Nowadays, carbon frameworks derived from natural biomaterials have attracted extensive attention for electromagnetic interference (EMI) shielding due to their renewability and affordability. However, it is critical and challenging to achieve effective regulation of shielding effectiveness (SE) as well as weaken the strong EM reflection of highly conductive biomass-based carbon materials. Herein, commercial cotton pads with oriented structure were selected as carbonaceous precursor to fabricate aligned carbon networks by pyrolysis, and the EMI SE of the samples with increased temperature of 800-1000°C can be accurately controlled in the effective range of ∼21.7-29.1, ∼27.7-37.1 and ∼32.7-43.3 dB with high reflection coefficient of >0.8 by changing the cross-angle between the electric-field direction of incident EM waves and the fiber-orientation direction due to the occurrence of opposite internal electric field. Moreover, the further construction of Salisbury absorber-liked double-layer structure could result in an ultra-low reflection coefficient of only ∼0.06 but enhanced SE variation range up to ∼38.7-49.3 dB during the adjustment of cross-angle, possibly due to the destructive interference of EM waves in the double-layer carbon networks. This work would provide a simple and effective way for constructing high-performance biomass carbon materials with adjustable EMI shielding and ultra-low reflectivity.

如今，源自天然生物材料的碳框架由于其可再生性和可负担性而在电磁干扰 (EMI) 屏蔽方面引起了广泛关注。然而，实现屏蔽效能（SE）的有效调节以及削弱高导电生物质基碳材料的强电磁反射是至关重要的和具有挑战性的。在此，选择具有定向结构的商用棉垫作为碳质前驱体，通过热解制备排列的碳网络，升温 800-1000°C 的样品的 EMI SE 可以精确控制在 ~21.7-29.1 的有效范围内, ~27.7-37.1 和 ~32.7-43.3 dB，具有 >0 的高反射系数。由于相反的内部电场的出现，通过改变入射电磁波的电场方向和纤维取向方向之间的交叉角，如图8所示。此外，Salisbury 类吸收体双层结构的进一步构建可能导致超低反射系数仅为 ~0.06，但在调整交叉角期间，SE 变化范围提高至 ~38.7-49.3 dB，这可能是由于电磁波在双层碳网络中的相消干涉。这项工作将为构建具有可调EMI屏蔽和超低反射率的高性能生物质碳材料提供一种简单有效的方法。进一步构建类似索尔兹伯里吸收体的双层结构可能会导致超低反射系数仅为 ~0.06，但在调整交叉角期间，SE 变化范围增加至 ~38.7-49.3 dB，可能是由于破坏性电磁波在双层碳网络中的干扰。这项工作将为构建具有可调EMI屏蔽和超低反射率的高性能生物质碳材料提供一种简单有效的方法。进一步构建类似索尔兹伯里吸收体的双层结构可能会导致超低反射系数仅为 ~0.06，但在调整交叉角期间，SE 变化范围增加至 ~38.7-49.3 dB，可能是由于破坏性电磁波在双层碳网络中的干扰。这项工作将为构建具有可调EMI屏蔽和超低反射率的高性能生物质碳材料提供一种简单有效的方法。