Enhanced curing behavior, mechanical and thermal properties of 3D printed aluminum nitride ceramics using a powder coating strategy

High refractive index and ultraviolet (UV) absorption of AlN powders make it challenging to use the digital light processing (DLP)-based vat photopolymerization (VPP) technology for fabricating AlN ceramic components with fine precision. In this work, powder coating strategy (PCS) was creatively integrated with DLP-based VPP to optimize the curing behavior and rheological of AlN ceramic suspensions and homogenize the microstructure of sintered AlN ceramics. This novel approach is in favor of the improvement of the rheological and curing characteristics of AlN suspensions. The viscosity of the PCS ceramic suspension at the shear rate of 100 s-1 was 57.0% lower than that of the BM suspension. The cure depths and broadening depth at the exposure energy of 120 mJ/cm2 for PCS ceramic suspension (with a 45 vol% solid loading) were 41.6% and 25.8% higher than those of the BM ceramic suspension, respectively, illustrating that the PCS is beneficial to enhance the 3D printing speed and accuracy of AlN ceramics. Moreover, the microstructure uniformity of the 3D-printed AlN ceramic can be improved by the novel approach as compared with the conventional ball-milled (BM) method. The thermal conductivity (144.11 W·m-1·K-1) and bending strength (400.07 ± 13.49 MPa) of Sample PCS were 7.44% and 9.72% higher than those of Sample BM, respectively, which was owing to the change in the second phase distribution from semi-connected (Sample BM) to isolated (Sample PCS) location. Finally, the integrated process successfully produced a fin-type AlN ceramic heat sink, demonstrating its effectiveness in manufacturing complex-shaped AlN ceramic components with exceptional thermal conductivity and mechanical properties.