Atomic-scale elucidation of attenuation mechanisms underlying exceptional electromagnetic wave absorption of SiZrBCN ceramic nanocompositesOA

To elucidate the atomic-scale mechanisms governing electromagnetic wave(EMW)attenuation in polymer-derived ceramics,a SiZrBCN ceramic nanocomposite was prepared via chemical modification of polyborosilazane with tetrakis(dimethylamino)zirconium(IV),followed by pyrolysis and annealing.Advanced characterization methods combined with first-principles calculations via density functional theory(DFT)were employed to investigate the structural evolution,dielectric properties,and attenuation mechanisms of the nanocomposites.The results show that after pyrolysis at T≤1400℃,the SiZrBCN is in an amorphous state.As the annealing temperature increases,ZrC_(x)N_(1−x),SiC,andβ-Si_(3)N_(4)initially precipitate at 1500℃.When the temperature increases to 1800℃,ZrC_(x)N_(1−x)transforms into ZrB_(2),forming SiC/ZrB_(2)multiphase ceramic nanocomposites.With the incorporation of Zr,SiZrBCN-16,after annealing at 1600℃,exhibits excellent EMW absorption performance,achieving a maximum effective absorption bandwidth of 6.03 GHz(thickness:1.65 mm)and a minimum reflection loss of−44.1 dB(thickness:1.9 mm).In addition to the conductive loss caused by the free carbon network,DFT analysis revealed two primary dielectric loss mechanisms that result in exceptional absorbing performance:(1)Electronegativity-driven charge separation in ZrC_(x)N_(1−x)solid solutions facilitates the formation of electric dipoles;(2)interfacial lattice distortion and atomic disparity across the interface at the ZrC(001)/β-Si_(3)N_(4)(001)and ZrN(100)/SiC(110)boundaries induce electronic reconstruction and charge separation.