Strong and Tough Porous Silicon Carbide Ceramics

Porous silicon carbide (SiC) ceramics are considered promising materials for structural applications under severe conditions. However, the inadequate mechanical strength and fracture toughness restrict their further applications. Here, we report the development of strong and tough porous SiC ceramics with highly cross-linked SiC nanowire networks as reinforcements. To be specific, a hot-pressing technique is used to dramatically increase the cross-linking of SiC nanowire networks, followed by chemical vapor infiltration to coat the nanowires with pyrolytic carbon (PyC) nanolayers, as well as precursor infiltration and pyrolysis to introduce a SiC matrix. The resulting porous ceramics exhibit impressive mechanical performance including a flexural strength of 187 MPa, a compressive strength of 215 MPa, a fracture toughness of 3.4 MPa·m^1/2, and an energy absorption capability of 19.2 MJ·m^-3 at a relatively high porosity of 43%. The highly cross-linked nanowire networks facilitate multiple strengthening and toughening mechanisms, such as nanowire-induced crack deflection, as well as bridging, interfacial sliding, and pull-out of the nanowires. This work demonstrates a versatile strategy for simultaneously improving the strength and toughness of porous ceramics.