Search

The two-component composites with porous carbon and magnetic metals exhibit a promising application prospect in microwave absorption due to their superior impedance matching and excellent loss ability. Herein, a novel process combined sol-gel and in-situ pyrolysis methods was proposed to prepare a series of porous carbon@Fe 20 Ni 80 composites. The structure and composition of composites were controlled by adjusting pyrolysis temperature and doping amount of Fe 20 Ni 80 for achieving an improvement on microwave absorption performance. Under the optimal Fe 20 Ni 80 doping amount of 2 mmol, the composite pyrolyzed at 800 °C shows the highest performance. With 15 wt% filler loading, the composite achieves the minimum reflection loss value (RL min) of −39.5 dB at 6.7 GHz with a thickness of 3 mm. Moreover, under the optimal matching thickness of 2.2 mm, the maximum effective absorption bandwidth (EAB max) reaches 5.4 GHz (8.0–13.4 GHz), covering the whole X-band. The porous structure is maintained at appropriate pyrolysis temperature, which optimizes the impedance matching of materials. The porous carbon matrix with partial graphitization exhibits the dielectric loss ability to electromagnetic waves. In addition, the introduction of Fe 20 Ni 80 endows the composite with magnetic loss ability. This study develops an avenue for the preparation of two-component composites with porous carbon and magnetic metals and has potential application in microwave absorption. [Display omitted] • A novel method was proposed to prepare porous carbon@Fe 20 Ni 80 composites. • Wheat flour was used as raw material in this work. • The structure of composites was controlled by adjusting pyrolysis temperature. • The composition was controlled by adjusting the amount of metal salt. [ABSTRACT FROM AUTHOR]

The electromagnetic wave absorbers widely applied to various harsh scenes, especially with anti-corrosion properties have been reported and the focus was at the anti-inorganic corrosion. However, the organic corrosion, such as microbiologically influenced corrosion is also serious and needs to be overcome. Herein, based on the excellent electromagnetic synergy effect, a series of cobalt-based metal-organic framework-derived composites with hollow bowl-shape were synthesized. By modulating the balance between the dielectric and magnetic loss, the minimum reflection loss of − 52.66 dB with matching thickness of 2.7 mm and an ultra-wide effective absorption bandwidth of 6.8 GHz, which covered the whole Ku band, with a thickness of 2.4 mm, were achieved. In addition, the radar cross section values of the composites were simulated and the results verify the excellent absorption performances of the absorbers. Combining the prominent absorption performance, the derived composites exhibited exceptional anti-microbiologically influenced corrosion properties reflected by the electrochemical impedance modulus at 0.01 Hz substantially increasing more than 3 times. Until now, no similar bifunctional materials have been reported, so it is of great significance and emergence to fill this gap, we hope our work can provide a theoretical basis for the following related experimental research. [Display omitted] • A novel self-assembled hollow bowl-shaped metal-organic framework-derived electromagnetic wave absorber was obtained. • Effective absorption bandwidth 6.8 GHz with a thickness of 2.4 mm was achieved. • The excellent absorbing performance is mainly attributed to the synergetic effect of dielectric loss and magnetic loss. • Combining absorption performance, the composites exhibited anti-microbiologically influenced corrosion properties. [ABSTRACT FROM AUTHOR]

• A novel Co-MOF derivative with a high saturation magnetization was obtained via solvothermal and pyrolysis. • Effective absorption bandwidth 6.9 GHz with a thickness of 2.5 mm was achieved. • The excellent absorbing performance is mainly attributed to the perfect synergetic effect of dielectric loss and magnetic loss. [Display omitted] Metal-organic framework (MOF) derived composite is one of the most promising lightweight electromagnetic wave (EMW) absorbers. However, it is still a significant challenge to raise its effective absorbing bandwidth (EAB) for enhancing the EMW absorbing performance. Herein, a novel Co/C composite derived from Co-MOF with a large saturation magnetization was fabricated via a solvothermal reaction and a subsequent annealing process. The resultant Co/C composite shows prominent EMW absorbing performance. The EAB of the Co/C composite obtained at 700 °C reaches an ultra-wide bandwidth of 6.9 GHz at 2.5 mm which is much higher than that of most other MOF-derived composites. The excellent EMW absorbing performance is mainly attributed to the perfect impedance matching, caused by the synergetic effect of dielectric loss and magnetic loss. Hence, this work provides a simple method for the synthesis of MOF-derived Co/C composites with prominent EMW absorbing ability. [ABSTRACT FROM AUTHOR]

• The Fe 3 O 4 @C nanocomposite with a foam-like core-shell structure was first prepared. • The foam-like structure was obtained by solution combustion method. • The efficient EMW absorption (RL ≤ −20 dB) band can reach 14.9 GHz (d = 1.4–5.5 mm). Ferrite and carbon nanocomposites are regarded to be excellent electromagnetic wave absorbers due to their compatible dielectric and magnetic loss capabilities. In this article, the three-dimensional (3D) Fe 3 O 4 @C core-shell nanocomposites with foam-like structure have been successfully prepared, which would greatly promote multiple reflection/scattering of the incident microwave. By adjusting the amount of polymeric precursors, the outer carbon can be perfectly controlled within the average thickness range of 9.1–34.8 nm. Meanwhile, through the synergy between 3D foam-like Fe 3 O 4 core and outer carbon, the impedance matching conditions of the nanocomposites can be improved. Besides, the electromagnetic wave absorptivity of the nanocomposites presents a significant dependence on the thickness of outer carbon. When the average thickness of outer carbon is 28.3 nm, the absorber shows the most excellent performance, and the minimum reflection loss (RL) value is −55.5 dB with 2.5 mm absorber thickness. Especially, when the thickness is tuned from 1.4 mm to 5.5 mm, the Fe 3 O 4 @C exhibits efficient absorption (RL ≤ −20 dB) in an ultra-wide band (14.9 GHz). Based on the amazing microwave absorption properties, this nanocomposite can be considered as an ideal absorber. [ABSTRACT FROM AUTHOR]