纳米纤维素
各向异性
热导率
保温
材料科学
气凝胶
热的
复合材料
各向同性
纤维素
光学
物理
化学工程
工程类
气象学
图层(电子)
作者
Tian Li,Jianwei Song,Xinpeng Zhao,Yang Liu,Glenn Pastel,Shaomao Xu,Chao Jia,Jiaqi Dai,Chaoji Chen,Amy Gong,Feng Jiang,Yonggang Yao,Tianzhu Fan,Bao Yang,Lars Wågberg,Ronggui Yang,Liangbing Hu
出处
期刊:Science Advances
[American Association for the Advancement of Science (AAAS)]
日期:2018-03-02
卷期号:4 (3)
被引量:353
标识
DOI:10.1126/sciadv.aar3724
摘要
There has been a growing interest in thermal management materials due to the prevailing energy challenges and unfulfilled needs for thermal insulation applications. We demonstrate the exceptional thermal management capabilities of a large-scale, hierarchal alignment of cellulose nanofibrils directly fabricated from wood, hereafter referred to as nanowood. Nanowood exhibits anisotropic thermal properties with an extremely low thermal conductivity of 0.03 W/m·K in the transverse direction (perpendicular to the nanofibrils) and approximately two times higher thermal conductivity of 0.06 W/m·K in the axial direction due to the hierarchically aligned nanofibrils within the highly porous backbone. The anisotropy of the thermal conductivity enables efficient thermal dissipation along the axial direction, thereby preventing local overheating on the illuminated side while yielding improved thermal insulation along the backside that cannot be obtained with isotropic thermal insulators. The nanowood also shows a low emissivity of <5% over the solar spectrum with the ability to effectively reflect solar thermal energy. Moreover, the nanowood is lightweight yet strong, owing to the effective bonding between the aligned cellulose nanofibrils with a high compressive strength of 13 MPa in the axial direction and 20 MPa in the transverse direction at 75% strain, which exceeds other thermal insulation materials, such as silica and polymer aerogels, Styrofoam, and wool. The excellent thermal management, abundance, biodegradability, high mechanical strength, low mass density, and manufacturing scalability of the nanowood make this material highly attractive for practical thermal insulation applications.
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