Measuring radiative properties of silica aerogel composite from FTIR transmittance test using KBr as diluents
Measuring radiative properties of silica aerogel composite from FTIR transmittance test using KBr as diluents
复制标题
使用 KBr 作为稀释剂通过 FTIR 透射率测试测量二氧化硅气凝胶复合材料的辐射性能
DOI：
10.1016/j.expthermflusci.2017.10.010
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发表时间：
2018-02
影响因子：
3.2
通讯作者：
Yueming Li
中科院分区：
文献类型：
--
作者：
Hu Zhang;Xian Wang;Yueming Li
光谱消光系数、Rosseland平均消光系数和辐射导热系数等辐射性能是多孔隔热材料的关键特性。对于含纤维和遮光剂的二氧化硅气凝胶复合材料，通过实验很难准确测定其光谱消光系数和辐射导热系数。这种复合材料的光谱消光系数通常通过使用KBr作为稀释剂的透射率测试来确定。传统的模型在从透过率测量确定消光系数时有几个假设：稀释剂被假设为纯透明介质，压制的小球没有反射，以及在计算复合材料的有效厚度时复合粉末与KBr串联。因此，传统模型在这些假设下确定的消光系数将导致辐射导热系数预测的不确定性。为了克服这一缺点，提出了考虑KBr稀释剂吸收、样品反射和样品粉末在稀释剂中随机分布的改进模型。采用压片法制备了组分和浓度相同但厚度不同的KBr稀释SiO2气凝胶复合颗粒。通过傅里叶变换红外光谱（FTIR）测量压制颗粒的透射率。光谱消光系数的计算与建议的模型从测量的透射率。根据不同模型测定的Rosseland平均消光系数，计算了SiO2气凝胶复合材料的辐射导热系数。本研究发现，所发展的模型可以消除传统模型的假设。
Radiative properties such as spectral extinction coefficient, Rosseland mean extinction coefficient and radiative thermal conductivity are the key features of porous insulation materials. For silica aerogel composites with fiber and opacifier, it is difficult to determine the spectral extinction coefficient and radiative thermal conductivity via experiment accurately. The spectral extinction coefficient of such composites is usually determined by a transmittance test using KBr as a diluent. The traditional model has several assumptions on determining the extinction coefficient from the transmittance measurement: the diluents are assumed as a pure transparent medium, the pressed pellet has no reflection, and the composite powder is in series with the KBr when calculating the effective thickness of the composite. Thus, the extinction coefficient determined from the traditional model with these assumptions will result in some uncertainty on predicting the radiative thermal conductivity. To overcome the drawbacks, improved models are proposed by considering the absorption of KBr diluents, sample reflection and random distribution of sample powder in the diluents. KBr diluted silica aerogel composite pellets with the same constituents and concentrations but different thicknesses are prepared using the pressed pellets method. The transmittances of the pressed pellets are measured by Fourier transform infrared spectroscopy (FTIR). The spectral extinction coefficients are calculated from the measured transmittances with proposed models. The radiative thermal conductivity of silica aerogel composite is calculated with the measured Rosseland mean extinction coefficient determined from different models. This study found that the developed models could eliminate the assumptions of the traditional model.
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影响因子：
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作者：
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