Studies on graphene-based high modulus foams and low melting alloy-based shape stable phase change materials

Abstract

Nanocarbon-based porous materials have been widely used to improve the thermal conductivity and shape stability of phase change materials (PCMs). Low melting alloys are a new class of promising PCMs, and they are challenged by low shape stability during phase transition process. Normal nanocarbon-based porous materials are not strong enough to load low melting alloys due to the high density of alloys. Here, we prepared graphene-based strong foams by a multi-cycles immersing-drying method to address this problem. The foams had low density (0.12 g/cm3), high compressive strength (>400 KPa), high compressive modulus (highest: 95.3 MPa), extremely high specific compressive modulus (1560 MPa·cm3/g), high thermal conductivity (76 mW/mK), and quasi-closed cell structures. The mechanical enhancements were mainly attributed to a capillary force-based self-tightening mechanism. The forms could effectively load low melting alloys, resulting in composite PCMs with high thermal conductivity (~10 W/mK), high volumetric latent heat (150–250 MJ/m3), high shape stability, and high heat sink performance.