Reduction of Hematite on the Surfaces of Fe-Si Alloys

Hematite was reduced to magnetite and/or wustite on the surfaces of Fe-Si alloys during annealing in argon in dependence on the annealing temperature and silicon concentration. Hematite film was formed after pre-annealing in oxygen. Fe-Si alloys with silicon content of 6, 9, 11 and 14 at.% Si were used in this study. Heat treatments have been performed in vacuum, oxygen and argon atmospheres in the temperature range of 500 divided by 780 degrees C. Phase analysis has been carried out using Mossbauer spectroscopy and X-ray diffraction. CEMS measurements showed that the samples which were annealed in vacuum 780 degrees C have similar Mossbauer parameters like the bulk except that the sextets are shaper due to ordering dining heat treatment in vacuum. Samples which were annealed in oxygen showed hematite on their surfaces. The content of hematite on the Surfaces of these samples increases by increasing the temperature and decreases by increasing the silicon content. After annealing in argon at 500 and 600 degrees C, magnetite was formed on the surfaces of all the samples. Samples with 6 and 9 at.% Si displayed wustite and fayalite on their surfaces after annealing in argon at 700 degrees C. On the other hand, samples with higher silicon contents (11 and 14 at.% Si) displayed magnetite, wustite and fayalite on their surfaces at the same temperature. The content of wustite decreases by increasing the silicon content while the fayalite content increases with increasing the content of silicon. These results have been confirmed by XRD measurements.