As a common environmental pollutant, microwave can cause great harms to human health. The development of high-performance microwave absorber with lightweight is indeed necessary. Herein, “rattan-like” graphene-based composite aerogels, having macroscopic pores surrounded by plenty of small pores, were designed and fabricated via an in-situ foaming then carbonized approach. Firstly, graphene oxide (GO), nanocellulose and ferrous ions were integrated into an aerogel with uniform large pores via a freeze-casting method. Then, the aerogel was immersed into a HO solution, during which bubble clusters generated in situ. These bubbles were driven into the stacked GO sheets and formed small pores. With the increase of the HO concentration from 0.5 to 10 wt%, the count percentage of the small pores in the aerogel increased from 81.5 to 95.2%. After the final carbonization, the graphene sheets were dually interconnected with magnetic nanoparticles and carbonized nanocellulose. The unique porous structure and dual-connected networks endowed the aerogel with enhanced conductive loss and optimized impedance matching capacity, and thus an excellent microwave absorption performance, whose maximum reflection loss achieves −68.5 dB. Further, the aerogel also exhibited superior sound absorption performance (noise reduction coefficient up to 0.91 in 1000–6300 Hz), and good mechanical stability.

中文翻译：

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一种可控发泡方法，用于制造具有理想微波吸收能力的“藤状”石墨烯基复合气凝胶

微波作为一种常见的环境污染物，会对人体健康造成极大的危害。开发高性能、轻量化的微波吸收体确实很有必要。在此，通过原位发泡然后碳化的方法设计和制造了“藤状”石墨烯基复合气凝胶，该气凝胶具有被大量小孔包围的宏观孔。首先，通过冷冻铸造方法将氧化石墨烯（GO）、纳米纤维素和亚铁离子整合成具有均匀大孔的气凝胶。然后，将气凝胶浸入 H2O 溶液中，在此过程中原位产生气泡簇。这些气泡被驱赶到堆叠的GO片中并形成小孔。随着H2O浓度从0.5%增加到10%，气凝胶中小孔的数量百分比从81.5%增加到95.2%。最终碳化后，石墨烯片与磁性纳米粒子和碳化纳米纤维素双重互连。独特的多孔结构和双连接网络赋予气凝胶增强的传导损耗和优化的阻抗匹配能力，从而具有优异的微波吸收性能，其最大反射损耗达到-68.5 dB。此外，气凝胶还表现出优异的吸声性能（在1000-6300 Hz范围内降噪系数高达0.91）和良好的机械稳定性。