Electrochemical behaviour of the alloy Ti60Ni40 after ion beam irradiation

Abstract

Electrochemical studies were performed using a potentiodynamic polarisation method and weight loss method on the irradiated and unirradiated specimens of the alloy Ti60Ni40 in 1 M HNO3 aqueous medium. The irradiation was carried out using Ni11+ 150 MeV ions at a fluence of 1×1013 ions/cm2. The X-ray diffraction pattern depicts that the alloy Ti60Ni40 was amorphous in nature before irradiation and that after irradiation a nanocrystalline Ti2Ni phase evolves. Polarisation results revealed that the irradiated specimen exhibits less corrosion current density when compared with the unirradiated specimen of the alloy Ti60Ni40. Weight loss data also corroborate the polarisation results. X-ray photoelectron spectroscopy (XPS) studies were also performed in order to establish the nature of the oxide film formed after the corrosion test. The Ti 2p XPS spectra revealed the presence of Ti2+, Ti3+ and Ti4+ species in the unirradiated specimen, whereas the irradiated specimen contained only Ti2+ and Ti4+. Scanning electron micrographs show that the oxide film formed on the irradiated specimen is more homogeneous compared to the unirradiated specimen of the alloy Ti60Ni40. Hence, the evolution of the nanocrystalline Ti2Ni phase and the absence of Ti3+ species in the oxide film formed on the irradiated specimen result in its superior corrosion resistance when compared with the unirradiated specimen of the alloy Ti60Ni40.