Synergistic Thermal Conductivity Enhancement in Geopolymer–Graphene Aerogel Composites Through 3D Structuring and Gelation Kinetics

To overcome the inherent drawback of low thermal conductivity (0.3 W/m·K) in conventional thermoplastic polymers, this work reports a scalable synthesis of cost-effective, thermally stable geopolymers using waste fly ash (FA) as a precursor material. By synergistically tailoring the Si/Al ratio and incorporating graphene oxide, a three-dimensional percolative thermal conductive network is engineered to dramatically enhance the thermal conductivity of geopolymer–graphene aerogel composites. Experimental results show that optimizing the Si/Al ratio effectively improves the matrix performance. With the optimal Si/Al ratios of 1.35 and 1.50, the thermal conductivities of the geopolymer reach up to 1.03 and 1.14 W/m·K, respectively, representing a nearly 245% increase over conventional polymers. Notably, the further introduction of ultra-low content of thermal conductive graphene aerogel filler (0.34 wt%) with a regulated Si/Al ratio of 1.64 results in a 34.2% increase in the thermal conductivity of the composite, achieving an exceptional specific improvement (thermal conductivity improvement/filler content) of 100.7%. Moreover, these composites maintain 75.5% of their initial conductivity at high temperature (100°C), demonstrating robust thermal stability. This breakthrough enables efficient thermal management for miniaturized electronic systems using ultra-low loading of high-performance fillers.