NiTi production via the FFC Cambridge process: Refinement of process parameters

The electrochemical FFC Cambridge process is well suited for NiTi production as it avoids the Ni segregation associated with conventional manufacturing routes. A homogeneous low oxygen product can be produced through the direct electro-deoxidation of the mixed metal oxides in a molten Formula salt bath. This work builds on previous literature concerning the reduction of NiTi [ J. Electrochem. Soc. , 155 , E171 (2008) ; Chin. Sci. Bull. , 51 , 2535 (2006) ] through the investigation of the effects of reduction temperature and the materials of construction on the phases formed. Previous work has shown that the use of a Ti cathodic current collector gave Ti enrichment, forming monoclinic Formula monoclinic NiTi at ambient temperature [ J. Electrochem. Soc. , 155 , E171 (2008) ]. The use of a Ni current collector caused Ni enrichment in the product, stabilizing the high temperature B2 cubic form at ambient temperature. This was true for all reductions carried out from 1173 to 1273 K, but for 1123 K and below, monoclinic Formula NiTi was formed. A NiTi current collector yielded Ni enrichment producing B2 cubic NiTi at ambient temperature. Mechanisms for the formation of these phases were proposed. The work also detailed the importance of good cell design and how sealing quality can dramatically affect the homogeneity of the products.