Electrodeposition of aluminum from the aluminum chloride-1-methyl-3-ethylimidazolium chloride room temperature molten salt plus benzene

The constant current electrodeposition of bulk aluminum on copper substrates was investigated in the Lewis acidic [> 50 mole percent (m/o) AlCl3] aluminum chloride-1-methyl-3-ethylimidazolium chloride room temperature molten salt (AlCl3-MeEtimCl). Although aluminum can be electroplated from the neat molten salt, we have found that the quality of the electrodeposit is greatly enhanced by the addition of benzene as a ''cosolvent.'' Electrodeposits produced in such melts exhibited a grain size on the order of 5 to 15 mu m. The lattice parameters of these electrodeposits were slightly smaller than the Joint Committee on Powder Diffraction Standards (JCPDS) value; this was attributed to the presence of vacancies in the aluminum lattice that were present at concentrations ranging from about 0.1 to 0.5 atomic percent (a/o). The copper substrate was found to have a slight (311) texture as determined by x-ray diffraction; however, ail of the electrodeposits exhibited a preferred (220) crystallographic orientation with the intensity of the (311) reflection being equal to that of a randomly oriented sample. The (200) and (111) reflections were relatively weak. The relative intensity of the (220) reflection increased and those for the (311), (200), and (111) orientations decreased as the benzene concentration was increased. A Williamson-Hall treatment indicated that microstrain in the electrodeposits was essentially nonexistent.