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Zhang, Zhongfan (2012) MODEL STUDY OF PLATINUM NANOPARTICLE INTERACTIONS WITH γ-ALUMINA SINGLE CRYSTAL SUPPORTS. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Pt/γ-Al2O3 is arguably the most important heterogeneous catalyst system, as it is used in numerous technologically important processes, including oil refining, catalytic converters and fuel cells. Hence, many investigators have studied Pt/γ-Al2O3 both experimentally and theoretically. Yet, a significant gap exists between experiment and theory since theory models well defined finite systems whereas the commercially available γ-Al2O3 is polycrystalline with ill-defined morphologies, crystallography and impurities. The goal of this thesis project is to synthesize a model Pt/γ-Al2O3 heterogeneous catalyst system which is in the appropriate size regime for theoretical modeling. The critical challenge of this project is the creation of single crystal γ-Al2O3 thin films. To achieve this goal, the growth of single crystal γ-Al2O3 thin film on NiAl(110) surface was systematically investigated by oxidation in dry ambient air to determine the optimal oxidation parameters to form a reasonably flat, defect-free, single crystal γ-Al2O3 film. We determined that the optimal oxidation condition was 850℃ for 1 hour in air that produced an 80 nm thick film with an RMS value of 10 nm. The model Pt/ γ-Al2O3 system was produced by e-beam evaporation of Pt nanoparticles onto the surface of the γ-Al2O3. We characterized the Pt/γ-Al2O3 by transmission electron microscopy techniques for morphological and electronic structure of the nanoparticles and interfaces, respectively. We provide two feasibility studies of obtaining benchmark parameters that could be used by theorists: (1) the interfacial energy through a Wulff-Kashiew analysis of the supported Pt nanoparticles’ shapes and (2) information on the density of states at the interface using electron energy loss spectroscopy. During the course of this study, we also discovered aspects of NiAl oxidation kinetics in the intermediate temperature regime of 650-950℃ where only γ-Al2O3 forms, not the thermodynamically stable α-Al2O3. For example, crystallinity, epitaxy, and surface roughness of the oxide depends on the oxidation temperature due to temperature-dependent strain and relative diffusion behaviors.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Zhang, Zhongfanzhz33@pitt.eduZHZ33
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee MemberBarnard, John
Committee MemberGleeson, Brian
Committee MemberGray, Jennifer
Committee MemberFrenkel, Anatoly
Thesis AdvisorYang, Judith
Date: 26 September 2012
Date Type: Publication
Defense Date: 3 April 2012
Approval Date: 26 September 2012
Submission Date: 24 July 2012
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 143
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Materials Science and Engineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: γ-Al2O3 single crystal, NiAl alloy, oxidation, thin film growth, epitaxy, Pt nanoparticles, model catalyst, equilibrium shape, adhesion, interface, support interaction
Date Deposited: 26 Sep 2012 17:20
Last Modified: 15 Nov 2016 14:00


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