NON-EQUILIBRIUM GAS-PHASE NITROGENATION

Authors

S. Brennan, Trinity College, Dublin, Ireland
Ralph Skomski, University of Nebraska-LincolnFollow
J.M.D. Coey, Trinity College, Dublin, Ireland

Date of this Version

March 1994

Comments

Published in IEEE TRANSACTIONS ON MAGNETICS, VOL. 30, NO. 2, MARCH 1994.

Abstract

Non-equilibrium nitrogenation of transition-metal rich rare-earth intermetallics can be used to increase the nitrogen content beyond its equilibrium concentration. For example, nitrogenation of Sm₂Fe₁₇ using ammonia yields volume expansions up to 8.3 vol %, which correspond to a composition Sm₂Fe₁₇N_x with x = 4. This effect is related to catalytic action at the metal surface where ammonia is decomposed into nitrogen and hydrogen, with nitrogen absorption on a site where it is weakly bound, as an intermediate step. For overloaded Sm₂Fe₁₇N_x with x>3 the net reaction energy U₀ = 5 ±10 kJ/mole indicates a nearly temperature-independent occupation of the non-9e sites.