Di Andi, Schiele Carina, Hadi Seyed Ehsan, Bergström Lennart
Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, 10691, Sweden.
Wallenberg Wood Science Center, Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, 10691, Sweden.
Adv Mater. 2023 Nov;35(48):e2305195. doi: 10.1002/adma.202305195. Epub 2023 Oct 24.
Low-density foams and aerogels based on upcycled and bio-based nanofibers and additives are promising alternatives to fossil-based thermal insulation materials. Super-insulating foams are prepared from upcycled acid-treated aramid nanofibers (upANF ) obtained from Kevlar yarn and tempo-oxidized cellulose nanofibers (CNF) from wood. The ice-templated hybrid upANF /CNF-based foams with an upANF content of up to 40 wt% display high thermal stability and a very low thermal conductivity of 18-23 mW m K perpendicular to the aligned nanofibrils over a wide relative humidity (RH) range of 20% to 80%. The thermal conductivity of the hybrid upANF /CNF foams is found to decrease with increasing upANF content (5-20 wt%). The super-insulating properties of the CNF-upANF hybrid foams are related to the low density of the foams and the strong interfacial phonon scattering between the very thin and partially branched upANF and CNF in the hybrid foam walls. Defibrillated nanofibers from textiles are not limited to Kevlar, and this study can hopefully inspire efforts to upcycle textile waste into high-performance products.
基于升级再造和生物基纳米纤维及添加剂的低密度泡沫和气凝胶，有望成为化石基保温材料的替代物。超级绝缘泡沫由从凯夫拉纤维纱线中获得的经酸处理的升级再造芳纶纳米纤维（upANF）和来自木材的氧化 TEMPO 纤维素纳米纤维（CNF）制备而成。upANF 含量高达 40 wt% 的冰模板法 upANF/CNF 基混合泡沫，在 20% 至 80% 的宽相对湿度（RH）范围内，垂直于排列的纳米原纤显示出高的热稳定性和极低的热导率，为 18 - 23 mW m⁻¹ K⁻¹。发现 upANF/CNF 混合泡沫的热导率随着 upANF 含量（5 - 20 wt%）的增加而降低。CNF-upANF 混合泡沫的超级绝缘性能与泡沫的低密度以及混合泡沫壁中非常细且部分分支的 upANF 和 CNF 之间强烈的界面声子散射有关。来自纺织品的解纤纳米纤维不限于凯夫拉纤维，这项研究有望激发人们将纺织废料升级再造为高性能产品的努力。
