Stresses and strains in adsorbent–adsorbate systems. VI

Abstract

The effects of some changes of ambients on the dimensions of an activated carbon rod are presented. The emphasis is on the regions where anomalous contractions occur. It is suggested that dimensional changes can be used to estimate adsorption potentials of liquids of very low vapor pressures where adsorption isotherms cannot be measured by the usual methods.

Adsorption-Induced Expansion of Graphene Oxide Frameworks: Observation by in Situ Neutron Diffraction

“…The expansion of carbon-based materials upon molecular adsorption has been known for many years. − Most thoroughly studied has been adsorption from the liquid state where the expansions observed are the largest. − However, pore dynamics in response to supercritical adsorption has been subjected to much less experimental investigation. It is desirable to address this situation on two accounts.…”

“…An adsorbent response to the adsorption of a van der Waals gas has been observed for a few carbon-based materials including activated carbon and carbon xerogels. The most common experimental technique for studying adsorption-induced deformation has been dilatometry. ,,− We note that dilatometry measures the macroscopic length change of a bulk sample with a resolution typically on the order of micrometers and sample lengths on the order of centimeters. Balzer et al , used dilatometry to study the deformation of carbon xerogels caused by adsorption of gases N 2 , Ar, CO 2 , and H 2 O under subcritical conditions.…”

Deformation of Microporous Carbons during N2, Ar, and CO2 Adsorption: Insight from the Density Functional Theory

“…In this work we focus on the origin of adsorption-induced deformation of microporous carbons. Typically microporous materials, such as carbons or zeolites, exhibit a nonmonotonic adsorption-induced deformation: they contract at low stages of micropore filling and switch to expansion as adsorption progresses. − The extent of observed contraction and expansion depends on the structure of the adsorbent, , the adsorptive applied, ,,,− and the temperature. ,,, The first model for adsorption-induced deformation of microporous materials was proposed by Bangham, who considered the energy change of the adsorbate–adsorbent interface to be the sole source of stress within the porous structure . This concept was later implemented into the framework of Biot’s poromechanics by the use of the Gibbs adsorption equation. ,, However, the fundamental issue of this approach is that adsorption leads to a reduction of the interfacial energy, and thereby only expansion should be observed, in clear contradiction with experimental findings.…”

Monte Carlo Simulation of Adsorption-Induced Deformation in Finite Graphitic Slit Pores

“…An early experimental investigation by Meehan in 1927 reported the expansion of charcoal on adsorption of carbon dioxide . Later the expansion of charcoal upon exposure to water vapor, ammonia, alcohols, and other gases was studied by Bangham and co-workers, − and the deformation of carbon rods was investigated by Flood and co-workers in the 50s and 60s, − who found evidence of contraction at low pressures. Adsorption-induced deformation was also investigated for materials other than carbon, − and both expansion and contraction were recorded.…”