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dc.contributor.author
Gerchow, Lars
dc.contributor.supervisor
Rubbia, André
dc.contributor.supervisor
Crivelli, Paolo
dc.contributor.supervisor
Prokscha, Thomas
dc.contributor.supervisor
Synal, Hans-Arno
dc.date.accessioned
2020-10-30T08:29:40Z
dc.date.available
2020-10-29T16:19:19Z
dc.date.available
2020-10-30T08:29:40Z
dc.date.issued
2020
dc.identifier.uri
http://hdl.handle.net/20.500.11850/448650
dc.identifier.doi
10.3929/ethz-b-000448650
dc.description.abstract
Positron, the anti-particle of the electron, and its bound state with an electron, positronium, have found many applications in physics and chemistry. Due to the unique sensitivity to a materials local electron density, positrons can be used to investigate complex voids structures. As such, the development and characterization of materials with precisely engineered porous networks is a vibrant area of research. Applied studies with positron have found relevance in catalysis, opto-, nano- and microelectronics, gas sorption, separation, and sensors, among others. The technique relies on the rapid annihilation of the positrons with the electrons of the material under study. In contrary to scattering, transmission or equilibrium techniques, the positron is a truly local probe of its surroundings. The methods studying the annihilation in time, energy and position are grouped under the term Positron annihilation spectroscopy (PAS). Studies have shown sensitivity to the amount, distribution, and connectivity of single site defects, micro- and mesoporosity levels. Control over these parameters are essential to guide the design for future materials. The objective of this thesis was to expand the scope of PAS for the characterization of novel nanoporous materials with advanced functionalities. One aspect of this work was increasing the availability of positron beams. Different production schemes exploiting the recent advances and availability of cyclotrons were investigated. With the development of new kinds of radioactive thin-film sources, a step towards small lab scale positron beams was made. The field of possible applications was expanded with studies on state-of-the-art materials with the ETH slow positron beam. A study on the pore evolution of ZSM-5 zeolite emphasizes the unique sensitivity of PAS to the presence of guest species within the micropore network. This opens new doors to study the impact of targeted inclusion of pendant molecules on the textural properties of other porous materials. Another study focused on the distinct impact of chemical properties, e.g. acidity, on the positron annihilation characteristics. The ability to evaluate both porosity and acidity in functional materials will widen the scope of the technique for the analysis of functional materials. Moreover, proof of concept studies on different type of nanocrystals, surface- anchored metal-organic frameworks, defect engineered copper films and carbon nanotubes were made. For more wide-spread usage of PAS in the general scientific community, also a strong fundamental understanding and the development of a solid theoretical framework for data analysis is essential. An automated analysis to derive the desired structural information without requiring an involved knowledge of the technique is a particular challenge. Therefore, another core activity of the thesis was the development of improved numerical tools and models to account for the complexity in the pore architecture of functional materials. Concluding, the work presented in this thesis expanded the number of successful application of PAS. Furthermore, it highlighted a set of problems which need to be tackled towards a more wide-spread use and proposed solution approaches.
en_US
dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.publisher
ETH Zurich
en_US
dc.subject
particle physics
en_US
dc.subject
positron
en_US
dc.subject
Positron annihilation spectroscopy
en_US
dc.subject
porosity
en_US
dc.subject
nanoporosity
en_US
dc.subject
mesoporosity
en_US
dc.subject
Material characterization
en_US
dc.title
Positronium Annihilation Spectroscopy Characterization of Novel Nano-porous Materials with Advanced Functionalities
en_US
dc.type
Doctoral Thesis
dc.date.published
2020-10-30
ethz.size
208 p.
en_US
ethz.code.ddc
DDC - DDC::5 - Science::530 - Physics
en_US
ethz.identifier.diss
26855
en_US
ethz.publication.place
Zurich
en_US
ethz.publication.status
published
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02010 - Dep. Physik / Dep. of Physics::02532 - Institut für Teilchen- und Astrophysik / Inst. Particle Physics and Astrophysics::03503 - Rubbia, André / Rubbia, André
en_US
ethz.date.deposited
2020-10-29T16:19:27Z
ethz.source
FORM
ethz.eth
yes
en_US
ethz.availability
Embargoed
en_US
ethz.date.embargoend
2023-10-30
ethz.rosetta.installDate
2020-10-30T08:30:00Z
ethz.rosetta.lastUpdated
2021-02-15T19:29:11Z
ethz.rosetta.versionExported
true
ethz.COinS
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