Design,Preparation And Property Research Of Composite Nanoporous Carbon Wave Absorbing Materials

Porous carbon has the advantages of low density and high electrical conductivity,which makes it potential for synthesizing lightweight wave absorbing materials.However,porous carbon usually has electromagnetic mismatch problems and weak of loss mechanism,making it difficult to get effective consumption of electromagnetic waves.The electromagnetic properties of the material can be improved by compounding porous carbon with magnetic metallic materials,which facilitate impedance matching and electromagnetic loss.Metal-organic frameworks(MOFs)are a series of crystalline materials consisting of magnetic metallic ions and organic ligands,which have the advantages of large specific surface area and adjustable morphology.The metal/nano-porous carbon complex can be formed by carbonizing it as a precursor,thus realizing the composition of magnetic metal and carbon.The metal/nano-porous carbon complex can be formed by carbonizing it as a precursor,which provides a feasible route to realize the composite of magnetic metal and carbon.By designing the composition and morphology of the precursors,some special structures can also be introduced to facilitate carrier migration and polarization relaxation to expand the frequency range of electromagnetic wave absorption.This thesis is intended for the study of the porous carbon derived from metalorganic derivatives.Through the structural design of the precursor,the electromagnetic parameters of the composite porous carbon are optimized to enhance the electromagnetic wave absorption performance and finally achieve the goal of "thin,light,wide and strong".The main research contents and experimental results are as follows:1.Synthesis of six-pointed star Ni-Zn-MOF and modulation of the wave absorption properties of the derived porous carbon materials.The Zn with low boiling point was utilized to prepare Ni/NiZn@C composite porous carbon with different compositions by controlling the carbonization temperature.It is shown that with the increase of the temperature,the Ni3ZnC0.7 obtained in the material is partially converted into Ni,which can improve the overall magnetic loss performance of the composite and indirectly affect the microscopic morphology of the material.When the charring temperature is 800℃,Ni/NiZn@C has the best wave absorption performance,which has an effective bandwidth of 5.9 GHz and the minimum reflection loss of-56.8 dB.2.To further construct a carbon skeleton structure with three-dimensional porous cavities,MF@NiZn composites were obtained by growing metal-organic frameworks on the melamine foam(MF)as the template.It is shown that the material has a nanoflower structure,and nano-capsules,which are formed by magnetic metals and carbon shells,are dotted on the surface of the nano-flower petals.This structure can increase the number of reflections of electromagnetic waves on the surface,thus extending the electromagnetic wave transmission path,improving impedance matching and reducing reflectivity.At the same time,the structure itself is stable and less prone to collapse,achieving the purpose of reducing reflectivity.The samples prepared at annealing temperatures of 800℃ and 900℃ can obtain the effective bandwidths of 6.0 GHz and 5.9 GHz,and the reflection loss can reach-46.5 dB and-40.5 dB,respectively.