Construction Of P-CIP@PANI Magnetic Particles And Microwave Absorbing Properties Of Composite Materials

Electromagnetic pollution will not only cause malfunction of electronic equipment and leakage of computer information,but also cause harm to human body's physical and mental health.In particular,how can we effectively avoid the detection of enemy radars in the military is particularly important for winning the war.Absorbing materials can effectively absorb electromagnetic waves,and convert electromagnetic energy into other energy(such as heat energy)and dissipate,which can not only achieve stealth function but also eliminate electromagnetic pollution.However,the single electric loss and magnetic loss materials have no obvious advantages in absorbing performance and effective bandwidth.Moreover,the traditional ferrite absorbers have a high density and a narrow absorption band and are difficult to satisfy the current stealth weapons."Light,wide,strong,thin" requirements.The use of electrical loss and magnetic loss materials composite construction of porous carbonyl iron powder@polyaniline(p-CIP@PANI)magnetic particle adjustment material impedance matching,and the use of porous particles to increase the electromagnetic wave reflection interface to extend the reflection path of the electromagnetic wave inside the material;and further to prepare three-way wave absorbing functional materials by solution blending method with multi-walled carbon nanotubes and graphene,respectively;The microstructure and absorption properties of EP composites were tested and characterized.The results are as follows:(1)The porous carbonyl iron powder was prepared by chemical etching of spherical carbonyl iron powder with a size of 2.5~3.5 ?m using an acid etching solution of citric acid and ferric chloride monohydrate.The quality was reduced by 40% compared to carbonyl iron powder that had not been subjected to acid etching.Scanning electron microscopy showed that polyaniline was coated on the surface of porous carbonyl iron powder to form a "core-shell" structure.When m(AN):m(p-CIP)=2:1,p-CIP@PANI particles were densely covered.Due to the presence of polyaniline,the saturation magnetization(MS)of p-CIP@PANI is 141.5 emu/g,which is a decrease of 33% compared with MS of porous CIP,and the coercive force is 2.2 Oe,which is much lower than that of porous CIP coercivity(6.7 emu/g).(2)The microwave-absorbing properties of p-CIP@PANI/multi-walled carbon nanotube epoxy composites are improved compared with single-wall carbon nanotube/epoxy composites.The strongest absorption value of epoxy composites with 5wt% pure multi-walled carbon nanotubes is greater than-5 dB,and the microwave absorbing properties are poor.With the introduction of p-CIP@PANI,the microwave absorbing properties of the composites are enhanced.When the material thickness is 2.5 mm and the p-CIP@PANI content is 30 wt%,the strongest absorption at 9.3 GHz reaches-19.7 dB,corresponding to an effective absorption band of about 3.2 GHz(8.2 to 11.4 GHz).When the amount of p-CIP@PANI was increased to 40 wt%,the strongest absorption of the composite increased to-31.5 dB at 8.82 GHz,but the effective absorption band was reduced to 2.9 GHz(7.55 to 10.54 GHz).The introduction of multi-walled carbon nanotubes facilitates the connection of p-CIP@PANI in the matrix to form a three-dimensional conductive network structure,and increases the electrical loss of the incident electromagnetic waves by the absorbing materials.(3)The microwave-absorbing properties of p-CIP@PANI/graphene epoxy resin composites are improved compared to that of single graphene/epoxy resin composites.The strongest absorption at 9.7 GHz is-9.5 dB for pure epoxy resin based composites with 5 wt% graphene content.With the introduction of p-CIP@PANI,the microwave absorbing properties of the composites are enhanced.When the thickness of the sample is 3.5 mm and the p-CIP@PANI is 40 wt%,the strongest absorption at 6.8 GHz is-44.3 dB.The corresponding effective absorption band is about 3.1 GHz(5.2~8.3 GHz),and when the thickness is 2 mm,the strongest absorption value reaches-30.3 dB at 12.8 GHz,corresponding to an effective absorption band of about 4.6 GHz(10.2~14.8 GHz).The core-shell structure of p-CIP@PANI magnetic particles and electrical loss-type graphene act synergistically to improve the impedance matching of the material.At the same time,the interfaces between the graphene sheets,p-CIP@PANI,and the resin matrix cause interfacial polarization relaxation?depolarization enhanced loss.(4)When the content of p-CIP@PANI is 40 wt%,graphene and multi-walled carbon nanotubes with mass fraction of 5 wt% are added respectively.The input impedance of the multi-wall carbon nanotube composite system when the impedance imaginary part of the composite system approaches zero.The real part is 581.4 ?,and the real part of the input impedance of the graphene composite system is 449.6 ?,which is closer to the real part of the air impedance 377 ?,and the impedance matching is better.The effective bandwidth of the graphene composite system is 4.6 GHz,which is also significantly better than that of the multi-wall carbon nanotube composite system.The effective bandwidth is 3.2 GHz.The composite graphene and porous magnetic particles have more excellent microwave absorbing properties.Graphene has large specific surface area,surface defects,high dielectric loss,better dielectric constant and permeability than carbon nanotubes.In addition to the formation of a strong conductive network in the composite,it can also pass through the interface polarization mechanism and defects polarization to lose electromagnetic waves.