Study On Preparation And Electromagnetic Properties Of Biomass Carbon-based Microwave Absorbing Materials

With the advent of the 5G era,we have to face a more serious problem of electromagnetic radiation pollution.Designing high-efficiency,broadband and lowdensity absorbing materials has become an effective way to solve electromagnetic radiation pollution.Biomass carbon-based materials come from all aspects in nature,are easy to handle,and their unique structure can increase the structural diversity of carbon materials.We have conducted a series of researches on the preparation of carbon-based microwave absorbing materials based on biomass.The main research contents and results are as follows:(1)We control the heating rate to prepare the carbon material with corncob as the carbon source.The reflection loss(RL)of the sample made at 10?/min at 16.4 GHz at an absorption thickness of 1.6 mm is-46.79 dB;Add KOH,ZnCl2,H3PO4 activators to the reactor to pre-carbonize orange peel to prepare carbon-based materials.Under the action of KOH,the specific surface area of the product can reach 1588.35 m2/g and the absorption thickness is 8.1 mm,the RL can reaches-41.41 dB at 15.92 GHz.(2)The magnetic nano-particle composite carbon material can control its magnetic loss to improve the microwave absorption performance.Corncob-based carbon/Ni The composite material is made of corncob soaked in Ni(NO3)2 · 6H2O carbonized under Ar.Ni particles can increase magnetic loss to improve electromagnetic performance.Pore structure and large surface area play an important role in enhancing microwave absorption performance,which can increase the multiple scattering and reflection of incident electromagnetic waves.Adjust the pore structure and specific surface area of the corncob-based carbon/Ni composite by controlling the quantity of KOH,the product with KOH mass ratio of 1.5 can reach-50.25 dB at 12.00 GHz at an absorption thickness of 8.1 mm.(3)Multi-layer porous corncob-based carbon/Ni composite material is made by carbonizing corncobs under Ar atmosphere.Controlling the milling time can change the particle diameter,surface area and pore size of Ni particles.Increasing the milling time will increase the surface area and decrease the pore size with the Ni particle size,which promotes the multiple reflection and absorption of incident electromagnetic waves and increases the interface between Ni and carbon,and it can ameliorate the electromagnetic loss and impedance matching.The overall microwave absorption performance of the composite material obtained by 2 h ball milling is the best(the absorption capacity(?S)at 1.7 mm is 117.7 dB·GHz)and the absorption efficiency(RE)is 69.24 dB·GHz/mm,5.0 GHz effective absorption bandwidth(fE)and-42.51 dB maximum reflection loss(RLmax)).