A study on corrosion resistance characteristics of PVD Cr-N coated steels by electrochemical method

The corrosion behavior of Cr-N coated steels with different phases (-Cr, CrN and Cr₂N) deposited by cathodic arc deposition on AISI H13 steel was investigated in a 3.5% NaCl solution at ambient temperature. Potentiodynamic polarization tests, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were the techniques applied to characterize the corrosion behavior. It was found that the CrN coating had a lower current density from potentiodynamic polarization tests than others. The porosity, corresponding to the ratio of the polarization resistance of the uncoated and the coated substrate, was higher in the Cr₂N coating than in the other Cr-N coated steels. EIS measurements showed, for most of the Cr-N coated steels, that the Bode plot presented two time constants. Also, the Cr₂N coating represented the characteristic of Warburg behavior after 72 h of immersion. The coating morphologies were examined in planar view and cross-section by SEM analysis and the results were compared with those of the electrochemical measurement. The CrN coating had a dense, columnar grain-sized microstructure with minor intergranular porosity. From the above results, it is concluded that the CrN coating provided a better corrosion protection than the other Cr-N coated steels.     

纳米复合涂层对碳钢防腐性能的交流阻抗评定

利用电化学阻抗谱法考察了普通涂层、纳米复合涂层 和憎水纳米复合涂层的防腐性能.结果表明，纳米复合涂层的防腐性能明显高于普通涂层， 而经过氟表面活性剂改性的表面憎水的纳米复合涂层的防腐性能更好.     

电化学方法探讨三聚磷酸钛及磁性氧化铁在有机涂层中的缓蚀机制

本文利用电化学方法研究了在油漆涂层中添加三聚磷酸钛和磁性氧化铁对金属防护性能的影响。结果表明,三聚磷酸钛作为活性防锈颜料,添加在涂层中能够极大地改善涂层的防护性能,磁性氧化铁亦不失为一种较好的防锈颜料,但性能不及三聚磷酸钛。同时亦探讨了这两种颜料的可能防锈机理。     

GaAs／AlAs DBR的GSMBE优化生长及表征

采用气态源分子束外延（GSMBE）技术优化生长了GaAs／AlAs分布布拉格反射镜（DBR）材料，并用X射线衍射（XRD）及反射光谱对其生长质量进行了表征。结果表明，采用5S间断生长的GaAs／AlAs DBR材料质量和界面质量优于无间断生长，并且10对GaAs／AlAs DBR的质量优于30对，说明DBR对数越多，周期厚度波动越大，材料质量越差。优化生长得到的30对GaAs／AlAsDBR的反射率大于99％，中心波长为1316nm，与理论设计结构的模拟结果基本一致，可用作1．3μm垂直腔面发射激光器（VVSEL）直接键合的反射腔镜。     

低频脉冲电流退火对CoFeSiB非晶薄带巨磁阻抗效应的影响

研究了经不同低频脉冲电流密度退火的Co66.3Fe3．7Si12B18非晶薄带的巨磁阻抗（GMI）效应。结果表明，在低频脉冲电流下，巨磁阻抗效应的大小与退火电流密度密切相关。非晶带的GMI变化率△Z／Z先随退火电流密度的增加而增强，当电流密度为104A／mm^2时，△Z／Z达到最大值53．8％，此后随电流密度增大，GMI变化率开始减小。对脉冲电流退火影响巨磁阻抗效应的机制作了定性分析。并分析了由脉冲电流退火在材料内感生的横向各向异性场凤对GMI效应的影响，发现HK有利于提高GMI效应的峰值，但同时存在一个临界值，当超过这个值时，GMI效应的峰值减弱。     

机器人的阻抗控制

阻抗控制在机器人的力的控制中具有重要地位,文章对阻抗控制方法中的参数的意义进行了说明,总结并分析对比了阻抗控制和其它力控方法的特点,对基于动力学模型和基于位置的两种主要的阻抗控制方法进行了分析,列出了阻抗控制参数的选取方法.     

稀土对A572 Gr.65钢电化学腐蚀行为的影响

目的提高A572 Gr.65钢的耐蚀性能。方法通过向A572 Gr.65钢中添加La和Ce的混合稀土,得到不同稀土含量的A572 Gr.65钢。以3.5%NaCl溶液为腐蚀介质,借助电化学工作站、XRD和SEM等手段分析表征了不同稀土含量的A572 Gr.65钢的电化学腐蚀行为。结果稀土能使A572 Gr.65钢腐蚀电位正移,腐蚀电流减小。当稀土质量分数为0.0047%时,腐蚀电位最正,为-0.50V,腐蚀电流密度最小,为2.77×10-6 A/cm2,极化曲线的阳极部分存在明显的活化-钝化过渡区,有明显的钝化过程。不同稀土含量的A572Gr.65钢的阻抗谱均由单一的容抗弧组成,容抗弧半径代表着对电荷传输的阻碍能力,稀土质量分数为0.0047%时,容抗弧半径最大,对电荷传输的阻碍能力最大。稀土可以使钢中的夹杂物变性,使夹杂物由Ca S和Al2O3-Ca O变为稀土的氧硫化物,夹杂物尺寸由5μm变为2μm,减小腐蚀发生的活性区。此外,稀土离子可以提高阴极极化率,使腐蚀产物中不稳定的γ-Fe OOH含量减少,增强锈层的稳定性、致密性和附着能力,增大电荷转移的阻力,有效阻碍侵蚀性Cl-的侵入。结论稀土的添加能有效提高A572Gr.65钢的耐蚀性,稀土质量分数为0.0047%时,试验钢的耐蚀性最好。腐蚀过程中,由点蚀逐渐转变为均匀腐蚀,活性点的形成和阳极溶解速度为整个腐蚀过程中的限制性环节。     

Exploring thermal spray gray alumina coating pore network architecture by combining stereological protocols and impedance electrochemical spectroscopy

Complex multiscale pore network architecture characterized by multimodal pore size distribution and connectivity develops during the manufacture of ceramic thermal spray coatings from intra- and interlamellar cracks generated when each lamella spreads and solidifies to globular pores resulting from lamella stacking defects. This network significantly affects the coating properties and their in-service behaviors. De Hoff stereological analysis permits quantification of the three-dimensional (3D) distribution of spheroids (i.e., pores) from the determination of their two-dimensional (2D) distribution estimated by image analysis when analyzing the coating structure from a polished plane. Electrochemical impedance spectroscopy electrochemically examines a material surface by frequency variable current and potential and analyzes the complex impedance. When a coating covers the material surface, the electrolyte percolates through the more or less connected pore network to locally passivate the substrate. The resistive and capacitive characteristics of the equivalent electrical circuit will depend upon the connected pore network architecture. Both protocols were implemented to quantify thermal spray coating structures. Al₂O₃-13TiO₂ coatings were atmospherically plasma sprayed using several sets of power parameters, are current intensity, plasma gas total flow rate, and plasma gas composition in order to determine their effects on pore network architecture. Particle characteristics upon impact, especially their related dimensionless numbers, such as Reynolds, Weber, and Sommerfeld criteria, were also determined. Analyses permitted identification of (a) the major effects of power parameters upon pore architecture and (b) the related formation mechanisms. This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials Park, OH, 2006.     

退火条件对FeCuNbSiB非晶带材应力阻抗效应的影响

研究了退火条件对非晶FeCuNbSiB带材应力阻抗性能的影响。结果表明,当退火温度为300℃时,FeCuNbSiB非晶带材开始慢慢晶化,当温度上升到500℃时,带材内部结构已由非晶态完全转变成晶态。当退火温度低于300℃时,退火能够消除部分应力,使阻抗变化的灵敏度提高;但当退火温度高于300℃时,随着退火温度的升高,应力阻抗效应减弱。退火时间超过1h,延长退火时间,对带材的应力阻抗性能影响不大。非晶FeCuNbSiB带材经100℃×2h的退火处理后,应力为2.7MPa时,应力阻抗变化可达26%。     

铝阳极氧化膜在NaCl溶液中的电化学性能

采用交流阻抗法研究了工业纯铝L3阳极氧化膜在中性NaCl溶液中交流阻抗谱的变化规律, 比较了未封闭处理与沸水封闭处理后氧化膜的交流阻抗谱的差异, 并结合等效电路分析了氧化膜多孔层与阻挡层电化学参数的变化.结果表明, 未封闭的阳极氧化膜在NaCl溶液中浸泡初期存在一个自封闭过程, 封闭处理明显提高氧化膜多孔层的初始Rp值并降低初始CPEp值; 溶液中侵蚀性离子浓度越高, 封闭处理提高铝阳极氧化膜的耐蚀性能作用越明显.