铜/中孔二氧化硅催化合成2,2一二甲基环丙烷甲酸乙酯

以甘氨酸、无水乙醇和异丁烯等为原料,经酯化、重氮化、环丙烷化三步反应合成2,2一二甲基环丙烷甲酸乙酯.采用中孔二氧化硅(CFG)负载铜离子为催化剂,探讨了环丙烷化的反应温度、反应时间、负载铜与非负载铜及催化剂用量对收率的影响.结果表明,当反应温度50℃,反应时间130min时,铜氨络离子与CFG 交换后经100℃处理过的Cu/CFG其催化活性最高,收率38.9%;而以铜盐为催化剂时,收率10.4%.催化剂负载后可降低铜盐用量,而且Cu/CFG易于分离,可再生使用.     

Electronic structures and related properties of Ag–Au bulks and surfaces

First-principles calculation reveals that the Ag–Au bulks are energetically favorable with negative heats of formation within the entire composition range, and the Ag–Au interaction has a negligible effect on electronic structures of Ag–Au bulks. Moreover, it is found out that surface segregation of Ag atoms could reduce the work function of Ag–Au surfaces to an extent of about 0.13–0.60 eV, and composition as well as surface state would be fundamental factors in determining surface segregation of the Ag–Au system, which could clarify the controversy regarding surface segregation of Ag–Au in the literature.     

Interactions between TiAl alloys and yttria refractory material in casting process

In this work, U-shaped yttria ceramic crucibles have been prepared to melt Ti–47Al (at.%) alloy in a vacuum induction furnace, in order to simulate the worst practical situation with respect to the interactions between TiAl alloy and yttria refractory material. The effects of superheating temperature and cooling media on the metal–crucible interface, microstructure, chemical composition and microhardness have been evaluated. The investigation demonstrates that interactions between the yttria crucible and the molten TiAl consist of slight chemical dissolution and some physical erosion and the extent of the dissolution and erosion depend on the superheating temperature. The thermodynamics of TiAl–Y₂O₃ reactions have been investigated according to the calculation of the Gibbs free energy change of the yttria dissolution reaction. The possibilities of melting and casting TiAl alloys by the use of yttria refractory material are also discussed.     

Spectroscopic and electrochemical studies on block‐polymer/PMMA blend based composite polymer electrolytes

Poly(methylmethacrylate)(PMMA)/oxymethylene‐linked polyoxyethylene multi‐block polymer(Om‐POE_n, where n represents number of unit  CH₂CH₂O ) blend based composite electrolyte films containing different lithium salt concentration and nanofillers' content are prepared using solvent evaporation technique. The interaction of polymer–salt complex has been confirmed using FTIR spectral studies. The figuration of CPE was studied by XRD. Ionic conductivity and thermal behavior of the CPEs were studied with various salt concentrations, temperature, and nanofillers' content. The surface structure of the CPE is also investigated using scanning electron microscopy. The high room temperature ionic conductivity, transmittivity in the visible region, and thermal stability make these CPEs potential candidates as solid‐like electrolytes for electrochemical devices. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

AutoCAD二次开发及应用

本文针对近年来工程中的实际应用，指出对ＡｕｔｏＣＡＤ进行二次开发的方法及一些实际的例子。     

EXC100-1B型水文巡测车液压支撑的研发改进

该文通过实例分析EXC100—1B型水文巡测车侧支撑液压缸失效故障的成因，介绍液压缸内泄的判断方法，并提出更安全、更可靠的油路改进方案。     

汽车油耗智能检测技术发展趋势

研制能快速、准确测量汽车在各种工况下油耗的仪器,已成为一项重要的课题。介绍了汽车油耗检测技术,同时重点论述了国内外汽车油耗智能检测技术的发展现状及趋势。