Surface Modification To Develop Hierarchical Micro/Nano Topography On Titanium Based Medical Implants

Self-organized nanostructured TiO2 layers were developed on micro rough planar, cylindrical, and threaded surfaces of Ti6Al4V alloy by electrochemical anodization (EA) performed in phosphate-fluoride solution (1M H3PO4 with different HF additions) by using different process parameters (electrolyte concentration, anodization potential U, potential ramp U-r, and sample rotational speed n). Optical microscopy and scanning electron microscopy (SEM) was used to evaluate the morphology of the oxide layers. Nanostructured oxide layers with nanotubes/nanopores internal diameter in 25-110 nm range were developed on surfaces with an initial micro rough topography (R-a = 0.5-2 mu m, resulting by CNC turning or by sand blasting and acid etching - SLA). On planar surfaces, the optimal EA process parameters in our custom-built anodization cell are: 0.5 wt.% HF addition in electrolyte, U = 20 V, and U-r = 0.1 V/s - for turned surfaces, and 0.4 wt.% HF addition in electrolyte, U = 24 V, and U-r = 0.08 V/s - for SLA surfaces. For cylindrical surfaces the nanotubes were superimposed on micro rough surface by using 0.4 wt.% HF addition in electrolyte, U = 24 V, and U-r = 0.08 V/s. On threaded surfaces continuous nanoporous oxide layer covering all geometrical features - frontal apex, spiral channels, major diameter, minor diameter, thread flanks - was developed by using 0.4 wt.% HF addition in electrolyte, U = 24 V, U-r = 0.08 V/s, and n = 8 rev/min.