dc.contributor.author	Seo, Dongjin	en
dc.contributor.committeechair	Ducker, William A.	en
dc.contributor.committeemember	Martin, Stephen Michael	en
dc.contributor.committeemember	Paul, Mark R.	en
dc.contributor.committeemember	Davis, Richey M.	en
dc.contributor.department	Chemical Engineering	en
dc.date.accessioned	2014-10-31T08:00:47Z	en
dc.date.available	2014-10-31T08:00:47Z	en
dc.date.issued	2014-10-30	en
dc.description.abstract	This thesis describes measurements of the gas-solid flow boundary condition at moderate Knudsen number, i.e., where the dimensions of the flow are similar to the mean free path, and thus partial slip is expected. This regime has become more important with increased focus on nano-scale devices, but there is currently no consensus on how the slip length should vary for different solids and gases, or whether it can be controlled. In this thesis, I describe unambiguous measurements showing that partial slip occurs, that the slip length depends both on gas and solid, and that the slip length can be altered in situ. The slip length is determined from analysis of the vibration of a small sphere adjacent to a solid. I also describe applications of these findings both to the separation of gases, and to inhalants. The effect of water films, gas species, organic films, and electric fields on gas flow was studied. Water films had a large, but complex effect. On bare hydrophobilic glass, the tangential momentum accommodation coefficient (TMAC) for nitrogen on hydroxyl-terminated silica changed from 0.25 to 0.88 when the humidity changed from 0 to 98 %. On hydrophobized glass, TMAC changed from 0.20 to 0.56 in the same range. The effect of the gas on TMAC was measured for five different gases (helium, nitrogen, argon, carbon dioxide, hexafluoride sulfur) on octadecyltrichlorosilane-coated glass surfaces. A lower TMAC occurred for greater molar mass, and this trend was explained using a simple model representing both the gas and the monolayer by spheres. The existence of this gas-dependent difference in TMAC suggests that gases can be separated based on their collisions with surfaces. Methods for controlling the flow boundary condition were also developed by adsorbing monolayers on the solid, and altering the monolayers in situ. Both temperature and electric fields altered the boundary condition, and these changes were attributed to changes in the surface roughness. The effect of roughness was modeled with grooved surfaces. Possible applications of this effect of roughness include changing the flow of aerosol droplets for deeper delivery of therapeutic drugs into the lung.	en
dc.description.degree	Ph. D.	en
dc.format.medium	ETD	en
dc.identifier.other	vt_gsexam:3774	en
dc.identifier.uri	http://hdl.handle.net/10919/50650	en
dc.publisher	Virginia Tech	en
dc.rights	In Copyright	en
dc.rights.uri	http://rightsstatements.org/vocab/InC/1.0/	en
dc.subject	gas	en
dc.subject	slip flow	en
dc.subject	accommodation coefficient	en
dc.subject	boundary condition	en
dc.subject	lubrication	en
dc.title	Measurement and Control of Slip-Flow Boundary Conditions at Solid-Gas Interfaces	en
dc.type	Dissertation	en
thesis.degree.discipline	Chemical Engineering	en
thesis.degree.grantor	Virginia Polytechnic Institute and State University	en
thesis.degree.level	doctoral	en
thesis.degree.name	Ph. D.	en

Measurement and Control of Slip-Flow Boundary Conditions at Solid-Gas Interfaces

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