic topological superconducting phase in Nb-doped Bi2Se3

A nematic topological superconductor has an order parameter symmetry, which spontaneously breaks the crystalline symmetry in its superconducting state. This state can be observed, for example, by thermodynamic or upper critical field experiments in which a magnetic field is rotated with respect to the crystalline axes. The corresponding physical quantity then directly reflects the symmetry of the order parameter. We present a study on the superconducting upper critical field of the Nb-doped topological insulator NbxBi2Se3 for various magnetic field orientations parallel and perpendicular to the basal plane of the Bi2Se3 layers. The data were obtained by two complementary experimental techniques, magnetoresistance and DC magnetization, on three different single crystalline samples of the same batch. Both methods and all samples show with perfect agreement that the in-plane upper critical fields clearly demonstrate a two-fold symmetry that breaks the three-fold crystal symmetry. The two-fold symmetry is also found in the absolute value of the magnetization of the initial zero-field-cooled branch of the hysteresis loop and in the value of the thermodynamic contribution above the irreversibility field, but also in the irreversible properties such as the value of the characteristic irreversibility field and in the width of the hysteresis loop. This provides strong experimental evidence that Nb-doped Bi2Se3 is a nematic topological superconductor similar to the Cu- and Sr-doped Bi2Se3

PowerCore: a program applying the advanced M strategy with a heuristic search for establishing core sets

AbstractMotivation: Core sets are necessary to ensure that access to useful alleles or characteristics retained in genebanks is guaranteed. We have successfully developed a computational tool named 'PowerCore' that aims to support the development of core sets by reducing the redundancy of useful alleles and thus enhancing their richness.Results: The program, using a new approach completely different from any other previous methodologies, selects entries of core sets by the advanced M (maximization) strategy implemented through a modified heuristic algorithm. The developed core set has been validated to retain all characteristics for qualitative traits and all classes for quantitative ones. PowerCore effectively selected the accessions with higher diversity representing the entire coverage of variables and gave a 100% reproducible list of entries whenever repeated.Availability: PowerCore software uses the .NET Framework Version 1.1 environment which is freely available for the MS Windows platform. The files can be downloaded from http://genebank.rda.go.kr/powercore/. The distribution of the package includes executable programs, sample data and a user manual.Contact: [email protected]

High-performance solid-state flexible supercapacitor based on reduced graphene oxide/hierarchical core-shell Ag nanowire@NiAl layered double hydroxide film electrode

All-solid-state flexible supercapacitor (AFSC) is a promising energy storage device due to its high flexibility, security, and environmental friendliness. However, high electrical resistance and low specific capacitance of electrodes limit its application for potential portable electronic devices. In this study, we design a novel hybrid film electrode composed of reduced graphene oxide (rGO)/silver nanowire (Ag NW)@nickel aluminum layered double hydroxide (NiAl LDH; herein, GAL) possessing high electrochemical performance by using hydrothermal and vacuum filtration techniques. The Ag NW@NiAl LDH (AL) composites with hierarchical core-shell structure are utilized to increase electroactive surface area and improve electrical conductivity, while the rGO nanosheets serve as a prominent carbon material with outstanding electrical conductivity and mechanical flexibility. The freestanding GAL electrode shows high specific capacitance of 1148 F g−1 at 1 A g−1 compared with rGO/NiAl LDH (GL) of 765.2 F g−1 at 1 A g−1. Furthermore, the bind-free symmetric AFSC device is successfully prepared using GAL hybrid film as electrodes and PVA-KOH as solid-state gel electrolyte. The GAL//GAL AFSC device delivers a superior specific capacitance of 127.2 F g−1 at 1 A g−1, a high energy density of 35.75 mWh cm−3 at a power density of 1.01 W cm−3, and great cycling ability of 83.2% over 10,000 cycles at 5 A g−1. This study introduces a novel design of flexible electrode structure for advanced energy storage applications

Control Upstream Austenite Grain Coarsening during Thin Slab Casting Direct Rolling (TSCDR) Process

Thin-slab cast direct-rolling (TSCDR) has become a major process for flat-rolled production. However, the elimination of slab reheating and limited number of thermomechanical deformation passes leave fewer opportunities for austenite grain refinement, resulting in some large grains persisting in the final microstructure. In order to achieve excellent ductile to brittle transition temperature (DBTT) and drop weight tear test (DWTT) properties in thicker gauge high-strength low-alloy products, it is necessary to control austenite grain coarsening prior to the onset of thermomechanical processing. This contribution proposes a suite of methods to refine the austenite grain from both theoretical and practical perspectives, including: increasing cooling rate during casting, liquid core reduction, increasing austenite nucleation sites during the delta-ferrite to austenite phase transformation, controlling holding furnace temperature and time to avoid austenite coarsening, and producing a new alloy with two-phase pinning to arrest grain coarsening. These methodologies can not only refine austenite grain size in the slab center, but also improve the slab homogeneity

Multiphysics analysis of heat pipe cooled microreactor core with adjusted heat sink temperature for thermal stress reduction using OpenFOAM coupled with neutronics and heat pipe code

Heat-pipe-cooled microreactors (HPRs) have advantages such as a compact design, easy transportation, and improved system reliability and stability. The core of an HPR consists of fuel rods and heat pipes in a monolith, which is a solid block structure containing many holes for the fuel rods and heat pipes. When designing the core of an HPR, high thermal stress and reactivity feedback owing to thermal expansion are important considerations. Therefore, a high-fidelity multiphysics analysis tool is required for accurately analyzing an HPR core. When performing a multiphysics analysis, it is necessary to couple the heat pipe thermal analysis code, thermal-structural analysis code, and neutronics code. To develop a multiphysics analysis tool, OpenFOAM, an open source Computational Fluid Dynamics (CFD) tool, and ANLHTP, a heat pipe thermal analysis code, were coupled. In this process, the structural analysis solver of OpenFOAM was verified, and its limitations were improved. To confirm the proper working of the code, the mini-core problem was analyzed using the OpenFOAM-ANLHTP coupled code. Next, to consider the reactivity feedback, coupling with PRAGMA, a GPU-based continuous-energy-Monte Carlo neutronics code was performed, and the multiphysics analysis capability of the OpenFOAM-ANLHTP-PRAGMA coupled code was confirmed through an analysis of the MegaPower reactor core. To reduce the temperature distribution within the monolith, the temperature distribution of the heat pipe sink was adjusted, and the reduced thermal stress of an HPR core was observed

Knowledge, attitude and practice towards sexual and reproductive health including comprehensive sexuality education among first year students of university Malaysia Sabah (UMS), Malaysia

This study aims to assess knowledge, attitude and behavior in sexual and reproductive health (SRH) including comprehensive sexuality education (CSE) among 439 first year students; 213 sciences and 226 arts students from 5 Faculties of University Malaysia Sabah (2016-2017). Exposure of Malaysian students to sexual education is limited to science subjects which are only being taught at upper elementary and secondary high school levels. Arts students are less exposed to sexual education across Malaysia as it is delivered in Basic Science subject only. It was a university-based, cross-sectional, descriptive study. Pretested self- administered questionnaire was anonymously completed by all participants and was conducted from November 2016 to January 2017. Students’ demographic characteristics from Science and Arts streams were same except females, Sabah ethnics and Malays were more in Arts. Awareness of HIV/AIDS, Condom, Wet dream, COC pills and abortion services were more in Science students and statistically significant. 34.3 % and 81.2% of Science students agreed that CSE should be introduced in primary and secondary school but not statistically significant. 22 out of 439 students were sexually active. Science students had more knowledge about SRH and favourable attitude towards sexuality education but less favourable behaviour of watching and reading pornographic materials. It was concluded that there were gaps in knowledge, attitude and behaviour of SRH and need to remedy these by giving appropriate CSE classes to first-year university students in an elective module according to their culture and religious beliefs in accord with International Technical Guidance on Sexuality Education (ITGSE)