Engineering mesoporous silica for superior optical and thermal properties
Engineering mesoporous silica for superior optical and thermal properties
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DOI：
10.1557/mre.2020.40
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发表时间：
2020-07
影响因子：
4.3
通讯作者：
Danielle M. Butts;Patricia E. McNeil;Michal Marszewski;E. Lan;Tiphaine Galy;Man Li;J. Kang;David S
中科院分区：
文献类型：
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作者：
Danielle M. Butts;Patricia E. McNeil;Michal Marszewski;E. Lan;Tiphaine Galy;Man Li;J. Kang;David S
我们报告了在隔热透明材料方面的重大进展：具有可控孔隙率的硅基整体，它结合了窗口的透明度和与气凝胶相当的导热系数。缺乏透明的隔热窗户导致商业和住宅建筑的大量热量损失，占美国每年一次能源消耗的4.2%。本研究为解决这一问题提供了一个潜在的解决方案，证明了常压干燥的二氧化硅气凝胶整体，即模糊物，可以在没有超临界干燥的情况下同时获得高光学透明度和低导热系数。采用正硅酸乙酯、甲基三乙氧基硅烷和凝胶化后表面改性前驱体的组合，合成了具有不同孔含量和孔径大小的常温干燥材料。通过控制合成和工艺条件，制备了厚度为0.5~3 mm、透过率为95%、导热系数为0.04W/(MK)的介孔材料。较窄的孔径分布(~lt；15 nm)导致了良好的透明度和低雾度，而孔隙率超过80%则导致低导热系数。提出了一个考虑分维和声子边界散射的热输运模型来解释测量到的低有效导热系数。这项工作为透明、节能窗户的设计提供了新的见解。
We report a significant advance in thermally insulating transparent materials: silica-based monoliths with controlled porosity which exhibit the transparency of windows in combination with a thermal conductivity comparable to aerogels. The lack of transparent, thermally insulating windows leads to substantial heat loss in commercial and residential buildings, which accounts for ~4.2% of primary US energy consumption annually. The present study provides a potential solution to this problem by demonstrating that ambiently dried silica aerogel monoliths, i.e., ambigels, can simultaneously achieve high optical transparency and low thermal conductivity without supercritical drying. A combination of tetraethoxysilane, methyltriethoxysilane, and post-gelation surface modification precursors were used to synthesize ambiently dried materials with varying pore fractions and pore sizes. By controlling the synthesis and processing conditions, 0.5–3 mm thick mesoporous monoliths with transmittance >95% and a thermal conductivity of 0.04 W/(m K) were produced. A narrow pore size distribution, <15 nm, led to the excellent transparency and low haze, while porosity in excess of 80% resulted in low thermal conductivity. A thermal transport model considering fractal dimension and phonon-boundary scattering is proposed to explain the low effective thermal conductivity measured. This work offers new insights into the design of transparent, energy saving windows.