Bifunctional SiC/Si_(3)N_(4) aerogel for highly efficient electromagnetic wave absorption and thermal insulation

SiC ceramics are attractive electromagnetic(EM)absorption materials for the application in harsh environment because of their low density,good dielectric tunable performance,and chemical stability.However,the performance of current SiC-based materials to absorb EM wave is generally unsatisfactory due to poor impedance matching.Herein,we report ultralight SiC/Si3N4 composite aerogels(~15 mg·cm^(−3))consisting of numerous interweaving SiC nanowires and Si3N4 nanoribbons.Aerogels were prepared via siloxane pyrolysis and chemical vapor reaction through the template method.The optimal aerogel exhibits excellent EM wave absorption properties with a strong reflection loss(RL,−48.6 dB)and a wide effective absorption band(EAB,7.4 GHz)at a thickness of 2 mm,attributed to good impedance matching and multi attenuation mechanisms of waves within the unique network structure.In addition,the aerogel exhibits high thermal stability in air until 1000℃and excellent thermal insulation performance(0.030 W·m^(−1)·K^(−1)).These superior performances make the SiC/Si_(3)N_(4) composite aerogel promising to become a new generation of absorption material served under extreme conditions.

A review on the emerging resilient and multifunctional ceramic aerogels

Ceramic aerogels are attractive for their low density,high porosity,large surface area as well as various applications in areas of thermal insulation,catalysis,filtration,and lightweight structural materials.Conventional ceramic aerogels are usually assembled by oxides nanoparticles.Due to the inefficient necklike connections between the nanoparticles and the volume shrinkage at elevated temperatures,ceramic aerogels fail easily caused by the brittleness and high-temperature structural collapse.To overcome these drawbacks,a class of resilient ceramic aerogels with highly porous architectures that are composed of one-or two-dimensional nanostructures has been prepared.Benefiting from the unique microstructures and/or the high-temperature stability of their building blocks,these aerogels exhibit reversible compressibility,high-temperature stability,thermal insulation,and various functions.In this review,we introduced the preparation methods,microstructures,mechanical properties,high-temperature stability,thermal insulation and various functions of these resilient ceramic aerogels.We have also discussed the relationships between their microstructures and properties,including mechanical properties and thermal insulation performance.Finally,perspectives for the further development of resilient ceramic aerogels are presented.