Binder jetting additive manufacturing of hierarchical structural SiC_w/SiC composites

SiC-based composites have a wide range of applications in thermostructural filed. It is of great significance to accurately manufacture high-performance SiC whisker-reinforced SiC matrix composites (SiC_w/SiC). Binder jetting (BJ) is an additive manufacturing method that can prepare complex-shaped whisker preforms in near-net-size. Reactive melt infiltration (RMI) method can prepare highly dense matrix without shrinkage of composites. Currently, the preparation technology of SiC_w/SiC using the combination of BJ and RMI has the challenges of low whisker volume fraction, irrational whisker distribution, and high residual silicon content in matrix. A combination process of spray drying and chemical vapor infiltration (CVI) was developed to shape one-dimensional SiC_w into SiC_w composites microspheres (SiC_w-CMS), which significantly improves the volume fraction and flowability of SiC_w. Based on the SiC_w-CMS, a novel hierarchical structural SiC_w/SiC was designed. Also, through constructing reasonable infiltration channels of liquid silicon, the content of residual silicon in SiC_w/SiC was reduced to 5.2 vol%. As a result, the flexural strength and fracture toughness of the SiC_w/SiC can reach 385 MPa and 5.93 MPa·m^1/2, respectively. The SiC_w/SiC also shows low coefficient of thermal expansion of 4.0–5.4 × 10⁻⁶ K⁻¹, high thermal conductivity of 110.4 W/(m·K), and appropriate resistivity (7.09 Ω·cm). The hierarchical structural SiC_w/SiC is expected to be a candidate for future thermal structural materials.