Influence of steel substrate roughness on morphology and mesostructure of TiO2 porous layers produced by template-assisted dip coating

Mesoporous titania films were prepared by template-assisted dip coating on 1.4301 stainless-steel substrates processed by grinding and spark erosion to different degrees of roughness. The influence of substrate roughness on the morphology and mesostructure of deposited films was studied. Textures produced by grinding with roughness Ra ranging from 0.10 to 0.78 μm did not noticeably affect the pore structure as confirmed by similar pore size and a single cubic mesophase formed on grinded steel. Grinding had a modest effect on the film integrity which manifested in fractures developed in the texture depressions. Greater roughness of the steel produced by spark erosion affected the micelle self-assembly process yielding two different mesophases on a substrate of 1.08 μm roughness, and resulting in a predominant loss of templated mesostructure on a rougher (Ra = 2.69 μm) substrate surface. Film surface area expressed as m2 BET per m2 of the substrate planar dimensions increased with substrate roughness. Higher roughness resulted in higher photocatalytic activity of crystalline films when tested in methylene blue decomposition. Given that a moderate surface texture had a negligible effect on the film mesostructure, introducing controlled substrate roughness may serve as a technique to enhance the total film surface area.