THERMODYNAMICS OF NITRIDE AND HYDRIDE FORMATION BY THE REACTION OF METALS WITH FLOWING NH3

The state where the equilibrium dissociation of ammonia, NH3 = 1/2N2 + 3/2H2, is not reached can be produced by flowing NH3. In this case NH3 must be considered to be in an unstable state. Nitrogen-rich metal nitrides, which cannot be obtained by action of N2 under normal pressures, can be prepared by use of a stream of NH3. This suggests that high nitrogen activity may arise from the high instability exhibited by a stream of NH3. It may be highly probable that a stream of NH3 also acts as a hydriding agent with high hydrogen activity. A thermodynamic analysis was performed with the object of gaining insights into these aspects from the equilibrium point of view.