RESUMEN
Advanced microwave absorption (MA) materials have attracted widespread attention to meet the challenges of electromagnetic (EM) pollution. Herein, MgFe2O4/MgO/C fibers were successfully prepared via electrospinning technology and carbonization, and their surfaces were coated by MoS2 via hydrothermal method. The EM wave absorption performance of composites was enhanced due to the introduction of MoS2. The results showed that the EM wave absorption performance of MgFe2O4/MgO/C could not meet the requirements due to low dielectric loss and poor impedance matching. The performance of the composites was improved after coating of MoS2, which showed the strong wave absorption capability and the broad absorption bandwidth. The optimal reflection loss (RL) is -56.94 dB at 9.5 GHz and the effective absorption bandwidth is 3.9 GHz (8.08-11.98 GHz) with a thickness of 2.7 mm. The excellent MA performance can be mainly attributed to excellent synergistic effect between MgFe2O4/MgO/C and MoS2. Furthermore, MoS2 also contributes to dielectric loss and ideal impedance matching. MgFe2O4/MgO/C@MoS2 composites may be utilized for lightweight and high-efficient MA materials.
RESUMEN
The conductive networks for electron hopping and migration constructed by one-dimensional (1D) composite absorbers are highly desirable to improve the electromagnetic (EM) wave attenuation capacity. Herein, the Ni@Co/C@polypyrrole (PPy) composites integrating the advantages of component and microstructure were fabricated. The addition of Co/C and PPy effectively optimized the impedance matching and improved the EM attenuation. Under the comprehensive impacts of multiple reflections/scattering, conduction loss and interface polarization, the Ni@Co/C@PPy composites showed superior EM wave absorption with the reflection loss (RL) value of -48.76 dB and the effective absorption bandwidth (EAB) of 5.10 GHz at a corresponding thickness of 2.0 mm. The largest EAB could reach 5.54 GHz (7.24-12.78 GHz) at the thickness of 2.2 mm. This work provides a great reference for fabricating 1D novel EM wave absorption materials.
RESUMEN
New types of electromagnetic (EM) wave absorption materials with a light weight, strong absorption ability and wide absorption frequency have been widely explored. Nevertheless, it is still an intractable challenge to design the structure of the materials and rationalize multiple components. In this work, one-dimensional (1D) CoFe2/C@MoS2 composites were prepared via electrospinning technology, high-temperature carbonization and hydrothermal method. SEM and TEM images reveal that the as-prepared CoFe2/C fibers with a 1D structure are well coated with MoS2. The excellent absorption performance of the composites is mainly attributed to the 1D structure and the ideal impedance matching. CoFe2/C@MoS2 composites show strong absorption ability with an optimal reflection loss (RL) of -66.8 dB (13.28 GHz) at a matching thickness of 2.12 mm. Meanwhile, the composite possesses an effective absorption frequency range between 10.70 and 16.02 GHz with a bandwidth of 5.32 GHz. These results indicate that CoFe2/C@MoS2 composites will become promising lightweight and highly efficient MA materials.
RESUMEN
Nowadays, ferrites/carbon fibers have attracted considerable attention as microwave absorption materials (MA) due to the synergistic effect between dielectric and magnetic loss. Herein, the ZnFe2O4/C fibers were fabricated via electrospinning and calcination methods, and then polypyrrole (PPy) successfully coated on the fibers via oxidative polymerization. The ZnFe2O4/C@PPy composites exhibit enhanced EM wave absorption performance with the loading of 25 wt%. The optimal reflection loss (RL) value is up to -66.34 dB (13.80 GHz) and effective absorption bandwidth (EAB) is 5.74 GHz (11.78-17.52 GHz) with a matching thickness of 1.93 mm. Besides, high-efficient absorption performance of the ZnFe2O4/C@PPy composites is mainly attributed to the dielectric loss and ideal impedance matching. This study reveals a novel approach to development of ferrites/carbon fibers coated with PPy, and the ZnFe2O4/C@PPy composites exhibit great potential application as the materials with high-efficient absorption properties.
RESUMEN
Herein, coralloid core-shell structure NiS/Ni3S4@PPy@MoS2 nanowires were elaborately designed and successfully synthesized through a three-step route to obtain exceptional microwave absorption (MA) properties. Ni nanowires were first fabricated, and then used as the substrate to be coated with a layer of PPy. Ni chalcogenides were obtained by using Ni nanowire as sacrificial templates while growing MoS2 nanorods by hydrothermal method. Both the one-dimensional (1D) core-shell structure and the coralloid surface generated by MoS2 nanorods were beneficial for the attenuation of microwaves. After investigating the electromagnetic properties of different loading content absorbers (30 wt.%, 40 wt.% and 50 wt.%), it is found that the 50 wt.% loading absorber has the optimal MA performance. The minimum reflection loss (RLmin) value can reach -51.29 dB at 10.1 GHz with a thickness of 2.29 mm, and the corresponding effective absorption bandwidth (EAB, RL < -10 dB) can be up to 3.24 GHz. This research provides a reference for exploiting novel high-efficient 1D absorbers in the field of MA.
RESUMEN
Metal-organic framework (MOF) materials have caused widespread concerns in the field of microwave absorption, due to the unique microstructure and electronic state. Herein, the CoZn/C@MoS2@polypyrrole (PPy) composites were prepared through MOF self-template method. The MoS2 sheets and PPy shell incorporated for optimizing impedance matching of two-dimensional (2D) CoZn/C composites. The introduction of MoS2 sheets and PPy shell endowed the composites with enhanced microwave absorption. The as-prepared CoZn/C@MoS2@PPy composites showed a minimum reflection loss (RL) of -49.18 dB with the thickness of 1.5 mm. In addition, the effective absorption bandwidth (EAB, RL values exceeding -10 dB) covered 4.56 GHz, which showed greater performances than CoZn/C composites under a lower thickness (<2 mm). This work not only provides a facile route for fabricating MOF-derived carbon-based composites as microwave absorbers, but also broadens the application of MOF materials.
RESUMEN
In this work, one-dimensional (1D) ZnFe2O4@carbon@MoS2/FeS2 composites were synthesized by hydrothermal method, magnetic-field-induced distillation-precipitation polymerization and high-temperature carbonization. The structure, morphology, composition, magnetic performance and electromagnetic (EM) wave absorbing properties of the composites were systematically studied. The composites show strong microwave absorption (MA) capacity with a minimum reflection loss (RLmin) value of -52.5 dB at 13.2 GHz, and have an effective absorption frequency range of 10.10-15.08 GHz with a bandwidth of 4.98 GHz when the thickness is 2.23 mm. It is expected that as-synthesized 1D ZnFe2O4@carbon@MoS2/FeS2 composites can be a promising EM wave absorption material.
RESUMEN
Microwave absorbing materials (MAM) have attracted considerable attention over the years in stealth and information technologies. Metal-organic framework (MOF) with a unique microstructure and electronic state has become an attractive focus as self-sacrificing precursors of microwave absorbers. The MOF-derived porous carbon (PC) materials exhibit a high absorbing performance due to the stable three-dimensional structure and homogeneous distribution of metal particles. MOF-derived PC materials are promising for ideal MAM via tuning of the structure and composition, resulting in appropriate impedance matching and the synergistic effect between magnetic and dielectric loss. In this review, the MOF-derived PC materials and their basic absorption mechanisms (dielectric loss, magnetic loss and impedance matching) are introduced, as well as the characters of various MOF-derived PC materials. In addition, this review provides a comprehensive introduction and tabulates the recent progress based on the classification of the MOF-derived metallic state, such as pure PC (without reduced metals), mono-metal/PC, multi-metal/PC, metal oxides/PC and other derived PC composites. Finally, the challenges faced by MOF-derived PC materials are overviewed, and their further development is mentioned.
RESUMEN
One-dimensional (1D) ZnFe2O4@SiO2 (ZS) nanochains were prepared with Stöber method under external magnetic field. Then, 1D ZS nanochains were covered with a uniform polydopamine (PDA) shell, and the pyrolysis process was completed to obtain 1D ZnFe2O4@SiO2@C (ZSC) nanochains. Finally, 1D flower-like ZnFe2O4@SiO2@C@NiCo2O4 (ZSCNC) nanochains were fabricated through a simple hydrothermal method. The carbon layer with strong dielectric loss enabled the 1D ZSC nanochains to achieve an ultra-wide effective absorption bandwidth (EAB) of 6.22 GHz. Compared with the above nanochains, the 1D ZSCNC nanochains showed more excellent microwave absorption (MA) properties because of the unique 1D flower-like architectures having large surfaces and multiple interfaces. The sample loaded with 30 wt% 1D flower-like ZSCNC nanochains showed strong MA performances with a minimum reflection loss (RL) value of -54.29 dB (11.14 GHz) and an EAB of 5.66 GHz (11.94-17.60 GHz) at the thickness of 2.39 mm. The 1D flower-like ZSCNC nanochains with strong absorption, broad absorption bandwidth (almost the entire Ku band) and thin layer has a good application prospect for the absorption of electromagnetic waves in Ku band.
