Study on wettability of plasma spray coated oxide ceramic for hydrophobicity

Abstract

Many industrial applications require hydrophobic surfaces with high-temperature compatibility. Ceramic surfaces, which have excellent endurance for high-temperature, are generally hydrophilic. For such applications, the required hydrophobicity is induced in ceramic surfaces with suitable polymeric agents by using different surface grafting techniques. To avoid the costly grafting process, suitable hydrophobic ceramic surfaces have to be designed for direct use in such applications. Rare earth oxides show hydrophobicity due to their electronic configurations. Hence, for the selection of hydrophobic ceramic material for real engineering components, three plasma spray-coated surfaces have been characterized for their water contact angle. In this study, yttria (Y2O3) was used as a rare earth oxide along with yttria stabilized zirconia (YSZ) and alumina (Al2O3) for comparison of surface properties. The dependence of contact angle on various experimental parameters was established. It was observed that cleaning with water induces temporary hydrophobicity in alumina even after baking at 180 °C. Yttria coating was found to be distinctly hydrophobic with the contact angle more than 115°. The hydrophobic behaviour of yttria was found to be permanent and does not degrade with environmental exposure. The apparent surface energies of the samples were estimated based on acid-base theory. The apparent surface energies of the studied samples were found to be in the range of 35 mJ/m2 to 42 mJ/m2. © 2020 Elsevier B.V.