Surface modification of a low-modulus Ti–7.5Mo alloy treated with aqueous NaOH

Abstract

A new α″ phase Ti–7.5Mo alloy with a lower elastic modulus had been developed for biomedical applications. This Ti–7.5Mo alloy also exhibits an even better strength/modulus combination and excellent corrosion resistance. However, titanium alloys doesn't bond directly to living bone. In the present study, bioactive coatings on commercially pure titanium (c.p. Ti) and Ti–7.5Mo were prepared by a simple chemical technique. Specimens of c.p. Ti and Ti–7.5Mo were initially immersed in a 5, 10 or 15 M NaOH solution at 60 °C for 24 h, resulting in the formation of a porous network structure composed of sodium titanate (Na 2Ti 5O 11). X-ray diffraction (XRD) results indicated that the intensity of the sodium titanate peak increased with an increasing NaOH concentration. The specimens were then immersed in simulated body fluid (SBF) at 37 °C for 3, 7 and 28 days, respectively. The apatite-forming ability of alkali-treated Ti–7.5Mo was higher than that of alkali-treated c.p. Ti on exposure to 5, 10 or 15 M NaOH aqueous solutions. The XRD results also indicated that the deposited amounts of calcium phosphate were much greater for alkali-treated Ti–7.5Mo than for alkali-treated c.p. Ti. The average thickness of calcium phosphate layer of 15 M NaOH-treated Ti–7.5Mo after immersion in SBF for 28 days was about 15 μm. The alkali treatment of Ti–7.5Mo by NaOH aqueous solutions can be anticipated to be promising artificial bone substitutes or other hard tissue replacement materials for heavy load-bearing applications due to their wonderful combination of bioactivity, low elastic modulus and low processing costs.