NiTi Production via the FFC Cambridge Process: Refinement of Process Parameters

Abstract

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 CaCl2 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 B19′ 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 B19′ 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.

DC Voltammetry of Electro-deoxidation of Solid Oxides

“…The authors then refined their justification by relating the formation of Ti 2 Ni phase and monoclinic NiTi to the use of a Ti cathodic current collector that gave Ti enrichment. 76 That was further confirmed by using a Ni current collector in a constant potential experiment. The Ni enrichment stabilized the high temperature cubic crystal structure of NiTi down to the room temperature, and no Ti 2 Ni was observed.…”

“…The later was initially attributed to the starting material being moderately Ti-rich. The authors then refined their justification by relating the formation of Ti 2 Ni phase and monoclinic NiTi to the use of a Ti cathodic current collector that gave Ti enrichment . That was further confirmed by using a Ni current collector in a constant potential experiment.…”

“…The Ni enrichment stabilized the high temperature cubic crystal structure of NiTi down to the room temperature, and no Ti 2 Ni was observed. 76 The electrodeoxidation of TiNiO 3 under constant voltage of 3.1 V was in situ studied using X-ray synchrotron diffraction. The general reduction pathway was somehow similar to that obtained from the ex-situ analysis.…”

Direct electrochemical production of pseudo-binary Ti–Fe alloys from mixtures of synthetic rutile and iron(III) oxide

“…The process has since been shown to be capable of reducing many different metal oxides, including those of tantalum, chromium and cerium [2][3][4]. Mixed-metal oxides can also be reduced simultaneously, allowing for the direct production of alloys, as well as more novel materials like high-entropy alloys and those derived from lunar regolith simulant material [5][6][7][8][9].…”

Compatibility Issues of Yttria‐Stabilized Zirconia Solid Oxide Membrane in the Direct Electro‐Deoxidation of Metal Oxides

“…The process popularly known as the FFC Cambridge, named after the original inventors is an electrochemical process where the solid metal oxides are directly reduced to metal in a high‐temperature (950°C–1000°C) cell with molten calcium chloride as the electrolyte and graphite as the anode. This method has been demonstrated for a variety of metals namely Ti, Zr, Ta, Dy, Nb, Si, Ce, Tb, and alloys like LaNi 5 , NiTi, NdCo 5 , Al 3 Sc, FeTi, Ni‐35Ti‐15Hf, and various other mixed oxides and intermetallics . The process has even been adapted for the production of titanium on a commercial scale .…”