-irradiation induced ultrafine Ni nanoparticles supported on biomass-derived macroporous carbon for enhanced microwave absorption in the X-band

A series of ultrafine Ni nanoparticles (NPs) supported on biomass-derived macroporous carbon composites are conducted by gamma-irradiation induced reduction method. The scanning electron microscopy (SEM) and transmission electron microscope (TEM) characterization show that the obtained materials have abundant macroporous structure and the Ni NPs are evenly decorated on the surface of macroporous carbon. Both high irradiation doses and increasing Ni2+ contents favor the production of smaller dots. When the irradiation dose is 220 kGy and the C/Ni2+ mole ratio is 1:6, the average diameter of Ni NPs can reach 7.7 nm. Electromagnetic analyses indicate that the ultrafine Ni NPs have a positive effect on the magnetic loss ability, due to their strong natural ferromagnetic resonances. The obtained sample (CSC-Ni-3) exhibits the best microwave absorption performances among these composites, with the strongest reflection loss (RL) value of -70.2 dB at 10.8 GHz for the thickness of 2.3 mm, and the effective absorption band (EAB) in the X-band (8.2-12.4 GHz) is up to 3.2 GHz. The advantages of CSC-Ni-3 can be clearly established in both matched impedance and high magnetic loss ability. The gamma-irradiation strategy presents a promising way for the design of ultrafine Ni NPs for high-performance microwave absorption.