Effects of Ni,Fe2O3, and CNT addition by reactive mechanical grinding on the reaction rates with H2 of Mg-based alloys

Ni, Fe₂O₃, and CNT were added to Mg. The content of the additives was about 20 wt % with that of Fe₂O₃ 6 wt%. The contents of about 20 wt % additives and 6 wt% Fe₂O₃ are known optimum ones to improve the reaction rates of Mg with H₂. Samples with compositions of 80 wt% Mg–14 wt% Ni–6 wt% Fe₂O₃ (named as Mg–14Ni–6Fe₂O₃), and 78 wt% Mg–14 wt% Ni–6 wt% Fe₂O₃–2 wt% CNT (named as Mg–14Ni–6Fe₂O₃–2CNT) were prepared by reactive mechanical grinding. The hydriding and dehydriding properties of these samples were then measured, and the effects of Ni, Fe₂O₃, and CNT addition on the hydriding and dehydriding rates of Mg-based alloys were investigated by comparing their hydrogen-storage properties with those of pure Mg and Mg–10 wt% Fe₂O₃.     

Effects of Cr2O3 addition on property improvement of magnesia-spinel refractories used in RH snorkel

The Ruhrstahl-Heraeus (RH) snorkel is one of the most important parts of the RH furnace, which is the primary facility for producing high-quality steel. The magnesia-spinel refractory is the ideal replacement for the classic magnesia-chrome refractory in the RH snorkel. In this study, the effects of Cr₂O₃ addition (0–3 wt%) on properties of magnesia-spinel refractories were investigated. It was found that the addition of Cr₂O₃ results in the acceleration of the densification process and a decrease in the cold strength as well as a significant increase in the hot modulus of rupture. Thus, the solid solution formed with the spinel significantly improves the resistance to thermal shocks, with the greatest improvement being observed after the addition of 2 wt% Cr₂O₃.     

取代2，4，6，8-四氮杂双环［3.3.0］辛烷的合成及硝解

利用苄胺、甲醛、乙二醛的缩合反应以及亚甲基二乙酰胺与乙二醛之间的亲核加成反应合成了两取代的 2 ,4,6 ,8-四氮杂双环[3.3.0 ]辛烷。研究认为在通常的反应条件下 ,其硝解不会得到双环 HMX。文中提出了一种合成双环 HMX的可能途径     

月形波导和加片圆波导的解析分析

采用模匹配方法分析了月形波导和加片圆波导的截止频率。波导中的场采用半数阶Bessel函数展开并令其满足边界条件,从而获得截止频率的特征方程国。根据本文所给公式可求解任意尺寸的月形波导、倒月形波导和加片圆波导的截止频率,并获得稳定的、具有高精度的解。     

Effect of addition time of a superplasticizer on cement adsorption and on concrete workability

The effect of addition time of a naphthalene-based superplasticizer (SNF) on the adsorption behavior on type I Portland cement slurries and on the concrete workability was studied. Test results indicate that the adsorption behavior of SNF on cement particles follows a Langmuir isothermal adsorption model. As the addition time increases, the saturated adsorption amount of SNF decreases sharply at the beginning and then more slowly. In comparison, the concrete workability decreases slightly in the early phase and then falls off abruptly. Most importantly, the transition points in both cases appear to be the same, at about 10–15 min. This strongly suggests that a close relationship exists between the SNF adsorption behavior on cement particles and the workability of concrete. In addition, the optimum addition time of SNF to concrete should be in this period, which corresponds to the beginning of the dormant period of the cement hydration process.     

Improved electrodeposition of CdS layers in presence of activating H2SeO3 microadditive

CdS thin films were deposited electrochemically onto indium tin oxide (ITO)/glass substrates from aqueous solutions containing 0.01 M CdCl₂, 0.05 M Na₂S₂O₃ and 0.02 M Edta-Na₂ at −1.2 mV versus saturated sulfate reference electrode. Depositions were carried out at various temperatures (20, 50 and 80 °С) and different pH (2.5, 3.5 and 4.5) in a three electrode electrochemical cell. All above mentioned electrochemical syntheses were reproduced in presence of H₂SeO₃ microadditive to compare resulted CdS layers. Electrodeposited CdS thin films were characterized by different instrumental techniques to know the influence of deposition conditions on the quality of the obtained layers. It was found that the presence of 0.05–0.5 mM of H₂SeO₃ in the electrolyte changes the mechanism of the CdS film formation that facilitates nucleation and a growth of a more dense and uniform polycrystalline CdS film. Addition of 0.5 mM of H₂SeO₃ into the initial solution allowed us to obtain nearly stoichiometric (sulfur content ~52 at%) CdS films at reduced temperature value of 50 °C vs. higher temperature values used in a conventional electrodeposition process of CdS layers. No Se-containing phases were detected by EDX, Raman and XRD analyses in the CdS films. The presence of H₂SeO₃ tends to rearrange polytype crystalline structure of CdS to more stable hexagonal structure. The band gap value of CdS was increased from 2.3 eV to 2.5 eV as a result of H₂SeO₃ addition.     

The alkyl glycidyl ether as synthetic building blocks

Alkyl glycidyl ether is one of the most useful key materials for industrial applications because the addition reaction of various kinds of nucleophilic reagents to the reactive epoxy bond of the glycidyl ethers has led to glyceryl ether derivatives. Glyceryl ether exhibits many interesting physical and pharmacological properties. The alkyl glycidyl ether can presently be produced at an industrial scale under the phase-transfer catalytic Williamson ether synthesis. We have reviwwed some addition reactions of the alkyl glycidyl ether and possibilities for use as the building blocks for the syntheses of surfactants, pharmaceuticals, etc. that contain glyceryl ether skeletons. Typical examples of alkyl glyceryl ether derivatives include: amino ether as cosmetic material, and isodiglycerin mono- and dialkyl ethers and triglycerin monoalkyl ether as a cosmetic or a pharmacologically useful material, respectively. Another interesting reaction is the rearrangement of the epoxy bond of the alkyl glycidyl ether, which gives alkoxy ketone in a one-pot synthesis.     

稀土添加剂对WC-Co硬质合金孔隙影响的研究

本文根据稀土强化碳化钨—钴硬质合金的实验事实，研究了稀土添加剂对WC－Co硬质合金孔隙度和孔隙尺寸的影响，对稀土添加剂在碳化钨—钴合金中的强化机理进行了探讨．结果表明：加入适当的稀土添加剂可使合金中的总孔腺度降低，较大的B类孔隙基本消失．     

Effect of Brazing Conditions on Microstructure and Mechanical Properties of Al2O3/Ti--6Al-4V Alloy Joints Reinforced by TiB Whiskers

Al2O3 and Ti-6Al-4V alloy were brazed with Ag-Cu-Ti ＋B fillers in different brazing conditions. Effects of brazing temperature, holding time and additive Ti content on joints microstructure and shear strength were investigated by scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, transmission electron microscopy and shear testing. Results indicate that TiCu and Ti（Cu,Al） decrease, but Ti2Cu and -Ti2（Cu,Al） increase in brazing seam with increasing brazing temperature, holding time and additive Ti content. Area consisting of Ti3（Cu,Al）30 and TiO near Al2O3 becomes gradually discontinuous from continuity when brazing temperature rises or holding time extends. As Ti additive content increases, TiO is absent near Al2O3, area consisting of only Ti3（Cu,Al）30 thickens. TiB whiskers are in situ synthesized by Ti and B atoms during brazing process. The brazing temperature, holding time and additive Ti content on joints microstructure influence the joints shear strength directly. The shear strength of joints, obtained at 850 ℃ holding for 10 min, reaches the maximum of 78 MPa. According to the experimental results, phase diagram and thermodynamics calculation, the interface evolution mechanism of the Al2O3/Ti-6Al-4V alloy joint was analyzed.