Jia Yujun, Ajayi Tosin D, Wahls Benjamin H, Ramakrishnan Kishore Ranganath, Ekkad Srinath, Xu Chengying
State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, P. R. China.
Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States.
ACS Appl Mater Interfaces. 2020 Dec 30;12(52):58005-58017. doi: 10.1021/acsami.0c17361. Epub 2020 Dec 17.
Achieving a high electrical conductivity while maintaining a good thermal insulation is often contradictory in the material design for the goal of simultaneous thermal protection and electromagnetic interference shielding. The reason is that materials with a high electrical conductivity often pertain a high thermal conductivity. To address this challenge, this study reports a multifunctional ceramic composite system for carbon fiber-reinforced polymer composites. The fabricated multifunctional ceramic composite system has a multilayer structure. The polymer-derived SiCN ceramic reinforced with yttria-stabilized zirconia fibers serves as the thermal protection and impedance-matching layer, while the yttria-stabilized zirconia fiber-reinforced SiCN ceramic with carbon nanotubes provides the electromagnetic interference shielding. The thermal conductance of the multilayered ceramic composite is about 22.5% lower compared to that of the carbon fiber-reinforced polymer composites. The thermal insulation test during the steady-state condition shows that the hybrid composite can be used up to 300 °C while keeping the temperature reaching the surface of carbon fiber-reinforced polymer composites at around 167.8 °C. The flame test was used to characterize the thermal protection capability under transient conditions. The hybrid composite showed temperature differences of 72.9 and 280.7 °C during the low- and high-temperature settings, respectively. The average total shielding efficiency per thickness of the fabricated four-layered ceramic composite system was 21.45 dB/mm, which showed a high reflection-dominant electromagnetic interference shielding. The average total shielding efficiency per thickness of the eight-layered composite system was 16.57 dB/mm, revealing a high absorption-dominant electromagnetic interference shielding. Typical carbon fiber-reinforced polymer composites reveal a reflection-dominant electromagnetic interference shielding. The electrons can freely move in the percolated carbon nanotubes within the inner layers of the composite material, which provide the improved electromagnetic interference shielding ability. The movement of electrons was impeded by the top and bottom layers whose thermal conduction relies on the lattice vibrations, resulting in a satisfactory thermal insulation of the composite materials and impedance matching with the free space. Results of this study showed that materials with a good thermal insulation and electromagnetic interference shielding can be obtained simultaneously by confining the electron movement inside the materials and refraining their movement at the skin surface.
在材料设计中，为实现同时具备热防护和电磁干扰屏蔽功能这一目标，要达到高电导率同时又保持良好的热绝缘性往往相互矛盾。原因在于，具有高电导率的材料通常也具有高导热率。为应对这一挑战，本研究报告了一种用于碳纤维增强聚合物复合材料的多功能陶瓷复合体系。所制备的多功能陶瓷复合体系具有多层结构。用氧化钇稳定的氧化锆纤维增强的聚合物衍生SiCN陶瓷用作热防护和阻抗匹配层，而含有碳纳米管的氧化钇稳定的氧化锆纤维增强SiCN陶瓷提供电磁干扰屏蔽。与碳纤维增强聚合物复合材料相比，多层陶瓷复合材料的热导率降低了约22.5%。稳态条件下的热绝缘测试表明，这种混合复合材料在高达300℃时仍可使用，同时使碳纤维增强聚合物复合材料表面的温度保持在约167.8℃。采用火焰测试来表征瞬态条件下的热防护能力。该混合复合材料在低温和高温设置下分别显示出72.9℃和280.7℃的温差。所制备的四层陶瓷复合体系每厚度的平均总屏蔽效率为21.45 dB/mm，显示出以反射为主的高电磁干扰屏蔽性能。八层复合体系每厚度的平均总屏蔽效率为16.57 dB/mm，表明是以吸收为主的高电磁干扰屏蔽性能。典型的碳纤维增强聚合物复合材料显示出以反射为主的电磁干扰屏蔽性能。电子可以在复合材料内层中渗流的碳纳米管内自由移动，这提供了增强的电磁干扰屏蔽能力。电子的移动受到顶层和底层的阻碍，顶层和底层的热传导依赖于晶格振动，从而使复合材料具有令人满意的热绝缘性能，并与自由空间实现阻抗匹配。本研究结果表明，通过限制材料内部电子的移动并抑制其在表面的移动，可以同时获得具有良好热绝缘和电磁干扰屏蔽性能的材料。
