Abstract:Ordered
mesoporous carbon (OMC) is considered to be a prospective carbon-based
material for microwave absorption because of its abundant well-ordered
mesoporous structures, high specific surface area, numerous active
sites, and facile preparation process. However, its development has
been seriously hindered by its poor impedance-matching characteristic.
Herein, silica-modified OMC composites with a designable impedance-matching
transition layer are successfully fabricated via a self-assembly method
and succeed… Show more
“…With reference to the ε″ (Figure g), the conspicuously increased tendency is attributed to the high electrical conductivity and interconnected network of WPU/MXene/NiFe 2 O 4 , which is instrumental in the emerging migrating and hopping of electrons. The weak resonance peaks at ∼10 and 11.5 GHz may be associated with the loss of incident electromagnetic waves through dipolar polarization and interfacial polarization. − Additionally, the hybrid aerogel after introducing NiFe 2 O 4 NPs exhibits a slightly decreasing ε′ and ε″, which balance the impedance characteristics (Figure S8) and are consistent with our previous report …”
Flexible, ultralight, and mechanically robust electromagnetic interference (EMI) shielding materials are urgently demanded to manage the increasing electromagnetic radiation pollution, but it remains a great challenge to simultaneously achieve ultralight yet mechanically robust properties while retaining high-efficiency EMI shielding performance. Herein, we fabricate a novel waterborne polyurethane/Ti 3 C 2 T x MXene/nickel ferrite (WPU/MXene/NiFe 2 O 4 ) hybrid aerogel by constructing a strong chemical bonding interaction between an NCOterminated WPU prepolymer and hydroxyl functionalized MXene nanosheets. The resultant aerogels exhibit remarkable lightweight and mechanical properties, particularly high compressive stress far exceeding that of other MXene-based and WPU-based porous materials. Furthermore, synergistic effects of the oriented porous architecture and the multiphase skeleton endow the hybrid aerogels with a high Xband EMI shielding effectiveness (SE) of 64.7 dB at a low density of ∼38.2 mg/cm 3 . The corresponding specific SE value achieves 1694−3124 dB•cm 3 /g, and the SSE/d is up to 15,620 dB•cm 2 /g, surpassing that of most reported EMI shielding materials. Importantly, this aerogel, with excellent electromagnetic radiation protection effects and shielding reliability, is highly promising for long-term and effective EMI shielding service in various application environments.
“…With reference to the ε″ (Figure g), the conspicuously increased tendency is attributed to the high electrical conductivity and interconnected network of WPU/MXene/NiFe 2 O 4 , which is instrumental in the emerging migrating and hopping of electrons. The weak resonance peaks at ∼10 and 11.5 GHz may be associated with the loss of incident electromagnetic waves through dipolar polarization and interfacial polarization. − Additionally, the hybrid aerogel after introducing NiFe 2 O 4 NPs exhibits a slightly decreasing ε′ and ε″, which balance the impedance characteristics (Figure S8) and are consistent with our previous report …”
Flexible, ultralight, and mechanically robust electromagnetic interference (EMI) shielding materials are urgently demanded to manage the increasing electromagnetic radiation pollution, but it remains a great challenge to simultaneously achieve ultralight yet mechanically robust properties while retaining high-efficiency EMI shielding performance. Herein, we fabricate a novel waterborne polyurethane/Ti 3 C 2 T x MXene/nickel ferrite (WPU/MXene/NiFe 2 O 4 ) hybrid aerogel by constructing a strong chemical bonding interaction between an NCOterminated WPU prepolymer and hydroxyl functionalized MXene nanosheets. The resultant aerogels exhibit remarkable lightweight and mechanical properties, particularly high compressive stress far exceeding that of other MXene-based and WPU-based porous materials. Furthermore, synergistic effects of the oriented porous architecture and the multiphase skeleton endow the hybrid aerogels with a high Xband EMI shielding effectiveness (SE) of 64.7 dB at a low density of ∼38.2 mg/cm 3 . The corresponding specific SE value achieves 1694−3124 dB•cm 3 /g, and the SSE/d is up to 15,620 dB•cm 2 /g, surpassing that of most reported EMI shielding materials. Importantly, this aerogel, with excellent electromagnetic radiation protection effects and shielding reliability, is highly promising for long-term and effective EMI shielding service in various application environments.
“…According to Marksworth’s electromagnetic (EM) field theory, the MA capability of materials relies on their microstructures and two other parameters: relative permittivity (ε r = ε′ – j ε″) and permeability (μ r = μ′ – j μ″), where the real parts (ε′ and μ′) correspond to the electric and magnetic energy storage capabilities, whereas the imaginary parts (ε″ and μ″) represent the loss of electric and magnetic energy, respectively . The complex permittivity of Ln 2 O 3 /MnO/C composites measured at 2–18 GHz is shown in Figure a,b.…”
Metal–organic frameworks (MOFs)
have been verified as ideal
precursors for preparing highly effective microwave absorbers. However,
it is still challenging to fabricate a thin, lightweight, and well-organized
nanostructure with strong microwave absorption (MA) capability and
wide absorption bandwidth. In this study, hollow cube dual-semiconductor
Ln2O3/MnO/C (Ln = Nd, Gd, Er) nanocomposites,
which are effective microwave absorbers, have been fabricated via
one-step high-temperature carbonization of Ln-Mn-MOFs. The effect
of band gap on the MA performance of various nanocomposites synthesized
at the same carbonization temperature is investigated. Gd2O3/MnO/C-800 shows superior MA capacity with maximum reflection
loss (RLmax) of −64.4 dB at 12.8 GHz and 1.86 mm-thickness.
When the thickness is 1.44 mm, the RL value is obtained as −52.7
dB at 16.8 GHz, and at a low frequency of 4.36 GHz and thickness of
4.59 mm, the RL value reaches −56.4 dB. Further, the effect
of temperature on the MA properties of Gd2O3/MnO/C is examined. The results reveal that Gd2O3/MnO/C-700 has an ultrahigh MA bandwidth of 6.6 GHz, covering the
entire Ku bands at 2.09 mm-thickness. Overall, this work demonstrates
a facile strategy to construct hollow, homogeneous ternary composites
with outstanding MA performance.
“…For CNA900, average value of tan δ ε (0.45) is about twice as high as average value of tan δ μ (0.21), so it is not hard to conclude that dielectric loss plays a decisive role in enhancing microwave dissipation performance. For the purpose of further understanding the microwave attenuation performance of the as-made samples, attenuation constants α can be gained by the following formula 38 , 39 : Figure 5 Cole–Cole curves of ( a ) CNA800, ( b ) CNA900 and ( c ) CNA1000. ( d ) Dielectric loss tangent of the as-synthesized samples.…”
Effectively broadening microwave absorbing frequency of pure magnetic substances remains a huge challenge. Herein, micro-perspective structures can be controlled through a calcination route. Satisfactorily, the composites prepared at the calcination temperature of 900 °C exhibit excellent microwave attenuation performance with a broad working frequency and appropriate paraffin filling ratio. Remarkably, the composites can reach an extremely high reflection loss (RL) value of − 49.79 dB, and the extended effective working frequency range (RL < − 10 dB) of 6.84 GHz can also be obtained. Superb magnetic loss, admirable dielectric loss, sufficient dipole polarization, as well as superior impedance matching should be band together for obtaining ideal microwave absorbers. The CoNi hydroxides derived bimatallic alloy composites were fabricated via a cost-effective and facile synthesis process, and this work aroused inspirations of designing high-performance microwave absorbers for mataining the sustainable development.
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