Microstructural Characterization and Hydrothermal Ageing Resistance of Rice Husk Silica-Doped Alumina Toughened Zirconia Biocomposite

This study investigates the influence of amorphous and crystalline silica derived from rice husk (RH), a sustainable agricultural waste, on the phase composition, microstructure, hydrothermal ageing resistance, mechanical properties, and biocompatibility of Alumina Toughened Zirconia (ATZ) biocomposites. The research supports the bio-circular economy by valorizing rice husk-derived silica as a functional additive in high-performance ceramics. Comprehensive characterization was conducted using X-ray diffraction (XRD), scanning electron microscopy (SEM), mechanical testing, hydrothermal ageing, and in vitro bioactivity assessments. Results show that both amorphous and crystalline silica improve ageing resistance, with 1 wt% RHA-derived silica yielding optimal mechanical and ageing properties in both cases. However, amorphous silica outperforms crystalline silica in enhancing flexural strength due to enhanced compaction. At concentrations beyond 1 wt%, a decline in mechanical performance is observed, although ageing resistance remains improved due to the formation of a protective glassy phase. This work highlights the comparative advantages of amorphous silica and reinforces the viability of RH-derived materials in advancing bio-circular and eco-friendly ceramic technologies.