Shell effect on microstructure and diffusion in interface region of nanoencapsulated phase change material: A molecular dynamics simulation

CY Zhao and YB Tao and WY Wang, JOURNAL OF MOLECULAR LIQUIDS, 354, 118872 (2022).

DOI: 10.1016/j.molliq.2022.118872

A new simplified molecular dynamics model of nanoencapsulated phase change material (NEPCM) is constructed to investigate the shell effect in the shell-core interface. The amorphous silica wall with different thicknesses were built as the nanocapsule shell and paraffin (octadecane) was dispersed as the nanocapsule core. By MD method, the atom distribution was revealed by the linear density. The linear density of paraffin was reduced close to the shell and yet augmented far away from the shell compared with the pure paraffin density. Orientation order parameter (S) was greatly enhanced close to the silica shell, revealing that molecules near the surface were more orderly and packed perpendicularly to the shell. End-to-end distance (r(e)) of each paraffin molecule was calculated and the distribution was revealed. The results showed the percentages of molecules fully stretched were more increased with the increasing shell thicknesses. S and r(e) both showed the changes of the internal structures in the cases with the silica shell. The results of diffusion properties showed the addition of the silica shell broke the symmetry of the systems and the PCM diffusion was significantly weakened. Overall, the work presents the microstructures of paraffin and provides explanations for the thermophysical properties from paraffin morphology. (C) 2022 Published by Elsevier B.V.

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