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You searched for +publisher:"Georgia Tech" +contributor:("Dr. David S. Sholl"). Showing records 1 – 3 of 3 total matches.

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1. Keita, Namory. Lattice model simulation of hydrogen effect on palladium gold alloys used as purification metal membranes.

Degree: MS, Chemical Engineering, 2012, Georgia Tech

Hydrogen fuel is seen as energy of the future. Hydrogen molecules (H₂) are mostly used in the petrochemical industry and ammonia production. Hydrogen molecules are produced in large majority by steam reforming of hydrocarbons (methane). However, the purification of hydrogen is still a major factor in the cost of producing hydrogen. The range of membranes is large with advantages and drawbacks of each type of membrane. Among those membranes, metal alloy membranes are widely used because of their selectivity, durability, and resistance to poisoning. In the past, it was assumed an alloy once formed would remain in its initial structure while hydrogen gas was permeating through. It has been shown experimentally that the presence of hydrogen in palladium gold metal alloys will change the structure of the alloy from a disordered to an ordered phase. Hydrogen isotherms at different temperatures were used to demonstrate the change in structure. This structural change resulted in an increase in solubility of hydrogen in the membrane. In this work, using NVT-Monte Carlo we calculated the effect of hydrogen on the structure and on the solubility of Pd₉₆Au₄ and Pd₈₅Au₁₅ alloys. The palladium gold alloy was used because it demonstrated high resistance to sulfur poisoning and similar or higher permeability seen in to pure Pd. The methods used do not require any experimental input except for the structure of the bulk crystal. The interstitial binding energies were calculated using a Cluster Expansion model derived previously by Semidey and Kang from plane wave Density Functional Theory. The metal atoms enthalpies of formation were calculated from a truncated version of the Cluster Expansion derived by Sluiter for fcc metal structures. We conclude that hydrogen presence in the metal membrane will change the membrane from a disordered to a Short Range Ordered structure. Advisors/Committee Members: Dr. David S. Sholl (Committee Chair), Dr. Carsten Sievers (Committee Member), Dr. Michael A. Filler (Committee Member).

Subjects/Keywords: Purification; Palladium gold alloys; Hydrogen; Metal membranes; Hydrogen as fuel; Alloys

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APA (6th Edition):

Keita, N. (2012). Lattice model simulation of hydrogen effect on palladium gold alloys used as purification metal membranes. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/44712

Chicago Manual of Style (16th Edition):

Keita, Namory. “Lattice model simulation of hydrogen effect on palladium gold alloys used as purification metal membranes.” 2012. Masters Thesis, Georgia Tech. Accessed April 16, 2021. http://hdl.handle.net/1853/44712.

MLA Handbook (7th Edition):

Keita, Namory. “Lattice model simulation of hydrogen effect on palladium gold alloys used as purification metal membranes.” 2012. Web. 16 Apr 2021.

Vancouver:

Keita N. Lattice model simulation of hydrogen effect on palladium gold alloys used as purification metal membranes. [Internet] [Masters thesis]. Georgia Tech; 2012. [cited 2021 Apr 16]. Available from: http://hdl.handle.net/1853/44712.

Council of Science Editors:

Keita N. Lattice model simulation of hydrogen effect on palladium gold alloys used as purification metal membranes. [Masters Thesis]. Georgia Tech; 2012. Available from: http://hdl.handle.net/1853/44712

2. Haldoupis, Emmanuel. Mulitscale modeling and screening of nanoporous materials and membranes for separations.

Degree: PhD, Chemical and Biomolecular Engineering, 2013, Georgia Tech

The very large number of distinct structures that are known for metal-organic frameworks (MOFs) and zeolites presents both an opportunity and a challenge for identifying materials with useful properties for targeted separations. In this thesis we propose a three-stage computational methodology for addressing this issue and comprehensively screening all available nanoporous materials. We introduce efficient pore size calculations as a way of discarding large number of materials, which are unsuitable for a specific separation. Materials identified as having desired geometric characteristics can be further analyzed for their infinite dilution adsorption and diffusion properties by calculating the Henry's constants and activation energy barriers for diffusion. This enables us to calculate membrane selectivity in an unprecedented scale and use these values to generate a small set of materials for which the membrane selectivity can be calculated in detail and at finite loading using well-established computational tools. We display the results of using these methods for >500 MOFs and >160 silica zeolites for spherical adsorbates at first and for small linear molecules such as CO₂ later on. In addition we also demonstrate the size of the group of materials this procedure can be applied to, by performing these calculations, for simple adsorbate molecules, for an existing library of >250,000 hypothetical silica zeolites. Finally, efficient methods are introduced for assessing the role of framework flexibility on molecular diffusion in MOFs that do not require defining a classical forcefield for the MOF. These methods combine ab initio MD of the MOF with classical transition state theory and molecular dynamics simulations of the diffusing molecules. The effects of flexibility are shown to be large for CH₄, but not for CO₂ and other small spherical adsorbates, in ZIF-8. Advisors/Committee Members: Dr. David S. Sholl (Committee Chair), Dr. Christopher W. Jones (Committee Member), Dr. Krista S. Walton (Committee Member), Dr. Peter J. Hesketh (Committee Member), Dr. Sankar Nair (Committee Member).

Subjects/Keywords: Molecular simulations; Separations; Zeolites; Metal-organic frameworks; Nanoporous; Nanostructured materials; Membranes (Technology); Separation (Technology)

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

APA (6th Edition):

Haldoupis, E. (2013). Mulitscale modeling and screening of nanoporous materials and membranes for separations. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/47669

Chicago Manual of Style (16th Edition):

Haldoupis, Emmanuel. “Mulitscale modeling and screening of nanoporous materials and membranes for separations.” 2013. Doctoral Dissertation, Georgia Tech. Accessed April 16, 2021. http://hdl.handle.net/1853/47669.

MLA Handbook (7th Edition):

Haldoupis, Emmanuel. “Mulitscale modeling and screening of nanoporous materials and membranes for separations.” 2013. Web. 16 Apr 2021.

Vancouver:

Haldoupis E. Mulitscale modeling and screening of nanoporous materials and membranes for separations. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2021 Apr 16]. Available from: http://hdl.handle.net/1853/47669.

Council of Science Editors:

Haldoupis E. Mulitscale modeling and screening of nanoporous materials and membranes for separations. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/47669


Georgia Tech

3. Semidey Flecha, Lymarie. First-principles approach to screening multi-component metal alloys for hydrogen purification membranes.

Degree: PhD, Chemical Engineering, 2009, Georgia Tech

Metal membranes play a vital role in hydrogen purification. Defect-free membranes can exhibit effectively infinite selectivity for hydrogen. Membranes must meet multiple objectives, including providing high fluxes, resistance to poisoning, long operational standards, and be cost effective. Alloys offer an alternate route in improving upon membranes based on pure metal such as Pd. Development of new membranes is hampered by the large effort and time required not only to experimentally develop these membranes but also to properly test these materials. We show how first principle calculations combined with coarse-grained modeling can accurately predict H2 fluxes through binary and ternary alloy membranes as a function of alloy composition, temperature and hydrogen pressures. Our methods require no experimental input apart from the knowledge of the bulk crystal structure. Our approach is demonstrated for pure Pd, Pd-rich binary alloys, PdCu binary alloys, and PdCu-based ternary alloys. PdCu alloys have experimentally shown to have potential for resistance to sulfur poisoning. First, we used plane wave Density Functional Theory to study the binding and local motion of hydrogen for the alloys of interest. This data was used in combination with a Cluster Expansion Method along with the Leave-One-Out analysis to generate comprehensive models to predict hydrogen behavior in the interstitial binding sites within the bulk of the alloys of interest. These models not only were required to correctly fit our calculated data, but they were also required to properly predict behaviors for local conditions for which we had not collected information. These models were then used to predict hydrogen solubility and diffusivity at elevated temperatures. Although we are capable of combining first principle theory calculations with coarse grain modeling, we have explored a pre-screening method in order to determine which a particular material are worth performing additional calculations. Our heuristic lattice model is a simplified model involving as few factors as possible. It is by no means intended to predict the exact macroscopic H properties in the bulk of fcc materials, but it is intended as a guide in determining which materials merit additional characterization. Advisors/Committee Members: Dr. David S. Sholl (Committee Chair), Dr. Andrei G. Fedorov (Committee Member), Dr. Ronald R. Chance (Committee Member), Dr. Victor Breedveld (Committee Member), Dr. William Koros (Committee Member).

Subjects/Keywords: Pd alloys; Hydrogen purification; Alloys; Ternary alloys; Hydrogen; Hydrogen as fuel

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

APA (6th Edition):

Semidey Flecha, L. (2009). First-principles approach to screening multi-component metal alloys for hydrogen purification membranes. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/31710

Chicago Manual of Style (16th Edition):

Semidey Flecha, Lymarie. “First-principles approach to screening multi-component metal alloys for hydrogen purification membranes.” 2009. Doctoral Dissertation, Georgia Tech. Accessed April 16, 2021. http://hdl.handle.net/1853/31710.

MLA Handbook (7th Edition):

Semidey Flecha, Lymarie. “First-principles approach to screening multi-component metal alloys for hydrogen purification membranes.” 2009. Web. 16 Apr 2021.

Vancouver:

Semidey Flecha L. First-principles approach to screening multi-component metal alloys for hydrogen purification membranes. [Internet] [Doctoral dissertation]. Georgia Tech; 2009. [cited 2021 Apr 16]. Available from: http://hdl.handle.net/1853/31710.

Council of Science Editors:

Semidey Flecha L. First-principles approach to screening multi-component metal alloys for hydrogen purification membranes. [Doctoral Dissertation]. Georgia Tech; 2009. Available from: http://hdl.handle.net/1853/31710

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