School of Materials Science and Engineering, Nanyang Technological University , 50 Nanyang Avenue, Singapore 639798, Singapore.
Beijing Key Laboratory of Lightweight Multi-functional Composite Materials and Structures, Beijing Institute of Technology , Beijing 100081, China.
ACS Appl Mater Interfaces. 2017 Sep 20;9(37):32211-32219. doi: 10.1021/acsami.7b07643. Epub 2017 Sep 8.
Flexible waterborne polyurethane (WPU)/silver nanowire (AgNW) nanocomposites with unidirectionally aligned micrometer-sized pores are fabricated using a facile freeze-drying process, and their dimensions, densities, and AgNW contents are easily controllable. The high-aspect-ratio AgNWs are well-dispersed in the nanocomposite cell walls, giving the nanocomposites good compression strength and excellent electrical conductivity even at very low densities. The large conductivity mismatch between the AgNWs and WPU also induces substantial interfacial polarization that benefits the absorption of electromagnetic (EM) waves, whereas the aligned cell walls promote multireflections of the waves in the porous architectures, further facilitating the absorption. The synergistic actions of the AgNWs, WPU, and unidirectionally aligned pores lead to ultrahigh EM shielding performance. The X-band shielding effectiveness (SE) of the nanocomposites is 64 and 20 dB at the densities of merely 45 and 8 mg/cm, respectively, and ultrahigh surface specific SE of ∼1087 dB cm/(g mm) is achieved with only 0.027 vol % AgNWs, demonstrating that they are promising ultralight, flexible, mechanically robust, high-performance EM shielding materials.
采用简便的冷冻干燥工艺制备了具有各向异性微米级孔的柔性水性聚氨酯（WPU）/银纳米线（AgNW）纳米复合材料，其尺寸、密度和 AgNW 含量易于控制。高纵横比的 AgNW 在纳米复合材料的细胞壁中得到了很好的分散，赋予了纳米复合材料优异的压缩强度和导电性，即使在密度非常低的情况下也是如此。AgNW 和 WPU 之间的大导电性失配也会引起显著的界面极化，有利于电磁波（EM）波的吸收，而定向的细胞壁则促进了波在多孔结构中的多次反射，进一步促进了吸收。AgNW、WPU 和定向排列的孔的协同作用导致了超高的电磁屏蔽性能。在密度仅为 45 和 8 mg/cm 时，纳米复合材料的 X 波段屏蔽效能（SE）分别达到了 64 和 20 dB，并且仅使用 0.027 体积%的 AgNW 就实现了超高的表面比 SE 约为 1087 dB cm/（g mm），表明它们是很有前途的超轻、柔性、机械坚固、高性能的电磁屏蔽材料。
