A Study of Benzotriazole as an Addition Agent for Acid Copper Sulphate Solutions

During a study of addition agents for acid copper sulphate solution, it has been shown that benzotriazole forms an insoluble cuprous complex which codeposits with the copper^1a A method has been devised for dissolving the deposit and separating the addition agent and it has been deffionstrated that benzotriazole can be recovered from the electrodeposit in the undecomposed form.² Since benzotriazole can be separated and estimated with accuracy, it provides a compound which is eminently suitable for studying addition agent action during electrodeposition. Polarization studies have shown that benzotriazole markedly increases the activation overpotential of the cathode η_A—mainly by decreasing the active area of the surface by film formation—and it is possible to detect 10^?7 M benzotriazole from its effect on the cathode overpotential. Additions of 0·012 g/1 benzotriazole give very fine grained deposits of copper and prevent epitaxy, while higher concentrations (0·12 g/1) result in fully-bright deposits with a banded structure. The effect of plating variables on the amount of benzotriazole included in copper deposits has been studied as a necessary prerequisite for suggesting a mechanism of addition agent action which, in this particular system, has been based on the formation of metal complexes.     

Microstructure and crystallographic characteristics of nanocrystalline copper prepared from acetate solutions by electrodeposition technique

Methane sulphonic acid is an alternative electrolyte for conventional sulphuric acid for copper deposition. The electrodeposition of copper from eco-friendly acetate-based electrolytes consisting of copper acetate, sodium acetate and methane sulphonic acid was dealt. Thamine hydrochloride (THC), saccharin and 4-amino-3-hydroxynaphthalene 1-suphonic acid were used as additives in depositing electrolytes. The cathode current efficiency was calculated using the Faraday's law. Metal distrbution ratio of the solutions was determined using Haring–Blum cell. These additives impact the surface morphology of deposited copper films by downgrading, the grain size was analyzed by scanning electron microscopy (SEM) and X-ray diffiraction technique. XRD pattern acquired for electrodeposited copper film shows polycrystalline and face centered cubic structure (FCC). The crystal size of the copper film was calculated using the Debye–Scherrer's equation. The crystal size revealed that deposits produced from additive containing electrolytes exhibited the lowest grain size. Texture coefficient analysis studies revealed that all copper film deposits are polycrystalline and the crystals are preferentially oriented and parallel to the surface. A uniform and pin-hole free surface morphology and grain refining were brought about by the additives.     

Oxidation Potentials in Matte Smelting of Copper and Nickel

The oxidation potential, given as the base-ten logarithm of the oxygen partial pressure in bars and the temperature [log pO₂/T, °C], defines the state of oxidation of pyrometallurgical extraction and refining processes. This property varies from copper making, [?6/1150]; to lead/zinc smelting, [?10/1200]; to iron smelting, [?13/1600]. The current article extends the analysis to the smelting of copper and nickel/copper sulfide concentrates to produce mattes of the type Cu(Ni)FeS(O) and iron silicate slags, FeO_xSiO₂—with oxidation potentials of [?7.5/1250].     

Fabrication of thin copper mesh for electromagnetic interference of display panel by pulse reverse current method and study on the microstructure by small angle neutron scattering

A copper sheet with mesh was mass-produced by continuously combining three techniques, electroforming with pulse-reverse current, transfer technique onto a transparent polyimide (PI) film and oxidation processes. Thiourea as an organic additive in a modified copper sulfate bath changes the reduction potentials of copper complexes, which results in effectively controlling the crystal orientation, surface roughness and microstructure of the copper layer. An electroformed copper layer without thiourea has a relatively rough surface with an average surface roughness of about 144.7 nm, whereas, the copper layers with thiourea have a smooth surface with an average surface roughness in the range of 6.3 to 12.1 nm. The copper layers with thiourea have a preferred orientation of crystal structure such that Cu (111) peak intensity increases, whereas, Cu(220) peak intensity decreases with thiourea addition. Electroforming with a rectangular pulse current density including etching at +640 mAcm^?2 for 1.8 msec and plating at ?160 mAcm^?2 for 4 msec in a modified copper sulfate bath with 200 ppm-thiourea at 25 °C is one of optimum conditions to massproduce a copper mesh sheet roll with 300 ??m pitch, 10 ??m mesh width and thickness, and 200 m long.     

Recovering Silver from Photographic Process Wastes

Spent color bleach-fix solution (CBFS), a product of photographic processing operations, is a potential source of silver. Of the extraction reactors used in recovering this silver, the rotating cylindrical electrode (RCE) has an advantage in that it provides improved mass transfer with an extended effective surface area. In addition, the application of a potentiostatic technique allows the silver deposition reaction to take place preferentially, without the formation of silver sulfide. The process consists of prior physical treatment, subsequent chemical reduction of the ferric-EDTA (ethylene diamine tetra-acetic acid) complex present in the CBFS with sodium dithionite (monitored by measuring the redox potential of Fe³⁺/Fe²⁺ couple), followed by electrodeposition of silver in a divided cell using a cation exchange membrane. The combined procedure results in increased current efficiency and reduced electrolysis time.     

Corrosion and corrosion inhibition of Cu-20%Fe alloy in sodium chloride solution

The electrochemical behavior of copper (Cu), iron (Fe) and Cu-20%Fe alloy was investigated in 1.0 M sodium chloride solution of pH 2. The effect of thiourea (TU) addition on the corrosion rate of the Cu-20%Fe electrode was also studied. Open-circuit potential measurements (OCP), polarization and electrochemical impedance spectroscopy (EIS) were used. The results showed that the corrosion rates of the three electrodes follow the sequence: Cu < Cu-20%Fe < Fe. Potentiostatic polarization of the Cu-20%Fe electrode in the range −0.70 V to −0.45 V (SCE), showed that iron dissolves selectively from the Cu-20%Fe electrode surface and the rate of the selective dissolution reaction depends on the applied potential. At anodic potential of −0.45 V, thiourea molecules adsorb at the alloy surface according to the Langmuir adsorption isotherm. Increasing thiourea concentration (up to 5 mM), decreases the selective dissolution reaction and the inhibition efficiency η reach 91%. At [TU] > 5 mM, the dissolution rate of the Cu-20%Fe electrode increases due to formation of soluble thiourea complexes. At cathodic (−0.6 V), the inhibition efficiency of thiourea decreases markedly owing to a decrease of the rate of the selective dissolution reaction and/or desorption of thiourea molecules. The results indicated that thiourea acts mainly as inhibitor of the selective dissolution reaction of the Cu-20%Fe electrode in chloride solution.     

Anodic dissolution of gold in alkaline solutions containing thiourea, thiosulfate and sulfite ions

Gld dissolves electrochemically in alkaline solutions containing ligands to form complex ions with gold ion.Therefore,selective leaching of noble metals is expected without dissolution of base metals such as steels,aluminum alloys in scrap treatment.Gold electrodes were investigated using linear sweep voltammetry,EQCM method and potentiostatic eclectrolysis in alkaline solutions containing thiourea,Na2SO3 and Na2S2O3.The solution composition,electrode potential affect gold dissolution rate and current efficiency.The gold dissolved from anode electrode forms complex ions,suspension particles as compound precipitates and deposits on cathode electrode as a metal.Anodic efficiency for gold dissolution is between 10% and 22%.This is caused by the oxidation decomposition of sulfite ions and thiourea.The statbility of the alkaline solution containing these elements was also estimated by capillary electrophoresis technique.     

The Effect of Cyclic Lactams and Their Structural Analogs on the Surface Morphology,Coating Properties,and Electroreduction Kinetics of Cu(II) Ions

The behavior of cyclic compounds in copper-plating sulfate electrolytes is directly determined by their structure (the nature of a heteroatom in a ring, the size of the cycle, and the presence of side carbonyl groups). The efficiency coefficient increases with an increase in the volume concentration of an additive in the presence of nitrogen-containing heterocycles, whereas that of oxygen-containing ones slightly depends on c _L ⁰ . Calculation of the kinetic parameters of the process confirmed that kinetics of a cathode reaction is mainly due to the nature of a heteroatom in the cycle. Combined analysis of chronopotentiometry and impedance data showed that the complexes formed in the surface layer block the electrode surface, increase the Ψ′ potential, and make the discharge of metal ions difficult, with their inhibitory effect increasing with an increase in ligand concentration. Effective control of deposition rate, morphology, and properties of coatings is possible as a result of changes in the nature, structure, and volume concentration of the additives.     

Impedance of NiSi electrode in sulfuric-acid solution in the region of passive and transpassive states

The behavior of an NiSi electrode in 0.5 M H₂SO₄ in the region of passive and transpassive state (from 0.50 to 2.1 V (versus SHE)) is studied. The conclusion is made about formation of oxide film close to SiO₂ by composition on the electrode surface in the passivation process. Equivalent electric circuit modeling passive and transpassive state of nickel silicide is proposed. Thickness of oxide film and its specific resistance depending on electrode potential are calculated basing on the impedance data.     

The Effect of 10-Methylacridinium and Potassium Iodides on the Salt Passivation of Copper and α-Brass in Chloride Solution

A comparative study of potassium and 10-methylacridinium iodides as inhibitors of copper and -brass anodic dissolution depending on the potential, rotational speed of disk electrode, and concentration of additives is performed. The effect of additives on the film formation at the metal surface is determined.     

Microstructural study of NiCrAlY electrodeposits

Pulse electrodeposition technique was used to co-deposit Ni with NiCrAlY powder on Ni-based high temperature alloy substrate. Pure nickel anode was immersed in a standard Watt’s bath containing fine particles of NiCrAlY powder that were entrapped during electrodeposition to form a NiCrAlY electrodeposit on cathode specimen surface. Diffusion heat treatment was conducted in argon at ≈1150°C and the samples were oxidized at 1000°C in air. Scanning and transmission electron microscopy coupled with energy dispersive X-ray spectroscopy and X-ray diffraction were used to characterize the microstructure and identify the phases. Pulse electrodeposition resulted in dense and fine-grained deposit with the formation of Al₂O₃ oxide at the coating surface after exposure to high temperature.     

Antifriction coatings of Pb–Sn–Cu alloy electro-deposited from methanesulphonate bath

Abstract

Electrodeposition of antifriction Pb–Sn–Cu coatings from a bath based on methanesulphonic acid (MSA) has been investigated. The bath contains two specially selected organic additives which modify both the structure and the appearance of deposits, prevent the oxidisation of Sn(II) ions and allow the increase of tin content in deposits. The antifriction lead (～90%)–tin (～8%)–copper (～2%) films are deposited from the MSA-electrolyte at a current density of 4 A dm^?2 and a bath temperature of about 20–25°C. Inhibition of the Sn²⁺ ions discharge reaction is observed when the ternary alloy is deposited on the cathode. The Cu²⁺ ions discharge proceeds at a diffusion limiting current. Simultaneous co-deposition of copper has no effect on the kinetics of both lead and tin electrodeposition. Wear characteristics of the deposits from the methanesulphonate bath do not differ from those obtained from the usual fluoroborate bath.     

Structural Characterization and Corrosion Stability of a Si-Doped DLC Coating Applied on Cylinder Liner

The aim of this work was to characterize the structure and electrochemical behavior of a silicon-doped diamond-like carbon (DLC) film deposited by hollow cathode plasma immersion ion process (HCPIIP) on a cylinder liner for heavy duty diesel engine. The film structure was characterized by scanning electron microscopy, x-ray diffraction, and Raman spectroscopy. Nanoindentation tests were performed to evaluate the film hardness and Young’s modulus. Monitoring of the open circuit potential with time, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization measurements was performed in a solution consisting of 0.25 wt.% NaCl + 5.0 wt.% H₂SO₄ at room temperature. The results showed that the film has an amorphous nature consisting of a mixture of sp³ and sp²-like carbon bonds with an I _D/I _G ratio of 0.87. Nanoindentation tests showed that the H/E ratio of the DLC film was 0.102. EIS measurements indicated that the impedance values were higher for the DLC-coated material. Potentiodynamic polarization curves revealed that the corrosion current density was almost three times lower for the coated alloy. The HCPIIP process was considered successful to enhance the surface properties of the cylinder liner.     

Fe-Zn Alloy Coating on Galvannealed (GA) Steel Sheet to Improve Product Qualities

Galvannealed steel sheets (GA) have become the mainstream steel sheet for automobile applications because of their superior corrosion resistance, paintability, and weldability. To impart specific properties, different coatings on GA steel sheet were reported to improve properties further. In this context, we have developed an electroplating process (flash coating) for bright and adherent Fe-Zn alloy coating on GA steel sheet to enhance performances such as weldability, frictional behavior, phosphatability, and defect coverage. A comparative study with bare GA steel sheet was carried out for better elastration. The electroplating time was reduced below 10 s for practical applicability in an industrial coating line by modulating the bath composition. Electroplating was performed at current density of 200-500 A/m² which yielded with higher cathode current efficiency of 85-95%. The performance results show that Fe-10 wt.% Zn-coated GA steel sheet (coating time 7 s) has better spot weldability, lower dynamic coefficient of friction (0.06-0.07 in lubrication), and better corrosion resistance compared to bare GA steel sheet. Uniform phosphate coating with globular crystal size of 2-5 µm was obtained on Fe-Zn flash-coated GA steel sheet. Hopeite was the main phosphate compound (77.9 wt.%) identified along with spencerite (13.6 wt.%) and phosphophyllite (8.5 wt.%).     

Effect of conditions of formation of composite pyrographite/Nafion-polyaniline-Pt anode upon electrooxidation of methanol

The effect of the conditions of formation (regime of formation and sequence of deposition of composite components, pH of the solution) of a multicomponent composite anode including polyaniline, Nafion, and platinum on the activity of such an anode in the course of electrocatalytic oxidation of methanol is studied. An explanation of the observed regularities of platinum and polyaniline codeposition is suggested on the basis of the data on the electrode surface topography obtained using the atomic force microscopy technique.     

On the Electrodeposition of Tungsten-Cobalt Alloys From Aqueous Solutions

Sound coherent deposits of tungsten-cobalt alloys with up to 60–66 wt. % of tungsten can be produced at cathode current efficiencies of up to 21% from solutions containing 40–70 g./l. of tungsten as sodium tungstate, 4–12 g./l. of cobalt as cobalt sulphate, 70–150 g./l. of citric acid and 50 g./l. of ammonium chloride, adjusted to room-temperature pH of 7·5–8·5 with sodium hydroxide, and operated at 50–70° C. with interrupted d.c. pulses of 0·05–2 sees, and equal or rather greater “off” periods, the cathode current density during the pulses being 5–20 amps./dm.². Moderate agitation of the solution is desirable.

Hydrogen overpotential for hydrogen deposition from citrate buffers is much less on tungsten-cobalt cathodes than on tungsten or cobalt cathodes. Evidently the electronic structure of the alloy cathodes is much more favourable than that of tungsten for hydrogen deposition: this suggests that it is also more favourable for tungsten deposition, which may help to explain why tungsten-cobalt alloys are so much more easily deposited than pure tungsten.

A number of amphipathic organic molecules, among them thiourea, benzenesulphonamide and pyridine, increase the hydrogen overpotential on tungsten-cobalt alloys: but they do not increase the cathode current efficiency of alloy deposition, evidently because they increase the metal-deposition overpotential about equally.     

The role of addition agents in the electrodeposition of Ni-Mn-Zn alloys from a sulphate bath

The modifications caused by the addition agents dextrin, glucose, l-serine, β-alanine and glycine during the electrodeposition of Ni-Mn-Zn alloy have been investigated as a function of various plating variables. The electrolytic bath contained 20 g l^-1 nickel sulphate, 80 g l^-1 manganese sulphate, 20 g l^-1 zinc sulphate, 30 g l^-1 ammonium sulphate, 18 g l^-1 thiourea and 0.8 g l^-1 ascorbic acid. Bright light grey, smooth and unevenly fine-grained deposits were generally formed in all cases except for β-alanine which gave blackish-grey, uneven and coarsely crystalline deposits. The nickel content in the deposits was found to increase with the addition of dextrin, glucose or l-serine and was decreased on adding β-alanine or glycine to the bath. In contrast, the zinc content followed the reverse trend under similar conditions. The percentage of manganese, however, was always smaller when glucose, β-alanine or glycine were added to the bath but was greater with the addition of dextrin or l-serine. Further, the alloy composition also changed with increasing concentration of these agents.The cathode current efficiency was found to increase linearly in each case as the current density was increased and remained almost unaffected by the presence of the above additives at a given current density. Dextrin, glucose and l-serine were observed to lower the cathode polarization at a given current density; β-alanine and glycine caused the values for the throwing power polarization to increase. Comparatively large values for the throwing power were thus obtained when dextrin, glucose or l-serine was added to the bath.Attempts have been made to explain the results on the basis of adsorption and other theoretical aspects of electrodeposition.     

Tantalum—processing,properties and applications

Tantalum— the Earth’s 49th most abundant element— is frequently produced as a by-product of tin smelting. The metal is also extracted from concentrates by reduction with sodium or fused-salt electrolysis; tantalum carbide is produced by carburization of Ta₂O₅ or tantalum hydride. Sintering, electric-arc melting and electron-beam melting are used to refine and purify raw tantalum. Tantalum’s unique properties make it suitable for a number of diverse applications, including capacitors, chemical equipment, hard-metal tooling and alloys. Tantalum consumption is expected to increase in the capacitor market, because of the demand for electronics equipment.     

金属铜电沉积过程中分形研究

以环形金属铜片作为阳极，细铜丝作为阴极，研究了酸性电解液条件下金属铜电沉积过程中的二级枝晶生长现象，测定了沉积时间－电流关系曲线，对外加电压，电解液中硫酸铜浓度等对金属铜的电沉积产物形貌及其分维数的影响进行了观测，分析。研究发现，沉积过程中，电流随沉积时间的增加而变大，沉积产物的分维数随电解液中硫酸铜的增加而变大，随外加电压的变动而波动。     

Adsorption of thiourea on polycrystalline platinum: Influence on electrodeposition of copper

Although previous works have shown the marked influence of thiourea as an organic additive in electrolyte bulk on copper electrodeposition, a variety of mechanisms could be responsible. The present paper concerns the effect of a thiourea layer adsorbed prior to copper electrodeposition. First evidence of a monolayer on platinum substrate was revealed by X-ray photoelectron spectroscopy. Two different times (15 h and 1 min) for platinum immersion were tested, and it was observed that, even for short times, thiourea is chemisorbed on the surface. Then, effects of thiourea adsorption on copper underpotential deposition (UPD) and overpotential deposition (OPD) processes on polycrystalline platinum were investigated by polarisation curves, atomic force microscopy and X-ray photoelectrons. Thiourea monolayer increases the copper UPD process: in fact the current density of UPD cathodic peak is higher in the presence of thiourea on the platinum surface. However no modifications were observed on the AFM images and on the XPS spectra. For the copper OPD process, the presence of thiourea monolayer inhibits copper deposition: the current density of OPD cathodic peak is lower whatever the immersion time of the platinum substrate in the thiourea solution. Moreover, XPS spectra show that the presence of thiourea modified the oxidation state of the copper coating, as an oxide film is formed more quickly on the surface of the coating.