Synthesis and bioactivity of porous Ti alloy prepared by foaming with TiH2

A novel porous Ti–6Al–4V with an open cell structure was fabricated by powder metallurgy process with the addition of TiH2 as the pore forming and active agent. Control of porosity of porous Ti alloy made it possible to obtain the porous Ti with the Youngʹs modulus value of 5.8–9.5 GPa, which was similar to that of human cancellous bone. This kind of porous Ti alloy with good biomechanical properties is potential to alleviate the problem of mechanical mismatch between the bone and the Ti implant. The porous Ti alloy prepared by the addition of TiH2 as foaming agent had a uniform distribution of pores with pore size of 90–190 μm and porosity of 43–59%. In order to improve the biological properties, the duplex titania/apatite coatings were applied onto the surface of porous Ti alloy. The titania coating was deposited by chemical treatment and the apatite coating was subsequently applied by immersing the samples in a simulated body fluid. Results showed that a homogeneous nanocrystallite titania coating with a thickness of 0.8 μm was formed on the surface of the Ti alloy after chemical treatment. The carbonate-containing apatite coating with a thickness of 1 μm was deposited on the surface of titania coating after immersion in simulated body fluid for 7 days. The nucleation of the carbonate-containing apatite can be induced from the electrostatic interaction between the OH-containing groups on the surface of titania coating and the calcium and phosphate ions in the metastable simulated body fluid on those specific superficial sites. The growth kinetics of the coatings was also discussed. Cell culture test showed the well stretched and proliferated cells on the surface of the sample, indicating the good biocompatibility of porous Ti alloy.