Catalytic behavior of LaFeO3 pervoskite oxide during low-pressure gas nitriding

Abstract

The LaFeO3 perovskite oxide has been proved to be an effective catalyst in the gas nitriding. However, its catalytic efficiency was sensitive to the nitriding parameters. In order to clarify the catalytic conditions of the LaFeO3 oxide, the low-pressure gas nitriding was carried out in the present work. The effects of gas pressure and ammonia flow rate on catalytic behavior of the LaFeO3 oxide were discussed. The catalytic feature and conditions of the LaFeO3 oxide was identified. The microstructure and phase composition of nitrided layers were analyzed by the optical microscope, transmission electron microscopy, scanning electron microscope and X-ray diffraction, respectively. The microhardness profiles of nitrided layers were measured by micro-hardness tester to evaluate catalytic efficiency of the LaFeO3 oxide. The X-ray photoelectron spectroscopy was applied to reveal the catalytic behavior. The results show that the LaFeO3 perovskite oxide exhibited an excellent catalytic activity via accelerating dissociation of ammonia molecules and diffusion of nitrogen atoms. The dehydrogenation reaction of ammonia molecules was the rate-determining step for the rare earth nitriding, which was greatly affected by gas pressure and ammonia flow rate. The LaFeO3 catalyst shows an excellent durability of catalytic activity in low pressure and low flow rate conditions.