An efficient high-frequency electromagnetic wave absorber: Nickel-N@Carbon composite

The nickel-N@carbon composite (Ni-N@C) with size of 4.0-5.0 mm was prepared, in which the Ni-N bonds were formed in the carbonization process. The Ni-N bonds between metallic Ni and N provide different surface electron distribution and contribute to the high-frequency electromagnetic wave absorption (EMWA) of Ni-N@C composite. The Ni-N bonds in the Ni-N@C composite have been confirmed by X-ray diffraction, Raman spectrum, X-ray photoelectron spectroscopy. Compared with Ni@C composite and reported Ni-based materials, the Ni-N@C composite shows the stronger reflection loss (RL = -32.31 dB) and wider effective absorption band (EAB, RL < -10 dB) at the high frequency (12.79 -18 GHz), which can be ascribed to Ni-N bonds. Besides, the EMWA characteristics of Ni-N@C composites are flexibly adjusted by tuning the pyrrole monomers to obtain optimized impedance matching, which is beneficial for broadening the EAB. All C, X and Ku bands (3.90-18.0 GHz) can be covered through changing the Ni content and layer thickness for Ni-N@C composites. (C) 2019 Elsevier B.V. All rights reserved.