Multifunctional Graphene Aerogel with Bubble-Induced Hierarchical Porosity for Acoustic Absorption, Thermal Insulation and Wearable Sensing

Graphene aerogels are lightweight porous materials with strong potential for sound absorption, thermal insulation, mechanical damping, and flexible sensing. However, their practical use is limited by weak mechanical stability, structural shrinkage, poor recovery after deformation, and difficulty in controlling multiscale pores. To address these issues, a bubble-induced rGO/ANF/PVA graphene aerogel system was developed. In this system, rGO forms the conductive porous framework, ANF reinforces the structure, and PVA acts as a flexible binder to stabilize the network. The aerogels were prepared by mixing GO, ANF, and PVA solutions, followed by high-speed shear homogenization to introduce air bubbles into the suspension. The bubble-containing mixture was then processed by unidirectional freeze casting at −60 °C, freeze dried for 72 h, and thermally annealed at 400 °C using a slow-ramp strategy to obtain reduced rGAP aerogels. This process produced a hierarchical porous structure containing large bubble-derived macropores, aligned ice-templated pores, and smaller interconnected pores within the pore walls. The composition strongly influenced the final properties. The graphene-dominated rGAP1 aerogel, with a GO/ANF/PVA ratio of 2:1:1, showed porosity above 99%, a low density of 3.28 mg cm⁻³, a compressive modulus of about 64 kPa, and a specific energy absorption of about 290 kJ kg⁻¹. In contrast, the PVA-rich rGAP6 aerogel, with a ratio of 1:1:8, reached a compressive modulus of about 300 kPa and a specific energy absorption close to 1100 kJ kg⁻¹. The 30 mm rGAP6 sample showed the best acoustic performance, with an NRC of about 0.67 and a mean sound absorption coefficient of about 0.93. The aerogels also showed low thermal conductivity, hydrophobicity, stable sensing over 1000 compression cycles, and good flame resistance.