Compressional stress effect on thermal conductivity of powdered materials: Measurements and their implication to lunar regolith
Compressional stress effect on thermal conductivity of powdered materials: Measurements and their implication to lunar regolith
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压缩应力对粉末材料热导率的影响：测量及其对月球风化层的影响
DOI：
10.1016/j.icarus.2015.12.012
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发表时间：
2016
期刊：
影响因子：
3.2
通讯作者：
Satoshi Tanaka
中科院分区：
文献类型：
--
作者：
Nagoya Sakatani;Kazunori Ogawa;Yu-ichi Iijima;Masahiko Arakawa;Satoshi Tanaka
真空条件下粉末材料的热导率是行星科学中一个有价值的物理参数。我们报告了90-106 μm和710-1000 μm的玻璃珠和月壤模拟物的热导率测量结果，使用两种不同的实验装置，分别改变压缩应力和温度。我们发现，随着压应力的增加，热导率增加，例如，从0.003到0.008 W m-1 K-1的玻璃珠直径为90-106 μm的压应力小于20 kPa。这种热导率的增加归因于颗粒之间的接触面积由于它们的弹性变形而扩大。热导率也随温度的升高而增加，这主要代表了颗粒间辐射热传导的增强。从在第一个实验中获得的有效热导率中估计的辐射电导率的减少产生固体电导率（通过颗粒间接触的传导贡献）和压缩应力之间的关系。我们发现，固体电导率是成正比的约1/3功率的压缩应力的玻璃珠样品，而风化模拟物显示出一个较弱的指数比玻璃珠。我们开发了一个半经验表达式的月壤的热导率使用我们的月壤模拟数据。该模型使我们能够估计月球表面下热导率的垂直分布。我们的模型提供了一个检查的密度和压缩应力的导热系数在阿波罗15号和17号热流实验中观察到的原位测量。
Thermal conductivity of powdered materials under vacuum conditions is a valuable physical parameter in the context of planetary sciences. We report results of thermal conductivity measurements of 90–106 μm and 710–1000 μm glass beads, and lunar regolith simulant using two different experimental setups for varying the compressional stress and the temperature, respectively. We found the thermal conductivity increase with the compressional stress, for example, from 0.003 to 0.008 W m−1K−1for the glass beads of 90–106 μm in diameter at the compressional stress less than 20 kPa. This increase of the thermal conductivity is attributed the areal enlargement of the contacts between particles due to their elastic deformation. The thermal conductivity increased also with temperature, which primarily represented enhancement of the radiative heat conduction between particles. Reduction of the estimated radiative conductivity from the effective thermal conductivity obtained in the first experiment yields the relation between the solid conductivity (conductive contribution through inter-particle contacts) and the compressional stress. We found that the solid conductivity is proportional to approximately 1/3 power of the compressional stress for the glass beads samples, while the regolith simulant showed a weaker exponent than that of the glass beads. We developed a semi-empirical expression of the thermal conductivity of the lunar regolith using our data on the lunar regolith simulant. This model enabled us to estimate a vertical distribution of the lunar subsurface thermal conductivity. Our model provides an examination for the density and compressional stress relationships to thermal conductivity observed in the in-situ measurements in Apollo 15 and 17 Heat Flow Experiments.