Abstract:Although Fe 3 O 4 particles have exhibited excellent microwave absorbing capacity and widely used in practical application due to the synergistic effect of magnetic loss and dielectric loss, their applications are still limited for the required high mass fraction in absorbers. To overcome this problem, the development of Fe 3 O 4 materials with low dimensional structures is necessary. In this study, the shape anisotropic Fe 3 O 4 nanotubes (NTs) with low mass ratios were applied to realize efficient microwave … Show more
“…It's clear that the maximum reflection loss (RL) value of Co/PCNF moves to the low frequency band with a decrease in thickness, where the show in Fig. 9 f. This phenomenon can be mainly explained by the theory of quarter-wavelength, which can be expressed by the following equation 51 , 53 : Figure 9 ( a ) Reflection loss (RL) curves for CoNPs, ( b ) Reflection loss (RL) curves for PCNF, ( c ) S1, ( d ) S2 and ( e ) S3 with different thickness in the frequency range of 2–18 GHz, ( f ) RL values of Co/PCNF at “matching thickness” (tm) in 2.00–18.00 GHz. where c is the velocity of light.…”
Recent studies have found that the core–shell structured metal nanoparticles and porous carbon nanofibers (PCNF) are combined into a microwave absorbing material through electrospinning, which exhibits excellent microwave absorption performance. In this study, the core–shell structure Co nanoparticles prepared by the self-developed HEIBE process (production rate of > 50 g/h) were combined with porous carbon fibers, and their absorbing properties were greatly improved. The morphology of Co/PCNF demonstrated that CoNPs are randomly dispersed in the porous carbon nanofibers and carbon nanofiber form complex conductive network which enhances the dielectric loss of the materials. Meanwhile, the Co/PCNF has a low graphitization and shows a significant improvement in permittivity due to the combination of CoNPs and high conductivity of carbon material. The maximum reflection loss (RL) of Co/PCNF reaches − 63.69 dB at 5.28 GHz with a thickness of 5.21 mm and the absorption bandwidth (RL ≤ − 10.0 dB) is 12.92 GHz. In terms of 5.60 mm and 6.61 mm absorber, there are two absorption peaks of − 47.64 dB and − 48.30 dB appear around 12.50 GHz and 14.10 GHz, respectively. The results presented in this paper may pave a way for promising applications of lightweight and high-efficiency microwave absorbing materials (MAMs).
“…It's clear that the maximum reflection loss (RL) value of Co/PCNF moves to the low frequency band with a decrease in thickness, where the show in Fig. 9 f. This phenomenon can be mainly explained by the theory of quarter-wavelength, which can be expressed by the following equation 51 , 53 : Figure 9 ( a ) Reflection loss (RL) curves for CoNPs, ( b ) Reflection loss (RL) curves for PCNF, ( c ) S1, ( d ) S2 and ( e ) S3 with different thickness in the frequency range of 2–18 GHz, ( f ) RL values of Co/PCNF at “matching thickness” (tm) in 2.00–18.00 GHz. where c is the velocity of light.…”
Recent studies have found that the core–shell structured metal nanoparticles and porous carbon nanofibers (PCNF) are combined into a microwave absorbing material through electrospinning, which exhibits excellent microwave absorption performance. In this study, the core–shell structure Co nanoparticles prepared by the self-developed HEIBE process (production rate of > 50 g/h) were combined with porous carbon fibers, and their absorbing properties were greatly improved. The morphology of Co/PCNF demonstrated that CoNPs are randomly dispersed in the porous carbon nanofibers and carbon nanofiber form complex conductive network which enhances the dielectric loss of the materials. Meanwhile, the Co/PCNF has a low graphitization and shows a significant improvement in permittivity due to the combination of CoNPs and high conductivity of carbon material. The maximum reflection loss (RL) of Co/PCNF reaches − 63.69 dB at 5.28 GHz with a thickness of 5.21 mm and the absorption bandwidth (RL ≤ − 10.0 dB) is 12.92 GHz. In terms of 5.60 mm and 6.61 mm absorber, there are two absorption peaks of − 47.64 dB and − 48.30 dB appear around 12.50 GHz and 14.10 GHz, respectively. The results presented in this paper may pave a way for promising applications of lightweight and high-efficiency microwave absorbing materials (MAMs).
“…9 Traditional ferrite materials possess exclusive features of strong saturation magnetization, high complex permeability as well as being of low cost, which have been extensively applied in the eld of microwave absorption. 10,11 Ferrosoferric oxide (Fe 3 O 4 ) as the simplest ferromagnetic substance has been widely used in dye degradation, 12 biomedical applications, 13 hydrogen storage, 14 energy storage devices, 15 electromagnetic absorbers, 16 etc. Especially in the domain of microwave absorption, natural resonance and eddy-current effect reveal unexceptionable magnetic loss in the high-frequency range.…”
A hollow-structured flower-like Fe3O4@MoS2 composite was synthesized. The minimum reflection loss value reached −49.6 dB at 13.2 GHz with a thickness of 2.0 mm and the effective absorbing bandwidth was 4.24 GHz (11.68–15.92 GHz).
“…reported that compared with Fe 3 O 4 particles, Fe 3 O 4 nanotubes have significant multiple resonances with stronger coercivity, which are beneficial to microwave absorption. [ 8 ] Yang and co‐works found that iron nanowires have higher permeability and better EMW absorption performance than iron nanoparticles. [ 9 ] However, to achieve excellent EMW absorption performance, the loading of 1D magnetic metal materials in matrix is usually higher than 30 wt%, which is not conducive to the lightweight development of EMW absorbing materials.…”
Soft magnetic micro/nanostructures are highly desirable for pursuing excellent magnetic properties and electromagnetic wave (EMW) absorption performance. However, their magnetic loss at high frequency is usually very low due to the sharp drop of permeability, and thus results in a heavy loading in matrix and a large layer thickness, which are not conductive to the development of ultralight and ultrathin EMW absorbers. Here, an ultralight and ultrathin EMW absorber based on a parallel Ni wire array are reported, and an orientation‐enhanced strategy to improve EMW absorption performance is proposed. Combining with the finite element simulation, it is found that the parallel orientation of Ni wires with a capacitor‐like structure enhances the interfacial polarization, thereby improving dielectric loss. The strong shape anisotropy caused by orientation increases magnetic loss by enhancing magnetic resonances, which further improves impedance matching. The parallel Ni wire array exhibits excellent EMW absorption and achieves the largest specific reflection loss (reflection loss/(thickness × loading)) among magnetic wire‐based absorbers.
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