Electrodeposition of Al-W Alloys in the Lewis Acidic Aluminum Chloride−1-Ethyl-3-Methylimidazolium Chloride Ionic Liquid

Abstract

The electrodeposition of non-equilibrium Al-W alloys was investigated in the Lewis acidic 66.7-33.3 percent mole fraction aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl 3 -[EtMeIm]Cl) room-temperature ionic liquid (IL). The W(III) compound, K 3 [W 2 Cl 9 ], served as the reservoir for W. Both controlled potential and controlled current techniques were employed. Depending on the electrodeposition conditions, it was possible to prepare Al-W alloys with a W content approaching 96 percent atomic fraction (a/o). However, as the W content of these alloys increased above 30 a/o, the deposits became powdery and friable and were difficult to characterize. XRD analysis of deposits containing ∼16 a/o W revealed a broad reflection consistent with the amorphous phase that typically appears at alloy concentrations that exceed the limit of the supersaturated solid solution. This phase is not readily apparent in X-ray diffraction patterns until the W content reaches about 9 a/o. As expected, the lattice parameter for the fcc Al phase decreased as the W content of the alloy increased, reaching a maximum contraction of about 0.2%, consistent with a W content of about 5 a/o. This suggests that the amorphous phase may be present in deposits containing a little as 5 a/o W. Alloys containing ∼3 a/o W were dense and compact and displayed a chloride pitting potential of +0.3 V versus unalloyed Al. Heat treatment was explored as a method to address the powdery morphology of those deposits with a high W content, but XRD analysis indicated that this approach leads to the precipitation of at least one new phase (Al 5 W) and a decrease in the chloride pitting potential.

Electrodeposition of Al-W Alloy Films in a 1-Ethyl-3-methyl-imidazolium Chloride-AlCl3Ionic Liquid Containing W6Cl12

“…12 As reported in a series of studies on sputtered Al-W alloys, Al-W alloys exhibit higher pitting potentials with increasing W content. 1,3,4,[6][7][8] However, the Al-W alloys electrodeposited from the K 3 W 2 Cl 9 bath had powdery morphologies and were easily exfoliated from the substrate when the W content was >5 at.%, making it difficult to carry out polarization experiments.…”

“…[10][11][12] Of these methods, electrodeposition has particular advantages in that a uniform film can be formed relatively quickly and continuously, onto substrates having complex shapes, using simple equipment. Various Al-based alloy films have been electrodeposited in molten salts such as NaCl-AlCl 3 with the addition of ion sources for the alloy component.…”

“…10 Recently, the electrodeposition of Al-W alloy films from an EMIC-AlCl 3 bath with the addition of the W(III) compound K 3 W 2 Cl 9 was reported. 11,12 Although the W content of the Al-W alloys reached nearly 96 at.%, the deposits with high W content had powdery morphologies. When the current density was high (>20 mA cm −2 ), dense Al-W alloy films were obtained, but the W content decreased to <3 at.%.…”

Review—Electrochemical Surface Finishing and Energy Storage Technology with Room-Temperature Haloaluminate Ionic Liquids and Mixtures

“…These alloys are formed at or less than 0 V vs. Al(III)/Al without difficulty. Many Al alloy systems have been prepared by this route, including Al-Mg, 77 Al-Ti, [78][79][80] Al-Zr, 81 AlHf, 72 Al-V, 82 Al-Cr, [83][84][85][86][87][88] Al-Mo, 89 Al-W, 73 Al-Mn, 90,91 Al-In, 74 and Al-La. 44 It has been determined by X-ray diffraction techniques that Al-Zr, Al-Cr, Al-Mo, Al-W and Al-Mn in particular form amorphous glass phases.…”

Potential Oscillation Associated Galvanostatic Deposition of Periodic Al Wires from a Chloroaluminate Ionic Liquid

“…Ionic liquids (ILs) have attracted numerous interests in electrochemistry and electrodeposition 12,13 especially for the deposition of materials such as Al 14 that are difficult to obtain from aqueous baths. Materials with various morphologies, specifically, metals/alloys wires, [15][16][17][18][19][20][21] have been electrodeposited from ILs with and without the need of template.…”