Solid particle erosion studies of ceramic oxides reinforced water-based PU nanocomposite coatings for wind turbine blade protection

Wind energy has been regarded to be one of the renewable energies to rely on for the future. In tropical countries like India maintenance of wind turbine blades is a challenging task. Solid particle erosion is one of the root causes of wind turbine blade damage resulting in reduction in energy production. In the present study, in-house synthesized ceramic oxide nanoparticles such as Al2O3, ZrO2, and CeO2 are used as fillers for reinforcement of water-based polyurethane (PU) coatings on glass fibre reinforced polymer (GFRP) substrates for solid particle erosion resistance for the first time. Al2O3, ZrO2, and CeO2 nanoparticles have been prepared by solution combustion synthesis method using urea, glycine, and oxalyl dihydrazide, respectively, as fuels. These ceramic nanoparticles are found to crystallize in corundum, tetragonal, and cubic structures, respectively, as confirmed by X-ray diffraction studies. Field emission scanning electron microscopy shows the porous microstructure of the oxide products due to the release of gases in course of preparation. Transmission electron microscopy studies of these nanoparticles show corresponding lattice fringes in their high-resolution images. Observed Al–O, Zr–O, and Ce–O vibrational modes in Raman spectra confirm the formation of corresponding oxides. The oxidation states of Al, Zr, and Ce in the respective oxides are found to be +3, +4, and +4, respectively, as demonstrated by X-ray photoelectron spectroscopy. The nanocomposite coatings consisting of PU and Al2O3, ZrO2, and CeO2 nanoparticles have been developed by a simple spray method on GFRP substrates. The solid particle erosion resistance tests of coatings have been studied at varied concentrations of Al2O3, ZrO2, and CeO2 nanoparticles at impinging angles of 30° and 90°. It has been observed that ZrO2, and CeO2 nanoparticles-reinforced PU coatings show better solid particle erosion resistance compared to Al2O3-reinforced coating. Among different concentrations studied here, coatings with 15 wt% filler concentrations offer a relatively low erosion rate than the other concentrations at both impinging angles. However, GFRP substrate and PU coating are observed to show much higher erosion rate compared to nanoparticles reinforced PU coatings.