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 AlxMn1−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.
A recently introduced shear-flow-free method for measuring the rotational viscosity of a resonantly forced torsional pendulum is used to determine the transverse magnetic relaxation time in magnetite and cobalt-based ferrofluids. From these data the average size of the ferromagnetic grains and their hydrodynamic diameter (core plus surfactant coating) are deduced under in-situ conditions, i.e. without diluting the sample. The reliability of the method is demonstrated by comparing the results with those of the complementary techniques of magneto-granulometry, X-ray diffraction, electron microscopy, and photon-correlation spectroscopy.