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Open Access Influence of the Hydrogen Reduction Time and Temperature on the Morphology Evolution and Hematite/Magnetite Conversion of Spindle-Type Hematite Nanoparticles

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We report on the transformation via hydrogen reduction of spindle-type hematite nanoparticles into hematite/magnetite hybrid iron oxide particles. The transformation process consists of the reduction of nanoparticles powder in an autoclave using hydrogen gas at a fixed pressure of 11 bars. Both temperature and time of reduction are varied between 300 °C to 360 °C and 0 to 45 h. X-Ray powder diffraction data on the obtained powder and corresponding Rietveld refinement allow the amount of reduced hematite to be determined as a function of these two parameters. Kinetics parameters are measured and an estimation of the activation energy is obtained through linearization of the Arrhenius equation. While reduction is dramatically accelerated at higher temperature, the morphology of the nanoparticles only remain qualitatively unchanged at 300 °C as seen from transmission electron microscopy images. The mechanisms underlying morphology changes are still under study and seem to be closely related to reactor pressure.

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Document Type: Regular Paper

Affiliations: 1: Ecole d'Ingénieurs et d'Architectes de Fribourg, Boulevard de Pérolles 80, CP 32 CH-1705 Fribourg, Switzerland. [email protected] 2: Ecole d'Ingénieurs et d'Architectes de Fribourg, Boulevard de Pérolles 80, CP 32 CH-1705 Fribourg, Switzerland 3: University of Fribourg, Adolphe Merkle Institute, Route de l'Ancienne Papeterie, P. O. BOX 209, CH-1723 Marly 1, Switzerland. [email protected]

Publication date: December 1, 2011

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  • International Journal for Chemistry and Official Membership Journal of the Swiss Chemical Society (SCS) and its Divisions

    CHIMIA, a scientific journal for chemistry in the broadest sense, is published 10 times a year and covers the interests of a wide and diverse readership. Contributions from all fields of chemistry and related areas are considered for publication in the form of Review Articles and Notes. A characteristic feature of CHIMIA are the thematic issues, each devoted to an area of great current significance.

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