Study of Phase Transitions Occurring in a Catalytic System of ncFe-NH3/H2 with Chemical Potential Programmed Reaction (CPPR) Method Coupled with In Situ XRD

Nitriding of nanocrystalline iron and reduction nitride with gaseous mixtures hydrogen ammonia were studied at 375 °C atmospheric pressure using the chemical potential programmed reaction (CPPR) method coupled in situ XRD. In this paper, a series phase transitions occurring during processes is shown, detailed analysis composition structure material given. The influence variable nitriding on lattice parameters α-Fe, γ′-Fe4N, ε-Fe3-2N phases shown. α interplanar space changes irrelevantly one area but decreases linearly average increases crystallite size when α→γ′ transformation occurs. nanocrystallite distributions (nCSDs) determined, nCSD for ε reduction. can occur directly to or indirectly an intermediate step γ′ formation as result ε→γ′→α transformations. determining factor reducing process volume nanocrystallites. Those V < 90,000 nm3 undergo direct ε→αFe(N), > transforms αFe(N) indirectly. It was determined what value which fraction nanocrystallites starts reduce