Multi-dimensional ordered mesoporous carbon/silica@Ni composite with hierarchical nanostructure for strong and broadband microwave absorption

Ordered mesoporous carbon (OMC) has been regarded as a promising carbonaceous material for microwave absorption (MA) owing to its high specific surface area, sufficient ordered mesoporous nanostructures and easy decoration. However, its development in MA performance is seriously hampered by its shortcomings of lacking magnetic loss and poor impedance matching. Herein, a series of multi-dimensional ternary OMC/SiO₂@Ni composites with hierarchical nanostructure (zero-dimensional (0D) Ni nanoparticles and three-dimensional (3D) OMC/SiO₂ framework) is successfully prepared via a self-assembly method, an in situ synthesis, and followed by a calcination treatment. By adjusting the calcination temperature and Ni nanoparticle content, OMC/SiO₂@Ni composites with different graphitization degree, Ni nanoparticle size and magnetic properties can be easily obtained. Remarkably, OMC/SiO₂@Ni0.5-700 composite exhibits an exceedingly strong reflection loss (RL) value of −62.2 dB and a broad effective absorption bandwidth (RL ≤ −10 dB) of 8 GHz (almost covers X and Ku bands) with a layer thickness of only 2.5 mm. Such fabulous MA performance comes from a synergy between the well-designed hierarchical ternary nanostructure and improved impedance matching. This work provides an insight for rational structure design and multi-component loss mechanism of lightweight MA material, which shows great potential in practical applications.