Rational Construction of Hierarchically Porous Fe–Co/N-Doped Carbon/rGO Composites for Broadband Microwave Absorption

Developing lightweight and broadband microwave absorbers for dealing with serious electromagnetic radiation pollution is a great challenge.Here,a novel Fe-Co/N-doped carbon/reduced graphene oxide(Fe-Co/NC/rGO)composite with hierarchically porous structure was designed and synthetized by in situ growth of Fe-doped Cobased metal organic frameworks(Co-MOF)on the sheets of porous cocoon-like rGO followed by calcination.The Fe-Co/NC composites are homogeneously distributed on the sheets of porous rGO.The Fe-Co/NC/rGO composite with multiple components(Fe/Co/NC/rGO)causes magnetic loss,dielectric loss,resistance loss,interfacial polarization,and good impedance matching.The hierarchically porous structure of the Fe-Co/NC/rGO enhances the multiple reflections and scattering of microwaves.Compared with the Co/NC and Fe-Co/NC,the hierarchically porous Fe-Co/NC/rGO composite exhibits much better microwave absorption performances due to the rational composition and porous structural design.Its minimum reflection loss(RLmin)reaches?43.26 dB at 11.28 GHz with a thickness of 2.5 mm,and the effective absorption frequency(RL≤?10 dB)is up to 9.12 GHz(8.88-18 GHz)with the same thickness of 2.5 mm.Moreover,the widest effective bandwidth of 9.29 GHz occurs at a thickness of 2.63 mm.This work provides a lightweight and broadband microwave absorbing material while offering a new idea to design excellent microwave absorbers with multicomponent and hierarchically porous structures.

高击穿电压聚氨酯漆包线的制备及性能

采用1,1,2,2-四氢全氟-1-癸醇对异佛尔酮二异氰酸酯三聚体的1个异氰酸酯基进行封端,将封端后的三聚体替代部分异佛尔酮二异氰酸酯与全氟聚醚二元醇反应,合成了不同三聚体含量的支链型含氟聚氨酯。然后将支链型含氟聚氨酯配置成漆包线漆,通过高速漆包线机将其制备成漆包线。分别采用红外光谱、热重分析仪、万能试验机和接触角测试仪等对所制备的支链型含氟聚氨酯结构、热稳定性、力学性能以及疏水性进行测试;采用电压试验仪、单向刮漆试验仪、软化击穿试验仪及焊锡试验仪等对漆包线的击穿电压、力学性能、热性能和直焊性进行测试,探究了封端三聚体含量对聚合物结构、性能以及漆包线性能的影响。结果表明,封端三聚体占比30%(摩尔分数)的支链型含氟聚氨酯的拉伸强度可达30.50 MPa、断裂伸长率为952%、初始分解温度提高至216.6℃、接触角增大至96.1°,相较于普通的聚氨酯均有大幅提高;相应漆包线的击穿电压高达7033.8 V,而封端三聚体占比10%的支链型含氟聚氨酯漆包线的击穿电压最高,达到了7513.4 V,是普通聚氨酯漆包线(4719.8 V)的1.6倍。同时,力学性能、热性能和直焊性均满足聚氨酯漆包线的使用要求。