Ultrasonic study of water adsorbed in nanoporous glasses

Ogbebor, Jason; Valenza, John J.; Ravikovitch, Peter I.; Karunarathne, Ashoka; Muraro, Giovanni; Lebedev, Maxim; Gurevich, Boris; Khalizov, Alexei F.; Gor, Gennady Y.

doi:10.1103/physreve.108.024802

Cited by 6 publications

(3 citation statements)

References 69 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Starting from this simple expression, we derive a microscopic model by accounting for the impact of the n a adsorbed molecules on the speed of sound v ( n a ) and phonon lifetime τ( n a ). For the speed of sound, as a first-order approximation, we assume that the coefficients of the stiffness matrix C and the zeolite volume are independent of n a v ( n normala ) = C / ρ ∼ v ( 0 ) / 1 + n a m / m β where v 0 is the speed of sound of empty zeolite, m is the mass of the methane molecule, and m β is the mass of empty zeolite (for more details on the speed of sound in nanoconfined fluids, the reader can refer to the experimental and simulation results of coupled adsorption-ultrasonic measurements , ). For the phonon lifetime, as illustrated in Figure a, we write a simple Matthiessen’s rule in which we consider two relaxation processes that are uncoupled and, hence, independent of each other: (1) phonon–phonon scattering within the solid network and (2) phonon scattering at the interface due to the collision with a fluid molecule.…”

Section: Resultsmentioning

confidence: 99%

“…where v 0 is the speed of sound of empty zeolite, m is the mass of the methane molecule, and m β is the mass of empty zeolite (for more details on the speed of sound in nanoconfined fluids, the reader can refer to the experimental and simulation results of coupled adsorption-ultrasonic measurements 65,66 ). For the phonon lifetime, as illustrated in Figure 5a, we write a simple Matthiessen's rule in which we consider two relaxation processes that are uncoupled and, hence, independent of each other: (1) phonon−phonon scattering within the solid network and ( 2) phonon scattering at the interface due to the collision with a fluid molecule.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Thermal Conductivity of a Fluid-Filled Nanoporous Material: Underlying Molecular Mechanisms and the Rattle Effect

Ferreira de Souza,

Picard,

Franco

et al. 2024

J. Phys. Chem. B

View full text Add to dashboard Cite

Nanoporous materials are central to the energy and environmental crisis, with key applications in adsorption, separation, and catalysis. While confinement and surface effects on fluids severely confined in their porosity are well documented, the thermal behavior of nanoporous solids subjected to fluid adsorption remains puzzling in many aspects. With striking phenomena such as the so-called rattle effect, through which fluid/solid collisions decrease the overall thermal conductivity, the solid thermal conductivity and, more generally, heat transfer and dispersion in these complex systems challenge classical approaches (e.g., mixing rules including effective medium approaches fail to capture such effects as shown here). In particular, a robust molecular framework to describe the crossover between the decrease in thermal conductivity through the rattle effect in very narrow pores and the increase in thermal conductivity when replacing vacuum with a fluid phase in larger pores is still missing. Here, using a prototypical model of fluid-filled nanoporous materials (a Lennard-Jones phase confined in an all-silica zeolite), we perform a molecular simulation study to shed light on the parameters that govern the rattle effect in nanoporous solids. First, by varying the fluid/fluid, fluid/solid, and solid/solid interaction strengths as well as the fluid number density and mass density, we unravel the ingredients that lead to the essential coupling between fluid adsorption and phonon transport. Second, despite this complex interplay, inspired by pioneering molecular approaches on the rattle effect, we show that all data obey a simple statistical physics model that relies on the change in the speed of sound due to the fluid adsorbed density and the decrease in phonon lifetime due to scattering by fluid molecules. This framework, which provides a simple formalism to rationalize the thermal behavior of this class of solid/fluid composites, points to a decrease in thermal conductivity upon fluid confinement (up to 30% in some cases). Such an effect paves the way for the design of novel applications involving fluids in interaction with nanoporous materials.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Thermal Conductivity of a Fluid-Filled Nanoporous Material: Underlying Molecular Mechanisms and the Rattle Effect

Ferreira de Souza,

Picard,

Franco

et al. 2024

J. Phys. Chem. B

View full text Add to dashboard Cite

show abstract

“…For stimuli-responsive applications, elastic properties of materials are the key. However, elastic properties of nanoporous materials are challenging to quantify even for relatively simple structures . AID can serve as a method to measure the elastic constants of nanoporous samples. ,− If AID and EID are performed on the same samples, the elastic constants can be derived from AID to help eliminating the number of unknowns in the EID experiments.…”

Section: Moving Forwardmentioning

confidence: 99%

What Drives Deformation of Smart Nanoporous Materials During Adsorption and Electrosorption?

Gor,

Kolesnikov

2024

Langmuir

Self Cite

View full text Add to dashboard Cite

Nanoporous solids have high surface area, so processes at the surface affect the sample as a whole. When guest species adsorb in nanopores, be they molecules adsorbing from the gas phase, or ions adsorbing from solution, they cause material deformation. While often undesired, adsorption-or electrosorption-induced deformation provides a potential for nanoporous materials to be used as actuators. Progress in this direction requires understanding the mechanisms of adsorption-or electrosorption-induced deformation. These two processes are rarely discussed together, and this Perspective aims to fill this gap to some extent, focusing on driving forces for both processes. Typically the main driving force for both is the solvation (disjoining) pressure, acting normally to the pore walls. However, in some cases, solvation pressure is not sufficient to describe the effects even qualitatively. We highlight examples in which the surface stress acting along the solid surface is an additional driving force for deformation.

show abstract

Evaluating the Pressure Dependence of the Longitudinal Modulus of an Adsorbate in Nanopores Using Ultrasound: A Novel Procedure Taking the Effect of Emptying Pore Ends into Account

Schappert,

Pelster

2024

J. Phys. Chem. C

View full text Add to dashboard Cite

The determination of the elastic properties of nanoconfined substances from measured effective quantities is a challenging task. In this article, we explore the possibilities to determine an adsorbate's elastic modulus and its pressure dependence using ultrasound. As a model system, we study the isothermal adsorption and desorption of liquid argon in nanoporous glass with an average pore diameter of d P = 25.6 nm. The longitudinal modulus of an adsorbate, β ads , is usually determined by means of an effective medium equation using the average modulus of the filled porous system, c, with c l being the measured velocity of longitudinal ultrasonic pulses propagating through the sample and ρ the average density. However, in the so-called plateau region of a sorption isotherm, curved liquid−vapor menisci and empty pore ends are present at the outer surface of the sample, i.e., the filling of the pores and the density vary within the sample. With the analysis of our ultrasonic measurements, we show that the determination of the pressure dependence of an adsorbate's modulus requires the careful consideration of the accurate geometrical arrangement of the adsorbate in the volume, where the ultrasonic pulses propagate. Thereby, we have developed a method for the correct determination of the pressure dependence of an adsorbate's modulus that can be applied to other porous systems. Thus, our findings will have an immediate impact on the interpretation and analysis of ultrasonic studies on elastic properties of nanoconfined materials.

show abstract

Ultrasonic study of water adsorbed in nanoporous glasses

Cited by 6 publications

References 69 publications

Thermal Conductivity of a Fluid-Filled Nanoporous Material: Underlying Molecular Mechanisms and the Rattle Effect

Thermal Conductivity of a Fluid-Filled Nanoporous Material: Underlying Molecular Mechanisms and the Rattle Effect

What Drives Deformation of Smart Nanoporous Materials During Adsorption and Electrosorption?

Evaluating the Pressure Dependence of the Longitudinal Modulus of an Adsorbate in Nanopores Using Ultrasound: A Novel Procedure Taking the Effect of Emptying Pore Ends into Account

Contact Info

Product

Resources

About