Microwave Absorption Properties Of MOF-Derived Carbon Nanotube Composites

Electromagnetic wave absorption(EMWA)materials play an important role in improving electromagnetic radiation pollution and promoting energy absorption,and designing high-performance EMWA materials has become an indispensable requirement.Metal organic frameworks(MOFs)have been widely used to prepare porous carbon-based composites with the advantages of high porosity,tunable composition,and diverse morphological structures.Its derived carbon nanotubes(CNTs)composites with rich heterogeneous interfaces,a large number of continuous conductive networks and multicomponent coordination,as well as multiple scattering paths formed by the porous structure inherited from MOF,all contribute to the enhanced attenuation of electromagnetic waves and improved EMWA performance.Therefore,it is important to study the EMWA performance of MOF-derived CNTs composites.In response to the need for broadband absorbing properties of EMWA materials,this thesis achieves the selective region-controlled growth of CNTs by controlling the collapse state of MOF precursors.This unique distribution can form a local conductive network to prevent the generation of global conductive pathways and enable the impedance matching of their composites over a wide loading concentration range.As a result,the carbonyl iron(CI)/CNTs composite exhibits a broadband effective absorption of more than5.0 GHz over a wide filling range of 50 wt%-55 wt%.Moreover,the material can achieve full-frequency absorption from 2-18 GHz at a total thickness of 8.7mm after optimization by superstructure design.This work provides a new approach for the preparation of broadband EMWA materials.In this thesis,multi-stage structured carbon fiber(CF)/CNTs composites were prepared for the need of integrated structure-function design of EMWA materials.The number of functional groups on the surface of CF was controlled by changing the pretreatment of CF,and the number of CNTs grown on the surface was adjusted to effectively regulate the electromagnetic properties of the composites.This work provides a new idea for the design of structural absorbing materials.