THERMAL STABILITY OF RARE EARTH OXIDE COATED SUPERHYDROPHOBIC MICROSTRUCTURED METALLIC SURFACES

摘要

In this paper, we present a method of generating nearly superhydrophobic surfaces from Femtosecond Laser Surface Processed (FLSP) metallic substrates and the study of their thermal stability at high temperatures. Using an FLSP process, hierarchical microano structures were fabricated on stainless steel 316 after which a 200 nm Cerium Oxide (CeO_2) film was sputtered onto the surface. Before CeO_2 deposition, the contact angle of sample was measured. Post CeO_2 deposition, the contact angles were measured again. As a result of the cerium oxide deposition, the contact angle of the originally hydrophilic FLSP surface turned near superhydrophobic with an equilibrium contact angle of approximately 140°. Subsequently, the coated surfaces were annealed in air. The surface maintained its high contact angle from room temperature to about 160℃, after which it lost its hydrophobicity due to hydrocarbon burn off. For each annealing temperature, we monitored the chemical composition for the cerium oxide-coated FLSP surface using energy dispersive x-ray spectroscopy (EDS) and X-ray diffraction (XRD). Under a nitrogen rich annealing environment, the nearly superhydrophobic FLSP metallic surface maintained its high contact angle up to temperatures as high as 350℃. To further understand the physics behind the observed phenomenon, we investigated two additional samples of polished stainless steel 310 again coated with 200 nm of CeO_2.