Preparation of superhydrophilic alumina films by hydrothermal processes using an organophosphorous compound

Superhydrophilic alumina films were successfully fabricated by a hydrothermal reaction of nanofibrous alumina films in a nitrilotris(methylenephosphonic acid) (NMP) aqueous solution at 180°C for 6 h. The films showed superhydrophilicity not only as prepared but also after a boiling water resistance test, indicating that they had good durability. The alumina films were phosphorylated wholly in a hydrothermal condition only at 180°C for 6 h. Phosphate moieties were present both at the surface and inside the films and a micro-structure with a serrated morphology was observed over the entire film surface. Whole phosphorylation of the alumina films resulted in good durability in the boiling water resistance test. Other films were phosphorylated partially at 160°C for 6 h and at 180°C for 4 h. The micro-structure with a serrated morphology was observed partially at the film surface. This morphology corresponded to the degree of phosphorylation. These results indicate that the phosphate moieties present on and in the films and the micro-structure of the films produced superhydrophilicity.