Scale-Phobic Surfaces Made of Rare Earth Oxide Ceramics

Scaling or precipitation fouling involves crystallization of hard and chalky solid salts from a solution. Scaling results in significant production and energy losses and is a major concern in many industries. Here we investigate the scale-phobicity of rare earth oxide (REO) ceramics (particularly CeO₂, Gd₂O₃, and Er₂O₃) in comparison with glass and stain-less steel. We quantify the surface energy and its polar and apolar components for these materials using the Van Oss-Chaudhury-Good approach and show a direct correlation between surface energy and scale deposition. We also show that the polar component of surface energy is the main contributor to scale deposition; hence, REOs with minimal polar component represent high barrier to scale deposition. Moreover, we study the weight gain due to calcium sulfate dihydrate (gypsum) scale accumulation on these materials and show 55% and 77% reduction on REOs in comparison with bare glass and stainless-steel, respectively. We also evaluate the adhesion forces between salt and test materials using atomic force microscopy with a gypsum microparticle adhered onto a tipless cantilever. We show adhesion force between salt particles and REO surfaces is about half that of bare glass and stainless-steel because of the lower surface energy and polar component. We expect REO ceramics would find widespread applicability as robust scale-phobic surfaces in various industries.