In situ high-temperature Mössbauer spectroscopic study of carbon nanotube―Fe―Al2O3 nanocomposite powder

• Published in: Thermochimica acta Vol. 494; no. 1-2; pp. 86 - 93
• Main Authors: DE RESENDE, Valdirene G, PEIGNEY, Alain, DE GRAVE, Eddy, LAURENT, Christophe
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier 10-10-2009
• Subjects: Cross-disciplinary physics: materials science; rheology; Engineering Sciences; Exact sciences and technology; Materials; Materials science; Nanopowders; Nanoscale materials and structures: fabrication and characterization; Physics; Powders; In situ; Thermogravimetry; Carbon nanotubes; Moessbauer spectroscopy; Iron; XRD; Nanostructures; Electron microscopy; Thermal stability; Aluminium Oxides; Composite materials; Nanocomposites; Transition elements; Mössbauer spectroscopy; Oxidation; Thermal analysis; Nanopowder; Electrochemical reaction; Alumina
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/j.tca.2009.04.024

The oxidation of a carbon nanotube–Fe–Al2O3 nanocomposite powder was investigated using notably thermogravimetric analysis, room temperature transmission and emission Mössbauer spectroscopy and, for the first time, in situ high-temperature transmission Mössbauer spectroscopy. The first weight gain (150–300 °C) was attributed to the oxidation into hematite of the α-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 °C or above. A weight loss (300–540 °C) corresponds to the oxidation of carbon nanotubes and graphene layers surrounding the nanoparticles. The graphene layers surrounding γ-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 °C) correspond to the oxidation of the intragranular α-Fe particles and the γ-Fe–C particles.