In situ self-catalyzed growth of Ni-N co-doped carbon nanotubes on carbon foam with engineered heterointerfaces for...

In recent years, constructing hierarchical heterostructures and integrating dielectric-magnetic components have emerged as a promising approach for improving the microwave absorption (MA) properties of materials. In this work, we propose a facile hierarchical composite strategy in which Ni ions are first adsorbed on the skeleton surface of three-dimensional (3D) melamine foam (MF), followed by a subsequent carbothermal reduction and pyrolysis process that converts nickel oxide into metallic nickel and, meanwhile, self-catalyzes the growth of N-doped carbon nanotubes (NCs) encapsulating Ni nanoparticles (NPs) on MF-derived carbon foam (CF), ultimately yielding a 3D heterostructured Ni-NC@CF composite. By tuning the Ni ion concentration, the morphology of the grown NC can be regulated, thereby influencing MA performance of the products. The suitable composition and unique 3D hierarchical architecture endow the optimized Ni-NC@CF composite with excellent MA performance, achieving a minimum reflection loss of -63.65 dB at a thickness of 2.3 mm and a maximum effective absorption bandwidth of 4.64 GHz at 1.6 mm. This can be ascribed to the improved impedance matching and balanced dielectric and magnetic losses, together with the synergetic effect of multiple electromagnetic wave (EMW) dissipation mechanisms induced by multi-heterogeneous interfaces, abundant N-doped sites and defects, a 3D conductive porous carbon framework and small magnetic Ni NPs. Moreover, the composite also demonstrates good radar and infrared stealth performance. Overall, this work not only provides a promising candidate for efficient EMW absorption and stealth applications but also offers a practical approach for developing advanced EM materials by multi-heterogeneous engineering.