Lattice Boltzmann simulations on the role of channel structure for reactive capillary infiltration

Abstract

It is widely recognized that the structure of porous media is of relevance for a variety of mechanical and physical phenomena. The focus of the present work is on capillarity, a pore-scale process occurring at the micron scale. We attempt to characterize the influence of pore shape for capillary infiltration by means of Lattice Boltzmann simulations in 2D with reactive boundaries leading to surface growth and ultimately to pore closure. The systems under investigation consist of single channels with different simplified morphologies: namely, periodic profiles with sinusoidal, step-shaped and zigzag walls, as well as constrictions and expansions with rectangular, convex and concave steps. This is a useful way to break the complexity of typical porous media down into basic structures. The simulations show that the minimum radius alone fails to properly characterize the infiltration dynamics. The structure of the channels emerges as the dominant property controlling the process. A factor responsible for this behavior is identified as being the occurrence of the pinning of the contact line. It turns out that the optimal configuration for the pore structure arises from the packing of large particles with round shapes. In this case, the probability of having wide and straight flow paths is higher. Faceted surfaces with sharp edges should be avoided because of the phenomenon of pinning near narrow-to-wide parts. This study is motivated by the infiltration of molten metals into carbon preforms. This is a manufacturing technique for ceramic components devised for advanced applications. Guidelines for experimental work are discussed.

Surface growth for molten silicon infiltration into carbon millimeter-sized channels: Lattice–Boltzmann simulations, experiments and models

“…The system of a single channel has also the advantage to ease the comparison with simulations in order to improve the description of the surface reaction [31,32]. Dimensionless numbers are introduced with the aim to assess the accuracy of simulations involving surface growth.…”

“…In any case, it should be kept in mind that multiphase models overestimate the experimental density ratio between the gas and liquid phases. Previous works addressed the case of linear infiltration for single channels [31,32].…”

Reactive silicon infiltration of carbon bonded preforms embedded in powder field modifiers heated by microwaves

“…It was even demonstrated that, without chemical reaction, infiltration would not occur [23]. On the other hand the formation of SiC on the capillary walls slows down or even blocks silicon infiltration [22][23][24][25]. Further work needs to be performed on calibrated preforms with a narrow and repeatable pore size range in order to correlate the final material's microstructure with relevant control parameters in MW heating.…”

Wetting and Navier-Stokes Equation — The Manufacture of Composite Materials

“…It is probable that in the first stage of the process, infiltration is controlled by the reaction at the triple line, and after the SiC interface has been formed, the viscous flow becomes the controlling process. A completely different approach to the process of infiltration is performed by Sergi et al [67,68], in which they use Lattice-Bolztman models to describe infiltration in a single capillary and predict that infiltration distance is proportional to time when considering pore narrowing of the capillary due to the reaction. However, their predictions have not been validated experimentally up to date.…”