SYNTHESIS OF FE3N BY MECHANOCHEMICAL REACTIONS BETWEEN IRON AND ORGANIC H-X(CN)(6) RING COMPOUNDS

Novel mechanically activated solid state synthesis reactions between e lemental alpha Fe powder and amine compounds-piperazine (H10C4N2) and pyrazine (H4C4N2)- have been studied. Powder samples prepared after 14 4 and 228 h of ball milling in vacuum were examined by X-ray diffracti on, scanning electron microscopy and thermal analysis methods. After b all milling for a time brief compared to that required for most solid state-gas reactions formation oi a crystalline iron nitride (Fe3N) a p redominant phase with nitrogen concentration up to ca, 9.0 wt % was ob served. Thermal analysis experiments showed structural stability of th e Fe3N phase up to ca. 720 K. In the final product a small residual fr action was formed from alpha Fe and carbon dispersed during mechanical processing. The concentration of carbon in this fraction, estimated f rom thermogravimetric analysis was up to 2.5 wt %, dependent on millin g conditions and the organic compound used. Mechanochemical synthesis, reaction effectiveness, product composition and particle morphology d epends on the milling time and chemical characteristics of the organic compound used. Fine Fe3N particles at a submicrometre size range were obtained only by milling with pyrazine. Further, the higher chemical reactivity of pyrazine than piperazine was confirmed through the highe r level of nitridation achieved in the same preparation time.