Preparation And Properties Of Electrical/magnetic Loss Absorbing Materials

The electronic equipment in people's lives will produce electromagnetic pollution while providing convenience,which will affect people's health and the use of some precision instruments.Therefore,there is an urgent demand for highperformance absorbing materials,and they are also used in anti-reconnaissance and other fields.Cobalt ferrite is a potential magnetic loss absorbing material with unique spinel structure,stable properties and simple preparation.Whereas,cobalt ferrite has some shortcomings,such as lower absorption intensity,small width of absorption band and the impedance matching is not so good,which gives some limitation to the application of cobalt ferrite materials.The introduction of electrical loss absorbing materials has broadened the research road in the field of electromagnetic wave absorbing materials.Use the excellent magnetic properties of magnetic materials and the excellent electrical properties of electrical lossy materials to complement each other,the impedance matching degree of this time is improved under the synergy of the two,which makes the electromagnetic wave absorption performance can be correspondingly improved compared with before.It is of great significance to further explore the direction of the combination of electrical/magnetic loss materials to broaden the practical application of electromagnetic wave absorption materials.This thesis combines cobalt ferrite,a magnetic material,with carbon fibers prepared by electrospinning,barium titanate fibers,and silver nanoparticles prepared by the reaction of silver mirrors to prepare carbon/cobalt ferrite(C/CFO),silver/cobalt ferrite(Ag/CFO),barium titanate/cobalt ferrite(BTO/CFO)nanocomposites.And use common characterization methods such as XRD,FT-IR,Raman,SEM,XPS and TGDSC to test and characterize the composition,element valence and morphology of the obtained samples.VSM were applied to characterize the samples' magnetic properties and VAN were used for the representation of absorbing properties of the samples.The results are as follows:1.Carbon fibers were prepared by electrospinning combined with carbonization technology,and C/CFO nanocomposites were prepared by hydrothermal technology.The results show that in the C/CFO nanocomposite,the cobalt ferrite grows on the surface of the carbon fiber with a homogeneous distribution.With the increase of the proportion of cobalt ferrite,the saturation magnetization is grow from 13.71 emu/g to56.64 emu/g,and the coercivity is grow from 284.92 Oe to 733.06 Oe.The corresponding RL value of the sample increases first and then decreases.C/CFO-10 has the best RL value when the thickness is 2.6 mm under the frequency parameters set in the test process(2 GHz-18 GHz),reaching-137 d B,and the effective absorption bandwidth(RL <-10 d B)is 11.44 GHz.2.The silver nanoparticles are grown on the cobalt ferrite prepared by the hydrothermal technology through the silver mirror reaction,and then the Ag/CFO nanomaterial is prepared.The result shows that the silver nanoparticles grow uniformly on the surface of cobalt ferrite.With the increase of non-magnetic Ag in the sample,the saturation magnetization of the composite nanomaterial decreased from48.72 emu/g to 21.84 emu/g.The coercivity of the composite sample changed slightly from 938.63 Oe to 923.95 Oe.The reflection loss RL of Ag/CFO-6 at 2.9 mm has the best value of-83.55 d B at 5.83 GHz,and the effective absorption bandwidth is 4.13 GHz.3.Electrospinning technology was used to prepare BTO fiber,combined with hydrothermal technology to prepare BTO/CFO nanocomposite.The results show that,the saturation magnetization of the sample decreases from 21.53 emu /g to 14.66 emu/g,and the coercivity increases from 755.75 Oe to 891.22 Oe when the content of barium titanate increases.When the thickness of the BTO/CFO-10 nanocomposite is3.0 mm,the RL reaches-27.87 d B,and the microwave absorption performance behave well.