Carbonaceous composites with tailored porous architectures and magnetic Fe 3 O 4 components derived from walnut shells were fabricated by a solvothermal method and used as effective microwave absorbers. The porous composites were obtained by two carbonization processes at different temperatures and an etching process using potassium hydroxide. The introduction of a developed porous architecture inside the resulting materials distinctly improved the microwave absorption performance. Moreover, investigations revealed that the Fe 3 O 4 nanoparticles were chemically bonded and uniformly decorated on the porous framework without aggregation. Owing to the combined advantages of the lightweight conductive biochar-like porous framework with a favorable dielectric loss and Fe 3 O 4 nanoparticles with magnetic loss features, these newly fabricated porous carbonaceous composites exhibited excellent microwave absorption performance. A reflection loss (RL) of À51.6 dB was achieved at a frequency of 13.6 GHz. Besides, the effective absorption (below À10 dB) bandwidth reached 5.8 GHz (from 11.9 to 17.7 GHz) at an absorber thickness of only 2 mm. These results indicated that this type of porous Fe 3 O 4 -biochar composite derived from biomass substances and prepared via an easy-to-handle process can be considered as attractive candidates for the design and manufacture of high-efficiency microwave-absorbing materials.
Microwave
absorption materials with great reflection loss and wide
absorption band that can provide electromagnetic waves (EMWs) absorption
with minimal thickness are highly desirable, particularly when they
could be controllably fabricated through a facile process. Herein,
N-doped three-dimensional (3D) carbonaceous composites with highly
dispersed nickel nanoparticles (N-SA/Ni-X, X = 3%, 6%, 9%) were successfully
prepared by a facile one-step encapsulation process and carbonization.
The performance of the absorber has a significant enhancement due
to the introduction of nitrogen elements into a carbon network for
controlling the dispersion and size distribution of Ni nanoparticles.
When a 6% Ni2+ mass percentage was used, the maximum reflection
loss (RL) could reach −42.2 dB at 9.8 GHz. Moreover, the effective
absorption (below −10 dB) bandwidth can be increased by 2.3
GHz, from 8.5 to 10.8 GHz, with the absorber thickness of only 2 mm,
and it can be tuned from 2.8 to 14.4 GHz by adjusting the thickness
from 1.5 to 5 mm. The excellent electromagnetic-wave-absorbing performance
could be assigned to the combinatorial advantages of the lightweight
conductive porous network with favorable dielectric loss and magnetic
loss features induced by highly dispersed Ni nanoparticles. These
newly fabricated N-SA/Ni-X composites could be regarded as promising
candidates for lightweight and high-performance microwave absorption
materials.
Hetero-structured functional materials with tailored composition that can provide excellent electromagnetic wave (EMW) absorption with minimal thickness are highly desirable, especially if they can be easily fabricated. Herein, novel hetero-structured CoNi-CuO composite microspheres were fabricated via a facile solvothermal process. The composites with adjusted mass ratios of CuO to CoNi alloy (5/1, 2.5/1 and 1.25/1) were facilely achieved by modulating the quantity of CuCl 2 $2H 2 O during the synthesis. It was demonstrated that the enhanced microwave absorption properties could be ascribed to the dielectric CuO, which can favorably increase the interface of the hetero-structure and the impedance matching with CoNi alloyed particles. It was shown that, when the molar ratio was 2.5 : 1, the typical CoNi-CuO composite microspheres presented a promising microwave absorption performance, namely a maximum reflection loss (RL) of À25.1 dB at 13.2 GHz with a thickness of only 2.5 mm, while the effective microwave absorption bandwidth (RL < À10) could reach 3.4 GHz (from 10.0 to 13.4 GHz). As is demonstrated, this kind of newly fabricated CoNi-CuO composite can be regarded as a promising candidate for high-performance microwave absorption materials.
Hollow dopamine-derived cavities/Fe3O4 nanoparticles-encapsulated carbonaceous composites with self-generating 3D network structure were fabricated for potential application as excellent microwave absorbers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.