Preparation And Properties Of Fe/Carbon/Ceramic Composite Microwave Absorbing Materials

With the development of radio communication equipments and electronic technology,electromagnetic wave,as an information medium,has penetrated into all aspects of human life,bringing convenience but also causing serious electromagnetic radiation.In the military field,with the rapid development of detection technology,the application of stealth technology has been more and more extensive.Therefore,the research of microwave absorbing materials is a hot topic at present.On the other hand,a large amount of coal gangue is generated in the process of coal mining and coal washing,which is extremely polluting the environment by stacking treatment.Therefore,it is the main task of researchers to reuse coal gangue.In this paper,the coal gangue was uesd to prepare ceramic-based composite microwave absorbing materials.This can not only open up a new way for the recycling of coal gangue,but also to achieve low-cost preparation of microwave absorbing materials.The specific works are as follows:The ceramic matrix was prepared from coal gangue and starch by pelletizing and solid sintering.It was impregnated into 1.5 mol/L iron nitrate precursor solution,and then calcined in inert atmosphere to obtain a series of ceramic-based composites loaded with different magnetic components.The effects of calcination temperature on the phase,structure and microwave absorption properties of the composites were studied.The results showed that,there were certain magnetic properties and graphitization degree of the prepared ceramic-based composite absorbing materials,which were attributed to the carbothermal reduction reaction during the calcination process.It was found,the position of the reflection peak could be adjusted by changing the coating thickness and phase composition.When the calcination temperature was 700 ?,a minimum reflection loss of-18.4 dB and an effective absorption bandwidth of4.2 GHz of FeG700 were observed when the coating thickness was 1.5 mm.Its excellent absorbing performance could be attributed to the synergistic effect of dielectric loss and magnetic loss,and the dielectric loss came from interfacepolarization,the magnetic loss came from natural resonance and exchange resonance.Ceramic-based composites with different magnetic component loading were prepared by adjusting the concentration of iron nitrate precursor solution and sintering at a specific temperature in an inert atmosphere.The effects of magnetic component loading on the phase,structure and microwave absorption properties of composites were investigated.The results showed that,changing the concentration of precursor solution could adjust the loading of magnetic component,then affected the electromagnetic parameters and optimized the microwave absorption performance.The higher the concentration of the solution,the more the magnetic component loading and the stronger the magnetic properties of the composites.However,the microwave absorption properties and electromagnetic parameter values of composites were not in the same growth trend as the magnetic component loading.It was found that the effective absorption bandwidth of the FeG700 was the widest(5 GHz)with a coating thickness of 2 mm,when the concentration of the precursor solution was 1.25mol/L.