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Biomass-derived porous carbon has drawn extensive attention in the microwave absorbing materials (MAMs) due to the advantages of extensive sources, low-cost, sustainability and tailorable structure. Aimtolight-weight biomass-derived MAMs with high attenuation capacity over wide frequency range, longan shell-based porous carbon material (LSPC) was prepared by activated carbonization by using different activators, namely phosphoric acid (H3PO4), potassium hydroxide (KOH) and zinc chloride (ZnCl2). Influence of activation on the microstructure, morphology and microwave absorbing performance of resulted porous carbon materials were systematically investigated by applying X-ray diffraction, Raman spectroscopy, scanning electron microscopyvector network analyzer. Results indicate that activation induced more amorphous regions and defects, thus forming more heterogeneous interface and polarization centers conducing to the dielectric loss. Compared with LSPC with thick and smooth skeletons, activated LSPC materials showed hierarchical structures with different scale pores. While LSPC-H3PO4 exhibited thinner wall of pores and LSPC-ZnCl2 showed smaller pores on the skeleton, LSPC-KOH depicted vertebra-like hierarchical structure. Activation improved the microwave absorbing performance, and LSPC-KOH showed the best microwave capacity, with minimum reflection loss of -43.57 dB, which was 2.03 times and 3.02 times higher than that of LSPC-H3PO4 and LSPC-ZnCl2, respectively. Moreover, activation broadened the effective absorption bandwidth of LSPC to varying degrees. Analysis of structure-associated electromagnetic loss behavior implies that hierarchical structure, dipolar/interfacial polarization and multiple reflection greatly contribute to the balanced impedance matching and attenuation capacity, thus improving the microwave absorption performance of activated LSPC materials.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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