Synthesis And Microwave Absorption Properties Of MOF Derived Zn-Co/C Doped Graphene

Metal-organic frameworks(MOFs)are kinds of coordination polymer assembled by metal coordinating clusters and aromatic organic linkers.Due to its two-dimensional,three-dimensional structure and special metal/carbon composite,it has been considered to be one of the potential microwave absorption material.however,its disadvantages such as easy agglomeration and poor impedance matching performance affect its microwave absorption effect in practical applications.As a single-layer material with good dielectric properties,graphene exhibits excellent performances in terms of providing a larger interface and increasing the rate of carrier migration.Assembling MOF and two-dimensional graphene is a feasible method to obtain materials with excellent microwave absorption capacity and impedance matching performance.In this paper,Zn-Co/C nanoparticles derived from Zn-Co metal-organic frameworks were prepared and compounded with reduced oxide graphene.In this paper,by changing the preparation conditions and the concentration of graphene composite,the electromagnetic parameters and impedance matching of the composite material are adjusted to improve the microwave absorption capacity of the material.The main contents of this article are as follows:(1)MOFs' structure consists of Zn-Co and isophthalic acid as ligands were prepared by hydrothermal method,the precursor with a stable,three-dimensional hollow structure can provide more reflection and achieve good effects in the field of material composite and microwave absorption.Different reaction dosage ratios of 1:0:1,0:1:1,1:1:1,1:1:2,1:1:3,and 1:1:4 for metal ligands and organic ligands were prepared to analyze the effect of dosage ratios on morphology.The experimental results show that when the molar mass ratio of the metal ligand to the organic ligand is 1:1:2,an ideal precursor material with uniform microscopic morphology could be formed,it has a hollow spherical shell structure,and the surface of the spherical shell is covered with wrinkles.(2)Analyze the microwave loss performance of the composite material by changing the annealing temperature to 500?,600?,700?,and 800?.The results showed that when the annealing temperature is 600? for 10 minutes,materials with better microwave loss performance could be obtained.This is because the increasing of the annealing temperature makes the degree of metal crystallinity get higher and the amorphous carbon content formed by the organic framework is gradually increasing.But if the temperature is too high,the structure of the Zn-Co/C nanospheres will collapse and the metal particles will be separated from the organic framework.When the annealing temperature is 600°C,the lowest reflection loss in the range of 2-18 GHz is-11.05 dB,and the corresponding thickness is 5.0 mm.When the annealing temperature is 800°C,the lowest reflection loss is-26.88 dB.(3)The impedance matching of the material was adjusted by graphene,and the ZnCo/C composite material is prepared with a reaction mass ratio of 1:1.2 and an annealing temperature of 600°C.Graphene solutions with concentrations of 0.6 mg/ml,0.9 mg/ml,1.2 mg/ml and 1.5 mg/ml were introduced to obtain ZnCo/C/RGO composite materials.As the concentration of graphene increased,the impedance matching of the material gradually increased.When the concentration of the graphene solution is 1.2mg/ml,the minimum reflection loss of Zn-Co/C/RGO with a thickness of 1.5 mm reached-32.56 dB with the bandwidth corresponding to RL at-10 dB can reach 3.92 GHz,while,a minimum RL of-47.15 dB at 11.2 GHz was also obtained at the thickness of 2.0 mm.