Comparative study of multiwall carbon nanotube nanocomposites by Raman, SEM, and XPS measurement techniques

Substantial research efforts are under way to optimize the production of composites enhanced by the incorporation of nanomaterial fillers such as multiwall carbon nanotubes (MWCNTs). It is therefore critical to develop robust methods to detect and characterize MWCNTs in nanocomposites to measure product performance and potential risks from release of the MWCNTs. In this study, the effectiveness of X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and scanning electron microscopy (SEM) methods is assessed on a series of MWCNT-epoxy nanocomposites samples. A general trend of positive correlation between signal intensity and MWCNT mass loading was observed by both Raman spectroscopy and XPS. Raman spectroscopy was capable of detecting MWCNTs at the lowest nominal concentration tested (0.01%), while for XPS, MWCNTs were detected down to a threshold of approximately 0.5%. Analysis of the same locations of two nanocomposite samples with nominal MWCNT mass fractions of 0.3% and 1% using Raman chemical imaging and SEM revealed a similar detectability of MWCNT clusters and with the higher mass loading sample having a greater number of MWCNT-rich domains. Overall, these results show a good comparability among the different techniques and therefore provide comprehensive, nondestructive microscopy methods to characterize nanocomposites.