This study investigates the impact of nitrogen doping on the performance of carbon nanotube (CNT)/polymer nanocomposites for thermoelectric applications; this was performed through measurement of conductivity of the generated nanocomposites. Three different catalysts (Co, Fe, and Ni) were used to synthesize nitrogen-doped CNTs (N-CNTs) by chemical vapor deposition technique. Synthesized N-CNTs were melt-mixed with a polyvinylidene fluoride (PVDF) matrix with a small-scale mixer at a broad range of loadings from 0.3 to 3.5 wt.% and then compression molded. Measurement of electrical conductivity of the generated nanocomposites showed superior properties in the following order of the synthesis catalyst: Co > Fe > Ni. We employed various characterization techniques to figure out the reasons behind dissimilar electrical conductivity of the generated nanocomposites, i.e., transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, thermogravimetric analysis, light microscopy, and rheometry. It was found out, that the superior electrical conductivity of (N-CNT)Co nanocomposites was due to a combination of high synthesis yield, high aspect ratio, low nitrogen content, and high crystallinity of N-CNTs coupled with a good state of N-CNT dispersion. Moreover, it was revealed, that nitrogen doping had an adverse impact on electrical conductivity and, thus, on thermoelectric performance of CNT/polymer nanocomposites.
Part of the book: Thermoelectrics for Power Generation