Nucleation and morphology studies of aluminum deposited from an ambient-temperature chloroaluminate molten salt

Aluminum deposition from AlCl sub(3):MEIC (1-methyl-3-ethylimidazolium chloride) has been studied employing an inverted optical microscope to perform in situ optical observations during the deposition process at a 250 mu m diam tungsten electrode. Thin, continuous aluminum coatings with nuclei (or cluster) sizes below optical microscopic resolution are produced from a 1.1:1.0 AlCl sub(3):MEIC molten salt using constant potential deposition at potentials less than or approximate to -0.2 V vs. an Al(III)/Al reference electrode. At less negative potentials, the microscopic structure consists of larger ( > 0.5 mu m), optically resolved nuclei. Analysis of chronoamperograms indicate that the deposition process involves progressive nucleation with diffusion-controlled growth of the three-dimensional nuclei. Calculated nuclear site densities and average nuclei sizes are in agreement with optical and electron microscope images.