Binder jetting additive manufacturing of high-performance silicon carbide optical mirrors via graphite addition method

Binder jetting (BJ) additive manufacturing demonstrates significant potential in the fabrication of silicon carbide composites (Si/SiC) mirrors with arbitrary structures.However, the insufficient performance of BJ-prepared Si/SiC, primarily due to high residual silicon (Si) content, limits its application.Here, graphite addition method was proposed to reduce the residual Si content through dual mechanisms.Performance enhancement mechanisms were revealed that graphite, as the self-lubricating phase, improves the flowability of raw powders, which facilitates to reduce the content and size of residual Si.Additionally, β-SiC was formed by the reaction of residual Si and carbon during reactive melt infiltration (RMI) process.The results show that the density of Si/SiC was increased by 5.99% and the residual Si content was decreased by 18.18%.Notably, the flexural strength, elastic modulus and thermal conductivity reached 268.37 MPa, 329.93 GPa and 127.01 W/(m•K), respectively.The dimensional deviations throughout the entire process were -0.11% in length, -0.49% in width, and +0.28% in height.Finally, high-performance Si/SiC mirrors with complex structure were fabricated.Furthermore, the shape accuracy and surface roughness of the Si/SiC mirror were 12.05 nm RMS and 0.772 nm RMS.Therefore, this work manifested the feasibility of graphite addition method for the performance enhancement of BJ additive manufacturing optical Si/SiC mirrors.