Control of the hydrophobicity of rare earth oxide coatings deposited by solution precursor plasma spray by hydrocarbon adsorption

【摘要】：The basis of the hydrophobicity of lanthanide rare earth oxides(REOs) has been the subject of considerable debate.To explore this question,the wetting behaviors and surface compositions of hierarchicallystructured Yb_2O_3(one of the REOs) coatings and non-REO Al_2O_3 coatings deposited via solution precursor plasma spray process were investigated in this work.The Yb_2O_3 coatings were subjected to a number of post-deposition treatments including vacuum(1-15 Pa) treatment,Ar-plasma treatment,heat treatment(400℃),long-time air exposure and ultra-high vacuum(1×10~(-7) Pa) treatment.Subsequent characterization showed that different post-deposition treatments resulted in different wetting behavior for the Yb_2O_3 coatings which correlated with the content of hydrocarbon on the surface.Yb_2O_3 coatings exhibited reversible transitions between superhydrophobicity after vacuum treatment and superhydrophilicity after Ar-plasma or heat treatment,linked to hydrocarbon adsorption onto and desorption from the surface.Yb_2O_3 coatings after long-time air exposure and ultra-high vacuum treatment both remained hydrophilic and showed a smaller hydrocarbon content than coatings after vacuum treatment.Al_2O_3 coatings with hierarchical surface structures similar to the Yb_2O_3 coatings showed an increase in WCA to only-170 after the same vacuum treatment,indicating the REO has a much higher affinity for hydrocarbon adsorption than Al_2O_3,and that the content of hydrocarbon adsorbed on the surface of the REO determined the wetting behavior.