Formation and Characterization of Ceramic Nanocomposite Crystalline Coatings on Aluminium by Anodization

Abstract

Ceramic nanocomposite coatings have been synthesized on aluminium by using lithium sulphate electrolyte with zirconium silicate additive by anodization. The effects of current density (CD) on microhardness, structure, composition and surface topography of the oxide layer formed at various CDs (0.1–0.25 A/cm2) have been studied. Crystalline coatings formed at 0.25 A/cm2 have been (width 95 nm) observed with a relatively uniform distribution confirmed by scanning electron microscopy. Additionally, the average microhardness value of ceramic nanocomposite coatings fabricated from lithium sulphate–zirconium silicate bath is approximately 8.5 times higher than that of the as-received aluminium. The surface statistics of the coatings is discussed in detail to explain the roughness and related parameters for better understanding. These observations demonstrate the importance of surface statistics in controlling the morphology of the coatings and its properties. From the X-ray diffraction investigations, it can be concluded that the formed nanocomposite coatings are crystalline in nature and that the crystallinity of the coatings decreases with increasing applied current density.