Nitrides, free-energy diagram

Similar free-energy diagrams, which can be interpreted in exactly the same way, have been constructed for sulphides , carbides and nitrides (Figs. 7.56 to 7.58). 

Using an active metal such as Zr, we can get an idea about the possible reactions by using the Ellingham free-energy diagrams. Figure 15.21 is a plot of the free energy of formation of selected nitrides as a function of temperature. The lines represent the reaction... 

Figure 4 Richardson diagram of various transition metal mononitrides (together with other nitrides) giving the free energy of formation as a function of temperature. (Ref 4. Reproduced by permission of Wiley VCH)...

Schick s work includes the study of borides, carbides, nitrides, and oxides of some elements in Groups IIA, IIIB, IVA, IVB, VB, VIIB, and VIII as well as selected rare earths and actinides. As far as possible, the tables have been made compatible with the JANAF tables. Among the subjects treated are phase diagrams, heat capacities, enthalpies, entropies, enthalpies of phase transformation, formation, and reaction, melting temperatures, triple points, free energies of formation, vapour pressures, compositions of vapour species, ionization and appearance potentials, e.m.f. of cells, and enthalpies of solution and dilution. Volume 1 summarizes the techniques used to analyse data and cites the data analysed, and Volume 2 gives tables of values produced by this study. 

Since many ceramics are oxides, the oxygen partial pressure, p02, is an important variable. There is a lot of information about many metal-oxygen systems. In part, this is due to interest in how to obtain metals by direct reduction from their oxides. A frequent way of representing free energies of formation of oxides as a function of pOi and T is the Ellingham diagram (Ellingham, 1944) that was popularized by Richardson and Jeffes (1948) for iron and steel production. Much less is known about nitrides and oxynitrides or even carbides. 

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