Ultralow-density carbon foam composites with bean-like Co-embedded carbon nanotube whiskers towards high-performance microwave absorption

Abstract

We describe the design and fabrication of an ultralight carbon foam composite with special bean-like Co-embedded carbon nanotube whiskers used for high-performance microwave absorption materials. A facile approach was developed to create this carbon foam with the self-growth of carbon nanotubes on low-cost cobalt-decorated commercial melamine sponges (MF) via a simple thermal annealing process. It was found that a large number of bean-like carbon nanotubes whiskers (1D) embedded with Co nanoparticles (0D) grew on the surface of carbon skeleton (3D) under the action of surface autocatalysis. This unique hierarchical micro/nanostructure not only reduced the density of the materials but also effectively improved their thermal oxidation stability and microwave absorption ability. The resultant foam showed an excellent microwave absorption performance with the combined advantages of ultralow density (9.4 mg/cm3), strong absorption (minimum reflection loss value of −46.2 dB), wide absorption width (4.8 GHz), and high thermal oxidation stability (>350 °C). The RL values of the foam could be all below −10 dB at the frequency from 4 to 18 GHz covering 87% of the whole test frequency range. These remarkable results also provide a potentially scalable, simple, and cost-effective strategy for designing metal-embedded carbon composite nanostructures for catalysis, electrochemistry, and other applications.