Preparation Of Zn-Ni-Based MOF-Derived Carbon-Based Composites And Their Microwave Absorption Properties

With the rapid development of science and technology,a large number of electronic devices have appeared.The frequent use of devices has caused electromagnetic waves to be everywhere.Electromagnetic radiation damages human health and also affects the normal operation of electronic devices.Therefore,high-performance electromagnetic absorbing materials have become the focus of research.In practical applications,people expect to obtain ideal absorbing materials with strong absorbing performance,light weight,thin thickness and effective frequency bandwidth.The metal organic framework(MOF)material has a diversified spatial structure,and its metal particle size,occupation,pore size,specific surface area,etc.can be adjusted during the preparation process.With these characteristics,it is used in supercapacitors,catalysis,and sensors.The high temperature treatment of MOF in an inert gas environment can obtain a composite of elemental metal and carbon in situ,while retaining the structural framework of the precursor to a certain extent.The optimization of the space structure of MOF materials and the preparation of derivative-based composite materials can realize the artificial adjustment of the electromagnetic parameters of composite materials,and at the same time make electromagnetic waves reflect multiple times inside the material,which is expected to produce broadband and strong absorption absorbing materials.In this paper,a variety of composite materials have been prepared by simple and inexpensive synthesis methods.The specific research content is as follows:1?Taking Zn-MOF(ZIF8)as the precursor,after high temperature treatment,the low melting point metal zinc is sublimated,the organic ligand is carbonized into porous carbon,and different content of ferrocene is introduced as the iron source to obtained Fe-ZIF8-1,Fe-ZIF8-1.44 and Fe-ZIF8-4.44 with different microscopic morphology and magnetic properties.The absorber in the sample test ring is 20%of the total mass,and when the thickness of Fe-ZIF8-1.44 is 2.48 mm,the best reflection absorption can reach-39.8 d B,and its effective bandwidth(RL?-10 d B)is 5.6 GHz.2?It is found that its microstructure is difficult to control by doping magnetic particles,so a bimetallic MOF with magnetic properties is prepared to improve the loss mechanism to enhance its microwave absorbing performance.Using Zn Ni-MOF as the precursor,sea urchin-like Zn O-Ni O and spherical Ni/C composite materials were obtained through high-temperature treatment,and then Ni/C composite materials were subjected to secondary annealing treatment by introducing a sulfur source to obtain NiS₂/C composite materials.When the absorber content is 30%,the NiS₂/C composite material with a thickness of 2.37mm has the best reflection and absorption value of-47.6 d B,and its effective bandwidth is4.42 GHz.3?In order to optimize the experimental process,Ni-MOF was selected as the precursor to prepare composite materials Ni/C-370,Ni/C-420,Ni/C-470 and Ni/C-520 with different carbonization degrees by adjusting the carbonization temperature.The test results show that when the filling ratio of Ni/C is 30%,the Ni/C-470 composite material with the precursor carbonized at 470?has better electromagnetic wave absorption performance.When the thickness is 2.2 mm,the reflection absorption value can reach-53.09 d B and the effective bandwidth is 5.27 GHz.