Structural and morphological characterization of anatase TiO2 coating on χ-Alumina scale fiber fabricated by sol–gel dip-coating method

Abstract

Anatase TiO2 coatings 0.4μm thick have been successfully fabricated by sol–gel dip-coating process on χ-Al2O3 fibers 100μm by 10cm long with a surface fish-scale. This was achieved by adjustment of the sol–gel parameters such as molar ratio of the precursors in TiO2-sols, dip-coating time, drying duration in air, heating processes and number of cyclical repetitions of the process. Two samples were prepared using two sols containing different molar ratios of precursors. XRD, TEM, EDS and SEM characterization confirmed: (1) the similarity of the growth of anatase-TiO2 from two sols under the optimal sol–gel parameters, (2) that the coatings are composed of aggregated crystallites of 10–25nm in diameter, (3) the good compositional uniformity of Ti in the fabricated anatase-TiO2 crystallites, (4) a surface covering ratio of anatase-TiO2 around the fiber of at least 90%, and (5) that there is a good adherence of the fabricated anatase-TiO2 layer on alumina fiber as evidenced by the lack of cracking and peeling off traces around the boundary between the coating and the fiber.