Optical porosimetry of weakly absorbing porous materials
Porosimétrie optique des matériaux poreux faiblement absorbants
Libois, Quentin ; Lévesque-Desrosiers, Félix ; Lambert-Girard, Simon ; Thibault, Simon ; Domine, Florent
The physical porosity Φ of a porous material determines most of its properties. Although the optical porosity Φopt can be measured, relating this quantity to Φ remains a challenge. Here we derive relationships between the optical porosity, the effective refractive index 𝑛eff and the physical porosity of weakly absorbing porous media. It introduces the absorption enhancement parameter 𝐵, which quantifies the asymmetry of photon path lengths between the solid material and the pores and can be derived from the absorption coefficient 𝜇𝑎 of the material. Hence Φ can be derived from combined measurements of 𝑛eff and 𝜇𝑎. The theory is validated against laboratory measurements and numerical experiments, thus solving a long-standing issue in optical porosimetry. This suggests that optical measurements can be used to estimate physical porosity with an accuracy better than 10%.</p>
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