DETERMINATION OF PARTICLE-SIZE DISTRIBUTION IN AN FE2O3-BASED CATALYST USING MAGNETOMETRY AND X-RAY-DIFFRACTION

In this paper, the techniques of SQUID magnetometry and line broadening in x-ray diffraction are employed for determining an important parameter for catalysts, viz. the particle size distribution. Magnetization versus temperature (5 K-400 K) and magnetization versus field (up to 55 kOe) data are reported for an alpha-Fe2O3 based catalyst. After determining the region of superparamagnetism, the distribution functio f(r) is determined assuming a log normal distribution and Langevin paramagnetism of superparamagnetic particles. The distribution is found to be fairly symmetric with center near 65 angstrom and range of 35 to 115 angstrom. From line-broadening of Bragg peaks in x-ray diffraction, particle radii varying between 75 angstrom and 110 angstrom are obtained. These results are compared with the reported Mossbauer measurements of Huffman et al. on the same sample.