Compositional and Hollow Engineering of Silicon Carbide/Carbon Microspheres as High-Performance Microwave Absorbing Materials with Good Environmental Tolerance

Microwave absorbing materials(MAMs)characterized by high absorption efficiency and good environmental tolerance are highly desirable in practical applications.Both silicon carbide and carbon are considered as stable MAMs under some rigorous conditions,while their composites still fail to produce satisfactory microwave absorption performance regardless of the improvements as compared with the individuals.Herein,we have successfully implemented compositional and structural engineering to fabricate hollow Si C/C microspheres with controllable composition.The simultaneous modulation on dielectric properties and impedance matching can be easily achieved as the change in the composition of these composites.The formation of hollow structure not only favors lightweight feature,but also generates considerable contribution to microwave attenuation capacity.With the synergistic effect of composition and structure,the optimized SiC/C composite exhibits excellent performance,whose the strongest reflection loss intensity and broadest effective absorption reach-60.8 dB and 5.1 GHz,respectively,and its microwave absorption properties are actually superior to those of most SiC/C composites in previous studies.In addition,the stability tests of microwave absorption capacity after exposure to harsh conditions and Radar Cross Section simulation data demonstrate that hollow SiC/C microspheres from compositional and structural optimization have a bright prospect in practical applications.

Advances in core–shell engineering of carbon-based composites for electromagnetic wave absorption

Electromagnetic(EM)absorption is paving the way to overcome the challenges related to conventional shielding strategy against EM pollution through sustainable energy dissipation.As characteristic functional media that can interact with electric or magnetic field branch,EM wave absorption materials(EWAMs)have received extensive attention and realized considerable development in the past two decades,where carbon-based composites are always considered as promising candidates for high-performance EMAWs due to their synergetic loss mechanism as well as diversified composition and microstructure design.Recent progress indicates that there is more and more interest in the fabrication of carbon-based composites with unique core–shell configuration.On one hand,core–shell configuration usually ensures good chemical homogeneity of final products and provides some positive protections for the components with susceptibility to corrosion,on the other hand,it creates enough heterogeneous interfaces between different EM components,which may bring enhanced polarization effect and intensify the consumption of EM energy.In this review,we firstly introduce EM wave absorption theory,and then highlight the advances of core–shell engineering in carbonbased composites in terms of built-in carbon cores and built-out carbon shells.Moreover,we also show some special core–shell carbon-based composites,including carbon/carbon composites,assembled composites,and decorated composites.After analyzing EM absorption performance of some representative composites,we further propose some challenges and perspectives on the development of core–shell carbon-based composites.