Preparation Of Hollow Carbon Microsphere-based Composites And Research On Its Microwave Absorbing Properties

Carbon-based materials such as graphene,carbon nanotubes,and carbon fibers limit their application in the field of microwave absorption due to their raw materials non-renewable and other shortcomings.Porous carbon materials such as biochar can reduce the density of the material on the one hand,and increase the number of reflections and scattering of electromagnetic waves in the holes on the other hand.In the research of porous carbon,the hollow carbon ball-based absorbing materials prepared by the soft template method are seldom studied.Therefore,in this paper,glucose is used as the carbon source,the hollow carbon sphere precursor is prepared by the soft template method,and the hollow carbon sphere-based composite material with good absorbing performance is prepared by liquid-phase reduction and hydrothermal methods,and its characterization and absorbing properties are carried out.Exploration of the mechanism.Using P123 and SO as the soft template and glucose as the carbon source,a hollow carbon microsphere precursor with a relatively uniform particle size(about 2?m)was prepared by adjusting the ratio and concentration of the two surfactants.By controlling the carbonization temperature to adjust the dielectric properties of the hollow carbon spheres,hollow carbon microspheres with good microwave absorbing properties are obtained.The minimum reflection loss of the sample obtained at 800°C is-32.19dB.In order to improve the wave-absorbing performance and impedancematching of hollow carbon spheres,magnetic metal and hollow carbon spheres are compounded together to prepare composite materials.First,the carbonized carbon balls were surface treated with different oxidants,and then the HCS/Ni composite material was prepared by the hydrothermal reduction method.Among them,the HCS/Ni composite material prepared with carbon balls oxidized and treated with concentrated sulfuric acid and concentrated nitric acid has a minimum reflection loss of-54.6dB,but its impedance matching performance still needs to be improved.Since the surface of the hollow carbon microsphere precursor contains residual oxygen-containing functional groups,the cobalt metal is compounded on the surface of the hollow carbon microsphere precursor by means of electrostatic self-assembly,and then it is calcined at a high temperature.The amount of cobalt salt added affects the electromagnetic parameters of the composite material,thereby affecting the wave-absorbing performance.Compared with HCS-800?,HCS/Co-1 has improved performance in terms of minimum reflection loss,thickness,band width,and impedance matching.The minimum reflection loss reaches-44dB,the thickness is 1.8mm,and the corresponding effective absorption bandwidth is 4.6GHz.The impedance matching value of the composite material is around 1,which is well improved.Because the microstructure of the composite material has an important influence on the absorbing performance,the MoS₂/HCS composite material was prepared by the hydrothermal method,and the molybdenum disulfide was petal-shaped covering the surface of the hollow carbon sphere.This structure is the multiple reflection of electromagnetic waves and Scattering provides the basis.The thickness of the molybdenum disulfide shell affects the dielectric constant of the composite material and thus has an impact on t he microwave absorbing performance.The minimum of HCS/MoS₂-1 is-44.6GHz,and the corresponding effective absorption bandwidth is 4.6GHz.In addition,in the entire C,X and Ku absorption bands,when the thickness is changed from 2.0 to 5.5 mm,the RL value is all less than-20dB.Impedance matching has also been well improved.Because the ternary composite material can introduce more polarization mechanisms,which is conducive to the attenuation of electromagnetic waves,the ternary composite material is prepared by combining HCS with Co and MoS₂.The minimum reflection loss of HCS/MoS₂/Co-1 is-37GHz,the corresponding frequency is 10.88GHz,the matching thickness is 2.9mm,and the corresponding effective absorption bandwidth is 3.2GHz.However,its impedance matching is no better than binary composite materials,and its process optimization needs to be further explored.