Properties assessment of multiwalled carbon nanotubes: A comparative study

• Published in: Synthetic metals 2014-11, Vol.197, p.159-167
• Main Authors: Stefov, V., Najdoski, M., Bogoeva-Gaceva, G., Buzarovska, A.
• Format: Article
• Language: English
• Subjects: Band spectra; Bands; Carbon nanotubes; Catalytic methods; Co3O4; Cross-disciplinary physics: materials science; rheology; Density; Diffraction; Exact sciences and technology; Infrared; Lasers; Materials science; Methods of nanofabrication; Multi wall carbon nanotubes; Nanoscale materials and structures: fabrication and characterization; Nanotubes; Physics; Polyethylenes; Raman; Scanning electron microscopy; Spectra; Thermal analysis; XRPD
• ISSN: 0379-6779; 1879-3290
• DOI: 10.1016/j.synthmet.2014.09.011

•MWCNTs are obtained from polyethylene waste by pyrolysis as described previously.•Characterization/comparative study of as-prepared and commercial MWCNTs is made.•An interesting effect of laser irradiation on the Raman spectral picture is found.•In the LNT infrared spectra of the studied MWCNTs no additional bands are observed.•Thermal stability and activation energy for thermal decomposition are determined. In the last decade the interest in studies of carbon nanotubes (CNTs) from different viewpoints has been constantly increasing. In this work, we have prepared multi walled carbon nanotubes (MWCNTs) by pyrolysis of low density polyethylene (LDPE), using cobalt(II) acetate as a catalyst precursor, and then their systematic structural characterization has been carried out in parallel with the commercial MWCNTs (Nanocyl NC3100). For that purpose, scanning electron microscopy, powder X-ray diffraction, vibrational spectroscopy and thermogravimetry were used. The scanning electron microscopic images (SEM) recorded with different magnification of the synthesized product clearly showed the morphology of the carbon nanotubes. In the diffractogram of the as-prepared MWCNTs, in contrast to the commercial MWCNTs, characteristic peaks for metallic Co were observed besides the typical peaks for graphite. When studying the MWCNTs with Raman spectroscopy, an interesting effect of the laser irradiation on the spectral picture was revealed. In the Raman spectrum of the as-prepared MWCNTs recorded with laser power of 0.111mW the appearance of the bands from cobalt(II,III) oxide (Co3O4) modes clearly demonstrated the oxidation of Co particles from the sample to Co3O4. The infrared spectra of the as-prepared and commercial MWCNTs recorded at room temperature (RT) and at liquid nitrogen temperature (LNT) are shown and compared. There is no noticeable temperature effect on the spectra appearance in both the frequency and intensity of bands. The TGA and DTG curves for investigated MWCNTs in air atmosphere are presented and the overall results are summarized. The results of TGA showed that up to 350°C, the as-prepared MWCNTs are thermally stable in air, and above this temperature the process of thermo-oxidative decomposition proceeds fast and is completed at around 420°C. The activation energy for the thermal decomposition of the nanotubes is 139kJmol−1.