WETTABILITY OF TRANSITION-METAL OXIDE SURFACES

The wettability of transition metal oxide surfaces (TiO2, ZrO2 and HfO 2) by water was investigated by measuring the contact angles using the sessile drop method. The oxide surfaces were prepared by thermal oxid ation of polished metal foils of Ti, Zr and I-If which had been polish ed to different levels of surface roughness. The surfaces were also ch aracterized by optical microscopy, X-ray diffraction (XRD), atomic for ce microscopy (AFM) and Auger/XPS (AES/ESCA) methods. From the depende nce of contact angles on surface roughness for the three investigated oxides, contact angles on Bat surfaces win calculated as 70.7 degrees, 59.9 degrees and 74.0 degrees for TiO2, ZrO2 and HfO2, respectively. These results suggest thar the three oxides do nor provide acceptable waterproofing coatings on silica fibers used for space shuttle thermal insulation. (C) 1998 Elsevier Science S.A.