Tesi di Dottorato

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Author: search.filters.author.Falcone, GiovanniSubject: search.filters.subject.Fisica

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    Adsorption properties of carbon nanotubes and application of thermal desoprtion spectroscopy to ammonia and methane ices and zoisite
    (2010-12-14) Vasta, Roberta; Bonanno, Assunta; Falcone, Giovanni
    In this work we wanted to underline the importance of Thermal Desorption Spectroscopy and its applications to several branches of Physics. Temperature-programmed desorption techniques (TPD) are important to determinate kinetic and thermodynamic parameters of desorption processes and decomposition reactions. Knowledge of the nature of the desorption process is fundamental to understand the nature of the elementary chemical processes of adsorbates, as the energetics of bonding, the specification of the chemical nature of the bound species and the nature and magnitude of interactional effect between adsorbed species. We focused our attention on the applications of Thermal Desorption Spectroscopy (TDS) to High-Energies Physics, Astrophysics and Geophysics; in fact this technique was used, respectively, to investigate the molecular hydrogen adsorption on carbon nanotubes, the effects of electron bombardment on ammonia and methane ices and changes of zoisite mineral after heating. The molecular hydrogen adsorption on carbon nanotubes was studied to find a possible solution to vacuum system problems of Large Hadron Collider (LHC); in fact, the circular path of photon beams produces synchrotron radiation which deteriorates LHC vacuum desorbing gas molecules from the ring walls. Among the desorbed species the most problematic to pump out is H2. Since LHC elements operate at low temperatures, a possible solution to vacuum problem is the installation of cryosorbent materials on the LHC walls. In this work we study the possibility to use carbon nanotubes as criosorbers in future accelerators. Our sample, furnished by Prof. Nagy group of Chemical Engineering Department of Calabria University, is constituted by MWNTs synthesized by chemical vapor deposition using C2H4 and subsequently purified. Our investigations confirm that the carbon nanotubes have a great adsorption capacity also at low temperatures both for H2 and noble gases as Kr; then we observed that H2 adsorption on CNT is described by a first kinetic-order, while Kr adsorption is characterized by a zero kinetic-order. By means of TDS we calculate the activation energy for H2 adsorption on carbon nanotubes and we found a value of about 3KJ/mol, perfectly coherent with theoretic one. Moreover, from a comparison between nanotubes and other carbon-based material (as charcoal), we noted that adsorption efficiency for CNT is almost an order of magnitude higher then charcoal. So carbon nanotubes are good candidates to cryosorbers in future accelerators. 2 As Thermal Desorption Spectroscopy application to Astrophysics we studied the effect of electron bombardment on ammonia and methane ices. The interstellar medium is composed for 99% by gas; molecules, atoms and radicals at gas state condense on dust grains surface of molecular clouds (at 10 K) creating an icy mantle with a thickness of 0.1 μm. The presence of ices is confirmed by IR spectroscopy of obscured stellar sources and in interstellar grains are localized solid mixture containing H2O, CO, CH4 and NH3. In these environments ices are subjected to chemical and physical processes, specifically to bombardment of photons and cosmic rays, with the consequent synthesis of new organic species In this work we conducted an investigation of the chemical processing of ammonia and methane ices subjected to energetic electrons. By Thermal Desorption Spectroscopy we verify the production of new organic species, after energetic irradiation in interstellar ices, as diazene (N2H2), ethane (C2H6) and acetylene (C2H2). Finally, in Geophysics and Petrology Thermal Desorption Spectroscopy can be used to study minerals chemical composition. Our interest was focused on zoisite and the sample investigated was furnished by prof. Ajò from “Institute of Inorganic Chemistry and Surfaces” of CNR, in Padova. In this work we used TDS to investigate zoisite behaviour during heating form room temperature to 650oC and to understand if its modification into tanzanite variety after heating is due to structural changes or to a dehydration mechanism.
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    Aspects of Integrability in AdS/CFT duality
    (2011) Infusino, Gabriele; Rossi, Marco; Falcone, Giovanni
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    Turbulence and structures in plasma astrophysics
    (2011) Donato, Sandro; Carbone, Vincenzo; Falcone, Giovanni
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    Study of SU(N) gauge theories on the lattice
    (2006) Falcone, Rossella; Papa, Alessandro; Falcone, Giovanni
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    Periodic and aperiodic structures realized by innovative soft-metter based techniques
    (2014-05-19) Infusino, Melissa; Umeton, Cesare; Agostino, Raffaele; Falcone, Giovanni
    Il presente lavoro di tesi `e basato sullo studio e l’utilizzo di tecniche sperimentali per la realizzazione di strutture periodiche ed a-periodiche su diverse scale di grandezza. La prima tecnica oggetto di studio rappresenta un nuovo approccio rispetto alle usuali tecniche olografiche e prevede l’utilizzo delle pi`u recenti tecnologie realizzate nell’ambito dell’olografia diffrattiva, quali i modulatori di fase spaziale. I modulatori di fase spaziale consentono la produzione di distribuzioni di intensit`a sia periodiche che a-periodiche ed in generale rendendo possibili geometrie difficilmente realizzabili con le classiche tecniche di interferenza a multi-fascio. Il sistema fotosensibile di partenza `e costituito da una miscela di pre-polimeri e cristalli liquidi nematici: la separazione di fase tra le due componenti `e indotta dalla fotopolimerizzazione. L’impiego dei cristalli liquidi consente la realizzazione di strutture dinamiche le cui propriet`a ottiche sono modificabili attraverso l’applicazione di stimoli esterni, quali campi elettrici ed ottici. Le strutture relizzate hanno una periodicit`a micrometrica che le rende applicabili nel campo dell’ottica. La seconda tecnica studiata si basa su fenomeni di auto-assemblaggio nei polimeri a blocchi e consente il raggiungimento di scale di grandezza inferiori: la periodicit`a delle strutture realizzate raggiunge infatti poche decine di nanometri. Nella tecnica di autoassemblaggio la separazione di fase tra le componenti `e regolata semplicemente dalla temperatura del sistema e le strutture risultanti hanno delle caratteristiche fortemente dipendenti dalle dimensioni dei costituenti. 3
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    Meccanismi di scambio di carica nell'interazione ione superficie
    (2014-05-19) Maletta, Stefano; Sindona, Antonio; Falcone, Giovanni
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    Chemical and morphological influence on nanostructures: synthesis and characterization of Carbon-based materials
    (2014-05-15) Policicchio, Alfonso; Agostino, G.; Falcone, Giovanni
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    Adsorption properties of carbon nanotubes and application of thermal desoprtion spectroscopy to ammonia and methane ices and zoisite
    (2014-05-15) Vasta, Roberta; Bonanno, Assunta; Falcone, Giovanni
    In this work we wanted to underline the importance of Thermal Desorption Spectroscopy and its applications to several branches of Physics. Temperature-programmed desorption techniques (TPD) are important to determinate kinetic and thermodynamic parameters of desorption processes and decomposition reactions. Knowledge of the nature of the desorption process is fundamental to understand the nature of the elementary chemical processes of adsorbates, as the energetics of bonding, the specification of the chemical nature of the bound species and the nature and magnitude of interactional effect between adsorbed species. We focused our attention on the applications of Thermal Desorption Spectroscopy (TDS) to High-Energies Physics, Astrophysics and Geophysics; in fact this technique was used, respectively, to investigate the molecular hydrogen adsorption on carbon nanotubes, the effects of electron bombardment on ammonia and methane ices and changes of zoisite mineral after heating. The molecular hydrogen adsorption on carbon nanotubes was studied to find a possible solution to vacuum system problems of Large Hadron Collider (LHC); in fact, the circular path of photon beams produces synchrotron radiation which deteriorates LHC vacuum desorbing gas molecules from the ring walls. Among the desorbed species the most problematic to pump out is H2. Since LHC elements operate at low temperatures, a possible solution to vacuum problem is the installation of cryosorbent materials on the LHC walls. In this work we study the possibility to use carbon nanotubes as criosorbers in future accelerators. Our sample, furnished by Prof. Nagy group of Chemical Engineering Department of Calabria University, is constituted by MWNTs synthesized by chemical vapor deposition using C2H4 and subsequently purified. Our investigations confirm that the carbon nanotubes have a great adsorption capacity also at low temperatures both for H2 and noble gases as Kr; then we observed that H2 adsorption on CNT is described by a first kinetic-order, while Kr adsorption is characterized by a zero kinetic-order. By means of TDS we calculate the activation energy for H2 adsorption on carbon nanotubes and we found a value of about 3KJ/mol, perfectly coherent with theoretic one. Moreover, from a comparison between nanotubes and other carbon-based material (as charcoal), we noted that adsorption efficiency for CNT is almost an order of magnitude higher then charcoal. So carbon nanotubes are good candidates to cryosorbers in future accelerators. 2 As Thermal Desorption Spectroscopy application to Astrophysics we studied the effect of electron bombardment on ammonia and methane ices. The interstellar medium is composed for 99% by gas; molecules, atoms and radicals at gas state condense on dust grains surface of molecular clouds (at 10 K) creating an icy mantle with a thickness of 0.1 μm. The presence of ices is confirmed by IR spectroscopy of obscured stellar sources and in interstellar grains are localized solid mixture containing H2O, CO, CH4 and NH3. In these environments ices are subjected to chemical and physical processes, specifically to bombardment of photons and cosmic rays, with the consequent synthesis of new organic species In this work we conducted an investigation of the chemical processing of ammonia and methane ices subjected to energetic electrons. By Thermal Desorption Spectroscopy we verify the production of new organic species, after energetic irradiation in interstellar ices, as diazene (N2H2), ethane (C2H6) and acetylene (C2H2). Finally, in Geophysics and Petrology Thermal Desorption Spectroscopy can be used to study minerals chemical composition. Our interest was focused on zoisite and the sample investigated was furnished by prof. Ajò from “Institute of Inorganic Chemistry and Surfaces” of CNR, in Padova. In this work we used TDS to investigate zoisite behaviour during heating form room temperature to 650oC and to understand if its modification into tanzanite variety after heating is due to structural changes or to a dehydration mechanism.
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    Entanglement dynamics in a cavity and its protection by the quantum zeno effect
    (2014-05-15) Francica, Francesco; Plastina, Francesco; Falcone, Giovanni