Optimizing AlN hydrolysis process to fabricate coated modified powders for improving the properties of Si3N4/SiAlON ceramics prepared by Vat Photopolymerization

The preparation of complex structural parts of Si₃N₄ and its composite ceramics using conventional methods is difficult. The Vat Photopolymerization (VPP) technique is regarded as an effective method for the preparation of ceramic materials. However, due to the high absorption of ultraviolet (UV) light and high refractive index of Si₃N₄, it is challenging to realize its complex structure via VPP technique. AlN and Si₃N₄ can be compounded to form SiAlON phase, and AlN powders can be hydrolyzed to produce Al(OH)₃ that can be easily dehydrated. In this study, Si₃N₄@Al₂O₃ and AlN@Al₂O₃ powders were prepared by mixing Si₃N₄ and AlN powders by hydrolysis. Subsequently, Si₃N₄/SiAlON composite ceramics were prepared by VPP. With the addition of 10 vol% AlN, the viscosity of ceramic slurry was found to be 0.50 Pa·s. Furthermore, the curing depth was observed to reach 49.46 ± 2.15 μm at 800 mJ/cm². The sintered ceramics exhibited the formation of the excellent β-Si₃N₄/β-SiAlON phase. The relative density, bending strength, hardness, fracture toughness and thermal conductivity was determined to be 92.61 ± 2.51 %, 402.91 ± 9.61 MPa, 21.11 ± 0.61 GPa, 6.33 ± 0.25 MPa·$m^{\frac{1}{2}}$ and 33.17 ± 1.01 W·m⁻¹·K⁻¹, respectively. This study introduces a novel approach to cladding modification of Si₃N₄ and AlN, as well as the preparation of Si₃N₄/SiAlON composite ceramics with exceptional properties via VPP.