Abstract: The phase field method is effective in simulating the formation of solidification microstructure. Based on the phase field models of coupling flow field and noise field proposed by Tong and Beckermann, using finite difference method to solve control equation, apartly simulating the dendritic morphology under the condition of convection or none convection, and drawing the following conclusions after comparing the results: in the side, the dendrite will no longer be symmetrical under the condition of countercurrent and downstream, the dendrite tip grows faster with countercurrent than that of the latter, while the dendrite grows almost naturally in the vertical direction of convection.
Abstract: In this paper, the thermal conductivity of lateral double diffused metal oxide semiconductor (LDMOS) was studied. In order to optimize their properties, the LDMOS device based on the lower surface of field (RESURF) theory join the second field plate technology. Power device self-heating effect will affect the carrier mobility, making its negative resistance effect in IV characteristic curve under the high-power condition. As the thermal conductivity of SiO2 is low, the self-heating effect of SOI device is more obvious. The simulation using Silvaco -TCAD software for different buried oxide (BOX) with different SOI layer thickness accordingly show that the thicker SOI layer and the thinner buried oxide layer, the smaller the self-heating effect.
Abstract: So far, there has been a large number of high conductivity of solid materials to replace the liquid electrolyte. All solid-state composite polymer electrolyte materials have not yet fully realized industrial production, but many areas are moving in the direction of practical development. With the deepening of the study, the ionic conductivity mechanism and constantly improve, but the ionic conductivity of composite electrolytes should be improved, need to conduct groundbreaking research in the preparation process, structure and properties of the composite electrolyte materials have many problems. The composite polymer electrolyte materials has become an intersection of many disciplines including materials science, chemistry, physics, and the content may lead to the field of new energy materials, in particular, is a new technological revolution in the field of battery materials, which study of the problem will continue and in-depth.
Abstract: Composite polymer electrolyte materials are widely used in the electrochromic glass, rechargeable lithium-ion batteries, supercapacitors, and other fields, all solid-state electrolyte to overcome the problems of the conventional liquid electrolyte rheology, chemical stability and security, applications and rangewill continue to expand. The room temperature conductivity of composite electrolytes should be improved, the need to conduct groundbreaking research in the preparation process of the composite electrolyte materials, structure and properties, there are many problems. The composite polymer electrolyte materials has become an intersection of many disciplines including materials science, chemistry, physics, and the content may lead to the field of new energy materials, in particular, is a new technological revolution in the field of battery materials, which study of the problem will continue and in-depth.
Abstract: Polymer electrolytes since the 1970s, the PV Wright, PEO polymers and inorganic salts can form complexes with high ionic conductivity. Thereafter, on a global scale, set off a craze of the theory with solid polymer electrolyte materials research and technology development, a lot of research work has been in the field to start and made great achievements in the preparation and study of different substrate materials composite polymer electrolytes, the most promising as lithium solid electrolyte materials. The polymer matrix itself large to have a high degree of crystallinity, this is very unfavorable to ion transport, therefore, to try to expand the ion transport required for the amorphous region and increase the migration of the polymer chain, and the electrolyte conductivity the rate is not only related with the polymer matrix, but also by the factors of the salt type and concentration of organic plasticizer and nano inorganic filler types and add methods.
Abstract: Ordered microporous carbon materials with controlled chemical and physical properties were synthesized by one-step nanocasting process using different carbon precursors. Large amount of heteroatoms, particularly oxygen and nitrogen species were presented in the carbon matrix. The interactions between the electrolyte ions and the surface functionalities were investigated in detail under various electrolyte environments. The electrochemical studies have revealed that different pseudo-processes occurred in proton-rich and proton-free electrolyte solutions. In proton-rich electrolyte environment, the faradaic processes are mainly due to the proton exchange between the nitrogen and oxygen species on the carbon electrode with the electrolyte. On the other hand, in proton-free electrolytes, nitrogen species was shown to play very important role in terms of the adsorption/desorption of K+ ions when negatively polarized in K+ containing electrolytes. The faradaic interaction between K+ ions and the nitrogen functionalities are stronger at the more negative potential. Very high gravimetric capacitance of 452 F/g and large capacitance retention of 97% at high discharge rate was achieved by the nitrogen-enriched carbon with moderately developed surface area. The superior capacitive performances of the templated carbons are closely linked to the ordered hierarchical porous structure, the adequate microporosity as well as the presence of suitable surface functionalities.
Abstract: Micro-arc oxidation (MAO) method was used for the surface modification of MB3 magnesium alloy. The morphology feature, phase composition, and chemical composition of the formed ceramic coatings were studied by metallographic microscope, scanning electron microscopy (SEM), XRD, respectively. Drop test has been applied to study the corrosion resistance of MB3 Mg alloy with and without micro-arc oxidation treatment. The present result indicates that, through MAO, ceramic coatings were in-situ fabricated on the surface of MB3 Mg alloy, the micro-arc oxidation coating is relatively dense and uniform, maximum thickness is more than 97μm. The dominant phase of the coating is spinal Mg2SiO4 (Forsterite) and dissociative MgO (Periclase). Drop test shows that after oxidation the corrosion resistance of MB3 Mg alloy is greatly improved.
Abstract: ZnO/TiO2 and ZnO/SnO2 composite nanoparticles were prepared by hydrothermal combined-assisted ethanol method , The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS), and the uv-vis absorption performance of which was also characterized by uv-vis diffuse reflective spectrum (UV-vis). The results of the research showed that, in ultraviolet-visible absorption spectra diffuse, the maximum absorption peaks of ZnO/TiO2 and ZnO/SnO2 nanocomposite particles were blue-shift comparing to the pure nanometer ZnO, and there were also weak absorption in the visible region.
Abstract: In this work the total energy calculations on the atomic geometry and chemisorption properties of Co(0001)/H surface are performed by using the density-functional theory in the approach of the projector-augmented wave (PAW) method. For a clean Co(0001) surface the atomic relaxations of the top three Co(0001) layers are obtained. The adsorptions of atomic Hydrogen have been investigated in the surface periodicities of p(1×1), p(1×2), p(2×2), and ( )R30º combined with hcp hollow and fcc hollow sites. For the cases studied in this work, the atomic hydrogen occupies fcc hollow site preferably drawn from the total energies. In these surface structures the perpendicular distances between the adsorbate and the first layer of substrate (DH-Co) range from 0.93 Å to 0.99 Å. The calculations on the surface vibrational modes proved the frequencies of atomic hydrogen along substrate surface displayed strong dependence on the adsorption geometries.