Study of the kinetics of the nitriding of the nanocrystalline iron
using the TG and XRD methods

W. Arabczyk, R. Wróbel
Technical University of Szczecin, Institute of Chemical and
Environment Engineering, Pulaskiego 10, 70-322 Szczecin, Poland

The interaction of the nanocrystalline iron with ammonia has been
investigated. The reaction was carried in the thermobalance at 500 OC.
The obtained TG curves present the characteristic linear sections
corresponding to the a-Fe and g'-Fe[4]N phases. The samples having
different conversion degree have been obtained by a freezing of the
process. The obtained samples were submitted to the XRD analysis. The
Scherrer's method has been used to determine a mean crystallite size
of the phases. The mean crystallite size of the substrate as well as
of the product has been found to increase with an increasing
conversion degree. The mean crystallite size of product (after the
total conversion was reached) was equal to that of the substrate. The
specific surface area did not change as a result of the nitriding
process. The above facts can not be explained using the "core and
shell" model. If the dissociative adsorption of ammonia is the
limiting step of the nitriding process, then the nucleation process
occurs according to a new model, in which the crystallites undergo to
the phase transition following to their size. The greater crystallites
do not undergo to the phase transition until the smaller ones are
converted. This phenomenon can be explained taking into account the
relation between the specific surface area of the crystallites and
their size. The theoretical predictions about the dependence of the
mean crystallite size on the conversion degree, according to the new
model and to the "core and shell" one, are in agreement only with the
first model.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/413 must be provided.

1. The XRD study of the nanostructured TiC/C and TiN/C composites.
2. The kinetics of the nanocrystalline iron nitrides reduction
3. The XRD Method of the Determination of the Size Distribution of the Nanocrystalline Materials