Lightweight, Fire‐Retardant, and Anti‐Compressed Honeycombed‐Like Carbon Aerogels for Thermal Management and High‐Efficiency Electromagnetic Absorbing Properties

Abstract

Ordered porous carbon materials (PCMs) have potential applications in various fields due to their low mass densities and porous features. However, it yet remains extremely challenging to construct PCMs with multifunctionalization for electromagnetic wave absorption. Herein, the honeycombed‐like carbon aerogels with embedded Co@C nanoparticles are fabricated by a directionally freeze‐casting and carbonization method. The optimized aerogel possesses low density (0.017 g cm−3), fire‐retardant, robust mechanical performance (compression moduli reach 1411 and 420 kPa in the longitudinal and transverse directions at 80% strain, respectively), and high thermal management (high thermal insulation capability and high‐efficiency electrothermal conversion ability). Notably, the optimized aerogel exhibits the excellent electromagnetic wave absorption properties with broad effective absorption bandwidth (13.12–17.14 GHz) and strong absorption (−45.02 dB) at a thickness of only 1.5 mm. Density functional theory calculations and the experimental results demonstrate that the excellent electromagnetic wave absorption properties stem from the synergetic effects among high electrical conductivity, numerous interfaces and dipoles and unique ordered porous structure. Meanwhile, the computer simulation technology (CST) simulation confirms that the multifunctional aerogel can attenuate more electromagnetic energy in a practical environment. This work paves the way for rational design and fabrication of the next‐generation electromagnetic wave absorbing materials.

Dimensional Design and Core–Shell Engineering of Nanomaterials for Electromagnetic Wave Absorption

“…[240] The ultralow density, excellent compressibility and elasticity, and unique cellular structure of aerogels are anticipated to satisfy the demands for multiple functions, such as those for sensors, water treatment, flame resistance, and thermal insulation, as shown in Figure 17. [28,29,[240][241][242] The aerogels of Co-rGO/chitosan have low density, robust mechanical properties, excellent thermal management, and high flame retardancy (Figure 17c-h). [240] [29] Copyright 2018, American Chemical Society.…”

“…In the past decades, the assembly of low-dimensional coreshell units into an aerogel has attracted considerable inte rest. [28,29,[239][240][241][242] The presence of numerous pore structures benefits impedance matching according to the effective medium and provides multireflection/multiscattering sites for EM wave attenuation. The large heterointerfaces in pores intensify the interfacial effects, and the interconnected structure units form conduction networks, eventually contributing to the dielectric loss capacity.…”

“…[28,29,[240][241][242] The aerogels of Co-rGO/chitosan have low density, robust mechanical properties, excellent thermal management, and high flame retardancy (Figure 17c-h). [240] [29] Copyright 2018, American Chemical Society. c,d) Mechanical properties: The digital photograph shows the lightweight natural (c) and anticompressed (d) property of metal nanoparticles-rGO-chitosan (M-C-CG) aerogel.…”

“…e-h) Thermal management properties: e,f) Time-dependent temperature plots of rGO-chitosan (e) and Co-C-CG (f) aerogels and f,g) digital photos of rGO-chitosan (g) and Co-C-CG (h) in a hot flame. c-h) Reproduced with permission [240]. Copyright 2021, Wiley-VCH.…”

A Flexible, Mechanically Strong, and Anti‐Corrosion Electromagnetic Wave Absorption Composite Film with Periodic Electroconductive Patterns

“…According to the effective medium and free electron theories (ε″ ≈ 1/2πε 0 ρf), the ε′ and ε″ values were determined by electron transmission and electrical conductivity. [19,[51][52][53][54] With the dissolution of copper, the complex permittivity of these composite films dropped in a cliff-like manner, and the real and imaginary parts of the ACP film finally stabilized at 23 ± 2 and 6 ± 1, respectively. For the EMW absorbing materials, high EM parameters not only brought strong attenuation, but also resulted in high reflectivity or poor impedance matching.…”