Synergistic Effect of Mo,W, Mn and Cr on the Passivation Behavior of a Fe-Based Amorphous Alloy Coating

In this work, the electrochemical behaviors of SAM2 X5 Fe-based amorphous alloy coating and hard chromium coating were comparatively studied in 3.5 wt% Na Cl solution. In comparison with the hard chromium coating, the SAM2 X5 coating exhibited a wider and stable passive region with lower passive current density in the potentiodynamic polarization and showed a considerably lower current density at different anodic potentials in the potentiostatic polarization. In order to understand the passivation mechanism of the Fe-based amorphous coating, the components of the passive films formed at various polarization potentials were examined by X-ray photoelectron spectroscopy. The synergistic effect of Mo, W, Mn and Cr in the passive films was systemically analyzed. It has been revealed that Mo and W facilitate the formation of compact and stable Cr_2O_3 passive film at lower potentials, and the substantial enrichment of Mn in the passive film enhances the passivation ability at relatively higher potentials. The deep understanding of the passivation characteristics in multicomponent alloy systems could provide a guide for the design of corrosion-resistant amorphous alloy coatings for engineering applications.     

Modification of Roll Pass Design of Low Pearlite,Fine-Grained Sheet Steel Using Numerical Modeling and Processing Maps

Abstract

The main objective of this pass design is to achieve fine-grained structure with high strength properties and good ductility for 2.0 mm thickness steel sheet on a six stand finishing mill. Numerical modeling is used to evaluate the different rolling parameters while processing maps are used to determine a workability “window” in which dynamic recrystallization must occur.

The existing rolling parameters would not lead to a dynamically recrystallized structure. The proposed technique retains the sequence of reduction in thickness at the working temperatures, while it diminishes the rotational speed of the first stand and consequently all the other stands. The first stand is proposed to rotate with 25 rpm at 7.2 s-1 rate of deformation. The final rotational roll speed would be 177 rpm at stand no. 6 with 83.4 s-1 rate of deformation at 850 °C. Rolling force and torque needed in the proposed technique are lower than those in the existing ones at most of the passes. The proposed technique saves energy as it reduces the power consumption.

Le principal objectif de cette conception de passe de laminoir est d'obtenir une structure à grain fin avec des propriétés de résistance élevée et une bonne ductilité pour une tôle d'acier d'une épaisseur de 2.0 mm, sur un laminoir finisseur à six cages. On utilise la modélisation numérique pour évaluer les différents paramètres de laminage alors qu'on utilise les plans de formage pour déterminer une "fenêtre” de fabricabilité dans laquelle doit se produire une recristallisation dynamique.Les paramètres actuels de laminage ne peuvent conduire à une structure dynamiquement recristallisée. La technique proposée retient la séquence de réduction en épaisseur aux températures d'opération, tout en diminuant la vitesse de rotation de la première colonne et, par conséquent, de toutes les autres colonnes. On propose que la rotation de la première colonne soit de 25 rpm, avec un taux de déformation de 7.2 s-1. La vitesse du dernier rouleau serait de 177 rpm à la colonne no. 6, avec un taux de déformation de 83.4 s-1, à 850 °C. La force de laminage et le moment de torsion nécessaires pour la technique proposée sont plus bas que ceux qui existent déjà pour la plupart des passes. La technique proposée conserve l'énergie puisqu'elle réduit la consommation de pouvoir.     

Dendritic SBA-15 supported Wilkinson's catalyst for hydroformylation of styrene

After PAMAM (polyamidoamine) dendrimers have been successfully grown in SBA-15 mesoporous materials, Wilkinson's catalyst (RhCl(PPh₃)₃) precursor has been tethered on these dendritic supports to produce heterogeneous catalysts for hydroformylation reaction of styrene. SBA-15 has been functionalized by two methods. In the passivation method, the silanols outside the SBA-15 pores have been passivated to preclude the rhodium precursor to be tethered outside the channels. The rhodium catalysts supported in the pore channels of this passivated SBA-15 show positive dendritic effects in enhancing the catalytic activity, regio-selectivity and stability of the catalyst by minimizing the leaching of the rhodium complex catalyst from the catalyst support to the liquid-phase media.     

Elucidation of corrosion failure mechanisms of coated phosphated steel substrates

Coatings are commonly believed to protect metal surfaces from corrosion based on some combination of their barrier properties and electrochemical properties. Various physical and electrochemical tests were performed on seven different coatings (latex, alkyd, 2-PK epoxy, and electrocoat) to determine which properties were the main determinants of corrosion resistance in continuous and cyclic corrosion tests. Physical property tests and AC electrochemical tests were all related to barrier behavior, while DC electrochemical tests were related to electrochemical behavior. DC electrochemical properties are commonly associated with inhibitor chemistry, but can be broadly related to all components of the paint. These test results were compared with corrosion test results from both continuous (B-117) and cyclic (GM9540) accelerated tests. The best correlation was seen with a model emphasizing barrier behavior with a secondary component relating to electrochemical protection. Presented at 2007 FutureCoat! Conference, sponsored by Federation of Societies for Coatings Technology, October 3–5, 2007, in Toronto, Ont., Canada.     

黄铜矿细菌浸出机理及钝化原因研究进展

细菌冶金技术由于成本低、污染少、流程短等优点,越来越受到人们重视,由于在常温下黄铜矿的细菌浸出速率较慢,有必要研究提高黄铜矿浸出速率的方法。综述了黄铜矿的细菌浸出机理以及黄铜矿的钝化原因。研究结果表明黄钾铁矾、硫层、中间产物层、高的溶液还原电位和黄铜矿稳定的晶体结构可能是黄铜矿细菌浸出过程中的钝化原因。     

过渡期清洁汽油的生产技术

综合论述了国内外催化汽油脱硫技术进展,讨论了催化汽油中硫的类型和含量分布,对过渡期催化汽油脱硫的新工艺进行了研究,论证了与传统加氢脱硫技术相比的成本优势。     

Two-dimensional LBIC and internal quantum efficiency investigations of porous silicon-based gettering procedure in multicrystalline silicon

In this work, a porous silicon-based gettering technique was applied to multicrystalline silicon (mc-Si) wafers. Porous silicon (PS) was formed by the stain-etching technique and was used as a sacrificial layer for efficient external purification technique. The gettering procedure consists of achieving a PS/mc-Si/PS structure that undergoes a heat treatment at 900 °C for 90 min in an infrared furnace under a N₂ ambient. After removing the PS layers, mc-Si solar cells were realized. The effect of the gettering procedure was evaluated by means of the laser beam-induced current (LBIC) mapping, the internal quantum efficiency (IQE) mapping and the dark current-voltage (I-V) characteristic. Consequently, LBIC and IQE images show an enhancement of the gettered sample as compared to a reference untreated one. The serial resistance and the shunt resistance carried out from the dark I-V curves confirm this gettering-related solar cell improvement.     

Study of electrical properties of oxidized porous silicon for back surface passivation of silicon solar cells

Back surface passivation becomes a key issue for the silicon solar cells made with thin wafers. The high surface recombination due to the metal contacts can be lowered by reducing the back contact area and forming local back surface field (LBSF) in conjunction with the passivation with dielectric layer. About 3×10^-7 m thick porous silicon (PS) layer with pore diameter mostly of 1×10^-8–5×10^-8 m was formed by chemical etching of silicon using the acidic solution containing hydrofluoric acid (HF), nitric acid (HNO₃) and De-ionized water in the volume ratio 1:3:5 at 298 K for which etching time was kept constant for 360 s. Electrical properties of oxidized PS was studied through the current–voltage (I–V) and capacitance–voltage (C–V) characteristics of the metal–insulator–semiconductor (MIS) device in which the oxidized PS was used as an insulating layer and the results were further analyzed. The C–V curves of all the studies MIS devices showed the negative flatband voltage varying from -2 to , confirming that the oxidized layer of PS has fixed positive charge.     

Effect of hydrogen dilution on intrinsic a-Si:H layer between emitter and Si wafer in silicon heterojunction solar cell

In silicon heterojunction solar cells, a thin intrinsic amorphous-silicon (a-Si:H) buffer layer between a doped emitter and a c-Si wafer is essential to minimize carrier recombination. This study examines the effect of H₂ dilution on the properties of the intrinsic a-Si:H layers deposited on Si wafers by plasma-enhanced chemical vapor deposition. A H₂/SiH₄ ratio of 24 led to improvements in the quality of intrinsic a-Si:H films and in the performance of passivation compared to a-Si:H film without H₂ dilution. A high H₂-dilution ratio, however, degraded the passivation of the a-Si:H film. The Si heterojunction solar cells with an optimal intrinsic a-Si:H layer showed an efficiency of 12.3%.     

电解二氧化锰用阳极材料的发展与应用

详尽地讨论了电解二氧化锰生产中所遇到的问题以及电解用阳极材料的发展和应用。阳极材料的自身特性不仅决定了它的实用寿命和相应电解过程中的各项参数,而且不同阳极材料对EMD的电化学性能和纯度有直接的影响。针对阳极易钝化的特点,介绍了有关以钛为基体的多种阳极材料的研究。