高活性氧化亚铜薄膜材料的绿色合成研究

本文采用一步脉冲雾化化学气相沉积法在250℃下制备了氧化亚铜薄膜催化剂.实验研究了前驱体中掺杂水对氧化铜薄膜表面形貌、拓扑结构、表面成分和光学特性的影响规律.结果表明所制得的催化剂为纯相的氧化亚铜.前驱体溶液中掺杂水会导致氧化亚铜的晶粒变小,从而使得共光学能隙从2.16 eV降至2.04 eV.原子力显微镜结果表明随着水的加入,氧化亚铜的表面粗糙度降低,表面更加均匀.此外,利用密度泛函理论计算得到了水和乙醇在氧化亚铜薄膜表面的吸附和反应特性,并提出了氧化亚铜的形成机理.本文开发了一种低成本且实际可行的薄膜制造方法,该方法在太阳能电池和半导体等领域具有潜在应用.     

Finite element modelling of cold drawing for high-precision tubes

Cold tube drawing is a metal forming process that allows manufacturers to produce high-precision tubes. The dimensions of the tube are reduced by pulling it through a conical converging die with or without inner tool. In this study, finite element modelling has been used to give a better understanding of the process.This paper presents a model that predicts the final dimensions of the tube with very high accuracy. It is validated thanks to experimental tests. Moreover, five studies are performed with this model, such as investigating the influence of the die angle on the drawing force or the influence of relative thickness on tube deformation.     

微弧等离子喷涂碳纳米管/纳米Al2O3-TiO2复合涂层的吸波性能研究

将碳纳米管与纳米Al₂O₃-TiO₂陶瓷粉末超声共混制备了碳纳米管/纳米Al₂O₃-TiO₂复合粉末,测试了复合粉末在2—18GHz波段的电磁参数.研究表明：随着碳纳米管质量分数的增加,碳纳米管/纳米Al₂O₃-TiO₂复合粉末的复介电常数和损耗角不断增大.当碳纳米管质量分数和厚度增加时,复合粉末对电磁波的反射率峰值先增加后减小,而谐振频率不断向低频移动.采用微弧等离子喷涂制备了7wt%碳纳米管/纳米Al₂O₃-TiO₂复合吸波涂层,当厚度为1.5mm时,涂层最小反射率为-24.0dB,当厚度为2.0mm时,涂层小于-10dB的频带宽为3.60GHz,当温度为500℃高温时,1.0mm厚的涂层最小高温反射率为-12.2dB,小于-10dB频带宽为2.0GHz.复合涂层的实际厚度D与理论厚度d呈线关系：d=0.898D+0.515. 关键词： 等离子喷涂 碳纳米管 2O₃-TiO₂')" href="#">纳米Al₂O₃-TiO₂ 吸波性能     

Superfluid phases of the three-species fermion gas

We discuss the zero temperature phase diagram of a dilute gas with three fermionic species. We make use of solvable limits to conjecture the behavior of the system in the “unitary” regions. The physics of the Thomas-Efimov effect plays a role in these considerations. We find a rich phase diagram with superfluid, gapless superfluid and inhomogeneous phases with different symmetry breaking patterns. We then discuss one particular possible experimental implementation in a system of ⁶Li atoms and the possible phases arising in this system as an external magnetic field is varied across three overlapping Feshbach resonances. We also suggest how to experimentally distinguish the different phases.     

含甲缩醛柴油喷雾和燃烧排放特性的试验研究

应用激光相位多普勒技术测量了含甲缩醛柴油喷雾的速度场和粒径场,在直喷式柴油机上研究了该含氧混合燃油的燃烧排放特性。结果表明,添加甲缩醛可改善柴油的雾化,增加喷雾轴线上的粒子速度,但减小喷雾锥角;同时以远大于其加入的比例降低柴油机排气烟度,但对氮氧化物的排放影响不大。柴油机采用甲缩醛作燃油添加剂时,需改造燃油系统。     

雾化喷射冷却的机理及模型研究

雾化喷射冷却的换热机理十分复杂,目前其研究还很不成熟。本文从喷射雾滴的特性参数出发,以被冷却表面上形成的喷射液膜为对象,考虑了冷却液体向环境的散热,建立质量、能量守恒方程,得到半经验半解析的雾化喷射换热模型。其中,本文提出真换热系数和显换热系数的概念,认为显换热系数受空间散热影响,而真换热系数只与喷雾动量有关。最后设计了雾化喷射局部换热实验,对模型进行检验,结果表明,该模型能够较好地符合实验所得的换热系数及加热面表面温度沿喷射半径的分布趋势。     

Preparation of lithium carbonate hollow spheres by spray pyrolysis

Lithium carbonate (Li₂CO₃) hollow spheres were prepared by spray pyrolysis of lithium bicarbonate (LiHCO₃) in this research. The products were characterized by X‐ray diffraction (XRD), scanning electron microscope (SEM), crystal size distribution (CSD) analysis and BET surface area measurement. The XRD figure of the product is nearly the same as the standard pattern, indicating the product achieved by spray pyrolysis has pure Li₂CO₃ crystalline phase. The SEM images show the self‐assembly hollow spheres are composed of about 200 nm primary particles. While the CSD analysis shows the macro‐volume mean crystal size ranges 4‐9 μm depending on the experimental conditions. The BET surface area of the product reaches 7.24 m²/g, which is much higher than the best value reported in the literature. The product prepared in this work has great potential application prospect in the lithium‐battery industry. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

固体吸附管捕集冷原子吸收光谱法测定工作场所空气中汞的研究

建立了工作场所空气中汞及其化合物的高锰酸钾-二氧化锰混合固体吸附管捕集、冷原子吸收测定方法。用高锰酸钾与二氧化锰按质量比1∶1混合后填装玻璃管制成固体吸附管捕集工作场所空气中汞,并以0.90 mol·L-1的硫酸溶液解吸后冷原子吸收光谱法测定,与高锰酸钾-硫酸吸收液法的采样效率、样品稳定性、穿透容量进行了比对。在0.000 2~0.015 0 mg·L-1的浓度范围内线性关系良好,相关系数为0.999 1,空气中汞在0.001~2.820 mg·m-3范围内,平均采样效率为99.9%~100.0%,300 mg吸附剂对汞的穿透容量大于505.4 μg,吸附管对汞的平均加标回收率为96.4%~103.8%,日内、日间精密度分别为3.0%~3.3%,3.5%~5.2%,最低检出浓度为0.001 3 mg·m-3(以采集7.5 L空气样品计)、0.000 6(以96 L空气样品计)。采集后的吸附管在室温下保存30 d,下降率小于0.1%。固体吸附管采样方法简单,适用于工作场所空气中汞及其化合物的短时间、时间加权平均浓度及个体暴露浓度的采样检测。     

Polydisperse effects in jet spray flames

A laminar jet polydisperse spray diffusion flame is analysed mathematically for the first time using an extension of classical similarity solutions for gaseous jet flames. The analysis enables a comparison to be drawn between conditions for flame stability or flame blow-out for purely gaseous flames and for spray flames. It is found that, in contrast to the Schmidt number criteria relevant to gas flames, droplet size and initial spray polydispersity play a critical role in determining potential flame scenarios. Some qualitative agreement for lift-off height is found when comparing predictions of the theory and sparse independent experimental evidence from the literature.     

Optoelectronic properties of SnO_2 thin films sprayed at different deposition times

This article presents the elaboration of tin oxide(SnO_2) thin films on glass substrates by using a home-made spray pyrolysis system. Effects of film thickness on the structural, optical, and electrical film properties are investigated. The films are characterized by several techniques such as x-ray diffraction(XRD), atomic force microscopy(AFM), ultravioletvisible(UV–Vis) transmission, and four-probe point measurements, and the results suggest that the prepared films are uniform and well adherent to the substrates. X-ray diffraction(XRD) patterns show that SnO_2 film is of polycrystal with cassiterite tetragonal crystal structure and a preferential orientation along the(110) plane. The calculated grain sizes are in a range from 32.93 nm to 56.88 nm. Optical transmittance spectra of the films show that their high transparency average transmittances are greater than 65% in the visible region. The optical gaps of SnO_2 thin films are found to be in a range of 3.64 e V–3.94 e V. Figures of merit for SnO_2 thin films reveal that their maximum value is about 1.15 × 10-4-1?atλ = 550 nm. Moreover, the measured electrical resistivity at room temperature is on the order of 10-2?·cm.