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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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
|Subjects:||Material Science > Nanochemistry|
|Deposited On:||06 Jun 2011 07:59|
|Last Modified:||06 Jun 2011 07:59|
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