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Absorption (electromagnetic radiation)

About: Absorption (electromagnetic radiation) is a research topic. Over the lifetime, 76674 publications have been published within this topic receiving 1381221 citations.


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Journal ArticleDOI
TL;DR: In this paper, the effect of porous structure on microwave absorption property of the carbon/Co nanocomposite was also discussed and the maximum reflection loss of the porous C(Co) nanocompositionite can reach 40dB at 4.2GHz with 5mm in thickness and the primary microwave absorptive mechanism is ascribed to the dielectric loss.
Abstract: Porous carbon/Co nanocomposites were fabricated by a sol-gel method. The electromagnetic parameters were measured in the 2–18GHz range. Compared with porous carbon composite, porous carbon/Co nanocomposite has larger dielectric loss due to the enhanced interfacial polarization relaxation loss and Ohmic loss. The maximum reflection loss of the porous C(Co) nanocomposite can reach 40dB at 4.2GHz with 5mm in thickness and the primary microwave absorptive mechanism is ascribed to the dielectric loss. The effect of porous structure on microwave absorption property of the carbon/Co nanocomposite was also discussed.

327 citations

Journal ArticleDOI
TL;DR: In this article, the optical effect of the substrate on the anomalous absorption of aggregated silver films is taken into account in terms of the dipole interaction between an island particle and its mirror image in the substrate.

326 citations

Journal ArticleDOI
01 Mar 2021
TL;DR: In this paper, Co/C nanocomposites with Co nanoparticles uniformly distributed in amorphous carbon sheets are prepared by a freezing dry and carbothermic reduction process.
Abstract: Carbon-based composites have gained extensive attention as microwave absorbing materials due to the lighter weight compared with other materials. In this work, Co/C nanocomposites with Co nanoparticles uniformly distributed in amorphous carbon sheets are prepared by a freezing dry and carbothermic reduction process. Hierarchical porous microstructures (micropores, mesopores, macropores) are achieved by ice template and huge amounts of gas during carbothermal reduction. Excellent absorption performance is achieved at a very low Co/C content (10% and 15%), which is a great success to design ultralight absorbers. At 10% content level, the effective absorption bandwidth is 5.0 GHz with a thin thickness of 1.8 mm, while the absorption bandwidth is 4.7 GHz with a thin thickness of 1.5 mm at 15% Co/C content level. The excellent absorption performance is attributed to excellent impedance matching resulting from synergy of cobalt and carbon and strong interfacial polarization induced by the hierarchical porous microstructures. This work provides a new pathway of designing ultralight absorbers with the advantage of thin thickness and wide bandwidth. Excellent absorption performance is achieved at only 10% Co/C content level, a success to design ultralight absorbers.

325 citations

Journal ArticleDOI
TL;DR: In this article, a theoretical model was developed to predict the absorption and refraction of an aggregate of monomer units (a molecular aggregate, molecular crystal, or polymer) at any frequency.
Abstract: A theoretical classical model is developed to predict the absorption and refraction of an aggregate of monomer units (a molecular aggregate, molecular crystal, or polymer) at any frequency. The monomers are treated as having complex electronic polarizabilities whose frequency dependence is determined by the absorption bands of the isolated monomers.Polarizations in the aggregate induced by incident light are modified by Coulombic interactions between the monomers. No first‐order approximation is involved as in exciton theory. The molar extinction coefficient and molar refraction are obtained from normal modepolarizabilities found by solving an eigenvalue problem. The predicted absorption spectra agree (to first order in interaction energy) with exciton theory in the limit of weak coupling, with the hypochromism theory of Tinoco and Rhodes, and (for a classical oscillator model) with exciton theory for strong coupling. The oscillator strength sum rule is obeyed. The predicted spectrum of a pair of dyelike monomers is illustrated for the cases of weak, intermediate, and strong coupling.

325 citations

Journal ArticleDOI
O. Humbach, H. Fabian, U. Grzesik, U. Haken, W. Heitmann1 
TL;DR: In this article, the spectral position and relative intensities of bound hydroxyl (SiOH) absorption bands in state-of-the-art synthetic silica were investigated.
Abstract: The presence of bound hydroxyl (SiOH) in silica is well known to produce an optical fundamental absorption band at about 2.7 μm. For optical fiber applications the influence of the corresponding overtones and combination modes on the absorption spectrum are of significant importance. A literature review is presented which reveals uncertainties regarding the correct absorption band intensities as well as their spectral positions. We present precise data on spectral position and relative intensities of OH absorption bands in state of the art synthetic silica. Our investigations cover the influence of different manufacturing techniques, OH content, and a comparison of bulk and fiber data. With the knowledge of the conversion factors between the intensities of different OH absorption bands it is possible to predict the entire OH related transmission performance of an optical component by measurement of a single absorption band, e.g., the fundamental mode at 2.7 μm or the 1.38 μm band in the low loss range of optical fibers.

324 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2022185
20213,106
20202,866
20192,953
20182,876
20172,679