Preparation and thermophysical characterisation analysis of potential nano-phase transition materials for thermal energy storage applications

The efficacious use of phase change materials (PCMs) is mainly confined by their poor thermal conductivity (TC). In this study, multiwalled carbon nanotubes (MWCNTs), graphene nanoplatelets (GNP) and titanium oxide (TiO2) based single, and novel hybrid nano additives were incorporated into paraffin, a typical PCM, to find the optimal composite which could not only enhance the thermal conductivity but also limit the latent heat. Both unitary and hybrid nanoparticles at five different concentrations (0.2, 0.4, 0.6, 0.8 & 1.0 wt.%) were investigated using various characterisation techniques, including FT-IR, XRD, DSC, TGA, and TC apparatus. The results depicted good intermolecular interactions between the PCM and the nanoparticles and showed that the dispersion of nanoparticles within the PCM did not affect the chemical structure of pristine paraffin but enhanced its thermal and chemical stability. Novel hybrid nanocomposites were found to be more stable and exhibit better thermal performance than single nanocomposites. The highest value of thermal conductivity was observed at 1.0 wt.% of GNP+MWCNTs hybrid particles based PCM with a maximum enhancement of 170% at 25 °C. However, compared with single and hybrid carbon-based nanofillers, TiO2 based mono and hybrid nano-PCM showed a minimum reduction in the latent heat with a maximum decrease of -3.7%, -5.2%, and -5.5% at 1 wt.% of TiO2, TiO2+GNP and TiO2+MWCNTs, respectively. The significant improvement in the thermal properties of PCMs with the inclusion of these nanofillers indicates that they have the potential to be employed in thermal energy storage applications.