Abstract A rapid and controlled reduction method of graphene oxide (GO) along with their performances as broadband frequency absorbers is demonstrated in this report. The microwave-controlled rapid GO reduction technique was adopted to control the exfoliation, structural defects, and the localized electron concentrations while keeping the carbon network in graphene intact. The reduction technique is facile and scalable to produce gram-scale graphene with a controlled manner for preparing a sprayable, lightweight coating (coating thickness ~100–120 μm) throughout a large-area (~225 mm diagonal distances) substrate. The as-prepared coating was explored as active broadband frequency absorbing material in the 4–15 GHz frequency region. We obtained extraordinary absorption properties with an absorptivity average ~96% along with the successive broadening of the bandwidth of ~8.5 GHz throughout the absorption band. The retrieved real and imaginary parts of the surface impedance signify proper impedance matching with the free space; thereby providing high absorption at the aforementioned frequency band. The presence of residual oxygen-containing functional groups results in the differential ability to accumulate electrons, which generate the electric dipole under alternating electromagnetic field while electron hysteresis in these dipoles results in additional surface polarization, which effectively increases the microwave absorption potential of rGO compared to pristine GO.

中文翻译：

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石墨烯中的缺陷重建具有出色的宽带吸收特性和增强的带宽

摘要 本报告展示了氧化石墨烯 (GO) 的快速可控还原方法及其作为宽带频率吸收剂的性能。采用微波控制的快速 GO 还原技术来控制剥离、结构缺陷和局部电子浓度，同时保持石墨烯中的碳网络完整。该还原技术简单且可扩展，以可控方式生产克级石墨烯，以在大面积（~225 毫米对角线距离）基板上制备可喷涂的轻质涂层（涂层厚度~100-120 μm）。所制备的涂层被探索为 4-15 GHz 频率范围内的活性宽带频率吸收材料。我们获得了非凡的吸收特性，平均吸收率约为 96%，并且整个吸收带的带宽不断扩大至 8.5 GHz。检索到的表面阻抗的实部和虚部表示与自由空间的适当阻抗匹配；从而在上述频带提供高吸收。残留含氧官能团的存在导致电子积累能力的差异，在交变电磁场下产生电偶极子，而这些偶极子中的电子滞后导致额外的表面极化，与 rGO 相比，这有效地增加了微波吸收电位原始的GO。检索到的表面阻抗的实部和虚部表示与自由空间的适当阻抗匹配；从而在上述频带提供高吸收。残留含氧官能团的存在导致电子积累能力的差异，在交变电磁场下产生电偶极子，而这些偶极子中的电子滞后导致额外的表面极化，与 rGO 相比，这有效地增加了微波吸收电位原始的GO。检索到的表面阻抗的实部和虚部表示与自由空间的适当阻抗匹配；从而在上述频带提供高吸收。残留含氧官能团的存在导致电子积累能力的差异，在交变电磁场下产生电偶极子，而这些偶极子中的电子滞后导致额外的表面极化，与 rGO 相比，这有效地增加了微波吸收电位原始的GO。