Application Of Worm Hollow Porous MnO@C/CNTs Composites In Microwave Absorption

In recent years,the rapid development of the modern electronic industry has resulted in the increasingly severe electromagnetic radiation problem.In order to solve electromagnetic radiation,many countries have vigorously developed absorbing materials with good performance.The ideal electromagnetic wave absorbing material converts electromagnetic energy into heat energy and other forms of energy,and realizes attenuation and absorption of electromagnetic waves in a wide frequency band.It has the characteristics of good thermal stability,strong oxidation resistance and light weight.For absorbing materials,the chemical composition of the absorbent and the special microstructure are two key factors affecting the electromagnetic absorbing properties.A new carbon-based material represented by graphene has a high conductivity,thermal conductivity and light weight.However,graphene carbon-based materials alone suffer from impedance matching problems.Therefore,a special porous structure is used in combination with both carbon materials in order to achieve new discoveries in the field of absorbing materials.The manganese carbonate is calcined into a porous manganese oxide template,and then the acetylene gas is introduced to serve as a carbon source to quantitatively coat the template.A series of porous microspheres with different carbon contents are obtained by controlling the time of acetylene introduction.Via scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffractometer,Raman spectrometer,pore size and specific surface area analyzer and thermogravimetric equipment are used to observe the morphology,structure,carbon crystallinity,element composition and material of the samples under different carbon contents.The characterization results show that the carbon coated manganese oxide microspheres are porous structures,and the carbon layer thickness can be controlled by the carbon source time.Samples of carbon materials prepared by chemical vapor deposition have the same chemical composition,slightly different degrees of graphitization,and contain a large amount of amorphous carbon.In order to obtain the best electromagnetic wave absorption performance,the experimental conditions are adjusted differently.Finally,when the material is carbonized at 600~oC,the access time of acetylene is controlled at 10min,and the mass fraction of paraffin wax is 40%,the prepared sample has the best absorbing effect.At a thickness of3.8mm,the strongest reflection loss is-60.5d B and the effective absorbing bandwidth is14.2GHz over the simulated thickness range.The presence of the carbon layer in the composite material has a significant improvement in the absorbing effect.Also,the unique porous structures provide good impedance matching.Manganese oxide and porous structures bring multiple reflections of electromagnetic waves,which are beneficial to interfacial polarization and relaxation,and provide a possibility for materials to have good absorbing properties.More importantly,this study provides an idea and direction to effectively regulate the absorbing properties by controlling the carbon content.