Electrodeposition of Aluminum–Tungsten Alloy Films Using EMIC–AlCl3–W6Cl12 Ionic Liquids of Different Compositions (original) (raw)
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Journal of The Electrochemical Society, 2017
The electrodeposition of Al-W alloy films in a Lewis acidic 1-ethyl-3-methyl-imidazolium chloride (EMIC)-AlCl 3 ionic liquid using W 6 Cl 12 as the W ion source was investigated. W 6 Cl 12 dissolved in the ionic liquid at a higher concentration than other W ion sources used in previous studies. Potentiostatic electrodeposition was performed in a bath containing W 6 Cl 12 at a concentration of 49 mM. Dense Al-W alloy films containing up to 12 at.% W were electrodeposited at potentials more negative than 0 V vs. Al/Al(III). The deposition current density at >0 V was lower than 0.3 mA cm −2 , while that for Al-W alloy films was higher and reached 38 mA cm −2 at −0.5 V. The deposition of W was induced by the deposition of Al. At lower W concentrations, the Al-W alloy films were composed of a super-saturated solid solution, and in the W content range of 9-12 at.% they comprised an amorphous phase. Potentiodynamic polarization and nano-indentation showed that the Al-W alloy films containing 10-12 at.% W exhibited high pitting corrosion resistance, high hardness, and low Young's modulus.
Surface and Coatings Technology, 2017
Al-W alloy films with various W contents up to ~12 at% were prepared by electrodeposition using 1-ethyl-3-methylimidazolium chloride (EMIC)-AlCl3 ionic liquids with different concentrations of W precursor, W6Cl12. The hardness (H) and Young's modulus (E) of the films were examined by nano-indentation. The films were composed of a single-phase fcc Al super-saturated solid solution, an amorphous phase, or
Surface and Coatings Technology, 2006
The electrodeposition and surface morphology of aluminium on tungsten (W) and aluminium (Al) electrodes from 2 : 1 molar ratio AlCl 3 -[EMIm]Cl ionic liquids were investigated. Analyses of the chronoamperograms indicate that the deposition process of aluminium on W substrates was controlled by instantaneous nucleation with diffusion-controlled growth, while the deposition processes of aluminium on Al electrodes were found to be associated with kinetic limitations. Constant potential deposition experiments showed that the electrodeposits obtained on both W and Al electrodes between − 0.10 and −0.40 V (vs. Al(III)/Al) are dense, continuous and well adherent. Dense aluminium deposits were also obtained on Al substrates using constant current deposition between 10 and 70 mA/cm 2 , and the current efficiency was found to be dependent of the current density varying from 85% to 100%.
The corrosion behavior of sputter-deposited aluminum–tungsten alloys
Electrochimica Acta, 2002
Thin films on aluminum–tungsten alloys were prepared by co-deposition of pure aluminum and pure tungsten, each sputtered by an independently controlled magnetron source, on glass and sapphire substrates. Completely amorphous films were obtained in the Al80W20–Al67W33 composition range. Passivity and corrosion behavior of amorphous Al–W alloys were investigated in 1 M deaerated hydrochloric acid solution using polarization and impedance spectroscopy measurements and have been correlated with the properties of pure alloy components. Tungsten and sputter-deposited Al–W thin films are inherently passive materials while aluminum undergoes pitting corrosion in hydrochloric acid solution. The passive film formed at the OCP on each alloy possesses excellent electric and dielectric properties comparable to those of the isolating film on tungsten. The absolute impedance increases with increasing tungsten content in the alloy. According to electrochemical polarization measurements, alloying Al with W in solid solution significantly enhances the material's resistance to pitting corrosion by shifting the breakdown potential above 2000 mV (Al67W33) and lowering the corrosion rate at the OCP by more than two orders of magnitude. The most likely mechanism explaining the passivity of amorphous Al–W alloys, the Solute Vacancy Interaction Model (SVIM), involves the formation of complexes between highly oxidized solute atoms (W+6) and mobile cation vacancies, which restrict the transport of Cl− through the oxide film and inhibit its breakdown in hydrochloric acid solution. The role that film stress relaxation effects and microscopic defects in amorphous Al–W films, of the some composition, and deposited on various substrates play in their corrosion resistance is discussed.
Journal of Materials Science and Technology -Shenyang-
Electrochemical deposition and nucleation of aluminum on tungsten electrode from AlCl 3 -NaCl melts were studied by cyclic voltammetry, chronopotentiometry and chronoamperometry. Cyclic voltammetry and chronopotentiometry analyses showed that Al (III) was reduced at 200 • C in two consecutive steps in an electrolyte of molten AlCl 3 -NaCl system with a composition 52:48 molar ratio. The current-time characteristics of nucleation aluminum on tungsten showed a strong dependence on overpotentials. Chronoamperometry showed that the deposition process of aluminum on tungsten was controlled by an instantaneous nucleation with a hemispherical diffusion-controlled growth mechanism. The results could lead to a better understanding of the AlCl 3 -NaCl melt system that has technological importance in electrodeposition of metals as well as in rechargeable batteries.
Surface and Interface Analysis, 2013
Tungsten heavy alloys (WHAs) are kind of composite materials; these alloys provide a unique combination of properties such as high density, excellent mechanical properties and good corrosion resistance that making them increasingly attractive in many practical applications. In this work, the corrosion behavior of the investigated tungsten heavy alloys with the composition of (95% W-3.5% Ni-1.5% Fe), (93% W-4.5% Ni-1.0% Fe-1.5% Co) and (90% W-6% Ni-4% Cu) fabricated by either chemical or mechanical technique has been evaluated through potentiodynamic polarization measurements in different aqueous solutions of 0.6 M NaCl, 0.1 M HCl and 0.1 M NaOH. The extent of the corrosion has been illustrated by examining the surfaces of WHAs before and after the corrosion test using SEM. It includes general dissolution, localized attack of the binder phase and tungsten grain loss, where the extent of each of these depends on the fabrication technique and the alloy composition as well as the pH of the medium.
Diffusion and corrosion behaviour of tungsten-implanted Aluminium and the Al12W phase
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1990
into aluminium were studied as a function of the annealing temperatures using the Rutherford backscattering technique. The formation of the Al,,W metastable alloy starts at a temperature of 450 o C. Electrochemical corrosion studies show a shift in the corrosion potential of + 600 mV for the as-implanted samples relative to the nonimplanted ones. This shift is 50 mV lower for samples where the Al,,W me&stable alloy has been formed. However, the implanted samples show higher corrosion rates than the nonimplanted ones.
Electrochimica Acta, 2011
In this study, Al was electrodeposited on a platinum substrate at room temperature from an ionic liquid bath of EMIC containing AlCl 3 using potentiostatic polarization (PP), galvanostatic polarization (GP), monopolar current pulse polarization (MCP) and bipolar current pulse polarization (BCP). Transition of current or potential during galvanostatic or pulse polarization revealed that the initial stage of the deposition process was controlled by a nucleation process depending on the polarization condition. For example, the average size of Al deposits decreased with increasing current density in the case of GP. FE-SEM observation showed that dense and compact Al deposits with a smooth surface were obtained by the current pulse method. Roughness factor evaluated from electrochemical impedance measurement confirmed the smooth surface of these deposits. Adhesion strength of Al deposits was greatly improved by using BCP in which an anodic pulse was combined with a cathodic pulse for electrodeposition. In this study, the optimal parameters for BCP were found to be I C =-16.0 mA cm-2 , I A = 1.0 mA cm-2 , r C (duty ratio) = 0.5, and ƒ = 2 Hz. The mechanisms of electrodeposition by these three methods are discussed.
Electrochimica Acta, 2009
Electrorefining of aluminum alloy was investigated using AlCl 3 and 1-ethyl-3-methyl-imidazolium chloride (EMIC) (molar ratio AlCl 3 :EMIC = 1.65:1) ionic liquid electrolyte on copper and aluminum cathodes at temperature of 90 ± 3 • C and cell voltage of 1.5 V. The effect of electrode surface modification and cathode overpotential on deposit characteristics of aluminum was investigated. The surface modification of electrodes reduced the dendritic depositions of aluminum. It was also observed that cathodic overpotentials obtained from experiments using modified electrodes are significantly lower than those of unmodified electrodes. A non-dendritic deposit of aluminum was observed even after prolonged electrorefining of 25 h. Pure aluminum deposits were obtained for all experiments with the current efficiencies in the range of 94-99%.