PDF(Pubmed)
Abstract：
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 (λr) 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.
摘要：
各向异性纤维素纳米纤维(CNF)泡沫代表可再生绝缘中的现有技术。这些泡沫由大的(直径>10μm)单轴排列的大孔与中孔孔壁和排列的CNF组成。泡沫显示出各向异性的热传导，其中热量在轴向方向上(沿着对齐的CNF和大孔)比在径向方向上(垂直于对齐的CNF和大孔)更有效地传输。在这里，我们探讨了在各向异性CNF泡沫中的大孔壁上沉积还原氧化石墨烯（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膜,我们开发了液相自组装以逐层方式沉积rGO。使用电子和离子显微镜，我们彻底表征了所得的rGO-CNF泡沫并证实了rGO的成功沉积。与CNF对照泡沫相比,这些分层rGO-CNF泡沫在宽范围的相对湿度下显示出较低的径向热导率(λr)。因此，我们的工作证明了一种在各向异性CNF泡沫中改善隔热的潜在方法，并引入了用于此类泡沫后改性的通用自组装。
