Phase Analysis of Magnetic Inclusions in Nanornaterials Based on Multiwall Carbon Nanotubes

Functionalized multiwall carbon nanotubes as well as nanocomposite based on that material covered by nanoparticles composed of iron oxides were the subject of investigations. In order to identify all iron-bearing phases including those reported on the base of previous X-ray diffraction measurements, the transmission Mossbauer spectroscopy was utilized. The experiments were carried out both at room temperature and also at low tempera tures. It was stated that in the investigated nanotubes some impurities were present, originating from the catalyst remains, in form of Fe-C and alpha-Fe nanoparticles. The Mossbauer spectra collected for the nanocomposite showed a complex shape characteristic of temperature relaxations. The following subspectra related to iron-based phases were identified: sextet attributed to hematite, with hyperfine magnetic field reduced due to the temperature relaxations, sextet corresponding to iron carbide as well as two doublets linked to superparamagnetic hematite and ferrihydrites.