Experimental and analytical analyses of the thermal conductivities and high-temperature characteristics of silica aerogels based on microstructures
Experimental and analytical analyses of the thermal conductivities and high-temperature characteristics of silica aerogels based on microstructures
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DOI：
10.1088/0022-3727/46/1/015304
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发表时间：
2013-01
期刊：
影响因子：
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通讯作者：
Jun-jie Zhao;Y. Duan;Xiao-dong Wang;B. Wang
中科院分区：
文献类型：
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作者：
Jun-jie Zhao;Y. Duan;Xiao-dong Wang;B. Wang
基于扫描电子显微镜、Brunauer-Emmett-Teller和比重瓶测量以及三维无规扩散限制的团簇-团簇聚集结构，提出了一种分析传热模型，用于计算二氧化硅气凝胶的温度依赖性微结构参数和热导率。该模型是一个纯预测模型，不需要实验拟合的经验参数，只需要四个实测结构参数作为输入参数。该模型可提供高温下的组织和热物理性能，为材料设计提供理论指导。结果表明，在300 ~ 1500 K温度范围内，气凝胶结构的热演化过程分为三个阶段。目前的分析模型是充分验证了实验数据。在以前的热传递模型中使用的恒定结构的假设被发现在较高的温度下会导致显着的错误，因为温度相关的结构变形显着增加气凝胶的热导率。高温热处理后的二氧化硅气凝胶的导热系数和总导热系数比未热处理的气凝胶大得多。
An analytical heat transfer model based on scanning electron microscopy, Brunauer–Emmett–Teller and pycnometry measurements and a 3D random diffusion-limited cluster–cluster aggregation structure is proposed to calculate the temperature-dependent microstructural parameters and thermal conductivities of silica aerogels. This model is a pure prediction model, which does not need experimentally fitted empirical parameters and only needs four measured structural parameters as input parameters. This model can provide high-temperature microstructural and thermophysical properties as well as theoretical guidelines for material designs with optimum parameters. The results show that three stages occur during the thermal evolution processes of the aerogel structure with increasing temperature from 300 to 1500 K. The current analytical model is fully validated by experimental data. The constant structure assumptions used in previous heat transfer models are found to cause significant errors at higher temperatures as the temperature-dependent structure deformation significantly increases the aerogel thermal conductivity. The conductive and total thermal conductivities of silica aerogels after high-temperature heat treatments are much larger than those with no heat treatment.