Electrochemical investigations of copper behaviour in different cupric complex solutions: Voltammetric study

The electrochemical behaviour of copper has been investigated in different cupric complex solutions by cyclic voltammetry. In pyridinic and picolinic solutions the reduction of cupric complex occurred in two stages leading to Cu(I) and Cu(0), respectively. The electrodeposited copper is oxidized in two steps leading to Cu(I) and Cu(II) as in ammoniacal cupric complex solutions. In glycine, alanine, sulfamic acid and ethylenediamine solutions, the cuprous complex is an intermediate in the cupric complex reduction but it is not detected during the oxidation of the electrodeposited copper in these solutions. In EDTA and triethanolamine solutions, the cuprous complex is not observed. The rate of copper etching was determined in pyridinic and ammoniacal cupric solutions and was shown to be faster in ammoniacal cupric solutions than in the pyridinic solutions.     

Aspects of electrochemical behaviour of carbon steel in different Bayer plant solutions

Cyclic voltammetric and potentiodynamic studies were carried out on 300W carbon steel in Bayer plant solution, at 100 °C, with different alumina concentrations. Alumina behaves as an anodic inhibitor, shifting the critical passivation potentials positively and decreasing the critical passivation current with increasing concentration. Increase in alumina concentration promotes the formation of a uniform and less porous film. The pore resistance model describes the properties of the oxide films. Aluminium was found in all oxides formed, supporting the formation of a mixed oxide Fe_3–x Al _x O₄. Thermodynamic calculation of some equilibrium potentials was carried out using the Fe(OH)₃ ^– ion rather than HFeO₂ ^– ion. Moreover, the Al(OH)₄ ^– ion was considered instead of AlO₂ ^– ion in the oxidation process.     

430不锈钢表面微纳多孔结构阳极氧化膜的制备及疏水性研究

利用扫描电镜(SEM)研究了阳极氧化工艺对SUS430不锈钢在由氟化铵、水及乙二醇(Eg)组成的电解液中制备微纳多孔结构氧化膜的影响,通过能谱仪(EDS)对阳极氧化膜微孔内部和未成孔位置的组成进行了分析,测试了阳极氧化前后不锈钢表面的水接触角。适当降低电解液含水量有利于提高不锈钢表面的微孔密度,可形成微纳多孔结构的氟化铵浓度以0.15 mol/L最好,氧化电压过大以及氧化时间过长都会导致阳极氧化膜发生过度腐蚀。在氟化铵含量为0.15 mol/L、含水量小于0.4 mol/L的电解液中,保持电解液温度为20°C,采用氧化电压50~60 V阳极氧化15~30 min,不锈钢表面可制备出孔径为3~5μm的多孔结构,微米级孔洞内部形成有序的蜂窝状纳米多孔结构(孔径约为100 nm)。阳极氧化后不锈钢表面形成了氧化物和氟化物,与水的接触角为138.2°,具有较好的疏水性。     

Composition and structure of the anodic films on titanium in aqueous solutions

Surface-enhanced Raman spectra of the amorphous film on titanium have been obtained for the first time. The anodic corrosion film at low potentials is identified to be highly disordered TiO₂ with some Ti₂O₃ also present. The presence of the anatase and rutile modifications of TiO₂ at high voltages ( 80V) is confirmed.     

Electrochemical behaviour of passive films on molybdenum-containing austenitic stainless steels in aqueous solutions

Passivation and its breakdown reactions have been studied on Mo-containing stainless steel specimens using different electrochemical techniques. Mo-containing stainless steel specimens were polarized in both naturally aerated NaCl and Na₂SO₄ solutions of different concentrations at 25 ± 0.2 °C between −1000 and 1500 mV versus saturated calomel electrode (SCE). The results of potentiodynamic polarization showed that i_corr and i_c increases with increasing either Cl⁻ or SO₄²⁻ concentration indicating the decrease in passivity of the formed film. EIS measurements under open circuit conditions confirmed that the passivity of the film decrease with increase in either Cl⁻ or SO₄²⁻ concentration.     

Anodic behaviour of alkaline solutions containing copper cyanide and sulfite on the graphite anode

Sulfite may be added to copper cyanide solutions to reduce cyanide oxidation at the anode during copper electrowinning. Anodic sulfite oxidation is enhanced in the presence of copper cyanide. Sulfite also suppresses the oxidation of copper cyanide. The effect of sulfite on the oxidation of copper cyanide decreases with increasing mole ratio of cyanide to copper. This is related to the shift in the discharged species from Cu(CN)₃ ^2– to Cu(CN)₄ ^3– with increasing mole ratio of cyanide to copper. Sulfite is oxidized to sulfate. At [Cu⁺] = around 1 M, CN:Cu = 3.0–3.2, [OH^–] = 0.05–0.25 M, [SO₃ ^2–] = 0.4–0.6 M and the temperature = 50–60 °C, the anodic current efficiency of sulfite reached 80–90%. With further increase in sulfite concentration beyond 0.6 M, the current efficiency of sulfite oxidation will not be increased significantly. Further increase in CN:Cu mole ratio will result in decrease in the anodic current efficiency.     

Electrochemical methods for the study of corrosionin lubricant additive systems

Potentiodynamic polarization has been used to study the corrosion behaviours of mild steel and copper in solutions containing some examples of common types of lubricant additives. A variety of conditions for performing of experiments were investigated. The best results were obtained in a background solution of 0.01m tetra-n-butylammonium perchlorate in 1:1 toluene/ethanol. The behaviour of the aforementioned metals was characterized and compared in solutions containing allyl amine, alkyl phosphite, and organic sulfides. For most solutions, corrosion and pitting potentials and corrosion rates of each metal were found to vary with the compound's concentration. Changes in the corrosivity of chemicals towards metals were monitored as a corrosion inhibitor was added to their solutions. The relative corrosion behaviour observed were consistent with the known performance of these metals in contact with lubricants containing these additives.     

Effect of complexing agents on the electrochemical behaviour of orthopaedic stainless steel in physiological solution

This work is aimed at providing a better understanding of the biocompatibility of stainless steel in the human body, where various biomolecules are able to bind metal ions and convey them from the surface of an orthopaedic implant to various parts of the body. The passivation behaviour of orthopaedic stainless steel was studied by potentiodynamic and potentiostatic electrochemical methods in physiological solution as a function of type and concentration of complexing agents added. The latter were used to simulate the complexing effect of biomolecules in vitro. Two complexing agents, EDTA and citrate, were investigated in the concentration range from 0.1 to 100 mM. Their addition induces a pronounced effect on the passivation characteristics of stainless steel. The results were discussed in the context of the formation of soluble complexes of metal ions, which induces an increase in metal dissolution and disturbs the formation of the passive layer. The degree of increased dissolution appears to be related to the stability constants of the complex formed.     

压裂返排液中不同铁基电极除硼性能的影响与分析

压裂返排液中硼的去除对非常规油气资源的可持续发展具有重要意义。电絮凝作为一种环保技术,近年来受到越来越多的关注。从电化学的角度来看,不同电极的电化学性能具有一定差异,这很大程度上影响着絮凝性能。然而,铁基电极作为经济有效的电极材料,不同铁基电极对除硼效果的影响至今还没有得到系统的研究。本研究采用不同的铁基电极作为阳极,考察了其在电絮凝过程中的除硼性能,并用电化学方法、化学方法及相关表征手段阐述了铁基电极产生不同除硼效果的原因。结果表明,相同条件下,不锈钢作为阳极时的除硼效率为17%左右,比碳钢作为阳极的除硼率大致高出10%。当使用不锈钢电极时,其所在介质的Fe³⁺含量为43%,而碳钢电解时,Fe³⁺含量却仅有30%。此外,不锈钢阳极电解产生的絮凝物具有更分散疏松的形态,粒径分布较为均一,有利于得到更好的絮凝能力。     

Effect of PgTPhPBr on the electrochemical and corrosion behaviour of 304 stainless steel in H2SO4 solution

Weight-loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements were used to study the inhibition of 304 stainless steel corrosion in 1 M H₂SO₄ at 50 °C by propargyltriphenylphosphonium bromide (PgTPhPBr). The inhibiting effects of propyltriphenylphosphonium bromide (PrTPhPBr) and propargyl alcohol (PA) were also studied for the sake of comparison. For the investigated compounds, Tafel extrapolation in the cathodic region gave a corrosion inhibition efficiency of 98% at 1 × 10^–3 M. Adsorption of both PgTPhPBr and PA was found to follow Frumkin's isotherm while adsorption of PrTPhPBr obeys that of Temkin. In the anodic domain, PgTPhPBr acted as a good passivator. The impedance spectra recorded at the corrosion potential (E _cor) revealed that the charge transfer process in the inhibited and uninhibited states controls corrosion of 304 stainless steel.     

Comparative study on electrical properties of copper nanowire/polypropylene and carbon nanotube/polypropylene composites

Nanocomposites using copper nanowires (CuNWs) or carbon nanotubes (CNTs) as fillers with polypropylene (PP) as matrix were prepared by miscible solution mixing and precipitation method. Comparative studies on electrical conductivity and electromagnetic interference shielding properties were reported. On the conductivity curve, a plateau was found for both CuNW/PP composite and CNT/PP composite. The plateaus are located at a different concentration range for each composite type: for CuNW/PP composite, it is between 0.8 and 1.7 vol %, while for CNT/PP composite the plateau occurs in a narrower range between 0.4 and 0.6 vol %. The shielding effectiveness (SE) increases with increased concentration of fillers. CNT/PP composite has higher SE at concentrations less than 2 vol %; the two curves cross near 10 dB at this point and at concentrations higher than 2 vol %, CuNW/PP composite has higher SE. © 2014 American Institute of Chemical Engineers AIChE J, 61: 296–303, 2015     

铁和碳钢在浓碱溶液中的阳极极化曲线

通过极化曲线测量方法研究铁和碳钢在不同浓度的KOH浓碱溶液中的阳极极化行为,结果表明铁和碳钢在浓碱溶液中表现出典型的活化-钝化金属特性.     

Effect of titanium dioxide (TiO2) distribution and minute amounts of carbon black on the opacity of PVDF based white composite films

There is a contradiction in making completely opaque and white plastic film with a required high TiO₂ filling fraction, which resulted in inefficient pigment utilization and high cost. Two methods were used here to overcome the contradiction. Firstly, TiO₂ was grafted with poly(methyl methacrylate) (PMMA) by atom transfer radical polymerization to improve the pigment dispersion in poly(vinylidene) fluoride (PVDF). Secondly, minute amounts of carbon black (CB) were added into the PMMA‐g‐TiO₂/PVDF system to enhance opacity and decrease TiO₂ fraction. The structure, morphology, and properties of PMMA‐g‐TiO₂ hybrid particles and composite films were investigated by FTIR, TEM, TGA, SEM, DMA, covering power meter, and UV/VIS spectrophotometer, etc. It was observed that PMMA‐g‐TiO₂ was dispersed uniformly as individual particles in PVDF due to the good compatibility between PMMA and PVDF. Therefore, the opacity of PMMA‐g‐TiO₂/PVDF films was markedly higher than unmodified‐TiO₂/PVDF ones. Adding minute amounts of CB can significantly increase the opacity of the thin film due to its absorption effect on decreasing light transmittance. The contrast ratio (CR) of the PMMA‐g‐TiO₂/PVDF film with 20 μm thickness and 25 vol % TiO₂ was 97.67%, lower than the critical CR 98% for a complete opacity, however, the CR of sample with 10 vol % TiO₂ was 98.1% as the CB concentration was 2 × 10^?4 g/cm³, saved more than 15% TiO₂. We proposed that a critical thickness d₀ existed for the CB/PMMA‐g‐TiO₂/PVDF composite films, under which the light reflectance increased as a function of thickness, otherwise, the reflectance kept constant. Besides, d₀ could be decreased by increasing CB concentration. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43064.     

Electrochemical behaviour of the antimony electrode in sulphuric acid solutions—I. Corrosion processes and anodic dissolution of antimony

The corrosion processes at open circuit conditions and in the active dissolution region of antimony, at low anodic overpotentials, have been studied in sulphuric acid solutions. It was established that antimony dissolution at open circuit is coupled to oxygen reduction, which occurs via the hydrogen peroxide route. The rate of antimony dissolution was found to increase linearly with increasing acid concentration. Based on potentiodynamic, galvanodynamic and steady-state measurements as well as ac impedance data possible mechanisms for the corrosion processes at open circuit as well as for the dissolution of antimony in the active region are proposed and discussed.     

A study of the dynamics of anodic copper dissolution in a NaCl/KSCN electrolyte

The oscillatory behaviour of the anodic dissolution of copper into an aqueous NaCl solution containing a small amount of thiocyanate ions has been studied experimentally in the absence and in the presence of a magnetic field. The latter has an inhibiting effect on the oscillation and, under specific conditions, it can fully suppress it.     

The passive behaviour of AISI 316 in alkaline media and the effect of pH: A combined electrochemical and analytical study

In this paper, thin surface films were formed on AISI 316 immersed in alkaline solutions of pH ranging from 13 to 9 under open circuit potential conditions. The electrochemical behaviour of the films formed under these conditions was evaluated by different electrochemical techniques: d.c. potentiodynamic polarisation, capacitance measurements (Mott-Schottky approach) and electrochemical impedance spectroscopy. The chemical composition was studied by X-ray photoelectron spectroscopy (XPS).The results reveal a good agreement between the film composition, the electronic properties and the electrochemical behaviour.The analytical results showed that the composition of the surface film changes with the pH. The films become enriched in Cr(III) and Fe(III) species and depleted in Fe(II) and Ni species, as the pH decreases from 13 to 9. The results are consistent with the formation of a film, presenting a bilayer structure, composed of an outer oxide/hydroxide layer, enriched in iron, and an inner anhydrous layer, rich in chromium and nickel oxides.Impedance measurements reveal that the resistance of the surface film increases during immersion and that the pH influences the evolution of the charge transfer resistance and the evolution of the film capacitance.Capacitance measurements based on the Mott-Schottky approach show that the concentration of electronic defects decreases with pH and that the films formed at pH 13 present the highest density of donors and, therefore, a more conductive behaviour.     

Surface and Corrosion Characteristics of a-C:H/Fluorocarbon Films

Fluorocarbon films were deposited on type 301 stainless steel substrates from mixtures of hexafluoroethane (HFE) or hexafluoroacetone (HFA) and acetylene and argon in a radio-frequency (13.56 MHz) plasma discharge. A 10 nm thick polysilicon interlayer was deposited prior to fluorocarbon film deposition to obtain good adhesion. To prevent film failure. a-C:H layer was deposited on the polysilicon layer prior to fluorocarbon film deposition, resulting in a-C:H/fluorocarbon composite film structures. The influence of the feed gas composition on the properties of the layered structure was investigated. Surface energies of the films were calculated from the film contact angle values obtained with water and diiodomethane. The composition of the surface layer of these films was characterized using X-ray photoelectron spectroscopy (XPS). The resistance offered by these a-C:H/fluorocarbon film structures to anodic breakdown in an electrolyte containing 0.1 M NaCl and 0.1 M Na₂SO₄ was studied using a potentiostatic technique. The anodic current density for the coated type 301 stainless steel samples was at least 3 orders of magnitude smaller than that for the bare sample and more than an order of magnitude smaller than that observed with samples coated with only the (equally thick) a-C:H layer. The resistance offered by the layered coatings to solution penetration increased with increasing fluorine content in the films.     

不锈钢表面电化学磷化及膜层性能

采用由4.0 g/L ZnO、4 g/L CaCl₂、5%(体积分数)H₃PO₃、4 g/L酒石酸和3 g/L氯酸钠组成的锌钙系磷化液,在温度为70°C和电流密度为4 mA/cm²的条件下对1Cr₁₈Ni₉Ti不锈钢表面进行电化学磷化20 min。对比了所得磷化膜与采用相同磷化液化学磷化2 h所得膜层的表面形貌、相结构和耐蚀性。结果表明,与化学磷化相比,电化学磷化所需时间较短,所得膜层的结晶大小和分布均匀,耐腐蚀性更好。     

Interfacial processing and adhesion of diamond,diamond-like,and TiN films on metallic and polymeric substrates

Diamond, diamond-like, and titanium nitride (TiN) films have extremely desirable chemical, electrical, and mechanical properties for a variety of applications ranging from corrosion- and erosion-resistant coatings to electronics packaging of microelectronic devices. However, many of these applications are limited by the poor adhesion of these films to metal and polymer substrates. The adhesion of a film is determined primarily by internal stresses in the film, thermal and lattice mismatch, and most importantly by interfacial bonding. We have developed methods based on mechanical interlocking, chemical bonding, grading of interatomic potentials, and the multilayer discontinuous thin films approach to control stresses and strains in thin films. A substantial improvement in adhesion and wear properties is obtained by using these methods selectively. We review issues related to the adhesion of diamond, diamond-like carbon, and TiN films on metal and polymeric substrates.     

碳钢基体镍-磷合金镀层表面沉积TiO2薄膜

采用电沉积法在碳钢镀镍一磷合金镀层表面制备了TiO2薄膜,研究了溶液pH值、沉积时间和电流密度对薄膜增重的影响,分析测定了薄膜的成分及表面形貌。所得最佳工艺条件：pH值为4;时间为40min;电流密度为40-50mA／cm^2。在最佳工艺条件下成功制备了与基体结合良好、致密、均匀的TiO2薄膜。浸泡试验表明TiO2薄膜提高了镍一磷合金镀层在质量分数为10％硫酸和10％氯化钠溶液中的耐蚀性。