Temperature-field assisted vat photopolymerization (TF-VPP) fabrication of high-strength, low-shrinkage silica-based ceramic cores: effects of spherical powders and vacuum debinding

Vat photopolymerization (VPP) encounters difficulties in fabricating high-strength, low-shrinkage ceramic cores with high-precision and high quality using high-solid-loading, high-viscosity slurries. This study developed a high-solid-loading (71 vol%) silica-based ceramic slurry using spherical powders. Notably, spherical particle slurry presents favorable Newtonian fluid behavior, effectively inhibiting interlayer stair-stepping effect and large pore formation. The proposed uniform temperature field-assisted vat photopolymerization (TF-VPP) method reduced the slurry viscosity from 103.4 Pa·s at 25°C to 8.6 Pa·s (100s^-1) at 55°C. It simultaneously achieved uniform stair-stepping effects in the TPMS structure and high-precision fabrication of fine micropore features (minimum size: 50 μm). The temperature field mitigated residual stresses in ceramic green bodies, enhanced interlayer bonding and apparent Young's modulus. Compared with air debinding, the vacuum debinding and sintering process suppresses the formation of the ZrSiO₄ phase while promoting densification. The average porosity and Z-axis shrinkage were approximately 20.03% and 4.43%, respectively. The average room-temperature (25°C) and high-temperature (1550°C) flexural strength reached 12.43 MPa and 22.56 MPa, respectively, representing substantial improvements of 36.4% and 61.6%. According to CT pore characterization, core samples fabricated via vacuum debinding primarily feature small pores, without noticeable cracks. With 71vol% spherical powder slurry, the proposed TF-VPP coupled with vacuum debinding fabricates large-size (108.71mm) silica-based ceramic cores featuring low shrinkage and superior comprehensive properties. Moreover, this integrated approach offers a systematic framework for the high-precision printing of ultra-high-solid-loading ceramic slurries and for defect-free ceramic sintering.