Possessing both dielectric
loss and magnetic loss is desirable
for high-efficiency microwave absorbers to achieve promising impedance
matching and high attenuation constant. In this work, biomass-derived
carbon (BDC)/NiCo2S4 (BNCS) composites were
successfully synthesized through growing flower-like NiCo2S4 microspheres on the surface of a three-dimensional
(3D) BDC framework using a low-cost, facile, and sustainable process.
The results indicated that the precursor dosage had a significant
impact on the microstructures, surface morphologies, and electromagnetic
parameters of the materials, and the introduction of NiCo2S4 nanosheets obviously enhanced impedance matching and
attenuation constant, leading to a strong absorption performance.
The minimum reflection loss (RLmin) of BNCS reached −62.74
dB at 2.24 mm and an effective bandwidth of 7.62 GHz at 1.96 mm was
achieved, which was much better than that of BDC (−8.41 dB
at 2.97 mm). It was apparent that BNCS could serve as a promising
candidate for next-generation high-performance microwave absorbers
with strong absorption, wide bandwidth, and thin thickness.
Absorbers
with light weight, low filler loading, high absorption
capacity, and broad absorption bandwidth are highly desirable for
electromagnetic (EM) wave absorption application, and extensive efforts
in designing excellent performance biomass-derived microwave absorbents
using sustainable and renewable materials have been made. Here, for
the first time we constructed flexible and high-performance EM-absorbing
materials of porous biomass-derived carbon (PBDC) decorated with in-situ
grown MnO nanorods (MnOnrs) by a simple process. The chemical composition
and microstructural feature of these MnOnrs/PBDC composites are highly
dependent on the content of MnOnrs controlled through the concentration
of potassium permanganate, and thus their EM properties could be also
manipulated. Compared with the pure PBDC, the MnOnrs/PBDC composites
exhibited excellent EM wave absorption performance with the minimum
reflection loss (RLmin) of −51.6 dB at 10.4 GHz
with a thickness of 2.47 mm and a qualified bandwidth of 14.2 GHz
with an integrated thickness from 1.00 to 5.00 mm. Notably, the microwave
absorption capacity of this new kind of composite is not so susceptible
to the content of MnOnrs as those common carbon-based absorbers, which
could be attributed to the synergistic effect between PBDC and MnOnrs
as well as the hierarchical structure. This work may provide a new
guideline for development of biomass as a low-cost, green, and renewable
high-performance, carbon-based absorber.
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