Electrochemical Deposition of Nanostructured Metals and Alloys from Ionic Liquids

Abstract

Metals like aluminium, magnesium, tungsten or their alloys cannot be electrodeposited from aqueous electrolytes. We have developed a procedure using AlCl3-based ionic liquids for the deposition of nanostructured metals and alloys. The ionic liquids (IL) employed for these studies consist of mixtures of an inorganic (e.g., AlCl3) and an organic component (e.g., 1-butyl-3-methyl-imidazoliumchloride or [BMIm]Cl). In our contribution we describe the electrochemical deposition of less noble metals like Al or Fe and alloys like Al x Mn1−x with a controlled nanostructure. The variation of physical and chemical process parameters allows the deposition of samples with crystallite sizes from 10 up to several hundred nm. Deposits prepared from IL's show remarkable properties. Based on nanoindentation measurements we observe crystallite size dependent microhardness for nanostructured aluminium (from 1.44 GPa (100 nm) to 3.40 GPa (14 nm)). The thermal stability of the deposits was measured by high temperature X-ray diffraction. The deposits show a thermal stability up to 350 °C resulting from oxide impurities in the grain boundaries. An activiation energy of 41 kJ/mol can be determined for the crystallite growth process. The magnetization curves of nanostructurd iron exhibit soft magnetic behavior; the coercivity is inverse proportional to the crystallite size.