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Lightweight and efficient microwave absorbing material based on walnut shell-derived nano-porous carbon


Lightweight microwave absorbing materials have drawn tremendous attention. Herein, nano-porous biomass carbon materials have been prepared by carbonization with subsequent potassium hydroxide activation of the walnut shell and the microwave absorption properties have also been investigated. The obtained samples feature large specific surface areas and with numerous micropores and nanopores. The sample activated at 600 ℃ with the specific surface area of 736.2m2/g exhibits the most excellent microwave absorption performance. It has the maximum reflection loss of -42.4 dB at 8.88 GHz and the effective absorption bandwidth (the reflection loss below -10 dB) is 1.76 GHz (from 8.08 GHz to 9.84 GHz), corresponding to thickness of 2 mm. Additionally, the effective absorption bandwidth can reach 2.24 GHz (from 10.48 GHz to 12.72 GHz) when the absorber thickness is 1.5 mm. Three-dimensional porous architecture, interfacial polarization relaxation loss, and the dipolar relaxation loss make great contribution to the excellent microwave absorption performance. In contrast, the non-activated sample with lower specific surface area (435.3m2/g) has poor microwave absorption performance due to poor dielectric loss capacity. This comparison highlights the role of micropores and nanopores in improving dielectric loss property of the porous carbon materials. To sum up, porous biomass carbon has great potential for lightweight microwave absorbers. Moreover, KOH is a kind of efficient activation agent in the fabrication of carbonaceous materials.

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Publication details

The article was received on 12 Apr 2017, accepted on 04 May 2017 and first published on 05 May 2017

Article type: Paper
DOI: 10.1039/C7NR02628E
Citation: Nanoscale, 2017, Accepted Manuscript
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    Lightweight and efficient microwave absorbing material based on walnut shell-derived nano-porous carbon

    X. Qiu, L. Wang, H. Zhu, Y. Guan and Q. Zhang, Nanoscale, 2017, Accepted Manuscript , DOI: 10.1039/C7NR02628E

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