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High-temperature XRD study of thermally induced structural and chemical changes in iron oxide nanoparticles embedded in porous carbons

Schettino, M. A. and Freitas, J. C. C. and Morigaki, M. K. and Nunes, E. and Cunha, A. G. and Passamani, E. C. and Emmerich, F. G. (2010) High-temperature XRD study of thermally induced structural and chemical changes in iron oxide nanoparticles embedded in porous carbons. Journal of Nanoparticle Research, 12 (8). pp. 3097-3103.

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Abstract

Magnetic carbon-based nanomaterials have promising applications in many fields owing to their biocompatibility and thermal/mechanical stability. This study describes a high-temperature X-ray diffraction (XRD) study of the chemical and structural transformations suffered by superparamag- netic iron oxide nanoparticles embedded in porous carbons. The nanoparticles were prepared from the decomposition of iron pentacarbonyl over porous carbons, resulting in nanometer-sized iron oxides homogeneously dispersed into the carbon matrix. The thermally induced changes in these materials were followed by in situ high-temperature XRD, using synchrotron radiation. The growing of the nanopar- ticles and of the carbon crystallites were first observed, followed by the reduction of the iron oxides to form a-Fe (at temperatures as low as 400 C in some cases) and c-Fe(C). The temperatures at which these chemical reactions occurred were depen- dent on the total time spent on heating and on the nature of the iron oxides formed in the as prepared materials. A noticeably large thermal expansion coefficient was also observed for the iron oxide nanocrystals. The formation of austenitic iron, stabi- lized by the presence of carbon, was found to be only partially reversible upon cooling

Item Type:Article
Subjects:Material Science > Nanochemistry
ID Code:9914
Deposited By:CSMNT
Deposited On:06 Jun 2011 07:59
Last Modified:06 Jun 2011 07:59

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