Island-like nickel/carbon nanocomposites as potential microwave absorbers—Synthesis via in situ solid phase route and investigation of electromagnetic properties

Abstract In this work, nickel–carbon (Ni/C) nanocomposites were prepared facilely as potential light-weight microwave absorbers via the calcination of nickel nitrate–polyacrylamide mixture in flowing ammonia. The electromagnetic properties of as-prepared Ni/C nanocomposites were investigated in relation to their composition and microstructure. Findings indicate that as-prepared Ni/C nanocomposites are of island-like morphology and consist of uniformly dispersed Ni nanoparticles and porous carbon medium. The electromagnetic properties of Ni/C nanocomposites are highly dependent on calcination temperature; and the Ni/C nanocomposite obtained at 600 °C exhibits excellent electromagnetic properties. This is attributed to the special porous structure and desired electromagnetic impedance matching of the carbon medium as well as the uniform dispersion of Ni nanoparticles in the carbon medium. Namely, the carbon medium is accessible to induced multi-dielectric polarization thereby improving the microwave absorbing properties of the Ni/C nanocomposites, and it also contributes to improving the thermal stability, chemical stability, and dielectric performance of the nanocomposites while the intrinsic magnetic properties of metallic Ni are retained.