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锌及锌覆盖层户外大气暴露腐蚀行为的研究 总被引:5,自引:0,他引:5
户外大气暴露腐蚀造成了损失巨大,研究其腐蚀行为与规律意义重大.通过户外大气暴露腐蚀数据统计分析及腐蚀产物分析,确定了影响锌及锌覆盖层在我国典型地区大气暴露腐蚀行为的最主要的环境因子,在腐蚀动力学、腐蚀机理、腐蚀产物等方面系统研究了锌及锌覆盖层在我国典型地区的大气腐蚀规律.结果表明,相对湿度、SO2、Cl-是影响锌及锌覆盖层在北京、武汉、江津、广州典型地区大气腐蚀行为的主要环境因子.锌及锌覆盖层在上述典型地区大气腐蚀动力学以线性为特征,且腐蚀速率:江津>广州>武汉>北京,与这些地区在试验时间SO2沉积率大小排列次序(江津>广州>武汉>北京)相对应.锌及锌覆盖层在上述典型地区大气暴露主要腐蚀产物为:Zn4SO4(OH)6·5H2O,另含有少量Zn5Cl2(OH)8·H2O及Zn4Cl2(OH)4SO4·5H2O. 相似文献
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用冷喷涂技术制备Cu-Cu2O涂层,研究了其在不同海水环境下的极化行为,并建立了涂层的腐蚀过程数学模型。结果表明:在浸泡的初期Cu2O促进了涂层的局部腐蚀;随着浸泡时间的增加局部腐蚀产物进一步促进了表面氧化膜的形成;在非搅拌的静态环境下,涂层的腐蚀受CuCl2-扩散的控制;Cl-促进了涂层的腐蚀,阻碍氧化膜的形成,且Cl-对CuCl的络合是Cl-浓度的一级反应;在CuCl向Cu2O转变的过程中产生H+,使电极表面附近溶液的pH值降低,阻碍氧化膜的形成和降低耐久性,而在溶液中加入Na2B4O7-H3BO4缓冲体系,能有效地提高氧化膜的击破电位。根据本文提出的反应过程数学模型进行计算的结果,与实验结果具有很好的相符性。 相似文献
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研究镁材微弧氧化膜在含Cu2+介质中的腐蚀行为对扩大其使用范围具有十分重要的意义。采用微弧氧化技术对纯镁材进行表面硅酸盐氧化处理,制备了陶瓷膜。采用扫描电镜、X射线衍射、交流阻抗谱等方法分析了微弧氧化膜在0.1 mol/L Cu SO4溶液中的腐蚀形貌、腐蚀产物组成及腐蚀行为;采用极化曲线分析了Cu2+对Cl-腐蚀的影响。结果表明:因为微弧氧化膜中的Mg O与溶液中的H+发生反应,促进了溶液中Cu2+的水解,生成更多Cu(OH)2,并吸附于膜层表面,从而阻止了腐蚀介质向膜基面的进一步扩渗,减弱了腐蚀介质对膜层的腐蚀作用;腐蚀介质Na Cl溶液中加入Cu SO4后,未加剧微弧氧化膜的破坏,反而产生了缓蚀效果。 相似文献
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锡青铜中主要元素为Cu、Sn、Zn、Pb。2004年前,在我单位(沈阳北车西屋轨道制动机技术有限公司)化验室化学分析条件下,对锡青铜中的锡含量的测定中使用的是传统的有剧毒的分析方法。此方法是将试样用HCL—H2O2溶解。锡呈四价状态,在接触剂氯化汞存在下,隔绝空气,用次亚磷酸钠将其还原为二价,在盐酸介质中,以淀粉为指示剂,用碘酸钾标准溶液滴定。分析过程繁锁,分析时间长,在分析锡青铜时使用有毒试剂:氯化汞溶液5%,如不慎接触会对人体产生毒害。原来分别采用测试的方法,操作复杂繁琐。自2005年已采用锡青铜无剧毒分析方法,可溶样一次,联测出锡青铜中锡、锌、铅、铜的含量,还可避免毒害试剂的使用,以达到快速安全的检测手段。 相似文献
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钙钛矿/钨青铜两相复合BSTN陶瓷的形成与性能研究 总被引:4,自引:0,他引:4
设计了特殊配方0.7BaO.0.3SrO·(1-y)TiO2·yNb2O5, 通过过量组成控制,制备了钙钛矿相和钨青铜相共存的复相陶瓷.用XRD和阻抗仪测试了相结构及介电常数.结果表明,在形成以钙钛矿为主相的体系中,Nb2O5过量6mol%以上时开始形成钨青铜相;在形成以钨青铜为主相的体系中,BaO和SrO过量11mol%以上时开始形成钙钛矿相.两相含量相当的体系中,钙钛矿相几乎不固溶Nb2O5,而钨青铜相固溶一定量TiO2.复相陶瓷的介电性能具有BST和SBN两相的特点.BSTN复相体系中钨青铜相的铁电/顺电转变温度随固溶TiO2量增加而降低,随钙钛矿相增加而升高,其最低转变温度约在200℃,比纯SBN相下降90℃. 相似文献
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为改善焦磷酸盐电镀Cu-Sn合金层的耐蚀性能差、镀速慢、结合力差等问题,用失重试验、形貌成分分析及电化学技术等方法,研究了阳极中Sn含量对焦磷酸盐电镀Cu-Sn合金层的沉积速率、腐蚀速率、腐蚀过程和微观形貌等的影响。结果表明:当阳极中Sn含量(质量分数)为25%时,Cu-Sn合金镀层的沉积速率较大[6.32mg/(cm2·h)],镀层中Sn含量为5.80%,属于低锡青铜,镀层耐蚀性好,在5%H2SO4溶液中的失重腐蚀速率最小,为0.011 8 mg/(cm2·h),腐蚀电流密度较小(84.7μA/cm2),腐蚀电位最正(-0.405 V),腐蚀倾向最小;CuSn合金镀层的包状物颗粒大小均匀、排列紧密、无明显的表面缺陷,镀层与基体结合良好。 相似文献
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采用共沉淀法制备Ti1-x Snx O2复合氧化物,浸渍负载质量分数10%的CuOx和FeOy活性组分,制备一系列Cum-Fen/Ti1-x Snx O2催化剂.探究不同Ti/Sn和Cu/Fe(物质的量比)对Cum-Fen/Ti1-x Snx O2催化剂的NH3-SCR反应活性的影响.研究结果表明,Ti0.67 Sn0.33 O2载体可促进活性组分CuOx和FeOy的相互作用.当Cu/Fe为3:1时,在300℃ 下NOx的转化率达到91.3%;向反应体系通入286 mg/m3 SO2反应3 h后,NOx的转化率仅下降2.6%.X射线光电子能谱(XPS)、程序升温还原(H2-TPR)、程序升温脱附(NH3-TPD和NOx-TPD)的表征表明,CuOx和FeOy之间存在相互作用,与单一的Cu/Ti0.67 Sn0.33 O2和Fe/Ti0.67 Sn0.33 O2对比,复合催化剂表面吸附氧浓度相对增加15% ~33%,总酸量增大56%,从而提高了催化剂脱硝活性. 相似文献
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Edward Moore 《International journal for numerical methods in engineering》1974,8(2):271-276
The fitting of a function y =\documentclass{article}\pagestyle{empty}\begin{document}$ \sum\nolimits_{i = 1}^n {A_i {\rm{e}}^{\lambda ix}} $\end{document} to experimental data is considered. Integral equations are developed which have the functions \documentclass{article}\pagestyle{empty}\begin{document}$ \sum\nolimits_{i = 1}^n {A_i {\rm{e}}^{\lambda ix}} $\end{document} as their solutions for n = 1, 2, 3, These integral equations are used to find the frequencies λi. Examples are worked out to illustrate the method. The method is shown to be capable of extension to other functions. 相似文献
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Ashis Bhattacharjee Debasis Roy Madhusudan Roy 《International Journal of Thermophysics》2012,33(12):2351-2365
Thermal decomposition of oxalate-based molecular precursors, namely ${\{{\rm N}(n{-} {\rm C}_{4} {\rm H}_{9})_{4}[{\rm Zn}^{\rm II}{\rm Fe}^{\rm III}({\rm C}_{2} {\rm O}_{4})_{3}]\}_{\infty}, \{{\rm N}(n{-}{\rm C}_{4}{\rm H}_{9})_{4}[{\rm Co}^{\rm II}{\rm Fe}^{\rm III}({\rm C}_{2}{\rm O}_{4})_{3}]\}_{\infty}}$ , and ${\{{\rm N}(n{-}{\rm C}_{4} {\rm H}_{9})_{4}[{\rm Fe}^{\rm II}{\rm Fe}^{\rm III}({\rm C}_{2}{\rm O}_{4})_{3}]\}_{\infty}}$ , abbreviated as BuZnFe, BuCoFe, and BuFeFe, respectively, are studied using thermogravimetry (TG) in the temperature range from ~300?K to ~675?K at multiple heating rates. This study also deals with how the thermal decomposition of the complexes proceed stepwise through a series of intermediate reactions. The effect of the divalent metal MII on the nature of thermal decomposition of the complexes, reflected in their TG profiles in terms of number of steps involved, is reported in this study. The temperature range of thermal decomposition steps for BuZnFe, BuCoFe, and BuFeFe with the same heating rates are studied systematically. Two different isoconversional methods, namely an improved iterative method and a model-free method are employed to calculate the kinetic parameters, and thus the most probable reaction mechanism of thermal decomposition is determined. Based on kinetic parameters, the important thermodynamic parameters such as the changes of entropy, enthalpy, and Gibbs free energy are estimated for the activated complex formation from the precursors. Considering the mass loss during the different thermal decomposition steps of BuZnFe, BuCoFe, and BuFeFe, observed in the thermogravimetry profiles, the overall reactions of the thermal decompositions are demonstrated. 相似文献
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D. Yagodin G. Sivkov S. Volodin P. Popel A. Mozgovoj 《Journal of Materials Science》2005,40(9-10):2259-2261
Measurements of temperature dependences of density d and ultrasound velocity V s of the eutectic Bi-44.6 wt.% Pb alloy were performed from eutectic temperature up to 550–900°C. Density was studied using gamma absorption method. Ultrasound velocity was determined by pulse phase method. The dependences V s(T) and d(T) are linear in temperature interval of measurements and can be approximated by the equations: $$\displaylines{ V_{\rm s} (T) = 1788 - 0.269\;(T - 398)\ {\rm m} \cdot {\rm s}^{ - 1}.\cr d(T) = 10271 - 1.29\;(T - 398)\ {\rm kg} \cdot {\rm m}^{- 3} .\cr} $$ These results are found to be in good agreement with data of other works. 相似文献
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D. Dengel W. Bergmann K.-H. Eschermann 《Materialwissenschaft und Werkstofftechnik》1981,12(7):235-243
Estimation of the Endurance and the Fatigue Limit of Steel by Measuring Specimens′ Temperatures. Microplastic deformation processes are pre-requisites for fatigue crack formation within metallic materials. If the testing frequency of a specimen, cyclically stressed by a progressively-increasing load test, is not too low it is no great metrological problem to ascertain that special stress amplitude, σf,th (f ? fatigue limit, th ? thermometrical), at which specimen's temperature begins to rise due to the start of ‘remarkable’ microplastic deformations. Investigations of this kind, recently carried out by rotating bending showed a very good correspondence between σf,th and a statistically ascertained estimate of the fatigue limit, \documentclass{article}\pagestyle{empty}\begin{document}$ \hat \sigma _{({\rm P} \simeq {\rm 0}\%{\rm)}} $\end{document} (P ? Probability of fracture), derived from comparatively performed Wöhler-tests. The purpose of this paper is to investigate the relationship between σf,th and \documentclass{article}\pagestyle{empty}\begin{document}$ \hat \sigma _{({\rm P} \simeq {\rm 0}\%{\rm)}} $\end{document} for some carbon steels when cyclically stressed by push-pull and pulsating tensile loading, respectively. Both, unnotched and notched specimes were tested. Moreover, thermometrically monitored Wöhler-tests revealed that temperature measurements can provide a short-cut prediction of specimens′ lives. Above all it has to be mentioned that a reliable clue is gettable at a very early experimental stadium whether the cyclic stressed specimen will later become a ‘break’ or – normally much later – a ‘run-out’. 相似文献
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W. L. Wood 《International journal for numerical methods in engineering》1981,17(2):281-289
This paper shows that it is comparatively simple to analyse algorithms for the numerical integration of the Space discretized equations from structural dynamics when applied to \documentclass{article}\pagestyle{empty}\begin{document}$\ddot x + \mu \dot x\omega ^2 x = p{\rm e}^{ist} $\end{document}, instead of the usual \documentclass{article}\pagestyle{empty}\begin{document}$ \ddot x + \omega ^2 x = 0 $\end{document}, and suggests that this should be done in order to gain some insight into the effect with natural damping and/or a periodic forcing term. The method is illustrated on some three- and four-time-level schemes. 相似文献
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The interface structure of an Al2O3/Nb/Al2O3 sandwich produced by solid-state diffusion bonding was investigated in detail by various transmission electron microscopy (TEM) methods. The joint possessed at one interface a
,
, and on the other interface a
and
orientation relationship. At both interfaces, misfit dislocations formed to compensate the lattice mismatch as found by high-resolution transmission electron microscopy (HRTEM). Electron energy-loss near edge structure (ELNES) studies revealed that the interface is terminating with an Al layer resulting in Al–Nb bonds. Identical sandwiches were investigated on the meso- and macroscopic scale by performing compression tests and simultaneously monitoring the strain development at (001)Nb and crystal faces. The full-field optical strain measurements (FFOM) revealed that the strain is localized at the interfaces when observed at the (001)Nb face while it is along the maximum shear directions of 36–54° inclined to the interface when observed at the face. The strain localization along a specific maximum shear direction results in the cleavage of Al2O3, always initiating from the interface possessing the
and
orientation relationship. 相似文献
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Wenbin Yang Litong Zhang Laifei Cheng Yongsheng Liu Laifei Cheng Weihua Zhang 《Applied Composite Materials》2009,16(2):83-92
A two-layered self healing coating with a B4C internal layer and a SiC external layer is prepared on C/SiC composite by chemical vapor deposition (CVD). Microstructure
and component of the coating was analyzed by SEM, EDS, and XRD. Oxidation behavior of SiC-B4C coated C/SiC composite was compared with SiC-SiC coated C/SiC in an environment of at 700°C, 1,000°C and 1,200°C for 100 h, respectively. It is demonstrated that the SiC-B4C coating is more efficient to protect the composite from oxidation than SiC-SiC coating below 1,000°C due to the self healing
behavior. After oxidized at 700°C for 100 h, the residual flexural strength of SiC-B4C coated C/SiC is about 86%, and that of SiC-SiC coated is about 64%. While after oxidized at 1,200°C, the former is about
86% and the later is about 89%. This is due to the enhanced evaporation of B2O3 at higher temperature. 相似文献
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Light-weight, cellular β-SiAlON/SiC ceramics were produced via dip-coating of an Al/Si-powder containing preceramic polymer
slurry into corrugated cardboard. The coated cardboard preforms were pyrolyzed in Ar-atmosphere at 1200°C, where the cellulose
fibres decomposed into carbon. Simultaneously the Al/Si melt infiltrated into the porous carbon and formed β-SiC. Subsequent
nitridation at temperatures between 1200–1530°C resulted in the formation of a β-SiC-containing
composite. Different pre-oxidation treatment resulted in a variation of the oxygen content in the solid solution phase (z = 0.6–1.2). 相似文献
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Copper diphosphates (Cu2P2O7 · 5H2O, Cu1.6K0.8P2O7 · 1.7H2O, and Cu1.5K1.0P2O7 · 2.8H2O) were made by mixing aqueous solutions of tetrapotassium diphosphate and copper dichloride. When the diphosphates were heated, the decomposition of the diphosphates to orthophosphate was observed at a temperature lower than 150° C. The orthophosphate was polymerized by condensation to polyphosphates in the temperature range of about 150 to 450° C. The polyphosphates reorganized to diphosphate at 450 to 550° C according to the following reaction:
相似文献
20.
Peng Zhu Linfei Liu Shengping Zhu Guina Xiao Ying Wang Da Xu Yijie Li 《Journal of Superconductivity and Novel Magnetism》2012,25(6):1641-1645
$\mathrm{GaBa}_{2}\mathrm{Cu}_{3}\mathrm{O}_{7\mbox{-}\delta}$ thin films have been grown on CeO2 cap layer by RF magnetic sputtering with different oxygen/argon partial pressure ratio from 2:1 to 1:5. The CeO2 cap layers were fabricated by pulse laser deposition (PLD) on YSZ/CeO2/Ni-5%W alloy substrate and had good properties in structure and surface morphology. We study the relationship between oxygen/argon ratio and the performance of the $\mathrm{GaBa}_{2}\mathrm{Cu}_{3}\mathrm{O}_{7\mbox{-}\delta}$ film in order to find out the optimized deposition condition. The structure and surface morphology of the $\mathrm{GaBa}_{2}\mathrm{Cu}_{3}\mathrm{O}_{7\mbox{-}\delta}$ thin films were measured by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), Atomic force microscopy (AFM). It was found that the texture and surface performance of $\mathrm{GaBa}_{2}\mathrm{Cu}_{3}\mathrm{O}_{7\mbox{-}\delta}$ film, such as growth orientation, grain roughness, grain size and surface morphology, are deeply affected by the oxygen/argon ratio. And the film??s performance was the best when the oxygen/argon partial pressure ratio is 1:1. 相似文献
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