Construction Of Carbon/iron-cobalt Magnetic Metal Composite Absorbent

With the development of information technology and military industry,electromagnetic radiation has become an increasingly troublesome problem.In order to solve these problems,absorbing materials have been paid more attention.Ferrite and magnetic alloy is the most widely used magnetic absorbing material,but the single magnetic materials absorbing effect does not meet the requirements of "thin light wide strong",in order to achieve better absorbing effect,general requirements to composite dielectric performance good and magnetic materials up was prepared with magnetic loss performance and absorbing materials possess the properties of dielectric loss.Sol-gel method is a common method for preparing nanomaterials.It is simple and low-cost.Aiming at the shortcoming of single morphology and narrow application range of traditional absorbing materials,carbon/iron-cobalt alloy composite absorbing agents and three-dimensional composite absorbing agents with nanowire morphology were prepared by sol-gel method combined with subsequent solid phase sintering.At the same time,we also discuss the formation of the morphology,the influence of various parameters in the preparation process on the absorption performance and the corresponding absorption mechanism.The CoFe₂O₄ precursor was prepared from citric acid,cobalt nitrate and ferric nitrate by sol-gel self-propagating method.The precursor was mixed with urea and go solutions in different proportions and sintered at 900? in solid phase to obtain CoFe nanowires with diameter of about 20 nm and length of about 5 ?m.Nanowires are usually attached to r GO sheets,and the nanowires are uniform and dispersed in size.The CoFe nanowires grown on the carbon sheet have excellent absorbing performance.The peak value of reflection loss is lower than-10 dB at each thickness of 2?5 mm.The lowest peak value occurs at the thickness of 3.5mm and 7.2 GHz,reaching-36 dB.However,the lowest peak value of the agglomerated wave-absorbing material only reached-10 dB at 2.5-4.5mm,and the lowest peak value was-11 dB at 3mm and 5.9GHz,and the maximum effective bandwidth was only 1.5 GHz.Using citric acid,nickel nitrate and ferric nitrate as raw materials,CoFe₂O₄ precursor was prepared by sol-gel self-propagating method.RF precursor was preparedby mixing resorcinol and formaldehyde solution.The ratio of the two was adjusted and C@CoFe was prepared by heat treatment at 600? and 900?,respectively.When the mass ratio of RF and metal-citric acid precursor is 1:1 and the C@CoFe is obtained by heat treatment at 600?,its absorbing performance is poor and no reflection loss reaches-10 dB within 2?18GHz.When the temperature reaches 900?,the absorptive material obtained under this reaction condition is only 2 mm thick,and the reflection loss in the range of 16?18 GHz is below-10 dB,and the maximum reflection loss on electromagnetic wave reaches-15.8 dB.When we adjusted the ratio of reactants to the mass ratio of RF and metal-citric acid precursor 2:1,the maximum reflection loss of C@CoFe obtained by heat treatment at 600? from 2?9.5 GHz at 2?5 mm was over-10 dB.When the thickness reaches 2 mm,the maximum reflection loss of 9.5 GHz electromagnetic wave reaches-21 dB,and the maximum effective bandwidth of 5 GHz also appears at this time.When the C@CoFe obtained after 900? heat treatment,when the thickness of the absorbing materal changes between 2 and 5 mm,the maximum reflection loss of the absorbent on the electromagnetic wave with frequency of 4?18GHz only exceeds-10 dB.Under this reaction condition,when the thickness of the obtained absorbing material is 4.5mm,the maximum reflection loss of electromagnetic wave at 5.7 GHz reaches-38 dB,and the maximum effective bandwidth is only 2 GHz,which also appears at this time.Go gel was prepared by freeze-drying method,then the mixed solution of CoFe₂O₄ precursor and RF precursor was filled into go gel by sol-gel method,and finally C@CoFe /rGO foam was obtained by heat treatment at 600?.The product has a distinct core-shell structure attached to the r GO sheet,and Co and Fe elements are uniformly distributed in the foam.When the absorptive material thickness is 2.53 mm,the peak value of the lowest reflection loss at 14.6GHz can reach-46.2dB,and the effective absorptive bandwidth reaches 7GHz at 2.53 mm.Similar to the C@CoFe prepared in the above part,the reflection loss and effective bandwidth are greatly improved at 600?,and this Three-dimensional structure has more application scenarios.