Corrosion Resistance of Ti_3Al/BN Abradable Seal Coating

Ti–Al mixed powder(Ti:Al = 3:1 in atomic ratio) and Ti3 Al intermetallic alloy powder mechanically clad hexagonal BN to fabricate Ti Al/BN and Ti3Al/BN composite powders. The corresponding porous abradable seal coatings(named as TAC-1 and TAC-2, respectively) were deposited using vacuum plasma spray(VPS) technology, and their corrosion behavior was studied via salt spray corrosion and electrochemical tests. Phase compositions and microstructures of these coatings before and after corrosion were characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM) facilitated with energy dispersive X-ray spectrometer(EDS). The results showed that spontaneous passivation of TAC-1 and TAC-2 granted the coatings excellent corrosion resistance than that of commercial Al/BN coating. Additionally, TAC-2 exhibited higher corrosion potential(Ecorr) and breakdown potential(Ebp) but a lower corrosion current density(icorr) than TAC-1. A small quantity of the corrosion product(Al(OH)3and Al O) could be detected on the surface of TAC-1, while no corrosion product appeared in TAC-2. The non-uniform elements distribution in the metal matrix of TAC-1 resulted in localized corrosion and relatively poor corrosion resistance compared to TAC-2.     

0Cr13Ni8Mo2Al钢与铝合金和钛台金接触腐蚀与防护研究

通过测定0Cr13Ni8Mo2Al钢与铝合金（LY12）和钛合金（TC4）组成的电偶对的电偶电流的方法,研究了0Cr13Ni8Mo2Al钢在使用中与铝合金和钛合金接触时发生电偶腐蚀的敏感性。研究结果表明:0Cr13Ni8Mo2Al钢与铝合金接触时会产生严重的电偶腐蚀,必须进行防护处理方可使用;与钛合金接触时产生的电偶腐蚀很轻微,可以不进行防护。0Cr13Ni8Mo2Al钢表面进行镀镉钛防护后,与铝合金接触时的电偶电流密度大为减小,相差近10倍;采用环氧锌黄底漆、XM-33-4双组分密封胶防护可以有效地防止0Cr13Ni8Mo2Al钢与铝合金和钛合金接触产生的电偶腐蚀。     

活性γ型宫内节育器中消炎痛对铜与不锈钢电偶腐蚀的影响

针对活性γ型宫内节育器,研究了在ＰＨ６－８的生理盐水中消炎痛对铜与不锈钢的电偶腐蚀的影响。消炎痛不影响铜的自然腐包电位及其随溶液ＰＨ的升高而正移的规律;     

PEMFC燃料电池三级电堆的装配分析

以提高PEMFC燃料电池电堆性能为目的,研究了电堆组装过程中加载方式和载荷对电堆接触电阻及电堆性能的影响。利用有限元分析软件ANSYS Workbench对三级电堆的装配过程进行有限元分析。分析了几种不同大小的载荷及不同的加载方式的装配对电堆性能的影响,对比了这几种情况下燃料电池堆的核心部件膜电极(MEA)组件的变形情况及应力分布情况,得出电堆的最佳装配载荷。该结果可为燃料电池电堆的装配提供较好的参考依据。     

Galvanic corrosion of aluminium alloy members of bridge guiderails under severe atmospheric exposure conditions

ABSTRACT

Aluminium alloys are nowadays preferred as materials for bridge guiderails especially for bridges connecting oceanic islands or spanning inlets due to their inherent corrosion resistance. But because of the limited mechanical strength of aluminium alloy, fasteners of guiderail members are made from steel materials. It has been found that contact between bare steel fasteners and aluminium alloy members can cause galvanic corrosion in the aluminium alloy. Research was carried out to investigate the capability of different surface treatments on fasteners and aluminium alloy members to inhibit galvanic corrosion under atmospheric exposure for periods of one and three years. It was found, among other results, that stainless steel fasteners treated with zinc flake coating were the most effective inhibitors of galvanic corrosion on aluminium alloy members.     

Bi and Te thin films synthesized by galvanic displacement from acidic nitric baths

Bismuth (Bi) and tellurium (Te) thin films were formed by galvanic displacement of different sacrificial iron group thin films [i.e. nickel (Ni), cobalt (Co) and iron (Fe)] where the formation was systematically investigated by monitoring the change of open circuit potential (OCP), surface morphology and microstructure. The surface morphologies and crystal structures of galvanically displaced Bi or Te thin films strongly depended on the type and thickness of the sacrificial materials. Continuous Bi thin films were successfully deposited with the sacrificial Co. However, dendrites and nanoplatelets were formed from the Ni and Fe thin films. Te thin films were synthesized with all the three sacrificial thin films. Chemical dissolution rate of the sacrificial thin films and mixed potential strongly influenced formation of Bi or Te thin films.     

The origin of the complex character of the Ohmic impedance

The local and global Ohmic response for an electrode exhibiting geometry-induced potential and/or current distributions has recently been shown to be represented by a frequency-dependent complex impedance. A physical explanation for this result is provided in terms of the radial contribution to local current density and the decrease in current density along the current lines. Experiments performed with Cu/Al and Mg/Al galvanic couples show that, in regions where a radial current density does not exist, the local Ohmic impedance is independent of position; whereas, in regions where the radial current density cannot be neglected, the local Ohmic impedance is a function of position. Simulations performed on recessed electrodes show that, even in the absence of a radial current, an axial variation of current density gives rise to a complex Ohmic impedance. The complex character of the Ohmic impedance shows that an equivalent circuit, using the usual two-terminal resistor to represent the Ohmic contribution of the electrolyte, provides an inadequate representation of an electrode with geometry-induced current and potential distributions.     

Inferring the distribution of iron oxidation species on mineral surfaces during grinding of base metal sulphides

Electrochemistry plays an important role in the flotation of base metal sulphide minerals. During grinding a galvanic interaction occurs between minerals and grinding media and controls the iron contamination on mineral surfaces, which depresses mineral flotation significantly. In this study, the galvanic interaction was quantified by measuring the iron oxidation species originated from grinding media by ethylene diamine-tetra acid (EDTA) extraction in single mineral and mixed mineral systems. It was found that the extent of galvanic interaction between minerals and grinding media was intimately associated with the electrochemical reactivity of minerals. The nobler the mineral, the stronger the galvanic interaction with grinding media, and the higher the amount of iron oxidation species from grinding media. For both galena and chalcopyrite a linear relationship was observed between the amount of iron oxidation species and flotation recovery in single mineral systems. This relationship was able to predict the iron oxidation species on galena and chalcopyrite surfaces when they were mixed with pyrite separately. The distribution of iron oxidation species onto the two minerals in the mixture changed with the ratio of the mineral surface areas and was correlated with mineral flotation recovery. The major cathodic mineral in the mixture was dictated by the combination of mineral surface area and reactivity and drew iron oxidation species from the grinding media.     

Looking, recalling, and GSR as a function of defense.

10 pictures were viewed for 10 sec. each, during which the eye fixations were photographed and GSR was recorded. An independent assessment was made for each of 16 Ss of the defenses of isolation and repression. The defense of isolation was strikingly associated with venturing to look around more, and the defense of repression with looking around less: in contrast to repressors, isolators looked at the "ground" as well as the figure; they scattered their fixations and they made bigger jumps from 1 fixation to the next. Isolation was better than repression for the recall of sexual content. No strong trends emerged from correlations of GSR and defense ratings. Some looking measures correlated significantly with standard Rorschach scores. The findings seem consistent with results for cognitive styles as well as with clinical understanding of the defenses. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bimetallic Pt–Au thin film electrocatalysts with hierarchical structures for the oxidation of formic acid

A series of bimetallic Pt–Au thin films with different Pt/Au ratios were fabricated on glassy carbon (GC) substrates through galvanic replacement reactions between hierarchical Co thin films prepared by cyclic voltammetric deposition and mixed solutions of HAuCl₄ and H₂PtCl₆. The morphologies of the as-prepared Pt–Au thin films resemble those of the sacrificial Co templates, and the Pt/Au ratios in the films are dependent on the HAuCl₄/H₂PtCl₆ molar ratios in the mixed solutions. Because of good stability and excellent synergistic effect of Au and Pt, the bimetallic films with novel structures display unexpected high catalytic activity for the oxidation of formic acid. The as-prepared hierarchical Pt–Au micro/nanostructures are expected to find applications as catalysts in direct formic acid fuel cells (DFAFCs).