Protection behavior of fluorine-containing cover gases on molten magnesium alloys

The sulphur hexa-fluoride gas（SF6）, which is commonly used as the cover gas of molten magnesium alloys in the magnesium industry today, has an extremely high global warming potential（GWP）. The protection mechanism of SF6 containing cover gases on molten magnesium alloys was presented. The cover gas protects the melt by reacting with the melt to form a coherent protective film on the melt surface. The film contains MgO and MgF2. Particles containing MgF2 form on the interface between the oxide film and the bulk magnesium alloy, which correspond to the concave areas from the surface observation. These particles increase the Pilling and Bedworth ratio of surface film and enhance the protective capability of the films. Based on the understanding of the mechanism of SF6, a melting technology in a sealed furnace was proposed, and the protection behavior of magnesium alloys in the sealed melting furnace was investigated under the protective atmosphere containing HFC-134a. The morphology and composition of the surface film were also studied. Experiments to evaluate the protective effect of two other fluorine containing gases with low GWPs on AZglD alloy in the sealed furnace were also carried out, and the results show that the new gases are potential substitutes for SF6.     

单轴取向p型半导体CuI薄膜的制备与表征

在室温下用反应沉淀制取了CuI粉体,用溶液生长法在玻璃载体上制备了单轴取向p型半导体CuI薄膜。用XRD、SEM对样品进行了分析,结果表明,CuI粉体为片状结构;晶体薄膜是(111)晶面沿玻璃平行生长的单轴取向马赛克CuI薄膜。阐明了单轴取向CuI薄膜形成的机理。     

新型高碳高铬低镍钢的组织及力学性能研究

基于耐热耐磨钢的工况要求,合理设计钢的化学成分,采用普通铸造法制备出了新型高碳高铬低镍合金铸钢,并对其铸态组织和力学性能进行了研究.结果表明:该钢的铸态组织由块状奥氏体和沿奥氏体晶界呈网状分布的碳化物组成,而奥氏体内未出现弥散析出相；该钢铸态具有好的抗冲击性,其韧度为5.4J/cm2,但其硬度有待提高,洛氏硬度仅为35 HRC.     

纺织剪刀用W9Mo3Cr4V钢镀TiN薄膜的表面性能

为改善纺织剪刀用W9Mo3Cr4V高速钢的表面性能,采用多弧离子镀技术对其进行镀TiN表面处理。以X射线衍射和扫描电镜对镀膜进行微观分析。在载荷500kg、加载时间1min的条件下,用摩擦磨损试验机测试了镀TiN薄膜前后W9Mo3Cr4V钢的耐磨性。在3%NaCl溶液中测试了W9Mo3Cr4V钢镀TiN薄膜前后的极化曲线。结果表明,镀TiN能明显提高W9Mo3Cr4V钢的抗磨损性能以及抗腐蚀性能。     

Optimisation,design and characterisation of a piezoelectric micro suspension

A piezoelectric micro active suspension device has been developed for the application of active isolation of sensitive electronic devices such as frequency generators or inertial sensors. The developed strategy is based on a classical skyhook active damper but adapted and optimised to allow robust implementation onto an adaptive microelectromechanical systems (MEMS). The micro suspension is a silicon beam structure etched in a silicon on insulator (SOI) wafer and is equipped with a pair of piezoelectric transducers obtained from a lead zirconate titanante thin film sandwiched between pairs of electrodes. High performance transducers allow application of the active isolation strategy and demonstrate the possibility to implement skyhook damping with low-voltage control level.     

Study on properties and aggregation structures of deacetylated konjac glucomannan/chitosan hydrochloride absorbent blend gel films

A series of novel blend films of deacetylated konjac glucomannan (d‐KGM) and Chitosan hydrochloride (CHI·HCl) were prepared successfully by using the solvent‐casting technique with different blending ratios of the two polymers. The miscibility and aggregation structure of the blend films were studied by Fourier transform infrared spectroscopy, wide‐angle X‐ray diffraction and scanning electron microscopy. The results indicated that the blend system of d‐KGM and CHI·HCl had a conditional miscibility. A new crystal occurred and hydrogen‐bonding interaction was strengthened when the CHI·HCl content in the blend films was 40%. The effects of deacetylation degree of KGM, acids (the solvent Chitosan dissolved in), temperature, and the mix ratio on the swelling behavior of the blend films were also studied. The blend film KC3 (CHI·HCl content in the blend films was 30%) had not only the highest equilibrium swelling degree (26 times) but also the highest tensile strength, and it could be regarded as a potential absorbent film material. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Semiconducting ground-state of three polymorphs of Mg2NiH4 from first-principles calculations

Magnesium nickel hydrides (Mg₂NiH₄) are the prospective candidates for hydrogen storage and switchable mirror. The hydrides exist in two typical crystallographic forms, the low temperature (LT) phase in monoclinic structure, and the high temperature (HT) phase in cubic structure. LT has two modifications–untwinned (LT1) and microtwinned (LT2) structures. The electronic structures of the three polymorphs of Mg₂NiH₄ are investigated using ab initio calculations based on density functional theory. The calculated band gaps of LT1 and HT are in reasonable agreement with experimental observations and other theoretical predications, while the calculated band gap of LT2 is slightly lower than those of LT1 and HT. Electronic-structure analysis shows that strong interactions exist between Ni and H, whereas the interactions between Mg and H are negligible. The strong ionic character between Mg and NiH₄ complex can be viewed as the origin of the semiconducting ground-state.