【摘 要】
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The increasing electromagnetic hazards including electromagnetic interference and electro-magnetic pollution,which were stemmed from massive usage of electromagnetic technology,have triggered widespread concerns.To cope with this challenge,electromagnetic
【机 构】
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Science and Technology on Advanced Functional Composite Laboratory,Aerospace Research Institute of M
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The increasing electromagnetic hazards including electromagnetic interference and electro-magnetic pollution,which were stemmed from massive usage of electromagnetic technology,have triggered widespread concerns.To cope with this challenge,electromagnetic wave absorbing materials with high performance are greatly needed.Composite construction has been widely applied in electromagnetic (EM) wave absorbing materials to achieve high per-mittivity,high permeability and impedance matching.However,high-temperature stability,oxidation and corrosion resistance are still unignorable issues.Herein,high entropy hexa-borides/tetraborides (HE REB6/HE REB4) composites with synergistic dielectric and magnetic losses were designed and successfully synthesized through a one-step boron carbide reduction method.The five as-prepared (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)B6/(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)B4,(Y0.2Nd0.2Sm0.2 Er0.2Yb0.2)B6/ (Y0.2Nd0.2Sm0.2Er0.2Yb0.2)B4,(Y0.2Nd0.2Eu0.2Er0.2Yb0.2)B6/ (Y0.2Nd0.2Eu0.2Er0.2Yb0.2)B4,(Nd0.2 Sm0.2 Eu0.2 Er0.2Yb0.2)B6/ (Nd0.2 Sm0.2 Eu0.2 Er0.2Yb0.2)B4 and (Y0.2 Sm0.2 Eu0.2 Er0.2Yb0.2)B6/(Y0.2 Sm0.2 Eu0.2 Er0.2Yb0.2)B4 contain two phases of HE REB6 and HE REB4.Among them (Y0.2 Nd0.2Sm0.2 Eu0.2 Er0.2)B6/ (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)B4 (HE REB6/ HE REB4-1) and (Y0.2Nd0.2Sm0.2Er0.2Yb0.2)B6/(Y0.2Nd0.2Sm0.2Er0.2Yb0.2)B4 (HE REB6/ HE REB4-2) exhibit excellent EM wave absorption proper-ties.The optimal minimum reflection loss (RLmin) and effective absorption bandwidth (EAB) of HE REB6/HE REB4-1 and HE REB6/HE REB4-2 are-53.3 dB (at 1.7 mm),4.2 GHz (at 1.5 mm) and-43.5 dB(1.3 mm),4.2 GHz (1.5 mm),respectively.The combination of conducting HE REB4 with magnetism into HE REB6 as a second phase enhances dielectric and magnetic losses,which lead to enhanced EM wave absorption performance.Considering superior high-temperature stability,oxidation and corrosion resistance of HE REB6 and HE REB4,HE REB6/HE REB4 composite ceramics are promising as a new type of high-performance EM wave absorbing materials.
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