| With the continuous development of science and technology,the use of electronic equipment is increasing,and the electromagnetic(EM)interference and radiation generated by some high-power EM radiation sources will affect the operation of equipment and human health.Electromagnetic wave(EMW)absorbing materials can convert EM energy into other forms of energy to achieve the attenuation of EMWs.Therefore,the research of efficient EMW absorbing materials has attracted widespread attention.EMW absorbing materials are mainly composed of EMW absorbers and matrix materials.EMW absorber is mainly used to consume EMW energy,and the matrix material is mainly used for bonding and dispersing EMW absorber.With the complexity and diversity of the environment,the material is required to have strong EMW absorption performance,but also has certain mechanical properties,thermal stability and corrosion resistance,especially the EMW absorption material is required to have low density,so as to reduce the weight of the device.In this thesis,PEEK/C/Fe Co composite foams and PEEK/C/Ni porous composites were prepared by the thermal phase separation technology,solution blending and in-situ electrochemical deposition using polyetheretherketone(PEEK)as the matrix of the EMW absorbing materials,and the morphology,EM parameters and EMW absorption performance of the composite were studied.Firstly,a series of PEEK/C/Fe Co composite foams with different densities and content were prepared by combining the thermal phase separation technology and solution blending by the graphite and magnetic Fe Co particles as the filler of EMW absorber and the PEEK foam as the matrix.The porous structure of PEEK foam can promote the refraction and reflection of incident EMWs,while the content of graphite and Fe Co particles will improve the dielectric constant and magnetic permeability of the composite foam,which in turn affects the EMW absorption performance of the foam.The prepared PEEK-50/C-40/Fe Co-10 composite EMW absorbing material with a density of 0.49 g/cm~3 has a wide absorption frequency and relatively strong reflection loss,the maximum reflection loss at 14.9 GHz is-35.9 d B,the matching thickness is1.5 mm,and the effective absorption bandwidth reaches 3.6 GHz(12.9-16.5 GHz).In addition,with the PEEK foam as the matrix material,the compressive strength of the composite EMW absorbing material is 6.40 MPa and is stable at 400°C.Porous PEEK/C composites were prepared by combining thermal phase separation technology and solution blending,and then nickel nanoparticles were introduced into the porous structure of the porous materials by electrochemical deposition to obtain PEEK/C/Ni composite foams containing different nickel content.The nickel particles are attached to the graphite flakes and PEEK,providing a certain degree of magnetism,which affects the EMW absorption performance of composite foam.The prepared PEEK/C/Ni-12.4 composite EMW absorbing material has the best EMW absorption performance,its maximum reflection loss at 8.9 GHz is-45.1 d B,the matching thickness is 2.5 mm,and the effective absorption bandwidth reaches 2.4 GHz.At the same time,the PEEK/C/Ni-12.4 composite EMW absorbing material also has good impedance matching and strong attenuation characteristics,and can adjust the matching thickness in the frequency range of 4-18 GHz to achieve effective absorption of EMWs.The PEEK/C/Ni-12.4 composite also has a compressive strength of 10.88 MPa and good thermal stability at 500°C,and have a low density of 0.54 g/cm~3,which meets the requirements of high-performance EMW absorbing materials.The composite foam prepared in this thesis has the advantages of light weight,high strength and good EMW absorption performance,which can adapt to more complex and harsh use environments,and also provides a new method for the development of high-performance EMW absorbing materials. |
