Flower-like CuS hollow microspheres composed of nanoflakes have been successfully prepared via a facile solvothermal method. The crystal structure, morphology and microwave absorption properties of the as-synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and a network analyser. The effects of reaction temperature, concentration of the reagents and reaction time on the structures and morphologies of the CuS products were investigated using XRD and SEM techniques. A plausible mechanism for the formation of hollow architectures related to Ostwald ripening was proposed. The CuS/paraffin composite containing 30 wt% CuS hollow microspheres shows the best microwave absorption properties compared with other CuS/paraffin composites. The minimum reflection loss of −31.5 dB can be observed at 16.7 GHz and reflection loss below −10 dB is 3.6 GHz (14.4–18.0 GHz) with a thickness of only 1.8 mm. The effective absorption (below −10 dB, 90% microwave absorption) bandwidth can be tuned between 6.2 GHz and 18.0 GHz for the absorber with a thin thickness in the range 1.5–4.0 mm. The results indicate that the microwave absorption properties of flower-like CuS hollow microspheres possess the advantages of broad bandwidth, strong absorption, lightweight and thin thickness are superior to those of other absorbing materials.

Traditional ceramic materials are generally brittle and not flexible with high production costs, which seriously hinders their practical applications. Multifunctional nanofiber ceramic aerogels are highly desirable for applications in extreme environments, however, the integration of multiple functions in their preparation is extremely challenging. To tackle these challenges, we fabricated a multifunctional SiC@SiO₂ nanofiber aerogel (SiC@SiO₂ NFA) with a three-dimensional (3D) porous cross-linked structure through a simple chemical vapor deposition method and subsequent heat-treatment process. The as-prepared SiC@SiO₂ NFA exhibits an ultralow density (~ 11 mg cm^− 3), ultra-elastic, fatigue-resistant and refractory performance, high temperature thermal stability, thermal insulation properties, and significant strain-dependent piezoresistive sensing behavior. Furthermore, the SiC@SiO₂ NFA shows a superior electromagnetic wave absorption performance with a minimum refection loss (RL_min) value of − 50.36 dB and a maximum effective absorption bandwidth (EAB_max) of 8.6 GHz. The successful preparation of this multifunctional aerogel material provides a promising prospect for the design and fabrication of the cutting-edge ceramic materials.

In recent decades, problems with electromagnetic interference (EMI) radiation problems have arisen, that can seriously reduce the performance of precision devices nearby and threaten human health. In consequence, it is important to seek high efficiency materials to suppress EMI pollution. Generally, high magnetic permeability or electrical conductivity is essential for efficient EMI shielding. Conventionally, various forms of metal construction (sheet/films, coatings, etc.) are used for EMI shielding. However, metallic shielding has drawbacks that include high density, lack of corrosion resistance and expensive processing, which restrict its use in the modern electronic world. By contrast, conductive polymer composites (CPCs), formed from insulative polymers and conductive fillers, have attracted more and more interest from both industry and academia. CPCs have properties that offer great potential for application in efficient EMI shielding. These include low density, high flexibility, good chemical stability and easy processing and forming. From a theoretical viewpoint, it is generally accepted that the shielding of EM waves is due to the three basic mechanisms of reflection, absorption and multiple internal reflections. However, it must be recognized that the SE of CPCs has a close relation to the reflection mechanism, which can cause secondary EMI pollution. Therefore, materials with charge carriers or magnetic/electric dipoles as well as cellular structure should be the focus for the development of EMI shielding materials with strong absorption properties. On that basis, the main aim of this paper is to review the current position in research of the design of inorganic based foams (metal, carbon or MXene) and polymer composite foams as EMI shielding materials. On the one hand, these composite foams have the merit of being lightweight, and on the other hand, the special porous structure can effectively harvest microwaves by prolonging the travel path. As a result, absorption dominates EMI shielding, which satisfies current requirements of EMI shielding applications. This review also points out the future challenges and gives guidelines for finding solutions for the next generation of shielding applications using composite foams.

The core–shell Ni–SiO₂ composite exhibits the best electromagnetic wave absorption in the GHz range with a minimum reflection loss of −40.0 dB, which is superior to those of Ni–TiO₂ and Ni microspheres.