Low Electrical Percolation Threshold of Silver and Copper Nanowires in Polystyrene Composites

Silver and copper nanowires have been synthesized using a scalable method of AC electrodeposition into porous aluminum oxide templates, which produces gram quantities of metal nanowires ca. 25 nm in diameter and up to 5 and 10 μm in length for Ag and Cu, respectively. The nanowires have been used to prepare polystyrene nanocomposites by solution processing. Electrical resistivity measurements performed on polymer nanocomposites containing different volume fractions of metal indicate that low percolation thresholds of nanowires are attained between compositions of 0.25 and 0.75 vol %.     

Catalytic oxidation of sulphide ions to elementary sulphur in aqueous solutions over transition metal oxides

The catalytic activity of a wide range of transition metal oxides in oxidation of sulphide ions by air in aqueous medium was studied. Some specific features of the reaction mechanism on some of the studied oxides were considered. The transition metal oxides are promising catalysts for practical application. Some of these oxides will allow the preparation of catalysts possessing activity comparable to that of the cobalt phthalocyanine based catalysts, popular in industrial practice.     

超声波在金属凝固中的应用与发展

简要介绍了超声波及其基本特性，综述了高能超声对金属凝固过程作用方面的研究和应用状况，提出超声处理是改善金属凝固组织，提高力学性能的有效方法，并对21世纪超声凝固细晶技术的前景进行了展望。     

快重离子在石墨中引起表面及体径迹的STM研究

用多种快重离子辐照高定向石墨（HOPG），借助扫描隧道显微镜（STM）系统地研究了表面及体内缺陷，结果表明，离子在表面及解理面上都形成了小丘状的缺陷，且在表面较容易形成，可以用非连续损伤径迹结构来对其进行解释。     

厚断面球铁的声速

论述了影响厚断面球铁声速和声波衰减的各种因素。指出，必须在应力状态下同时考核声速和声波衰减，以作为判别厚断面球铁材质的一种手段。     

连铸铝镇静钢的钢水准备

在连铸生产铝镇静钢时,水口絮流一直是困扰工程技术人员的一个难题.从絮流的原因入手,分析了Al2O3生成的控制.并介绍了几种钢水钙化的方法,从中比较出用复合造渣材料来解决浇铸铝镇静钢的优点.     

金属蒸气法制备聚合物固载Pd－Cu双金属原子簇

为了不使用任何还原剂而获得聚合物固载高分散零价双金属加氢催化剂，利用金属蒸气法制备了３种不同Ｐｄ／Ｃｕ质量比的聚合物固载双金属原子簇。透射电镜（ＴＥＭ）和Ｘ衍射（ＸＲＤ）测定表明，Ｐｄ－Ｃｕ原子簇粒度很小，平均直径小于３．０ｎｍ。Ｘ射线光电子能谱（ＸＰＳ）表明，Ｐｄ和Ｃｕ均为零价态。Ｐｄ－Ｃｕ原子簇在异丙叉加氢反应中具有很高的活性和选择性。这些结果提供了令人信服的证据，即金属蒸气法可用于在聚合物孔穴内直接而温和地置入小的零价金属原子簇，而且这样制备的聚合物固载金属原子簇很适合于催化应用。     

Studies on the interactions of metal oxides and Na2 SO4 at 1100 and 1200 K in oxygen

The interaction of different metal oxides such as Co₃O₄, NiO, Al₂O₃, Cr₂O₃, Fe₂O₃ and SiO₂ with Na₂SO₄ at a temperature of 1100 and 1200 K in flowing oxygen has been studied. The thermogravimetric studies for each system were carried out as a function of Na₂SO₄ in the mixture. The presence of different constituents in the reaction products were identified by X-ray diffraction analysis and the morphologies of the reaction products were characterized using metallography and scanning electron microscopy (SEM). The formation of products was also investigated by thermodynamic computation of free energies of the reactions and the study of relevant equilibrium phase diagrams. The soluble species in the aqueous solutions of the reaction products were determined quantitatively using atomic absorption spectrophotometry. The high temperature interaction products usually contain a 3-phase structure namely, Na₂O·M₂O _x , M₂O _x and metal sulphide and/or metal sulphate. The formation of Na₂O·M₂O _x depends upon the solid state solubility of metal oxide in the molten salt at high temperatures. Under limited solubility conditions Na₂O·M₂O _x is invariably formed, but as soon as this condition is relaxed the oxide. M₂O _x , precipitates and forms a separate phase.     

Recrystallization/precipitation behaviour in microalloyed steels

Microalloyed high-strength low-alloy (HSLA) steels contain additions of Nb, V, Ti, or in combination, in amounts of 0.01 to 0.1 weight percent to improve mechanical properties, which are strongly dependent on the thermomechanical interaction taking place in the course of rolling mill processes. The recrystallizatian of hat-twisted austenite has been investigated in a cylindrical specimen (f 6×50 mm) machined from hat rolled plates of 0,052 wt % Niobium microalloyed steel. Continuous and interrupted torsion test were carried out in the temperature range 1123 K to 1173 K after a solution treatment of 1.5 minutes at 1423 K and torque-twist data were analysed. The various methods were discussed for obtaining results from torsion tests. The effect of precipitation kinetics was appreciated by way of connection t_p/t_p(red), where t_p is the experimental measured time for the peak stress and t_p(red) is the newly defined reduced time. The softening ratio X and time t_0.05R for start of static recrystallization were established.

The correlation between precipitation and recrystallization is presented as a graphs for chosen requirements (temperature of austenitization, carbon and niobium content and strain rate). If temperature goes below 850°C, the restoration processes are hardly suppressed, both are limited by diffusion and Nb(CN) precipitation, which are extended dynamically in the range of strains rates 10⁻² to 1 s⁻¹.

In the present paper, an attempt is made to derive the PRTT diagram and to define all mathematical equations for describing recrystallization times t_0.05R, t_0.5R, t_0.95R and t_0.05P for the start of precipitation. In real metal forming processes such as the hot rolling of plates or strips the knowledge of these parameters and results is extremely important for the the correct microstructure and sheet quality to be obtained.