Atom ingress from synthetic body fluid into nanoporous layers formed in titanium by helium ion-implantation

Helium ion-implantation can be used to form a buried layer of nanoscale cavities in Ti. This offers the potential for diffusing dopant atoms of interest for biomedical applications, into a Ti surface. Disc specimens were taken from a He-implanted foil and a small spot in the centre was eroded to a different depth on each disc before treatment with synthetic biological fluid. IBA techniques (including RBS, NRA and PIXE) were used to determine the uptake of specific elements in two regions: the central eroded spot and the outer (un-eroded) region. The most significant effect was for oxygen. A small amount of prior erosion resulted in a threefold increase in the oxygen in both regions. Whereas, greater erosion caused a rapid reduction in the uptake in the centre, the strong enhancement in the outer region remained a striking feature. This provides convincing evidence that oxygen can move laterally over large distances through the nanoporous layer.