Strong EM wave absorption and lightweight are the foremost important factors that drive the real-world applications of the modern microwave absorbers. This work mainly deals with the design of highly efficient microwave absorbers, where a hierarchical carbon nanotube (CNT) forest is first grown on the carbon fiber (CF) through the catalytic chemical vapor deposition method. The hierarchical carbon nanotube grown on the carbon fiber (CNTCF) is then embedded in the epoxy matrix to synthesize lightweight nanocomposites for their use as efficient microwave absorbers. The morphological study shows that carbon nanotubes (CNTs) self-assemble to form a trapping center on the carbon fiber. The electromagnetic characteristics of resultant nanocomposites are investigated exclusively in the X-band (8.2–12.4 GHz) using the network analyzer. The synthesized nanocomposites, containing 0.35 and 0.50 wt % CNTCFs, exhibit excellent microwave absorption properties, which could be attributed to the better impedance matching conditions and high dielectric losses. The reflection loss (RL) of −42.0 dB (99.99% absorption) with −10 dB (90% absorption) and −20 dB (99% absorption) bandwidths of 2.7 and 1.16 GHz, respectively, is achieved for 0.35 wt % CNTCF loading at 2.5 mm thickness. The composite with 0.50 wt % CNTCF loading illustrates substantial absorption efficiency with the RL reaching −24.5 dB (99.65% absorption) at 9.8 GHz and −10 dB bandwidth comprising 84.5% of the entire X band. The excellent microwave properties obtained here are primarily due to the electric dipole polarization, interfacial polarization, and unique trapping center. These trapping centers basically induce multiple reflections and scatterings, which attenuate more microwave energy. This investigation opens a new approach for the development of extremely lightweight, small-thickness, and highly efficient microwave absorbers for X-band applications.

中文翻译：

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分层碳纳米管涂层碳纤维：超轻，薄，高效的微波吸收器

强大的电磁波吸收能力和轻便性是推动现代微波吸收器在现实世界中应用的最重要因素。这项工作主要涉及高效微波吸收器的设计，其中首先通过催化化学气相沉积法在碳纤维（CF）上生长分层碳纳米管（CNT）林。然后，将生长在碳纤维（CNTCF）上的分层碳纳米管嵌入环氧基质中，以合成轻质纳米复合材料，以用作高效微波吸收剂。形态研究表明，碳纳米管（CNT）自组装形成碳纤维上的捕获中心。使用网络分析仪仅在X波段（8.2-12.4 GHz）中研究了所得纳米复合材料的电磁特性。包含0.35和0.50 wt％的CNTCF的合成的纳米复合材料表现出优异的微波吸收性能，这可以归因于更好的阻抗匹配条件和高介电损耗。对于0.35 wt％的CNTCF负载，反射损耗（RL）分别为-20dB和-10dB（90％吸收）和-20dB（99％吸收），带宽分别为2.7和1.16 GHz，为-42.0 dB（99.99％）厚度为2.5毫米。CNTCF负载为0.50 wt％的复合材料显示出显着的吸收效率，其中RL在9.8 GHz频率下达到-24.5 dB（吸收为99.65％），带宽为-10 dB，占整个X频段的84.5％。此处获得的出色微波性能主要归因于电偶极极化，界面极化和独特的俘获中心。这些捕获中心基本上会引起多次反射和散射，从而衰减更多的微波能量。这项研究为开发用于X波段应用的超轻量，小厚度和高效微波吸收器开辟了一种新方法。