Characterization of Si<SUB>3</SUB>N<SUB>4</SUB>/TiO<SUB>2</SUB> Nanocomposite Coatings Prepared via Micro Arc Oxidation

Abstract

Nanocomposite Si3N4/TiO2 coatings were prepared by micro arc oxidation with Si3N4 nanoparticles in solution and the effects of time and current density on the coatings formation and growth were studied. X-ray diffraction analysis was utilized to detect the nanocrystalline and amorphous characteristics of the composite coatings. Surface morphology and nanostructure of coatings were observed by scanning electron microscopy and atomic force microscopy. The results showed that current density had great effects on phase transformation of Si3N4 nanoparticles in composite coatings. The moderate current density conduced to homogeneous distribution of silicon nitride nanoparticles in the coatings. Moreover, fine nanoparticles that entered and homogeneously distributed in the composite coating led to an increase in the barriers for nucleation of oxide-based grains and inhibition of grain growth. Therefore, the introduction of nanoparticles resulted in the formation of smaller oxide-based grains.