La thèse traite du transport de particules colloïdales en milieu poreux. L'influence des propriétés physico-chimiques et hydrodynamiques sur le dépôt et détachement de particules de latex a été étudiée en réalisant des expériences durant lesquelles des grandeurs macroscopiques (concentration dans les effluents, réduction de perméabilité) et microscopiques (variation de porosité par atténuation gamma) ont été mesurées. / This thesis deals with colloidal particle transport in porous media. The influence of physicochemical and hydrodynamic conditions on the deposition and detachment of latex particles was studied by performing a series of experiments during which macroscopic (effluent concentration, permeability reduction) and microscopic (porosity variation) properties were measured.

In dieser Dissertation wird eine neue Methode vorgestellt, welche die Untersuchung der Wechselwirkung von Atomen und Molekülen mit Oberflächen mit Ausdehnungen <10^-8 cm^2 gestattet. Die hochauflösende Massenspektrometrie an Nanopartikeln wird mit laserinduzierter thermischer Desorption kombiniert. Zur kontrollierten Variation der Temperatur der unter UHV-Bedingungen gespeicherten Siliziumdioxidpartikel wird ein IR-Laser verwendet. Die im Rahmen dieser Arbeit aufgebaute Apparatur beinhaltet die Kombination des IR-Lasers mit dem elektrodynamischen Partikelspeicher als auch den Aufbau eines externen optischen Streulichtnachweises mit einem Ar^+-Laser. Unter Berücksichtigung wirksamer Kühlmechanismen wird ein Zusammenhang zwischen Teilchentemperatur und erforderlicher IR-Bestrahlungsintensität hergestellt. Ein kinetisches Modell verknüpft die im Experiment als Funktion der Zeit gemessene Partikelmasse mit den grundlegenden physikalischen Größen zur Beschreibung von Adsorptions- und Desorptionsprozessen. Die vorgestellte neue experimentelle Methode wird exemplarisch anhand von Messungen wie zyklische Adsorptions- und Desorptionsmessungen bei Partialdrücken adsorbierender Moleküle von 10^-10-10^-11 mbar, Physisorption von Wasser und Charakterisierung der Oberfläche gespeicherter Partikel mittels thermischer Desorption bei Temperaturen bis 560 K demonstriert. Ein weiteres Beispiel beschreibt die Bestimmung der Aktivierungsenergie für die Desorption von Fullerenmolekülen, mit denen die Partikeloberfläche zuvor durch Bedampfung präpariert wurde. Die Bedampfung wird als zeitaufgelöster Adsorptionsvorgang gemessen. Abschließend wird die Entladung der Partikel beschrieben, die bei Temperaturen >550 K beobachtet wird. Die Entladung zeigt ein Schwellenverhalten und hängt offenbar von der Ladung der Partikel ab. Verschiedene Erklärungsmöglichkeiten werden diskutiert.

Thesis--Universität Dortmund, 2006. / Includes bibliographical references.

Water is of interest for understanding the formation history and habitability of past and present solar system environments. It also has potential as a resource - when split to its constituent oxygen and hydrogen - both in space and on the Earth. Determining the sources, evolution, and eventual fate of water on bodies easily reachable from Earth, especially Earth's moon, is thus of high scientific and exploration value to the private sector and government space agencies. Understanding how to efficiently split water with solar energy has potential to launch a hydrogen economy here on Earth and to power spacecraft more sustainably to far away destinations. To address the fundamental interactions of water with important surfaces relevant to space exploration and technology development, temperature programmed desorption (TPD) and water photolysis experiments under well controlled adsorbate coverages have been carried out and are described in detail in this thesis. TPD experiments under ultra-high vacuum (UHV) conditions were conducted on lunar surrogate materials and genuine lunar samples brought to Earth by the Apollo program. The TPD's were conducted to determine the desorption activation energies of water chemisorbed directly to the powder surfaces, knowledge of which can improve existing models of water evolution on Earth's moon and aid in interpreting data collected by spacecraft-based investigations at the Moon. The TPD experiments of molecular water interacting with two lunar surrogates (micronized JSC-1A and albite) in ultra-high vacuum revealed water desorption during initial heating to 750 K under ultra-high vacuum. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) indicated possible water formation during the initial heating via recombinative desorption of native hydroxyls above 425 ± 25K. Dissociative chemisorption of water (i.e., formation of surface hydroxyl sites) was not observed on laboratory time scales after controlled dosing of samples (initially heated above 750 K) with 0.2 - 500 L exposures of water. However, pre-heated samples of both types of surrogates were found to have a distribution of molecular water chemisorption sites, with albite having at least twice as many as the JSC-1A samples by mass. A fit to the TPD data yields a distribution function of desorption activation energies ranging from ~0.45 eV to 1.2 eV. Using the fitted distribution function as an initial condition, the TPD process was simulated on the timescale of a lunation. A preview of these results and their context was published in Icarus (2011) 213, 64, doi: 10.1016/j.icarus.2011.02.015 by lead author Charles Hibbitts and the full treatment of the results from the TPD on lunar surrogates (presented here in Chapter 2) has been published in the Journal of Geophysical Research – Planets (2013) 118, 105, doi: 10.1002/jgre.20025 by lead author Michael J Poston. The desorption activation energies for water molecules chemisorbed to Apollo lunar samples 72501 and 12001 were determined by temperature programmed desorption (TPD) experiments in ultra-high vacuum. A significant difference in both the energies and abundance of chemisorption sites was observed, with 72501 retaining up to 40 times more water (by mass) and with much stronger interactions, possibly approaching 1.5 eV. The dramatic difference between the samples may be due to differences in mineralogy, surface exposure age, and contamination of sample 12001 with oxygen and water vapor before it arrived at the lunar sample storage facility. The distribution function of water desorption activation energies for sample 72501 was used as an initial condition to mathematically simulate a TPD experiment with the temperature program matching the lunar day. The full treatment of the TPD results from these two lunar samples (presented here in Chapter 3) has been submitted with the title "Water chemisorption interactions with Apollo lunar samples 72501 and 12001 by ultra-high vacuum temperature programmed desorption experiments" to Icarus for publication in the special issue on lunar volatiles by lead author Michael J Poston. A new ultra-high vacuum system (described in Chapter 4) was designed and constructed for planned experiments examining the possible formation of hydrated species, including water, from interaction of solar wind hydrogen with oxygen in the lunar regolith and to examine the effects of the active radiation environment on water adsorption and desorption behavior on lunar materials. This system has been designed in close collaboration with Dr. Chris J Bennett. An examination of a unique system for water photolysis - zirconia nanoparticles for hydrogen production from water with ultra-violet photons - was performed to better understand the mechanism and efficiency of water splitting on this catalyst. Specifically, formation of H₂ from photolysis of water adsorbed on zirconia (ZrO₂) nanoparticles using 254 nm (4.9 eV) and 185 nm (6.7 eV) photon irradiation was examined. The H₂ yield was approximately an order of magnitude higher using monoclinic versus cubic phase nanoparticles. For monoclinic particles containing 2 monolayers (ML) of water, the maximum H₂ production rate was ~0.4 µmole hr⁻¹ m⁻² using 185 + 254 nm excitation and a factor of 10 lower using only 254 nm. UV reflectance reveals that monoclinic nanoparticles contain fewer defects than cubic nanoparticles. A H₂O coverage dependence study of the H₂ yield is best fit by a sum of interactions involving at least two types of adsorbate-surface complexes. The first dominates up to ~0.06 ML and is attributed to H₂O chemisorbed at surface defect sites. The second dominates at coverages up to a bilayer. H₂ formation is maximum within this bilayer and likely results from efficient energy transfer from the particle to the interface. Energy transfer is more efficient for the monoclinic ZrO₂ nanoparticles and likely involves mobile excitons. These results (presented in Chapter 5) have been submitted with the title "UV Photon-Induced Water Decomposition on Zirconia Nanoparticles" for publication in the Journal of Physical Chemistry C by lead author Michael J Poston. This paper has been reviewed and will be accepted after minor modification.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

abstract: In this study, two novel sorbents (zeolite 4A and sodium polyacrylate) are tested to investigate if utilizing ultrasonic acoustic energy could decrease the amount of time and overall energy required to regenerate these materials for use in cooling applications. To do this, an experiment was designed employing a cartridge heater and a piezoelectric element to be simultaneously providing heat and acoustic power to a custom designed desorption bed while measuring the bed mass and sorbent temperature at various locations. The results prove to be promising showing that early in the desorption process ultrasound may expedite the desorption process in zeolite by as much as five times and in sodium polyacrylate as much as three times in comparison to providing heat alone. The results also show that in zeolite desorption utilizing ultrasound may be particularly beneficial to initiate desorption whereas in sodium polyacrylate ultrasound appears most promising in the after a temperature threshold is met. These are exciting results and may prove to be significant in the future as more novel heat-based cooling cycles are developed. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2018

In dieser Dissertation wird eine neue Methode vorgestellt, welche die Untersuchung der Wechselwirkung von Atomen und Molekülen mit Oberflächen mit Ausdehnungen <10^-8 cm^2 gestattet. Die hochauflösende Massenspektrometrie an Nanopartikeln wird mit laserinduzierter thermischer Desorption kombiniert. Zur kontrollierten Variation der Temperatur der unter UHV-Bedingungen gespeicherten Siliziumdioxidpartikel wird ein IR-Laser verwendet. Die im Rahmen dieser Arbeit aufgebaute Apparatur beinhaltet die Kombination des IR-Lasers mit dem elektrodynamischen Partikelspeicher als auch den Aufbau eines externen optischen Streulichtnachweises mit einem Ar^+-Laser. Unter Berücksichtigung wirksamer Kühlmechanismen wird ein Zusammenhang zwischen Teilchentemperatur und erforderlicher IR-Bestrahlungsintensität hergestellt. Ein kinetisches Modell verknüpft die im Experiment als Funktion der Zeit gemessene Partikelmasse mit den grundlegenden physikalischen Größen zur Beschreibung von Adsorptions- und Desorptionsprozessen. Die vorgestellte neue experimentelle Methode wird exemplarisch anhand von Messungen wie zyklische Adsorptions- und Desorptionsmessungen bei Partialdrücken adsorbierender Moleküle von 10^-10-10^-11 mbar, Physisorption von Wasser und Charakterisierung der Oberfläche gespeicherter Partikel mittels thermischer Desorption bei Temperaturen bis 560 K demonstriert. Ein weiteres Beispiel beschreibt die Bestimmung der Aktivierungsenergie für die Desorption von Fullerenmolekülen, mit denen die Partikeloberfläche zuvor durch Bedampfung präpariert wurde. Die Bedampfung wird als zeitaufgelöster Adsorptionsvorgang gemessen. Abschließend wird die Entladung der Partikel beschrieben, die bei Temperaturen >550 K beobachtet wird. Die Entladung zeigt ein Schwellenverhalten und hängt offenbar von der Ladung der Partikel ab. Verschiedene Erklärungsmöglichkeiten werden diskutiert.

(EN) Ambient mass spectrometry defines the versatile group of methods providing analysis of solid sample surfaces and liquids in an open atmospheric pressure environment, where the sample is simultaneously accessible to another treatment. Ambient mass spectrometry is a sharply developing research area in the analytical chemistry. It provides fast, direct analysis of objects without any sample pretreatment with the use of the mass spectrometer. Desorption electrospray ionization (DESI) and desorption atmospheric pressure photoionization (DAPPI) equipped with software control of the sample holder were investigated in this doctoral thesis. These methods use a spray of solvents for desorption and ionization molecules from solid substrate and they are suitable tools for mass spectrometry imaging (MSI) of low molecular organic compounds, where the chemical identity of molecules present on a surface is examined as a function of spatial distribution. This project deals with applications and instrumental development. As for the applications, the position of the defense glands on insect bodies, separation of the lipids in complex mixtures on thin-layer chromatography (TLC) plates, or steroid metabolites in woman urine during pregnancy were thus investigated. As for the instrumental development, the most...

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Diborane (B2H6) is a hydride gas often employed in high-purity industrial surface processes such as chemical vapor deposition or epitaxial layer growth. The use of diborane at industrial scales is complicated by the formation of higher-order borane contaminants in pure diborane gas via a complex series of gas-phase reactions. An advanced, rationally designed sorbent could stabilize diborane through interfacial interactions, dramatically reducing the decomposition rate without permanently trapping the molecule. However, the design of such a sorbent would require a nuanced understanding of diborane's fundamental surface chemistry, about which little is known. In the work presented in this thesis, a novel ultra-high vacuum (UHV) system was designed and employed to characterize the fundamental interactions of diborane with a variety of surfaces. In situ Fourier-transform infrared (FTIR) spectroscopy and temperature-programmed desorption (TPD) experiments were used in conjunction with density-functional theory (DFT) calculations to elucidate binding geometries and interaction mechanisms. On non-functionalized model surfaces such as CaF2 or amorphous carbon, diborane adsorbed only at cryogenic temperatures. Hydroxylated surfaces such as amorphous silica (SiO2) adsorbed significantly more diborane, which remained at slightly higher temperatures. FTIR spectra indicated the presence of hydrogen bonding between diborane and surface hydroxyl groups. DFT calculations revealed that the interaction takes the form of a novel bifurcated dihydrogen bond. In contrast with previous reports, diborane exhibited only weak interactions with the surface hydroxyl groups of silica. DFT calculations further elucidated that the irreversible reaction of diborane with surface hydroxyls is only possible in the presence of a second nucleophile (such as adventitious water). On the metal-organic framework (MOF) UiO-66 NH2, unique chemistry was observed in which diborane reacted with the –NH2 groups of the MOF linkers, yielding stable surface-bound products. DFT calculations determined the reaction mechanism to be dissociative adsorption of diborane, resulting in two amine-bound –BH3 moieties. Importantly, it was found that these fragments persisted at room temperature and could only leave the surface via the reverse reaction. The discovery that diborane can be stored as separate fragments that re-combine to yield the parent molecule has important implications for the development of new diborane sorbents. We hypothesize that surfaces designed with fixed, precisely spaced nucleophiles could enable the reversible storage of diborane. / Doctor of Philosophy / Diborane (B2H6) is a useful but hazardous gas employed in both academia and industry, often in processes that require ultra-high-purity source gases. However, diborane reacts with itself at room temperature, making the contamination of pure diborane very difficult to avoid. This problem could potentially be solved with a specially designed solid material that would sequester diborane without destroying it, but the design of such a material would require a much better understanding of diborane's chemistry with surfaces than currently exists. In this work, we employed ultra-high vacuum (UHV) methods to study the interactions between diborane and a variety of surfaces, with the ultimate goal of determining guiding principles for the design of diborane-stabilizing sorbents. Among the materials we studied were inorganic carbon, silica (SiO2), and a class of advanced microporous materials known as metal-organic frameworks (MOFs). Inorganic materials were found not to interact meaningfully with diborane. A novel hydrogen bond was discovered between diborane and the surface of silica, but the interaction was found to be too weak to provide significant stabilization. Most MOFs behaved similarly to silica. The MOF UiO-66-NH2, however, was found to react with diborane. Through a combination of computer simulations and UHV experiments, the precise nature of the reaction was determined. On the surface of UiO 66 NH2, diborane splits into two surface-bound BH3 molecules, where it is trapped until the reaction reverses. Importantly, it was found that BH3 can only leave the surface by recombining into diborane—effectively storing diborane on the surface to be released later. We hypothesize that this useful chemistry is due to the fixed distance between chemical groups on the MOF surface. This discovery suggests a promising strategy for the design of advanced diborane sorbents.