Nitrogen storage properties based on nitrogenation and hydrogenation of rare earth-iron intermetallic compounds R2Fe17(R=Y, Ce, Sm)

摘要

The nitrogen storage properties for the rare earth-iron intermetallic compounds, R2Fe ~ (R=Y, Ce, and Sm), wereinvestigated. These intermetallic compounds formed thecorresponding metal nitrides by heating in a mixed gas of NH3-H2at 350-450℃ and the nitrogen was incorporated into interstitialsites of the crystal lattices. The nitrogen stored as the metal nitrideswas reversibly released as NH3 by the following heating in H2 at450℃. An amount of the nitrogen released per unit volume ofthese intermetallic compounds is larger than that of a conventionalnitrogen container charged at 15 MPa. The nitrogen storagecapacity of Sm2Fe17Nx was increased by repeating thenitrogenation-hydrogenation cycle owing to the formation ofFeNx/RNy composites with large surface areas derived from thestarting intermetallic compound through the cycle. Furthermore,the nitrogen storage characteristics of Sm2Fe17 powders wereeffectively improved by surface loading with Ru metal that isactive for ammonia generation.