NiMn2O4 spinel as an alternative coating material for metallic interconnects of intermediate temperature solid oxide fuel cells

In an effort to improve the performance of SUS 430 alloy as a metallic interconnect material, a low cost and Cr-free spinel coating of NiMn₂O₄ is prepared on SUS 430 alloy substrate by the sol-gel method and evaluated in terms of the microstructure, oxidation resistance and electrical conductivity. A oxide scale of 3-4 μm thick is formed during cyclic oxidation at 750 °C in air for 1000 h, consisting of an inner layer of doped Cr₂O₃ and an outer layer of doped NiMn₂O₄ and Mn₂O₃; and the growth of Cr₂O₃ and formation of MnCr₂O₄ are depressed. The oxidation kinetics obeys the parabolic law with a rate constant as low as 4.59 × 10⁻¹⁵ g² cm⁻⁴ s⁻¹. The area specific resistance at temperatures between 600 and 800 °C is in the range of 6 and 17 mΩ cm². The above results indicate that NiMn₂O₄ is a promising coating material for metallic interconnects of the intermediate temperature solid oxide fuel cells.     

Studies of cycling behavior,ageing, and interfacial reactions of LiNi0.5Mn1.5O4 and carbon electrodes for lithium-ion 5-V cells

The cycling and storage behavior of LiNi_0.5Mn_1.5O₄ and MCMB electrodes for 5-V Li-ion batteries was investigated at elevated temperatures using a variety of electrochemical (CV, EIS) and spectroscopic (XPS, micro-Raman) tools. It was established that LiNi_0.5Mn_1.5O₄ electrodes could be cycled highly reversibly, demonstrating sufficient capacity retention at 60 °C by a constant current/constant voltage mode in DMC–EC/1.5 M LiPF₆ solutions. By studying the influence of temperature on the impedance of LiNi_0.5Mn_1.5O₄ electrodes, we conclude that when the initial electrode's surface chemistry is developed at a high temperature (60 °C) it becomes nearly invariant, and hence, their impedance remains steady upon cycling and storage. Prolonged storage of these electrodes at 60 °C may result in local Mn and Ni dissolution and transformation of the active material to λ-MnO₂. We have found that the surface chemistry of aged LiNi_0.5Mn_1.5O₄ electrodes (free of carbon black and PVdF) involves the formation of LiF, C–F and P–F_x species. Storage of MCMB electrodes in LiPF₆ containing solutions at open circuit conditions (before their first lithiation) leads to significant morphological changes and the formation of lithium fluoride on the electrode surface, as determined by the XRD studies. LiF is probably a product of a catalytic thermal decomposition of LiPF₆. These initial changes further influence the impedance and kinetics of the lithiated electrodes.     

Thermoelectric properties of semi-conducting compound CoSb3 doped with Pd and Te

Hot-pressed samples of the semi-conducting compound CoSb₃-doped Pd and Te were prepared and characterized by X-ray and microprobe analysis. Thermoelectric characterization was done through measurements of the electrical and thermal conductivities as well as the Seebeck coefficient between room temperature and 900 K. All samples had n-type conductivity. The dimensionless thermoelectric figure of merit ZT increases with increasing temperature and reaches a maximum value of 1 at 873 K.     

Effect of silica coating thickness on the thermal conductivity of polyurethane/SiO2 coated multiwalled carbon nanotube composites

Silica coated multiwalled carbon nanotubes (SiO₂@MWCNTs) with different coating thicknesses of ∼4 nm, 30–50 nm, and 70–90 nm were synthesized by a sol–gel method and compounded with polyurethane (PU). The effects of SiO₂@MWCNTs on the electrical properties and thermal conductivity of the resulting PU/SiO₂@MWCNT composites were investigated. The SiO₂ coating maintained the high electrical resistivity of pure PU. Meanwhile, incorporating 0.5, 0.75 and 1.0 wt% SiO₂@MWCNT (70–90 nm) into PU, produced thermal conductivity values of 0.287, 0.289 and 0.310 W/mK, respectively, representing increases of 62.1%, 63.3% and 75.1%. The thermal conductivity of PU/SiO₂@MWCNT composites was also increased by increasing the thickness of the SiO₂ coating.     

Numerical simulation of electromagnetic sheet bulging based on FEM

A sequential coupling method has been used to analyze the electromagnetic sheet bulging. The adaptive remeshing technique is used in air meshes to make it change regularly according to the deformation result of the sheet. The deformed sheet is imported into electromagnetic model to calculate the magnetic force in next time step. Therefore, the method solves the problem of electromagnetic?Cstructure coupling analysis. According to the research results, with the increase of the sheet deflection, the effects of the radial component of the magnetic force on sheet deformation increase gradually. The optimum value of the time step is found, which corresponds to the better simulation result and less computational time. The simulative deflections at the center and 20?mm from the center with time are good in agreement with the experimental ones.     

大型风电铸件铸造工艺CAD系统的开发与应用

基于AutoCAD2010平台,以ObjectARX2010与VC＋＋.NET为开发工具,结合ODBC技术,并利用参数化设计方法开发适用于大型风电铸件的铸造工艺CAD系统。系统功能主要包括冒口系统设计、浇注系统设计、冷铁系统设计、砂箱设计及铸造工艺参数设计,并根据工厂实际生产情况设计相应的辅助功能系统。     

大型卷板机工件的视觉曲率半径测量

为准确快速的在线测量大型卷板机工件的曲率半径,利用相机拍摄投影在卷板机工件上的激光条纹,然后采用结合梯度锐化和重心法的中心提取算法对拍摄的激光条纹进行高精度的条纹中心提取,并从三维点数据拟合出曲线的半径,为卷板机的成形工艺提供实时的数据依据。     

Modelling of turbulent molten pool convection in laser welding of a copper–nickel dissimilar couple

The effects of turbulence on momentum, heat, and mass transfer during laser welding of a copper–nickel dissimilar couple are studied by carrying out three-dimensional unsteady Reynolds Averaged Navier Stokes (RANS) simulations. The turbulent transport is modelled by a suitably modified high Reynolds number k–ε model. The solid–liquid phase change is accounted for by a modified enthalpy porosity technique. In order to demonstrate the effects of turbulence, two sets of simulations are carried out for the same set of processing parameters: one with the turbulence model, and the other without activating the turbulence model. The enhanced diffusive transport associated with turbulence is shown to decrease the maximum values of temperature, velocity magnitude, and copper mass fraction in the molten pool. The effects of turbulence are found to be most prominent on the species transport in the molten pool. The composition distribution in turbulent simulation is found to be more uniform than that obtained in the simulation without turbulent transport. The nickel composition distribution predictions, as obtained from the present turbulence model based simulations, are also found to be in good agreement with the corresponding experimental results.     

Synthesis and characterization of nanolamellar tungsten and molybdenum disulfides

Tungsten and molybdenum disulfides were produced in direct self-sustained combustion in argon between elementary sulfur and metal (W, Mo) nanopowders prepared by electrical explosion of wires. The results of XRD analysis show that the main phases of the synthesized nanopowders are hexagonal WS₂ and MoS₂. According to SEM and TEM observations, they are agglomerated nanolamellar particles of thickness 40–150 nm and width 100–3000 nm.