Influence of ZrO₂ on microstructure regulation and performance enhancement of silica-based ceramic cores via an in situ reaction pathway

Silica-based ceramic cores have shown great potential for aero-engine applications owing to their excellent thermal stability and facilitation of efficient demoulding. However, their widespread application is still limited by the inherent drawback of insufficient mechanical strength. In this study, high-strength silica-based ceramic cores were fabricated by adding nano-ZrO₂, and the influence mechanisms of nano-ZrO₂ on the slurry flow behavior, phase composition evolution, and mechanical properties were systematically investigated via a combination of structural characterization and first-principles calculations. Results indicate that the high specific surface area of nano-ZrO₂ particles and the extensive hydrogen-bonding network formed by their surface hydroxyl groups lead to a significant increase in slurry viscosity with the increase of nano-ZrO₂ content. Furthermore, the flexural strengths of the green and sintered bodies reach maximum values of 9.5 MPa and 45.08 MPa, respectively, at a nano-ZrO₂ content of 5 wt%. For the sintered bodies, the observed mechanical enhancement is attributed to the synergistic effect of stress-induced t-ZrO₂ transformation and strengthening by the in situ formed ZrSiO₄. First-principles calculations indicate that ZrSiO₄ possesses a low binding energy (-9.27 eV) and a high elastic modulus (244.3 GPa), which supports its effectiveness as a reinforcing phase at the atomic scale. This study provides promising approaches and a theoretical basis for the fabrication of high-strength ceramic cores for turbine blade applications.