Effects of electrolyte composition on the process of conversion of aluminium foil in to alumina ceramics by plasma electrolytic oxidation

Abstract EN

Alumina thick and thin films can be used for a variety of purposes, including the semiconductors, electronics, substrate and dielectric, piezoelectric and ferromagnetic devices.

The films can be produced by conventional methods such as tape casting and roll compaction from ceramic slurry.

However, these methods offer limited part geometries and cause defects in the film structure.

Plasma electrolytic oxidation is a novel surface engineering technology, allowing relatively thin and thick oxide coatings to be formed on metals.

Alumina ceramics were produced by conversion of a rectangular shape aluminium foil (30 x 15 x 0.05 mm) using a plasma electrolytic oxidation technique.

To achieve better understanding of the coating formation on the foil substrates the plasma electrolytic oxidation (PEO) process was carried out for 6 minutes in electrolytes containing various proportions of alkali, silicate and phosphate salts.

The influence of the electrolyte constituents on the coating thickness, morphology of the process conversion of aluminium foil in to alumina ceramics to obtain alumina ceramics with a moderate degree of flexibility were studied.

Preliminary results indicate that the thickest coating corresponding to conversion of about 70% of Al foil to alumina ceramics, with residual aluminium foil thickness of around 20 ^m, has been achieved in electrolyte (1.25 g/l KOH, 2.0 g/l Na4P2O7, 2.0 g/l Na2SiO3).

The increase of potassium hydroxide concentration leads the discharge phenomena to occur at lower voltages.

Moreover, the addition of silicate in the electrolyte can increase the activity of discharge as well as coating surface roughness.