Investigation of the thermal properties of phase change materials encapsulated in capped carbon nanotubes using molecular dynamics simulations.

Due to the high demand for clean, economic, and recyclable energy, phase change materials (PCMs) have received significant attention in recent years. To improve the performance of PCMs, they are confined in micro- and nano-capsules composed of organic or inorganic materials. In this study, encapsulated phase change material (EPCM) systems were constructed with paraffin molecules as the core material and capped carbon nanotubes (CNTs) as the shell. We investigated the effects of different parameters including CNT diameter, length, and chirality and the length of the alkane molecule chain. We also investigated metal nanocluster-enhanced PCM systems via the addition of Cu, Ag, and Al clusters to the EPCM systems. Different thermodynamic, dynamic, and structural properties including configurational energy, melting range, mean square displacement, self-diffusion coefficient, radial distribution function (RDF), and average end-to-end distance of the confined molecules were examined. We also investigated the effect of metal doping in CNT on the different properties of the confined PCM. The results indicated that a longer CNT has a lower melting point than the normal CNT system. It was also observed that the bigger (30,0) CNT, (14,14) armchair CNT, and icosane systems have higher melting ranges than the normal (25,0) system. The metal cluster systems also have a lower starting melting point than the normal system. Furthermore, it was found that the Al cluster system has the lowest starting melting point among the studied systems.