Tesis sobre el tema "Desorption energy"

Unique physical properties such as small effective mass, high electron drift velocities, high electron mobility and small band gap energy make InN a candidate for applications in high-speed microelectronic and optoelectronic devices. The aim of this research is to understand the surface properties, desorption kinetics and thermal stability of InN epilayers that affect the growth processes and determine film quality as well as device performance and life time. We have investigated the structural properties, the surface desorption kinetics, and the thermal stability using Auger electron spectroscopy (AES), x-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), high resolution electron energy loss spectroscopy (HREELS), and temperature programmed desorption (TPD). Investigations on high pressure chemical vapor deposition (HPCVD)-grown InN samples revealed the presence of tilted crystallites, which were attributed to high group V/III flux ratio and lattice mismatch. A study of the thermal stability of HPCVD-grown InN epilayers revealed that the activation energy for nitrogen desorption was 1.6±0.2 eV, independent of the group V/III flux ratio. Initial investigations on the ternary alloy In0.96Ga0.04N showed single-phase, N-polar epilayers using XRD and HREELS, while a thermal desorption study revealed an activation energy for nitrogen desorption of 1.14 ± 0.06 eV. HREELS investigations of atomic layer epitaxy (ALE)-grown InN revealed vibrational modes assigned to N-N vibrations. The atomic hydrogen cleaned InN surface also exhibited modes assigned to surface N-H without showing In-H species, which indicated N-polar InN. Complete desorption of hydrogen from the InN surface was best described by the first-order desorption kinetics with an activation energy of 0.88 ± 0.06 eV and pre-exponential factor of (1.5 ± 0.5) ×105 s-1. Overall, we have used a number of techniques to characterize the structure, surface bonding configuration, thermal stability and hydrogen desorption kinetics of InN and In0.96Ga0.04N epilayers grown by HPCVD and ALE. High group V/III precursors ratio and lattice mismatch have a crucial influence on the film orientation. The effects of hydrogen on the decomposition add to the wide variation in the activation energy of nitrogen desorption. Presence of surface defects lowers the activation energy for hydrogen desorption from the surface.

During operation of heavy ion accelerators a significant pressure rise has been observed when the intensity of the high energy beam was increased. The cause for this pressure rise is ion induced desorption, which is the result when beam ions collide with residual gas molecules in the accelerator, whereby they undergo charge exchange. Since the change in charge state will affect the bending radius of the particles after they have passed a bending magnet, they will not follow the required trajectory but instead collide with the vacuum chamber wall and gas are released. For the Future GSI project FAIR (Facility for Antiproton and Ion Research) there is a need to upgrade the SIS18 synchrotron in order to meet the requirements of the increased intensity. The aim of this work was to measure the desorption yields, η, (released molecules per incident ion) from materials commonly used in accelerators: 316LN stainless steel, Cu, Etched Cu, gold coated Cu, Ta and TiZrV coated stainless steel with argon and uranium beams at the energies 5-100 MeV/u. The measurements were performed at GSI and at The Svedberg Laboratory where a new dedicated teststand was built. It was found that the desorption yield scales with the electronic energy loss to the second power, decreasing for increasing impact energy above the Bragg Maximum. A feasibility study on the possibility to use laser refractometry to improve the accuracy of a specific throughput system was performed. The result was an improvement by up to 3 orders of magnitude, depending on pressure range.

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.

The first part of this thesis deals with hydrogen storage materials, in view of their applications as promising energy carriers. One of the main open problems with these materials is: how can their decomposition temperature be lowered, when hydrogen is wanted to be released, so as to improve the energy efficiency of the process. A possible answer is given by joint decomposition of two or more hydrides, if very stable mixed compounds are formed (‘hydride destabilization’). Aiming at this result, the new hydride composite 2LiBH4-Mg2FeH6 was considered, it was synthesized, and its thermodynamic and kinetic properties were investigated. In the second part of this thesis work lithium oxide materials, of relevant interest for applications to batteries, were investigated. The chemical lithiation reaction of niobium oxide was considered, as equivalent to the electrochemical process of lithium insertion on discharging a Nb2O5 cathode vs. a metal Li anode. Thus, the Li2Nb2O5 compound was synthesized by reaction of monoclinic a-Nb2O5 with n-butyllithium.This material was investigated by neutron powder diffraction (D2B equipment at ILL, France) and its structure was Rietveld refined in space group P2 to wRp=0.045, locating the Li atoms inserted in the a-Nb2O5 framework.

The focus of the presented research is to examine the fundamental physics and chemistry of low-energy electron-stimulated reactions on adsorbate covered single crystal surfaces. Specifically, condensed SiCl₄ on the Si(111) surface and condensed H₂O on the TiO₂ (110) surface have been studied. By varying adsorbate film thicknesses, the coupling strength of the target molecule to the substrate and surrounding media dictates the progression of the electron induced reactions. To investigate the electron interactions with SiCl₄ on the Si(111) surface, desorbing cations and neutrals were detected via time of flight mass spectrometry (ToF-MS) where neutral chlorine atoms were ionized using a resonance enhanced multi-photon ionization (REMPI) technique. Structure in the cation and neutral yields were assigned to molecular excitations. At an incident electron energy of 10 eV, a resonance structure in the neutral yields was attributed to a negative ion resonance and observed in thick and thin films of SiCl₄. With monoenergetic electrons, specific surface reactions can be controlled which have implications for film growth, surface patterning and masking, and etching. For the H₂O/TiO₂ (110) system, the water interactions with the TiO₂ surface are revealed through the strong electron induced reaction dependencies on the water coverage. Understanding the nonthermal reaction landscape of H₂O on the TiO₂ (110) surface is crucial for developing the system as a catalytic source of hydrogen. The electron-stimulated oxidation of the TiO₂ (110) surface and electron induced sputtering of H ₂O was investigated. Irradiation of water films ([coverage]< 3 ML) oxidized the TiO₂ (110) surface similarly as surface oxidation via O₂ deposition. Each H₂O molecule in the first monolayer seems to be a target for the incoming electron initiating the oxidation. However, water coverages greater than a monolayer limited the oxidation process. The electron-stimulated desorption and sputtering yields of water from the TiO₂ (110) surface were measured as a function of water coverage. Surprisingly, the amount of water sputtered from the surface is nonlinearly dependent on water coverage.

One of the most crucial issues nowadays is the protection of the environment and the replacement of fossil fuels, which are abundantly used around the world, with more efficient and renewable sources. The highest portion of global energy demands today is used in heating and cooling purposes. One way of alleviating the fossil-based thermal energy uses is to harvest excess thermal energy using thermochemical storage materials (TCMs) for use at heating/cooling demands at different times and locations. Along this, in this master’s thesis, a bench-scale thermochemical heat storage (TCS) system is numerically designed, as a part of a collaborative project: Neutrons for Heat Storage (NHS), funded by Nordforsk. The TCS system that is designed herein employs the reversible chemical reaction of ammonia with a metal halide (MeX) for a heat storage capacity of 0.5 kWh, respectively releasing and storing heat during absorption and desorption of ammonia into and from the MeX. This system is designed for low temperature heat applications, around 40-80 °C. SrCl2 is chosen as the metal halide to be used, based on the research outcomes in determining the most suitable materials conducted by NHS project partners. In the ammonia-SrCl2 system, only the absorption and desorption between SrCl2∙NH3 and SrCl2∙8NH3 are considered. The main reason is because absorption/desorption between the last ammine and SrCl2 undergoes at a significantly higher/lower reaction pressure (for a given temperature), with a significant volume change compared to the rest of the ammines, and therefore is practically less cost effective. This thesis also includes a detailed discussion of four different thermochemical storage designs from literature, found as the most relevant to the present TCS system study, which use the reaction between ammonia and metal halides. The first system that was examined is a TCS system built by the NHS project partners at Technical University of Denmark (DTU), owing to its similarities with the desired project, regarding the design and parameters the system uses. This system works in batch mode, only allowing either absorption (i.e. heat release) or desorption (i.e. heat storage) at a given cycle. Thus, upgrading the design of this TCS system at DTU is considered as a most-likely solution to the research objectives of this current thesis project. Moreover, the TCS system at DTU uses storage conditions and desorption temperature similar to the current project’s desired low temperature range of 40-80 °C. The second system discussed herein from literature uses two reactors for cold and heat generation, which means that both charging and discharging processes occur simultaneously. This simultaneous operability is the main reason that this particular system was examined in this thesis. The next discussed system from literature also uses two reactors, for absorption and desorption processes, which work reversibly when each process is completed, like in the desired concept of this project. These two systems (i.e., the secondly and the thirdly discussed systems) use the reversible solid-gas reaction for absorption and desorption between SrCl2∙NH3 and SrCl2∙8NH3, however, the conditions of pressure and temperature between them differ. The second system from literature operates at desorption and absorption at respective conditions of 96 °C, 15 bar and 87 °C, 11 bar while the third system discussed operates at 103 °C, 16 bar and 59 °C, 3 bar during desorption and absorption respectively. The last system from literature that is discussed herein provides the same desorption temperature of 80 °C. Inaddition this particular study suggests that the reaction of solid with gaseous NH3 is better (than the solid with liquid NH3 reaction) based on results derived from several different low-pressure experiments of the reactions. The main differences between all these discussed systems from literature, as opposed to the desired TCS system design in this thesis project, concern the systems’ operating mode and the pressure and temperature-conditions. The first difference is that only one of the examined systems pumps the solid VIII powder salt around the system in contrast to the others that keep the salt static inside the reactors and pumped only the ammonia around the system, as chosen in the current system. The second difference concerns the operating conditions during absorption and desorption reactions, where these different systems operate at a widely different pressure and temperature conditions as compared to the current system expectations. Thus, there are four main lessons that were learnt via this literature analysis, to improve the TCS system at DTU to the desired new system in this work. The first lesson is related to the reactants’ transportation mechanism that should be used in this system. Regarding this, it was decided to maintain the solid salt (metal halide) stationary inside each reactor (but not pumping it instead of ammonia), similar to the majority of designs discussed from literature. According to the second and third lessons, the solid-gas reaction is the most suitable solution and only the reactions of absorption and desorption between SrCl2∙NH3 and SrCl2∙8NH3 are considered, following the experience from literature (for the reasons explained earlier). The last lesson regards the system’s suitable operating conditions and more specifically the TCS system’s temperatures that should match the district heating temperatures. Thus, the temperature point that was chosen as a priority was 80 °C, from the range 40- 80 °C set in the partner project NHS. To maintain this condition, therefore, the most suitable condition of pressure of both reactions (according to the equilibrium pressure vs temperature curve) was chosen to be at around 8 bar. This same pressure was chosen for both reactions, since the pressure difference between these reactors and the storage of ammonia (i.e. from 8 to 10 bar) should be as small as possible due to the high costs that can arise in the case of a higher pressure difference (i.e. requiring more compressors and heat exchangers). Inspired by these literature cases, firstly a conceptually suitable TCS system was proposed in this project and after that the final desired system was designed and was implemented and evaluated numerically. The numerical design and optimization of the chosen TCS system was performed herein by using the software Aspen Plus (version 9), which contains both fluids and solids in a simulation environment, using consistent physical properties. This TCS system is designed to store and release heat at around 80 °C and 8 bar through absorption and desorption by using two identical reactors respectively. Each reactor includes the amount of around 1 kg (more specifically 0.985 kg) strontium chloride salt reacting with 1.7 kg of ammonia. A verification system is also modelled in Aspen, using available experimental data from literature. Here, the modelled novel system design was adapted to this chosen other system layout from literature which uses the same reaction pair, yet at different operating conditions. This adapted system design in Aspen was then used to verify the chosen configuration and the reliability of the constructed system for the NHS project. Good agreements between the modelled results in Aspen against the available experimental data of this verification model are obtained. A sensitivity analysis is also conducted herein on the proposed novel TCS system to identify the optimum operating conditions and the behaviour of the chosen most important parameters of the system. The designed system provides an energy storage capacity of 0.5 kWh for the specific amounts (in volumetric flow rates) of ammonia and monoammine of strontium chloride, that comes from the analysis, of 1.08696 e-05 kmol/s and 1.5528 e-06 kmol/s respectively. For these specific values of the HTF, the analysis showed that the volumetric flow rates of the heat and cold external sources must be 1.56 l/min (which is decreasing with the increase of the inlet HTF temperature) and 0.42 l/min (which is increasing with the increase of the inlet HTF temperature) respectively. In conclusion, this study presents an ammonia-SrCl2 TCS benchscale system design that allows continuous heat storage and release, in an easy-to-scale up design, also suggesting optimum operating conditions.
En av de mest avgörande frågorna i dag är skyddet av miljön och utfasningen av fossila bränslen som används allmänt över hela världen för mer effektiva och förnybara resurser. Den största delen av den globala energibehovet idag avser uppvärmnings- och kylapplikationer. Ett sätt att minska fossilbaserad termiskenergianvändning är att lagra överskottsvärmeenergi genom termokemiska lagringsmaterial (TCM) och använda den för värme- och kylbehov vid olika tidpunkter och platser. I samband med detta är ett termokemiskt värmelagringssystem numeriskt utformat i detta mastersexamensprojekt, som en del av ett samarbetsprojekt Neutrons for Heat Storage (NHS) finansierat av Nordforsk. Det termokemiska lagringssystemet (TCS) som är konstruerat utnyttjar den reversibla kemiska reaktionen av ammoniak med en metallhalogenid (MeX) för en värmelagringskapacitet på 0.5 kWh, och frigör och lagrar värme respektive under absorption och desorption av ammoniak till och från MeX. Systemet är designat för lågtemperaturuppvärmningstillämpningar runt 40-80 °C. SrCl2 väljs som det mest lämpliga metallhalogeniden för systemet, baserat på studier som utförts av NHS-projektpartnerna. I ammoniak SrCl2-systemet beaktas endast absorption och desorption mellan SrCl2NH3 och SrCl28NH3. De huvudsakliga orsakerna till detta är att absorptionen/desorptionen mellan den sista aminen och SrCl2 kräver ett betydligt högre/lägre reaktionstryck (för en given temperatur), och resulterar i en betydande volymförändring jämfört med resten av aminerna, och är därför praktiskt taget mindre kostnadseffektivt. Detta mastersexamensprojekt inkluderar en detaljerad genomgång av fyra olika TCS-system från litteratur som använder reaktionen mellan ammoniak och metallhalogenider. Dessa väljs här eftersom dessa anses vara de mest relevanta (från litteratur) jämfört med det valda systemet i denna studie. Det första undersökta systemet är ett system byggt av NHS-projektpartnerna vid Danmarks Tekniska Universitet (DTU). Detta har valts på grund av likheterna med det önskade systemet i det aktuella mastersexamensprojektet, vad gäller systemdesign och parametrar. Detta system fungerar i batch-läge, vilket endast tillåter antingen absorption (dvs värmeavgivning) eller desorption (dvs värmelagring) under en specifik cykel. Således kan en uppgraderad design av detta TCS-system vid DTU möjligen vara en lämplig lösning på forskningsmålen för detta mastersexamensprojekt. Dessutom använder detta TCS-system från DTU ganska liknande driftsförhållanden (temperaturer och tryck) i nivå med det aktuella projektets önskade lågtemperaturintervall på 40-80 °C. Det andra systemet från den litteratur som diskuterats använder två reaktorer för kyla och värmeproduktion, vilket innebär att både laddningsoch urladdningsprocesser sker samtidigt. Denna samtidiga operation är främst anledningen till att systemet undersöktes, eftersom detta är en önskad funktion att uppnå i det aktuella projektet. Nästa system från den litteratur som diskuteras häri använder också två reaktorer för absorptions- och desorptionsprocesser, som fungerar reversibelt när varje process är klar, precis som önskat i detta projekt. Dessa två system (dvs det andra och det tredje diskuterade systemen) använder den reversibla fastgasreaktionen för absorption och desorption mellan SrCl2NH3 och SrCl28NH3, dock vid olika tryck- och temperaturförhållanden. Det andra systemet arbetar nämligen under kombinationer av absorption och desorption av 96 °C, 15 bar och 87 °C, 11 bar, medan det tredje systemet arbetar vid 103 °C, 16 bar respektive 59 °C, 3 bar. Det sista systemet som diskuterats från litteraturen arbetar vid samma temperatur som det önskade systemet gör (dvs. 80 ° C) och genom olika lågtrycksexperiment visar att den fasta salt-gasreaktionen är ett bättre val än reaktionen av det fasta saltet med flytande gasreaktion. De viktigaste skillnaderna mellan alla dessa diskuterade system från litteratur i motsats till det önskade TCS-system i detta mastersexamensprojekt, avser systemdriftläge samt deras tryck och X temperaturförhållanden. Den första skillnaden är att endast ett av alla undersökta system pumpar saltet i fast pulverform, till skillnad från de andra som håller saltet stillastående i reaktorerna och endast pumpar ammoniak. Den andra skillnaden gäller driftsförhållandena under absorptions- och desorptionsreaktioner där dessa system arbetar vid mycket olika tryck- och temperaturförhållanden jämfört med det nuvarande systemet. Således, från översynen av alla system, finns det fyra huvudsakliga lärdomar för att förbättra TCS-systemet vid DTU till det önskade nya systemet. Den första är relaterad till reaktanttransportmekanismen som bör användas i detta system. I detta avseende har det beslutats att hålla det fasta saltet (metallhalogenid) stillastående i varje reaktor (men inte pumpa det istället för ammoniak), till skillnad från de flesta system i litteraturen. Enligt dem andra och tredje lektionerna är den fasta gasreaktionen den mest lämpliga lösningen och endast reaktionerna på absorption och desorption mellan SrCl2∙NH3 och SrCl2∙8NH3 bör övervägas enligt erfarenheten från litteraturen (av de skäl som förklarats tidigare). Den sista lärdomen avser systemets lämpliga driftsförhållanden och mer specifikt TCS-systemets temperaturer för att matcha fjärrvärmetemperaturerna. Den temperaturpunkten valts som prioritet, från området 40-80 °C inställt av moderprojektet NHS, sattes till 80 °C. För att bibehålla detta tillstånd var det lämpligaste tryckvillkoret för båda reaktionerna (enligt jämviktstrycket kontra temperaturkurva) valdes att ligga på cirka 8 bar. Samma tryck valdes för båda reaktionerna, eftersom tryckskillnaden mellan dessa reaktorer och lagring av ammoniak (dvs. från 8 till 10 bar) borde vara så liten som möjligt på grund av de höga kostnaderna som kan uppstå vid högre tryckskillnad (dvs. fler kompressorer krävs och värmeväxlare). Inspirerad av denna litteratur föreslogs för det första ett konceptuellt lämpligt TCS-system i detta mastersexamensprojekt, varefter det slutliga systemet implementerades och utvärderades numeriskt för de önskade förhållandena. Den numeriska utformningen och optimeringen av det valda TCS-systemet utfördes här med hjälp av programvaran Aspen Plus (version 9), som innehåller både vätskor och fasta ämnen i en simuleringsmiljö, med konstant fysiska egenskaper. Detta TCS-system är utformat för att lagra och släppa värme vid cirka 80 °C och 8 bar genom absorption och desorption med användning av två identiska reaktorer respektive. Varje reaktor innefattar cirka 1 kg (närmare bestämt 0.985 kg) strontiumkloridsalt reagerande med 1.7 kg ammoniak. Ett verifieringssystem modelleras också i Aspen med hjälp av tillgängliga experimentella data från litteraturen. I detta anpassades den modellerade nya systemdesignen till denna valda andra verifieringssystemlayout från litteratur, som använder samma reaktionspar, men under olika driftsförhållanden. Denna anpassade systemdesign i Aspen användes sedan för att verifiera den valda konfigurationen och tillförlitligheten för det designade systemet för NHS-projektet. Här erhålls ett bra avtal för denna verifieringssystemdesign mellan Aspenmodellresultaten och experimentdata. Här utförs också en känslighetsanalys för det utformade TCSsystemet i det aktuella projektet för att identifiera de optimala driftsförhållandena och beteendet för de valda viktigaste parametrarna i systemet. Det konstruerade systemet ger en energilagringskapacitet på 0.5 kWh för de specifika mängderna (i volymflöde) av ammoniak och monoamin av strontiumklorid, som kommer från analysen, av 1.08696 e-05 kmol/s och 1.5528 e-06 kmol/s respektive. För dessa specifika värden på värmeöverföringsvätskan visade analysen att de volymetriska flödeshastigheterna för värme och kalla yttre källor måste vara 1.56 l/min (vilket minskar när temperaturen på värmeöverföringsvätskan ökar) och 0.42 l/min (som ökar när temperaturen på värmeöverföringsvätskan ökar). Sammanfattningsvis presenterar denna studie ett ammoniak-SrCl2 TCS-bänkskålsystem som möjliggör kontinuerlig värmelagring och frigöring, har en design som är lätt att anpassa och föreslår också optimala driftsförhållanden.

Résumé : Lors de l’utilisation de la radiation pour le diagnostic et le traitement du cancer, l’ADN est une cible importante due à son rôle dans la division cellulaire. La radiation y dépose de l’énergie par production abondante (10[indice supérieur 5] e[indice supérieur −]/MeV) d’électrons de basse énergie (EBE) (<50 eV) menant à la production de radicaux et à la dissociation de molécules. Une meilleure compréhension de ces phénomènes physico-chimiques mènera au développement de nouvelles stratégies en radioprotection et en radiothérapie. Il est primordial d’identifier et de quantifier ces dommages initiaux. Suite à des résultats obtenus par des expériences récentes (Li et al., 2010) sur des couches minces d’ADN irradiées par des EBE dans le vide, nous suggérons que certains produits désorbent en quantité significative. Nous proposons une méthode pour mesurer cette perte de matière en utilisant une balance à quartz pour mesurer in situ les changements de masse totale. Ce mémoire présentera la conception et la construction de l’appareil ainsi que les résultats d’irradiation de la thymine et de la thymidine. À 25 ◦ C, le taux de perte de masse spontanée des échantillons joue un rôle important pour les petites molécules comme la thymine (126 uma). L’irradiation augmente d’abord ce taux qui diminue d’un facteur 5 à 15 après une exposition prolongée, signe de modifications notables de l’échantillon. Pour des molécules plus imposantes comme la thymidine (242 uma), il n’y a pas de désorption spontanée et le taux de désorption induite par des électrons de 50 eV est de 0,4 ± 0,1 uma/e[indice supérieur -]. Cette méthode, nécessaire à la calibration d’autres expériences réalisées par HPLC et spectrométrie de masse, permet de compléter la quantificationdes fragments, qui peuvent aussi être l’origine de lésions subséquentes.
Abstract : DNA is the principle target of radiotherapy (RT) due to its crucial role in cellular growth and function. Ionizing radiation (IR) delivers its energy into the cell and its nucleus via sequential ionization events that produce many low-energy electrons (LEE)(10[superscript 5]e[superscript −] per MeV) which drive subsequent molecular dissociations and the formation of radicals and other reactive species. Since a better understanding of these mechanisms is needed to develop new strategies for radioprotection and RT, it is essential to identify and to quantify the initial damage induced by IR. Recent chromatographic (HPLC) analysis of short oligonucleotide irradiated with LEE in vacuo (Li et al., 2010) revealed that only ∼30 % of the loss of intact molecules could be explained by the formation of identifiable radiation products. We hypothesize that electron stimulated desorption (ESD) may account for some of the unexplained loss of the missing molecules. Here we propose a new experimental method to quantify this loss using a quartz crystal microbalance to measure in situ the total mass change due to ESD. This thesis describes the design and the construction of the novel apparatus and presents results for LEE irradiated thymine (thy) and thymidine (dT). We find that at 25 ◦ C, the thermal-induced mass loss is important for small molecules such as thy (126 amu). Upon irradiation at 50 eV, the rate of mass loss initially increases, but then decreased by factors between 5 and 15 indicating structural changes occurring at the sample surface. For larger molecules such as dT (242 amu), there is no thermal evaporation at 25 ◦ C and the LEE induced rate of desorption at 50 eV is 0.4 ± 0.1 amu/e[superscript -]. This work is needed to calibrate HPLC and mass spectrometry experiments allowing us to quantify the fragment species produced by LEE that are expected to induce further and biologically significant damage.

Lorsque la matière condensée est soumise à des rayonnements de haute énergie, des électrons secondaires de basse énergie (0-20 eV) sont produits en grande quantité. Ces électrons participent à part entière aux dommages induits dans la matière, incluant les processus d’érosion et de modifications chimiques. Les fragments produits au sein du milieu réagissent et de nouvelles espèces sont formées. Plusieurs domaines d’application sont concernés par ces processus, et plus particulièrement le design de dispositifs par lithographie ou par dépôts assistés par faisceaux focalisés et l’astrochimie. Les enjeux concernent l’identification des mécanismes induits par les électrons lents, le contrôle des fragments réactifs et espèces stables formés, ainsi que la détermination de grandeurs quantitatives permettant d’apprécier l’efficacité des processus impliqués. L’approche développée dans ce travail de thèse consiste à irradier des surfaces et interfaces directement avec des faisceaux d’électrons de basse énergie afin d’étudier les processus induits. Les réponses de films moléculaires supportés modèles (d’épaisseur variable) sont étudiées en fonction de l’énergie incidente des électrons et des doses délivrées. Dans les cas favorables, des méthodologies ont pu être proposées pour accéder à l’estimation de sections efficaces effectives. Pour ce faire, trois techniques expérimentales sont combinées. Les films déposés et les résidus formés sont analysés par spectroscopie de perte d'énergie d’électrons à haute résolution (HREELS) et désorption programmée en température (TPD). Les fragments neutres (et non pas ioniques comme le plus souvent) désorbant sous irradiation sont analysés en masse afin de mener une étude de désorption stimulée par impact d’électrons (ESD).Dans le contexte de la fonctionnalisation de surface, le greffage de centres carbonés hybridés sp2 sur un substrat de diamant poly-cristallin hydrogéné a été réalisé par irradiation électronique d’une couche mince de benzylamine. A 11 eV, le mécanisme dominant implique la dissociation en neutres du précurseur. La section efficace effective de greffage a pu être déterminée par HREELS suite à une unique irradiation, en tirant avantage du profil du faisceau d’irradiation. Dans le contexte de l’astrochimie, la réponse à l’irradiation par électrons lents de glaces d’ammoniac amorphes et cristallisées a été étudiée. La désorption de molécules d’ammoniac a été observée. Elle peut résulter de l’érosion directe du film et de mécanismes de désorption induite par excitation électronique (DIET). Différents processus de fragmentation/recombinaison ont été mis en évidence via la désorption des espèces neutres NHx (x = 1,2), H2 et N2. Une chimie particulièrement riche est induite par irradiation électronique à 13 eV. L’analyse temporelle des rendements ESD a permis la détermination de la section efficace de la désorption de NH3, et l’observation de la formation retardée de N2 et H2. L’analyse TPD des résidus a démontré la synthèse de diazène (N2H2) et d’hydrazine (N2H4) dans le film. Ces résultats peuvent aider à l’élucidation des écarts observés dans les abondances de NH3 et N2 dans les régions denses de l'espace. Enfin, les premiers travaux réalisés pour fonctionnaliser un substrat de façon résolue à l’échelle micrométrique sous irradiation d’électrons lents sont également présentés. La faisabilité de la procédure utilisant un microscope électronique à basse énergie (LEEM) a été démontré sur une monocouche de terphenylthiol (TPT). Des motifs de 5 μm de travaux de sortie différents ont été imprimés en travaillant à des énergies de 10-50 eV. Ensuite la réponse de films modèles de résines lithographiques (PMMA, polyméthacrylate de méthyle) à des irradiations électroniques a été étudiée, afin d’identifier les énergies favorables en vue d’une modification de surface résolue spatialement
High-energy irradiation of condensed matter leads to the production of copious amounts of low-energy (0-20 eV) secondary electrons. These electrons are known to trigger various dissociative processes leading to observed damages including erosion and chemical modifications. The resulting reactive species within the condensed media can also lead to the synthesis of new molecules. This has implications in several applications most especially in the design of lithographic methods, focused beam-assisted deposition, as well as in astrochemistry. In all these applications, it is important to identify the processes induced by low-energy electrons, study the reactive fragments and stable molecules produced to determine possibilities of controlling them, and generate quantitative data to gauge the efficiencies of these processes. The approach developed for this PhD work consists of directly irradiating surfaces and interfaces using low-energy electrons and studying the processes that arise. The responses of different model molecular films (of varying thickness) were studied as a function of incident electron energy and dose. In favorable cases, methodologies proposed herein can be used to estimate effective cross sections of observed processes. Three complementary surface-sensitive techniques were utilized for this purpose. To characterize the deposited films and formed residues, the High Resolution Electron-Energy Loss Spectroscopy (HREELS) and Temperature Programmed Desorption (TPD) were used. Neutral fragments (as opposed to their often-detected ionic counterparts) desorbing under electron irradiation were monitored using a mass spectrometer in a technique called Electron Stimulated Desorption (ESD).Within the context of surface functionalization, the grafting of sp2-hybridized carbon centers on a polycrystalline hydrogenated diamond substrate was realized through electron irradiation of a thin layer of benzylamine precursor deposited on its surface. At 11 eV, the dominant mechanism is proposed to be neutral dissociation of the precursor molecules. The effective cross section of the grafting process was estimated in only a single measurement from the HREELS map of the sample surface, taking advantage of the electron beam profile. Within the context of astrochemistry, on the other hand, the responses of crystalline and amorphous NH3 ices were studied under electron impact. The desorption of intact NH3 was observed which resulted in the direct erosion of the film proceeding through a mechanism consistent with desorption induced by electronic transitions (DIET). Different fragmentation and recombination processes were also observed as evidenced by detected neutral species like NHx (x=1,2), N2, and H2. Aside from desorption, a wealth of chemical processes was also observed at 13 eV. Temporal ESD at this energy allowed for the estimation of the effective cross section of NH3 desorption and observing the delayed desorption of N2 and H2. TPD analysis of the residues also provided evidence of N2H2 and N2H4 synthesis in the film. These results can help explain the observed discrepancies in abundances of NH3 and N2 in dense regions in space. Lastly, this PhD work will present prospects for these electron-induced processes to be constrained spatially in microscopic dimensions for lithographic applications. The feasibility of the procedure utilizing Low-Energy Electron Microscope (LEEM) was demonstrated on a terphenylthiol self-assembled monolayer (TPT SAM) specimen. Spots of 5 μm in diameter with different work functions were imprinted on the surface using energies from 10-50 eV. Electron-induced reactions in thin-film resists (PMMA, poly(methyl methacrylate)) were also studied at low-energy identifying opportunities for energy- and spatially-resolved surface modification

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2010.
Committee Chair: Orlando, Thomas; Committee Member: El-Sayed, Mostafa; Committee Member: First, Phillip; Committee Member: Lackey, Jack; Committee Member: Tolbert, Laren. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Este trabalho tem por objetivo avaliar o desempenho econômico - custo operacional energético e custo de investimento - do processo de absorção químicaseguida de dessorção de dióxido de carbono (CO2),comparando-se os seguintes solventes da classe das aminas: monoetanolamina (MEA) e a mistura metildietanolamina/piperazina (MDEA/PZ), utilizando-se o simulador de processo Aspen Plus®. Para a avaliação da operação de absorção, recorreu-se primeiramente à implementação de um modelo matemático de absorção desenvolvido em planilha eletrônica,para comparar e validar o comportamento dos perfis de temperaturas resultantes das simulações com o Aspen Plus. Este modelo foi desenvolvido a partir dos parâmetros de transferência de massa e variáveis de processo pré especificadas. Tanto no modelo em planilha como no modelo do AspenPlus®, o dimensionamento das colunas de absorção e dessorção foram definidos a partir das variáveis de processo, considerando-se aspectos hidrodinâmicos e de transferência de massa. As simulações foram realizadas inicialmente em ciclo aberto, com as concentrações iniciais de aminas, e em seguida em ciclo fechado, com acorrente de fundo da coluna de dessorção reciclada para a alimentação da coluna de absorção, com coeficientes de carga praticamente iguais, emulando-se, assim o o ciclo fechado. Com base na literatura, estabeleceram-se as seguintes condições: a razão de 1:4 (em massa) entre a vazão de gás da mistura ar/CO2 e a vazão de solução de amina; faixas de pressões de operação de 1,0 bar(abs) a 1,3 bar(abs), na absorção, e 2,2 bar(abs.), na dessorção; eficiência de 94% de recuperação de CO2. Os dados apresentados, comparando-se MEA e a mistura MDEA/PZ revelaram uma redução no fator de consumo energético no refervedor na ordem de 15 % no sistema de dessorção empregando-se MDEA/PZ. Estimativas de custo operacionais e custo de investimento foram computados e também incluídos para a análise econômica. O crédito obtido pela diferença no custo operacional anual, entre as duas alternativas avaliadas, variou entre US$ 50.000,00/ano e US$ 140.000,00, em função da volatilidade do preço do insumo energético.
The aim of this work is to evaluate the economic performance - energy operational cost and investment cost - of the chemical absorption process using carbon dioxide desorption (CO2), comparing the following solvents of the amine class: monoethanolamine (MEA) and (MDEA / PZ), using the Aspen Plus® process simulator. For primary evaluation purpose of the absorption operation, a mathematical absorption model was developed in a spreadsheet, to compare and validate the behavior of the temperature profiles resulting from simulations with Aspen Plus. This model was developed from the pre-specified mass transfer parameters and process variables. Both in the spreadsheet model and in the AspenPlus® model, the dimensioning of the absorption and desorption columns were defined from the process variables, considering hydrodynamic and mass transfer aspects. The simulations were performed initially in the open cycle, with the initial concentrations of amines, and then in closed cycle, with the bottom stream of the desorption column recycled to feed the absorption column, with almost equal load coefficients, emulating the closed loop. Based on the literature, the following conditions were established: the ratio of 1: 4 (by mass) between the gas flow of the air / CO2 mixture and the flow rate of the amine solution; operating pressure ranges of 1.0 bar (abs) at 1.3 bar (abs) at absorption, and 2.2 bar (abs.) at desorption; efficiency of 94% CO2 recovery. The data presented, comparing MEA and the MDEA / PZ mixture revealed a reduction in the energy consumption factor in the order of 15% in what concerns the desorption system using MDEA / PZ. Estimates of operating costs and investment costs were computed for economic analysis. The credit obtained by the difference in the annual operating cost between the two alternatives ranged from US $ 50,000.00 / year to US $ 140,000.00, due to the volatility of the energy price.

Surface structure, chemical composition, bonding configuration, film polarity, and electronic properties of InN layers grown by high pressure chemical vapor deposition (HPCVD) have been investigated. Sputtering at an angle of 50-70 degrees followed by atomic hydrogen cleaning (AHC) was successful in removing the carbon contaminants. AHC is found to be the most effective cleaning process to remove oxygen contaminants from InN layers in an ultrahigh vacuum (UHV) system and produced a well ordered surface. Auger electron spectroscopy (AES) confirmed the cleanliness of the surface, and low energy electron diffraction (LEED) yielded a 1×1 hexagonal pattern demonstrating a well-ordered surface. High resolution electron energy loss spectra (HREELS) taken from the InN layers exhibited loss features at 550 cm-1, 870 cm-1 and 3260 cm-1 which were assigned to Fuchs-Kliewer phonon, N-H bending, and N-H stretching vibrations, respectively. Assignments were confirmed by observation of isotopic shifts following atomic deuterium dosing. No In-H species were observed indicating N-termination of the surface and N-polarity of the film. Broad conduction band plasmon excitations were observed centered at 3100 cm-1 to 4200 cm-1 in HREEL spectra acquired with 25 eV electrons, for a variety of samples grown with different conditions. Infrared reflectance data shows a consistent result with HREELS for the bulk plasma frequency. The plasmon excitations are shifted about 300 cm-1 higher in HREEL spectra acquired using 7 eV electrons due to the higher plasma frequency and carrier concentration at the surface than in the bulk, demonstrating a surface electron accumulation. Hydrogen completely desorbed from the InN surface upon annealing for 900 s at 425 ºC or upon annealing for 30 s at 500 ºC. Fitting the coverage versus temperature for anneals of either 30 or 900 s indicated that the desorption was best described by second order desorption kinetics with an activation energy and pre-exponential factor of 1.3±0.2 eV and 10-7.3±1.0 cm2/s, respectively. Vibrational spectra acquired from HREEL can be utilized to explain the surface composition, chemical bonding and surface termination, and film polarity of InN layers. The explanation of evidence of surface electron accumulation and extraction of hydrogen desorption kinetic parameters can be performed by utilizing HREEL spectra.

A catalytic route to hydrogen production via thermochemical water splitting is highly desirable because it directly converts thermal energy into stored chemical energy in the form of hydrogen and oxygen. Recently, the Davis group at Caltech reported an innovative low-temperature (max 850C) catalytic cycle for thermochemical water splitting based on sodium and manganese oxides (Xu, Bhawe and Davis, PNAS, 2012). The key steps are thought to be hydrogen evolution from a Na2CO3/MnO mixture, and oxygen evolution by thermal reduction of solids formed by Na+ extraction from NaMnO2. Our work is aimed at understanding the fundamental chemical processes involved in the catalytic cycle, especially the hydrogen evolution from water. In this project, efforts are made to understand the interactions between the key components (Na, O2, CO2, and water) in the hydrogen evolution steps on a well-defined MnO(100) single crystal surface, utilizing x-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and temperature programmed desorption (TPD). While some of the behavior of the catalytic system is observed with the model system developed in this work, hydrogen is only produced from water in the presence of metallic sodium, in contrast to the proposal of Xu et al. that water splitting occurs from the reaction of water with a mixture of Na2CO3 and MnO. These differences are discussed in light of the different operating conditions for the catalytic system and the surface science model developed in this work.
Ph. D.

This dissertation has investigated the adsorption, thermal behavior, and radiation (both photon and electron) processing of prebiotically-relevant ices and surfaces. A custom ultra-high vacuum (UHV) chamber has been built that is coupled with a Fourier Transform-Infrared (FT IR) spectrometer and a Temperature Programmed Desorption (TPD) system that utilizes Quadrupole Mass Spectrometry (QMS) to study selected organic:surface systems. Formamide (HCONH₂) has been studied in two related but distinct studies relevant to primitive Earth and interstellar chemistry. First, in collaboration with a theory group, formamide’s interaction with kaolinite (Al6Si6O36H30), a clay mineral relevant to early Earth chemistry, has been studied experimentally and theoretically. Experimental infrared results are compared with calculated infrared frequencies obtained by our collaborators. TPD analysis is compared with the calculated values of adsorption energy, and the optimal kaolinite termination site for adsorption is reported. Second, the first thermal and radiation damage study of pure formamide and HCONH₂:H₂O mixed ices on an interstellar icy grain analog (SiO₂) is reported. A discussion of the pure formamide ice phases identified with FT-IR upon warm-up, as well as the TPD binding energies of HCONH₂ on SiO₂, is presented. The observed Lyman-alpha photochemical products and proposed formation mechanisms from pure formamide ice is reported and discussed. In addition, results of Lyman alpha processing of mixed HCONH₂:H₂O ices are provided. Low-energy electron irradiation of pure HCONH₂ and HCONH₂:H₂O mixed ices has also been reported for the first time. A third investigation has studied acetylene (C₂D₂) and acetonitrile (CH₃CN) interactions and radiation stability in mixed low-temperature ices to simulate possible prebiotic reactions that may occur on Saturn’s moon, Titan. This investigation contributes to understanding the possible consumption, trapping, and degradation of these species on the surface of Titan.

The presented thesis deals with the utilization of TOF-LEIS analytical method in the area of nanostructure analysis. A new procedure for depth profiling of the elemental composition of the sample, based on the alternate measurement with the DSIMS method, was established. The TOF-LEIS method is able to detect the interface between the layers before its mixing by the ion beam of the DSIMS method. Furthermore, a procedure of TOF-LEIS spektra modification was established to obtain the actual concentration of elements in the sample by reduction of a multiple collision contribution. By comparison of TOF-LEIS spectra with the results received by the DSIMS method the ratio of molybdenum and silicon ion yields was obtained. In the next section advantages of the TOF-LEIS method in combination with XPS during analysis of thermal stability of gold nanoparticles are presented. The mutual complementarity of both methods is shown and final conclusions are supported by electron microscopy images. The final section deals with a newly assembled apparatus for the TOF-SARS analytical method and shows its possibilities regarding the detection of hydrogen on the graphene.

Le montage optique assemble ici est destine a l'etude des interactions d'electrons de basse energie avec des couches adsorbees et la desorption d'ions negatifs. Il dirige sur des surfaces placees en ultra-vide des faisceaux electroniques de densite constante et d'energie ajustable et assure la collecte et l'analyse des ions negatifs desorbes. (i) un processus de desorption resonnante provoque d'intenses desorptions d'ions h# sur les surfaces d'aluminium, de magnesium ou de silicium couvertes de molecules de vapeur d'eau lorsque l'energie des electrons est voisine de 6,5 ev; cette desorption s'etablit des que le faisceau d'electrons arrive sur une surface fraichement preparee. Mais, sur ces surfaces, la desorption resonnante d'ions o# et oh# n'apparait qu'apres une transformation des couches adsorbees provoquee par un bombardement electronique applique plusieurs minutes. Le mecanisme de desorption resonnante est attribue a la dissociation d'un etat anti-liant voisine des processus attachements electroniques dissociatifs observes en phase gazeuse; (ii) sur d'autres metaux (ti, cr, w, ni) les desorptions resonnantes a tres basse energie restent peu detectables meme apres des bombardements electroniques prolonges. Ces bombardements prealables sont souvent indispensables pour provoquer une desorption d'ions o# a partir de molecules h#2o, co ou o#2 dans des collisions au-dela de 20 ev. Les caracteristiques de cette desorption dependent fortement du substrat et peu de l'adsorbat; (iii) des enregistrements complementaires d'intensite permettent de suivre les transformations des couches adsorbees operees par le bombardement electronique au travers des variations de travail de sortie et des modifications de rendement de retrodiffusion des electrons par la surface

Ce travail de these est une contribution experimental a l'etude des interactions des electrons de basse energie avec les molecules condensees sur un substrat metallique. La sonde de ces interactions est la detection des ions negatifs qui desorbent. A basse energie, ces ions sont formes par le mecanisme d'attachement electronique dissociatif (aed). L'objectif de ce travail est l'etude des effets de l'environnement sur la desorption stimulee d'ions negatifs, et la reactivite induite dans les films homogenes et heterogenes. Pour cela, nous avons etudie la desorption d'ions o a partir de films de o 2 condense sur divers substrats moleculaires protiques ou non, ayant des moments dipolaires variables (0 < < 3,92 d). Nous avons montre en particulier que la morphologie, a savoir l'existence de micropores dans la structure de d 2o condense a 15 k, conduit a une amplification des collisions des ions o , et permet d'expliquer les differentes caracteristiques des spectres de rendement d'ions o observees quand o 2 est condense sur d 2o. En ce qui concerne la reactivite induite, nous avons montre que l'interaction des electrons de basse energie avec cf 2cl 2 condense conduit a la synthese efficace de cl 2 avec un maximum d'efficacite vers 15 ev. Dans les films heterogenes o 2/cd 3cood, o 2/cd 3cn et o 2/ch 3oh, nous avons observe la desorption d'ions o en dessous du seuil de desorption de ces ions dans le film de o 2 pur. Le mecanisme implique est probablement la formation de complexe anionique (o 2. . M *), ou m * est une resonance de cd 3cood, cd 3cn ou ch 3oh de basse energie ( 5 ev).

L'interaction d'electrons de basse energie (0 - 25 ev) avec des molecules condensees conduit a la desorption d'ions negatifs et positifs dont les spectres de rendement et les distributions d'energie cinetique permettent de decrire les mecanismes et la dynamique des processus en jeu. Des etudes sur les molecules o 2, n 2o et cf 4 condensees sur un metal (pt) montrent que les mecanismes (l'attachement dissociatif et la dissociation dipolaire) et la dynamique de desorption dependent des conditions de condensation. - en multicouches de molecules d'oxygene o 2, la formation de resonances o - * 2 de symetrie +, interdites en phase gazeuse, contribue a la desorption d'ions o - et que la predissociation d'etats de rydberg o * 2 est responsable de la desorption d'ions o - et o + via le processus de dissociation dipolaire. - en monocouche ou submonocouche de o 2, un processus de desorption d'ions o - tres energetiques impliquant un transfert de charge du substrat metallique vers des fragments neutres o formes par excitation dissociative par impacts d'electrons sur o 2 condense est mis en evidence. - des distributions d'energie cinetique d'ions o - montrent que la dynamique de desorption depend de l'environnement dans lequel les molecules o 2 sont condensees et qu'en plus des collisions multiples des electrons incidents et des ions, les phenomenes de fluctuation de l'energie de polarisation et de creation de phonons dans le substrat et le milieu condense jouent un role important. - enfin l'interaction d'electrons avec l'oxygene moleculaire condense conduit a la production d'ozone o 3 en surface et en volume de l'adosorbat via des reactions atomes-molecules, avec un seuil a 3. 5 ev d'energie incidente.

This Ph.D. project was developed within the research projects of astrobiology “Space life- OPPS” and “Reservoirs for Planetary Atmospheres”. The project was focused on laboratory studies on photoprocessing and thermal desorption of formamide (HCONH2), acetonitrile (CH3CN), and acetaldehyde (CH3COH) in simulated space conditions. The analytical techniques used were Fourier Transformed Infrared Spectroscopy (FTIR), Temperature Programmed Desorption (TPD) analysis, and mass spectroscopy.

碩士
國立高雄科技大學
環境與安全衛生工程系
107
The soil and groundwater contamination issue caused by the previous industry development gradually attracts the public attention in Taiwan. Thermal desorption is one of the important technology used for remediation of soil contaminated with total petroleum hydrocarbon (TPH). Contaminants in the TPH contaminated soil is heated to boiling points and transferred into the gas phase, and then furtherly separated and treated. The current remediation projects which adopted the thermal desorption technology were to use the off-situ thermal desorption facilities in Taiwan. The off-situ treatment should include costs for the contaminated soil transportation and backfill soil and is less considered by the decision maker. In-situ treatment technology has advantages on cost and time saving for the contamination site remediation. The fossil fuel gradually runs out in the world. As well as the use of fossil fuel energy should meet more stringent environmental requirements. As such the search for the alternative energy is a critical and emerging issue. This research is to use biomass fuels, palm kernel shells, as the alternative energy in the thermal desorption technology for treatment of the TPH contaminated soil and to evaluate the efficiency of the in-situ treatment technology. The test method is the contaminated soil indirectly heated to above the boiling points of TPH, and then contaminants are gasified from the soil and transferred into gas phase. Particulates are separated from the gas phase and organic contaminants in the gas phase is furtherly treated by the air pollution control system. The thermal desorption is one of physical remediation technologies and used for treatment of numerous organic soil contaminants with high removal efficiency. The thermal desorption is a technology with high potential to be developed for the contamination remediation in the recent few years. Biomass energy is one of future alternative energies, and better than the wind power and solar energy to be the base load electricity. Therefore, the industry and technology in use of biomass energy for the business operation is more acceptable by the market. Biomass energy used for replacement of fossil fuel can reduce the carbon dioxide emission and greenhouse effect. Based on the verification results, the use of biomass energy can also reduce the emissions of SO2 and NOx and can create a green cycling economy. In the current trend of the energy saving and the environment of reduce carbon, if biomass can be used as one of the alternative energy source of the thermal desorption technology, it will improve the cost efficiency in the soil remediation in the future. The cost of soil treatment with thermal desorption of synthetic gas from palm kernel shell is only about 60% of diesel fuel, which can greatly reduce energy costs and with competitive advantage in soil remediation measures. Its byproducts - carbonized palm kernel shell is one kind of biocoal that can be reused, the idea of treatment method meets the principle of circular economy. It also provides new thinking and application reference for the in-situ method of soil remediation. Key Word：Thermal desorption、Biomass energy、Palm Kernel Shell