To achieve excellent electromagnetic wave (EMW) absorption properties, the microstructure design of the absorber is critical. In this work, six kinds of N-Ni/C nanostructures with different morphologies were prepared by one-step hydrothermal method and high temperature carbonization by adjusting the types of nickel salts and reaction solvents. The EMW absorption performance of six different morphologies of N-Ni/C nanostructures was compared and analyzed. Among them, it is found that the nanoflower-like N-Ni/C composite has excellent dielectric loss and magnetic loss synergistic effect due to its polycrystalline structure, and can obtain excellent EMW absorption performance. The minimum reflection loss value at a thickness of 1.9 mm is −59.56 dB at 16.88 GHz, and the effective absorption bandwidth value reaches 6.0 GHz at a thickness of 2.2 mm. Our research shows that different morphologies and multiple lattice structures of nanostructures with the same composition have a significant influence on EMW absorption performance, which provides new research ideas for developing high-performance EMW absorbing materials.

Two-dimensional metal carbide or nitride materials (MXenes) are widely used in electromagnetic wave absorption because of their unique structure. Herein, a novel composite preparation strategy has been proposed to design dendritic nanofibers based on the electrostatic spinning methods. The multifunctional MXene nanosheets are used as the dendritic matrix, and magnetic nanoparticles are embedded in the nanosheets as magnetic loss units. Multidimensional nanocomposites have interlaced carbon fiber networks, large-scale magnetically coupled networks, and a lot of multi-heterojunction interface structures, which endow the composites with extraordinary conduction loss, magnetic loss, and polarization loss capabilities, respectively. The impedance matching and loss mechanisms of the composites are improved by optimizing the synergistic relationship between the components and building a suitable structure. The optimum reflection loss (RL) of −54.1 dB is achieved at 2.7 mm and a wide effective absorption bandwidth (EAB, RL below −10 dB) of 7.76 GHz is obtained at a small thickness of 2.1 mm for the nanocomposites. The distinctive microstructures of the nanofibrous membranes give rise to their flexibility, waterproof, and electromagnetic wave absorption performance and endow the nanofibrous membranes potential to be utilized as lightweight, efficient electromagnetic wave protective fabric in harsh environment.