双向冷冻铸造构建各向异性石墨烯气凝胶具备频率可调声学吸收能力

1成果简介

噪声污染已成为现代社会的重大环境问题，开发高效、轻质、宽频声学衰减材料对于建筑隔音、交通工具降噪、工业设备消声等领域至关重要。石墨烯衍生物和碳纳米管凭借其优异的化学稳定性、力学性能和结构可调性，在声学衰减介质领域展现出巨大潜力。然而，低维纳米结构在多孔骨架中的精确形貌调控仍面临两大核心难题：①纳米片容易发生随机重新堆叠，丧失高比表面积优势；②难以实现均匀定向排列，限制了结构各向异性的有效利用。更重要的是，纯石墨烯气凝胶的声学性能——特别是石墨烯片层尺寸和负载量如何影响内部隔板效应和结构各向异性——迄今缺乏系统性研究。

本文，韩国公州大学Sung Ho Song教授和忠北大学Dong Ju Lee教授等在《RSC Advances》期刊发表名为"Frequency-tunable acoustic absorption in anisotropic graphene aerogels via morphological engineering of internal barriers"的论文。该研究通过双向冷冻铸造（bidirectional freeze-casting）技术，利用冰偏析诱导自组装（ISISA）过程，系统构建了具有高度有序、垂直和水平取向层状网络的各向异性石墨烯气凝胶，并通过内部隔板（septa）的形貌工程实现了频率可调的声吸收性能。

该策略的核心发现包括：(1)大片层石墨烯构建的气凝胶形成连续、流线型微通道，结构阻力最小；(2)小片层石墨烯构建的气凝胶则形成高密度内部结构隔板（septa），显著增加通道曲折度和气流阻力；(3) 高密度隔板通过增强粘热能耗散和多重散射效应，大幅提升声吸收性能；(4) 通过调控骨架空间取向与入射声波的相对方向，横向模式下的声吸收优于纵向模式，揭示了隔板效应对声吸收的各向异性增强机制。该工作建立了微观前驱体尺寸与宏观分级架构之间的结构-性能关系，为高性能碳基噪声绝缘材料的设计提供了新范式。

2图文导读

图1、Schematic representation of the synthesis and size-tailoring of GO. (a) Synthesis of raw GO via the modified Hummers' method involving chemical oxidation and purification. (b) Sequential size-reduction process: extraction of LGO via sedimentation during stirring, followed by the fabrication of MGO (750 W, 2 min) and SGO (750 W, 30 min) through time-controlled tip sonication.

图2、Morphological characterization and size distribution of GO samples. SEM images and corresponding histograms of (a) DGO showing uncontrolled sizes, (b) LGO (mostly >50 µm), (c) MGO (peak ∼ 10 µm), and (d) SGO (<1 µm). AFM topographical images and height profiles of (e) LGO, (f) MGO, and (g) SGO, confirming successful lateral size reduction while maintaining a sheet thickness below 2 nm.

图3、Characterization and structural analysis of Graphene Oxide (GO) samples with varying lateral sizes: Large GO (LGO), Medium GO (MGO), and Small GO (SGO). (a) Aqueous dispersion digital image and C 1s XPS analysis of LGO. (b) Aqueous dispersion digital image and C 1s XPS analysis of MGO. (c) Aqueous dispersion digital image and C 1s XPS analysis of LGO. (d) Raman spectra of LGO, MGO and SGO. (e) X-ray diffraction of LGO, MGO and SGO.

图4、Microstructural characterization of vertically aligned GO aerogels prepared from LGO, MGO, and SGO at various concentrations via bidirectional freezing. (a) Schematic illustration of the GO aerogel fabrication process using a bidirectional freezing technique. (b) Schematic of GO growth direction and SEM observation sites. (c) SEM images of GO aerogels: SEM images showing the cross-sectional morphologies of LGO-A, MGO-A, and SGO-A via concentration. Microstructural characterization of horizontally aligned GO aerogels prepared from LGO, MGO, and SGO at various concentrations via bidirectional freezing. (d) Schematic illustration of the GO aerogel fabrication process using a bidirectional freezing technique. (e) Schematic of GO growth direction and SEM observation sites. (f) SEM images of GO aerogels: SEM images showing the cross-sectional morphologies of LGO-A, MGO-A, and SGO-A via concentration.

图5、Comparison of the sound absorption coefficient between rLGO-A, rMGO-A and rSGO-A. (a) The image of the orientation of the sound absorber and the horizontal incidence of sound. (b) The sound absorption coefficient of rGO-A at an incident sound frequency of 10 Hz. (c) The sound absorption coefficient of rGO-A at an incident sound frequency of 30 Hz. (d) The sound absorption coefficient of rGO-A at an incident sound frequency of 50 Hz. (e) The sound absorption coefficient of rGO-A at an incident sound frequency of 100 Hz. Comparison of the sound absorption coefficient between rLGO-A, rMGO-A and rSGO-A. (f) The image of the orientation of the sound absorber and the vertical incidence of sound. (g) The sound absorption coefficient of rGO-A at an incident sound frequency of 10 Hz. (h) The sound absorption coefficient of rGO-A at an incident sound frequency of 30 Hz (i) The sound absorption coefficient of rGO-A at an incident sound frequency of 50 Hz. (j) The sound absorption coefficient of rGO-A at an incident sound frequency of 100 Hz.

图6、Schematic illustration of the sound absorption mechanism within a directionally antagonistic graphene absorber: (a) wave reflection in perpendicular rGO-A and (b) wave absorption in parallel rGO-A.

3小结

总而言之，该工作通过双向冷冻铸造和冰偏析诱导自组装（ISISA）技术，系统构建了具有高度有序各向异性层状结构的石墨烯气凝胶，揭示了内部隔板（septa）形貌对声吸收性能的关键调控作用。核心发现如下：

1. 石墨烯片层尺寸决定隔板形貌：大片层形成流线型微通道（低阻力），小片层形成高密度隔板（高曲折度、高气流阻力）；
2. 隔板密度决定声吸收强度：高密度隔板通过增强粘热能耗散和多重散射效应，显著提升声吸收性能和吸收带宽；
3. 骨架取向决定频率响应：横向模式（声波垂直于层状骨架传播）的声吸收优于纵向模式，隔板效应在横向取向下被最大化利用；
4. 三维协同调控实现频率可调：通过片层尺寸、骨架取向和负载量三个维度的协同调控，实现声吸收频率和强度的精准调谐。

该工作建立了微观前驱体尺寸→介观隔板形貌→宏观分级架构→声学性能的完整结构-性能关系框架，为高性能、轻质、频率可调碳基噪声绝缘材料的理性设计提供了新范式，在建筑声学、交通降噪、航空航太隔音等领域具有广阔应用前景。

文献：

• DOI
• https://doi.org/10.1039/D6RA01470D

来源：材料分析与应用