Pourbaix-Ellingham diagrams

The minimum temperature necessary for the formation of the metal under a particular reduction pressure is that temperature at which the corresponding carbon monoxide pressure line intersects the Nb2C-NbO-Nb equilibrium line in the Pourbaix-Ellingham diagram. 

The Pourbaix-Ellingham diagram of the tantalum-carbon-oxygen (Ta-C-O) system indicates fewer sequential steps between the oxide and the metal as compared to the niobium-carbon-oxygen system ... 

The changing water properties, combined with the high temperatures and pressure and the intense radiation field, result in an extreme in-core environment [20] that must be understood in order to advance materials development. For example, the changes in water properties are reflected in changes in corrosion mechanism (Section 4.3) while Pourbaix diagrams are useful constructs at temperatures around Pc, Ellingham diagrams are more appropriate at P Pc [21]. 

Figure 6-15. Superimposed Ellingham-Pourbaix diagrams for the Fe-O-S and Al-O-S systems drawn for 600 and 700 °C and 1 atm total pressure (Gesmundo et al., 1994).

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