Graded surface structure in chemically polished NiTi shape memory alloy after NaOH treatment

A bioactive sodium titanate film (Na2TiO3) with a trait of Ni2O3 formed on the chemically polished NiTi substrate by the direct reaction of the NiTi phase with NaOH solution. Depth profiles of O, Ni, Ti and Na show the porous sodium titanate film possesses a smooth graded interface structure to the NiTi substrate.