Ultralight and High-Strength SiC_nw@SiC Foam with Highly Efficient Microwave Absorption and Heat Insulation Properties

Abstract

An ultralight and high-strength SiCnw@SiC foam with highly efficient microwave absorption and heat insulation properties was successfully synthesized using the template sacrifice method and chemical vapor deposition process. The microstructure is a novel double network structure, which is formed by the coupling of the morphology-controlled SiCnw and the SiC skeleton. The introduction of SiCnw can not only provide more interface polarization and dielectric loss to the SiC foam, which greatly enhances the microwave absorption capacity of the composite foam, but also can enable it to act as an excellent radiation absorbent, which can effectively reduce the thermal conductivity of the foam, especially at high temperatures. In this study, a minimum reflection loss (RL min) of −52.49 dB was achieved at 2.82 mm thickness with an effective absorption bandwidth of 5.6 GHz. As the length/diameter ratio of SiCnw decreases, the composite foam exhibits excellent high-temperature thermal insulation and mechanical properties. For the SiCnw@SiC foam, the thermal conductivity is only 0.304 W/mK at 1200 °C and the compressive strength reaches 1.53 MPa. This multifunctional SiCnw@SiC foam is an outstanding material, which has potential applications in microwave absorption and high-temperature heat insulation in harsh environments.

Effects of SiC whisker addition on mechanical, thermal, and permeability properties of porous silica‐bonded SiC ceramics

“…The maximum thermal conductivity (1.415 Wm −1 K −1 ) was obtained in the SW100-12 sample, and the lowest thermal conductivity (0.060 Wm −1 K −1 ) was obtained in the SW0-8 sample. These results are the opposite of the previous results reported in porous silica-bonded SiC ceramics, [33][34][35] C/SiO 2 /SiC-based aerogels, 65 SiC nanowire-SiC foams, 66 and mullite-SiC foams. 67 The exceptional phenomenon can be understood by the following:…”

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

“…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.…”

“…[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.…”

Dielectric Loss Mechanism in Electromagnetic Wave Absorbing Materials

“…Up to now, the foam‐structured absorbing materials including carbonaceous foam and SiC foam have been widely investigated and shown fascinating properties such as fireproofing and thermal insulation (Figure 2i ). [ 92 , 93 ]…”