# Carbon Allotropes/Epoxy Nanocomposites as Capacitive Energy Storage/Harvesting Systems
## 3 Results and Discussion
### Thermal and Mechanical Characterization  
Differential Scanning Calorimetry was employed for the investigation of the thermal properties of the nanocomposites. An endothermic step-like process was recorded in the thermograms of all examined systems, which was identified as the transition from the glassy to the rubbery state of the polymer matrix. The characteristic glass transition temperature for all systems was determined at the point of inflection using suitable software provided by TA instruments. The results are listed in Table 6. The variation of the glass transition temperature with filler content can give an insight into the different interactions occurring inside the materials. Increasing T\({}_{\text{g}}\) values indicate strong interactions between the \begin{table}
\begin{tabular}{c c} \hline \hline  & **BDS** \\ \hline Frequency range & 10\({}^{-1}\)-10\({}^{7}\) Hz \\ Temperature range & 30–160 \({}^{\circ}\)C \\ Temperature step & 5 \({}^{\circ}\)C/min \\ Stabilization time & 60 s \\ V\({}_{\text{rms}}\) & 1 V \\ \hline \hline \end{tabular}
\end{table} 
Table 4: BDS parameters. \begin{table}
\begin{tabular}{c c} \hline \hline  & **DC Measurements** \\ \hline Applied Voltages & 50, 100, 250 V \\ Charging time & 60 s \\ Discharging time & 600 s \\ Temperature & Ambient \\ \hline \hline \end{tabular}
\end{table} 
Table 5: DC measurements’ parameters. nanoparticles and the macromolecules that obstruct the cooperative segmental movement of the polymer chains. All nanocomposites exhibit higher glass transition temperature values than the neat epoxy, which is a sign of the good adhesion of the nanofillers to the polymeric matrix. Carbon black nanocomposites exhibit a progressive increase in T\({}_{\text{g}}\) values with filler content while, on the other hand, nanocomposites filled with nanodiamonds show a remarkable stability across the board. At high concentrations for the GnP and MWCNT-filled nanocomposites, the interactions between adjacent nanoparticles, due to their aspect ratio, become stronger, thus cancelling part of the hindrance of the chain mobility and slightly lowering the values of the glass transition temperature. The mechanical properties of polymer nanocomposites are dictated by several parameters including the individual properties of the constituents and the distribution of fillers in the polymer matrix, as well as interfacial bonding and the fabrication method. The addition of carbonaceous nanoparticles enhances the mechanical properties of the nanocomposites as demonstrated by the static and dynamic tests (Figures 3 and 4, respectively). The tensile modulus was determined as the slope of the stress-strain curve in the elastic region. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Specimens**} & **CB** & **GnP** & **MWCNT** & **ND** \\ \cline{2-5}  & **T\({}_{\text{g}}\)**(°C)** & **T\({}_{\text{g}}\)**(°C)** & **T\({}_{\text{g}}\)**(°C)** & **T\({}_{\text{g}}\)**(°C)** \\ \hline Epoxy & 44.6 & 44.6 & 44.6 & 44.6 \\
0.1 phr & 43.7 & 52.0 & 51.7 & 53.2 \\
1 phr & 46.4 & 53.3 & 51.8 & 54.0 \\
3 phr & 55.6 & 53.9 & 53.7 & 53.5 \\
5 phr & 56.1 & 58.8 & 52.1 & 53.3 \\
7 phr & 56.3 & 55.3 & 51.7 & 53.7 \\
10 phr & 57.4 & 54.9 & 50.2 & 52.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Glass transition temperature as determined via DSC test, for all examined systems. Figure 2: SEM images of the nanocomposites with 3 phr: (**a**) CB; (**b**) MWCNT; (**c**) GnP; (**d**) ND content. Figure 3 presents the [PERSON]'s modulus and tensile strength versus filler content for all examined nanocomposites. Error bars denote the standard deviation of the representative results. The Young's modulus increases predictably with filler concentration for all systems except the nanocomposites filled with nanodiamonds.