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Composition and chemistry of Pd-Ni-Co thin film alloys for hydrogen related applications

  • The discovery and design of high performance Pd-alloys is of great interest for the use of hydrogen as a future energy carrier. Therefore hydrogen has to be detected, separated from other gases and stored. In this respect this thesis presents the combinatorial synthesis and characterization of the ternary Pd-Ni-Co alloy System over a wide composition range based on so-called thin film alloy libraries. Those libraries are model systems to characterize a large number of alloy compositions at the same time. The sputter-deposition process is optimized for the gradient of the Pd concentration on the surface of the alloy library by the use of electron-excited Auger electron spectroscopy. The scientific goal of this work is the experimental Investigation of adsorbate-induced surface segregation phenomena on alloy libraries. The surface and bulk compositions of an alloy library are studied after deposition, H2 exposure and H2S poisoning. The co-segregation of Ni and Co to the surface isThe discovery and design of high performance Pd-alloys is of great interest for the use of hydrogen as a future energy carrier. Therefore hydrogen has to be detected, separated from other gases and stored. In this respect this thesis presents the combinatorial synthesis and characterization of the ternary Pd-Ni-Co alloy System over a wide composition range based on so-called thin film alloy libraries. Those libraries are model systems to characterize a large number of alloy compositions at the same time. The sputter-deposition process is optimized for the gradient of the Pd concentration on the surface of the alloy library by the use of electron-excited Auger electron spectroscopy. The scientific goal of this work is the experimental Investigation of adsorbate-induced surface segregation phenomena on alloy libraries. The surface and bulk compositions of an alloy library are studied after deposition, H2 exposure and H2S poisoning. The co-segregation of Ni and Co to the surface is observed. The segregation process is influenced by the oxidation of Ni and Co due to the contact with ambient air, by H2 and by H2S poisoning. Also at very high Pd concentrations in the range of 87 at.% to 97 at.%, which is interesting for the detection of very low H2-Concentrations in air, the co-segregation of Ni and Co takes place. The poisoning effects were investigated in detail on a pre-selected Pd-Ni-Co alloy by photoelectron spectroscopy (XPS, HAXPES) in addition to AES and EDX. The composition profile of the alloy on the nm scale is acquired and the surface and bulk chemistry is discussed before and after poisoning. The composition of the alloy only changed within the first 3 nm due to H2S exposure. In the ternary Pd-Ni-Co alloy system Pd is present in its metallic state, while Ni and Co show several oxidation states. The presented concepts of ternary alloy development pave the way for the systematic synthesis and characterization of new ternary transition metal alloy systems.zeige mehrzeige weniger

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Metadaten
Autor*innen:Julius Kühn
Dokumenttyp:Dissertation
Veröffentlichungsform:Graue Literatur
Sprache:Englisch
Jahr der Erstveröffentlichung:2016
Titel verleihende Institution:Technische Universität Berlin, Fakultät II - Mathematik und Naturwissenschaften
Gutachter*innen:Wolfgang UngerORCiD, Thorsten Ressler
Datum der Abschlussprüfung:02.11.2015
Verlag:Technische Universität
Verlagsort:Berlin
Erste Seite:1
Letzte Seite:127
DDC-Klassifikation:Naturwissenschaften und Mathematik / Chemie / Analytische Chemie
Freie Schlagwörter:(HAX)PES; AES; Bibliothek ternärer Pd-Legierungen; Hydrogen sensor; Library of ternary Pd-alloys; REM/EDX; Wasserstoffsensor
DOI:10.14279/depositonce-5002
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:14.04.2016
Referierte Publikation:Nein
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