目的 探索二氧化硅气凝胶复合材料在长时高温环境中的性能变化规律,为其作为长时使用隔热材料的推广应用提供参考。方法 基于溶胶-凝胶法与超临界干燥工艺制备了二氧化硅气凝胶及其复合材料,开展了材料的长时热处理实验及性能（密度、热导率、压缩强度）、结构（孔径分布、骨架形貌）的表征,分析了材料在长时高温环境中的变化趋势和规律。结果 在长时高温环境中,当环境温度低于二氧化硅气凝胶复合材料耐受温度上限1 050 ℃时,材料性能在短时间内变化较为明显,之后随时间延长趋于稳定,主要原因是构成二氧化硅气凝胶骨架的纳米颗粒具有高表面活性,在高温环境中易于烧结而造成结构变化。纤维的引入能够有效抑制二氧化硅气凝胶的烧结,从而复合材料表现出比纯二氧化硅气凝胶相对更高的耐受温度,经1 000 ℃热处理480 h后的1 000 ℃热导率仅为0.071 W/(m·K)。适当的烧结能够使二氧化硅气凝胶骨架得到强化,经1 000 ℃热处理168 h后复合材料的压缩强度提升了将近1倍（98.9%）,同时其1 000 ℃热导率仅增大9.2%。结论 本文制备的二氧化硅气凝胶复合材料能够在长时1 000 ℃环境中保持低热导特性,有望作为长时高温隔热材料应用。
Abstract
The work aims to study the performance evolution patterns of the silica aerogel composite under long-term high-temperature environments to provide a reference for the application of silica aerogel composites as thermal insulation materials for prolonged use. The pure silica aerogel and its composite were prepared via the sol-gel method combined with supercritical drying technology. Long-term heat treatment experiments were conducted on the materials, along with characterizations of their properties (density, thermal conductivity, compressive strength) and structures (pore size distribution, skeleton morphology). The evolution trends and patterns of the materials under long-term high-temperature conditions were analyzed. In a long- term high-temperature environment, when the ambient temperature was below the upper tolerance limit of the silica aerogel composite, the properties changed more significantly over short periods, and then tended to stabilize with extended time. The primary reason was that the nanoparticles constituting the silica aerogel skeleton possessed high surface activity and were prone to sintering under high-temperature conditions, resulting in structural changes. The introduction of fibers could effectively inhibit the sintering of the pure silica aerogel, enabling the composite to exhibit a relatively higher temperature tolerance than pure silica aerogel. After heat treatment at 1 000 ℃ for 480 h, the thermal conductivity of the composite at 1 000 ℃ was only 0.071 W/(m·K). Moderate sintering could strengthen the silica aerogel skeleton, thereby enhancing the compressive strength of the composite to a certain extent. After heat treatment at 1 000 ℃ for 168 h, the compressive strength of the composite was nearly doubled (98.9%), while its thermal conductivity at 1 000 ℃ only increased by 9.2%. The silica aerogel composite prepared in this study can maintain low thermal conductivity over prolonged periods at 1 000 ℃, showing promise for application as a long-term high-temperature thermal insulation.
关键词
二氧化硅气凝胶 /
隔热 /
长时高温环境 /
性能变化 /
热导率 /
烧结
Key words
silica aerogel /
thermal insulation /
long-term high-temperature environment /
performance evolution /
thermal conductivity /
sintering
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