Gas transport in porous Vycor glass subjected to gradual pore narrowing

Fernandes, Neil E.; Gavalas, George R.

doi:10.1016/s0009-2509(97)00399-0

Cited by 13 publications

(10 citation statements)

References 9 publications

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“…The factor K approximately cancels the path curvature effect in the case of nitrogen and overwhelms it in the case of isobutane. The results for isobutane are in accord with measurements of isobutane permeation in untreated Vycor at 450 K . The results for nitrogen are also in accord with the experimental results in (17) but not with previous measurements 21 showing “surface flows” of nitrogen in untreated Vycor at temperatures as low as 270 K. This discrepancy may be due to a too weak intrapore potential adopted in the simulations or to geometric effects.…”

Section: Resultssupporting

confidence: 85%

“…The scattering center concentration is taken to be equal to the concentration of silanols on the surface of Vycor glass (with vicinal and geminal pairs being counted as one). From previous experimental measurements, 2.3 nm -2 is a reasonable value for the silanol number . To avoid correlation effects, pore lengths of 1000 Å were used and periodic boundary conditions were imposed.…”

Section: Construction Of the Pore Surface And Intrapore Potentialmentioning

confidence: 99%

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Molecular Dynamics Simulations of Diffusion in Mesoporous Glass

Fernandes

Gavalas

1999

Ind. Eng. Chem. Res.

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The effect of gas−solid intrapore potential and surface roughness on diffusion in a single capillary was investigated by molecular dynamics simulations. Calculations were carried out for nitrogen and isobutane under free molecular flow conditions in pores of diameter 4−14 Å at temperatures of 200−800 K. The gases were treated as Lennard-Jones atoms and the pore surface was taken as cylindrical, exerting a 9−3 potential. No energy transfer was considered between the gas and solid, but interaction with the roughened pore wall provided the scattering required for diffusive transport. Two effects of the gas−solid potential were examined in some detail. One is the enhanced intrapore gas concentration which increases the flux, and the other is the bending of the molecular trajectories which decreases the flux. In pores of radius 20 Å, both effects were significant for temperatures as high as 500 K and were enhanced as the temperature decreased. For nitrogen, the two effects partially canceled each other over the temperature range examined, resulting in a temperature dependence similar to that of Knudsen diffusion. For isobutane, the partitioning effect dominated the path curvature effect at temperatures as high as 500 K.

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Section: Resultssupporting

confidence: 85%

Section: Construction Of the Pore Surface And Intrapore Potentialmentioning

confidence: 99%

Molecular Dynamics Simulations of Diffusion in Mesoporous Glass

Fernandes

Gavalas

1999

Ind. Eng. Chem. Res.

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“…Other researchers have also demonstrated the transportation of gases through porous Vycor glass. 14–17 …”

Section: Resultsmentioning

confidence: 99%

Singlet Oxygen Delivery Through the Porous Cap of a Hollow-Core Fiber Optic Device

2009

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The development of the first photosensitizer/fiber optic device is reported. An oxygen-flowing fiber-capped configuration is used for the application of heterogeneous, spatially confined singlet oxygen delivery in aqueous media. This is a unique device, unlike other heterogeneous photosensitizers, in which local concentrations of singlet oxygen can be delivered via introduction and withdrawal of the fiber tip.

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“…4 nm. Eine Verringerung der Porengröße ist prinzipiell durch eine postsynthetische Modifizierung möglich [6]. Shelekhin et al [7] Aus den Ableitungen der erhaltenen Druckverläufe können der Fluss durch die Membran und die Permeabilität errechnet werden [9]: …”

Section: Einführungunclassified