EFFECTS OF NITRIC ACID TEMPERATURE AND REFLUX TIME ON COVALENT FUNCTIONALIZATION OF HELICAL CARBON NANOTUBES FOR NANOCOMPOSITE APPLICATIONS

摘要

In this study a reflux process was used for chemical functionalization of helical carbon nanotubes (HCNTs). The impact of process temperature (i.e., 60 °C and 100 °C ) and reflux time (i.e., 3, 6, and 24 hours), as two key parameters for covalent functionalization of HCNTs were investigated. To evaluate the effectiveness of the process parameters, the functionalized HCNTs were examined using several characterization instruments and techniques such as, Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction Spectroscopy (XRD), visual dispersion test, and Raman Spectroscopy. The result of characterization confirmed that the change in process parameters were mostly effective and surface atomic structure of the functionalized HCNTs were successfully altered. The dispersion test results revealed more dispersion uniformity and higher solubility for the functionalized HCNTs compared to the HCNTs without treatment. The investigation on effects of process parameters showed that variation of reflux time and reflux temperature did not have any considerable impact on the solubility of functionalized HCNTs. All functionalized HCNTs demonstrated higher (D/G) ratio in their Raman spectrums. Here, increasing the reflux time led to higher (D/G) ratios, which means that more atomic defects were created on the surface of HCNTs; conversely, the rise of reflux temperature showed no clear increase in the (D/G) peak. Apart from 24 hours treatment of HCNTs, all other samples unveiled at least a change in FTIR spectrum by increasing the reflux temperature. Moreover, prolonging the reflux process led to change in certain regions of FTIR spectrum that can be considered as attachment of more functional groups to the surface of chemically functionalized HCNTs.