A Mössbauer study of sub-micron particles in the calciferous and calciferous-aluminous mixed oxide system (C-A-F) system)

A study was undertaken to prepare sub-micron particles of mixed oxides within the composition range CaO·Fe2O3 to 6CaO·2.2Al2O3·0.8Fe2O3 using both quenching and slow controlled cooling of a melt. Estimations of the particle sizes were obtained from the Blocking temperature using Mössbauer spectrometry and from the widths of X-ray diffraction lines. Sub-micron particles of 4CaO·Al2O3·Fe2O3 were shown to be superparamagnetic below 30 Å, which explains the anomalously high magnetic susceptibilities found in high-alumina cement and pulverised fuel ash.