Research On Aluminum Electrodeposition Using AlCl₃-BMIC Ionic Liquid Under High Gravity Field

Ionic liquid, an ionic compound presented a liquid state at room temperature, which is composed of anions and cations, is used for electrodeposition of active metals such as aluminum at relatively low temperature. In this paper, the influence and discipline of high gravity for aluminum deposition in ionic liquid were researched. Electrical conductivities of AICI3-BMIC ionic liquid were measured and aluminum deposition was studied in general and high gravity respectively.The results indicated that electrical conductivities of AlCl3-BMIC increased with increasing the temperature, which can be described by Kohlraush empirical formula. When x(AlCl3) is less than 0.6, electrical conductivities increased with increasing molar fraction of AlCl3. When x(AlCl3) is between 0.6 and 0.714, electrical conductivities began to decrease, but the tendency of decreasing is gently. Dendrite aluminums were easily obtained in general gravity and the coatings were poor adherent, but aluminum content is 97.68%. The deposition rate of aluminum increased with the enhancement of gravity coefficient at the same current density. When the high gravity coefficient was 162, the deposition rate was 1.5-2.5 times than that of general gravity. In the range of investigative current densities, deposition rate increased with the increasing of current density in the same gravitational field strength, and there was approximate linear relationship between them. The morphology and chemical composition of aluminum deposits were characterized by scanning electron microscope coupled with EDS microanalysis and X-ray diffraction. Results revealed that, the dendrite coatings were avoided, and a uniform, dense, shining aluminum layers were deposited on the cathode under different gravity coefficient. Aluminum coatings showed good adherent, even sometimes the compact layers must be stripped from the cathode by adopting mechanical approach. Under G=104, homogeneous surface distribution were obtained and Al content is 97.31%at the condition of current density J=18 mA/cm2, and current efficiency of aluminum coating was 84.5%. Results of XRD indicated that all of the electrodeposits exhibited a strong preferred (111) crystallographic orientation. Compared with the (200) reflection, the (220), (311), and (222) reflections were relatively weak.