Significantly toughened SiC foams with enhanced microwave absorption via in situ growth of Si3N4 nanowires

Porous ceramic materials with high electromagnetic absorption capacity, low density, high thermal resistance and excellent mechanical properties are highly desirable in aerospace applications. Here, we synthesized one type of hierarchical SiC composite foams with in situ grown Si 3 N 4 nanowires via a pyrolysis process. The existence and structure of Si 3 N 4 nanowires were characterized by multiple techniques and analysis revealed that the growth of nanowires was based on a typical vapor-solid mechanism. Owing to the presence of a large amount of Si 3 N 4 nanowires, both the mechanical performance and electromagnetic absorption were significantly enhanced. The minimum Reflection loss (RL) of 1.25 mm SiC composite foam reaches −50.3 dB at 16.48 GHz with an effective bandwidth (RL < −10 dB) of 3.6 GHz (14.4–18 GHz), while the toughness and specific compressive strength increased by 356% and 126%, respectively. Especially, a ductile and steady fracture behavior was observed for the mechanically enhanced composite foam, rather than the typical catastrophic failure usually seen for ceramic materials. Owing to the excellent electromagnetic wave absorption capability and enhanced mechanical properties, as well as low density and high thermal resistance, this type of composite ceramic material may find applications in aviation, aerospace and other extreme environments.