ELECTROCHEMICAL-BEHAVIOR OF FERROSILICIDES (FEXSI) IN NEUTRAL AND ALKALINE AQUEOUS-ELECTROLYTES .1. THERMODYNAMICS OF FE-SI-H2O SYSTEMS AT 298 K

The thermodynamics of Fe-Si-H2O systems are summarized in the form of Si(IV), Fe(II), and Fe(III) activity-pH, Fe(III) activity-Cl- activity, and potential-pH diagrams, calculated from standard Gibbs energies of formation of the various species considered. The semiconducting compound Fe2SiO4 was predicted to have an area of stability in the potential-pH diagram. However, the propensity of silicon to oxidize in preference to iron at low potentials leads to an area of coexistence of elemental iron and SiO2, from which Fe2SiO4 would have to be formed at higher potentials; hence, a meta-stable diagram is presented in which such iron-silicon compounds are excluded from consideration.