FeNi@C Powder And Their Composites And Microwave Absorbing Properties

For the development of radar wave absorbing materials"thin,wide,light,and strong"requirements,taking into account the dual function of wave absorption and load-bearing structural wave absorbing materials,has become a very important research direction in the field of wave absorbing materials and composite materials.In the case of meeting the requirements of mechanical properties,how to improve the absorbing effect of absorbing materials and broaden their absorption band has become the focus of research on structural absorbing materials.In this paper,the FeNi@C composite powder with both dielectric and magnetic loss mechanisms was first developed,and the wave absorption characteristics of the composite powder were studied.Then,the FeNi@C/glass fiber/epoxy absorbing composite material and its laminate with glass fiber/epoxy resin were successfully prepared through a combination of magnetic separation and dense blending techniques,and the radar wave absorbing characteristics of the absorbing composites and laminates were studied in turn,and the FeNi@C composite powder content and laminate structure of the absorbing composites were optimized according to the wave absorbing characteristics.Finally,a structural composite with broadband wave absorption characteristics was prepared.The FeNi@C composite powder has a balance of dielectric and magnetic loss mechanisms,with a dielectric constant imaginary partε′′of about 2.44-0.44,a tanδ_εof0.25-0.06,a magnetic permeability imaginary partμ′′of about 0.25-0.13,and a tanδ_μof 0.25-0.13 in the frequency range of 2 to 14 GHz.FeNi@C has a high attenuation constant for electromagnetic waves and good impedance matching properties.FeNi@C composite powder with a thickness of 1.5 mm has the strongest absorption peak of-15.15 d B at 15.82 GHz,and the composite powder with a thickness of 1.6 mm achieves effective absorption in the 12.11 GHz–18 GHz band with a maximum effective absorption bandwidth of 5.89 GHz.The structural absorbing composite laminate is a"glass fiber layer/absorbing layer/glass fiber layer"sandwich structure.The thickness of the absorbing layer determines the absorption peak strength of the laminate;the mechanical properties of the laminate are determined by the glass fiber layer;and the thickness of the glass fiber layer matches the thickness of the absorbing layer as the main factor for the effective absorption peak width of the laminate.The laminate has the best overall performance when the total thickness of the laminate is 2 mm and the thickness of the absorbing layer is 1.2 mm,with a tensile strength of 183.54 MPa,the strongest absorption peak of-29.32 d B at 14.67 GHz,and a maximum effective absorption bandwidth of 5.09GHz.