Hydrophobic Properties of Al2O3 Doped with Rare-Earth Metals: Ab Initio Modeling Studies

Polymer-based hydrophobic coatings degrade in response to high temperatures or abrasion. Rare-earth oxides (REOs) as a ceramic material may provide more robust surfaces whose hydrophobicity is maintained due to their specific electron configuration. It has been also shown that REO thin films are stable on the surface of bare materials used in the aerospace industry (i.e., aluminum and titanium alloys). Hence, coating or doping of Al2O3 and TiO2 surfaces with REO might be promising both theoretically and practically. Following our previous studies on cerium-doped Al2O3 and TiO2, in this work, the density functional theory (DFT) method is applied to investigate the possibility of tuning the wettability of commonly used hydrophilic Al2O3 by surface doping with neodymium (Nd) and europium (Eu). The results indicate that Nd and Eu segregate to the (0001) surface of Al2O3 and thermodynamically stable oxygen termination of dopant is formed. A significant increase in the static water contact angle provide a valuable opportunity for the RE element surface modification of Al2O3, in order to achieve hydrophobicity.