The process of nanocrystalline iron nitrides reduction was investigated with application of the thermogravimetry and XRD methods. The kinetics of the reduction of ε-Fe_3-2N phase was investigated under hydrogen atmosphere and temperature range 400 to 500 ⁰C. It was observed that in the reduction process the average crystallite size both of iron and iron nitride Fe₄N phases increases with conversion degree of Fe₄N to Fe. Those results indicate that reduction process is limited by surface reaction and undergoes according to the Adsorption Range Model [1].
The rate of the reduction was calculated from slope of the approximately linear part of TG curve and is proportional to the hydrogen partial pressure. The kinetic equation of reaction was proposed. Based on kinetic equation the dependence of reaction constant on temperature was determined. The process is not activated and the apparent activation energy amounts -17 kJ/mol.
The Adsorption Range Model allows a better description of the process by the numerical modelling. In this way a good agreement of theoretical data with experimental ones was achieved. The free energy of nitrogen segregation as a function of bulk nitrogen concentration was obtained.

1. W. Arabczyk, R. Wróbel, Study of the kinetics of nitriding of the nanocrystalline iron using the TG and XRD methods, Solid State Phenomena, Vol. 94 (2003) pp. 185-188,

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1. The XRD study of the nanostructured TiC/C and TiN/C composites.
2. Study of the Kinetics of the Nitriding of the Nanocrystalline Iron Using the TG and XRD Methods
3. The XRD Method of the Determination of the Size Distribution of the Nanocrystalline Materials