Electronic structures of [111]-oriented free-standing InAs and InP nanowires

We report on a theoretical study of the electronic structures of the [111]-oriented, free-standing, zincblende InAs and InP nanowires with hexagonal cross sections by means of an atomistic $sp^{3}s^{*}$, spin-orbit interaction included, nearest-neighbor, tight-binding method. The band structures and the band state wave functions of these nanowires are calculated and the symmetry properties of the bands and band states are analyzed based on the $C_{3v}$ double point group. It is shown that all bands of these nanowires are doubly degenerate at the $\Gamma$-point and some of these bands will split into non-degenerate bands when the wave vector $k$ moves away from the $\Gamma$-point as a manifestation of spin-splitting due to spin-orbit interaction. It is also shown that the lower conduction bands of these nanowires all show simple parabolic dispersion relations, while the top valence bands show complex dispersion relations and band crossings. The band state wave functions are presented by the spatial probability distributions and it is found that all the band states show $2\pi/3$-rotation symmetric probability distributions. The effects of quantum confinement on the band structures of the [111]-oriented InAs and InP nanowires are also examined and an empirical formula for the description of quantization energies of the lowest conduction band and the highest valence band is presented. The formula can simply be used to estimate the enhancement of the band gaps of the nanowires at different sizes as a result of quantum confinement.Comment: 9 pages, 8 figures. arXiv admin note: substantial text overlap with arXiv:1502.0756

Design and fabrication of whisker hybrid ceramic membranes with narrow pore size distribution and high permeability via co-sintering process

Ceramic microfiltration membranes (MF) with narrow pore size distribution and high permeability are widely used for the preparation of ceramic ultrafiltration membranes (UF) and in wastewater treatment. In this work, a whisker hybrid ceramic membrane (WHCM) consisting of a whisker layer and an alumina layer was designed to achieve high permeability and narrow pore size distribution based on the relative resistance obtained using the Hagen-Poiseuille and Darcy equations. The whisker layer was designed to prevent the penetration of alumina particles into the support and ensure a high porosity of the membrane, while the alumina layer provided a smooth surface and narrow pore size distribution. Mass transfer resistance is critical to reduce the effect of the membrane layers. It was found that the resistance of the WHCM depended largely on the alumina layer. The effect of the support and whisker layer on the resistance of the WHCM was negligible. This was consistent with theoretical calculations. The WHCM was co-sintered at 1000 °C, which resulted in a high permeability of ~ 645 L m−1 h−1 ;bar−1 and a narrow pore size distribution of ~ 100 nm. Co-sintering was carried out on a macroporous ceramic support (just needed one sintering process), which greatly reduced the preparation cost and time. The WHCM (as the sub-layer) also showed a great potential to be used for the fabrication of ceramic UF membranes with high repeatability. Hence, this study provides an efficient approach for the fabrication of advanced ceramic MF membranes on macroporous supports, allowing for rapid prototyping with scale-up capability

New Technology and Experimental Study on Snow-Melting Heated Pavement System in Tunnel Portal

In recent years, with the rapid growth of economy and sharp rise of motor vehicles in China, the pavement skid resistance in tunnel portals has become increasingly important in cold region. However, the deicing salt, snow removal with machine, and other antiskid measures adopted by highway maintenance division have many limitations. To improve the treatment effect, we proposed a new snow-melting approach employing electric heat tracing, in which heating cables are installed in the structural layer of road. Through the field experiment, laboratory experiment, and numerical investigation, structure type, heating power, and preheating time of the flexible pavement heating system in tunnel portal were systematically analyzed, and advantages of electric heat tracing technology in improving the pavement skid resistance in tunnel portal were also presented. Therefore, such new technology, which offers new snow-melting methods for tunnel portal, bridge, mountainous area, and large longitudinal slope in cold region, has promising prospect for extensive application

Thermal conductivity of MgO in giant planetary interior conditions predicted by deep potential

Thermal conductivity $\kappa$ of MgO plays a fundamental role in understanding the thermal evolution and mantle convection in the interior of terrestrial planets. However, previous theoretical calculations deviate from each other and the $\kappa$ of high-pressure B2 phase remains undetermined. Here, by combining molecular dynamics and deep potential trained with first-principles data, we systematically investigate the $\kappa$ of MgO from ambient state to the core-mantle boundary (CMB) of super-Earth with $5M_{\oplus}$. We point out the significance of 4-phonon scatterings and modify the conventional thermal conductivity model of MgO by considering the density-dependent proportion of 3-phonon and 4-phonon scatterings. The $\kappa$ profiles of MgO in Earth and super-Earth are further estimated. For super-Earth, we predict a significant reduction of $\kappa$ at the B1-B2 phase transition area near the CMB. This work provides new insights into thermal transport under extreme conditions and an improved thermal model for terrestrial planets.Comment: 4 figure

Bis(2-amino-1,3-benzothia­zol-3-ium) bis­(7-oxabicyclo­[2.2.1]heptane-2,3-dicarboxyl­ato)cadmate hexa­hydrate

In the structure of the title complex, (C7H7N2S)2[Cd(C8H8O5)2]·6H2O, the CdII atom is located on an inversion center and is O,O′,O′′-chelated by two symmetry-related 7-oxabicyclo­[2.2.1]heptane-2,3-dicarboxyl­ate ligands in a distorted octa­hedral geometry. The 2-amino­benzothia­zolium cation links with the Cd complex anion via N—H⋯O hydrogen bonding. Extensive O—H⋯O and N—H⋯O hydrogen bonds involving lattice water mol­ecules occur in the crystal structure

Facile co-sintering process to fabricate sustainable antifouling silver nanoparticles (AgNPs)-enhanced tight ceramic ultrafiltration membranes for protein separation

Protein separation in chemical industry applications using tight ceramic ultrafiltration (UF) membranes with multilayer asymmetric structures is hindered by challenges in their fabrication and fouling phenomenon. In this study, a facile co-sintering method for fabrication of silver nanoparticles (AgNPs)-enhanced tight ceramic ultrafiltration membranes was comprehensively investigated. The introduction of AgNPs into the membrane layer not only controlled the membrane surface charge properties, but also alleviated the sintering stress in the co-sintering process, ensuring a complete membrane layer owing to the higher ductility. The AgNPs obtained from silver nitrate were introduced before the formation of boehmite nucleation, providing a uniform distribution of AgNPs within boehmite owing to the electric double layer. The final UF membranes prepared by the co-sintering process exhibited a molecular weight cut-off of 9000 Da and permeance of 62 Lm−2h−1bar−1. Furthermore, the isoelectric point of the membrane surface could be controlled by the AgNPs (from 9.0 to 2.7), providing sustainable antifouling properties for protein purification owing to the electrostatic repulsion force. The AgNPs-enhanced ceramic membrane material also exhibits a higher stability without silver leakage due to the thermal treatment at 1000 °C. The proposed facile co-sintering process for fabrication of antifouling ceramic UF membranes with the assistance of AgNPs could decrease the sintering time and energy consumption, and thus is promising for industrial protein separation applications