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You searched for +publisher:"University of Texas – Austin" +contributor:("Haglund, John S."). Showing records 1 – 2 of 2 total matches.

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1. Ponkala, Mikko Juha Viljami. Humidity effects on hygroscopic particles deposited on HEPA filters and silicon wafer surfaces.

Degree: MSin Engineering, Mechanical Engineering, 2012, University of Texas – Austin

Semiconductor wafer manufacturing facilities (fab) must maintain extremely clean air environments to minimize the number of wafers scrapped due to contamination which would result in reduced yields. The fab air is cleaned bypassing it through either HEPA or ULPA filters. A number of airborne fab contaminants may be hygroscopic causing them to exist as a solid or a liquid when in equilibrium with their environment's relative humidity. The effect of relative humidity on such contaminants is poorly documented whether they were to be captured in a filter or deposited on a wafer. The work presented here experimentally characterizes NaCl evolution within HEPA filters when exposed to humidity fluctuations and the effect of humidity on NH4Cl corrosiveness when deposited on cobalt coated wafers with a TiN layer. Successive deliquescence and efflorescence fluctuations were imposed on particles captured on a glass fiber HEPA filter. Scanning Electron Microscopy (SEM) and Environmental SEM (ESEM) studies of the filters showed that the NaCl, under humidity excursions, did not penetrate deep into the filter but deliquesced and effloresced near the top surface of the filter. Pressure drop measurements for filters containing NaCl particles showed differences in pressure drop associated with relative humidity changes. These pressure drop changes suggested some redistribution particle properties. When exposed to a relative humidity of 20%, the NH4Cl particles did not corrode the cobalt wafer beyond the location of the initial deposit. At 61% relative humidity, the surrounding areas of the particles were corroded with a solid artifact left at the original location. At 76% relative humidity the NH4Cl particles were observed to have deliquesced, which is below the expected deliquescence relative humidity. The corrosion of the cobalt wafer was most extensive when the NH4Cl particles had deliquesced. Advisors/Committee Members: Ezekoye, Ofodike A. (advisor), Haglund, John S (committee member).

Subjects/Keywords: HEPA; Filter; Hygroscopic; Deliquescence; Efflorescence; Wafer; Contaminant

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Ponkala, M. J. V. (2012). Humidity effects on hygroscopic particles deposited on HEPA filters and silicon wafer surfaces. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/20008

Chicago Manual of Style (16th Edition):

Ponkala, Mikko Juha Viljami. “Humidity effects on hygroscopic particles deposited on HEPA filters and silicon wafer surfaces.” 2012. Masters Thesis, University of Texas – Austin. Accessed March 04, 2021. http://hdl.handle.net/2152/20008.

MLA Handbook (7th Edition):

Ponkala, Mikko Juha Viljami. “Humidity effects on hygroscopic particles deposited on HEPA filters and silicon wafer surfaces.” 2012. Web. 04 Mar 2021.

Vancouver:

Ponkala MJV. Humidity effects on hygroscopic particles deposited on HEPA filters and silicon wafer surfaces. [Internet] [Masters thesis]. University of Texas – Austin; 2012. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/2152/20008.

Council of Science Editors:

Ponkala MJV. Humidity effects on hygroscopic particles deposited on HEPA filters and silicon wafer surfaces. [Masters Thesis]. University of Texas – Austin; 2012. Available from: http://hdl.handle.net/2152/20008


University of Texas – Austin

2. Hubbard, Joshua Allen, 1982-. Enhanced real-time bioaerosol detection : atmospheric dispersion modeling and characterization of a family of wetted-wall bioaerosol sampling cyclones.

Degree: PhD, Mechanical Engineering, 2009, University of Texas – Austin

This work is a multi-scale effort to confront the rapidly evolving threat of biological weapons attacks through improved bioaerosol surveillance, detection, and response capabilities. The effects of bioaerosol release characteristics, transport in the atmospheric surface layer, and implications for bioaerosol sampler design and real-time detection were studied to develop risk assessment and modeling tools to enhance our ability to respond to biological weapons attacks. A simple convection-diffusion-sedimentation model was formulated and used to simulate atmospheric bioaerosol dispersion. Model predictions suggest particles smaller than 60 micrometers in aerodynamic diameter (AD) are likely to be transported several kilometers from the source. A five fold increase in effective mass collection rate, a significant bioaerosol detection advantage, is projected for samplers designed to collect particles larger than the traditional limit of 10 micrometers AD when such particles are present in the source distribution. A family of dynamically scaled wetted-wall bioaerosol sampling cyclones (WWC) was studied to provide bioaerosol sampling capability under various threat scenarios. The effects of sampling environment, i.e. air conditions, and air flow rate on liquid recovery rate and response time were systematically studied. The discovery of a critical liquid input rate parameter enabled the description of all data with self-similar relationships. Empirical correlations were then integrated into system control algorithms to maintain microfluidic liquid output rates ideally suited for advanced biological detection technologies. Autonomous ambient air sampling with an output rate of 25 microliters per minute was achieved with open-loop control. This liquid output rate corresponds to a concentration rate on the order of 2,000,000, a substantial increase with respect to other commercially available bioaerosol samplers. Modeling of the WWC was performed to investigate the underlying physics of liquid recovery. The set of conservative equations governing multiphase heat and mass transfer within the WWC were formulated and solved numerically. Approximate solutions were derived for the special cases of adiabatic and isothermal conditions. The heat and mass transfer models were then used to supplement empirical correlations. The resulting semi-empirical models offer enhanced control over liquid concentration factor and further enable the WWC to be deployed as an autonomous bioaerosol sampler. Advisors/Committee Members: Haglund, John S. (advisor), Ezekoye, Ofodike A. (advisor), Hall, Matthew J. (committee member), Hidrovo, Carlos H. (committee member), Novoselac, Atila (committee member).

Subjects/Keywords: Bioaerosol sampling and detection; Atmospheric dispersion modeling; Coarse particulate transport; Wetted-wall bioaerosol sampling cyclone; Concentration factor; Numerical multiphase heat and mass transfer model

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Hubbard, Joshua Allen, 1. (2009). Enhanced real-time bioaerosol detection : atmospheric dispersion modeling and characterization of a family of wetted-wall bioaerosol sampling cyclones. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2009-08-287

Chicago Manual of Style (16th Edition):

Hubbard, Joshua Allen, 1982-. “Enhanced real-time bioaerosol detection : atmospheric dispersion modeling and characterization of a family of wetted-wall bioaerosol sampling cyclones.” 2009. Doctoral Dissertation, University of Texas – Austin. Accessed March 04, 2021. http://hdl.handle.net/2152/ETD-UT-2009-08-287.

MLA Handbook (7th Edition):

Hubbard, Joshua Allen, 1982-. “Enhanced real-time bioaerosol detection : atmospheric dispersion modeling and characterization of a family of wetted-wall bioaerosol sampling cyclones.” 2009. Web. 04 Mar 2021.

Vancouver:

Hubbard, Joshua Allen 1. Enhanced real-time bioaerosol detection : atmospheric dispersion modeling and characterization of a family of wetted-wall bioaerosol sampling cyclones. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2009. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/2152/ETD-UT-2009-08-287.

Council of Science Editors:

Hubbard, Joshua Allen 1. Enhanced real-time bioaerosol detection : atmospheric dispersion modeling and characterization of a family of wetted-wall bioaerosol sampling cyclones. [Doctoral Dissertation]. University of Texas – Austin; 2009. Available from: http://hdl.handle.net/2152/ETD-UT-2009-08-287

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