溶剂热合成三维蔷薇花状SnS2微晶

在乙二醇溶剂热条件下,采用SnCl4·H2O和硫代氨基脲为原料,成功制备出了三维蔷薇花状的SnS2微晶.产品用X-射线粉末衍射(XRD)、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)、拉曼光谱(RS)和紫外一可见吸收光谱(UV-Vis)对样品进行了表征.结果表明SnS2蔷薇花是由纳米级厚度的片状"花瓣"相互连接、交叠、缠绕自组装生长而成.并对蔷薇花状SnS2三维结构的生长机理进行了简单探讨.     

室温超声合成哑铃状纳米氧化锌

以乙酸锌和六次甲基四胺的水溶液为前驱体溶体,采用超声直接沉淀法,于室温下超声30 min,成功制备出结晶性好的哑铃状纳米氧化锌(1),其结构和形貌经X-射线衍射、能量色散X-射线分析及场发射扫描电子显微镜表征.结果表明,1结晶性好,平均直径250 nm,长度达微米级,沿着c轴对称取向生长.对生长过程进行了分析.     

Effect of solution concentrations on crystal structure,surface topographies and photoluminescence properties of ZnO thin films

Zinc oxide thin films were deposited on silicon substrates via hydrothermal method. Microstructures, surface topographies and optical properties of ZnO thin films were systematically investigated by X-ray diffraction, atomic force microscopy and fluorescence spectrophotometer. The mean grain size and surface roughness of the thin films decrease first and then increase with increasing the concentration of zinc nitrate hexahydrate. The photoluminescence spectra of ZnO thin films, excited by the 240, 320, 360, 380 and 400 nm excitation wavelength, were investigated in detail. Based on our analysis, it can be noted that mechanisms of the ultraviolet, violet and blue emissions are attributed to the transitions from the localized levels below the conduction band, zinc vacancy, interstitial zinc and extended interstitial zinc levels to the valance band, respectively. Blue–violet emissions of ZnO have great potential in light emitting and biological fluorescence labeling applications.     

HREELS study of C70 molecules adsorbed on a Si(1 1 1)-(7×7) surface

We have measured the coverage dependence of vibrational excitation spectra of C₇₀ molecules adsorbed on a Si(1 1 1)-(7×7) surface using high-resolution electron-energy-loss spectroscopy. At the monolayer coverage, the intensity of the 57 meV peak increases, and those of the 83 and 178 meV peaks decrease. Taking into account the dipole selection rule, the change in intensity of the 57 meV peak indicates that the average angle between the long axes of C₇₀ molecules and surface normal is about 40°. The decreases in intensities of the 83 and 178 meV peaks suggest that the rotational motion of molecules is quenched upon adsorption. We will discuss the Coriolis interaction between the accidentally degenerate A₂″ and E₁′ modes.     

Study of the relationships between materials and their radiative properties: Application to natural fibers for the spectral wavelengths range 0.25–2.5 μm

Measurements were made of the reflectance and transmittance of wool and cotton, natural and dyed, using an integrating sphere spectrophotometer.     

The sky temperature in net radiant heat loss calculations from low-sloped roofs

The results of calculated and measured sky temperatures for a horizontal surface in clear night-time sky conditions are compared and discussed. In the case of large city areas (atmospheric pollution) the sky temperature may be about 10°C higher than the one calculated according to Swinbank's formula. The paper presents a quantitative analysis concerning the influence of the sky temperature values variations on net radiant heat loss and the heat balance of the low-sloped roofs.     

Energy recovery and plume reduction from an industrial spray drying unit using an absorption heat transformer

Spray drying is a widely used unit operation in the chemical industry. It is highly energy intensive, requiring hot, dry airstreams, at temperatures up to 550°C, to dry a wide range of products. Exhaust air from a dryer is usually vented to the atmosphere with little or no heat recovery. At best only the sensible heat associated with the air stream is recovered, although the majority of the stream's energy is in the form of latent heat associated with the evaporated water. Exhaust airstreams usually contain moisture to cause visible plumes upon leaving the dryer stack.A two-stage absorption heat transformer (A.H.T.) has been designed and contructed to investigate the potential for dehumidifying and reheating a simulated dryer exhaust stream to make it suitable for recycling to the dryer inlet. The amount of air vented to atmosphere and also the amount of wasted heat would be reduced by incorporating an A.H.T. into the drying operation. Performance data for the A.H.T. indicates that an airstream can be reheated to a temperature of 160°C, using a lithium bromide solution of 68% w/w, with a circulation ratio (LiBr: steam flow) of 14.8. Temperature lifts between 50 and 70°C are possible in the reheat column when using a low circulation ratio and a high LiBr concentration. Experiments show that a humid air stream can be dehumidified to a level suitable for recycling by direct contact with a concentrated lithium bromide stream.     

复合材料层板饱和裂纹间距的试凑法(cut-and-try)

本文首次通过三维有限元法计算分析出90°层中横向裂纹的饱和间距值,为预测饱和裂纹间距提供了一条新途径.     

Vertically positioned axially viewed aerosol cooled plasma — a new design approach for microwave induced plasma optical spectrometry with solution nebulization

A vertically positioned axially viewed argon microwave induced plasma (Ar-MIP) system is described, which can serve as a spectrochemical excitation source. The design concept of improved TE₁₀₁ rectangular cavity based on strong coupling between the plasma load and the magnetron generator has been presented. The idea of plasma cooling with a pure water aerosol is explained. The torch cooling system which permits aerosol generation and circulation has been described in detail. The influence of cooling on the argon plasma positioning in the discharge tube was investigated. The spectroscopic temperatures of iron and argon have been measured to evaluate excitation conditions and effect of plasma cooling. Analytical performance of the presented MIP system was characterized by determination of the limits of detection for some elements and comparison with other Ar-MIP experimental setups. Analysis of certified reference material was performed to determine the accuracy and precision available with the presented system.