Epoxy-Encapsulated ZnO-MWCNT Hybrid Nanocomposites with Enhanced Thermoelectric Performance for Low-Grade Heat-to-Power Conversion.

This work is devoted to the development of epoxy-encapsulated zinc oxide-multiwalled carbon nanotubes (ZnO-MWCNT) hybrid nanostructured composites and the investigation of their thermoelectric performance in relation to the content of MWCNTs in the composite. For the preparation of nanocomposites, self-assembling Zn nanostructured networks were coated with a layer of dispersed MWCNTs and subjected to thermal oxidation. The resulting ZnO-MWCNT hybrid nanostructured networks were encapsulated in commercially available epoxy adhesive. It was found that encapsulation of ZnO-MWCNT hybrid networks in epoxy adhesive resulted in a simultaneous decrease in their electrical resistance by a factor of 20-60 and an increase in the Seebeck coefficient by a factor of 3-15, depending on the MWCNT content. As a result, the thermoelectric power factor of the epoxy-encapsulated ZnO-MWCNTs hybrid networks exceeded that of non-encapsulated networks by more than 3-4 orders of magnitude. This effect was attributed to the ZnO-epoxy interface's unique properties and to the MWCNTs' contribution. The processes underlying such a significant improvement of the properties of ZnO-MWCNT hybrid nanostructured networks after encapsulation in epoxy adhesive are discussed. In addition, a two-leg thermoelectric generator composed of epoxy-encapsulated ZnO-MWCNT hybrid nanocomposite as n-type leg and polydimethylsiloxane-encapsulated CuO-MWCNT hybrid nanocomposite as p-type leg characterized at room temperatures showed better performance at temperature difference 30 °C compared with the similar devices, thus proving the potential of the developed nanocomposites for applications in domestic waste heat conversion devices.