Wang Chaozhi, Li Jiang, Guo Shaoyun
The State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University Chengdu 610065 China
RSC Adv. 2019 Jul 31;9(41):23843-23855. doi: 10.1039/c9ra04405a. eCollection 2019 Jul 29.
A broadband electromagnetic wave (EW) absorbing material should possess both wider effective absorption bandwidth and lower minimum reflection loss, depending on good impedance matching between the absorber and air and strong attenuation of EW. In this study, single-layer graphene/thermoplastic polyurethane (TPU) composite foams with different foam ratios and alternating multilayer graphene/TPU composite foams with different numbers of layers were prepared. Not only was the EW-absorbing mechanism of these composite foams examined, but also the relationship between the EW-absorbing properties and the number of layers were investigated. The single-layer sample S-5 with good impedance matching characteristics and S-3 with strong EW attenuation characteristics were selected as the constituent layers to design alternating multilayer graphene/TPU composite foams. Compared to the single-layer sample 4L-C (4L-C is defined as the monolayer sample S-4 with a thickness of 9 mm), the 4L alternating multilayer graphene/TPU composite foams could achieve more than 90% EW absorption in a wide frequency band of 8.5 GHz, and its minimum reflection loss was as low as -37.67 dB, which are very beneficial for its use as a lightweight, flexible electromagnetic wave absorbing material (EWAM) for broadband absorption. More importantly, the absorption of the obtained alternating multilayer composite foams could be simply modulated not only by the absorber thickness, but also by the number of layers to satisfy the applications in different frequency bands.
宽带电磁波（EW）吸收材料应具备更宽的有效吸收带宽和更低的最小反射损耗，这取决于吸收体与空气之间良好的阻抗匹配以及对电磁波的强衰减。在本研究中，制备了具有不同泡沫比例的单层石墨烯/热塑性聚氨酯（TPU）复合泡沫以及具有不同层数的交替多层石墨烯/TPU复合泡沫。不仅研究了这些复合泡沫的电磁波吸收机制，还研究了电磁波吸收性能与层数之间的关系。选择具有良好阻抗匹配特性的单层样品S - 5和具有强电磁波衰减特性的S - 3作为组成层，来设计交替多层石墨烯/TPU复合泡沫。与单层样品4L - C（4L - C定义为厚度为9 mm的单层样品S - 4）相比，4层交替多层石墨烯/TPU复合泡沫在8.5 GHz的宽频带内可实现超过90%的电磁波吸收，其最小反射损耗低至 - 37.67 dB，这对于其作为用于宽带吸收的轻质、柔性电磁波吸收材料（EWAM）非常有利。更重要的是，所获得的交替多层复合泡沫的吸收不仅可以通过吸收体厚度简单调节，还可以通过层数调节，以满足不同频带的应用需求。
