Elastic Response of Mesoporous Silicon to Capillary Pressures in the Pores

TL;DR

This study investigates how water-induced capillary pressures deform mesoporous silicon membranes, combining simulations, analytical modeling, and experiments to relate pore-load modulus to porosity and elastic properties, enabling elastic constant measurements.

Contribution

The paper introduces an analytical model linking pore-load modulus to porosity and elastic properties, validated by FEM simulations and experiments, applicable to similar mesoporous materials.

Findings

Pore-load modulus weakly depends on pore arrangement.

Analytical model accurately predicts pore-load modulus.

Young's modulus of pore walls is slightly lower than bulk silicon.

Abstract

We study water adsorption-induced deformation of a monolithic, mesoporous silicon membrane traversed by independent channels of $\sim$8 nm diameter. We focus on the elastic constant associated with the Laplace pressure-induced deformation of the membrane upon capillary condensation, i.e. the pore-load modulus. We perform finite-element method (FEM) simulations of the adsorption-induced deformation of hexagonal and square lattices of cylindrical pores representing the membrane. We find that the pore-load modulus weakly depends on the geometrical arrangement of pores, and can be expressed as a function of porosity. We propose an analytical model which relates the pore-load modulus to the porosity and to the elastic properties of bulk silicon (Young's modulus and Poisson's ratio), and provides an excellent agreement with FEM results. We find good agreement between our experimental data and the predictions of the analytical model, with the Young's modulus of the pore walls slightly lower than the bulk value. This model is applicable to a large class of materials with morphologies similar to mesoporous silicon. Moreover, our findings suggest that liquid condensation experiments allow one to elegantly access the elastic constants of a mesoporous medium.