Strengthening and aging of wet silica gels for up-scaling of aerogel preparation
Strengthening and aging of wet silica gels for up-scaling of aerogel preparation
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DOI：
10.1007/s10971-006-1505-7
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发表时间：
2007-03-01
影响因子：
2.5
通讯作者：
Einarsrud, M. -A.
中科院分区：
文献类型：
--
作者：
Strom, R. A.;Masmoudi, Y.;Einarsrud, M. -A.
为了提高用于气凝胶生产的湿凝胶的机械性能，使用三种不同的途径进行了老化研究。使用 HF 作为催化剂，由聚乙氧基二硅氧烷前体制备湿凝胶。研究的三种不同的老化路线是i）在密封模具中老化，ii）在溶剂中老化和iii）在模拟孔隙液体中老化，即含有少量水和HF的溶剂，类似于母液。所有老化过程都产生更强和更硬的湿凝胶，然而，在一定的老化时间后观察到强度和刚度的最大值。模拟孔隙液体允许8小时范围内的较短老化时间来达到最大机械强度，但最大强度低于其他两种老化路线。通过小规模、中规模和大规模的超临界干燥，从湿凝胶中获得整体透明的气凝胶。时效强化工艺已成功转移到更大的规模，与小规模相比，密度更低，透明度更高。
In order to enhance the mechanical properties of wet gels for aerogel production, aging studies by using three different routes was performed. The wet gels were prepared from a polyethoxydisiloxane precursor by using HF as a catalyst. The three different aging routes studied were i) aging in sealed mould, ii) aging in solvent and iii) aging in simulated pore liquid, i.e. a solvent with small amounts of water and HF resembling the mother liquor. All aging processes gave stronger and stiffer wet gels however, a maximum in strength and stiffness was observed after a certain aging time. The simulated pore liquids allowed short aging time in the range of 8 h to achieve the maximum mechanical strength, however the maximum in strength was lower than for the other two aging routes. From the wet gels, monolithic and transparent aerogels were obtained by supercritical drying at small-, mid- and large-scale. The aging strengthening process was successfully transferred to larger scales giving both lower density and higher transparency compared to small-scale.