Freeze-Cast Ni-MOF Nanobelts/Chitosan-Derived Magnetic Carbon Aerogels for Broadband Electromagnetic Wave Absorption

Abstract

The exceptional benefits of carbon aerogels, including their low density and tunable electrical characteristics, infuse new life into the realm of creating ultralight electromagnetic wave absorbers. The clever conceptualization and straightforward production of carbon-based aerogels, which marry aligned microporous architecture with nanoscale heterointerfaces and atomic-scale defects, are vital for effective multiscale microwave response. We present an uncomplicated synthesis method for crafting aligned porous Ni@C nanobelts anchored on N, S-doped carbon aerogels (Ni@C/NSCAs), featuring multiscale structural intricaciesachieved through the pyrolysis of freeze-cast Ni-MOF nanobelts and chitosan aerogel composites. The well-ordered porous configuration, combined with multiple heterointerfaces adopting a “nanoparticles-nanobelts-nanosheets” contact schema, along with a wealth of defects, adeptly modulates conductive, polarization, and magnetic losses to realize an equilibrium in impedance matching. This magnetically doped carbon aerogel showcases an impressive effective absorption bandwidth of 8.96 GHz and a minimum reflection loss of −68.82 dB, while maintaining an exceptionally low filler content of 1.75 wt %. Additionally, the applied coating exhibits an astonishing radar cross-section reduction of 51.7 dB m2, signifying its superior radar wave scattering capabilities. These results offer key insights into the attainment of broad-spectrum microwave absorption features by enhancing the multiscale structure of current aerogels.

Microwave Absorption Properties of Hexagonal Ba3(VO4)2 through Zn Doping: A Comprehensive Analysis of Ba3–xZnx(VO4)2

“…32 The optimized conductivity due to the Zn-doping resulted in the formation of a conductive path leading to the joule heating effects in the crystal as shown by the presence of a straight line in the cole-cole plot. 45 The structural arrangement of ions in the crystal lattice affects the material's polarization under an electric field. Different polarization mechanisms (ionic, electronic, orientation, and space-charge polarization) can be affected by the structure and doping, impacting the dielectric losses and enhancing microwave absorption.…”

Intelligent Tunable Wave-Absorbing CNTs/VO2/ANF Composite Aerogels Based on Temperature-Driving

“…However, increasing electromagnetic wave (EMW) pollution and radiation also cause threats to human health and information security. The urgent demand on how to deal with EMW pollution and absorb EMW radiation efficiently has raised great concerns about the development of efficient EMW absorbing materials. − In recent years, many traditional materials such as carbon-based materials (graphene, carbon nanotubes), conductive polymers (ferrites, alloys), and metal-based materials have been applied to electromagnetic wave absorption (EMA) strategies. , Graphene is a two-dimensional structure composed of a single layer of carbon atoms with excellent high electrical conductivity and mechanical strength but is currently expensive to prepare on a large scale and prone to structural changes at high temperatures, affecting performance . Carbon nanotubes have shown great strengths in electromagnetic wave-absorbing materials due to their excellent electrical and thermal conductivity, light weight, and good stability; however, they are easy to agglomerate, are difficult to disperse in the substrate, and have a large dielectric constant, which is not conducive to impedance matching. − The physical properties of aerogels with ultralow density, high porosity, large specific surface area, and low dielectric constant have great potential for modulating EMA. − …”