Production of NiTi shape memory alloys via electro-deoxidation utilizing an inert anode

NiTi shape memory alloys (SMA) with equiatomic composition of Ni and Ti were prepared by electro-deoxidation, in molten calcium chloride, at 950 °C. Constant voltage electro-deoxidation was conducted using a NiTiO3 cathode, and either a carbon anode or a novel CaRuO3/CaTiO3 composite inert anode. Both anode materials successfully allowed NiTi shape memory alloy to be obtained. The primary difference is that molecular oxygen was produced on the inert anode, instead of environmentally undesired CO2 greenhouse gases on the carbon anode. Indeed, it was found that carbon could successfully be substituted with conductive calcium titanate–calcium ruthenate composites for electro-deoxidation. Furthermore, DSC was used to analyze the phase transformation of NiTi shape memory alloys, with results revealing the existence of reversible martensite–austenite phase transformations during the cooling and heating process.