The carburization of iron oxide with carbon monoxide: Modifications of hägg iron carbide

Abstract

AbstractThis study was undertaken because of its potential use in catalysis as well as in metallurgy. Modifications of Hägg iron carbide, exhibiting differences in X‐ray diffraction patterns and Curie points, have been observed; the differences appear to be linked to the mode of preparation. Carburization of reduced iron with carbon monoxide leads to ‘normal’ Hägg iron carbide with a Curie point at 245°to 250°; carburization of iron oxide produces Hägg iron carbide with a higher Curie point, up to 276°. The ‘high‐Curie‐point’ carbide progressively approaches the ‘normal’ form with increasing temperature and time of carburization. Possible explanations for the ‘high‐Curie‐point’ modification, based on the effect of oxygen, alkali, or crystallite size, are suggested. The Curie point of 247 ± 3°is that of pure, well‐crystallized Hägg iron carbide.