Electrodeposition of Fe70Pd30 nanowires from a complexed ammonium–sulfosalicylic electrolyte with high stability

A highly stable plating bath for the electrodeposition of Fe–Pd nanowires into nanoporous alumina templates has been developed. Complexing of both metal ions and exchanging Fe²⁺ by Fe³⁺ avoid chemical reduction of Pd ions and, therefore, undesirable deposition. By using a pulse potential mode and appropriate adjustment of deposition potentials homogeneously filled templates without surface deposits and nanowires close to the desired composition of Fe₇₀Pd₃₀ have been achieved. These alloy nanowires represent a key step towards nanoactuators based on magnetic shape memory alloys.     

Electrodeposition of Ir—Ru alloys from chloride melts: Steady-state potentials and cathodic processes

Steady-state potentials of Ir, Ru, and glassy carbon are measured at 500–700°C in eutectic NaCl-KCl-CsCl melts containing a mixture of Ir and Ru chlorides. The Ir and Ru steady-state potentials are more positive than their equilibrium values, due to the alloying in the metal surface layer. In the cathodic deposition of alloys, depolarization is observed. Before the limiting diffusion current, Ir-Ru alloys (solid solutions) are plated as compact layers; at higher current densities, the deposit is a powdered dendritic mixture of individual Ir and Ru crystals, rather than the alloy     

Electrodeposition of magnesium–lithium–dysprosium ternary alloys with controlled components from dysprosium oxide assisted by magnesium chloride in molten chlorides

In the work, Gibbs energy showed that MgCl₂ can chloridize Dy₂O₃ and release Dy(III) ions in the LiCl–KCl–MgCl₂–Dy₂O₃ melts. Dy(III) ions were observed by cyclic voltammetry, square wave voltammetry in melts. X-ray diffraction (XRD) pattern of melts indicated that Dy₂O₃ was chlorinated by MgCl₂ and formed DyCl₃. XRD pattern of non-dissolved residue, which was left after the melts were washed with water to remove the soluble salt, showed that the new compounds (i.e., DyOCl, MgO, and Dy(OH)₃) were produced. The concentration of Dy(III) reached a maximum when the concentration of Mg(II) ions exceeded 8?×?10^?4 mol cm^?3 in melts by inductive coupled plasma atomic emission spectrometer analyses of melts. Galvanostatic electrolysis was conducted to extract Dy element from LiCl–KCl–MgCl₂–Dy₂O₃ melts by forming Mg–Li–Dy alloys. The components of Dy and Li in alloys were controlled within a small range by the concentration of MgCl₂ in melts, current density, and additions of Dy₂O₃. XRD patterns of alloys indicated that Mg₃Dy phase was formed. Scanning electron microscope images with energy-dispersive X-ray spectroscopy showed that Dy elements were mainly distributed in the grain boundary. Grain size was refined, due to a more content of Dy elements in alloys by optical microscopy images.     

Electrodeposition of Co–W coatings from boron gluconate electrolyte with a soluble tungsten anode

Conditions were determined in which an active anodic dissolution of tungsten is observed in a borongluconate electrolyte used to obtain Co–W coatings (pH ~6.5) and the nature of critical currents of transition to the passivation was found, which makes it possible to use the tungsten anode as a soluble electrode. The anodic dissolution of tungsten occurs under these conditions with a current efficiency of 90–100%, which, in contrast to the case of a graphite anode, does not lead to an additional oxidation of the electrolyte components and polymerization in solution; in combination with the decrease in the concentration of tungstate ions, this reduces the electrolyte performance. It was shown that the use of a soluble tungsten anode in obtaining nanocrystalline cobalt–tungsten coating can improve the electrolyte performance due to the rise in the current efficiency of electrodeposition and to the increase in the microhardness of the coatings in comparison with the case of an insoluble graphite anode.     

Cathodic reduction of superconducting oxocuprates YBa2Cu3O7− x at high current densities

The cathodic reduction of YBa₂Cu₃O₇ in aqueous electrolytes at ambient temperature turns out to be strongly dependent upon current density with respect to the reaction mechanism. At low current density, topotactic electron/proton transfer is the dominant process, while at higher current densities, two competing reactions appear, i.e. the topotactic conversion and an irreversible reaction leading to products amorphous in terms of X-ray diffraction. Received: 21 April 1999 / Accepted: 7 June 1999     

Electrodeposition,properties, and composition of rhenium–nickel alloys

The process of deposition of the Re–Ni alloy, its current efficiency, and the alloy composition are studied as a function of the current density and the solution temperature. The hydrogen content in the deposits, their surface morphology, internal structure, and properties as the cathodic material for HER are examined. It is assumed that besides the high rhenium content, the high catalytic activity of nickel–rhenium alloys is associated with the high degree of their structural disordering.     

Electrodeposition kinetics of tin—antimony alloy from sulfate electrolyte with organic additives

Kinetics of the Sn-Sb alloy electrodeposition from sulfate electrolytes containing organic additives (syntanol DS-10, Formalin, 1,4-butynediol) is studied by the faradaic impedance method. Bright Sn-Sb alloy coatings are plated in this electrolyte at i_c = 0.5-5 A/dm². With increasing i_c, the Sb content in the alloy decreases from 14 to 6.6 wt %     

Electrodeposition of iron–molybdenum–tungsten coatings from citrate electrolytes

Specific features of the electrodeposition of iron–molybdenum–tungsten coatings from citrate electrolytes based on iron(III) sulfate in the dc mode and with a unipolar pulsed current were studied. It was shown that varying the relative concentrations of salts of alloy-forming metals and the solution pH makes it possible to obtain lustrous compact coatings with low porosity and various contents of high-melting components. The effect of temperature on the coating composition and current efficiency was examined. The current density ranges providing high electrolysis efficiency were found and it was demonstrated that using a pulsed current favors formation of more compositionally homogeneous surface layers at a smaller amount of adsorbed nonmetallic impurities in the coatings. The iron–molybdenum–tungsten coatings are X-ray-amorphous and have better physicomechanical properties and corrosion resistance as compared with the base, which makes it possible to recommend these coatings for application in techniques for surface reinforcement and restoration of worn-out articles.     

Electrodeposition of cobalt–tungsten alloys and their application for surface engineering

Applying electrochemically deposited coatings is a convenient way to improve surface properties of a substrate metal. Today materials for applications are frequently selected according to their functional properties. Nowadays theoretical and practical studies of the co-deposition of tungsten with iron group metals are conducted worldwide, and interest for these studies increases. Tungsten alloys of iron group metals have a high melting point and are often considered high-performance alloys, and the attractiveness in those has been driven by their outstanding properties and multiple possible applications. That research is encouraged by the pronounced mechanical, tribological, and magnetic properties as well as the corrosion resistance of tungsten alloys. The magnetic properties of electrodeposited Co–W alloys are of interest in recording media and remotely-actuated micro-/nano-electromechanical systems. The given research presents an overview of versatile possibilities of Co–W alloys as multiscale materials obtained by electrodeposition from citrate solutions at pH 5–8 and temperatures 20–60°C. The paper discusses electrodeposited tungsten alloys as suitable candidates to meet many technological demands at macro-, micro- and nano-scale as coating films, microbumps and nanowires.     

Electrodeposition of Zinc–Nickel Alloys from Ammonium Oxalate Electrolytes

The electrodeposition of zinc–nickel alloys (5–16 at % Ni) from the ammonium oxalate electrolytes is studied. It is shown that the ratio between the alloy components has an effect on the corrosion resistance of the coatings, their structure, chemical and phase composition, and microhardness.     

Thermodynamic evaluation of viscosity in In–Zn and Sn–Zn liquid alloys

A theoretical formalism that links thermodynamic properties to transport properties has been used to study the viscosity of Sn–Zn and In–Zn liquid alloys at various temperatures. The formalism was successful at describing the thermodynamic properties of these alloys and showed a better estimation of the viscosity of the Sn–Zn alloy than that of the In–Zn alloy.     

Electrodeposition of Multilayered Ni–Cr Films from Sulfate–Oxalate Electrolytes

As shown by scanning Auger electron microscopy and Auger electron spectroscopy, multilayered Ni–Cr thin films can be deposited under the action of periodic currents from sulfate–oxalate solutions containing nickel and chromium ions. The chromium-rich layers have an amorphous structure. In the nickel/chromium interphase region, the carbon content is elevated. Nickel layers contain admixtures of a hydroxide nature.     

Electrodeposition of aluminum–hafnium alloy from the Lewis acidic aluminum chloride-1-ethyl-3-methylimidazolium chloride molten salt

The electrochemistry of Hf(IV) and the electrodeposition of Al–Hf alloys were examined in the Lewis acidic 66.7–33.3 mol% aluminum chloride-1-ethyl-3-methylimidazolium chloride molten salt containing HfCl₄. When cyclic staircase voltammetry was carried out at a platinum disk electrode in this melt, the deposition and stripping waves for Al shifted to negative and positive potentials, respectively, suggesting that aluminum stripping is more difficult due to the formation of Al–Hf alloys. Al–Hf alloy electrodeposits containing ~13 at.% Hf were obtained on Cu rotating wire and cylinder electrodes. The Hf content in the Al–Hf alloy deposits depended on the HfCl₄ concentration in the melt, the electrodeposition temperature, and the applied current density. The deposits were composed of dense crystals and were completely chloride-free. The chloride-induced pitting corrosion potential of the resulting Al–Hf alloys was approximately +0.30 V against pure aluminum when the Hf content was above 10 at.%.     

Molecular electronics at electrode–electrolyte interfaces

Four contemporary examples, all published in recent years, of studies of molecular electronics at electrode–electrolyte interfaces are reviewed in this opinion article. The first illustrative example involves the switching of the redox active molecular wire between redox states, with concomitant changes in molecular conductance. This example illustrates how molecular electronics at electrode–electrolyte interfaces can be used to analyse mechanisms of electron transfer, to distinguish electrolyte effects and to provide details not readily available from ensemble measurements. The second example shows that the fluctuations of molecular conductance of a redox active molecular wire can be followed as a function of electrode potential. This shows how the stochastic kinetics of individual reaction events at electrode–electrolyte interfaces can be followed. The third example demonstrates how electrochemistry can be used to control quantum interference in single molecular wires. The fourth example shows a single-molecule electrochemical transistor concept for well-defined metal cluster containing molecular wires.     

Electrochemical deposition and corrosion stability of Zn–Co alloys

Electrochemically deposited Zn–Co alloys under various deposition conditions were investigated using anodic linear sweep voltammetry for phase structure determination, scanning electron microscopy for surface morphology analysis, atomic absorption spectroscopy for determination of chemical composition, and polarization measurements and open circuit potential measurements for determination of corrosion properties. The influence of deposition current density, temperature, and composition of deposition solution on the phase structure and corrosion properties of Zn–Co alloys was studied. It was shown that the ratio of cobalt to zinc ions in the plating bath strongly affects the chemical content and phase structure, as well as corrosion stability, of Zn–Co alloys. Zn–Co alloys deposited from plating baths with the lowest and the highest ratios of cobalt and zinc ions exhibited the lowest corrosion rate.     

Calorimetric investigation of Al–Zn alloys using Oelsen method

The results of calorimetric study of binary Al–Zn system done according to the Oelsen thermodynamic method are presented in this paper. Main thermodynamic properties, including activities, activity coefficients, partial/integral molar Gibbs excess, and mixing energies were determined at 1,000 K. Positive deviation from Raoult law was noticed, with minimal values of ΔG ^M about ?3 kJ mol^?1 and maximal values of ΔG ^E about +2 kJ mol^?1. The energetics of mixing in liquid Al–Zn alloys has been analyzed through the study of concentration fluctuation in the long-wavelength limit, and weak affinity between Al and Zn atoms in the system was observed. Differential thermal analysis and light optic microscopy were applied in the frame of characterization of investigated binary alloys and phase diagram examination, and the results obtained were in accordance with available literature data.     

Electrochemical extraction of ytterbium from LiCl–KCl-YbCl3-ZnCl2 melt by forming Zn–Yb alloys

Journal of Solid State Electrochemistry - The electrochemical behavior of Yb(III) was studied at a W electrode in LiCl–KCl–ZnCl2 molten salt system. Cyclic voltammetry, square wave...     

Liquid Co–Sn alloys at high temperatures: structure and physical properties

The Co–Sn system is an important subsystem for Sn-based anode materials of lithium-ion batteries. Experimental results on the physical–chemical properties of this system in the liquid state, however, are rather sparse. In this work, the atomic structure and structure-sensitive thermophysical properties (viscosity, electrical resistivity, and thermoelectric power) of liquid Co–Sn alloys were investigated in a wide temperature range with special attention to the melting-solidification region. The obtained experimental results were combined with differential thermal analysis (DTA) data in order to verify the liquidus curve in the Sn-rich part of the Co–Sn phase diagram.     

Molar conductivities of concentrated lithium chloride–glycerol solutions at low and high temperatures: application of a quasi-lattice model

Conductivities of concentrated solutions of lithium chloride in glycerol were measured for concentrations ranging from 0.005 to 1.5 mol.dm^?3. The conductivity dependencies were analysed successively using the Debye–Huckel–Onsager limiting law (DHO) at very low concentrations, the Fuoss equation of 1978 up to 0.1 mol.dm^?3, the Casteel–Amis empirical equation and the quasi-lattice model (QLM) at moderate and higher concentrations. The molar conductivities at infinite dilution, obtained using DHO and QLM were quite different from each other, because the salt forms contact pairs which were underestimated in the Λ = f(C^1/3) in QLM, as it may well be proved by Raman spectroscopy. Besides, the value of Madelung constant suggests that LiCl crystallises face centred cubic (FCC) at higher concentrations. On the basis of Raman spectroscopy analysis of previous lithium salts, we assume that the dissociation coefficient varies slightly with concentration and fraction of paired ion constant, the QLM equation is applied successfully in the concentration range used in this study. The temperature dependency of conductivity was also described using the Vogel–Tamman–Fulcher (VTF) empirical equation where the Arrhenius type was found. The results also suggest that as NaCl, LiCl can be considered as a structure maker electrolyte.     

Effect of pH and volume current density on deposition rate and microhardness of Co–W coatings electrodeposited from concentrated boron–gluconate electrolyte

The optimal pH value of the concentrated boron–gluconate bath for electroplating Co–W coatings is established to be 6.5 (the concentrations of the alloying components are raised by a factor of 5 compared with the commonly used electrolyte). The microhardness of binary Co–W alloys obtained from this bath reaches 1000 kg mm^–2, and electrodeposition proceeds with high current efficiency ( 93–95%). We demonstrate the critical role the volume current density plays in determining the microhardness of the binary coatings electrodeposited from this bath under galvanostatic conditions. We attribute this peculiarity of the investigated system to microhardness size effect, which is associated with structural modifications in the plated coatings that can be induced by changing the volume current density. Using the concentrated bath improves efficiency of electrodeposition.