화학공학소재연구정보센터
Thermochimica Acta, Vol.494, No.1-2, 86-93, 2009
In situ high-temperature Mossbauer spectroscopic study of carbon nanotube-Fe-Al2O3 nanocomposite powder
The oxidation of a carbon nanotube-Fe-Al2O3 nanocomposite powder was investigated using notably thermogravimetric analysis, room temperature transmission and emission Mossbauer spectroscopy and, for the first time, in situ high-temperature transmission Mossbauer spectroscopy. The first weight gain (150-300 degrees C) was attributed to the oxidation into hematite of the alpha-Fe and Fe3C particles located at the surface and in the open porosity of the alumina grains. The 25 nm hematite particles are superparamagnetic at 250 degrees C or above. A weight loss (300-540 degrees C) corresponds to the oxidation of carbon nanotubes and graphene layers surrounding the nanoparticles. The graphene layers surrounding gamma-Fe-C particles are progressively oxidized and a very thin hematite layer is formed at the surface of the particles, preventing their complete oxidation while helping to retain the face-centered cubic structure. Finally, two weight gains (670 and 1120 degrees C) correspond to the oxidation of the intragranular alpha-Fe particles and the gamma-Fe-C particles. (C) 2009 Elsevier B.V. All rights reserved.