Strong electric wave response derived from the hybrid of lotus roots-like composites with tunable permittivity

Abstract

Lotus roots-like NiO/NiCo2O4 hybrids derived from Metal-organic frameworks (MOFs) are fabricated for the first time by using flake NiCo-MOF precursors as reactant templates. It was found that a thin sample consisting of 60 wt % NiO/NiCo2O4 hybrids in the wax matrix exhibited an effective microwave absorption bandwidth of 4.2 GHz at the thickness of 1.6 mm. The highest reflection loss of −47 dB was observed at 13.4 GHz for a sample with a thickness of 1.7 mm. Results obtained in this study indicate that hybrids of NiO and NiCo2O4 are promising microwave absorbing materials with adjustable permittivity, which can exhibit broad effective absorption bandwidth at low filler loading and thin thickness.

Tunable Dielectric Performance Derived from the Metal–Organic Framework/Reduced Graphene Oxide Hybrid with Broadband Absorption

“…If the thickness of absorber ( t m ) at peak frequency ( f m ) meets the formula where c represents the velocity of light in the free space, and |μ r | and |ε r | are the moduli of μ r and ε r . To demonstrate the maximum RL value appearing at 2.4 mm, as shown in Figure , we conduct the simulations of absorber t m at the minimum RL values versus peak frequency ( f m ) for S2 under λ/4 conditions . The black curve is on behalf of the simulation thickness ( t fit m ) at 2–18 GHz via violet dots, and quarter wavelength principles are the experimental matching thickness ( t exp m ) at f m .…”

“…To demonstrate the maximum RL value appearing at 2.4 mm, as shown in Figure 12, we conduct the simulations of absorber t m at the minimum RL values versus peak frequency (f m ) for S2 under λ/4 conditions. 41 The black curve is on behalf of the simulation thickness (t fit m ) at 2−18 GHz via violet dots, and quarter wavelength principles are the experimental matching thickness (t exp m ) at f m . We found that the value of t exp m at 2.4 mm fits well with the simulation t fit m , whereas the t exp m deviates from t fit m to variable extents.…”

Novel Three-Dimensional SiC/Melamine-Derived Carbon Foam-Reinforced SiO2 Aerogel Composite with Low Dielectric Loss and High Impedance Matching Ratio

“…The values of both ε′ and ε′′ of MDCF dropped sharply with increasing frequency, while those of SiC/MDCF and SiC/MDCF–Aerogel remained roughly balanced with the fluctuation phenomenon at high frequency in Figure a and b. On the basis of the Debye theory, ε′ and ε′′ were calculated as eqs and where ω is the angular frequency, τ is the polarization relaxation time, and σ ac is the alternative conductivity. ε ∞ is the high-frequency limit relative dielectric permittivity, ε s is the static permittivity, and ε 0 is the dielectric constant in vacuum.…”

“…By combining the profiling data of the MDCF–wax composite, we find that as to the SiC/MDCF–Aerogel–wax composite, the impedance matching ratio played a crucial role in achieving the lowest reflection loss value. When the impedance matching ratio reached a particular value, the attenuation loss began to have an impact. , …”

Fabrication of NiO/NiCo2O4 Mixtures as Excellent Microwave Absorbers

“…Their results demonstrated that the sample exhibited a maximum RL value of − 28.6 dB at 14.96 GHz. Porous NiO/NiCo 2 O 4 lotus root-like nanoflakes were demonstrated by Liang and co-workers as a promising candidate for a microwave absorbent [29]. The NiO/NiCo 2 O 4 (60 wt%)-wax hybrid showed the strongest EMW absorption with the RL value of − 47 dB at 13.4 GHz.…”