Heshmat Barmak, Andrews Gordon Moseley, Naranjo-Montoya Oscar A, Castro-Camus Enrique, Ciceri Davide, Sanchez Albert Redo, Allanore Antoine, Kmetz Anthony A, Eichmann Shannon L, Poitzsch Martin E, Raskar Ramesh
Opt Express. 2017 Oct 30;25(22):27370-27385. doi: 10.1364/OE.25.027370.
We use terahertz transmission through limestone sedimentary rock samples to assess the macro and micro porosity. We exploit the notable water absorption in the terahertz spectrum to interact with the pores that are two orders of magnitude smaller (<1μm) than the terahertz wavelength. Terahertz water sensitivity provides us with the dehydration profile of the rock samples. The results show that there is a linear correlation between such a profile and the ratio of micro to macro porosity of the rock. Furthermore, this study estimates the absolute value of total porosity based on optical diffusion theory. We compare our results with that of mercury injection capillary pressure as a benchmark to confirm our analytic framework. The porosimetry method presented here sets a foundation for a new generation of less invasive porosimetry methods with higher penetration depth based on lower frequency (f<10THz) scattering and absorption. The technique has applications in geological studies and in other industries without the need for hazardous mercury or ionizing radiation.
我们利用太赫兹波透过石灰岩沉积岩样品来评估其宏观和微观孔隙率。我们利用太赫兹光谱中显著的水吸收特性，与比太赫兹波长小两个数量级（<1μm）的孔隙相互作用。太赫兹对水的敏感性为我们提供了岩石样品的脱水情况。结果表明，这种情况与岩石微观孔隙率和宏观孔隙率的比值之间存在线性关系。此外，本研究基于光扩散理论估算了总孔隙率的绝对值。我们将结果与压汞毛细管压力法的结果进行比较，以此作为基准来验证我们的分析框架。这里提出的孔隙率测量方法为新一代基于低频（f<10THz）散射和吸收、具有更高穿透深度的侵入性较小的孔隙率测量方法奠定了基础。该技术在地质研究和其他行业中都有应用，无需使用危险的汞或电离辐射。
