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

Anatase TiO₂ coatings 0.4 μm thick have been successfully fabricated by sol-gel dip-coating process on χ-Al₂O₃ fibers 100 μm by 10 cm 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 10-25 nm 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.