Iron/multiwalled carbon nanotube (Fe/MWCNT) hybrid materials characterization: thermogravimetric analysis as a powerful characterization technique

Abstract

Nanomaterials and nanocomposites have gained relevance in science and technology due to their excellent properties. Therefore, the characterization of these materials is important. Thermogravimetric analysis is a powerful technique for the characterization of iron-carbon nanotubes (Fe/MWCNT) as hybrid nanomaterials, which may be prepared by impregnation step (alkaline or microwave-assisted precipitation). High-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD and in situ XRD), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) were the instrumental techniques used to characterize these hybrid materials. Through TGA, it was possible to determine the quantity of effective impregnated iron on the MWCNT. Further, in a TGA, nitrogen atmosphere reveals a thermal event reflecting the iron reduction by C from MWCNT and the shape of the signal reflects the dispersion and size of the iron particles on the surface. This thermal event is related to the particle sizes and chemical nature of iron oxides present. Thermal events from TGA may be correlated with the results obtained from XRD, XPS, and HR-TEM. The presence of smaller and well-distributed iron nanoparticles impacts the shape of the reducing event in the TGA. The reduction temperature as observed in TGA curves is related to the nature of metal compounds present, such as nitrates or oxides. These results suggest that TGA can be used as a rapid and economical technique for the evaluation of different Fe/MWCNT hybrid material properties. These results may facilitate the estimation of the structural and chemical nature of the Fe/MWCNT nanohybrid materials and permit the projections of potential applications.