Nanostructured titanium for medical devices

Abstract

The bulk and surface properties of pure titanium can be enhanced by nanostructuring to create a new generation of metals for medical implants. The healing response of bone to nanostructured titanium implants can be accelerated 20-fold by altering the metal's crystal size and grain boundary density. In addition, the strength of nanostructured titanium compared to conventional titanium can be increased between 30% to 100%. To incorporate these benefits into medical implants such as spinal rod or dental implants, nanostructuring must be applied to long rods or bars of titanium. One method of nanostructuring titanium is to subject long rods to high shear deformation. However, while this deformation creates nanoscale grains, it also imparts some residual stresses, which must be removed by annealing. In my research, we evaluated the annealing response of nanostructured titanium. Bars of pure titanium nanostructured by High Shear Deformation (HSD) were subjected to 1 hour annealing treatments between 200°C and 375°C. We evaluated the annealing response by measuring the microhardness. We confirmed the unusual phenomenon of "annealing hardening" that is unique to nanostructured metals. Generally, annealing reduces the hardness and strength of pure metals. But in the case of nanostructured titanium annealing can increase the strength. We were able to determine an optimum annealing temperature of 275°C.