Air-dried, high-density graphene hybrid aerogels for phase change composites with exceptional thermal conductivity and shape stability

Abstract

High density graphene hybrid aerogels with enhanced thermal conductivity and compressive properties are fabricated by self-assembly of aqueous mixtures of graphene oxide and high-quality graphene nanoplatelets (GNPs) followed by a convenient and cost-effective air drying process. The reduced graphene oxide sheets form an integrated three-dimensional network to accommodate GNPs, while the GNPs act as reinforcements to avoid excessive volume shrinkage of the network during the air drying process. Octadecanol is thus easily impregnated into the porous graphene network to obtain octadecanol/graphene phase change composites (PCCs) with exceptional thermal conductivities. The PCC with 12 wt% graphene exhibits a thermal conductivity of ∼5.92 W m⁻¹ K⁻¹ that is 26-fold higher than that of neat 1-octadecanol while maintaining a high latent heat of fusion (∼202.8 J g⁻¹). Even when compressed by a high weight at ∼70 °C, the PCC still retains shape stability without any leakage. Such abilities to endow PCCs with exceptional shape stability and to boost their thermal conductivity by an order-of-magnitude without incurring a significant loss in the heat of fusion are important attributes in enabling their practical application as latent heat storage/release units for thermal management and thermal protection.