Enhancement in lithium storage performances of SiO2/graphene-based nanocomposites prepared by low cost and facile approach

Journal of Materials Science: Materials in Electronics - The new nanocomposites of silicon dioxide/reduced graphene oxide (SiO2/rGO) and silicon dioxide/nitrogen-doped reduced graphene oxide...     

测量船中心机箭载导航定位数据仿真软件

针对测量船中心机无法有效检验验证GPS/GNSS遥测软件的问题,设计一种测量船中心机箭载导航定位数据仿真软件。通过对软件的任务和功能需求分析,在总结测量船现有联调演练方式的基础上,提出了仿真软件的建设目标、部署方式、运行模式以及软件总体架构,并对3个关键技术进行分析。分析结果表明:该软件避免了过去只能在航天器运行时才能检验、验证相应软件是否有缺陷的状况,有利于验证系统软件设计,降低运行成本,也便于后续任务加装新型号接收机的系统联试和测试。     

De-doped polyaniline nanofibres with micropores for high-rate aqueous electrochemical capacitor

Polyaniline nanofibres have been prepared without any template or surfactant. Although the morphology of polyaniline is well kept after dealing with aqueous ammonia, de-doped polyaniline nanofibres with micropores are of better electrochemical capacitor performances in 1 M H₂SO₄ aqueous solution. Its specific capacitance is 593 F g^?1 at a constant current density of 2.5 A g^?1, and can be subjected to charge/discharge over 5000 cycles in the voltage range of 0–0.65 V. Moreover, its capacitance retention ratio reaches circa 87% with the current densities increasing from 2.5 A g^?1 to 15 A g^?1.     

A novel method to prepare nanostructured manganese dioxide and its electrochemical properties as a supercapacitor electrode

Nanostructured MnO₂ was synthesized by co-precipitation in the presence of Pluronic P123 surfactant and characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscope (SEM) and transmission electron microscope (TEM). The sample without surfactant was spherical with particle size on the submicron scale, whereas P123-assisted samples were all loose clew shapes, consisting of MnO₂ nanowires, 8-20 nm in diameter and 200-400 nm in length. The electrochemical performances of the as-prepared MnO₂ as the electrode materials for supercapacitors were evaluated by cyclic voltammetry and galvanostatic charge-discharge measurements in a solution of 1 M Na₂SO₄. The sample without surfactant exhibited a relatively low specific capacitance of 77 F g⁻¹, whereas the nanostructured MnO₂ prepared with 0.02% (wt%) P123 exhibited excellent pseudocapacitive behavior, with a maximum specific capacitance of 176 F g⁻¹.     

Carbon-coated SiO2 nanoparticles as anode material for lithium ion batteries

A simple approach is proposed to prepare C-SiO₂ composites as anode materials for lithium ion batteries. In this novel approach, nano-sized silica is soaked in sucrose solution and then heat treated at 900 °C under nitrogen atmosphere. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis shows that SiO₂ is embedded in amorphous carbon matrix. The electrochemical test results indicate that the electrochemical performance of the C-SiO₂ composites relates to the SiO₂ content of the composite. The C-SiO₂ composite with 50.1% SiO₂ shows the best reversible lithium storage performance. It delivers an initial discharge capacity of 536 mAh g⁻¹ and good cyclability with the capacity of above 500 mAh g⁻¹ at 50th cycle. Electrochemical impedance spectra (EIS) indicates that the carbon layer coated on SiO₂ particles can diminish interfacial impedance, which leads to its good electrochemical performance.     

Capacity fade in Sn-C nanopowder anodes due to fracture

Sn based anodes allow for high initial capacities, which however cannot be retained due to the severe mechanical damage that occurs during Li-insertion and de-insertion. To better understand the fracture process during electrochemical cycling three different nanopowders comprised of Sn particles attached on artificial graphite, natural graphite or micro-carbon microbeads were examined. Although an initial capacity of 700?mAh?g(-1) was obtained for all Sn-C nanopowders, a significant capacity fade took place with continuous electrochemical cycling. The microstructural changes in the electrodes corresponding to the changes in electrochemical behavior were studied by transmission and scanning electron microscopy. The fragmentation of Sn observed by microscopy correlates with the capacity fade, but this fragmentation and capacity fade can be controlled by controlling the initial microstructure. It was found that there is a dependence of the capacity fade on the Sn particle volume and surface area fraction of Sn on carbon.     

A novel method for preparation of macroposous lithium nickel manganese oxygen as cathode material for lithium ion batteries

A simple one-step route using gas template method is applied to synthesize macroporous LiNi_0.5Mn_0.5O₂ which is characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Telle (BET) surface area, charge–discharge tests and electrochemical impedance spectroscopy (EIS) measurements. The as-synthesized material shows pure crystalline phase of LiNi_0.5Mn_0.5O₂, while the microstructure is comprised of macrospores ranging from 0.2 to 0.5 μm. The first discharge capacity is of 174 mAh g⁻¹ at 0.1 C rate, which is much higher than that of the material synthesized by the conventional solid state reaction method. Furthermore, the macroporous LiNi_0.5Mn_0.5O₂ material shows remarkable rate capacity and cycle stability, which may be attributed to the shorter lithium ion diffusion distance and better electrolyte penetration.     

基于分层体系结构的卫模仿真软件通用化设计

为解决卫星型号多、遥控码表变化大、遥测参数仿真复杂和卫模平台接口多样化等问题,提出基于分层体系结构的卫模仿真软件通用化设计。在对某型号卫星模拟器仿真软件研制过程进行分析的基础上,采用分层体系结构和接口标准化等方法实现通用化设计,并进一步指出实现通用化卫模仿真软件的关键技术和研究途径。结果表明：该设计能实现卫模仿真软件的通用化,为研制通用卫星模拟器仿真软件积累了经验,指明了方向。     

Ultrasonic-assisted synthesis of Pd–Ni alloy catalysts supported on multi-walled carbon nanotubes for formic acid electrooxidation

Pd–Ni alloys with different compositions (i.e. Pd₂Ni, PdNi, PdNi₂) dispersed on multi-walled carbon nanotubes (MWCNTs) are prepared by ultrasonic-assisted chemical reduction. The X-ray diffraction (XRD) patterns indicate that all Pd and Pd–Ni nanoparticles exist as Pd face-centered cubic structure, while Ni alloys with Pd. The transmission electron microscopy (TEM) images show the addition of nickel decreases the particle size and improves the dispersion. The X-ray photoelectron spectroscopy (XPS) spectra demonstrate the electronic modification of Pd by nickel doping. The electrochemical measurements reveal that the PdNi catalysts have better catalytic activity and stability for formic acid electrooxidation, among them PdNi/MWCNTs is the best. The performance enhancement is ascribed to the increase of electroactive surface area (EASA) and nickel doping effect which might modify the electronic structure.     

Fabrication of morphology controllable rutile TiO2 nanowire arrays by solvothermal route for dye-sensitized solar cells

Highly ordered, vertically oriented TiO₂ nanowire arrays (TNAs) are synthesized directly on transparent conducting substrate by solvothermal procedure without any template. The X-ray diffraction (XRD) pattern shows that TiO₂ array is in rutile phase growing along the (0 0 2) direction. The field-emission scanning electron microscopy (FE-SEM) images of the samples indicate that the TiO₂ array surface morphology and orientation are highly dependent on the synthesis conditions. In a typical condition of solvothermal at 180 °C for 2 h, the TNAs are composed of nanowires 10 ± 2 nm in width, and several nanowires bunch together to form a larger secondary structure of 60 ± 10 nm wide. Dye-sensitized solar cell (DSSC) assembled with the TNAs grown on the FTO glass as photoanode under illumination of simulated AM 1.5G solar light (100 mW cm⁻²) achieves an overall photoelectric conversion efficiency of 1.64%.