To avoid high reflectivity problems due to impedance mismatch on the surface of electromagnetic interference (EMI) shielding materials, absorption-dominated materials are favorable nowadays and can effectively solve the problem of electromagnetic pollution. Herein, we propose a novel and facile method to prepare absorption-dominated EMI shielding materials by combining an insulating porous absorption layer with a highly conductive reflective layer. The porous materials were obtained by initiating click chemistry of polyethylene glycol diacrylate (PEGDA) and pentaerythritol tetrakis(3-mercapto-propionate) (PETMP) on melamine foam. Without adding any conductive and magnetic materials, the composite porous polymer was used as the absorbing layer, and then loaded Mxene/Cellulose nanofiber(Mxene/CNF) film as the reflecting layer at the bottom. Due to the combination of absorption-reflection-reabsorption effects on electromagnetic waves, the porous composites obtained achieved an average shielding efficiency (SE) of 47.2 dB and a high absorptivity of 0.972, which are the highest values known for similar structures. Furthermore, a rise in reflectivity of the porous materials with increasing thickness was found, and a multiple transmission line model was proposed to explain the phenomenon. This composite material with excellent EMI SE and high absorption performance has a broad application prospect in the field of construction and defense industry. In addition, the waterborne polyurethane/MXene/CNF (WPU/MXene/CNF) composites prepared using the same method also achieved a high absorptivity of 0.730, which further demonstrates the high efficiency of this method.

中文翻译：

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绝缘吸收层与导电反射层相结合实现超高吸收效果的电磁屏蔽材料


为了避免电磁干扰(EMI)屏蔽材料表面阻抗不匹配导致的高反射率问题，目前以吸收为主的材料是有利的，可以有效解决电磁污染问题。在此，我们提出了一种新颖且简便的方法，通过将绝缘多孔吸收层与高导电反射层相结合来制备以吸收为主的 EMI 屏蔽材料。通过在三聚氰胺泡沫上引发聚乙二醇二丙烯酸酯（PEGDA）和季戊四醇四（3-巯基丙酸酯）（PETMP）的点击化学获得多孔材料。在不添加任何导电和磁性材料的情况下，复合多孔聚合物作为吸收层，然后在底部加载Mxene/纤维素纳米纤维（Mxene/CNF）薄膜作为反射层。由于电磁波吸收-反射-再吸收效应的结合，所获得的多孔复合材料实现了47.2 dB的平均屏蔽效率（SE）和0.972的高吸收率，这是已知的类似结构的最高值。此外，发现多孔材料的反射率随着厚度的增加而增加，并提出了多传输线模型来解释这种现象。这种具有优异EMI SE和高吸收性能的复合材料在建筑和国防工业领域具有广阔的应用前景。此外，采用相同方法制备的水性聚氨酯/MXene/CNF（WPU/MXene/CNF）复合材料也取得了0.730的高吸收率，进一步证明了该方法的高效性。