Oxygen vacancy-driven redox mechanisms for enhanced thermo-oxidative stability of silicone rubber with Fe2O3, CeO2, and CeZrO2

초록

The thermal degradation of silicone rubber in high-temperature oxidative environments remains a critical challenge, yet the mechanistic role of oxygen vacancy engineering in cerium-based stabilizers has not been systematically explored. This study demonstrates that CeO2 and CeZrO2 (HRA-01) achieve superior stabilization through oxygen vacancy-mediated Ce-3(+)/Ce-4(+) redox cycling that couples radical scavenging with dynamic oxygen buffering, with zirconium incorporation further enhancing oxygen vacancy density and mobility. Consequently, under harsh aging at 250 degrees C for 200 h, whereas pristine PDMS exhibited catastrophic toughness loss (similar to 98.5 %) and Fe2O3 composites offered only partial mitigation (81-98.5 % loss), CeO2-filled and HRA-01 composites retained markedly higher toughness, limiting losses to 42-54 % and 40-50 %, respectively. Thermogravimetric analysis showed nearly constant residues for CeO2 and HRA-01 (31-32 %), in sharp contrast to the substantial increases in pristine and Fe2O3 systems. Beyond performance metrics, we elucidate the oxygen-vacancy-mediated stabilization mechanism: vacancy-enabled Ce-3(+)/Ce-4(+) redox cycling couples rapid radical scavenging with dynamic oxygen buffering, additionally, Zr incorporation increases vacancy density and mobility to suppress thermo-oxidative chain scission and uncontrolled crosslinking. These findings establish CeZrO2 as a next-generation stabilizer that will contribute to enhanced durability and extended service lifetimes of silicone rubbers in demanding industrial applications.

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