Influence of Dissolved Oxygen on the Protectiveness and Morphological Characteristics of Calcareous Deposits with Galvanostatic Polarization

The influence of dissolved oxygen on calcareous deposits formed under galvanostatic polarization mode was studied.When the dissolved oxygen concentration was less than 7 mg L^(-1),the cathodic protection potential showed a plateau at the initial polarization,and then quickly shifted negatively.While the dissolved oxygen was more than 9 mg L^(-1),the potential shifted negatively in a linear form.After 168 h of polarization,the final protection potential shifted negatively with the decreasing dissolved oxygen concentration.The deposition progress was monitored by electrochemical impedance spectroscopy,and only one single loop was found in Nyquist diagram,indicating deposits of ineffective protectiveness precipitation under the experimental conditions.The protection factor of deposits increased with the decreasing dissolved oxygen concentration which was detected by linear polarization resistance technique.The cathodic electrochemical reaction could change very shortly from oxygen reduction to hydrogen evolution after cathodic protection under very low dissolved oxygen concentration,such as 1 mg L^(-1),resulting in the hydrogen bubbling from the metallic surface and the decrease of deposits protection factor.Observation by scanning electron microscopy and X-ray diffraction analysis demonstrated that the deposits were mainly of calcite under the experimental conditions,and that dissolved oxygen had no effect on the crystalline types of calcium carbonate.

Glucose Oxidase/Polypyrrole Biosensor Fabricated by Galvanostatic Electropolymerization Accompanied with a Potential Jumping

A galvanostatic glucose oxidase (GOD_x)/polypyrrole (Ppy) biosensor fabricated through a potential jumping process was reported.In spite of the instantaneous voltage jumping from 0.95 V to 1.7 V versus Ag/AgCl in the galvanostatic polymerization of pyrrole with commercial GOD_x,this GOD_x enzyme still could be successfully bundled with polypyrrole (Ppy).And,the results also confirmed that this glucose sensor not only possessed of better sensitivity to glucose than that fabricated from potentiometry or mild voltage elevating galvanometry for the similar preparing conditions but also exhibited two-week long-term stability.Finally,the kinetic data of Michalis constant (K_m) and Maximum current (I_m) for the optimized sensor were derived.The discovery this electro-modification process may disclose a novel method for fabricating the other enzyme biosensors.

Potential Oscillations of a Stainless Steel Electrode during Galvanostatic Polarization in a Mixed Solution of Sulfuric and Chromic Acids

Potential oscillations of a stainless steel electrode galvanostatically anodized have been observed in amixture of chromic and sulfuric acids. The potential regularly oscillated between 1.6 V vs. SCE (lower) and 2.1V(upper) with a certain frequency. The potential values are affected neither by the composition of chromic and sulfu-ric acids nor by the magnitude of applied current density although the potential frequency is very sensitive to theseparameters. This phenomenon is interpreted in terms of the repeated formation and disappearance of the saturatedlayer of dichromate ions on the electrode surface. Such scheme is consistent with the in situ FTIR spectroscopicresult that the concentration of Cr2O ions on the electrode surface increased with time during the polarization atthe lower potential but the change in concenetion of Cr2O ions was negligible at the higher potential.

Galvanostatic anodic polarisation of WE43

The Mg corrosion mechanism was explored using galvanostatic polarisation curves,hydrogen evolution and weight loss.The data(a)were consistent with the existence of the uni-positive Mg+ion,(b)indicated that some hydrogen dissolved in the WE43 metal,and(c)indicated that self corrosion was more important than the applied current density in causing weight loss.

Effects of synthetic conditions of pulse galvanostatic method on electroactivity of polyaniline

Nano-fibrous polyaniline was synthesized on stainless steel electrode in 0.5mol·L-1 H2SO4 solution by pulse galvanostatic method. The effects of synthetic conditions of pulse galvanostatic method on the electroactivity of polyaniline were investigated. The results show that the electroactivity of polyaniline film strongly depends on the synthetic conditions, such as the ratio of “on time” to “off time”(ton/toff), frequency, monomer concentration, temperature and mean current density. Different electroactivities of polyaniline are caused by different morphologies of polyaniline. The nano-fibrous polyaniline has higher electroactivity than polyaniline with other morphologies. Under the following conditions: mean current density of pulse galvanostatic method 13mA·cm-2, ton/toff 1, frequency 200Hz, monomer concentration 0.3mol·L-1 and temperature 20℃, nano-fibrous polyaniline film with the highest electroactivity can be obtained.

Influence of Temperature on the Protectiveness and Morphological Characteristics of Calcareous Deposits Polarized by Galvanostatic Mode

The influence of temperature on calcareous deposits formed under galvanostatic polarization mode was studied. The deposition was monitored by electrochemical impedance spectrum, and a supplementary loop in Nyquist diagram at high frequency was found to be an indicator of deposits precipitation with sufficient protection at above 20 ~C. An exponential increase of protectiveness with temperature was observed, which was quantified by linear polarization resistance technique. Observation by scanning electron microscope and X-ray diffraction analyses demonstrated that the critical temperature of calcium carbonate crystal form transition ranged from 15 to 20 ℃. Calcite formed below 15 ℃, while aragonite precipitated at above 20 ℃.

A Galvanostatic Modeling for Preparation of Electrodeposited Nanocrystalline Coatings by Control of Current Density

The correlation between the grain size of electrodeposited coatings and the current densities was modeled by considering galvanostatic conditions. In order to test the model by experimental results, nanocrystalline （NC） nickel samples were deposited at different current densities using a Watts bath. The grain size of the deposits was evaluated by X-ray diffraction （XRD） technique. Model predictions were validated by finding a curve being the best-fit to the experimental results which were gathered from literature for different NC coatings in addition to those data measured in this research for NC nickel coatings. According to our model, the variation of grain size with the reciprocal of the current density follows a power law. A good agreement between the experimental results and model predictions was observed which indicated that the derived analytical model is applicable for producting the nanocrystalline electrodeposits with the desired grain size by controling current density.

Electrochemical codeposition of Mg-Li-Gd alloys from LiCl-KCl-MgCl_2-Gd_2O_3 melts

Mg-Li-Gd alloys were prepared by electrochemical codeposition from LiCl-KCl-MgCl 2 -Gd 2 O 3 melts on molybdenum electrode with constant current density at 823 and 973 K. The microstructure of the Mg-Li-Gd alloys was analyzed by X-ray diffraction （XRD）, optical microscopy （OM） and scanning electron microscopy （SEM）. The results show that magnesium and gadolinium deposit mainly in the first 30 min, and the alloy obtained contains 96.53% Mg, 0.27% Li and 3.20% Gd （mass fraction）. Then, the reduction of lithium ions occurs quickly. The composition of alloy can be adjusted by controlling electrolysis time or Gd 2 O 3 concentration in LiCl-KCl melts. With the addition of Gd into Mg-Li alloys, the corrosion resistance of the alloys is enhanced. XRD results suggest that Mg 3 Gd and Mg 2 Gd can be formed in Mg-Li-Gd alloys. The distribution of Gd element in Mg-Li-Gd alloys indicates that Gd element mainly distributes at the grain boundaries of Mg-Li-Gd alloys.

Influence of Ga and In on microstructure and electrochemical properties of Mg anodes

The influence of Ga and In on the electrochemical properties of Mg anode materials were investigated by the polarization and galvanostatic curve tests. The microstructure and the corroded surface of the Mg-In-Ga alloys were observed by scanning electron microscopy （SEM）. The corrosion product of the Mg-0.8%In （mass fraction） and Mg-0.8%Ga-0.3%In alloy were determined by X-ray diffraction. The results show that no second phase exists in the Mg-xIn （x=0-0.8%） allloys. Intergranular compounds containing Ga and In elements occur in the Mg-0.8%In-xGa （x=0-0.8%） alloys. The addition of In into Mg as well as the addition of 0.05%-0.5%Ga into Mg-In alloy promotes the corrosion resistance. The addition of Ga into Mg-In alloys also promotes the electrochemical activity. The Mg-0.8%In-0.8%Ga alloy has the most negative mean potential,-1.682 V, which is more negative than -1.406 V in AZ91D. The corrosion type of the Mg-In-Ga alloys is general corrosion and the corrosion product is Mg（OH）2.

Discharge behavior and electrochemical properties of Mg-Al-Sn alloy anode for seawater activated battery

Mg-Al-Sn alloy is one of the new developed anode materials for seawater activated batteries. The potentiodynamic polarization, galvanostatic discharge and electrochemical impedance spectroscopy of Mg-6%Al-1%Sn and Mg-6%Al-5%Sn(mass fraction) alloys in seawater were studied and compared with the commercial AZ31 and AP65 alloys. The results show that the Mg-6%Al-1%Sn alloy obtains the most negative discharge potential of average-1.611V with a electric current density of 100 mA/cm2. EIS studies reveal that the Mg-Al-Sn alloy/seawater interfacial electrochemical process is determined by an activation controlled reaction. The assembled prototype batteries with Mg-6%Al-1%Sn alloy as anodes and Ag Cl as cathodes exhibit a satisfactory integrated discharge properties.

Fabricating multifunctional polymeric nanofilm capable of resisting corrosion and activating copper surface by electrochemical and hydrolysis-condensation approach

A multifunctional polymeric nanofilm of triazinedithiolsilane monosodium salt, which can resist corrosion and activatecopper surface concurrently, was prepared by galvanostatic technique and the following hydrolysis-condensation approach.Electrochemical tests were carried out to evaluate the resistant ability of nanofilm. The changes of functional groups atop thenanofilms were monitored with Fourier transform infrared spectroscopy （FT-IR） and contact angles （CA） simultaneously. Thechemical composition and the morphology of the polymeric nanofilm were investigated by X-ray photoelectron spectroscopy （XPS）and scanning electron microscope （SEM）, respectively. The results reveal that the preferentially developed disulfide units protect thecopper during the whole preparation process, and the subsequently hydrolyzed nanofilms without/with heating shape into newinterface phases bearing the multifunctionality. This multifunctional interface （the polymeric nanofilm on copper surface） opens upthe possibilities for other OH-containing reagents to be anchored onto copper surface in demanding researches or industrialapplications.

脉冲电流法电解合成聚苯胺

在 0 .2 mol/ L苯胺和 0 .5 mol/ L H2 SO4介质中采用脉冲电流法电解合成聚苯胺 (PANI)膜 .循环伏安研究表明 ,与恒电流法相比 ,脉冲电流法制得的 PANI膜具有更好的电化学活性 .扫描电镜 (SEM)对膜层的微观形貌观察发现 ,这种特殊的聚苯胺膜层呈纳米纤维状结构 ,不同于恒电流法制取的颗粒状 PANI膜 .讨论了脉冲通断比和频率对于膜层性能的影响 .

纳米纤维聚苯胺在电化学电容器中的应用

采用脉冲电流方法(PGM)合成了具有纳米纤维结构的导电聚苯胺(PANI).扫描电子显微镜对膜层观察表明,PANI膜是由直径约为100 nm的掺杂态聚苯胺纤维交织而成.以纳米纤维状聚苯胺组成电化学电容器,研究了其电化学电容性能,并与恒电流方法(GM)制备的颗粒状PANI电容器性能进行了比较.结果表明,在相同的沉积电量下,PGM制备的纳米纤维状PANI电化学电容器比颗粒状PANI电化学电容器具有更大的电容容量,其电化学电容器的比电容可高达699 F·g～1,能量密度为54.6 Wh·kg-1.并且该电化学电容器具有良好的充放电性能和循环寿命.

钢基表面热镀锌镁合金镀层及其耐蚀性能研究

采用电解活化助镀剂法在A3钢基表面制得了镁含量为0.3%～2.0%(质量分数,下同)的热镀锌镁合金镀层,对各种成分的锌镁合金镀层进行了电化学测试和中性盐雾实验,并通过电子扫描显微镜观察了镀层的表面形貌.结果表明,在镁含量小于2%的范围内,随着镁含量的增大,热镀锌镁合金镀层的耐蚀性能逐渐提高,但提高的幅度逐渐降低;随着镁含量的增大,镀层晶粒不断细化,组织结构趋于均匀;镁元素主要分布于晶界,起到细化晶粒的作用.

酰胺低温熔盐中Y-Ni合金薄膜的电化学制备

用恒电流电解法在乙酰胺－尿素－溴化钠熔体中电沉积出Ｙ的质量分数（ｗ（Ｙ））高达８７．５０％的Ｙ－Ｎｉ合金，在铜片上获得附着力强的合金薄膜．实验结果显示电沉积出的Ｙ－Ｎｉ合金中的。ｗ（Ｙ）随着电流密度增大而增大．在低电流密度获得的是带有金属光泽的银白色合金薄膜。

单室无隔膜电解槽中恒电流电解合成丁二酸的研究

旨在寻找和研制电还原顺丁烯二酸制备丁二酸中高活性、高选择性的电极材料,采用自行研制的不锈钢(Stainlesssteel,SS)载表面合金电催化材料(Surface alloy/SS)作为工作电极,利用CV研究了其在常温常压、不同电流密度和支持电解质等条件下顺丁烯二酸电合成丁二酸中的性能,通过离子色谱电导检测等技术对电合成产物进行检测分析.结果表明:Surface alloy/SS电极对顺丁烯二酸的加氢还原表现出很高的电催化活性;对产物丁二酸的选择性高;优化的电解条件为:电流密度27.68 mA·cm-2,0.1 mol·L-1硫酸作为支持电解质.

人工气候与恒电流通电法加速锈蚀钢筋混凝土梁的结构性能比较研究

采用人工气候环境和恒电流通电法对钢筋混凝土梁进行加速锈蚀试验,以钢筋混凝土梁底顺筋锈胀裂缝宽度为标准,对钢筋表面锈蚀特征、锈蚀钢筋力学性能、以及锈蚀钢筋混凝土梁的结构性能进行了试验研究与比较分析。由于人工气候环境与恒电流通电法使混凝土内钢筋锈蚀的电化学机理不同,试验结果表明:在混凝土表面顺筋锈胀开裂宽度相同条件下,两种环境引起的钢筋表面锈蚀特征、锈蚀钢筋名义强度和延伸率、锈蚀钢筋混凝土梁承载能力与延性均有明显的差异。人工气候环境模拟自然环境气候过程,并强化了气候因素的老化作用,使混凝土内钢筋锈蚀具有相同的电化学机理,并达到加速锈蚀的目的,将对进一步研究钢筋锈蚀程度对结构性能退化影响具有重要的学术和实际意义。

三维石墨烯-氧化镍纳米晶复合膜的电容性能

本文首先采用高温化学气相沉积技术（CVD）在泡沫镍模板上生长三维石墨烯（3DG）,然后利用化学浴沉积在石墨烯表面沉积碱式镍沉淀,氩气退火后得吸附氧化镍纳米片晶的石墨烯复合膜（3DG/NiO）。X-射线衍射（XRD）、拉曼（Raman）光谱、场发射扫描电子显微镜（FESEM）表征表明：泡沫镍表面生长了致密的三维石墨烯膜,层与层之间呈现明显的堆垛方式;石墨烯膜表面吸附了大量的NiO纳米片状晶体,相邻的纳米晶相互连接形成多孔结构。循环伏安（CV）曲线研究表明：3DG/NiO膜可作为兼具双电层电容和赝电容性能的复合型电极材料。充放电曲线研究表明：3DG/NiO电极的稳定充、放电比电容处于350~400F·g-1之间,300次循环后仅衰减1.12%,库仑效率保持在95%以上。

锂离子电池负极合金CoSn和Cu-Sn的制备与表征

CoSn alloy and Cu-Sn samples were syn thesized by H 2 -reduction following solid-state r eaction between Co ?,Cu?,Sn?and NaOH at ambient temperature.The samples were characterized by XRD,S EM.The results showed that CoSn alloy(80～200nm)is globe-shaped,ultrafine hexagon al material,and Cu-Sn alloy powder consists of two phases,i.e.Cu 6 Sn 5 and Cu 3 Sn.Cu-Sn powder has spherical morphology and the particle size is estimated to be 60～70nm.The electro chemical performances of CoSn alloy and Cu-Sn powder were studied using lithium-ions model cell Li /LiPF 6 (EC +DMC)/CoSn(or Cu-Sn).It was demonstrated the reversible discharge capacities for 10cycles keep above 280mAh ·g -1 for nanophase Cu-Sn,and 60mAh ·g -1 for CoSn alloy.Differ-ential capacity plots showed that th e reaction mechanisms of Cu-Sn with l ithium were reversible.

聚苯胺薄膜电极的制备及性能研究

文中在Pt电极上用循环伏安、恒电位和恒电流电化学聚合方法制备聚苯胺 (PAn)薄膜 ,对PAn膜电化学合成条件进行了探讨。结果表明 :循环伏安法的扫描电位上限、扫描速度、恒电位法的聚合电位、恒电流法电流密度等因素对PAn膜的物理和循环伏安特性都有很大的影响 。