微尺度化学
纳米纤维素
热扩散率
多孔性
材料科学
气凝胶
纳米尺度
保温
化学工程
传热
复合材料
热的
纳米技术
纤维素
热力学
图层(电子)
数学教育
工程类
物理
数学
作者
Koh Sakai,Yuri Kobayashi,Tsuguyuki Saito,Akira Isogai
摘要
Abstract High porosity solids, such as plastic foams and aerogels, are thermally insulating. Their insulation performance strongly depends on their pore structure, which dictates the heat transfer process in the material. Understanding such a relationship is essential to realizing highly efficient thermal insulators. Herein, we compare the heat transfer properties of foams and aerogels that have very high porosities (97.3–99.7%) and an identical composition (nanocellulose). The foams feature rather closed, microscale pores formed with a thin film-like solid phase, whereas the aerogels feature nanoscale open pores formed with a nanofibrous network-like solid skeleton. Unlike the aerogel samples, the thermal diffusivity of the foam decreases considerably with a slight increase in the solid fraction. The results indicate that for suppressing the thermal diffusion of air within high porosity solids, creating microscale spaces with distinct partitions is more effective than directly blocking the free path of air molecules at the nanoscale.
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