Synthesis, characterization, thermophysical properties and shape stability of paraffin/CNTs nanocomposite phase change materials

Paraffin/carbon nanotube (Pa/CNTs) nanocomposite with different CNTs lengths was prepared in order to investigate the change of thermophysical properties of paraffin phase change material (PCM). For this purpose, CNTs were first treated with sulfuric and nitric acids, which reduced the length of CNTs. Then, for complete dispersion of CNTs in paraffin, secondary functionalization was done using dodecylamine and they were added to paraffin with different wt.%. In order to stabilize the shape of paraffin, composites were inserted into graphene aerogel by vacuum impregnation method. Experiments showed that with the increase in the wt.% of CNTs, the thermal conductivity of composites increases, and the highest increase of 26.92% was observed for the composite containing 1 h refluxed CNTs with 1.2 wt.% in solid paraffin. Also, with an increase in the wt.% of CNTs, the latent heat of melting and solidifying of the composite increased, but the specific heat decreased. The absorption capacity of paraffin by graphene aerogel was investigated and the maximum absorption capacity was observed for the composite containing 1 h refluxed CNTs with 0.6 wt.% which showed 36.11% increase compared to the pure paraffin. In addition, by performing the leakage test, it was observed that the GA/Pa/CNTs structure has very good shape stability.