PVA-assisted graphene aerogels composite phase change materials with anisotropic porous structure for thermal management

The rapid development of spacecraft thermal control systems necessitates high-performance phase change materials (PCMs) with low density, high thermal conductivity and high enthalpy. Graphene aerogels (GAs) prepared by unidirectional freezing are ideal candidates as thermal conductive networks for PCMs due to the anisotropic porous structures. However, constructing anisotropic thermal conductive composite PCMs with low graphene aerogel loading while employing environmentally friendly cross-linking agents remains challenging. To fulfill the research gap, this study explores the synthesis of poly(vinyl alcohol) (PVA)/graphene aerogels (PGAs) by hydrothermal reaction and conventional freeze-drying. Anisotropic PGAs with oriented porous structures were fabricated by unidirectional freezing. After annealing and impregnation with paraffin wax, composite PCMs with excellent shape stability were obtained. The prepared composite exhibits low density (0.82 g cm⁻³) and high enthalpy (165 J g⁻¹). The combination of PVA and graphene enables the composite to achieve an ultralow graphene aerogel loading (0.85 wt%) while maintaining high thermal conductivity (1.37 W m⁻¹ K⁻¹), leading to a high specific thermal conductivity enhancement up to 477. This work sheds light on the potential of combing PVA and graphene to construct thermal conductive aerogels, intending to provide feasible means to develop high-performance PCMs for spacecraft thermal management.