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Normal and anomalous electrodeposition of tin–copper alloys from methanesulphonic acid bath containing perfluorinated cationic surfactant
No full textSn–Cu alloys were deposited from a 12?5 vol.-% (1?93 mol dm23) methanesulphonic acid bath containing a perfluorinated, cationic surfactant at 296 K. Electrodeposition was carried out under controlled flow conditions, using rotating disc, rotating cylinder and rotating cylinder Hull cell electrodes. The influences of deposition current and potential, rotation speed, cupric ion concentration, stannous ion level and surfactant concentration on the deposited alloy composition have been investigated. The presence of surfactant resulted in a shift in the Cu deposition potential compared to that of Sn deposition. Both ‘normal’ deposition (Cu deposited at a more positive potential than Sn) and ‘anomalous’ deposition (Sn deposited at a more positive potential than Cu) could be achieved. A series of Sn–Cu alloys was electrodeposited over a wide range of operating conditions to produce matte grey through golden yellow to light brown, surface finishes. Golden yellow coloured bronze deposits, containing 70–80 wt-% Cu and 20–30 wt-%Sn could be obtained. When Sn was deposited preferentially, the Cu content of the alloy was typically in the range 3–9 wt-% along the cathode of the rotating cylinder Hull cell
Composite, multilayer and three-dimensional substrate supported tin-based electrodeposits from methanesulphonic acid
No full textTin and tin–alloy deposits enjoy many applications in the electronics, tribology and engineering industries with potential applications as electrodes for lithium batteries and as electrocatalyst coatings. Methanesulphonic acid (MSA) has become a favoured electrolyte due to its environmental benefits and ability to offer a vehicle for many metal alloy, conductive polymer and composite coatings. A number of emergent uses require less common compositions or structures of alloy, polymer or composite deposits. This paper concisely provides diverse examples of modern tin-containing deposits from aqueous MSA, including Sn–Cu alloys having a very wide composition together with a wide range of colours (golden-yellow–dark-brown) and surface finishes, a Sn–Cu composite deposit containing ceramic, protonated titanium oxide nanotubes for batteries, a tin–copper–bismuth ternary alloy and tin deposits supported on an inert reticulated vitreous carbon or carbon felt substrate to provide a porous, three-dimensional tin surface for electrocatalysis and batteries. The importance of controlled current distribution and electrode/electrolyte movement is illustrated by the use of the rotating disc electrode, rotating cylinder electrode and rotating cylinder Hull cell
Electrodeposition of composite coatings containing nanoparticles in a metal deposit
No full textRecent literature on the electrodeposition of metallic coatings containing nanosized particles is surveyed. The nanosized particles, suspended in the electrolyte by agitation and/or use of surfactants, can be codeposited with the metal. The inclusion of nanosized particles can give (i) an increased microhardness and corrosion resistance, (ii) modified growth to form a nanocrystalline metal deposit and (iii) a shift in the reduction potential of a metal ion. Many operating parameters influence the quantity of incorporated particles, including current density, bath agitation (or movement of work piece) and electrolyte composition. High incorporation rates of the dispersed particles have been achieved using (i) a high nanoparticle concentration in the electrolyte solution, (ii) smaller sized nanoparticles; (iii) a low concentration of electroactive species, (iv) ultrasonication during deposition and (v) pulsed current techniques. Compositional gradient coatings are possible having a controlled distribution of particles in the metal deposit and the theoretical models used to describe the phenomenon of particle codeposition within a metal deposit are critically considered
The electrodeposition of highly reflective lead dioxide coatings
No full textIn the presence of a suitable surfactant, such as hexadecyltrimethylammonium chloride or bromide, highly reflective and hard lead dioxide coatings with a black appearance can be electrodeposited from methanesulfonic acid media at room temperature (295 K). The reflective PbO2 coatings are compact, adherent to the (vitreous carbon or carbon-polymer) substrate and can be formed at current densities of 10 to 100 mA cm?2 at a thickness up to several hundred microns. The coatings were characterised by measurement of surface optical reflectance, surface roughness, surface microstructure, phase composition and crystallite size. The reflective PbO2 films were found to mainly consist of the alpha (orthorhombic) phase with feather-like and orientated microstructures. The crystallite size and surface roughness were in the order of tens of nanometres and their optical reflectance was several orders of magnitude higher than matte coatings produced in the absence of additives
Anodic deposition of compact, freely-standing or microporous polypyrrole films from aqueous methanesulphonic acid
No full textFreely-standing and flexible films (0.075 to 9 mm in thickness) of electrically conducting polypyrrole were synthesised via anodic electrodeposition onto a stainless steel substrate from methanesulphonic acid under stirred conditions at 295 K. Cyclic voltammetry was used to studythe effect of pyrrole monomer concentration (0.01 to 1.0 mol dm-3) and methanesulphonic acid level (1.0 to 6.0 mol dm-3) on the formation of polypyrrole films. The films were prepared for deposition times of 30–240 s at constant current densities of 1 to 15 mA cm-2. The ionic conductivity of freely-standing polypyrrole membranes in aqueous methanesulphonic acid was studied. Scanning electron microscopy was used to image the surface microstructure. The polypyrrole films, which were prepared in the oxidised (methanesulphonate doped), conductivestate, showed an ionic area resistance as low as 10 ohm cm2. The films were readily doped with the methanesulphonate anion and the membrane ionic conductivity was dependent on the electrolyte composition used for their deposition. In the presence of anodic oxygen evolution, thefilms showed a ‘template-free’ porosity due to film growth around the bubbles
A review of developments in the electrodeposition of tin
Full text linkThe importance of tin and its electrodeposition are summarised and the scope for plating tin is outlined. Established applications of electroplated tin include corrosion protection, electronics fabrication and cooking utensils. The past 20 years have seen developments in the science and technology of tin plating, including research into nanostructured deposits, adoption of environmentally friendly methanesulfonic acid baths and more ambitious coatings including multi-layers and composites. Our ability to tailor deposit structure and composition has been improved by newer electrolytes, pulse plating and electrolyte additives. The diversity of tin applications has extended to lithium batteries using newer structures (such as composites, multi-layers and nanostructures), electrical control (e.g., pulsed current) and relative bath/electrode movement (including the use of rotating electrodes). Electrochemical aspects of modern tin deposition are illustrated by data fromthe authors' laboratory which highlights the versatility of methanesulfonic acid electrolytes. A wide range of deposit morphology, colour and surface finish are possible by the use of suitable addition agents and control of electrode/electrolyte movement and operating conditions. Subject areas needing further research work are identified
Strategies for the determination of the convective-diffusion limiting current from steady state linear sweep voltammetry
No full textThe limiting current is an important parameter for the characterization of mass transport in electrochemical systems operating under convective-diffusion control. Four methods to determine the limiting current from current (I) vs. potential (E) plots are considered. Strategies to determine the limiting current values include: 1) direct measurement from I vs. E curves, 2) estimation from the current value at EL =DE/2 where DE is the length of the limiting current plateau), 3) evaluation of the first derivative dI/dE in the I vs. E curve and 4) from plots of E/I vs. I-1. The electrode reactions chosen to demonstrate the different strategies are: Cu(II) ? Cu(I) and Cu(I) ? Cu(0) in 1.5 mol dm-3 NaCl (pH 2) at a platinum rotating disc electrode and K3Fe(CN)6 ? K4Fe(CN)6 in 1 mol dm-3 NaOH at a 60 ppi reticulated vitreous carbon electrode (RVC)
Electrodeposition of copper from mixed sulphate–chloride acidic electrolytes at rotating disc electrode
No full textThe effect of chloride ion on the deposition of copper from low metal concentrations in aqueous, acid sulphate solutions was investigated. The electrolytes contained 0·05 mol dm-3 CuSO4 and 0·5 mol dm-3 Na2SO4 at pH 2 and 296 K. The chloride ion concentration was varied in a wide range from 0·03 to 2·0 mol dm-3. Linear sweep voltammetry was carried out under well defined flow conditions at a smooth platinum rotating disc electrode. The progressive transition from a single, two-electron reaction for the reduction of Cu(II)?Cu(0) to two, single-electron reactions for the reduction sequence: Cu(II)→Cu(I)→Cu(0) was clearly evident as the chloride ion concentration increased. The charge transfer and mass transport characteristics of these reactions were evaluated. The formal potential for the Cu II) reduction to Cu(I), the shift in the potential region for complete mass transport controlled reduction of Cu(I) to Cu(0) and the potential for hydrogen evolution at the deposited copper were also studied. A semi-logarithmic relationship between exchange current density and half-wave potential for Cu(II)→Cu(I) with chloride ion was achieved when the Cl-/Cu(II) ratio in the electrolytes exceeded 2, due to the presence of the Cu(I) dichlorocuprous anion, CuCl2-
A gold-coated titanium oxide nanotube array for the oxidation of borohydride ions
No full textHighly ordered titanium dioxide nanotube (?100 - 200 nm pore diameter) arrays, were formed on a titanium foil by anodising at a cell voltage of 60 V, in two stages. The nanotube arrays were over-coated with nanoparticulate gold using physical vapour deposition (PVD) sputtering resulting in a well dispersed coating. The electrodes were used to study the oxidation of 20 x 10-3 mol dm-3 borohydride ions in 3 mol dm-3 NaOH, at 298 K, by cyclic voltammetry. The gold-coated titanium oxide nanotube array electrodes provided higher electrical charge per unit mass of gold and unit area that a gold nanoparticle deposit on carbon and gold adsorbed on hydrothermally synthesised titanate nanotubes offering a reliable and low cost technique to produce a high surface area anode for a direct borohydride fuel cell
The characterisation of PbO2–coated electrodes prepared from aqueous methanesulfonic acid under controlled deposition conditions
No full textA series of PbO2 coatings on planar carbon substrates has been prepared by anodic deposition in aqueous methanesulfonic acid (MSA) under galvanostatic conditions. The effect of four experimental parameters, i.e., lead(II) methanesulfonate and MSA concentrations, current density, and temperature was analysed. Surface characterisation by XRD, SEM-EDX, and AFM has provided information about the structural (phase distribution, degree of crystallinity, and crystallite size), morphological (crystallite shape, degree of porosity), and tribological (surface roughness) properties of the PbO2 coatings, respectively. Electrochemical studies based on linear and cyclic voltammetry allowed comparison between electrodes prepared in MSA and classical electrodes prepared in HNO3. Pure ?- or ?-PbO2 and ? + ? mixtures were obtained depending on the conditions, being temperature the most influential deposition parameter. A temperature rise caused a transition to pure ?-PbO2 and led to a higher degree of crystallinity with a progressive increase of crystallite size, always within the range of 10–30 nm, as well as to a remarkably higher roughness, from smooth (35–50 nm rms) to rough (up to 500 nm rms) surfaces. Low MSA and high lead(II) methanesulfonate concentrations were required to avoid the formation of excessively porous powdery coatings, as well as cracks, pits, and holes. Most of the coatings obtained in MSA were uniform, nanocrystalline, and moderately rough. Their electrocatalytic behaviour was comparable to that of the electrodes prepared in HNO3, showing an O2-overpotential of +0.66 V in 0.05 M Na2SO4 at pH 3.0. Such coatings can then be envisaged as suitable anodes for energy and water treatment applications. Prolonged electrolysis has shown their stability against leaching
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