Effect of heating rate on asperities pattern formed in sol-gel derived nanocomposite hydrophobic coatings

Sol-gel based nanocomposite hydrophobic coating was applied on soda lime glass surface and cured at different heating rates, soaking temperatures and durations of time. Near infra-red radiation and conventional thermal curing methods were employed to densify the coatings. Effect of heating rate on hydrophobic behavior of all the coatings was studied by evaluating the water contact angle, microstructure and surface topography. Hierarchical micro-nano patterns formed on the coating were analyzed with the help of Field Emission Scanning Electron Microscopy and Atomic Force Microscopy. Conventional curing and near infra-red radiation curing methods were comparatively evaluated with respect to presence of asperities as a function of heating rate and soaking time. Both near infra-red radiation and conventional thermal cured coatings exhibited hydrophobicity, with thermal cured coatings exhibiting slightly improved hydrophobicity due to difference in the hierarchical micro-nano structure. The difference in the evolution of surface topography obtained with the different curing techniques could be explained due to the difference in heating rates achievable in conventional thermal and near infrared curing methods. Graphical abstract Highlights Sol-gel hydrophobic coatings cured with thermal and NIR radiation at different heating rates. Curing temperature and soaking times varied as process parameters. Water contact angle, surface morphology and topography studied for all samples. Heating rate was found to affect solvent evaporation rate which gave different asperities. Different asperities pattern obtained affected hydrophobicity.