Mechanochemical nitridation by ball milling iron with m-phenylene diamine

Abstract The solid state synthesis reactions between elemental α-Fe powder and m -phenylene diamine (C 6 H 4 (NH 2 ) 2 ) have been studied. The different phase transformations are found in the course of milling and during subsequent thermal annealing. The single e-Fe 2–3 N phase with nitrogen concentration up to 11.53 wt% was obtained after 250 h ball milling. Owing to the local inhomogeneity of N content, the e-Fe 2–3 N phase can be formed by ball milling at room temperature, even though the sample has a low average N content. The saturation magnetization M S and coercivity H C of e-Fe 2–3 N are 81.4 A m 2 /kg and 16.28 kA/m. Thermal analysis experiments show structural stability of the e-Fe 2–3 N phase up to 512.0°C. On comparison with α-Fe ball milled in NH 3 atmosphere, it is evident that the nitridation process in our experiment occurs more rapidly because more active nitrogen-containing radicals can be maintained during the milling process. It illustrates that the solid–solid reaction is more efficient than the solid–gas reaction.