High-performance B4C matrix composites fabricated from the B4C-Si-CeO2 system via reactive hot pressing

Boron carbide (B4C) matrix composites had the advantages of high hardness, high melting point and low density. However, due to the low relative density and poor fracture toughness of B4C, its comprehensive properties were limited in engineering applications. In this work, in order to improve the comprehensive properties of B4C composites, B4C-SiC-SiB6-CeB6 composites were designed and fabricated via reactive hot pressing at 2050 C and 20 MPa with B4C matrix and novel additives (Double doping of Si and CeO2) as raw materials. The effects of additive CeO2 content on the microstructures and mechanical properties of composite were investigated, and reaction mechanisms of B4C, Si and CeO2 at different temperatures were studied in detail. The work showed that liquid phase Si and SiB6 greatly improved the densification of composites. CeB6 played an indispensable role in the formation of SiC-SiB6 agglomerate structure, increasing strength and supplementing toughness. When the content of CeO2 was 6 wt%, the relative density, hardness, flexural strength and fracture toughness reached to 99.7%, 34.9 GPa, 461.46 MPa and 5.57 MPa m(1/2), respectively. Our strategy benefited from the formation of two liquid phases and SiC-SiB6 agglomerate structure, showing great potential in promoting sintering and improving fracture toughness.