PREPARATION OF THE SINGLE-PHASE GAMMA'-(FE1-XNIX)(4)N COMPOUNDS LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.6)

Single phase gamma'-Fe4N type (Fe1-xNix)4N compounds (0 less than or e qual to x less than or equal to 0.6) have been synthesized for the fir st time by controlled heat treatment of iron-nickel oxalates in a gase ous flow of NH3 rand H-2. The preparation processes were investigated using differential scanning calorimetry (DSC), X-ray diffraction and M ossbauer spectroscopy. The results confirmed that annealing of oxalate s in the NH3 and H-2 atmosphere included the processes of dehydration, decomposition and reduction, nitrogenation and thermal decomposition of the nitrides. The decomposition and reduction occur simultaneously. The final products depend on the flow rate ratio of NH3:H-2 and the a nnealing temperature. The formation conditions for the single phase ga mma'-Fe4N type (Fe1-xNix)(4)N compounds are related to the nickel conc entration, with increasing nickel content, the nitrogenation temperatu re decreased, in contrast the flow rate ratio of NH3:H-2 increased.