Pore tortuosity and diffusivity of porous composite RVEs composed of random sequential additions of polydisperse superellipsoidal particles

Abstract

Understanding the effects of particle configurations on their surrounding pore tortuosity and the diffusivity of porous composites is very critical to the durability evaluations of fuel cell electrodes, filtration membranes, polymer foams, ceramics, and powder beds. It has been a key but unresolved issue how to accurately probe the tortuosity of pore space interstitial to non-spherical particles and its influence on the diffusivity of porous composites. This work proposes two powerful numerical strategies that one is a direction-guided rapidly exploring random tree (DGRRT) method and another is a dual-probability-Brownian motion (DP-BM) scheme, to respectively explore the nonlinear pore tortuosity and the effective diffusivity of porous composites, the representative volume element (RVE) of which is regarded as a two-phase composite composed of the random sequential addition (RSA) of superellipsoidal particles with polydispersity in size under periodic boundary conditions and their supplementary set as complex pore space at a microscopic level. Both numerical models are validated to be capable of accurately obtaining the pore tortuosity and the effective diffusivity of porous composites by comparing with extensive theoretical data reported in the literature, which can be viewed as general strategies suitable for detecting the pore tortuosity and diffusivity-like transport properties of porous composites. Moreover, we utilize the proposed strategies to investigate the effects of superellipsoidal particle shapes, volume fraction, maximum particle size, and particle size distribution, on the pore tortuosity and the effective diffusivity of porous composites. The derived results show the affinity to particle component-pore tortuosity-diffusivity of porous composites, which can provide sound guidance for the design and optimization of composites.