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<p>Geopolymer materials are promising candidates for high-temperature thermal energy storage (TES) systems; however, their long-term reliability under repeated thermal cycling remains a critical challenge due to progressive microcracking, pore coarsening, and strength degradation. In this study, a multiscale reinforcement strategy using nano-silicon carbide (SiC) particles and reduced graphene oxide (rGO) nanosheets, combined as a nano-SiC functionalized rGO hybrid, was developed to address cyclic thermo–chemo–mechanical instability in one-part fly ash-based geopolymers exposed to 800&#xa0;°C for up to 100 heating–cooling cycles. Four systems were evaluated: control (G), G-rGO, G-SiC, and hybrid G-SiC-rGO. The control geopolymer lost ~40% compressive strength after 100 cycles, whereas the hybrid composite retained 85% (58.4 ± 2.9&#xa0;MPa initial, 49.6 ± 3.0&#xa0;MPa residual). Fracture toughness of the hybrid reached 1.68&#xa0;MPa·m1⁄2 and remained 1.53&#xa0;MPa·m1⁄2 post-cycling. Thermal conductivity improved from 0.55 to 1.10 W·m⁻<sup>1</sup>·K⁻<sup>1</sup> with &gt;98% retention; specific heat capacity stayed at ~0.92–0.95&#xa0;J·g⁻<sup>1</sup>·K⁻<sup>1</sup>. Dilatometry showed reduced thermal strain, and pore-structure analyses confirmed pore refinement in reinforced systems. FT-IR, <sup>29</sup>Si NMR, and XPS revealed increased Q<sup>4</sup>/Q<sup>3</sup> ratios, indicating enhanced gel cross-linking. Acoustic emission events decreased by 64%, and post-cycling SEM showed a dense, microcrack-free matrix. The synergistic reinforcement—rGO bridging nanoscale cracks and forming conductive pathways, while nano-SiC pins microcracks and reduces thermal expansion—yields a geopolymer composite with excellent strength retention, thermal stability, and durability for high-temperature TES applications.</p>

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High-temperature damage evolution and thermal performance of nano-SiC functionalized rGO geopolymers under repeated heat cycling

  • 期刊论文

  • 发表日期：

    2026年8月4日

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  • Nanthini Murugesan,
  • Raja Mariyasoosai Arulraj,
  • Jaganathan Venugopal

摘要

Geopolymer materials are promising candidates for high-temperature thermal energy storage (TES) systems; however, their long-term reliability under repeated thermal cycling remains a critical challenge due to progressive microcracking, pore coarsening, and strength degradation. In this study, a multiscale reinforcement strategy using nano-silicon carbide (SiC) particles and reduced graphene oxide (rGO) nanosheets, combined as a nano-SiC functionalized rGO hybrid, was developed to address cyclic thermo–chemo–mechanical instability in one-part fly ash-based geopolymers exposed to 800 °C for up to 100 heating–cooling cycles. Four systems were evaluated: control (G), G-rGO, G-SiC, and hybrid G-SiC-rGO. The control geopolymer lost ~40% compressive strength after 100 cycles, whereas the hybrid composite retained 85% (58.4 ± 2.9 MPa initial, 49.6 ± 3.0 MPa residual). Fracture toughness of the hybrid reached 1.68 MPa·m1⁄2 and remained 1.53 MPa·m1⁄2 post-cycling. Thermal conductivity improved from 0.55 to 1.10 W·m⁻1·K⁻1 with >98% retention; specific heat capacity stayed at ~0.92–0.95 J·g⁻1·K⁻1. Dilatometry showed reduced thermal strain, and pore-structure analyses confirmed pore refinement in reinforced systems. FT-IR, 29Si NMR, and XPS revealed increased Q4/Q3 ratios, indicating enhanced gel cross-linking. Acoustic emission events decreased by 64%, and post-cycling SEM showed a dense, microcrack-free matrix. The synergistic reinforcement—rGO bridging nanoscale cracks and forming conductive pathways, while nano-SiC pins microcracks and reduces thermal expansion—yields a geopolymer composite with excellent strength retention, thermal stability, and durability for high-temperature TES applications.