Electrical Insulation And Radar-Wave Absorption Performances Of Nano-Ferrite/Liquid-Silicone-Rubber Composites

In modern military struggles of exploiting radar technology to locate weapons,it is great significance of developing high-performance radar absorbing materials to enable military equipment achieving stealth.In the present study,we develop high radar wave-absorbing composites with a high flexible liquid silicone rubber（LSR）as dielectric matrix,which are composited by filling the nanoscaled ferrites of strontium ferroxide(SrFe₁₂O₁₉)or carbonyl iron（CIP）respectively.Nanofiller dispersivities in SrFe₁₂O₁₉/LSR and CIP/LSR nanocomposites are characterized by scanning electronic microscopy,and the mechanical properties,DC electrical conductivity and dielectric breakdown strength are tested to investigate electrical insulation performances.Compared with pure LSR,SrFe₁₂O₁₉/LSR and CIP/LSR nanocomposites represents slight and acceptable reductions in mechanical tensile strength and electric breakdown field,while render a substantial nonlinearity of electric conductivity under high electric field.Radar wave absorption performances of SrFe₁₂O₁₉/LSR and CIP/LSR composites are evaluated by measuring dielectric and magnetic loss,wave reflectivity,which demonstrates that these two kinds of composite materials are dominated by magnetic losses for radar wave-absorption.With the increase of filling content,the wave-absorption peaks of SrFe₁₂O₁₉/LS and CIP/LSR nanocomposites are shifted to lower frequencies.SrFe₁₂O₁₉/LSR nanocomposites present high wave-absorption performances in the high frequency band of 11～18GHz,in which 7wt%filling content can achieve the minimum reflection loss of-33d B at 11GHz with the effective absorption bandwidth of 10.1GHz.In comparison,CIP/LSR nanocomposites provide high wave-absorption performances in the low frequency band of 2G～8GHz,with a simply 3w%fill content to obtain the minimum reflection loss of-22d B at 7GHz and a remarkably larger effective absorption bandwidth of 3.9GHz.Wave-absorption characteristics of SrFe₁₂O₁₉/LSR and CIP/LSR nanocomposites in single and double layered structures are simulated as implemented by CST electromagnetic software.Radar wave scatterings are simulated to calculate reflectivities for various absorbing layer thicknesses and radar wave incidence angles.SrFe₁₂O₁₉/LSR and CIP/LSR nanocomposites approach the highest wave-absorption performance when their single layer thicknesses reside in 2mm and 3mm respectively.Double-layer absorbing structures are modeled by specifying SrFe₁₂O₁₉/LSR and CIP/LSR nanocomposites respectively as matching and loss layers,which demonstrate the significant improvement of wave-absorption performances can be realized when the thicknesses of match and loss layers are restrained at 1.75mm and 0.25mm respectively.