All oxide sol-gel assisted SiO<inf>2</inf>/(ZnO/Sn-In<inf>2</inf>O<inf>3</inf>)<inf>n</inf>/SS dielectric/conducting multilayer based spectrally selective coating on Stainless Steel tubes for potential solar thermal application

SiO2/(ZnO/Sn-In2O3)n=4/SS multilayer structure as a spectrally selective coating (SSC) is developed using a low-cost sol-gel assisted dip-coating process on stainless steel based planer and tube samples. The X-ray diffraction and atomic force microscopic measurements are carried out to understand the development of structural and microstructural features on the developed coating structures. The optical measurements are carried out using Ultraviolet–visible spectroscopy (UV–Vis) and Fourier transform infrared (FTIR) spectrometers, and the observed absorptance and emittance values are ∼0.85 and 0.14 for the developed coating structures. These coatings showed enhanced thermal stability up to 350 °C in open-air conditions and enhanced corrosion resistance against saline conditions, i.e., 3.5% by weight in water solution. The coating process is extended on a foot-long stainless steel (SS) tube having a one-inch diameter to demonstrate the feasibility of the developed technique. Thus, the developed process showed potential for large-scale, low-cost coating with desired optical properties for solar thermal applications.