Influence of alloying elements on microstructure and microhardness of Mg-Sn-Zn-based alloys

The phase evolution in （88%-91%）Mg-8%Sn-l%Zn-X （X=A1, Mn and/or Ce） system was analyzed via CALPHAD method and simulations were used in precise selection of the chemical composition. The influence of the addition of different alloying elements such as A1, Mn and Ce on the microstructure and microhardness of Mg-8%Sn-l%Zn-based alloys was investigated. Combined addition of A1 and Mn shows features distinct from separate addition of A1 or Mn. Additions of l%AI and l%Mn to base alloy result in the formation of massive A1-Mn phase in a-Mg matrix grains. Addition of Ce element can refme the second eutectic precipitates and form intermetallic compounds with Sn. Fine rod-like Sn-Ce phase presents mainly on the grain boundaries and plays a role in inhibiting grain growth. The effects of alloying elements on Vickers microhardness and indentation size effect of base alloy were examined.     

Fabrication of cobalt aluminum-layered double hydroxide nanosheets/carbon spheres composite as novel electrode material for supercapacitors

A new design route was presented to fabricate cobalt aluminum-layered double hydroxide(CoAl-LDH) thin layers which grow on carbon spheres(CSs) through a growth method. The CoAl-LDH thin layers consist of nanoflakes with a thickness of 20 nm. The galvanostatic charge–discharge test of the CoAl-LDH/CSs composite shows a great specific capacitance of 1198 F/g at 1 A/g (based on the mass of the CoAl-LDH/CSs composite) in 6 mol/L KOH solution, and the composite displays an impressive specific capacitance of 920 F/g even at a high current density of 10 A/g. Moreover, the composite remains a specific capacitance of 928 F/g after 1000 cycles at 2 A/g, and the specific capacitance retention is 84%, indicating that the composite has high specific capacitance, excellent rate capability and good cycling stability in comparison to pristine CoAl-LDH.     

Asymmetric capacitor based on superior porous Ni-Zn-Co oxide/hydroxide and carbon electrodes

Hierarchical porous multi-phase Ni-Zn-Co oxide/hydroxide is synthesized by using metal-organic framework-5 (MOF-5) as the template. Hierarchical porous carbon is obtained by the facile direct decomposition of the MOF-5 framework with phenolic resin. The structures and textures are characterized by X-ray diffraction, high-resolution transmission electron microscopy, scanning electron microscopy, and nitrogen sorption at 77 K. An asymmetric capacitor incorporating the Ni-Zn-Co oxide/hydroxide as the positive electrode and the porous carbon as the negative electrode is fabricated. A maximum energy density of 41.65 Wh kg⁻¹ is obtained, which outperforms many other available asymmetric capacitors. The asymmetric capacitor also shows a good high-rate performance, possessing an energy density of 16.62 Wh kg⁻¹ at the power density of about 2900 W kg⁻¹.     

The formation of active species for oxidative dehydrogenation of propane on magnesium molybdates

Pure and mixed magnesium molybdate phases (MoO₃, MgMoO₄, and MgMo₂O₇) have been examined for the oxidative dehydrogenation reaction of propane. The results are very sensitive to the stoichiometry and method of preparation. The catalysts exhibiting superior activity and selectivity are characterized by a unique temperature-programmed reduction peak that is not present for the poorly active or selective catalysts. Mixtures of MgMoO₄ and MoO₃ or MgMoO₄ and MgMo₂O₇, materials that perform poorly by themselves, show significant improvements in performance upon heating. The solid-state interactions leading to these improvements correspond to the appearance of the characteristic reduction peak. The results suggest that the beneficial synergistic effects seen with mixtures of inactive phases are due to formation of a new phase or species, rather than remote communication between phases (e.g., oxygen spillover). This revised version was published online in November 2006 with corrections to the Cover Date.     

不同取样方向AZ31B镁合金应变率效应

采用分离式Hopkinson压杆获得了冲击压缩方向与热轧态A231B镁合金板材法向分别成90°、45°及0°的动态应力一应变曲线，利用光学显微镜及透射电子显微镜对微观组织演化过程进行了分析。结果表明：应变率约为1 200 s-1，压缩方向与板面法向成90°时，孪晶的面积分数随应变量的增大逐渐增加，孪生是主要变形机制，其曲线为凹型；压缩方向与板面法向成45°及0°时，其塑性变形以位错滑移为主，曲线形状分别为近似线型和凸型；应变率约为2 800 s-1，压缩方向与板面法向成90°时，孪晶面积分数迅速增加，大多数晶粒取向发生7改变，有利于滑移，其曲线由较低应变率的凹形变为凸型。     

油藏工程学的发展现状及认识

80年代初期 ,国内诞生的油藏工程专业 ,在将近 2 0年的时间里 ,获得了飞速的发展。它经历了两个阶段 ,简单定量阶段和精确定量阶段。简单定量方法在现代研究中仍占主要地位。随着数学模型的完善及计算机技术的发展 ,精确定量的方法得到了较大程度的发展。随着油藏开发工作的进一步加深 ,精确定量的方法必将占据主要地位。     

海水环境下混凝土耐久性研究

采用岩相分析、X射线衍射分析、化学分析和扫描电镜/能谱分析等方法,对珠江三角沿海地区某30年跨海大桥桥墩混凝土开裂的原因及其耐久性问题进行研究。研究结果表明,该海工混凝土含有碱活性细集料,在海水环境下发生了碱-集料反应;海水的镁盐也侵蚀了混凝土,在粗裂缝的表面生成了大量的氢氧化镁沉淀;碱-集料反应与海水镁盐侵蚀等复合作用导致混凝土开裂。这是我国首例海水环境下混凝土因细集料发生碱-集料反应,并受镁盐侵蚀而造成复合破坏的报道。海工混凝土需综合考虑海水环境的影响,在选用集料时,应检测其碱活性,避免使用具有碱活性的集料。具有碱活性的细集料对混凝土耐久性的影响需引起重视。     

纳米材料在锂离子电池中的应用进展

介绍了纳米材料在锂离子电池中的应用及进展情况。主要介绍了在锂离子电池中用作阴极材料的锰钡矿型MaO2纳米材料、聚吡咯包覆尖晶石型LiMn2O4纳米管、聚吡咯／V2O5纳米复合材料，用作阳极材料的碳纳米管、纳米掺杂碳材料、纳米二氧化锡，用作固态电解质的纳米填料修饰聚氧乙烯基复合材料等几种新型纳米化学电源材料的制备、结构、形貌以及电化学性质。     

Ultradispersed particles in heavy oil: Part I, preparation and stabilization of iron oxide/hydroxide

In this study, ultradispersed colloidal particles of iron oxide/hydroxide were prepared in-situ in heavy oil matrices adopting (w/o) microemulsion approach for nanoparticle preparation detailed in our previous work [1-3]. The effect of composition of heavy oil on the stable concentration of colloidal particles, particle uptake, was investigated. The following trends in particle uptake were common between the (w/o) microemulsions and the heavy oil matrices. An optimum water content was found for which a maximum particle uptake was attained. Particle uptake increased as the content of vacuum residue, VR, and precursor salt concentration increased. Vacuum residue contributes high asphaltene content, which acts as a surface active agent. The iron oxide/hydroxide particles had been recently shown to effectively remove H₂S_(g) from oil phase [4]. H₂S_(g) is a hazardous by-product of heavy oil recovering and upgrading which should be removed as soon as it forms. Results pertaining to H₂S_(g) removal from heavy oil employing ultradispersed particles are communicated in Part II of this study.     

Efficacy of different chemicals on shelf life extension of parsley stored at two temperatures

Four different chemical treatments, GA₃, 1‐MCP, essential oils and nano‐Cu, were applied immediately after harvest to Petroselinum crispum (Mill) plants. The efficacy of the above chemicals on shelf life extension of parsley stored at 5 °C and 20 °C was determined by analysing physiological and biochemical factors that determine quality standards of storage fresh parsley. Nonsprayed parsley revealed the highest loss of weight, ascorbic acid, pigments and an enhancement of CO₂ production and lipid peroxidation at 5 °C and 20 °C of storage. Nano‐Cu was more effective for delaying weight loss and revealed a better storage capacity. GA₃, 1‐MCP and essential oils sprays were more effective in ascorbic acid retention at 20 °C than at 5 °C, whereas all substances protect samples from lipid peroxidation. Essential oils were more clearly inhibitory towards both total viable counts and yeast infection. Our results suggest that GA₃, 1‐MCP, essential oils and Nano‐Cu exert their function through different mechanisms during ripening and could provide an effective and complementary means for maintaining high‐quality parsley leaves after harvest.