Mechanochemical nitridation by ball milling iron with m-phenylene diamine

The solid state synthesis reactions between elemental alpha-Fe powder and In-phenylene diamine (C6H4(NH2)(2)) have been studied. The different phase transformations are found in the course of milling and during subsequent thermal annealing. The single epsilon-F2-3N phase with nitrogen concentration up to 11.53 wt% was obtained after 250h ball milling. Owing to the local inhomogeneity of N content, the epsilon-F2-3N 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 epsilon-Fe2-3N are 81.4 A m(2)/kg and 16.28 kA/m. Thermal analysis experiments show structural stability of the epsilon-Fe2-3N phase up to 512.0degreesC. On comparison with alpha-Fe ball milled in NH3 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. (C) 2002 Elsevier Science B.V. All rights reserved.