电化学修复过程中钢筋析氢稳态临界电流密度测定实验方法

采用动电位极化测定方法,在测得钢筋的阴极极化曲线之后,通过对其进行一阶微分分析,确定了钢筋的临界析氢电位及相应的析氢电流密度,之后采用稳态测量法获得钢筋析氢稳态临界电流密度。结果表明,动电位极化曲线能够记录阴极电化学反应的变化过程,一阶微分曲线出现突变点之前,阴极反应以耗氧反应控制为主,突变点之后以析氢反应控制为主;并可以测定钢筋混凝土中钢筋析氢稳态临界电流密度,从而判断氢脆发生的可能性。采用该方法测得钢筋混凝土试件的析氢稳态临界电流密度约为0.355 A/m2。     

含Ag抗菌双相不锈钢表面腐蚀产物的XPS分析

采用X射线光电子能谱技术(XPS)研究了含Ag抗菌双相不锈铸钢在有菌环境中经电化学极化后的表面腐蚀产物。结果表明:添加纯Ag颗粒制备的不锈钢经1150℃固溶处理后,其钝化膜表层中的Ag主要以Ag2+氧化物和游离态的形式存在,Cr主要以CrO2,CrO3和Cr(OH)3形式存在,而添加150～300μm Cu-Ag中间合金颗粒制备的不锈钢经1150℃固溶处理后,其钝化膜表层中的Ag主要以Ag2+,Ag+和Ag2/3+氧化物形式存在,Cr以CrO2、Cr2O3和CrO3等多价态铬氧化物形式共存,且与前者相比,添加150～300μm Cu-Ag中间合金颗粒制备的材料其钝化膜中Cr2O3、钼氧化物和MoO42-的含量更多,而α-FeOOH和Cr(OH)3等氢氧化合物以及水合物的含量更少,表明其钝化膜的稳定性优于添加纯Ag颗粒制备的材料。     

氨络合物体系电积锌的阴极过程

采用CHI650电化学工作站测定了在锌氨络合物体系中锌电沉积的稳态阴极极化曲线及电流-时间暂态曲线.结果表明:锌的阴极电结晶过程是以瞬时成核方式进行的,随外加电位负移,晶体的向外生长速率增大;添加剂的加入不会改变锌阴极电沉积的成核方式,但将大大减小晶体的向外生长速率.通过对不同NH3浓度下测得的阴极极化曲线的分析,可获得各条件下的平衡电位,以及阴极过程动力学参数(交换电流密度J°、传递系数α),进而推导出溶液中存在的主要离子为Zn(NH3)2 4,在阴极直接放电的络离子为Zn(NH3)22 .     

交流阻抗法研究工业纯钛的性能

采用交流阻抗技术结合恒电流阴极充氢和动态阴、阳 极极化法，研究了工业纯钛在海水中的阴极极化性能.结果表明：极化曲线所表现的lgI～E关系与交流阻抗法得出的lg(Rp)～-E关系和lg(Cd)～-E关系有对应性；交流阻抗的结果更直接地反映工业纯钛在海水中阴极极化后的表面状态变化，极化电阻Rp随着阴极电位的增大，呈下降趋势，微分电容Cd随着阴极电位的增大，呈上升趋势.充氢后的钛阳极溶解电流增大.     

AD—1添加剂对锡锌合金电沉积阴极行为的影响

采用旋转园盘电极法,微分电容法,循环伏安法和极谱法研究了 Sn-Zn 合金电沉积过程中的阴极特性。实验表明,在 Sn-Zn 合金电沉积过程中,AD-1添加剂起着重要作用,添加剂在阴极表面的扩散吸附及阻化作用使合金析出电位负移,并明显增加阴极极化,从而使合金结晶致密,保证了镀层质量。     

真空热处理制备Cr2O3-石墨插层化合物工艺参数研究

以三氧化铬(CrO3)与石墨为原料,利用真空热处理方法制备了三氧化二铬(Cr2O3)-石墨的插层化合物(GICs).运用X射线衍射(XRD)分析石墨插层化合物.结果表明:经热处理后,在1400℃时CrO3与石墨(石墨∶CrO3=1∶1)与形成了纯5阶的石墨的插层化合物.XRD分析表明,对网状层面结构的天然石墨,可以利用真空热处理的方法使一些非碳反应物(Cr2O3)插入石墨层间,从而改变石墨的层面结构.X射线光电子能谱(XPS)分析和表征了Cr离子以3价的形式存在于石墨插层化合物中.     

1Cr18Ni9Ti高温氧化行为研究

采用熔模精密铸造法制备1Cr18Ni9Ti耐热不锈钢,用氧化增重法在800℃对1Cr18Ni9Ti耐热不锈钢进行100 h氧化腐蚀实验.采用扫描电镜(SEM)观察其基体组织及各氧化阶段的显微组织彤貌;采用X射线衍射仪(XRD)对该材料最终高温氧化产物进行定性分析.结果表明:ICr18Ni9Ti耐热不锈钢在800℃下的氧化曲线符合抛物线规律;其氧化破坏形式以点蚀为主;最终氧化产物由CrO、Fe2O3(六方)、Fe2O3(立方)、CrTiO3、NiTiO3和Ni3TiO5等混合组成.     

碱性有机体系中铝阳极的电化学行为

为了提高铝的活化性能和减少铝的腐蚀,用电化学方法研究了碱性甲醇有机体系及加入添加剂饱和Ca(OH)2对铝阳极(w(Al)=99.999%)电化学行为的影响.结果表明:浓度4 mol/L KOH-甲醇 w(H2O)30%体系能大幅度抑制铝的腐蚀,但极化程度有所增大;添加剂饱和Ca(OH)2,使铝在浓度4 mol/L KOH-甲醇 w(H2O)30% 饱和Ca(OH)2中的电化学活性接近在浓度4 mol/L KOH水溶液中的活性;在1.20 V处的电流密度比无添加剂时的提高了1.402倍;开路电位值Eocp为-1.870 V.同时铝的腐蚀速度降低,缓蚀率为87.67%.     

不锈钢镀铬液有机添加剂新工艺

往常规镀铬溶液中加入有机添加剂,采用不同的电流密度、镀液温度、pH值和电镀时间进行镀铬,经过对镀层的形貌、厚度及结合力等性能进行比较取舍,获得了最佳镀液配方和工艺:CrO3250g/L,H2SO42.5g/L,Cr3 3g/L,甲醛8~10g/和丁二酸8~10g/L;在室温(20℃),镀液pH值为1.5,电流密度30A/dm2,电镀时间60min。该法既提高镀铬液的阴极电流效率又降低生产能耗,可获得光亮平滑、硬度高、结合力好的镀铬层。     

西南地区某输油管道外腐蚀分析

目的研究西南地区某输油管道外腐蚀行为。方法现场检测,对土壤理化性质及腐蚀产物成分进行室内分析。结果开挖点A的土壤呈弱碱性,土壤腐蚀性弱,管道发生轻微均匀腐蚀,腐蚀产物主要为FeO(OH),Fe(OH)3和Fe3O4等铁的氧化物,对应的阴极反应为吸氧反应;开挖点B的土壤酸性强,硫酸根离子浓度高,土壤腐蚀性强,管道发生严重坑蚀,腐蚀产物主要成分为FeSO4·7H2O及少量碱式硫酸铁,对应的阴极反应以析氢反应为主。结论开挖点土壤的理化性质差异,导致管道的腐蚀形态、腐蚀产物和腐蚀机理显著不同。     

掺杂钨丝电沉积铬的工艺研究

为了研究掺杂钨丝（真空镀铬加热元件）表面电解沉积一定厚度（≥100μm）金属铬的工艺,详细考察了不同温度、电流密度、沉积时间等对镀层的影响,并对镀层进行了性能测试。结果表明,最佳工艺条件为：铬酐150—180μg／L,硫酸1．5～1．8g/L,稀土（La^3＋）添加剂0．5-1．5#L,温度为55℃,电流密度为8～10A／dm^2,电镀时间3h。此工艺条件下所得镀层光亮,色泽好,厚度可达100μm,且镀层耐蚀性好,结合力高。     

高效快速镀铬工艺的研究

开发了一种新型镀铬工艺 .在 45A/dm2 的电流密度下 ,阴极电流效率达 2 6 % .新型复合型镀铬添加剂的加入 ,提高了阴极电流效率及镀液的覆盖能力 ,改善了镀层的性能 ,并在较宽的电流密度范围内可获得光亮的镀层 .     

铬酸钾对铝在磷酸溶液中的缓蚀作用

<正> 一、前言 近年来,人们对常用金属铁在酸中的腐蚀作了较多的研究,但对铝在磷酸中的腐蚀规律的研究还不多见。虽然Colegate等人也曾研究过铬酸钠对铝在磷酸溶液中的缓蚀作用,但未详细讨论动力学方程及动力学参数等重要问题。本工作采用经典的失重法,     

Study by Means of the Mass Spectrometry of Volatile Species in the Oxidation of Cr, Cr2O3, Al, Al2O3, Si, SiO2, Fe and Ferritic/Martensitic Steel Samples at 923 K in Ar+(10 to 80%)H2O Vapor Atmosphere for New-Materials Design

Mass spectrometry was used to study in-situ the role of volatile species in the oxidation of reference materials Cr, Cr₂O₃, Al, Al₂O₃, Si, SiO₂, Fe and ferritic/martensitic steels (P91 and P92) at high temperatures. All samples were heated to 650°C at 1 atm in a mixture of Ar with 10–80% range H₂O vapor. Oxidation times varied between 100 and 200 h. Cr(g), CrH(g), CrO(g), CrOH(g), CrO₂(g), CrOOH(g) and Cr(OH)₂(g) chromium-oxy-hydroxides species were identified during the corrosion of Cr oxidized in a steam atmosphere of Ar+80%H₂O for 100 h. CrO(g), CrO₃(g) and Cr(OH)₆(g) species were present in mass loss of a Cr₂O₃ sample in similar conditions for 200 h of oxidation. However a mass gain was observed when Cr₂O₂(g) and CrO(OH)₄(g) species were present. Simultaneously, thermogravimetric studies of the oxidation kinetics of the samples were made with one in-situ thermobalance. The P91 and P92 steels were studied with afore-mentioned techniques at the beginning of breakaway oxidation. During 100 h of oxidation at 650°C in Ar+10%H₂O atmosphere: Cr(OH)₆(g), CrOOH(g) and CrO₂(OH)₂(g) chromium oxy-hydroxides volatile species were detected in the P91 steel, and Cr(OH)₂(g), Cr(OH)₃(g), Cr(OH)₄(g), CrO(OH)₂(g) and CrO(OH)₄(g), species in the P92 steel. The morphology/composition and structure of the oxidized steel samples were also characterized using SEM/EDAX and XRD techniques, respectively.     

A Rotating Ring-Disc Electrode Study of the Hydrogen Evolution during Zinc Deposition from Zincate Electrolytes

The rotating ring-disc electrode technique offers a simple method for determination of the evolved hydrogen by its detection at the ring during zinc deposition on the disc (steel).

Potentiodynamic investigations have established an increased hydrogen production with shifting of the cathode (disc) potential towards the more negative direction.

The measurements of the ring current versus time at constant disc current show that the hydrogen evolution is intensive mainly in the first 1–2 sec of the zinc deposition. Thereafter it decreases gradually and becomes constant after 3–4 min period from the beginning.

It was found from the cathodic and anodic potentiodynamic curves that the process of hydrogen evolution during zinc deposition was stimulated in the presence of the additives in the electrolyte, particularly by the combinations of basic additives and brighteners.     

Thin-layer electrolytic nickel hydroxide Ni(OH)2 in an electrochemical capacitor

Thin-layer electrolytic nickel hydroxide Ni(OH)₂ has been obtained from an aqueous solution of nickel sulfate and nickel nitrate. The capacitor characteristics of Ni(OH)₂ depending on the synthesis and technology parameters, the thermal treatment and storage conditions of the deposits, the KOH concentration, the potential sweep rates, and the relation with the adverse process of oxygen isolation in an electrochemical capacitor were investigated by cyclic voltammetry. It was established that the optimal KOH concentration in the solution of an electrochemical capacitor is 0.1 M, and it allows one to attain an active material discharge capacitance of 427?C457 F/g. The additional anode polarization of cathode deposited Ni(OH)₂ stabilizes the discharge characteristics of the obtained Ni(OH)₂ + NiO mixture in storage processes. It was established that the mass transport process in the solid state phase is the limiting stage of the Ni(OH)₂/NiOOH system??s electrode process in a KOH medium.     

Application of spherical Ni（OH）2/CNTs composite electrode in asymmetric supercapacitor

1 Introduction Electrochemical capacitors (hereafter ECs) have greater power density than usual batteries and can be deeply discharged without any deleterious effect on life time[1]. Activated carbon(AC) with various modifications is the electrode materia…     

X-ray photoelectron spectroscopy of chromium layers electroplated from oxalate-sulfate solutions

The chemical composition of chromium deposits obtained from acidic (pH 1.5 to 1.7) chromium (III) oxalate-sulfate solutions was studied with the use of x-ray photoelectron spectroscopy. From the solutions containing more than 100 g/l Cr₂(SO₄)₃·6H₂O, an amorphous carbide close to Cr₂₃C₆ with inclusions of metallic chromium clusters is deposited on the cathode. From less acidic solutions poorer in chromium, metallic chromium is deposited. The work was financially supported by the Russian Foundation for Basic Research (projects nos. 99-03-32058 and 96-15-97368).     

碱性锌酸盐体系中Zn的电沉积行为研究简

通过循环伏安、计时电位及电化学阻抗谱技术研究了碱性锌酸盐体系中Zn的阴极还原历程,采用计时电流法结合扫描电镜(SEM)研究了Zn的电化学成核机理。结果表明:溶液中Zn主要以Zn(OH)42-形式存在,Zn(OH)42-通过前置转化反应生成Zn(OH)2;Zn(OH)2在阴极界面上分两步放电,第一步放电后生成Zn(OH)ad吸附在电极表面,而后经第二步放电还原为Zn,两步均不可逆。外加电位为-1.40~-1.50 V时,体系中仅发生Zn(OH)2的第一步放电反应;电位负移至-1.60 V时,Zn(OH)2经历了两步放电过程,但Zn仅吸附在电极表面,电沉积过程处于一种非稳态;当电位负移至-1.70~-1.80 V时,吸附态Zn才持续进入晶格形成完整镀层。体系中Zn的电结晶过程遵循三维连续形核方式。