Synthesis of Cu and Ni chalcogenides and evaluation of their properties for electromagnetic wave absorption

Abstract

Cu and Ni chalcogenides were synthesized by hydrothermal methods and characterized by XRD and SEM. Their properties on electromagnetic (EM) wave absorption were evaluated by a vector network analyzer with a coaxial measurement. For the Cu_7.2S₄ and Cu₂Se–paraffin systems, the peak for minimum reflection loss (R_L) shifted from high frequency to low frequency as the thickness increases. At a thickness of 1.6 mm, the Cu_7.2S₄–paraffin composite could achieve a R_L value of −36.60 dB at the absorption peak frequency (APF) of 17.2 GHz with a bandwidth of 6 GHz for R_L < −10 dB. For the Cu₂Se–paraffin composite, the R_L value, APF, and bandwidth were −27.5 dB, 11.76 GHz, and 3 GHz, respectively, at a thickness of 1.5 mm. For the NiO, NiS, and NiSe–paraffin composite systems, the APF for minimal R_L moved from high to low frequency as the thickness increases, too. The NiO–paraffin had a R_L of −12.68 dB at the APF of 12.8 GHz when the thickness of the sample was 2 mm. For the NiS–paraffin composite, the R_L value, APF, and bandwidth were −31.93 dB, 7.52 GHz, and 2 GHz, respectively, with a thickness of 3 mm, while the NiSe–paraffin composite had a R_L value, APF, and bandwidth of −41.22 dB, 8.24 GHz, and 1.6 GHz, respectively, with a thickness of 2.2 mm. All Cu and Ni chalcogenides had excellent EM reflection loss, enabling them to be excellent microwave absorbing materials. And most importantly, our results were the first to report superior EM absorption properties for selenides.