Enhancing the solid phase content and mechanical properties of SiC ceramics via stereolithography apparatus using silane-modified alumina coatings

Abstract

The promising application of SiC ceramics in aerospace, semiconductors, and the related fields is enabled by stereolithography apparatus (SLA) technology. However, the curing thickness and solid content are limited by the high absorbance of SiC powder, the mechanical properties of the printed parts are adversely affected. A synergistic surface modification strategy combining silane coupling agent treatment and sol-gel Al₂O₃ coating was proposed. Based on the Krieger-Dougherty (KD) theoretical framework, a general rheological model was established. By introducing the concept of effective hydrodynamic volume, the intrinsic relationship between particle surface coating thickness and intrinsic viscosity was quantitatively revealed for the first time. Model predictions indicate that for a coating thickness of 1 μm and a particle radius of 10 μm, the model predicted a theoretical intrinsic viscosity of [η] = 3.33 and a maximum packing fraction of ϕ_m = 53.4%. This prediction is in excellent agreement with experimental viscosity data within the 44%-52% solid content range, confirming the model's general applicability and predictive accuracy. Using an optimized silane content of 2 wt%, Al₂O₃-coated SiC composite powder was obtained, enabling a ceramic slurry with a solid loading of 50%, a viscosity of 2.8 Pa s (30 s⁻¹), and a curing thickness of 140 ± 9 μm. The sintered SiC ceramic composites achieved a density of 2.74 g/cm³, a flexural strength of 159 ± 13 MPa, and an elastic modulus of 82 ± 6 GPa. This study establishes a quantitative framework linking the surface coating of SiC particles to the rheological behavior of the slurry, providing a universal method for SLA printing of high-performance non-oxide ceramics.