Nanoporous Surface Modification Via Electrochemical Anodization And Properties Of Titanium And Its Alloys

Titanium and its alloys have been extensively used as implant materials owing to their excellent mechanical properties, adequate corrosion resistance and incredible biocompatibility. However, their implants still confronted with two major issues during long term service span:prostheses loosening because of mismatch of elastic modulus between implants and surrounding bony tissues, and inflection after implantation. Numerous efforts have been made consequently to overcome these problems, among which surface modification and the employment of the low elastic modulus ?-type titanium alloys are two efficient approaches. In present study, electrochemical anodization was utilized to modify the titanium and its alloys surface with an interconnected three-dimensional (3D) oxide layer. Additionally, a composite coating containing nanoscaled-silver/octacalcium phosphate was also constructed progressively on the oxide layer. Surface morphology, phase composition and elemental composition of the modified surface and coating were investigated. Mechanisms of the surface layer formation were also discussed. Particularly, biactivity of modified materials were evaluated in vitro. In addition, in order to obtain low elastic tatinium alloys implants. TiNb alloys was selected and further modified with a layer of nanotubular arrays. The effects of the Nb content on the formation of nanotubular arrays, and the structure and properties of the oxide layer were also systematically studied and characterized.There are three major parts in this dissertation, including:(1) An anodic TiO2 layer with interconnected 3D nanoporous structure on Ti implant was fabricatied via gavalnostatic mode in a fluoride-containing electrolyte. Geometry of the pores can be controlled by varying the stimulated current density, oxidation time and the water content of the electrolyte. The pore sizes ranged from 30 to 200 nm. Compared to the TiO2 nanotubular layers,3D oxide layers possess enhanced mechanical properties, higher adhesion strength and corrosion resistance. Moreover, the titanium modified with 3D structural oxide layers also showed good performance in the osteogenic cell culturing and revealed the potential applications in biomedical applications(2) A composite coating of nano-silver/octacalcium phosphate (OCP) was further constructed on the 3D porous TiO2 layers. The silver with controlled content distributed uniformly in the coating. By coating the nano-silver/OCP, the surface roughness of the material increased and performed superhydrophilic. Additionally, results incidated that the coating not only can realize sustained release of silver, but also exhibited excellent antibacterial properties on Escherichia coli and Staphylococcus aureus. The antibacterial efficiency even reached to 93% and 87% for these two cases, respectively.(3) Nanotube arrays on Ti-xNb alloys (x= 5?40 wt%) were prepared by anodic oxidation. Influence factors, such as Nb content, driving voltage on the structure of nanotube arrays were systematically studied. Results showed that the content of the Nb element has little effect on the morphology of the nanotubular arrays. The TiNb alloys became more hydrophilic after modified with anodized nanotubular surface. And the contact angles of surfaces were decreased with the increased applied potential, which may relate to the varied in nanotube sizes. Further annealing would reduce the hydrophilic of the surface due to the removal of hydrophilic group.