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

Document Type

Article

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.