Preparation And Microwave Absorption Properties Of Barium Ferrite@Hollow Microspheres/Carbon Nanotube Composites

As a kind of functional materials which could absorb the electromagnetic waves,Theabsorbing materials have been the key military materials studied by various countries.However,the traditional absorbing materials cannot meet the needs in many cases due to their single function.In order to meet the daily needs of military and human beings,many countries are trying to develop new absorbing materials with strong absorption capacity,light materials,high absorption frequency band and thin coating.As a common absorbing material,traditional ferrite has the disadvantages of high density and narrow absorption band.Carbon nanotubes,as a two-dimensional nanomaterial,which are excellent absorbing materials and widely used in various fields.In this paper,considering the complementary characteristics of the absorbing mechanism.including the magnetic loss performance of barium ferrite,the dielectric loss of carbon nanotubes and the light characteristics of hollow microspheres,a barium ferrite/carbon nanotube was prepared.then the binary composite material was composited with the hollow microspheres to obtain a barium ferrite@hollow microsphere/carbon nanotube ternary composite powder.The phase,structure,morphology and electromagnetic properties of the composite powders were characterized by XRD,SEM,XPS and VNA.The effects of composite amount,process and strontium on the absorbing properties of the composites were investigated.The main results are as follows:Firstly,a series of BaFe₁₂O₁₉/CNTs composite powders were prepared.The influence of barium ferrite type,carbon nanotube content and composite process on the absorbing properties of composite powders has been studied,which shows that the composite powder of BaFe₁₂O₁₉/5wt%CNTs obtained by the composite method of adding surface modifier has the best absorbing property.When the coating thickness is 2 mm,the maximum reflectivity is-36.6dB as the frequency of 9.4 GHz,the frequency band less than-10 dB is 8.4 GHz to 10.3 GHz,and the bandwidth is 1.9 GHz;the Ba_0.5Sr_0.5Fe₁₂O₁₉/CNTs composite obtained after doping the strontium has a larger absorption and bandwidth than the composite powder before.Secondly,BaFe₁₂O₁₉@hollow microspheres?HM?/CNTs composites were prepared.The effect of the amount of hollow microspheres on the absorbing properties was investigated.The appropriate amount of microspheres can improve the absorbing reflectivity of the composite powder,and too much or few microspheres are not beneficial to improving the absorbing reflectance,and the BaFe₁₂O₁₉@20wt%HM/5wt%CNTs composite powder has the best absorbing properties.When the coating thickness is 2 mm,it has the largest absorbing reflection of-26.9 dB at 8.7 GHz,and the frequency band of less than-10 dB is between 7.7 GHz and 9.7GHz with the bandwidth is 2.0 GHz.Finally,the Ba_0.5Sr_0.5Fe₁₂O₁₉@20wt%HM/5wt%CNTs composite powder was obtained by doping the strontium element.After simulating the influence of the coating thickness,it was found that the composite powder had better absorbing properties than before doping,and have a large absorption peak at multiple coating thicknesses.When the thickness is 0.6 mm,the composite powder has the best absorbing property,the largest absorbing peak at-41.9 dB as the frequency of 13.2 GHz,and the frequency band less than-10 dB is 12.8 GHz to 15.3 GHz with the bandwidth of 2.5 GHz.