铝合金2024上钒酸盐转化膜的研究

利用浸渍法在铝合金表面获得钒酸盐转化膜,应用交流阻抗技术(EIS)研究了NaVO3浓度及浸泡时间对铝合金2024表面钒酸盐转化膜成膜过程的影响,扫描电子显微镜(SEM)与能量散射能谱(EDS)分析膜表面形貌与成分.结果表明,EIS显示当转化液中NaVO3的浓度为0.1 M时处理3 min得到的转化膜的阻抗值最大,达到7.17×105Ω.cm2;SEM显示在该溶液浓度下表面所形成的转化膜均匀致密,其成分主要由Al,V,Mg元素组成.钒酸盐转化膜工艺简单,对环境无污染,膜的耐蚀性强,具有一定的应用前景.     

H2O2对钢表面稀土转化膜成膜的影响

应用交流阻抗技术(EIS)研究了H2O2浓度对特种钢表面稀土Ce转化膜成膜过程的影响、扫描电子显微镜(SEM)与能量散射能谱(EDS)分析膜表面形貌与成分.结果表明,EIS显示了在不同H2O2浓度转化液中成膜的动态过程,当H2O2的浓度相对0.012 M的Ce(NO3)3·6H2O达到一个优化浓度时(本实验为0.012 M)形成膜速度最快且最终膜的稳定阻抗值最大,达到2.1×105 Ω/·cm2;SEM显示在该溶液浓度下表面所形成的转化膜均匀致密,其成分主要由Ce、O、Fe元素组成.     

一种多颜色锆基转化膜在冷轧板上的耐腐蚀性

常温下经过不同时间的锆化处理,在冷轧板(CRS)表面制得一层淡黄色、金黄色和蓝紫色等不同颜色的转化膜。采用扫描电镜和能谱研究不同颜色转化膜的形貌和元素组成,转化膜主要由C、O、Fe、Zr和F等元素组成。通过电化学阻抗谱(EIS)研究不同颜色转化膜的电化学性能,通过百格试验和中性盐雾试验(NSS)检测粉末涂装后漆膜的附着力和耐腐蚀能力;结果显示,银白色裸板,淡黄色、金黄色、蓝紫色转化膜均具有一定的耐腐蚀能力,不同颜色转化膜可以显著提高冷轧板与粉末漆层的附着力和涂装之后冷轧板的抗腐蚀能力,其中金黄色转化膜表现出更加优异的耐腐蚀能力,其500h中性盐雾实验评级达到0级。     

AZ31镁合金在Hank’s仿生溶液中的电化学腐蚀行为研究

为研究镁合金在人体生理环境下的腐蚀行为,采用阳极极化和电化学交流阻抗谱(EIS)测量技术研究了AZ31镁合金在Hank’s仿生溶液中的电化学腐蚀行为及腐蚀产物形成过程;利用扫描电子显微镜(SEM)和X射线能谱仪(EDS)分析不同浸泡时间腐蚀产物膜的形貌和成分变化。研究结果表明:镁合金AZ31在Hank’s溶液中浸泡最初10min,表面形成新的MgO钝化膜。镁合金的腐蚀经历了点蚀的诱导、点蚀的发展和腐蚀产物层的生成3个阶段,腐蚀过程中除Mg的溶解过程外,还有H2PO-4、HPO2-4、PO3-4、Ca2+在镁合金表面的吸脱附过程。镁合金点蚀处磷酸钙盐沉积较多,表明镁离子的溶解促进了磷酸钙的沉积。     

环氧涂层/镀锌板电极系统腐蚀电化学行为

利用EIS研究环氧型有机涂层的腐蚀电化学行为。在浸泡初期阻抗谱是一个时间常数的单容抗弧,阻抗值基本不变,此时漆膜能够阻止介质渗入。在浸泡中期阻抗值随时间逐渐增大,原因为镀锌钢板表面预处理层的铬酸盐自修复作用以及铬酸盐转化膜溶解物和腐蚀产物沉积堵塞漆膜微孔隙,阻止介质渗入到达镀锌钢板表面,导致阻抗值变大。后期,预处理膜完全溶解破坏,金属基体腐蚀反应加快,阻抗值变小.     

微弧氧化对铝合金搅拌摩擦焊缝耐蚀性能的影响

为了提高搅拌摩擦焊(FSW)焊缝的耐腐蚀性能,本文采用微弧氧化技术在6082系铝合金FSW焊缝表面制备了不同电流密度下的微弧氧化陶瓷膜层,使用X射线衍射仪(XRD)和扫描电镜(SEM)对膜层进行相组成确定并观察其表面形貌,使用激光共聚焦扫描电子显微镜(CLSM)测定膜层表面粗糙度。通过电化学阻抗谱(EIS)及极化曲线(LSV)分析比较微弧氧化前、后铝合金FSW焊缝的耐腐蚀性能。结果表明:随着电流密度的增加,膜层越来越厚,击穿越来越困难。陶瓷层一旦被击穿,会形成很多的熔融物,使陶瓷层表面凹凸不平,表面粗糙度增加。此外,当电流密度为10A/dm2时,陶瓷膜层表现出较佳的耐蚀性能。     

处理工艺对纯镁表面植酸转化膜性能的影响

文章采用植酸水溶液对纯镁进行化学转化处理,通过SEM、EDS、电化学极化曲线法研究了温度、时间、浓度以及pH值对表面转化膜性能的影响.结果表明,转化膜的厚度和表面裂纹尺寸随着转化处理液浓度及处理时间的增加而增大,但时间过长或浓度过大均会导致转化膜的耐蚀性下降;溶液pH从1增大到5时,转化膜的裂纹尺寸呈现减小趋势,耐蚀性先增大后减小;转化膜表面裂纹尺寸随温度升高先增大后减小,温度在20℃～60℃之间,形成的转化膜耐蚀性较好,80℃和90℃时,形成的转化膜耐蚀性显著降低.     

纳米晶304不锈钢高温氧化膜中氧元素的XPS研究

利用X-射线光电子谱(XPS)研究普通304不锈钢(CP-SS304)和用深度轧制技术制备块体的纳米晶304不锈钢(BN-SS304)在900℃空气中氧化24h形成氧化膜中氧元素的结合能和原子百分比.BN-SS304和CP-SS304氧化膜表面氧元素以分子态(O0)和离子态(O2-)存在;BN-SS304和CP-SS304氧化膜中O0和O2-的结合能相同;Ar+溅射400s时不存在分子氧,而CP-SS304氧化膜溅射800s时不存在分子氧;从溅射开始至溅射800s,BN-SS304氧化膜中O2-与(O2-+O0)原子数的比值大于CP-SS304,最大差距为8.92％.结果表明,BN-SS304氧化膜表面吸附O2深度较低;BN-SS304氧化膜致密性更好.     

NMMO法制备丝瓜络再生纤维膜

采用NMMO工艺制取丝瓜络纤维素膜,并对纤维素膜进行表征。利用扫描电子显微镜(SEM)、红外光谱分析仪(FTIR)、X射线衍射仪(XRD)、热力学分析仪(TG)对丝瓜络纤维膜进行表征。SEM结果显示丝瓜络纤维素膜的厚度非常薄,并且膜的表面非常致密;FTIR光谱图显示丝瓜络纤维素膜的特征峰的形状与丝瓜络纤维的特征峰相似,显示出纤维素特征;XRD曲线图显示丝瓜络纤维素膜的纤维素结晶由纤维素Ⅰ变为纤维素Ⅱ;TG曲线图表明丝瓜络纤维素膜具有良好的热稳定性能,符合应用要求。     

Ce改性AZ91的微弧氧化膜制备及其耐蚀性能

利用交流恒压微弧氧化技术, 通过Ce改性镁合金基体制备高耐蚀微弧氧化膜. 在100、120和 140 V的外加电压下, 对3种试样: AZ91, 质量分数w(Ce) 分别为0.92%和1.80%改性的AZ91微弧氧化过程、微观结构和组成及氧化膜的耐蚀性能进行研究. 应用电子扫描显微镜(SEM), 电子能谱（EDS）和X射线衍射（XRD）等表征氧化膜的微观结构和化学组成. 利用稳态极化曲线和电化学阻抗谱（EIS）测试了氧化膜在质量分数w(NaCl)为3.5%的溶液中的腐蚀过程. 实验结果表明氧化膜成膜过程可以分为3个阶段; 氧化膜主要由MgO组成, 镁合金中的稀土元素Ce促进成膜过程, 增加膜层的致密性; 稀土改性后镁合金氧化膜的耐蚀性比镁合金基体提高4个数量级, 腐蚀电流密度低至10^-8 A/cm2．     

Corrosion resistance of cerium conversion film electrodeposited on Mg-Gd-Y-Zr magnesium alloy

The cerium conversion film was applied to improving the corrosion resistance of Mg-Gd-Y-Zr magnesium alloy. The film was electrodeposited on the surface of the Mg-RE alloy in cerium nitrate solution. The compositions and morphologies were analyzed by X-ray diffraction(XRD), scanning election microscopy (SEM). The corrosion behaviors of the film were investigated electrochemical impedance spectroscopy (EIS), potentiodynamic polarization tests and immersion tests. The results show that the optimum parameters for electrochemical deposition are as follows: pH 10.0, time 30 min, 50 mmol/L Na₂CO₃ and temperature 25 °C by the designed experiments according to the orthogonal table L(9, 3⁴). The corrosion protection efficiency is dependent on the deposition parameters. The cerium conversion film shows better corrosion protection behavior than chromate conversion film on Mg-Gd-Y-Zr magnesium alloy. Foundation item: Project (5133001E) supported by the Major State Basic Research and Development Program of China     

Electrochemical characterization of ion selectivity in electrodeposited nickel hexacyanoferrate thin films

The ion selectivity of electrodeposited nickel hexacyanoferrate （NiHCF） thin films was investigated using electrochemical impedance spectroscopy （EIS） and cyclic voltammetry （CV）. NiHCF thin films were prepared by cathodic deposition on Pt and Al substrates. EIS and CV curves were determined in 1 mol/L （KNO3＋C5NO3） and 1 mol/L （NaNO3＋CsNO3） mixture solutions, which were sensitive to the concentration of Cs^＋ in the electrolytes. Experimental results show that all Nyquist impedance plots show depressed semicircles in the high-frequency range changing over into straight lines at lower frequencies. With increasing amounts of Cs^＋, the redox potentials in CV curves shift toward more positive values and the redox peaks broaden; the semicircle radius in corresponding EIS curves and the charge transfer resistance also increase. EIS combining CV is able to provide valuable insights into the ion selectivity of NiHCF thin films. 2008 University of Science and Technology Beijing. All rights reserved.     

AD5933在肉类阻抗谱测量系统中的应用

为了能够对注水肉的检测提供科学的判断依据,提出了一种基于AD5933的肉类阻抗谱测量方法．该方法利用专用芯片AD5933测量阻抗谱信息,在特定的激励频率下,使用两个针状电极检测受检肉的电信号．每个频率采样3组数据,采用滑动平均算法滤除波动得到最终的阻抗值．研究结果表明,对于1-100kHz的激励频率,可以测量100fΩ-10kΩ之间的复阻抗,测量精度为0．5％,可以用于肉类阻抗谱的测量．     

酸雨作用下酸性土壤酸化过程中铜的腐蚀行为

利用极化曲线技术,电化学阻抗测试技术(EIS),扫描电镜(SEM),X射线衍射(XRD)等方法,研究模拟酸雨作用下酸性土壤酸化过程中铜的腐蚀行为.实验结果表明,模拟酸雨加速了铜在酸性土壤中的腐蚀.随着淋入的模拟酸雨酸性增加,铜的腐蚀速率增加.随着腐蚀的进行,铜在淋溶酸雨的土壤中腐蚀速率增加,而在淋溶蒸馏水对比液的土壤中腐蚀速率有所减小.腐蚀初期,铜的阻抗谱为偏心半圆容抗弧;腐蚀后期,当淋溶液为模拟酸雨时,土壤中铜的阻抗谱表现为双容抗弧,铜的腐蚀受电荷传递过程控制,当淋溶液为蒸馏水对比液时,铜的阻抗谱表现为高频的容抗和低频的Warburg阻抗,铜的腐蚀受扩散过程控制.铜表面的腐蚀产物主要为Cu_2O和CuO等Cu的氧化物,同时还夹杂有SiO_2等土壤成分.     

锌对Li（Ni_（1/3）Co_（1/3）Mn_（1/3））O_2电极首次脱锂过程电化学性能的影响

共沉积法制备不同含锌量的锂离子电池正极材料Li（Ni1/3Co1/3Mn1/3）O2.采用交流阻抗谱分析该正极材料在首次脱锂过程中的电化学特性以及锌对电极阻抗和锂离子扩散系数的影响.电极阻抗图谱分析结果表明：3.7～4.4V为电极发生电化学反应的电位区间;锌减小了电极材料的SEI膜阻抗和电荷转移阻抗;少量固溶锌提高了锂离子在材料固相中的扩散能力.     

Interpretation of electrochemical impedance spectroscopy(EIS) circuit model for soils

Based on three different kinds of conductive paths in microstructure of soil and theory of electrochemical impedance spectroscopy(EIS), an integrated equivalent circuit model and impedance formula for soils were proposed, which contain 6 meaningful resistance and reactance parameters. Considering the conductive properties of soils and dispersion effects, mathematical equations for impedance under various circuit models were deduced and studied. The mathematical expression presents two semicircles for theoretical EIS Nyquist spectrum, in which the center of one semicircle is degraded to simply the equivalent model. Based on the measured parameters of EIS Nyquist spectrum, meaningful soil parameters can easily be determined. Additionally, EIS was used to investigate the soil properties with different water contents along with the mathematical relationships and mechanism between the physical parameters and water content. Magnitude of the impedance decreases with the increase of testing frequency and water content for Bode graphs. The proposed model would help us to better understand the soil microstructure and properties and offer more reasonable explanations for EIS spectra.     

A portable single-cell analysis system integrating hydrodynamic trapping with broadband impedance spectroscopy

In this paper, we present a portable single-cell analysis system with the hydrodynamic cell trapping and the broadband electrical impedance spectroscopy(EIS). Using the least flow resistance path principle, the hydrodynamic cell trapping in serpentine arrays can be carried out in a deterministic and automatic manner without the assistance of any external fields. The experimental results show that a cell trap rate of higher than 95% can be easily achieved in our cell trapping microdevices. Using the maximum length sequences(MLS) technique, our home-made EIS is capable of measuring the impedance spectrum ranging from 1.953 kHz to 1 MHz in approximately 0.5 ms. Finally, on the basis of the developed single-cell analysis system, we precisely monitor the trapping process of human breast tumor cells(MCF-7 cells) according to the changes of electrical impedance. The MCF-7 cells with different trapping conditions or sizes can also be clearly distinguished through the impedance signals. Our portable single-cell analysis system may provide a promising tool to monitor single cells for long periods of time or to discriminate cell types.     

Effect of electropolishing on electrochemical behaviours of titanium alloy Ti-10V-2Fe-3Al

The electrochemical behaviours of titanium alloy Ti-10V-2Fe-3Al after electropolishing in a self-developed electrolyte in comparison with conventional grinding were studied by electrochemical impedance spectroscopy (EIS).Optical microscopy (OM),scanning electron microscopy (SEM),atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to evaluate the surface characteristics of the alloy.It was found from the EIS experiments that the polarization resistance (Rp) was increased,the double layer capacitance (Qc) was decreased and the electrochemical impedance of the alloy was enhanced by electropolishing.The electropolished surface was flat,smooth and bright and its roughness was 3.310 nm.To underline the advantage of electropolishing process against grinding to provide the anodic oxidation process with a higher quality substrate,the ground and electropolished titanium alloys were anodized in parallel under the same conditions.The corrosion behaviours of the two kinds of anodized titanium alloys were compared.It was revealed that electropolishing generated a high quality substrate and improved the corrosion resistance of anodic oxide film formed on titanium alloy Ti-10V-2Fe-3Al.Furthermore,the mechanism of electropolishing improving the corrosion resistance of the anodic oxide film was proposed.