Microstructure refinement-homogenization and flexural strength improvement of Al₂O₃ ceramics fabricated by DLP-stereolithography integrated with chemical precipitation coating process

In this study, the chemical precipitation coating (CP) process was creatively integrated with DLP-stereolithography based 3D printing for refining and homogenizing the microstructure of 3D printed Al₂O₃ ceramic. Based on this novel approach, Al₂O₃ powder was coated with a homogeneous layer of amorphous Y₂O₃, with the coated Al₂O₃ powder found to make the microstructure of 3D printed Al₂O₃ ceramic more uniform and refined, as compared with the conventional mechanical mixing (MM) of Al₂O₃ and Y₂O₃ powders. The grain size of Al₂O₃ in Sample CP is 64.44% and 51.43% lower than those in the monolithic Al₂O₃ ceramic and Sample MM, respectively. Sample CP has the highest flexural strength of 455.37±32.17 MPa, which is 14.85% and 25.45% higher than those of Samples MM and AL, respectively; also Sample CP has the highest Weibull modulus of 16.88 among the three kinds of samples. Moreover, the fine grained Sample CP has a close thermal conductivity to the coarse grained Sample MM because of the changes in morphology of Y₃Al₅O₁₂ phase from semi-connected (Sample MM) to isolated (Sample CP). Finally, specially designed fin-type Al₂O₃ ceramic heat sinks were successfully fabricated via the novel integrated process, which has been proven to be an effective method for fabricating complex-shaped Al₂O₃ ceramic components with enhanced flexural strength and reliability.