Search results for "Porous medium"
showing 4 items of 164 documents
Acoustic spectroscopy of aerogel precursors
2007
We investigate the acoustical properties of silica gels, which are precursors in the aerogel production process. These gels exhibit a strong “ringing gel” behavior, that is they emit a characteristic sound if one knocks against the container. We study this sound emission with a very simple spectroscopic technique and observe resonances which are characteristic for natural frequencies of a cylindrical body. From a fit of the experimental frequency positions to calculated values, we determine a sound velocity of c T = 4 m/s for a gel sample with porosity φ = 97.5%. This low sound velocity can only be interpreted as the transverse sound mode predicted by Biot’s theory for sound propagation in …
Numerical investigation on water exchange of shale samples
2020
Interest in the hydraulic and mechanical characterization of shales has grown in recent years, because of their application in the context of energy geotechnics. In the frame of nuclear waste disposal shales are considered as host formations for the placements of nuclear waste at high depths. In the frame of hydrocarbon production they are considered as unconventional reservoirs, from which extracting natural gas. Understanding how fluids flow through shales is then a key aspect for both fields of application. This paper focuses on the analysis of the transport of water vapour through laboratory samples. After reviewing the balance and flow laws that govern the transport of fluid in unsatur…
COMPUTATIONAL HOMOGENIZATION OF POLYCRYSTALLINE MATERIALS WITH PORES: A THREE-DIMENSIONAL GRAIN BOUNDARY FORMULATION
2012
In this study, the influence of porosity on the elastic effective properties of polycrystalline materials is investigated using a 3D grain boundary micro mechanical model. The volume fraction of pores, their size and distribution can be varied to better simulate the response of real porous materials. The formulation is built on a boundary integral representation of the elastic problem for the grains, which are modeled as 3D linearly elastic orthotropic domains with arbitrary spatial orientation. The artificial polycrystalline morphology is represented using 3D Voronoi Tessellations. The formulation is expressed in terms of intergranular fields, namely displacements and tractions that play …
Sponge‐Like Behaviour in Isoreticular Cu(Gly‐His‐X) Peptide‐Based Porous Materials
2015
We report two isoreticular 3D peptide-based porous frameworks formed by coordination of the tripeptides Gly-L-His-Gly and Gly-L-His-L-Lys to Cu(II) which display sponge-like behaviour. These porous materials undergo structural collapse upon evacuation that can be reversed by exposure to water vapour, which permits recovery of the original open channel structure. This is further confirmed by sorption studies that reveal that both solids exhibit selective sorption of H2 O while CO2 adsorption does not result in recovery of the original structures. We also show how the pendant aliphatic amine chains, present in the framework from the introduction of the lysine amino acid in the peptidic backbo…