Lower oxides stable phases

Closer examination of Fig. 7.84 shows that each of the non-stoichiometric oxides has a region of homogeneity over which the compound is the sole stable phase. It has been observed, from a number of gas-metal systems, that the lower oxides (here MjO and MO ) usually show a wider region of non-stoichiometric behaviour than the higher oxides (here MO2). 

Under mild reduction conditions B cations with stable lower oxidation states may lead to the formation of other mixed oxide phases. Increasing the reduction severity usually leads to a full reduction of the B cation to the metal state. 

Among the various tungsten carbide phases, WC has been known for the most stable phase. Chen and co-workers reported that WC was more stable than W2C under anodic potential range (6). In this report, W2C led to the anodic current peak at lower anodic potential (between 0.4 and 0.6 V vs Normal Hydrogen Electrode (NHE)) than WC (above 0.6 V vs NHE) in 0.5 M H2SO4 electrol3dn. This anodic current at lower potential means that W2C is more easily oxidized than WC and could be more easily lost in electrochemical applications. In addition, W2C showed higher corrosion currents than WC at the same potential (147). 

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