Preparation And Properties Of Fe₃O₄/rGO/PANI Composite Particles And The Microwave Absorption Coatings

As new intelligent electronic products have been widely used,more and more serious electromagnetic pollution has important influence on human's healthy life and national military information security.Microwave absorbing material refers to a kind of functional composite material that can absorb electromagnetic wave or convert electromagnetic wave into other forms of energy and consume,and has less reflection and scattering.Compared with common electromagnetic shielding materials,absorbing materials avoid secondary pollution caused by electromagnetic waves reflected into the environment.Therefore,the design and synthesis of"wide frequency,high efficiency and light weight"microwave absorbing materials has been a research hotspot in this field.At present,based on the principle of two-component or multi-component,"broadband,high-efficiency and light weight"powdery microwave absorption materials have been designed and synthesized.For practical application,these high-performance microwave absorbing materials need to be further mixed and doped with polymers to prepare coating materials.However,due to the poor dispersion and uniformity of powdery absorbing materials in the coating,there are still some problems such as poor absorbing performance and narrow effective absorbing bandwidth.In addition,the microwave absorption coating in sand,rain,ice and snow environment,easy to damage or failure,increase the maintenance cost of the microwave absorption coating.In view of the above problems,we have designed and synthesized a new type of"broadband,high-efficiency,light weight"powder microwave absorption material with good dispersion and stability in solution.The microwave absorption coating with high dispersion was further prepared by combing with macromolecule,and the absorption bandwidth and performance stability of the microwave absorption coating were improved by adjusting its surface structure and properties,which laid a foundation for its practical application.The specific research results and innovations are as follows:?1?Fe₃O₄/rGO/rod-shaped PANI ternary composite particles were prepared from Ferric oxide?Fe₃O₄?,Reduced graphene oxide?rGO?and polyaniline?PANI?solutions prepared by solution blending method.The Fe₃O₄/rGO/rod-shaped PANI ternary composite particle shows the characteristics of"broadband,high efficiency and light weight".When the composite material of Fe₃O₄/rGO/PANI particles with rGO content of 15%and paraffin thick is 3.0 mm,its minimum reflection loss?RL?reaches-50.0dB,and its effective absorption bandwidth?QB?reaches 11.4GHz[6.6-18.0].At the same time,the Fe₃O₄/rGO/PANI ternary composite particle has good stability and dispersion in aqueous solution,and can be dispersed and stabilized in water for 2-3 months without precipitation,which lays a foundation for further preparation of high-performance microwave absorption coating.?2?Using self-made Fe₃O₄/rGO/PANI ternary composite particle dispersion solution and commercial waterborne coating as raw materials,microwave absorption coating was prepared by simple blending method,and further microwave absorption coating was prepared by spraying process.The surface roughness of the microwave absorbing coating is controlled by controlling the external magnetic field by using the principle of magnetic particle movement induced by magnetic field.The results showed that the surface roughness?0.069-3.855?m?of the coating increased with the increase of the magnetic field?0-0.632 T?.The effect of coating roughness on microwave absorption performance was studied.The results show that the microwave absorption of the coating increases first and then decreases with the increase of surface roughness,which is attributed to the multiple scattering and absorption of electromagnetic waves caused by surface roughness.When roughness?Sa?is 1.934?m,Fe₃O₄/rGO/PANI/EP coating has a minimum reflection loss of-27.7 dB and an effective absorption bandwidth?RL<-10 dB?of 5.19 GHz[8.26-13.45],which is the maximum value of microwave absorption coating publicly reported at present.?3?A kind of microwave absorption coating with double layer-inclusion structure was designed and prepared.The upper layer is composed of Fe₃O₄@OTS-SiO₂ with low surface energy in the core-shell structure,which not only provides rough surface for microwave absorption coating and increases electromagnetic wave absorption,but also provides super-hydrophobic characteristics for the coating and increases self-cleaning and anti-icing performance of the coating.The lower layer is Fe₃O₄/rGO/PANI doped EP composite coating,which not only provides microwave absorption,but also ACTS as a binder to tightly adhere the upper nanoparticles to the substrate surface,increasing the structural stability of the coating.The results show that this new double-layer inclusion-structure microwave absorption coating not only shows excellent microwave absorption performance,but also shows the minimum reflection loss?RL?of electromagnetic wave of-32.5 dB,and the effective absorption bandwidth is about 13.8 GHz[4.2-18.0],which is the maximum value of the microwave absorption coating in public reports at present.It also shows excellent super hydrophobic characteristics?the contact Angle is 168.9^o,the rolling Angle is about 1^o?,which increases the environmental stability?in the outdoor 7 days,the microwave absorption performance did not change?.