Adhesion of sol-gel derived zirconia nano-coatings on surface treated titanium

Abstract

The morphology, adhesion and tribological properties of the zirconia sol-gel coatings on phosphate treated, anodized and un-treated titanium surfaces were investigated. The anodization of titanium involves the formation of a thin, compact, oxide layer, which improves the wettability for further coating. This process involves the conversion of the rutile structure of the original titanium oxide into a mostly crystalline anatase structure. The samples were anodized in sulphuric and phosphoric acid at varying concentrations. The samples were anodized at differing currents and differing time periods ranging from 10 to 30 minutes, Phosphate adsorption treatment involves soaking samples in 10% H3P04 solution for 10 minutes. These samples were spin coated with zirconia, yielding 100 nm thick films. The nanocoatings were prepared by alkoxide sol-gel chemistry, using techniques and protocols developed in an earlier work and were examined with x-ray diffraction, and scanning electron microscopy. Interfacial and adhesion properties were measured using a micromechanical tensile test. The tribological properties were investigated using an Orthopod machine, with commercial grade ultrahigh molecular weight polyethylene (UHMWPE) pins (3/8 inch diameter) that can articulate in number of different combinations against opposing coated and control specimens. The UHMWPE pins were used in a bovine serum environment. The amount of the wear was measured gravimetrically and wear features were observed using SEM.