DETERMINATION OF THE PARTICLE-SIZE DISTRIBUTION OF IRON-OXIDE CATALYSTS FROM SUPERPARAMAGNETIC MOSSBAUER RELAXATION SPECTRA

Mössbauer spectroscopy has been used to investigate the particle-size distribution of a variety of ultrafine iron-based direct coal liquefaction catalysts having either Fe2O3 or FeOOH composition. The Mössbauer spectra of these catalysts showed pronounced superparamagnetic relaxation effects. The relaxation spectra were analyzed as a function of temperature using a novel fitting model to determine the particle-size distribution for these catalysts. The resulting size distributions are in the nanometer range and agree reasonably well with size information obtained by scanning transmission electron microscopy (STEM), SQUID magnetometry, and X-ray diffraction (XRD). © 1993 Academic Press, Inc.