Ni-Mo-O催化剂中协同作用对丙烷氧化脱氢的影响

在 Ni-Mo-O体系中 ,加入 Mo O3 能极大地提高丙烷氧化脱氢制丙烯的反应活性。选用固混法、沉淀法、柠檬酸法制备了 Mo O3 过量 1 5 % (摩尔分数 )的α -Ni Mo O4催化剂 ,其中用沉淀法制得催化剂在 5 0 0℃ ,V( C3 H8) /V ( O2 ) /V ( N2 ) =1 0 /1 0 /5 0 ,反应气流量为 70 m L/min的条件下丙烷转化率可达 38.7% ,丙烯选择性达 70 .1 4 %。经 XRD,XPS,TPR表征说明 ,在含有过量 Mo O3 的催化剂中 ,α -Ni Mo O4与 Mo O3 两种晶体之间可产生微小的相互吸引 ;从而发挥协同作用 ,是提高催化剂活性     

Rapid determination of the fracture toughness of metallic materials using circumferentially notched bars

Three types of material whose fracture toughness tests were previously performed by using circumferentially notched bars, namely (1) a dual-phase steel with three different morphologies; (2) an Al-Zn-Mg-Cu-wrought alloy; and (3) Al-Si-cast alloys with three different Si contents, were investigated in terms of accuracy and reliability of the testing method. Also, the advantages of using circumferentially notched bars for fracture toughness determination of metallic materials were discussed. With the help of stress concentration factors, which are associated with the bluntness of the notch, correction factors for the fracture toughness calculations are derived. The corrected fracture toughness values are found to be close to the uncorrected ones, implying that the testing procedure is reliable.     

Oscillating Cup Viscosity Measurements of Aluminum Alloys: A201, A319 and A356

An oscillating cup viscometer was developed to measure the absolute viscosities of molten metals. Previous experiments established the capability of the apparatus to characterize the viscosities of molten nickel-based superalloys. However, modifications to the instrument and its theoretical analysis were required for reliable measurements on molten aluminum alloys, presumably due to their lower densities and lower viscosities. The theoretical literature for the fluid flow inside an oscillating cup is reviewed, and a working equation without any correction factor is developed for the improved viscometer. Some design parameters of the viscometer that directly affect the accuracy of viscosity estimation by using the working equation are discussed. A special vertical furnace was adopted to uniformly heat a longer cylindrical sample (10 mm inner diameter and 120 mm length) with a temperature difference of less than 2°C over the sample length. The measuring procedure was also improved to get more accurate motion parameters. It is estimated that the working equation and improved instrument provide an uncertainty of less than 4%. In addition, applications and experimental data are presented for pure aluminum and three aluminum alloys: A201, A319, and A356.     

Electroplating of nickel-cadmium alloys from alkaline solutions

The electroplating of Ni-Cd alloy coatings was carried out from alkaline baths (pH 10). For comparison, electroplating of the parent metals, Ni and Cd, was performed individually under the same conditions. The cathodic current efficiency for codeposition was high and decreased with increasing current density. The codeposition process is an anomalous type of plating with Cd being the preferentially deposited metal. The Ni content in the deposits increased with increasing current density. This increase in Ni content improves the corrosion resistance and microhardness of the deposits. X-ray diffraction analysis showed that the deposits consist of a mixture of Ni, β, γ, γ¹ phases.     

形状记忆合金薄膜的研究与发展

形状记忆合金是智能结构研究中重点开发的传感和驱元件材料之一。然而ＳＭＡ体材料响应速度较慢，在一五程度上限制了它的应用。ＳＭＡ薄膜弥补了这一缺陷，且更易于智能能结构集成化。本文介绍了国内外关于ＳＭＡ薄膜研究的现状。并展望了未来发展。     

Crack growth in aluminium alloy sheet material under flight-simulation loading

Crack propagation tests were carried out on 2024-T3 sheet specimens to study the effects of omitting low-amplitude cycles from the gust-dominated TWIST load sequence (MiniTWIST) and the removal of small load ranges from the manoeuvre-dominated FALSTAFF load sequence (short FALSTAFF). In other tests high-amplitude loads of TWIST and MiniTWIST were truncated at different levels. The results are compared with data from similar test programmes, including crack initiation. Attention is paid to unstationary crack growth retardation and a transient retardation during initial crack growth started by an artificial crack.     

镍代钴矿用硬质合金的新进展

概述了镍代钴矿用硬质合金的国内外进展情况．     

制备W－Ni－Cu钨合金的热解还原法工艺探讨

用硝酸镍、氯化铜与乙酸镍、乙酸铜的溶液分别与钨粉混合，干燥，经热解还原法制备的Ｗ－Ｎｉ－Ｃｕ钨合金，其技术指标均可满足使用要求。文章分析、讨论了这两种工艺特性及存在的问题。采用硝酸镍、氯化铜代镍、铜所制备的钨合金，在热解还原过程中产生大量有毒气体、严重的污染环境。乙酸镍、乙酸铜代镍和铜制备的钨合金，在热解还原过程中较好地解决了对环境及产品的污染问题，并保持了热解还原工艺的特性。     

Chemistry and Physics of Alkali Metals on MoS2 Surfaces

The interaction of alkali metal with surfaces has been of great interest to the community of catalysis since alkali metal can play an important role as a promoter. On alkali-doped MoS₂, such a promotion effect of alkali metal has been exemplified in the direct synthesis of linear alcohols from CO and H₂, where the alkali-doping switches the catalyst selectivity from methanation to alcohol synthesis. This paper reviews recent high-resolution X-ray photoelectron spectroscopy experiments that have provided direct observation of electron transfer from alkali metals to a model single crystal MoS₂ and the capture of the supra-valence electrons in the subsequent oxidation reactions.     

钼还原过程相变化研究

采用钼酸铵直接氢还原及钼酸铵先焙解然后再分段氢还原两种不同的还原方法进行了钼粉还原。通过Ｘ射线衍射方法分析了两种工艺还原过程中的反应序列及相变化规律，并讨论了不稳定相Ｍｏ４Ｏ１１对于钼粉还原过程的影响。