Electrodeposition of cobalt-nickel alloys from ammoniacal single-complex baths

The electrodeposition of cobalt-nickel alloys has been studied from ammoniacal single-complex baths containing 5–50 CoSo₄·7H₂O, 5–50 NiCl₂·46H₂O, 20–50 g dm^?3 (NH₄)₂SO₄ and 250–350 cm³ dm^?3 NH₄OH (20.5% solution). The effects of the plating current density and the concentrations of the bath constituents on the cathodic polarisation, current efficiency and composition of the alloy were investigated. A wide range of alloy compositions with a current efficiency of 60–80% could be obtained from the main baths examined. The alloy plating system interchanged between the normal and the anomalous types depending upon the plating current density and the concentration of NH⁺₄ ion in the bath. Electron microscopic and X-ray diffraction studies proved that the structure of the electrodeposited alloy was controlled by the alloy composition.     

Magnetic properties of nanocrystalline iron group thin film alloys electrodeposited from sulfate and chloride baths

Systematic studies of iron group binary (NiCo and CoFe) and ternary (CoNiFe) thin film alloys relating their magnetic properties with film composition, grain size and the corresponding crystal structure were investigated. Anions influence current efficiencies, magnetic properties, surface morphology and phases of electrodeposited films. Higher current efficiencies in chloride baths compared to sulfate baths were observed for CoFe, NiCo and CoNiFe alloys. The higher deposition current efficiencies in chloride baths were attributed to a catalytic effect. Anion types in CoFe and CoNiFe thin film alloys influenced the microstructures and the resulting magnetic properties (coercivity and squareness). The microstructures of NiCo alloys depend on the deposit Co contents rather than anion types. The surface morphologies of CoFe, NiCo and CoNiFe thin films were independent of anion types. CoFe deposits exhibited relatively smooth surface morphology and turned into fine crystallites with increasing solution Fe⁺² concentration. NiCo deposits showed very smooth surface morphology. CoNiFe deposits had the surface morphology of polyhedral crystallites. The deposit Fe content in CoFe electrodeposits linearly increased with increasing solution Fe⁺² concentration for both chloride and sulfate baths. Similar linear behavior of deposit Co contents was observed in NiCo electrodeposits.     

非晶态Ni—Mo合金的电沉积

从含有NiSO_4、(NH_4)_6Mo_7O_(24)、NaCl、Na_3C_6H_5O_7和NH_3·H_2O的镀液中电沉积具有金属光泽并略带银灰色的非晶态Ni-Mo合金.研究了镀液的组成、pH值及阴极电流密度等对阴极电流效率、合金组成以及合金结构的影响.合金最大钼含量为29.4at%.当镀层中钼含量大于约25at%时,为非晶态结构.此外,还研究了Ni-Mo合金的析氢催化特性.     

Synthesis and characterization of nickel tungsten alloys by electrodeposition

The objective of the current work was to study in detail the effect of bath chemistry, additives and operating conditions on the chemical composition, microstructure and properties of Ni-W alloys deposited from citrate-containing baths, in the absence of ammonia or ammonium salts, on stationary working electrodes. The morphology of the deposits was studied by scanning electron microscopy (SEM) as well as atomic force microscopy (AFM), and the approximate composition by energy dispersive spectroscopy (EDS). Metallographic cross-sections were also analyzed, and micro-hardness tests conducted. The results are discussed in detail with emphasis on routes to increase the tungsten content and deposit thickness, while reducing the extent of cracking.     

Electrodeposition of Zn-Co alloys with pulse containing reverse current

The electrodeposition of Zn-Co alloy deposits was studied by means of pulse-plating technique. The surface morphologies of Zn-Co alloy deposits were examined using scanning electron microscopy (SEM), and an attendant energy dispersive X-ray analyser (EDA) was used to analyse the composition of Zn-Co alloy deposits. Results obtained showed that the average current density and reverse current density amongst all the variables investigated had very strong effects on the cobalt content in the Zn-Co alloy deposits. It is possible to electrodeposit Zn-Co alloy coatings with a very wide cobalt content range of 10-90 wt.% by modulating pulse parameters. Grain size, surface appearance and internal stress in the deposits were also improved significantly by introducing reverse current.     

Electrodeposition and characterization of Cu-Ni-Zn and Cu-Ni-Cd alloys

The electrodeposition of ternary Cu-Ni-Zn and Cu-Ni-Cd alloys was investigated in acidic sulphate electrolytes. The influence of Zn²⁺ and Cd²⁺ ions concentrations as well as the effect of current density on the surface appearance and the deposits’ composition was examined. Sodium dithiolate (NaS)₂CC(CN)₂·3H₂O was used as surface active substance (SAS), and the effect of the SAS on the alloys composition and surface morphology was also investigated. No significant effect of SAS on the alloy composition, however, apparently effect on the deposits surface morphology was observed. It was also noticed that on increasing Zn²⁺ (or Cd²⁺) concentration in the bath, a depletion in the nickel content in the deposit occurred. Deposits obtained were characterized from the structural and morphological points of view. It was found that the structure and morphology of the deposited alloys are mainly controlled by both the applied current densities and the bath composition.     

Electrodeposition of lead alloys from fluoborate baths

The codeposition of some elements with lead from fluoborate baths has been studied in order to obtain lead alloys with a low concentration of a second metal. The metals considered were As, Bi, Cu, Sb, Se, Sn and Te. The chemical analysis of alloys obtained in various electrolysis conditions permitted an investigation of the kinetic behaviour of the metals codeposited with lead. The results showed that only Bi, Sb, Se and Te attain a limiting value of discharge current density and that the codeposition is regular for all metals. SEM observation of the deposits revealed that Sb and Se have a marked influence on the crystal morphology while the remaining metals induce only minor modifications.     

Electrodeposition of PbTe thin films from acidic nitrate baths

Electrodeposition of PbTe thin films from an acidic nitric bath was systematically investigated to understand the kinetics and the effect of electrodeposition conditions on film composition, crystallographic structure, texture and grain size. The electroanalytical studies employed initially with a rotating disk electrode to investigate the kinetics associated with Te, Pb and PbTe electrodeposition. The results indicated that the PbTe thin films were obtained by the underpotential deposition (UPD) of Pb atoms onto the overpotentially deposited Te atoms on a substrate.Based on these studies, PbTe thin films were potentiostatically electrodeposited using e-beam evaporated gold thin films on silicon substrate to investigate the effect of various deposition conditions on film composition and microstructure. The data indicated that the microstructure, composition and preferred film growth orientation of PbTe thin films strongly depended on the applied potential and electrolyte concentration. At −0.12 V, the film was granular, dense, and preferentially oriented in the [1 0 0] direction. At potentials more negative than −0.15 V, the film was dendritic and preferentially oriented in the [2 1 1] direction. A smooth, dense and crystalline film with nearly stoichiometric composition was obtained at −0.12 V from a solution containing 0.01 M HTeO₂⁺, 0.05 Pb²⁺ and 1 M HNO₃.     

Electrodeposition of Sn-Co alloys from gluconate baths

Electrodeposition of Sn-Co alloys was carried out from baths containing 2–20 g dm^–3 SnSO₄, 4–18 g dm^–3 CoSO₄.7H₂O, C₆H₁₁O₇Na and K₂SO₄ under different conditions of bath composition, pH, current density and temperature on to copper substrates. The influence of these variables on the cathodic potential, cathodic current efficiency and composition of the deposit were studied. The results show that the deposition of Sn-Co alloys from gluconate baths depends greatly on the concentration of tin. At high tin concentrations, tin is the more noble component. At low tin concentrations, tin reduction is strongly suppressed due to the formation of a more stable Sn-gluconate complex species and tin becomes the less noble component. The codeposition of Sn-Co alloy from these baths can be classified as an irregular plating system. The surface morphology of deposits was examined by scanning electron microscopy and crystal structure by X-ray. The results show that the structure of the deposits was controlled by the alloy composition.     

Electrodeposition of cobalt-nickel alloys from Watts-type baths

The electrodeposition of cobalt-nickel alloys was carried out from Watts-type baths of composition 5–60gl⁻¹ CoSO₄ · 7H₂O, 100–300gl⁻¹ NiCl₂ · 6H₂O and 25gl⁻¹ H₃BO₃ at a pH of 4.4. The cathodic polarization during electrodeposition and the alloy composition were greatly influenced by the concentrations of the depositable metal ions; whereas, the cathodic efficiency was only slightly affected. Under the examined conditions, the electrodeposition of the alloys belonged to the anomalous type. X-ray diffraction studies revealed that the alloys were deposited in the face-centred cubic structure and consisted of a mixture of the two phases α(Co) andβ(Ni). Sound, smooth and bright alloy deposits were obtained and their properties were improved by increasing the nickel content of the bath.     

Electrodeposition and characterization of thin layers of Zn–Co alloys obtained from glycinate baths

An alkaline bath containing CoSO₄ · 7H₂O, ZnSO₄ · 7H₂O, Na₂SO₄ and NH₂CH₂COOH is proposed for the deposition of thin layers of Zn–Co alloys onto steel substrates. Electrodeposition was carried out at 0.216–1.080 A dm^–2, pH 10 and 10–55 °C. The influence of bath composition, current density and temperature on galvanostatic cathodic polarization, cathodic current efficiency and alloy composition was studied. Different proportions of the two metals were obtained by using different deposition parameters, but at all Zn(II)/Co(II) ratios studied, preferential deposition of zinc occurred and anomalous codeposition took place. Increasing the bath temperature enhanced the cobalt content in the deposit. X-ray diffraction measurements indicated that the phase structure of the deposits was controlled by the applied current density. The Co₅Zn₂₁ phase was formed at low current density, while the CoZn₁₃ phase was formed at high current density. The potentiodynamic dissolution of the coatings showed that they contained Zn–Co alloy of different content and structure.     

Electrodeposition of rhenium-nickel alloys from aqueous solutions

Rhenium-nickel alloys were deposited on copper substrates in a small three-electrode cell, under galvanostatic conditions. The bath solution consisted of ammonium perrhenate, citric acid and nickel sulfamate. The effects of bath composition and deposition time were studied. The Faradaic efficiency (FE) and partial deposition current densities were calculated based on mass gain and elemental analysis using energy dispersive spectroscopy. The surface morphology was characterized by scanning electron microscopy. The thickness of the coating was measured on metallographic cross-sections. The results are discussed with emphasis on routes to increase the Faradaic efficiency and rhenium content in the coating. A plausible mechanism for the electrodeposition of rhenium-nickel alloys is presented.     

Electrodeposition of silver telluride thin films from non-aqueous baths

We describe a method for preparation of crystalline silver telluride films by cathodic deposition from dimethyl sulfoxide (DMSO) solutions containing 0.1 M NaNO₃, 5.0 mM AgNO₃ and 3.5-7.0 mM TeCl₄. X-ray diffraction data indicated that the deposited silver telluride films could be adjusted from Ag excess and stoichiometric monoclinic Ag₂Te to hexagonal Ag₇Te₄ by increasing the concentration of TeCl₄ in the electrolyte or lowering the deposition potential. The Ag₂Te film is gray and the Ag₇Te₄ film is dark blue-gray and mirror like adhered strongly to the substrates. Scanning electron microscopy images show that Ag₂Te films were formed with globular grains with average diameters of more than 1 μm. In contrast, Ag₇Te₄ film consists of triangles characteristic of a (1 1 1) single-crystal with a hexagonal structure in average sizes of about 0.4 μm. The X-ray photoelectron spectra (XPS) indicated that the binding energies deviation of Te3d in Ag₇Te₄ is less than that in Ag₂Te, which is consistent with the apparent valences of Te in Ag₂Te and Ag₇Te₄. Finally, the cathodic deposition reactions were studied by cyclic voltammetry.     

Electrodeposition of silane films on aluminum alloys for corrosion protection

In this paper, three types of protective silane films, methyltrimethoxysilane (MTMS), vinyltrimethoxysilane (VTMS) and dodecyltrimethoxysilane (DTMS) were prepared on aluminum alloys AA 2024-T3 by electrodeposition technique. The Reflection-Absorption Fourier Transform IR (FTRA-IR) measurements showed that, the silane films were successfully deposited through chemical bonding between silane agents and Al alloys. Electrochemical impedance spectroscopy (EIS) tests indicated that in comparison with those by conventional “dip-coating” method, silane films electrochemically prepared at cathodic potentials exhibited obviously higher corrosion resistances. “Critical potential” was all observed for each silane system. Silane films prepared at this potential performed the highest corrosion resistance. The scanning electron microscopy (SEM) images indicated a potential dependence of surface morphology of silane films. The highest compactness was obtained at the “critical potential”. Due to the presence of long hydrophobic dodecyl chain in bone structure, DTMS films displayed the highest barrier properties.     

Electrodeposition of high Mo content amorphous/nanocrystalline Ni–Mo alloys using 1-ethyl-3-methyl-imidazolium chloride ionic liquid as an additive

In the following research, adherent, compact and bright Ni–Mo alloy has been electrodeposited on mild steel in the presence of ionic liquid additive 1-ethyl-3-methyl-imidazolium chloride in ammonia citrate solution using pulse plating technique. The textural components of the coatings were evaluated employing X-ray diffraction (XRD) method. Microstructure, morphology and chemical composition of the coatings were studied using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis. The results revealed that in the presence of ionic liquid at pH of 8.5, Ni–Mo films containing more than 49 wt.% Mo have been carried out whilst no proper deposits have been conducted in additive free solution at the same condition. SEM micrographs showed different morphology of Ni–Mo deposits in the presence of ionic liquid additive. Also XRD patterns represented that present conditions lead to amorphous/nanocrystalline Ni–Mo coatings. Temperature and pH were varied for studying their effects on Ni–Mo characteristics. Moreover the effect of substrate preparation on morphology of coatings was also investigated.     

Electrodeposition of Pb–Cu alloy coatings from gluconate baths

Pb–Cu alloy coatings were electrodeposited on steel sheet cathodes from baths containing mixtures of lead nitrate, copper nitrate and sodium gluconate. Cathodic polarization, cathodic current efficiency and deposit composition were determined under different plating conditions. The results were consistent with the behaviour of a regular plating system with copper being the preferentially depositable metal. The lead (the less noble metal) content in the deposits increased with increase in current density and concentration of lead in the bath but decreased with increase in bath copper concentration. The structure and morphology of the as-deposited coatings were examined by X-ray, AES and SEM. The results showed that the deposits consist of a mixture of fine crystals of the two metals and the morphology of the deposits is mainly controlled by the composition of the deposit.     

Electrodeposition of amorphous gold alloy films

The process for electroplating amorphous gold-nickel-tungsten alloy that we developed previously based on the addition of a gold salt to a known amorphous Ni-W electroplating solution was investigated further using the X-ray diffraction (XRD) method for the purpose of quickly surveying the effects of various experimental variables on the microstructure of the alloy. In this system the gold concentration in the plating bath was found to be critical; i.e., when it is either very low or very high, the deposit becomes crystalline to XRD. The deposit composition varies linearly with the mole ratio of Au to Ni in solution, and the alloy deposit is amorphous to XRD when the atomic ratio of Au/Ni in the deposit is between 0.5 and 1.5. At suitable concentrations of the metal ions, the deposit contains essentially no tungsten. By extending the work on the Au-Ni-W system, an amorphous Au-Co alloy plating process was also developed.     

Pulse plating of Ni-Mo alloys from Ni-rich electrolytes

Pulse plating of Ni-Mo alloys from nickel-rich electrolytes was studied with an inversed rotating disk electrode. The deposit composition and the current efficiency were measured as a function of pulse variables (pulse period, duty cycle) and mass transport parameters (electrode rotation speed, molybdate concentration). At sufficiently short pulse periods, the Mo content of the pulse plated alloys was higher than in dc plating. Experiments using a rotating electrochemical quartz crystal microbalance and Auger electron spectroscopy showed that under the conditions of the experiments no significant corrosion reaction takes place during the pulse off-time. A simplified non-steady state diffusion model can explain the observed enhancement in Mo content and correctly predict the influence of pulse plating variables on deposit composition.     

Electrodeposition of Co–Cu alloy coatings from glycinate baths

The cathodic polarization, cathodic current efficiency of codeposition, composition and structure of Co–Cu alloy as a function of bath composition, current density and temperature were studied. Electrodeposition was carried out from solutions containing CuSO₄ · 5H₂O, CoSO₄ · 7H₂O, Na₂SO₄ and NH₂CH₂COOH. The cathodic current efficiency of codeposition (CCE) was high and it increased with increasing temperature and Cu²⁺ content in the bath, but it decreased with current density. The codeposition of Co–Cu alloys from these baths can be classified as regular. The Co content of the deposit increased with Co²⁺ content and current density and decreased with glycine concentration and temperature. The structure of the deposited alloys was characterized by anodic stripping and X-ray diffraction techniques. The data showed that the deposited alloys consisted of a single solid solution phase with a face-centred cubic (f.c.c.) structure.     

Progress in non-traditional machining of amorphous alloys

Amorphous alloys are a new type of multi-functional advanced material with the properties of general metal materials and glass, which are also called metallic glasses. They have good comprehensive properties, such as a wide application range, low cost, and high reusability. Using reasonable process parameters, non-traditional machining can not only realize the machining of complex amorphous parts, but also avoid the crystallization and oxidation of amorphous alloys, realizing tasks that cannot be accomplished by traditional machining. Therefore, this review systematically summarizes the research status and development potential of amorphous alloys fabricated using non-traditional machining methods. First, we introduce the principles of laser machining, ultrasonic machining, electrical discharge machining, electrochemical machining, and other non-traditional machining methods for amorphous alloys. Subsequently, the influence of the machining parameters and other external conditions on the machining effect is summarized. The machining cost, machining efficiency, and environmental impact of these non-traditional machining methods were compared. Finally, non-traditional machining technology for amorphous alloys is summarized and discussed.