Preparation And Microwave Absorption Properties Of Zinc Ferrite @ZIF-8 Derived Carbon Composites

The wide application of electromagnetic wave has promoted the development of electronic communication technology,and the civil and military fields have been improved qualitatively,but the electromagnetic pollution problem has become increasingly prominent.Electromagnetic wave generated during the operation of electronic devices will not only interfere with communication signals,but also pollute the natural environment,and even affect people’s health.Therefore,it is necessary to find a way to reduce electromagnetic pollution,and wave-absorbing materials are increasingly concerned by researchers because of their effective consumption of electromagnetic wave.The design of effective absorption bandwidth,low density,thin coating thickness and good absorption performance of wave-absorbing material has gradually become a hot research issue.As a kind of magnetic loss material,ferrite has low cost,high magnetic loss and stable chemical properties,so it is widely used in the development and design of absorbing materials.As a porous structural material,MOFs have the advantages of low density and high specific surface area,which can greatly improve the absorbing properties of materials,so they become a hot research direction of absorbing materials.This paper used the sol-gel combustion method,in-situ growth method and high temperature heat treatment,with Zn（NO₃）₂·6H₂O,Fe（NO₃）₃·9H₂O,Co（NO₃）₂·6H₂O,dimethylimidazole（2-MIM）as raw materials.A series of Zn_（1-x）Co_xFe₂O₄@ZIF-8 derivatives Zn_（1-x）Co_xFe₂O₄@C were prepared,and the absorption properties of the absorbing materials were improved by exploring the process temperature,regulating the composite ZIF-8 component,doping Co element.Specific work contents are as follows:（1）The modulation of the microstructure and dielectric loss characteristics of ZnFe₂O₄was achieved by the heat treatment temperature change,thus regulating the electromagnetic parameters of the material,and the ZnFe₂O₄@derived carbon material with excellent wave absorbing properties was obtained.When the carbonization temperature is 800°C,the material has excellent dielectric loss characteristics,and achieves RL≤-10 d B in the full frequency band of 2-18 GHz when the coating thickness d is 1-5 mm,and achieves RL≤-10 d B in the C-and X-band when the coating thickness d is only 1-2 mm.（2）The ZnFe₂O₄@C composite with"honeycomb"structure was prepared.The results show that the absorbing performance of the ZnFe₂O₄@C composites is optimized when the content of the clad ZIF-8 is 5%and 10%.The results show that the minimum reflection loss value of-36.5 d B is achieved at 9.4 GHz when the content of ZIF-8 is 5%,at which the coating thickness is 2.0 mm and the effective absorption bandwidth（RL≤-10 d B）is 3.5 GHz（7.6～11.1 GHz）.When the content of ZIF-8 is 10%,the minimum reflection loss value of-37.8 d B is achieved at 10.0 GHz with a coating thickness of 2.0 mm,and the effective absorption bandwidth is 3.5 GHz（7.9～11.3 GHz）.（3）Zn_（1-x）Co_xFe₂O₄ was prepared by doping Co²⁺during the preparation of ZnFe₂O₄ based on the sol-gel combustion method.By adjusting the content of Co,the performance of microwave absorption performance of the sample with the content of Co was studied.By doping the sample with Co elements and adjusting the magnetic permeability,the impedance matching is substantially optimized,and the sample has the largest area of∣（35）∣≤0.4 with the best impedance mismatch when x=0.1,and the best absorption performance with a RL value of-46.3 d B at a sample thickness of 2.2 mm,and the effective absorption bandwidth is 5.0 GHz（10.1～15.1 GHz）.The absorption performance is the best.Compared with the samples doped with Co,the performance has been greatly improved.