Customizing 3D thermally conductive skeleton by 1D aramid Nanofiber/2D graphene for high-performance phase change composites with excellent solar-to-thermal conversion ability

Three-dimensional (3D) graphene skeletons show the high potential using in encapsulation of phase change materials (PCM), yet still suffer from the high contact thermal resistance between graphene sheets in skeleton. In this work, aramid nanofiber (ANF) with high molecular chain orientation and rigid conjugate aromatic structure was firstly used to assemble graphene nanoplates (GNP) into a 3D thermally conductive skeleton. Typically, ball -milling treatment was used to improve the interfacial interaction between ANF and GNP, followed by unidi-rectional freezing technique was used to achieve 3D ANF/GNP skeleton with highly oriented honeycomb-like porous structure. As an encapsulation for PCM, ANF/GNP skeleton not only provides the thermal conduction path, but also endows excellent solar-thermal conversion ability, which greatly expands the application in solar energy utilization. Thus, the thermal conductivity of PCM composite can reach to 3.9 W/mK at only 4.26 vol% of GNP content, which gives the composite with rapid and stable heat charging/discharging ability during phase change process. Moreover, the honeycomb channel structure of ANF/GNP skeleton with huge capillary and surface tension forces not only reinforce the shape stability during phase change process, but also accommodate sufficient PCM for energy storage. Therefore, this work demonstrates the high-efficiency of ANF in constructing 3D thermally conductive graphene skeleton, which reveals a high potential using in encapsulating PCM.