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Electromagnetic-wave (EMW) absorption by Ni/C nanocapsules with similar permeability but different permittivity mainly due to differences in the graphite-shell thickness has been investigated. The optimal working frequency could appear at S-band and C-band and considerable strong EMW absorption was achieved. For the optimal Ni/C nanocapsules, a reflection loss exceeding -20 dB was reached from 2.6 to 8.2 GHz with a maximum value of -40 dB at 3 GHz. The improved absorption can be attributed to an optimal electromagnetic match and an enhanced dipole polarization upon increasing of shell thickness. [ABSTRACT FROM AUTHOR]

The intense requirement for bifunctional electromagnetic wave (EMW) absorbing materials is becoming the urgent focus and upgraded exploration for advanced application of absorbing EMW device in complex and extreme environments. Based on high dielectric loss capacity and superior chemistry inertness of graphite nanosheets, a two-dimensional (2D) graphite nanosheet decorated with graphite encapsulating soft-magnetic Ni 3 Fe nanocapsules was designed and exploited by introducing novel nitrogen catalyst in one-pot non-balance evaporating strategy. Through modulating the impedance matching and further optimal mass ratio, a minimum reflection loss (RL) of −35.8 dB at 7.35 GHz with an absorber thickness of 3.5 mm and a wide effective absorption bandwidth (EAB) of 5.5 GHz (RL ≤ −10 dB), which almost covered whole Ku-band, were realized with an absorber thickness of 2 mm. Combining the prominent EMW absorption, this 2D nanocomposite showed excellent comprehensive anti-corrosion ability to maintain the original microstructure in acidic, neutral and alkaline salty corrosion conditions. The successful exploration of 2D anticorrosive EMW absorber provides a significant insight for rational fabrication of futural bifunctional EMW absorbing devices in complex circumstances. [Display omitted] • Novel 2D graphite nanosheets decorated with Ni 3 Fe@C nanocapsules was synthesized with nonequilibrium strategy. • Outstanding anti-corrosion ability in acidic, neutral and alkaline circumstances simultaneously. • Effective absorption bandwidth 5.5 GHz with a thickness of 2 mm was achieved. • Systematically optimal strategy combined physical image and anti-corrosion mechanisms have been deeply discussed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new type of Fe 3 Si/C nanocapsules were designed and synthesized. • The desirable impedance match between amorphous carbon shell and Fe 3 Si can be achieved. • An optimal RL value and broadband absorption with RL lower than −10 dB have been achieved. Abstract Nanoscale heterostructures, like core-shell structures, show attractive microwave-absorption characteristics because of the synergetic effects of their dielectric shells and soft-magnetic cores. A new type of nanocapsules with amorphous C shell encapsulating Heusler soft-magnetic Fe 3 Si alloy has been designed and synthesized in which Si atoms were doped in the C shell to effectively produce a large amount of Si-C bonds to induce the formation of an amorphous C shell. This further significantly improves the dielectric properties of C shells by enhanced dielectric polarization. These tailored Fe 3 Si/C nanocapsules, exhibit enhanced microwave-absorption properties because of the desirable impedance match between the amorphous C shell and the soft-magnetic Fe 3 Si. The optimal Fe 3 Si/C nanocapsules exhibit a highest absorption intensity of −68.3 dB at 13 GHz and an absorption bandwidth of 4.6 GHz (for RL lower than −10 dB) for absorber thicknesses of 2.1 mm and 1.4 mm, respectively. This new type of nanocapsules is of potential interest for application as novel microwave-absorption material. [ABSTRACT FROM AUTHOR]