Microwave Absorption Performance Of Magnetic Fibers Prepared By Sol-Gel Method

Ferrite and metal powder are the most widely used magnetic absorbing materials.They have the dual properties of dielectric materials and ferromagnetic materials,and can absorb electromagnetic waves through dielectric loss and magnetic loss.However,conventional ferrite powders and metal powder absorbers have the disadvantages of high density and narrow effective absorption bandwidth.In order to reduce the density and improve the microwave absorption performance of ferrite and metal powder,magnetic fibers were prepared by sol-gel method and electrospinning technology.The absorbing properties and absorbing mechanisms were studied.The effects of parameters on absorbing properties were discussed.CoFe₂O₄ nanofibers and nanoparticles were prepared by sol-gel method and electrospinning technique using citric acid,cobalt nitrate and ferric nitrate as raw materials.The nanofiber density is about 1/10 of that of the nanoparticles.CoFe₂O₄nanofibers have a typical one-dimensional nanostructure,which is arranged in a one-dimensional direction by many nanoparticles.CoFe₂O₄ nanoparticles are not uniform in size.CoFe₂O₄ nanofibers have excellent absorbing properties.The peak value of reflection loss is less than-10dB at each thickness,the lowest peak value is-37dB,and the maximum absorption bandwidth is 10GHz.The peak value of the reflection loss of CoFe₂O₄ nanoparticles is lower than-10 dB only when the sample thickness is 2mm and2.5mm.,the lowest peak value is-25.5 dB,and the maximum absorption bandwidth is 4.8GHz.Fe₃Ni alloy nanofibers were prepared by sol-gel method and electrospinning technique using citric acid,nickel nitrate and ferric nitrate as raw materials.The product has a distinct fiber structure and less impurities when the heat treatment temperature is800°C.The Fe₃Ni alloy fiber has high dielectric constant because of high electrical conductivity.When the fiber content is 50%,the dielectric constant increases sharply,destroying the impedance matching,and the electromagnetic wave is largely reflected on the surface of the material.The ring sample with a content of 33%has good absorbing properties.When the heat treatment temperature is 600°C,the lowest reflection peak value is-15dB,and the maximum absorption bandwidth is 5GHz.When the heat treatment temperature is 800°C,the lowest reflection peak value is-15dB.The maximum absorption bandwidth is 3GHz.Fe₂Ni alloy nanofibers were prepared by sol-gel method and electrospinning technique with citric acid,nickel nitrate and ferric nitrate as raw materials.The effects of citric acid content and heat treatment temperature on the absorbing properties of Fe₂Ni alloy fibers were investigated.The viscosity of the spinning solution increases as the citric acid content increases,and lead to cross-linking of fibers.The Fe₂Ni alloy fiber has excellent absorbing properties,except the sample with 2 mol of citric acid,heat treatment temperature of 800°C,and a fiber content of 33%,the loss peak of each sample under each thickness is less than-10dB.