Growth mechanism of CdS film prepared by chemical bath deposition

In this paper, sodium citrate was adopted as a complexing agent and ammonia merely served as pH adjustor to investigate the growth mechanism of CdS film The growth rate, structural properties, surface morphology microstructure, and optical properties of CdS films were studied by profilometer, X-ray diffractometer（XRD）scanning electron microscopy（SEM）, transmission elec tron microscopy（TEM）, and spectrophotometer, respec tively. The SEM images show that CdS films prepared with higher ammonia concentration have lower nucleation density on substrate. SEM and EDS results show that the formation of Cd（OH）2is not required in the growth of CdS film. As the ammonia concentration increases, the sites tha previously adsorbed S2-are taken by OH-which leads to lower S2-density on substrate. CdS film forms through direct reaction of Cd2？with the S2-which are adsorbed on the substrate. Lower S2-density on the substrate results in the decrease of particle density on the substrate. The as deposited CdS films have relatively high-average trans mittance（＊80 %） in the wavelength range from 500 to1,000 nm which makes them suitable to be used in sola cell.     

Microstructure and Mechanical Properties of ε-Phase-Reinforced ZnAl4Y Matrix Composite Prepared by Mixed Solid-Liquid Casting

ε-Phase-reinforced ZnAl4Y matrix composite has been fabricated by mixed solid-liquid casting method. The results show that the size of primary η-Zn phase in the composite decreases remarkably with the increase of adding amount of Cu-10wt.%Al powders till it reaches 6.0 wt.% in ZnAl4Y alloy. Besides, a large amount of small ε-phase particles form in ZnAl4Y matrix when the adding amount of Cu-10wt.%Al powders is in the range of 4.0-6.0 wt.% in ZnAl4Y alloy. Coarse ε-phase particles forms when the adding amount of Cu-10wt.%Al powders exceeds 8.0 wt.% in ZnAl4Y alloy. Compared with ZnAl4Y alloy, the composite could obtain optimal mechanical properties when the added amount of Cu-10wt.%Al powders is 6.0 wt.%.     

Microstructure and Tribological Properties of WC-CeO2/Ni- base Alloy Composite Coatings

运用等离子喷涂技术在7005铝合金表面制备了WC和CeO2颗粒协同增强镍基合金复合涂层,研究了该复合涂层的微观结构和摩擦学性能。结果表明:加入CeO2颗粒细化了复合涂层的显微组织,使WC增强颗粒从圆形变为不规则多边形,并降低了其脱碳分解程度。不同PV值摩擦条件下,WC-CeO2/镍基合金复合涂层的摩擦系数和磨损失重均低于WC/镍基合金复合涂层和镍基合金涂层。PV值小于3.36 N·m/s时,复合涂层磨损表面的最大接触应力低于其弹性极限接触应力,主要发生微观切削磨损和疲劳磨损;PV值大于3.36N·m/s后,磨损表面的最大接触应力超过其弹性极限接触应力,接触温度也急剧上升至648℃,磨损表面出现明显的塑性变形和脱落,其磨损机制变为多次塑变磨损、磨粒磨损和粘着磨损,并伴有氧化磨损。     

降温速率对CdZnTe晶体内Te夹杂相的影响

采用改进的垂直布里奇曼生长法生长CdZnTe(CZT)单晶。生长完成后,选取了10~60 K/h不同速率降温处理。采用红外透射显微镜和多道能谱仪分别测试不同降温速率的晶片内部Te夹杂相分布和能谱响应。结果表明,10~30K/h之间的慢速降温会导致晶体内部出现较大尺寸的Te夹杂(>10μm),40 K/h以上的快速降温所得到的晶体内部主要以小尺寸(<10μm)为主。同时快速降温会导致晶体内部的Te夹杂浓度大量增加,并且降温速率越快,Te夹杂浓度越大。此外,降温速率过慢所得到晶片的能谱分辨率较差,但是降温速率过快也会影响到晶片的性能。40 K/h的降温速率所得到的晶片能谱性能较好,实验结果表明:大尺寸或者高浓度的Te夹杂都不利于能谱响应,保留一定浓度的小尺寸Te夹杂的晶体能谱性能较佳。     

超细无粘结相WC基陶瓷的研究进展

综述了近年来国内外超细无粘结相WC基陶瓷的研究状况,无/少粘结相、晶粒的纳米化是研发高性能WC基硬质陶瓷的发展方向之一,其在硬度、高温强度、抗腐蚀、耐磨损等方面较传统硬质合金有明显的优势,具有广阔的应用前景。介绍了机械合金化法、快速碳热还原法、直接碳化法、等离子体化学合成法等超细WC粉末的制备方法,超细无粘结相WC基陶瓷的新型制备技术以及材料的复合改性等内容,并分析了该材料在研究应用过程中面临的困难,认为解决材料的工业化生产、纳米粉末的均匀分散等问题,建立碳氧含量对其性能影响的量化指标是现阶段的研究重点。     

成教《精细有机合成化学及工艺学》课程教学方法探讨

针对成人教育和精细化学品生产技术专业特点,教师在教学过程中通过适当调整教学内容、完善课程教学资料、采用启发式教学方法、严格考核等,使学生学习效率明显提高,教学效果良好。     

Preparation of (0 2 0)-oriented BaTi2O5 thick films and their dielectric responses

Barium dititanate (BaTi₂O₅) thick films were prepared on a Pt-coated Si substrate by laser chemical vapor deposition, and ac electric responses of (0 2 0)-oriented BaTi₂O₅ films were investigated using several equivalent electric circuit models. BaTi₂O₅ films in a single phase were obtained at a Ti/Ba molar ratio (m_Ti/Ba) of 1.72–1.74 and deposition temperature (T_dep) of 908–1065 K as well as m_Ti/Ba = 1.95 and T_dep = 914–953 K. (0 2 0)-oriented BaTi₂O₅ films were obtained at m_Ti/Ba = 1.72–1.74 and T_dep = 989–1051 K. BaTi₂O₅ films had columnar grains, and the deposition rate reached 93 μm h^?1. The maximum relative permittivity of the (0 2 0)-oriented BaTi₂O₅ film prepared at T_dep = 989 K was 653 at 759 K. The model of an equivalent circuit involving a parallel combination of a resistor, a capacitor, and a constant phase element well fitted the frequency dependence of the interrelated ac electrical responses of the impedance, electric modulus, and admittance of (0 2 0)-oriented BaTi₂O₅ films.     

A novel colour image encryption algorithm based on chaos

In this paper, a novel colour image encryption algorithm based on chaos has been proposed. We use chaotic system to encrypt the R, G, B components of a colour image at the same time and make these three components affect each other. So the correlations between R, G, B components can be reduced and the security of algorithm is increased. Simulation results show that the proposed algorithm can encrypt colour image effectively and resist various typical attacks.     

Interfacial stress analysis of plated beams under symmetric mechanical and thermal loading

Extensive research has shown that bonding a thin plate to the tension face of a beam can significantly improve its flexural performance. Such a plated beam often fails by the premature debonding of the thin plate from the original beam in a brittle manner. A sound understanding of the mechanism of such debonding failures is important for the effective use of this strengthening technique. This paper presents a new analytical solution for the interfacial stresses in plated beams subjected to arbitrary mechanical and thermal loads which are symmetrically positioned about the mid-span. While the bonding of fiber reinforced polymer (FRP) plates to reinforced concrete (RC) beams represents the most common application of the plate bonding technique, the present solution is generic in terms of the materials of the beam and the plate. The solution is represented by Fourier series and is based on the minimisation of complementary energy. The new solution takes into consideration the non-uniform stress distribution in the adhesive layer and the stress-free boundary condition at the ends of the plate. In addition, it correctly predicts the drastic difference in the interfacial normal stress between the plate-to-adhesive interface and the adhesive-to-beam interface. The solution is general in nature and may be applied to the analysis of other types of composite structures.     

Acrolein formation in the oxidation of ethane over silica catalysts supporting iron and cesium

A significant yield of aldehydes was obtained by the partial oxidation of ethane over alkali‐modified Fe/SiO₂ catalysts at 475°C (<2% in the case of Cs–Fe/SiO₂). Not only acetaldehyde and formaldehyde but also acrolein were produced in the present system. There are no reports regarding the catalysts for the direct acrolein formation from partial oxidation of ethane. Such significant promoting effect of alkali‐modified Fe/SiO₂ catalysts in the partial oxidation of hydrocarbons has never been observed. Aldol‐type condensation for formation of acrolein could occur in the partial oxidation of ethane over alkali‐modified Fe/SiO₂ catalysts. This revised version was published online in July 2006 with corrections to the Cover Date.