Chapter 11 - Invention and fundamentals of the FFC Cambridge Process

Abstract

The original patent of the Fray-Farthing-Chen (FFC) Cambridge process was published in 1999, whilst the past 2decades have witnessed significant progresses in many aspects, including commercialisation and laboratory demonstrations of expected and unexpected materials with technological potentials. Whilst the authors and their research teams have continuously undertaken promising research and development, international colleagues in the molten salts chemistry, materials science and metallurgy, and other related fields are making various valuable and, often, surprising contributions to the development of the FFC Cambridge Process in terms of both fundamental understanding and technological advancements. This chapter aims to briefly introduce the background of the invention of the FFC Cambridge Process, and to review selectively the progress, focusing on fundamental hypotheses, experimental verifications, and those expected and unexpected experimental findings, particularly those having potential applications. To be in line with the rest of the chapters of this book, the discussion flows with studies on making titanium and its alloys by electro-deoxidation of titanium and other metal oxides individually and their mixtures in CaCl2 based molten salts. The procedures and mechanisms of metal oxide reduction on the cathode are reviewed in details, covering analysis and confirmation of (1) the steps responsible for the formation of various intermediate products, perovskites in particular, (2) the electron and ion transfer at the metal oxide/metal/molten salt three phase interlines (boundaries) that propagate from the surface into the center of the metal oxide precursor on the cathode, and (3) the impact of the molar volume ratio of metal to metal oxide on electro-deoxidation. The opportunity to fullfil the ambition of producing only the metals and oxygen gas in the FFC Cambridge Process has been assessed against several ceramic materials for making an effective and stable inert anode or an oxygen ion conducting solid membrane, typically yttrium stabilised zirconia. The research progresses in electro-deoxidation of other metal oxides individually or as a mixture are also highlighted, particularly for making functional metals and alloys that find uses in for example superconductors, high strain ferromagnets, hydrogen storage alloy powders and medical implants. A special attention is given to the potentially cleaner, faster and more efficient use of the FFC Cambridge Process to extract metals from their natural or synthetic sulfides in molten chloride salts with or without CaCl2. Ending with the surprising findings in using the principle of electro-deoxidation for cathodic protection and welding of titanium and its alloys, the authors hope this chapter has laid the foundation for better understanding the FFC Cambridge process, and more importantly further innovative leaps in the near future.