Enhanced thermal conductivity of microencapsulated phase change materials based on graphene oxide and carbon nanotube hybrid filler

Large energy storage capacity and high thermal charging/discharging rate are crucial for microencapsulated phase change materials (MEPCM) in thermal energy storage application. The microcapsules with dodecanol core and melamine-formaldehyde (MF) resin shell modified by graphene oxide (GO) and carbon nanotube (CNT) hybrid filler were prepared via in-situ polymerization. The effect of the combination of GO and CNT on morphology and thermal properties of the microcapsules was investigated, and the mechanism for heat transfer enhancement was further studied from both macroscopic and microscopic views. The results indicated that the addition of GO and CNTs largely enhanced the thermal conductivity of the microcapsules, and the GO-CNT hybrid filler was superior to individual GO or CNT. Particularly, with a hybrid filler loading of 0.6 wt%, the thermal conductivity of the microcapsule was improved by 195% with the latent heat slightly decreased. The prepared microcapsules were dispersed into water to form a latent functional thermal fluid, and its photo-thermal conversion performance was studied. The excellent thermal properties and photo-thermal conversion performance made the microcapsule dispersed slurry a potential fluid in direct absorption solar collectors.