A novel flexible and recoverable SiC nanofiber aerogel (SiC nf aerogel) was synthesized by electrospinning and freeze-drying methods. The SiC fibers prepared by electrospinning technique, have a fine diameter (~600 nm) and excellent flexibility. On this basis, the fibers are stirred at a high-speed and then subjected to freeze-drying and high-temperature treatment to prepare a SiC nf aerogels. The fabricated SiC nf aerogels possess low density (0.039–0.041 g/cm 3 ), excellent thermal insulation (0.025–0.031 W/(m∙K)), and mechanical properties of recoverable strain (~40%). Meanwhile, the SiC nf aerogels show excellent electromagnetic (EM) wave absorption characteristics, which have the effective absorption bandwidth of 9–11.5 GHz (reflection loss (RL) < −10 dB, more than 90% EM wave was absorbed) and minimum RL value attained −21.41 dB at 10.5 GHz with the thickness of 3 mm. The successful preparation of the novel multifunctional material can be used for high temperature insulation materials and electromagnetic wave absorbing materials in harsh environments.
Ceramic aerogels are promising high-temperature thermal insulation materials due to their outstanding thermal stability and oxidation resistance. However, restricted by nanoparticle-assembled network structures, conventional ceramic aerogels commonly suffer from inherent brittleness, volume shrinkage, and structural collapse at high temperatures. Here, to overcome such obstacles, 3D ultralight and highly porous carbon tube foams (CTFs) were designed and synthesized as the carbonaceous precursors, where melamine foams were used as the sacrificial templates to form the hollow and thin-wall network structures in the CTFs (density: ∼4.8 mg cm–3). Then, the arbitrary-shaped silicon carbide (SiC) nanofibrous aerogels (SNFAs) were obtained through a simple chemical vapor deposition (CVD) process on the CTFs. The resulting SNFAs exhibited excellent comprehensive performances: ultralow density (4.2 mg cm–3) and thermal conductivity (21.3 mW m–1 K–1 at room temperature), excellent rigidity (specific modulus: 13.2 kN·m kg–1), and resilient compressibility. The SNFAs could support over 2100 times their weight without visible deformation. Furthermore, the SNFAs also showed exceptional high-temperature thermal stability, which means that they could withstand 1100 °C in an air atmosphere and 1550 °C in an inert atmosphere. These superior comprehensive performances enable SNFAs to be suitable for thermal insulation in harsh environments.
Multifunctional high-level performance electromagnetic wave (EMW) absorbing materials is receiving increasing attention with the rapid development of modern information technology. However, current EMW absorbing materials usually have single function and poor thermal and chemical stability, which seriously hinders the practical application of these materials. Herein, to broaden the application fields of the EMW absorption materials, a multifunctional SiC nanofiber aerogel (SiC NFA) was prepared by using chemical vapor deposition (CVD) technology in this work. The as-synthesized SiC NFA exhibits a quite low density (∼9 mg cm −3 ), excellent mechanical performance, high fatigue-resistant, satisfactory refractory property, high temperature thermal stability and good thermal insulation performance. Moreover, the oil-modified SiC NFA has a dramatic hydrophobicity , resulting in a good self-cleaning performance. This SiC NFA also achieves a superior EMW-absorbing property with a minimum refection loss (RL min ) value of −39.37 dB at 7.04 GHz when its thickness is 1.9 mm. These inspiring findings lay a foundation for the subsequent development of multifunctional EMW absorbents.
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