Thermoelectric Behavior of Segregated-Network Polymer Nanocomposites

Abstract

Segregated-network carbon nanotube (CNT)-polymer composites were prepared, and their thermoelectric properties were measured as a function of CNT concentration at room temperature. This study shows that electrical conductivity can be dramatically increased by creating a network of CNTs in the composite, while the thermal conductivity and thermopower remain relatively insensitive to the filler concentration. This behavior results from thermally disconnected, but electrically connected, junctions in the nanotube network, which makes it feasible to tune the properties in favor of a higher thermoelectric figure of merit. With a CNT concentration of 20 wt %, these composites exhibit an electrical conductivity of 4800 S/m, thermal conductivity of 0.34 W/m x K and a thermoelectric figure of merit (ZT) greater than 0.006 at room temperature. This study suggests that polymeric thermoelectrics are possible and provides the basis for further development of lightweight, low-cost, and nontoxic polymer composites for thermoelectric applications in the future.

Thermal energy harvesting for large-scale applications using MWCNT-grafted glass fibers and polycarbonate-MWCNT nanocomposites

“…Their use can result in polymer composites with electrical conductivities up to 4×10 5 S/m as reported by Moriarty et al [22]. Relatively high filler loadings (>> 50 wt.%) can be realized [16], which result in quite high electrical conductivities [19,20,[23][24][25], while power factors being in the range of ~140 μW/mK -2 have been reported for single-walled carbon nanotubes (SWCNTs) in poly (3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) matrix [22]. However, such high filler loadings may result also in a significant increase of thermal conductivity [15,26,27].…”

“…In specific, they are of particular interest due to their low thermal conductivity, high electrical conductivity, ease of production, relatively low cost, flexibility and high specific properties. Accordingly, several studies exist in which polymer/CNT nanocomposites have been utilized for thermal energy harvesting [3,[12][13][14][15][16], and they have been investigated both theoretically [14] as well as experimentally [17,18]. The CNT networks in a polymer matrix have the ability to allow electron transport by tunneling, when junctions are separated by an insulating polymer film (even of some nm thick).…”

Magneto-Seebeck effect in an ITO/PEDOT:PSS/Au thin-film device

“…25 Moreover, through phonon scattering at interfaces, boundaries and imperfections, the nano-scale heterojunctions allow charge transport through tunneling and minimize the thermal conductivities. [26][27][28][29] By applying the conducting polymer in the low dimensional hybrids, the thermal conductivity can be largely reduced, while still permitting high electrical conductivity resulting in the enhancement of the figure of merit. The surface polarization has also been demonstrated as an additional driving force to diffuse charge carriers in vertical hybrid architecture for the development of Seebeck effects.…”

Carbon Nanotubes as Conductive Filler in Segregated Polymer Composites - Electrical Properties

“…A percolation threshold below 0.04% of SWCNT was achieved when an emulsion polymer (i.e., latex) has been used as the polymer matrix (Grunlan et al, 2004). Formation of the segregated SWCNT structure in PVA emulsion allows achievement of high electrical conductivity (48 S/cm) and acceptable thermopower at low thermal conductivity in solid state of the composite that indicates the promising applications of such a type of materials in thermoelectric systems for collection and generation of energy (Yu et al, 2008).…”