Formation mechanism of amorphous Ni-Fe-P alloys by electrodeposition

The formation mechanism of the amorphous Ni-Fe-P coating was studied by analysis of the forming thermodynamics, dynamics, and crystallography of the amorphous alloy. The results show that, in the initial stage of deposition a thin 'crystal epitaxial growth' layer first forms, and then transforms to amorphous gradually. The cross section in Ni-Fe-P coatings by electrolytic etching exhibits a banded structure of alternate dark and light bands. It is proposed that the banded structure is caused by a change in the P content with thickness,which is due to alternated depletion and enrichment of [OH-] in the diffusion layer resulting from the generation and evolution of hydrogen gas. The amorphous Ni-Fe-P coating will be formed in proper composition, high nucleation rate and strongly hindered growth of the crystal nucleus. Amorphous Ni-Fe-P alloys form as islands, and grow up by layer.

Catalytic graphitization of PAN-based carbon fibers with electrodeposited Ni-Fe alloy

Ni-Fe alloy was electrodeposited on the surface of polyacrylonitrile （PAN）-based carbon fibers, and catalytic graphitization effect of the heat-treated carbon fibers was investigated by X-ray diffractometry and Raman spectra. It is found that Ni-Fe alloy exhibits significant catalytic effect on the graphitization of the carbon fibers at low temperatures. The degree of graphitization of the carbon fibers coated with Ni-Fe alloy （57.91% Fe, mass fraction） reaches 69.0% through heat treatment at 1 250 °C. However, the degree of graphitization of the carbon fibers without Ni-Fe alloy is only 30.1% after being heat-treated at 2 800 °C. The catalytic effect of Ni-Fe alloy on graphitization of carbon fibers is better than that of Ni or Fe at the same temperature, indicating that Ni and Fe elements have synergic catalytic function. Furthermore, Fe content in the Ni-Fe alloy also influences catalytic effect. The catalytic graphitization of Ni-Fe alloy follows the dissolution-precipitation mechanism.

Fabrication and characterization of electrodeposited nanocrystalline Ni-Fe alloys for NiFe_2O_4 spinel coatings

Nanocrystalline Ni-Fe FCC alloy coatings with Fe content of 1.3%-39%（mass fraction） were fabricated on the nickel substrates using a DC electrodeposition technique. The crystal structure, lattice strain, grain size and lattice constant of the Ni-Fe alloy coatings were studied by X-ray diffraction technique. The chemical composition and surface morphology of the FCC Ni-Fe alloy coatings were investigated with the energy dispersive X-ray spectroscopy（EDS） and atomic force microscopy（AFM）. The results show that the Fe content of the Ni-Fe alloy coatings has a great influence on the preferred orientation, grain size, lattice constant and lattice strain. FCC Ni-Fe alloy coatings exhibit preferred orientations of（200） or（200）（111）. With an increase of Fe content, the preferred growth orientation of（200） plane is weakened gradually, while the preferred growth orientation of（111） increases. An increase of the Fe content in the range of 1.3%-25%（mass fraction） results in a significant grain refinement of the coatings. Increasing the Fe content beyond 25% does not decrease the grain size of FCC Ni-Fe alloys further. The lattice strain increases with increasing the Fe content in the FCC Ni-Fe alloys. Since the alloys with Fe content not less than 25% has similar grain size（~11 nm）, the increase in the lattice strain with the increase of Fe content cannot be attributed to the change in the grain size.

Thermal Stability of Ni-Fe Alloy Foils Continuously Electrodeposited in a Fluorborate Bath

Nanocrystalline Ni-Fe alloy foils were fabricated by using a continuous electrodeposition system, and then they were annealed at different temperatures ranging from room temperature to 650 ℃. A ductile-brittle-ductile evolution of these alloy foils was observed along with the increase of annealing temperature, and was affected by iron content. The first and second transformation took place at below 300 ℃ and over 500 ℃, respectively. Iron improved thermal stability of nanocrystalline Ni-Fe alloys. The XRD data indicated that for Ni100-xFex (x > 55) alloys bcc to fcc phase transformed at 300 ℃ and completely at 500℃.

Electrodeposition of Al on AZ31 magnesium alloy in TMPAC-AlCl_3 ionic liquids

Aluminum was electrodeposited with constant current on AZ31 magnesium alloy pretreated under optimized conditions from trimethyl-phenyl-ammonium chloride and anhydrous aluminum chloride （TMPAC-AlCl3） quaternary ammonium room temperature ionic liquids with benzene as a co-solvent. The corrosion resistance of the as-deposited Al layers was evaluated in 3.5% NaCl solution by the electrochemical technologies. The Al depositions were characterized by scanning electron microscopy equipped with energy dispersion X-ray. The results show that the microstructures of the Al depositions have spherical equiaxed grains obtained at a high current density, and bulk grains at a low current density. The Al deposition obtained at 12.3 mA/cm2 has a smooth and compact surface. The electrochemical measurements indicate that the thicker Al deposition can more effectively protect the Mg substrate. The Al deposition with bulk grains hardly protects the AZ31 Mg substrate from corrosion owing to its porosity.

Electrodeposition of As-Sb alloy from high arsenic-containing solutions

As-Sb alloy was electrodeposited from high arsenic-containing solutions. The influences of current density, Sb（3＋） concentration, reaction temperature and HCl concentration on the electrolyte composition, cell voltage and current efficiency were investigated. The surface morphology, composition and structure of the deposits were analyzed by scanning electron microscopy（SEM）, inductively coupled plasma mass spectrometry（ICP-MS） and X-ray diffraction（XRD）, respectively. The results show that the prepared As-Sb alloy shows an amorphous structure under all conditions. Under the optimized condition, i.e., 10 g/L As（3＋）, 2 g/L Sb（3＋）, 4 mol/L HCl, current density of 4 mA/cm2 and temperature of 20 °C, desired As-Sb alloy with a composition of 70.26% As and 29.74% Sb（mass fraction） is obtained. What is more, the current efficiency is as high as 94.74% and high arsenic removal rate is achieved under this condition.

Electrodeposition of Cu coating with high corrosion resistance on Mg-3.0Nd-0.2Zn-0.4Zr magnesium alloy

To improve the corrosion resistance, electrodeposition of Cu coating on Mg-3.0Nd-0.2Zn-0.4Zr （mass fraction, %NZ30K） magnesium alloy via an appropriate pretreatment was investigated. The surface morphologies, compositions and microstructures of the pretreated films and Cu coating were characterized in detail. The results show that the activation film consists of fluoride and phosphates and Zn immersion film forms preferentially on the eutectic compound Mg12Nd phase region. A smooth, uniform and dense Cu coating is successfully obtained. Potentiodynamic polarization tests reveal that Cu coating can greatly improve the corrosion resistance of NZ30K magnesium alloy. Open circuit potential （OCP） and electrochemical impedance spectroscopy （EIS） tests during long-term immersion further demonstrate that Cu coating can provide an effective protection for NZ30K magnesium alloy from corrosion up to ~60 h, due to its dense structure and a stable passive film formed. In addition, Cu coating exhibits good adhesion to substrate as confirmed by thermal shock test.

Electrodeposition of aluminium and aluminium-copper alloys from a room temperature ionic liquid electrolyte containing aluminium chloride and triethylamine hydrochloride

The electrodeposition of A1 and A1-Cu binary alloys on to gold substrates from a room temperature ionic liquid electrolyte containing A1C13-EtaNHC1 was studied. The electrochemical behavior of the electrolyte and the mechanism of deposition were investigated through cyclic voltammetry （CV）, and the properties of deposits obtained were assessed by scanning electron microscopy with energy dispersive X-ray spectroscopy （SEM-EDS） and X-ray diffraction （XRD）. A1 of 70μm in thickness and an A1-Cu alloy of 30μm in thickness with 8at% copper were deposited from the electrolyte. SEM images of the deposits indicate that the A1 deposit was smooth and uniform, whereas the Al-Cu deposit was nodular. The average crystalline size, as determined by XRD patterns, was found to be （30±5） and （29±5） nm, respectively, for A1 and A1-Cu alloys. Potentiodynamic polarization （Tafel plots） and electrochemical impedance spectroscopic （EIS） measurements showed that Al-Cu alloys are more corrosion resistant than Al.

Direct electrodeposition of ionic liquid-based template-free Sn Co alloy nanowires as an anode for Li-ion batteries

Sn Co alloy nanowires were successfully electrodeposited from Sn Cl2-Co Cl2-1-ethyl-3-methylimidazolium chloride(EMIC) ionic liquid without a template. The nanowires were obtained from the molar ratio of 5:40:60 for Sn Cl2(25)Co Cl2(25)EMIC at-0.55 V and showed a minimum diameter of about 50 nm and lengths of over 20 μm. The as-fabricated SnCo nanowires were about 70 nm in diameter and featured a Sn/Co weight ratio of 3.85:1, when used as an anode for a Li-ion battery, they presented respective specific capacities of 687 and 678 m Ah·g^(-1) after the first charge and discharge cycle and maintained capacities of about 654 m Ah·g^(-1) after 60 cycles and 539 m Ah·g^(-1) after 80 cycles at a current density of 300 m A·g^(-1). Both the nanowire structure and presence of elemental Co helped buffer large volume changes in the Sn anode during charging and discharging to a certain extent, thereby improving the cycling performance of the Sn anode.

Electrochemical behaviors of Zn-Fe alloy and Zn-Fe-TiO_2 composite electrodeposition

Electrochemical behaviors of Zn-Fe alloy and Zn-Fe-TiO2 composite electrodeposition in alkaline zincatesolutions were studied respectively by the methods of linear potential sweep and cyclic voltammetry. From the re-sults it can be concluded that Zn shows under potential deposition, Zn-Fe alloy codeposition is anomalous codeposi-tion and Zn-Fe alloy cathode polarization is increased with the introduction of additive. From the view point of elec-trochemistry, the reasons that the content of Fe in the Zn-Fe coating changes with the composition of the electrolyteand the process conditions altering and the relationship between the content of Fe and the appearance of the coatingare interpreted. The cathode polarization of Zn-Fe alloy codeposition is enhanced obviously with addition of additive.In the course of composite electrodeposition, TiO2 has less promotion to electrodeposition of zinc ions than to iron i-ons, while the electrodeposition of iron ions improves the content of TiO2 in composite coating, which is inagreement with the results of process experiments.

Electrochemical Synthesis and Magnetic Studies of Ni-Fe-Co-Mn-Bi-Tm High Entropy Alloy Film

Amorphous Ni-Fe-Co-Mn-Bi-Tm high entropy alloy films were firstly prepared by potentiostatic electro- deposition. The results indicate that the six elements can be co-deposited in an organic system of DMF （N,N-dimethylformamide）-CH3CN. The surface of the film is composed of compact and uniform particles with triangular cone shape and a particle size of 100-200 nm. A simple face-centered-cubic structure is identified by XRD patterns after the films were annealed under Ar atmosphere. The annealed alloy film shows soft magnetic properties and the magnetization decreases with Fe content decreasing.

Electrodeposition of Rare Earth Metals and Their Alloys in Organic Electrolytes

The electrodeposition of rare earth metals and their alloys in organic electrolytes are reviewed. The solvents, electrolytes and operetating conditions are discussed. It is concluded that exploring the rare earth salt, which can be highly soluble in organic solvents and easily dehydrated, is the key to the pracitical utilization of electrodeposition of rare earth metals and their alloys in organic electrolytes.

Review of electrodeposition methods for the preparation of high-entropy alloys

High-entropy alloys(HEAs)are suitable for engineering applications requiring excellent mechanical,corrosion,thermal,and magnetic properties.In the last decade,electrodeposition has emerged as a promising synthesis technique for HEAs.Research has focused on the influence of procedure parameters on the deposition of different HEA layers and the effect of their microstructure on their corrosion and magnetic properties.This review of current literature provides comprehensive information on HEAs and the use of direct and pulse electrodeposition as a synthesis technique for these materials.This review also addresses the research gaps on HEA production via electrodeposition,such as using other ceramic particles instead of graphene oxide in composite structures based on HEAs.

Preparation of Gd Co alloy in dimethylsulfoxide by electrodeposition method

Electrodeposition of Gd Co alloy film from dimethylsulfoxide (DMSO) electrolyte solutions has been investigated using cyclic voltammogram and potentiostatic technique. Potentiostatic depositions between -1.20 V and -2.70 V were applied to uncomplexed and complexed solution. The deposits obtained at potentials within -2.30～-2.70 V from complexed solutions are silver gray smooth films.

ELECTRODEPOSITION OF AMORPHOUS Ni-P ALLOY COATINGS

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Electrodeposition of Ni-W Amorphous Alloy and Ni-W-SiC Composite Deposits

Ni-W alloys and their composite deposits are electroplated on the metals when an appropriate complex agent is selected on the base of the theories of electrochemistry and complex chemistry, and the principle of induced codeposition. Effects of the bath composition, pH value, temperature and current density on the electrode position of Ni-W alloys and their composite deposits have been investigated, and the effect of heat treatment temperature on the hardness, structure and cohesive force of the amorphous Ni-W alloys and their composite deposits are also discussed. Results showed that the alloys containing more than 44 wt pct W content and the composite deposits containing 7.8 wt pct SiC content could be obtained by making use of the appropriate bath composition and plating conditions. Alloys and their composite deposits with over 44 wt pct W content show amorphous structure. The hardness of amorphous Ni-W alloys and their composite deposits increases obviously when heated, and can reach to 1350 HV and 1520 HV respectively for 46 wt pct W content. The cohesion on Cu, carbon steel and stainless steel is very good.

Electrodeposition of Ni-Cr alloy on aluminum substrate

Ni-Cr alloys with mass fraction of 1.4%23.9%Cr, 76.1%98.6%Ni, and hardness of 70.5 80.5HR were electrodeposited on aluminium substrate from the trivalent chromium sulphate-chloride solution using citric acid as complexing agent. The aluminium was pretreated by means of degreasing and eroding, polishing and twice chemical immersion of zinc. The effects of electrodeposition parameters such as current density, temperature, pH value and bath concentration on the composition and hardness of deposits were investigated. The results show that the Cr content increases with the increase of current density and the decrease of temperature, and that it increases with the increase of pH value to a maximum and then decreases. The increase of Cr content leads to the increase of hardness of the Ni-Cr layers. The deposits with high Cr content are of good corrosion resistance. Good adherence of Ni-Cr deposits to aluminium substrate is obtained. The Ni-Cr alloys are the Ni-Cr solid solution with fcc crystalline structure. The Ni-Cr alloy deposits are fine, bright and smooth and compact.

Electrodeposition of Er-Ni Alloy Film in Dimethylsulfoxide

The cyclic voltammetry and chronoamperometry were used to investigate the electrochemical behaviors of Er(Ⅲ) and Ni(Ⅱ) in LiClO 4 DMSO(dimethylsufoxide) system on Pt and Cu electrodes. Experimental results indicated that the reduction of Er(Ⅲ) to Er and Ni(Ⅱ) to Ni were irreversible in one step on Pt and Cu electrodes. The diffusion coefficient and electron transfer coefficient of Er(Ⅲ) in 0.01 mol·L -1 ErCl 3 -0.1 mol·L -1 LiClO 4 DMSO system at 303K were 1.47×10 -10 m 2·s -1 and 0.108 respectively, and the diffusion coefficient and electron transfer coefficient of Ni(Ⅱ) in 0.01 mol·L -1 NiCl 2-0.1 mol·L -1 LiClO 4 DMSO system at 303K were 3.38×10 -10 m 2·s -1 and 0.160 respectively. The homogeneous, strong adhesive Er Ni alloy films with metallic lu- stre was prepared by potentiostatic electrolysis on Cu electrode in ErCl 3 NiCl 2 LiClO 4 DMSO system at -1.90～ -2.55 V (vs SCE).

ELECTRODEPOSITION OF Ti-Ni ALLOY IN UREA-NaBr-KBr MELT

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Electrodeposition of Compositionally Modulated Zinc-cobalt Alloy Multilayer Coatings

The effects of pulse parameters on the cobalt content, surface morphologies and grain size of Zn-Co alloy deposits were studied using a pulse plating technique with a square-wave current containing reverse pulse. Average current density and reverse anodic current density amongst the variables investigated have very strong effects on the cobalt content in the Zn-Co alloy deposits. Grain size, surface appearance and internal stress in the deposit were improved significantly by introducing the reverse current. Varieties of Zn-Co alloy compositionally modulated multilayer (CMM) coatings with large differences in cobalt contents for different sublayers were electrodeposited by designing corresponding waveforms using a computer-aided pulse plater and characterized in terms of surface morphologies. Cross-sectional morphologies of the Zn-Co alloy CMM coatings, examined using field emission gun scanning electron microscopy (FEGSEM), confirmed the layered structure.