Ambient-dried thermal superinsulating monolithic silica-based aerogels with short cellulosic fibers
详细信息 查看全文
- 作者：Gediminas Markevicius ; Rachid Ladj ; Philipp Niemeyer…
- 刊名：Journal of Materials Science
- 出版年：2017
- 出版时间：February 2017
- 年：2017
- 卷：52
- 期：4
- 页码：2210-2221
- 全文大小：
- 刊物类别：Chemistry and Materials Science
- 刊物主题：Materials Science, general; Characterization and Evaluation of Materials; Polymer Sciences; Continuum Mechanics and Mechanics of Materials; Crystallography and Scattering Methods; Classical Mechanics;
- 出版者：Springer US
- ISSN：1573-4803
- 卷排序：52
文摘
Short (<2.5 mm) cellulose fiber–silica composite aerogels were synthesized by dispersing cellulose fibers in polyethoxydisiloxane-based sol. After in situ gelation, silica phase was hydrophobized with hexamethyldisilazane, and the composites were dried either at ambient pressure or with supercritical (sc) CO2. Fiber concentration was varied from 0 to 25 wt% (corresponding to 0–2.1 vol%) of the final dried composite. Preformed cellulosic fiber network preserved the monolithic shape of the silica-based composites during ambient drying. At room conditions, thermal conductivities were 0.015 ± 0.001 W/(m K) for sc-dried aerogels and 0.017 ± 0.001 W/(m K) for their ambient-dried counterparts. Materials dried with either method exhibited large specific surface areas, from 570 to 730 m2/g, and SEM analysis did not show significant differences in the global structure of the silica network. Composite aerogels were hydrophobic with water contact angles around 138°. Based on this proof of concept, the same approach was used with a variety of natural and recycled cellulosic fibers also resulting in silica-based monoliths with low thermal conductivities in the 0.016–0.023 W/(m K) range, all produced via ambient drying.