Critical insights into understanding the effects of synthesis temperature and nitrogen doping towards charge storage capability and microwave shielding in nitrogen-doped carbon nanotube/polymer nanocomposites†
In this study, various nitrogen-doped (N-doped) multiwall carbon nanotubes (MWNTs) were synthesized by varying the synthesis temperature (650 °C, 750 °C and 850 °C), and their charge storage capability and electromagnetic (EM) shielding effectiveness (SE) were assessed by incorporating them into a PVDF (polyvinylidene fluoride) matrix. Nitrogen doping was adopted to generate numerous polarizable centers in MWNTs. The concentration of nitrogen and polarizing centers was optimized by varying the synthesis temperature. The nitrogen doping had a significant impact on the structural, thermal, and electrical properties of MWNTs. Dielectric spectroscopy of the nanocomposites containing self-polarizable MWNTs showed significantly low loss tangent, exhibiting good charge storage ability at a given concentration of MWNTs. The electrical conductivity of N-doped nanocomposites decreased as the synthesis temperature increased from 650 °C to 850 °C. This phenomenon was observed to be significantly different to the bulk powder. The electrical conductivity of the nanocomposites was also reflected in the EM shielding results where the nanocomposites containing N-doped MWNTs showed lower shielding effectiveness than the un-doped MWNTs. Moreover, the SE decreased with increasing synthesis temperature for N-doped MWNTs. Taken together, this study demonstrates critical insights about the impact of nitrogen doping and synthesis temperature on electrical conductivity, charge storage ability, and EM shielding of MWNT polymer-based nanocomposites.