Characterization of Spark-Anodized Titanium for Biomedical Applications

The local compositions, structures, and morphologies of titania-based coatings formed by spark anodizing of titanium have been investigated using analytical scanning and transmission electron microscopies. The coatings were formed at 20, 40, or in orthophosphate and pyrophosphate electrolytes at , which are relevant to development of osseointegrated implants. According to X-ray diffraction, anatase and rutile are the main crystalline phases in the coatings, with amorphous material also being present, as confirmed by transmission electron microscopy. The amorphous phase is more extensive for formation in the pyrophosphate electrolyte than in the orthophosphate electrolyte and contains high levels of phosphorus species relative to that in adjacent nanocrystalline regions. Porosity, extending from craters at the coating surface to the vicinity of the metal/coating interface, is revealed in coating taper sections. Finer, submicrometer porosity is also found in some coating regions. Locations of silicon tracer species indicate destruction of coating material at breakdown sites followed by regrowth of material at the damaged regions.