Energetics of binary iron nitrides

High-temperature solution calorimetry in molten sodium molybdate 3Na(2)O . 4MoO(3) was used to determine the energetics of formation of a series of binary iron nitrides: gamma'-Fe4N, epsilon-Fe3N1+y (y = 0, 0.10, 0.22, 0.30, 0.33), zeta-Fe2N and gamma"-FeN0.91. The linear relation Delta H-f(o) (FeNx)= - 65.23x + 13.48 kJ mol(-1) was found between the enthalpies of formation from the elements at 298 K of iron nitrides FeNx and their nitrogen content x. Using this linear approximation, the enthalpy of formation of alpha"-Fe16N2 has been estimated to Delta N-f(o) (Fe16N2) = 85.2 +/- 45.8 kJ mol(-1). (C) 2000 Editions scientifiques et medicales Elsevier SAS. All rights reserved.