Study on the compressed ion layer and the specific heat of the phase change materials doping charged single-walled carbon nanotubes

In this paper, the thermal effect of charged single-walled carbon nanotubes (SWCNT) exerting with the molten carbonate salt phase change materials are investigated through molecular dynamics (MD) simulation. The results show that the surface charge of the SWCNT can affect the compressed ion layer surrounding the SWCNT, and in turn affect the specific heat (Cp) enhancement for the nanoparticle-enhanced phase change materials (NPCM). First, the ions inside the compressed ion layer are found to be redistributed and Li⁺, K⁺ and CO3^2- are all denser than the bulk. Moreover, the absorption of the ions inside the compressed ion layer can be significantly affected by changing the surface negative charge. The SWCNT surface charge can in turn stimulates enrichment of positive and negative charges, and in turn results in greater pairwise energy. As a consequence, the enrichment of positive and negative charges is supposed to be the main reason for the enhancement on Cp of the NPCM. The specific heat capacity of the NPCM are investigated and the results show that Cp is enhanced by adding the charged SWCNT. It is shown that SWCNT carrying negative charges possesses the best ability to enhance Cp of carbonate salts and the enhancement can be up to 19.16%. The conclusions provide a theoretical basis for the application of charged nanoparticles in enhancing the thermal property of PCM.