Rational design of the microstructure of functional materials provides a new opportunity to improve their performance. However, it is always difficult to construct desirable microstructures in magnetic metals due to their strong magnetic interactions. Herein, we demonstrate the successful synthesis of three-dimensional flower-like Ni microspheres (FNMs) through a simple two-step process, in which flower-like Ni(OH)₂ microspheres are firstly prepared by a hydrothermal route and then are reduced under a high-temperature H₂/N₂ atmosphere. The as-prepared FNMs are composed of cross-linked nanoparticles directed by their precursor. Compared with commercial and home-made Ni powder, FNMs exhibit enhanced conductivity and dielectric loss ability, as well as significantly improved impedance matching. As a result, FNMs exhibit good microwave absorption properties, including a strong reflection loss (−56.8 dB at 15.8 GHz) and a broad qualified frequency range (2.5–18.0 GHz) with thicknesses ranging from 5.0 to 1.0 mm and a thin matching thickness of 1.12 mm. Such an excellent performance is substantially superior to those of Ni-based materials derived from various elaborate strategies. It is believed that our work may inspire the controlled synthesis of conventional magnetic metal materials with enhanced microwave absorption properties in the future.

Graphene nanowalls (GNWs) with different sizes (i.e., length and height) were grown directly on the surface of individual carbon fibers (CFs) using a radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) technique. The size was controlled by varying the deposition time. The GNW-modified CFs were embedded into epoxy resin matrix to prepare a series of carbon-fiber-reinforced composites (CFRCs). The results indicated that GNWs were remarkably effective in improving the interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of the carbon-fiber-reinforced composites. The enhancement effect on the strength strongly depended on the size of GNWs. It increased with the increase in the GNWs’ size and reached the maximum upon the incorporation of GNWs that were grown for 45 min. Noticeable increases of 222.8% and 41.1% were observed in IFSS and ILSS, respectively. The enhancement mechanism was revealed by means of scanning electron microscope (SEM) fractography analysis. However, further increase of GNW size led to no more improvement in the shear strength. It could result from the increased defect concentration and wrinkle size in the GNWs, which deteriorated the strength.

The rational design of magnetic carbon composites, encompassing both their composition and microstructure, holds significant potential for achieving exceptional electromagnetic wave-absorbing materials (EAMs). In this study, FeCo@CM composites were efficiently fabricated through an advanced microwave plasma-assisted reduction chemical vapor deposition (MPARCVD) technique, offering high efficiency, low cost, and energy-saving benefits. By depositing graphitized carbon microspheres, the dielectric properties were significantly enhanced, resulting in improved electromagnetic wave absorption performances through optimized impedance matching and a synergistic effect with magnetic loss. A systematic investigation revealed that the laminar-stacked structure of FeCo exhibited superior properties compared to its spherical counterpart, supplying a higher number of exposed edges and enhanced catalytic activity, which facilitated the deposition of uniform and low-defect graphitized carbon microspheres. Consequently, the dielectric loss performance of the FeCo@CM composites was dramatically improved due to increased electrical conductivity and the formation of abundant heterogeneous interfaces. At a 40 wt% filling amount and a frequency of 7.84 GHz, the FeCo@CM composites achieved a minimum reflection loss value of −58.2 dB with an effective absorption bandwidth (f_E) of 5.13 GHz. This study presents an effective strategy for developing high-performance EAMs.