C. Liu and G.T. Burstein (Department of MateriaIs Science and Metallurgy
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University of Cambridge
,
Pembroke Street
,
Cambridge CB2 3QZ
,
United Kingdom)
金属学报(英文版)
The passivity of guillotined aluminium electrode is enhanced in alkaline electrolytes by SiO32-. It is proposed that the formation of a complete aluminosilicate gel is responsible for this phenomenon. Dissolution of the metal proceeds via the existing film and the dissolution product reacts with SiO_3~2- ions to form the gel. Under galvanostatic polarisation, significant amount of the gel is formed when the applied anodic i > 10mA cm-2. This gel layer can then be transformed into barrier-type of oxide film, thus contributing to the initial stage of the high voltage anodisation.
关键词:
passivity
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null
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null
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null
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null
S Narayan
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A Rajeshkannan
钢铁研究学报(英文版)
An experimental investigation on the workability behaviour of sintered Fe-035C steel preforms under cold upsetting, have been studied in order to understand the influence of aspect ratio and lubrication condition on the workability process. The above mentioned powder metallurgy sintered preform with constant initial theoretical density of 84% of different aspect ratios, namely, 04 and 06 respectively were prepared using a suitable die-set assembly on a 1 MN capacity hydraulic press and sintered for 90 min at 1200 ℃. Each sintered preform was cold upset under nil/no and graphite frictional constraint, respectively. Under the condition of triaxial stress densification state, axial stress, hoop stress, hydrostatic stress, effective stress and formability stress index against axial strain relationship was established and presented in this work. Further more, attained density was considered to establish formability stress index and various stress ratio parameters behaviour.
关键词:
powder metallurgy
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failure analysis
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plastic behaviour
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workability
International Journal of Hydrogen Energy
A highly active photocatalyst based on g-C(3)N(4) coated SrTiO(3) has been synthesized simply by decomposing urea in the presence of SrTiO(3) at 400 degrees C. The catalyst demonstrates a high H(2) production rate similar to 440 mu mol h(-1)/g catalyst in aqueous solution under visible light irradiation, which is much higher than conventional anion doped SrTiO(3) or physical mixtures of g-C(3)N(4) and SrTiO(3). The improved photocatalytic activity can be ascribed to the close interfacial connections between g-C(3)N(4) and SrTiO(3) where photo-generated electron and holes are effectively separated. The newly synthesized catalyst also exhibited a stable performance in the repeated experiments. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
关键词:
Carbon nitride;Photocatalyst;Visible light;SrTiO(3);tio2 nanotube photocatalyst;hydrogen-production;water;generation;oxynitride
韩娇
,
李莉
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杨金文
,
周旺松
,
俞峰
,
曹文全
钢铁研究学报
doi:10.13228/j.boyuan.issn1001-0963.20140400
利用Gleeble-3800热模拟变形试验机,对高温轴承钢G80T的动态再结晶行为及相关力学性能进行了研究.通过对该钢在1050℃下以10s-1的变形速率进行0％～70％的不同形变量的单道次压缩,研究了不同形变量下热变形钢的微观组织结构及硬度.结果表明:当形变量在20％时,无动态再结晶发生;当形变量达到40％时,热变形组织出现了部分的再结晶晶粒;随着形变量的进一步加大,再结晶晶粒数目增多,形变量达到60％后,形变组织形成了平均晶粒尺寸为2.8μm的完全再结晶组织.同时由于形变和晶粒尺寸大幅度细化,钢中的碳化物也随着形变量的增加而逐步减少.通过对压缩应力-应变曲线软化行为的分析,认为该钢的再结晶属于动态再结晶;在1050℃进行60％的形变可以实现该钢的完全动态再结晶,将平均晶粒尺寸从原始的22μm细化到2.8μm,同时将钢的硬度从820HV提高到895HV.研究结果表明,动态再结晶是细化高温轴承钢G80T晶粒尺寸和提高性能的一种有效措施.
关键词:
高温轴承钢
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热压缩
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动态再结晶
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晶粒细化
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显微硬度
QIAO Lijie LIU Rui XIAO Jimei University of Science and Technology Beijing
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Beijing
,
China
金属学报(英文版)
The effects of stress components on nucleation sites and propagation directions of stress cor- rosion cracks in brass were investigated with specimens under mode Ⅱ and mode Ⅲ loadings. The results indicated that under mode Ⅱ loading,stress corrosion cracks nucleated on the site with maximum normal stress component and propagated along the plane perpendieular to the maximum normal stress,under mode Ⅲ loading,the stress corrosion crack was not evident on the 45°plane due to the general corrosion in aqueous solution with high NH_4OH concentra- tion,while stress corroded in aqueous solution with low NH_4OH concentration, numerous cracks with spacings of 10—150μm were found on the 45°plane with maximum normal stress and no stress corrosion cracks was observed on the plane with maximum shear stress.
关键词:
stress corrosion cracking
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null
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null
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null
冯阳阳
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崔红
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李瑞珍
,
吴书峰
宇航材料工艺
doi:10.3969/j.issn.1007-2330.2011.02.029
选取两种国产T300级PAN基碳纤维,轴棒法制备4D预制体,以高温煤沥青为前驱体,采用液相浸渍-炭化以及石墨化相结合的技术制备C/C复合材料(密度≥1.95 g/cm<'3>),研究了C/C复合材料从室温(RT)到800℃的热导率及其影响因素.研究表明,在实验温度范围内C/C复合材料的热导率随温度升高而降低,由于原材料自身特性和预制体编织结构具有方向性,使C/C复合材料的导热性能表现出各向异性,径向热导率明显高于轴向;密度高、开孔率小、石墨化程度高的C/C复合材料由于晶粒间连通状态好,微晶结构趋于完整,材料的热导率增大;以低压热处理为最终处理工艺的C/C复合材料热导率略有提高;采用国产T300级与东丽,1300碳纤维制备的C/C复合材料的热导率相当.
关键词:
碳纤维
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C/C复合材料
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轴棒法
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热导率
