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You searched for subject:(hydrogen desorption mechanism). Showing records 1 – 2 of 2 total matches.

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Univerzitet u Beogradu

1. Kurko, Sandra V. 1982-. Uticaj modifikacije strukture MgH2 borom na proces dehidriranja.

Degree: Fakultet za fizičku hemiju, 2016, Univerzitet u Beogradu

Fizička hemija - Fizička hemija materijala / Physical chemistry - Physical chemistry of materials

Cilj ove doktorske disertacije je ispitati kakav uticaj ima modifikacija strukture MgH2 borom na proces dehidriranja. U prvom delu teze rađeni su proračuni na bazi teorije funkcionala gustine naelektrisanja (DFT od Density Functional Theory) u kojima su simulirane strukture MgH2 sa različitim procentom dodatog bora, kao i proračuni u kojima je simulirana (110) površina MgH2 bez i sa dodatkom bora. Praćen je uticaj koncentracije bora na stabilnost dopiranog jedinjenja i njegove elektronske osobine. Ispitane su interakcije atoma u dopiranom sistemu u odnosu na nedopiran hidrid i kako one utiču na difuziju vodonika odnosno vakancija u njemu. Ispitana je i zavisnost desorpcionih energija vodonika u funkciji zasićenosti i konfiguracije površine i dubine desorbovanih atoma u odnosu na površinu hidrida. Pronalaženjem putanje minimalne energije metodom napregnute elastične trake (NEB od Nudged Elastic Band) su određene aktivacione energije za proces desorpcije molekula vodonika iz dve različite konfiguracije sa dopirane i nedopirane (110) površine MgH2 i difuziju vakancija u zapremini hidrida. U drugom delu teze uticaj koji bor ima na dehidriranje MgH2 ispitivan je eksperimentalno, na uzorcima hidrida koji su bombardovani jonima B3+ energije 45 keV i fluenci 1012, 1015 i 1016 jona/cm2. Metodama rendgenostrukturne analize (XRD), laserske metode za određivanje raspodele veličine čestica (PSD) i skenirajuće elektronske mikroskopije (SEM) određene su morfologija i mikrostruktura početnog i bombardovanih uzoraka. Proces dehidriranja praćen je temperaturno programiranom desorpcijom (TPD)...

Advisors/Committee Members: Mentus, Slavko. 1946-.

Subjects/Keywords: hydrogen storage; DFT; boron; ion irradiation; desorption temperature; desorption mechanism; magnesium hydride

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

APA (6th Edition):

Kurko, S. V. 1. (2016). Uticaj modifikacije strukture MgH2 borom na proces dehidriranja. (Thesis). Univerzitet u Beogradu. Retrieved from https://fedorabg.bg.ac.rs/fedora/get/o:11676/bdef:Content/get

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Kurko, Sandra V 1982-. “Uticaj modifikacije strukture MgH2 borom na proces dehidriranja.” 2016. Thesis, Univerzitet u Beogradu. Accessed July 19, 2019. https://fedorabg.bg.ac.rs/fedora/get/o:11676/bdef:Content/get.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Kurko, Sandra V 1982-. “Uticaj modifikacije strukture MgH2 borom na proces dehidriranja.” 2016. Web. 19 Jul 2019.

Vancouver:

Kurko SV1. Uticaj modifikacije strukture MgH2 borom na proces dehidriranja. [Internet] [Thesis]. Univerzitet u Beogradu; 2016. [cited 2019 Jul 19]. Available from: https://fedorabg.bg.ac.rs/fedora/get/o:11676/bdef:Content/get.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Kurko SV1. Uticaj modifikacije strukture MgH2 borom na proces dehidriranja. [Thesis]. Univerzitet u Beogradu; 2016. Available from: https://fedorabg.bg.ac.rs/fedora/get/o:11676/bdef:Content/get

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


University of Illinois – Urbana-Champaign

2. Reich, Jason. Thermodynamics and kinetics of hydrogen storage in magnesium hydride: a theoretical study of catalyst-dopant, defect, and size effects.

Degree: PhD, 0337, 2014, University of Illinois – Urbana-Champaign

With their high capacity, light-metal hydrides – like MgH2 – remain under scrutiny as reversible H-storage materials. A key question persists: Is there a means to enhance the hydrogen desorption/adsorption properties of this “simple” hydride by decreasing size (e.g., creating nano-sized particles by ball-milling) and/or adding catalyst dopants? Thus, we need to determine accurately both the enthalpy and kinetic barriers controlling desorption, but for realistic, defected cases. Employing density functional theory (DFT) and simulated annealing, we studied initial H2 desorption from nanoclusters and semi-infinite stepped surfaces with and without transition-metal “catalyst” dopants (Ti or Fe). The large 450-atom supercell of the (110)x(1 ̅10) single stepped terrace permits the study of the effects of catalytic dopant with 10 unique dopant sites at step edges, kinks sites, and terrace sites. Extensive DFT-based simulated annealing studies were performed to find the dopants site preference and mechanism for catalyst-enhanced release of hydrogen, with additional detailed understanding from the spin-polarized electronic-structure (density of states) and charge densities. Different kink environments at the stable (110)x(1 ̅10) interface were explored to model the stability of diffusion of H to the dopant before desorption. For the most stable initial and final (possibly magnetic) states, extensive Nudged Elastic Band (NEB) calculations were performed to explore the potential energy surface (desorption enthalpies and kinetic barriers). A moment transition NEB calculation was created whereby each image was initialized to its most stable magnetic state and then images along the transition path were allowed to relax according to the NEB algorithm. This approach provided the lowest energy activation states. Together the DFT-based simulated annealing and NEB simulations determined the enthalpy change and transition-state (kinetic barrier) for desorption (H2 release to vacuum). Although small nanocluster (we focused on Mg31H62) structures are disordered (amorphous), the semi-infinite surfaces and nanoclusters have similar single, double, and triple H-to-metal bond configurations that yield similar H-desorption energies. Hence, we find that there is no size effect on desorption energetics with reduction in sample size, but dopants (as observed, e.g., Ti) do reduce the energy and kinetic barrier of H2 desorption. Overall, our results compare well with desorption experiments and elucidate the controlling chemistry for doped-MgH2 and its efficacy for use as a storage material. Notably, the same techniques used and developed here can be used for more complex hydrides or hydride reactions. Advisors/Committee Members: Johnson, Duane D. (advisor), Johnson, Duane D. (Committee Chair), Makri, Nancy (committee member), Nuzzo, Ralph G. (committee member), Ceperley, David M. (committee member).

Subjects/Keywords: hydrogen storage; thermodynamics; kinetics; magnesium hydride (MgH2); size effect; hydrogen; H2; desorption; catalysis; magnesium hydride defects; rutile semi-infinite surface; magnesium hydride nanocluster; Mg31H62; nudged elastic band; moment transition nudged elastic band; reversible H-storage; reversible H2 storage; reversible hydrogen storage; density functional theory (DFT); semi-infinite stepped rutile (110) surface; semi-infinite stepped surface; semi-infinite stepped magnesium hydride (MgH2) surface; activation energy; transition state; metal hydride; hydrogen desorption mechanism; H2 desorption mechanism; hydrogen desorption; H2 desorption

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

APA (6th Edition):

Reich, J. (2014). Thermodynamics and kinetics of hydrogen storage in magnesium hydride: a theoretical study of catalyst-dopant, defect, and size effects. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/46805

Chicago Manual of Style (16th Edition):

Reich, Jason. “Thermodynamics and kinetics of hydrogen storage in magnesium hydride: a theoretical study of catalyst-dopant, defect, and size effects.” 2014. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed July 19, 2019. http://hdl.handle.net/2142/46805.

MLA Handbook (7th Edition):

Reich, Jason. “Thermodynamics and kinetics of hydrogen storage in magnesium hydride: a theoretical study of catalyst-dopant, defect, and size effects.” 2014. Web. 19 Jul 2019.

Vancouver:

Reich J. Thermodynamics and kinetics of hydrogen storage in magnesium hydride: a theoretical study of catalyst-dopant, defect, and size effects. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2014. [cited 2019 Jul 19]. Available from: http://hdl.handle.net/2142/46805.

Council of Science Editors:

Reich J. Thermodynamics and kinetics of hydrogen storage in magnesium hydride: a theoretical study of catalyst-dopant, defect, and size effects. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2014. Available from: http://hdl.handle.net/2142/46805

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