Mesostructural stipulation of properties of porous materials. I. Pore-structure analysis of porous materials

Abstract

Procedural features of the mesostructural analysis of porous materials are established. It is shown that the experimental pore size is a function of research methods. The anisotropy of the macroporous system in biporous materials is determined. A mercury porometric method is developed for determining the effective porosity needed to evaluate the permeability factor.Keywords: biporous material, pore size analysis, macroporous structure anisotropy, mercury porosimetry.Increasing attention has been focused on high-porous materials in recent years [1][2][3][4][5]. New techniques are developed, for example, such as the formation of foamed and cellular materials. In addition, metal, ceramic, and polymer powders, and fibers and meshes are used to produce high-porous materials. Among these materials, of interest is the process of producing high-porous powder materials using pore-forming agents. The papers [4,5] inform of such materials, but there is practically no research data on their quite complex porous structure determined by different factors: size and content of each component, composition of the starting powder mixture and pore-forming additive, compaction pressure, volume shrinkage in sintering, etc.When the pore-forming agent is removed, these materials represent a system of macro-and micropores [6,7]. In terms of structural hierarchy [8], macropores form mesostructure and micropores submesostructure. We call the relative volume of macropores in the material macroporosity and relative volume of micropores in local volumes between the macropores microporosity.The macroporosity θ macr and size of large pores are determined by the number and size of pore-forming particles. The microporosity θ micr and size of micropores are determined by the size of powder particles (metal in our case) and compaction pressure of metal and pore-forming powder mixtures.Geometrical parameters of the porous structure are pore sizes and size distribution, structural anisotropy, matricity, tortuosity factor, etc. Note that the pore size distribution governs the research of pore space geometry.Assessment of these characteristics should take into account the uncertainty of the pore size and pore channel size, especially for high-porous materials made of nonspherical powders when there are pores of uncertain and random shape depending on numerous factors that are difficult to incorporate, which we particularly mentioned above for biporous materials.

Electrode Engineering for Electrochemical CO2 Reduction

“…In that case, the side reaction, the hydrogen evolution reaction (HER), is more favored. Hence, wettability and porosity are indispensable factors to be considered when optimizing the GDE structure. − …”