Nanostructure Formation in Anodic Films Prepared on a β Alloy Ti39Nb PVD Layer

Ti alloys are widely used for construction of bone implants. Some of them can be prepared without any toxic elements containing only Nb, Zr and Ta. At suitable composition they have the beta (BCC) structure with low modulus of elasticity and high corrosion resistance. The oxidation of their surface can increase the biocompatibility and enable the preparation of nanostructured surface morphology. The β-alloy Ti39wt.%Nb alloy was melted eight times by electric discharge, annealed at 850°C for 30 minutes and quenched to water. The substrates of the TiNb layers were prepared from bulk Ti39Nb and commercial cpTi and Ti6Al4V. They were cut using a SiC cutting wheel, ground with abrasive papers and then polished with a suspension of colloidal SiC. The TiNb layers were prepared by cathodic sputtering in a Hauser Flexicoat 850 unit. The thickness of the TiNb layer was measured by Calotest. Surface roughness was measured by a Hommel T1000 Basic roughness tester. The sample surface was observed by a JSM7600F scanning electron microscope. Samples were anodically oxidized in (NH4)2SO4 + 0,5wt%NH4F electrolyte at DC voltages 10, 20 and 30 V using a stabilized voltage source. The morphology of the nanostructured surface of a PVD layer depends particularly on the oxidation voltage and time, but also on the type of substrate. The surface morphology containing nanotubes appeared only on TiNb layer with a TiAlV substrate prepared at certain oxidation voltage and time. The morphology of oxidized layers is heavily influenced by substrate material even though the surface roughness of PVD layer and substrate is identical for all oxidation processes. TiNb alloy have very suitable properties for bioapplications and the study of surface properties contribute to the practical use of this material.