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A comprehensive study of pristine and calcined f-MWCNTs functionalized by nitrogen-containing functional groups
We present the study of pristine and calcined f-MWCNTs functionalized by nitrogen-containing
functional groups. We focus on the structural and microstructural modification tuned by
the previous annealing. However, our primary goal was to analyze the electronic structure and
magnetic properties in relation to the structural properties using a multi-technique approach. The
studies carried out by X-ray diffraction, XPS, and 57Fe Mössbauer spectrometry revealed the presence
of -Fe nanoparticles, Fe3C, and -FeOOH as catalyst residues. XPS analysis based on the deconvolution
of core level lines confirmed the presence of various nitrogen-based functional groups
due to the purification and functionalization process of the nanotubes. The annealing procedure
leads to a structural modification mainly associated with removing surface impurities as purification
residues. Magnetic studies confirmed a significant contribution of Fe3C as evidenced by a Curie
temperature estimated at TC = 452 15K. A slight change in magnetic properties upon annealing
was revealed. The detailed studies performed on nanotubes are extremely important for the further
synthesis of composite materials based on f-MWCNTs