Pulse current electrodeposition of Al from an AlCl3-EMIC ionic liquid

Abstract: Electrodeposition of aluminum from an AlCl3-EMIC ionic liquid with or without the addition of saturated LaCl3 was carried out by both direct- and pulse-current plating methods. The effects of various parameters, including current density, pulse frequency, current on/off duration (t on and t off), and temperature, on deposit morphology and crystal size were investigated. Deposits prepared by pulse-current plating gave a brighter and flatter surface than those prepared by direct-current plating at appropriate pulse current parameters. Temperature and pulse–current frequency (t off) were shown to significantly affect deposit morphology. Coalescence of grains during t off periods in the pulse current plating was observed, especially at temperatures above 60°C. Increasing the temperature from 25 to 90°C caused an increase in deposit grain size and resulted in a change of grain shapes from a small sphere-like form to a feather-like form. As a result, the adhesion of the deposited aluminum to the substrate was lowered. Smaller grain sizes and well-adhered deposits were achieved at lower temperatures. For example, deposition at 25°C resulted in the smallest crystal size of about 0.3μm under the conditions of t on =80ms, t off =20ms, and i =8mA/cm2. Furthermore, the addition of LaCl3 to the melt at 60°C effectively reduced the porosity and improved compactness of deposits. [Copyright &y& Elsevier]