Graphene Aerogel Composites with Self‑Organized Nanowires‑Packed Honeycomb Structure for Highly Efficient Electromagnetic Wave Absorption

With vigorous developments in nanotechnology,the elaborate regulation of microstructure shows attractive potential in the design of electromagnetic wave absorbers.Herein,a hierarchical porous structure and composite heterogeneous interface are constructed successfully to optimize the electromagnetic loss capacity.The macro–micro-synergistic graphene aerogel formed by the ice template‑assisted 3D printing strategy is cut by silicon carbide nanowires(SiC_(nws))grown in situ,while boron nitride(BN)interfacial structure is introduced on graphene nanoplates.The unique composite structure forces multiple scattering of incident EMWs,ensuring the combined effects of interfacial polarization,conduction networks,and magnetic-dielectric synergy.Therefore,the as-prepared composites present a minimum reflection loss value of−37.8 dB and a wide effective absorption bandwidth(EAB)of 9.2 GHz(from 8.8 to 18.0 GHz)at 2.5 mm.Besides,relying on the intrinsic high-temperature resistance of SiC_(nws) and BN,the EAB also remains above 5.0 GHz after annealing in air environment at 600℃ for 10 h.

Effect of BNNTs/matrix interface tailoring on toughness and fracture morphology of hierarchical SiC_f/SiC composites

A thin BN interphase is applied on BNNTs surface to tailor the interfacial bonding between BNNTs and SiC matrix in hierarchical SiCf/SiC composites. The thickness of BN interphase ranging from 10 to 70 nm can be optimized by chemical vapor deposition after BNNTs are in situ grown on SiC fiber surface. Without BN interphase, the fracture toughness of hierarchical Si Cf/Si C composites can be impaired by 13.6% due to strong interfacial bonding. As long as BN interphase with 30–45 nm thickness is applied, the interfacial bonding can be optimized and fracture toughness of hierarchical composites can be improved by 27.3%. It implies that tailoring BNNTs/matrix interface by depositing a layer of BN interphase is in favor of activating energy dissipation mechanisms at nanoscale induced by BNNTs.