Micro And Nano Structural Modulation Of Graphene Aerogel Composites And Wave Absorption Applications

In recent years,it’s an urgent need for rational design and eliminate electromagnetic radiation of electromagnetic wave absorbing materials with strong absorption,light weight,thin thickness and wide band width to reduce and eliminate electromagnetic radiation pollution.Graphene aerogel is a new microwave absorber,whose porous structure,large specific surface area,abundant active sites and other characteristics are beneficial to the loss of electromagnetic waves in the internal space of material,thus achieving the attenuation of electromagnetic waves.However,high conductivity,impedance matching imbalance and single loss mechanism hinder the application of graphene aerogel in microwave absorption.In this regard,considering the good magnetic/dielectric synergistic mechanism between magnetic and carbon materials,magnetic materials can be introduced in dielectric materials to optimize the impedance matching and attenuation capability of microwave absorbing materials.In this paper,we combine magnetic materials with graphene aerogel to prepare lightweight and efficient microwave absorbing materials.（1）Hollow-structured ZnO/ZnFe₂O₄ microspheres were firstly prepared by the solvothermal method and high-temperature pyrolysis.Then the composite material（ZnO/ZnFe₂O₄/rGO aerogel）consisting of reduced graphene oxide aerogel and ZnO/ZnFe₂O₄ microspheres was obtained by hydrothermal reaction and further freeze-drying process.The results show that the ZnO/ZnFe₂O₄/rGO aerogel has an abundant porous structure and a large amount of ZnO/ZnFe₂O₄is dispersed on the rGO lamellae with well-preserved structure after hydrothermal reaction.Thanks to the unique porous hollow structure of ZnO/ZnFe₂O₄,the three-dimensional conductive network of rGO aerogel and the good impedance matching,the ZnO/ZnFe₂O₄/rGO aerogel achieves excellent microwave absorption performance with a minimum reflection loss of-65.2d B and an effective absorption bandwidth of 9.1 GHz at 10 wt%filler loading.（2）Nanoparticles obtained from MOF templates were prepared by a simple co-precipitation method and high-temperature annealing process.Subsequently,they were hydrothermally reacted with graphene oxide suspension at 180℃for 6 h and freeze-dried to obtain a novel multidimensional porous composite（NiCo/C/CNT/rGO aerogel）.The results show that the one-dimensional carbon nanotubes are distributed on the NiCo/C surface and NiCo/C/CNT is tightly bound to the reduced graphene oxide nanosheets.Meanwhile,the two-dimensional reduced graphene oxide nanosheets stack on each other to form a three-dimensional porous structure.The NiCo/C/CNT/rGO aerogel composites have excellent microwave absorption performance（-58.8d B）and wide effective absorption bandwidth（7.6 GHz）at a thin thickness（1.8 mm）due to the multidimensional porous structure and the synergistic effect of magnetic-dielectric components.