Effect of CNTs length on thermophysical properties of paraffin/CNTs/graphene aerogel nanocomposite as a shape stabilized phase change material

Abstract

In this work, paraffin/carbon nanotubes/graphene aerogel (Pa/CNTs/GA) nanocomposite with different CNTs lengths were synthesized. CNTs' length was changed by refluxing them in a mixture of acids for different times, by which the initial micrometer length of CNTs was reduced to 1200 and 205 nm after 0.5 and 1 h refluxing. To complete dispersing CNTs in paraffin, they were functionalized for the second time using dodecylamine. By inserting paraffin composites into the aerogel using vacuum impregnation, the thermal conductivity of the aerogel increases greatly. Melting and freezing latent heat of both samples of graphene aerogel composite containing 0.5 and 1 h refluxed CNTs was reduced compared to that of the pure paraffin and Pa/CNTs composite. The specific heat of the Pa/CNTs/GA composite containing 1 h refluxed CNTs was reduced compared to that of the Pa/CNTs (1 h refluxed) composite, but it was increased for the samples containing 0.5 h refluxed CNTs. Also, Pa/ZnO, Pa/TiO2, and Pa/Al2O3 composites were prepared and their thermophysical properties were compared with those of Pa/CNTs composites.