Kim Taehoon, Do Hyung Wan, Choi Kyu-Jong, Kim Sungsoon, Lee Minwoo, Kim Taeyoung, Yu Byung-Kyu, Cheon Jinwoo, Min Byung-Wook, Shim Wooyoung
Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Korea.
Center for Multi-Dimensional Materials, Yonsei University, Seoul 03722, Korea.
Nano Lett. 2021 Jan 27;21(2):1132-1140. doi: 10.1021/acs.nanolett.0c04593. Epub 2021 Jan 13.
Ideal electromagnetic (EM) wave absorbers can absorb all incident EM waves, regardless of the incident direction, polarization, and frequency. Absorptance and reflectance are intrinsic material properties strongly correlated with electrical conductivity; hence, achieving perfect absorptance with zero reflectance is challenging. Herein, we present a design strategy for preparing a nearly ideal EM absorber based on a layered metal that maximizes absorption by utilizing multiple internal reflections and minimizes reflection using a monotonic gradient of intrinsic impedance. This approach was experimentally verified using aluminum nanoflakes prepared via topochemical etching of lithium from LiAl, and the impedance-graded structure was obtained through the size-based sorting behavior of aluminum nanoflakes sinking in dispersion. Unlike in traditional shielding materials, strong absorption (26.76 dB) and negligible reflectivity (0.04 dB) with a ratio of >10 can be achieved in a 120 μm thick film. Overall, our findings exhibit potential for developing a novel class of antireflective shielding materials.
理想的电磁波（EM）吸收体能够吸收所有入射的电磁波，而不论其入射方向、偏振和频率如何。吸收率和反射率是与电导率密切相关的固有材料特性；因此，实现零反射的完美吸收率具有挑战性。在此，我们提出一种基于层状金属制备近乎理想的EM吸收体的设计策略，该策略通过利用多次内部反射使吸收最大化，并利用固有阻抗的单调梯度使反射最小化。使用通过从LiAl中对锂进行拓扑化学蚀刻制备的铝纳米片对该方法进行了实验验证，并且通过铝纳米片在分散体中下沉的基于尺寸的分选行为获得了阻抗分级结构。与传统屏蔽材料不同，在120μm厚的薄膜中可实现大于10的强吸收（26.76dB）和可忽略不计的反射率（0.04dB）。总体而言，我们的研究结果显示出开发新型抗反射屏蔽材料的潜力。
