Formation of iron-nitride/silver nanocomposites by ammonia-flow method and nitride phase identification by X-ray absorption near-edge structure

Magnetic nanocomposites in which iron nitride nanograins were dispersed in a silver matrix were synthesized by nitriding iron oxide nanograins buried in the matrix. The ammonia-flow method, in which the solid phase reacted with flowing ammonia, was adopted for this synthesis. Several reactions of metallic iron with NH3 were carried out under various conditions and the resultant nitride phases were observed by X-ray diffraction (XRD). Based on these results, optimum conditions for the synthesis of the nanocomposite were determined, and a nanocomposite containing only gamma'-Fe4N or epsilon-Fe2-4N was successfully obtained. Phase identification of iron nitride in the composite was performed by X-ray absorption near-edge structure (XANES) measurement, which was found to be more suitable for the present nanocomposites than XRD.