title: Controlled surface modification of Ti-40Nb implant alloy by electrochemically assisted inductively coupled RF plasma oxidation.
abstract: Low temperature metal oxidation induced by plasma in the absence of liquid electrolytes can be useful for the surface preparation of orthopedic devices since residues from these may be harmful and need to be removed before implantation. In this study the oxidation of Ti-40Nb for biomedical application was achieved by employing an inductively coupled radio frequency oxygen plasma. The correlation between the growth mode of the surface oxide and the electric conductivity ratio of the plasma and the oxide phase were studied by varying the sample temperature, oxygen gas pressure and additional bias potential. The plasma treated samples were characterised by confocal laser microscopy, SEM, EBSD, XPS, TEM and ToF-SIMS. The surface energy was determined by contact angle measurements using the Owens-Wendt-Rabel-Kaelble method. Well adhering oxide layers consisting of TiO2 and Nb2O5 with thicknesses between 50 and 150 nm were obtained. Surface roughness values and microstructure indicate that the growth mode of the oxide can be well controlled by the sample temperature and oxygen gas pressure. At temperatures above 450°C a migration of Ti ions towards the surface controls the growth process. A bias potential higher than +50 V causes rough and defective surfaces with high surface energies.
authors.affiliation: Institute for Physical Chemistry, Justus-Liebig-University of Giessen, Heinrich-Buff-Ring 58, 35392 Giessen, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Göttlicher
authors.forename: Marcus
authors.initials: M
authors.lastname: Rohnke
authors.forename: Arne
authors.initials: A
authors.lastname: Helth
authors.forename: Thomas
authors.initials: T
authors.lastname: Leichtweiß
authors.forename: Thomas
authors.initials: T
authors.lastname: Gemming
authors.forename: Annett
authors.initials: A
authors.lastname: Gebert
authors.forename: Jürgen
authors.initials: J
authors.lastname: Eckert
authors.forename: Jürgen
authors.initials: J
authors.lastname: Janek
mesh_terms: D000497:Alloys / Q000737:chemistry*; D003460:Crystallization; D055664:Electrochemical Techniques / Q000379:methods*; D020007:Implants, Experimental; D008855:Microscopy, Electron, Scanning; D061848:Optical Imaging; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry; D056951:Photoelectron Spectroscopy; D058626:Plasma Gases / Q000737:chemistry*; D011846:Radio Waves; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D000497:Alloys; D010087:Oxides; D058626:Plasma Gases; C583184:Ti-40Nb alloy
keywords: Anodic plasma oxidation; Low temperature radio frequency discharge; Metallic implants; Surface modification; Ti alloy