Hadi Seyed Ehsan, Möller Elias, Nolte Sina, Åhl Agnes, Donzel-Gargand Olivier, Bergström Lennart, Holm Alexander
Department of Materials and Environmental Chemistry, Stockholm University, 106 91 Stockholm, Sweden.
Wallenberg Wood Science Center, Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden.
ACS Appl Mater Interfaces. 2024 Aug 28;16(34):45337-45346. doi: 10.1021/acsami.4c09654. Epub 2024 Aug 13.
Anisotropic cellulose nanofiber (CNF) foams represent the state-of-the-art in renewable insulation. These foams consist of large (diameter >10 μm) uniaxially aligned macropores with mesoporous pore-walls and aligned CNF. The foams show anisotropic thermal conduction, where heat transports more efficiently in the axial direction (along the aligned CNF and macropores) than in the radial direction (perpendicular to the aligned CNF and macropores). Here we explore the impact on axial and radial thermal conductivity upon depositing a thin film of reduced graphene oxide (rGO) on the macropore walls in anisotropic CNF foams. To obtain rGO films on the foam walls we developed liquid-phase self-assembly to deposit rGO in a layer-by-layer fashion. Using electron and ion microscopy, we thoroughly characterized the resulting rGO-CNF foams and confirmed the successful deposition of rGO. These hierarchical rGO-CNF foams show lower radial thermal conductivity (λ) across a wide range of relative humidity compared to CNF control foams. Our work therefore demonstrates a potential method for improved thermal insulation in anisotropic CNF foams and introduces versatile self-assembly for postmodification of such foams.
各向异性纤维素纳米纤维（CNF）泡沫代表了可再生隔热材料的最新技术水平。这些泡沫由大尺寸（直径>10μm）的单轴排列大孔组成，孔壁为中孔且含有排列的CNF。该泡沫表现出各向异性的热传导，即热量在轴向（沿着排列的CNF和大孔）比在径向（垂直于排列的CNF和大孔）更有效地传输。在此，我们探讨了在各向异性CNF泡沫的大孔壁上沉积一层还原氧化石墨烯（rGO）薄膜对轴向和径向热导率的影响。为了在泡沫壁上获得rGO薄膜，我们开发了液相自组装方法，以逐层方式沉积rGO。利用电子和离子显微镜，我们对所得的rGO-CNF泡沫进行了全面表征，并证实了rGO的成功沉积。与CNF对照泡沫相比，这些分级rGO-CNF泡沫在广泛的相对湿度范围内显示出较低的径向热导率（λ）。因此，我们的工作展示了一种改善各向异性CNF泡沫隔热性能的潜在方法，并引入了用于此类泡沫后修饰的通用自组装方法。
