Stability of rGO-zirconia reinforced one-part geopolymers under cyclic high temperatures for thermal energy storage applications

Thermal energy storage systems require materials that can withstand repeated high-temperature exposure without significant degradation. This study evaluates one-part fly ash geopolymer composites reinforced with reduced graphene oxide (rGO) nanosheets and zirconia (ZrO2) particles under 100 thermal cycles up to 800°C. The hybrid composite achieved a compressive strength of 58.4 MPa, retaining 85% of its initial strength after cycling, compared to only 60% retention in the control sample. Fracture toughness increased from 0.75 to 1.68 MPa·m1/2, while thermal conductivity improved from 0.55 to 0.78 W·m−1 ·K−1. Microstructural analysis revealed reduced crack density and pore refinement in the hybrid system. These improvements demonstrate that rGO-ZrO2 reinforcement effectively mitigates thermal degradation, offering a durable material solution for high-temperature thermal energy storage applications.