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On the Interplay between Surface Segregation and Oxidation: From Pure Metals to Binary Alloys.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	On the Interplay between Surface Segregation and Oxidation: From Pure Metals to Binary Alloys./
作者:	Li, Chaoran.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2022,
面頁冊數:	195 p.
附註:	Source: Dissertations Abstracts International, Volume: 84-01, Section: B.
Contained By:	Dissertations Abstracts International84-01B.
標題:	Materials science. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=29214339
ISBN:	9798834050407

On the Interplay between Surface Segregation and Oxidation: From Pure Metals to Binary Alloys.
Li, Chaoran.

On the Interplay between Surface Segregation and Oxidation: From Pure Metals to Binary Alloys. - Ann Arbor : ProQuest Dissertations & Theses, 2022 - 195 p.

Source: Dissertations Abstracts International, Volume: 84-01, Section: B.

Thesis (Ph.D.)--State University of New York at Binghamton, 2022.

This item must not be sold to any third party vendors.

Surface segregation has drawn much scientific attention because of its direct relevance to the surface physical and chemical properties such as corrosion resistance, catalysis, electronic, and magnetic properties, etc. Typical phenomenological theories provide a qualitative prediction of surface segregation behavior by calculating the system mixing energy, pure metal surface energies, and atomic size mismatch of each component in the alloy. But designing the alloy with desired properties requires detailed knowledge of the surface. By utilizing a variety of in-situ spectroscopy and microscopy techniques, including ambient-pressure X-ray photoelectron spectroscopy (AP-XPS), aberration corrected low energy electron microscopy (AC-LEEM), and scanning tunneling microscopy (STM), we performed investigations on the surface segregation and composition tunability with external thermal and chemical stimuli.The research has focused on studying the surface segregation behavior of a series of metal and binary alloys during vacuum annealing and with the presence of oxygen and hydrogen. Using synchrotron-based AP-XPS, we demonstrate the tunability of the deoxygenation process of bulk dissolved oxygen in copper via a combination of H2 gas flow and stepwise increase of temperature that results in surface segregation of oxygen from deeper regions of bulk Cu. Such surface segregation of bulk dissolved oxygen is further demonstrated from the vacuum annealing of NiAl that leads to oxide island growth on NiAl(100), from which we demonstrate that the chemically ordered surface favors compact oxide island growth whereas the order-disorder transition at the surface results in non-compact oxide growth.Dynamic surface composition evolution of Cu3Au(100) is monitored in real time in response to the imposed environmental stimuli. Segregation of Au to the pristine surface under ultrahigh vacuum annealing leads to the phase separation with pure Au at the surface and alloyed Au in the subsurface. Upon switching to an oxidizing atmosphere, oxygen adsorption drives the surface segregation of Cu along with inward migration of pure Au to the subsurface. Switching to a H2 atmosphere results in oxygen loss from the oxygenated surface, thereby promoting Au surface segregation and reverting the surface to the pristine state with the Au termination. For comparison, the surface segregation in Cu3Pt(100) is also monitored in response to temperature and oxygen gas. Vacuum annealing leads to surface segregation of Cu along with the enrichment of Pt in the subsurface region. Upon switching to the O2 atmosphere, dissociative chemisorption of oxygen does not change the surface segregation profile from that under the vacuum annealing condition. A stepwise increase in the oxygen pressure results in the transformation pathway of Cu→Cu2O→CuO, in which the selective oxidation of Cu gives rise to further accumulation of Pt underneath the oxide/alloy interface that hinders the supply of Cu from the bulk to the oxide/alloy interface, thereby leading to the termination of the surface oxidation after the Cu2O→CuO conversion is completed. This differs from the transformation pathway of Cu→Cu2O→Cu2O/CuO for the oxidation of pure Cu and Cu-Au alloys, in which the oxidation of Cu continues and the Cu2O/CuO bilayer growth is constantly maintained.The structural and compositional information obtained in these studies is of fundamental importance and can potentially serve as a guide in alloy design and for the choice of environmental conditions to fine tune the surface properties of metals and alloys such as catalytic performance and corrosion resistance.

ISBN: 9798834050407Subjects--Topical Terms:

543314
Materials science.
Subjects--Index Terms:

Electron microscopy

On the Interplay between Surface Segregation and Oxidation: From Pure Metals to Binary Alloys.
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520 $a Surface segregation has drawn much scientific attention because of its direct relevance to the surface physical and chemical properties such as corrosion resistance, catalysis, electronic, and magnetic properties, etc. Typical phenomenological theories provide a qualitative prediction of surface segregation behavior by calculating the system mixing energy, pure metal surface energies, and atomic size mismatch of each component in the alloy. But designing the alloy with desired properties requires detailed knowledge of the surface. By utilizing a variety of in-situ spectroscopy and microscopy techniques, including ambient-pressure X-ray photoelectron spectroscopy (AP-XPS), aberration corrected low energy electron microscopy (AC-LEEM), and scanning tunneling microscopy (STM), we performed investigations on the surface segregation and composition tunability with external thermal and chemical stimuli.The research has focused on studying the surface segregation behavior of a series of metal and binary alloys during vacuum annealing and with the presence of oxygen and hydrogen. Using synchrotron-based AP-XPS, we demonstrate the tunability of the deoxygenation process of bulk dissolved oxygen in copper via a combination of H2 gas flow and stepwise increase of temperature that results in surface segregation of oxygen from deeper regions of bulk Cu. Such surface segregation of bulk dissolved oxygen is further demonstrated from the vacuum annealing of NiAl that leads to oxide island growth on NiAl(100), from which we demonstrate that the chemically ordered surface favors compact oxide island growth whereas the order-disorder transition at the surface results in non-compact oxide growth.Dynamic surface composition evolution of Cu3Au(100) is monitored in real time in response to the imposed environmental stimuli. Segregation of Au to the pristine surface under ultrahigh vacuum annealing leads to the phase separation with pure Au at the surface and alloyed Au in the subsurface. Upon switching to an oxidizing atmosphere, oxygen adsorption drives the surface segregation of Cu along with inward migration of pure Au to the subsurface. Switching to a H2 atmosphere results in oxygen loss from the oxygenated surface, thereby promoting Au surface segregation and reverting the surface to the pristine state with the Au termination. For comparison, the surface segregation in Cu3Pt(100) is also monitored in response to temperature and oxygen gas. Vacuum annealing leads to surface segregation of Cu along with the enrichment of Pt in the subsurface region. Upon switching to the O2 atmosphere, dissociative chemisorption of oxygen does not change the surface segregation profile from that under the vacuum annealing condition. A stepwise increase in the oxygen pressure results in the transformation pathway of Cu→Cu2O→CuO, in which the selective oxidation of Cu gives rise to further accumulation of Pt underneath the oxide/alloy interface that hinders the supply of Cu from the bulk to the oxide/alloy interface, thereby leading to the termination of the surface oxidation after the Cu2O→CuO conversion is completed. This differs from the transformation pathway of Cu→Cu2O→Cu2O/CuO for the oxidation of pure Cu and Cu-Au alloys, in which the oxidation of Cu continues and the Cu2O/CuO bilayer growth is constantly maintained.The structural and compositional information obtained in these studies is of fundamental importance and can potentially serve as a guide in alloy design and for the choice of environmental conditions to fine tune the surface properties of metals and alloys such as catalytic performance and corrosion resistance.
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