Solvothermal synthesis of carbon-coated tin nanorods for superior reversible lithium ion storage

This paper reports the large-scale synthesis of carbon-coated tin (Sn-C) nanorods through a facile solvothermal carbonization approach by using Sn nanorods as templates and ethanol as a solvent. The as-synthesized Sn-C nanorods have been applied as anode materials for lithium-ion batteries. The Sn-C anode, which exhibits relatively higher initial Coulombic efficiency and lithium storage capacities, is more attractive than the previously reported tin oxide or sulfide anodes. The superior performance of the Sn-C nanorods makes it a promising anode material in high-energy density batteries.     

An efficient room-temperature route to uniform ZnO nanorods with an ionic liquid

Rod-like ZnO nanocrystals have been synthesized via an ultrasound-assisted way by the reaction between Zn(CH₃COO)₂·2H₂O and NaOH in the ionic liquid 1-butyl-3-methyl imidazole six hexafluorophosphoric acid salts ([BMIM][PF₆]) aqueous solution. The products were characterized by XRD, EDX, FESEM, TEM, HRTEM, UV-Vis and PL techniques. The as-prepared ZnO nanorods have a diameter of about 50 nm and a length of 1-2 μm. A plausible four-step mechanism was proposed to explain the formation of ZnO nanorods. It was found that the lowered ion diffusion velocity in the water-ionic liquid medium could largely contribute to the formation of the ZnO nanorods. The effects of experimental parameters on the formation of the products were also explored.     

Low-temperature mechanochemical–thermal synthesis of α-Al2O3 nanocrystals

The great capability of high-energy ball milled basic polyaluminium chloride gel (PACl) which consisted of the monomeric Al³⁺ ions and polymerized Al³⁺ species such as [Al₁₃O₄(OH)₂₄(H₂O)₁₂]⁷⁺ with a Keggin like structure to enhance the phase transformation into α-Al₂O₃ nanocrystals at low temperature was verified. PACl gel 10 min milled and annealed at 400 °C, partially transformed to nanocrystalline α-Al₂O₃ with the mean XRD crystallite size in the range of 15–17 nm, embedded in an amorphous or transition alumina matrix. Further crystal growth up to ∼50 nm and phase pure α-Al₂O₃ powder was obtained when heat-treated at 1000 °C. In contrast to this, the non-milled PACl gel transforms to the transition θ-Al₂O₃ phase at 1000 °C. The evolution of α-Al₂O₃ nanocrystals was studied by XRD, TEM, selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) methods.     

Synthesis and thermal stability of W-doped VO2 nanocrystals

Pure and W-doped vanadium dioxide nanocrystals have been synthesized by using V₂O₅ and oxalic acid as precursors via a thermolysis method. The VO₂ nanocrystals have a nearly spherical morphology with size ranging from 50 to 100 nm. The metal-insulator transition (MIT) temperature of the nanocrystals decreases with increasing W-doping content. The successive heat-induced fatigue character of the MIT in W-doped VO₂ nanocrystals was investigated by DSC analysis together with structural study, and a high stability upon heating–cooling cycles was found with respect to MIT temperature, peak temperature and latent heat of the phase transition.     

A novel single-step synthesis of N-doped TiO2 via a sonochemical method

A novel single-step synthetic method for the preparation of anatase N-doped TiO₂ nanocrystalline at low temperature has been devoleped. The N-doped anatase TiO₂ nanoparticles were synthesized by sonication of the solution of tetraisopropyl titanium and urea in water and isopropyl alcohol at 80 °C for 150 min. The as-prepared sample was characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and UV–vis absorption spectrum. The product structure depends on the reaction temperature and reaction time. The photocatalytic activity of the as-prepared photocatalyst was evaluated via the photodegradation of an azo dye direct sky blue 5B. The results show that the N-doped TiO₂ nanocrystalline prepared via sonication exhibit an excellent photocatalytic activity under UV light and simulated sunlight.     

One-step synthesis of reduced graphite oxide–silver nanocomposite

Here, a general approach for the preparation of reduced graphite oxide (rGO)–silver nanocomposite has been investigated. Graphite oxide (GO) sheets are used as the nanoscale substrates for the formation of rGO–silver composite. GO sheets and Ag ions can be reduced at the same time, under a mild condition using l-ascorbic acid (l-AA) as reducing agent. This simple approach should find practical applications in the production of rGO–silver nanocomposite. The SEM analysis indicates that the silver particles are dispersed on graphene sheets. Raman signals of rGO in the composite are increased by the attached silver nanoparticles, displaying surface-enhanced Raman scattering activity. The degree of enhancement can be adjusted by varying the quantity of silver nanoparticles in the composite. In addition, antibacterial activity of the composite against Escherichia coli was evaluated using zone of inhibition. Composites with Ag clearly showed antibacterial activity against E. coli. While GO alone has almost no effect against this bacteria.     

Honeycomb-like graphitic ordered macroporous carbon prepared by pyrolysis of ammonium bicarbonate

Honeycomb-like graphitic macroporous carbon (HGMC) was synthesized by means of pyrolysis of NH₄HCO₃ using Mg powder as reductant in an autoclave at 550 °C. The characterization of structure and morphology was carried out by X-ray diffraction (XRD), Raman spectrum, field-emission scanning electron microscopy (FESEM), and (High-resolution) transmission electron microscope [(HR)TEM]. The results of nitrogen adsorption-desorption indicate that the products are macropore materials with the pore size of 1-3 μm, and the Brunauer-Emett-Teller (BET) surface area was 14 m²/g. As a typical morphology, the possible growth process of HGMC was also investigated and discussed. The experimental results show that the in situ formed MgO microparticles play a template role during the HGMC formation.     

The control of the diameter and length of α-MnO2 nanorods by regulation of reaction parameters and their thermogravimetric properties

α-MnO₂-type single-crystal nanorods were synthesized under hydrothermal conditions based on the redox reaction of KMnO₄ in an acidic environment. Several reaction parameters, like the reaction temperature, the reaction time and the concentration of KMnO₄ in the reaction mixture, were varied in order to determine their impact on the structure, the dimensions of the synthesized nanorods, and as well on their thermogravimetric properties. It was found that the reaction time has no significant influence on the diameter, although it has a strong influence on the length of the obtained nanorods. On the other hand, the concentration of KMnO₄ in the reaction mixture has a strong impact on both the diameter and the length. With an increasing concentration of KMnO₄ in the reaction mixture the average lengths and diameters of the isolated MnO₂ nanorods are reduced. The change in dimensions of the synthesized nanorods is reflected in their thermogravimetric properties.     

基于相位差谱与幅值谱的人造地震动的反应谱拟合

首先,利用相位差分谱与非平稳强度包络线的相似关系确定地震动的相位角,根据速度谱与傅里叶幅值谱的形状相似来近似地震动的幅值谱,然后,通过在频域内调整傅里叶振幅谱的方法合成加速度时程.算例分析结果表明,该算法所得到的人工地震动时程对目标谱具有较好的精度.     

地震动的频谱特性和持时对结构地震反应的影响研究及其现状

多年来,国内外地震工程界存在着一个严重缺陷,即地震学与结构抗震两者之间缺乏联系.随着基于性能的地震工程学(PBEE)的出现以及不断发展,地震学的重要性日益凸显.在结构抗震设计和分析中,强震地面运动特性的变异性对于结构地震需求的影响最大,其主要可以用幅值、频谱特性和持时3个基本要素来表示.震害经验表明,各类结构的震害表现为这3个基本要素综合影响的结果.因此,通过研究强震地面运动特性对于结构地震需求的影响,将地震工程学与结构抗震有机地结合起来是一个必然的发展趋势.