Formation of epsilon-Fe2O3 phase by the heat treatment of alpha-Fe2O3/SiO2 nanocomposite
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Starting from a nanocomposite consisting of 4 nm hematite nanoparticles embedded in a silica matrix (30 wt.% hematite) and by applying heat treatments at increasing temperatures up to 1050 degrees C, gradual formation of epsilon-Fe2O3 phase was obtained. Besides representing a new synthesis route of epsilon-Fe2O3 phase, the results obtained in this work indicate that under certain conditions hematite nanoparticles are not thermally stable. Hence, like other ferric oxide polymorphs, nanosized hematite can undergo thermally triggered, size-induced structural phase transitions. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.