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Surface treatment of porous Ti13Nb13Zr alloy for biomedical applications

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The Ti and its alloys are considered as the best biomaterials for load-bearing applications. As the most popular Ti6Al4V alloy may be potentially harmful [1, 2], the number of another alloys have been proposed or implemented, e.g. Ti6Al7Nb, Ti29Nb13Ta4.6Zr, Ti13Nb13Zr, Ti15Mo5Zr3Al, Ti15Zr4Nb4Ta [3]. They are widely used, especially for load-carrying implants. However, in order to achieve the bioactivity, long term stability and bioactivity, new solutions are looking for. They may include: an use of scaffold/ porous structures, anticorrosion and nanooxidation, deposition of hydroxyapatite coatings with immersion techniques. The scaffold metallic materials possessing open porous structure are recently used to enhance bioactivity, i.e. the tissue in-growth rate and long term stability are considered. The pore size of 30÷400 μm seems the most plausible [4]. The greater pore size enhances the faster tissue growth, the smaller - better adhesion strength. Porous structures in a bulk or within the surface layer can be obtained by various methods: powder metallurgy (P/M) with or without space holders, rapid prototyping with an use of selective laser melting (SLM) or electron beam melting (EBM), plasma spraying etc. [5]. Corrosion rate of Ti measured may be substantial [6]; in electrochemical and gravimetric tests changes in simulated body fluids (SBF) between 0.01 and 0.1 μg/cm2·day, and after 48 weeks of an exposure of the Ti6Al4V alloy implant only traces of Ti, Al i V can be found in body tissues [7]. At low pH corrosion increases: in lactic and formic acids general corrosion occurs already after 3 weeks [8]. Ti alloys degrade in presence of chlorides saline and artificial saliva [9] and in phosphate buffered saline (PBS) [10]. Increase in roughness [11], increase in temperature, low pH and wear conditions increase corrosion rate of Ti alloys [6]. Improvement of corrosion resistance and bioactivity of titanium and it[...]

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