雙向冷凍鑄造構建各向異性石墨烯氣凝膠具備頻率可調聲學吸收能力

1成果簡介

噪聲污染已成為現代社會的重大環境問題，開發高效、輕質、寬頻聲學衰減材料對于建筑隔音、交通工具降噪、工業設備消聲等領域至關重要。石墨烯衍生物和碳納米管憑借其優異的化學穩定性、力學性能和結構可調性，在聲學衰減介質領域展現出巨大潛力。然而，低維納米結構在多孔骨架中的精確形貌調控仍面臨兩大核心難題：①納米片容易發生隨機重新堆疊，喪失高比表面積優勢；②難以實現均勻定向排列，限制了結構各向異性的有效利用。更重要的是，純石墨烯氣凝膠的聲學性能——特別是石墨烯片層尺寸和負載量如何影響內部隔板效應和結構各向異性——迄今缺乏系統性研究。

本文，韓國公州大學Sung Ho Song教授和忠北大學Dong Ju Lee教授等在《RSC Advances》期刊發表名為"Frequency-tunable acoustic absorption in anisotropic graphene aerogels via morphological engineering of internal barriers"的論文。該研究通過雙向冷凍鑄造（bidirectional freeze-casting）技術，利用冰偏析誘導自組裝（ISISA）過程，系統構建了具有高度有序、垂直和水平取向層狀網絡的各向異性石墨烯氣凝膠，并通過內部隔板（septa）的形貌工程實現了頻率可調的聲吸收性能。

該策略的核心發現包括：(1)大片層石墨烯構建的氣凝膠形成連續、流線型微通道，結構阻力最小；(2)小片層石墨烯構建的氣凝膠則形成高密度內部結構隔板（septa），顯著增加通道曲折度和氣流阻力；(3) 高密度隔板通過增強粘熱能耗散和多重散射效應，大幅提升聲吸收性能；(4) 通過調控骨架空間取向與入射聲波的相對方向，橫向模式下的聲吸收優于縱向模式，揭示了隔板效應對聲吸收的各向異性增強機制。該工作建立了微觀前驅體尺寸與宏觀分級架構之間的結構-性能關系，為高性能碳基噪聲絕緣材料的設計提供了新范式。

2圖文導讀

圖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.

圖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.

圖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.

圖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.

圖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.

圖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小結

總而言之，該工作通過雙向冷凍鑄造和冰偏析誘導自組裝（ISISA）技術，系統構建了具有高度有序各向異性層狀結構的石墨烯氣凝膠，揭示了內部隔板（septa）形貌對聲吸收性能的關鍵調控作用。核心發現如下：

1. 石墨烯片層尺寸決定隔板形貌：大片層形成流線型微通道（低阻力），小片層形成高密度隔板（高曲折度、高氣流阻力）；
2. 隔板密度決定聲吸收強度：高密度隔板通過增強粘熱能耗散和多重散射效應，顯著提升聲吸收性能和吸收帶寬；
3. 骨架取向決定頻率響應：橫向模式（聲波垂直于層狀骨架傳播）的聲吸收優于縱向模式，隔板效應在橫向取向下被最大化利用；
4. 三維協同調控實現頻率可調：通過片層尺寸、骨架取向和負載量三個維度的協同調控，實現聲吸收頻率和強度的精準調諧。

該工作建立了微觀前驅體尺寸→介觀隔板形貌→宏觀分級架構→聲學性能的完整結構-性能關系框架，為高性能、輕質、頻率可調碳基噪聲絕緣材料的理性設計提供了新范式，在建筑聲學、交通降噪、航空航太隔音等領域具有廣闊應用前景。

文獻：

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

來源：材料分析與應用