Dipartimento di Fisica - Tesi di Dottorato
Permanent URI for this collectionhttp://localhost:4000/handle/10955/35
Questa collezione raccoglie le Tesi di Dottorato afferenti al Dipartimento di Fisica dell'Università della Calabria.
Browse
163 results
Search Results
Item Laser action in liquid crystals: from random to periodic syatems(2007) Ferjani, Sameh; Strangi, Giuseppe; Versace, CarloItem Towards more sustainable organic processes : heterocyclizations in non-conventional solvents(2017-09-19) Maner, Asif S.; Carbone, Vincenzo; Gabriele, Bartolo; Mancuso, RaffaellaThis thesis reports the synthesis of important heterocyclic derivatives by iodocyclization, carbonylation and cycloisomerization reactions in Non-Conventionl solvents like deep eutectic solvents (DES) and Ionic Liquids (ILs). In chapter one general aspects of green and sustainable chemistry and introduction to eco-friendly green solvents such as water, DES, ScCO2 and ILs are described. Carbonylation processes, their advantages, types were described along with the application of transition metal catalysis in the carbonylation reactions with mechanistic approaches discussed. In chapter two, we describe a convenient and general method for the synthesis of substituted thiophenes through heterocyclodehydration and iodocyclization of readily available 1-mercapto-3-alkyn-2-ols in DES as the solvents. In chapter three we discuss a convenient carbonylative approach to 2-oxazolidinone derivatives carried out in an ionic liquid as the solvent (EmimEtSO4) is presented. It is based on the sequential concatenation of two catalytic cycles, both catalyzed by the same metal species (auto-tandem catalysis). In chapter four we present iodocyclization reactions to obtain iodinated isobenzofuranones and isochromenones by iodolactonization of 2-alkynyl benzoic acids in ionic liquids. In particular here we have developed divergent syntheses of (E)-3-(iodoalkylidene) isobenzofuran-1(3H)-ones and 4-iodo-1H-isochromen-1-ones by base-free Iodolactonization of 2-alkynylbenzoic acids in ionic liquids. In chapter five we report the cycloisomerization of readily available 2-alkynylbenzoic acids using an ionic liquid as the reaction medium in the presence of CuCl2 as a simple and inexpensive catalyst. Although in principle two different cyclization pathways can be followed, leading to either 5-exo-dig mode or 6-endo-dig mode, we have found that substrates bearing an aryl group on the triple bond or a terminal triple bond can be selectively converted into the isobenzofuranone derivatives, using N-ethyl-N-methylmorpholinium dicyanamide (Mor1,2N(CN)2) as the solvent. On the other hand, and in a complementary manner, substrates substituted with an alkyl or an alkenyl group on the triple bond selectively led to isochromenones when the reaction was carried out EmimEtSO4 and with excellent recyclability of the catalyst/ionic liquid system.Item Improving oilfield performance enabling horizontal drilling techniques: developments and optimization of standard and special measures for a real case study(2017-11-13) Al Taie, Amer Abdulhakim; Carbone, Vincenzo; Romagnoli, RaffaeleDrilling technique is a crucial issue to pay attention to. Drilling a horizontal well has a great interest to the oil and gas industry since nowadays it provides attractive means for improving both production rate and yet the recovery efficiency. The great improvements in drilling technology make it possible to drill horizontally no matter how complex are the trajectories and how deep it is suppose to reach. This study aims at presenting the optimal design aspects of a horizontal well. Design aspects include the selection of bit and casing sizes, detection of setting depths and drilling fluid density, casing, hydraulics, well profile, and construction of drill string simulator. When many vertical wells exist, an oil field named (Z14 field) should be designated to have a short radius horizontal well able to increasing the productivity and to promote the developing of the field itself. A single build profile with build rate 90 deg/100ft is constructed based on geological data. A drill string simulator composed of soft-string model and buckling tendency is constructed to predict torque and drag of string for six operating conditions. These conditions are pick-up, slack-off, sliding, pick-up with rotation, slack-off with rotation and drilling with rotation. Results of loads analysis showed that the suggested drill string can be used without exceeding torsional, tensile and buckling strengths. Analysis of single build profile showed that the torque and drag while drilling horizontal well could be minimized by drilling with low build rate, employing lighter pipe, and improving the lubricating capability with oil base mud (low friction forces). A finite element model was constructed to predict inclination tendency for multistabilizer rotary BHA in three dimensions, static condition. The bottom hole assembly was idealized with beam element capable of resisting axial forces, bending moments about the two principal axes, and twisting moments about its centroidal axis. Bit and stabilizer were treated as contact point and restricted from movement in all directions. Each element is loaded with gravity and normal contact forces. Model validation showed closer agreement between the model and Jiazhi's method (analytic) for slick, single, and two stabilizers BHA, compared to Akgun results. Predictions with finite element model showed that for building assembly, the weight on bit had small effect on bit side force especially in high angle wells. Also inclination tendency (building, dropping) would depend on position of the stabilizer, diameter of drillcollar behind the bit, and number of stabilizers.Item Rischio sismico ambientale e degli edifici: analisi tecnica HVSR - Aspetti teorici e aspetti sperimentali(2017-07-17) Magarò, Floriana; Carbone, Vincenzo; Zinno, RaffaeleItem Synthesis and characterization of nanomaterials: graphene, silicene and carbon nano- onions(2017-10-20) Osman, Salih Mohamed; Critelli, Salvatore; Caputi, LorenzoThe electronic structure of the graphene/Ni(111) system was investigated by means of electron energy-loss spectroscopy (EELS). A single layer of graphene has been obtained on Ni(111) by dissociation of ethylene. Angle-resolved EEL spectra show a low energy plasmon dispersing up to about 2 eV, resulting from fluctuation of a charge density located around the Fermi energy, due to hybridization between Ni and graphene states. The dispersion is typical of a two-dimensional charge layer, and the calculated Fermi velocity is a factor of ~0.5 lower than in isolated graphene. The interface-π plasmon, related to interband transitions involving hybridized states at the K point of the hexagonal Brillouin zone, has been measured at different scattering geometries. The resulting dispersion curve exhibits a square root behavior, indicating also in this case a two-dimensional character of the interface charge density. As well, it has been shown that it is possible to use EELS in the reflection mode to measure the fine structure of the carbon K-edge in monolayer graphene on Ni(111), thus demonstrating that reflection EELS is a very sensitive tool, particularly useful in cases where the TEM-based ELNES cannot be applied. Clean Ag(111) surface and the two phases of silicene on Ag(111), mixed (4×4, √13×√13R19°, 2√3×2√3R30°) and 2√3×2√3R30, have been studied by XPS, LEED and EELS. EEL spectra of the Ag(111) surface covered by silicene in the (4×4, √13×√13R19°, 2√3×2√3R30°) mixed phase shows a well-defined plasmon peak whose center is located at about 1.75 eV. The 2√3×2√3R30° phase shows EEL spectra that exhibit a peak located at about 0.75 eV loss, which moves clearly towards higher energies with increasing momentum transfer. The typical parabolic dispersion relation obtained from such spectra confirms that the peak is due to a collective excitation which is evidently associated to the silicene layer. These plasmons associated to silicene have never been observed in the past. Our results show that the plasmonic properties of silicene on Ag(111) are strongly dependent on the geometrical arrangement of Si atoms with respect to the substrate. Carbonaceous nanomaterials have been obtained by underwater arc discharge between graphite electrodes. TEM images showed that the resulting particles suspended in water consist of CNOs with other carbonaceous materials such as CNTs and graphene. We observed for the first time the formation of a solid agglomerate on the cathode surface. Raman and TEM studies revealed that the agglomerate is made exclusively of CNOs. The defragmentation of such agglomerate allows to obtain CNOs free of other carbonaceous materials without the complex purification procedures needed for floating nanomaterialsItem High-energy resummation in semi-hard processes at the LHC(2017-06-30) Celiberto, Francesco Giovanni; Carbone, Vincenzo; Papa, AlessandroSemi-hard processes in the large center-of-mass energy limit offer us an exclusive chance to test the dynamics behind strong interactions in kinematical sectors so far unexplored, the high luminosity and the record energies of the LHC providing us with a richness of useful data. In the Regge limit, s jtj, fixed-order calculations in perturbative QCD based on collinear factorisation miss the effect of large energy logarithms, which are so large to compensate the small QCD coupling s and must therefore be accounted for to all perturbative orders. The BFKL approach represents the most powerful tool to perform the resummation to all orders of these large logarithms both in the LLA, which means inclusion of all terms proportional to ( s ln(s))n, and NLA, which means inclusion of all terms proportional to s( s ln(s))n. The inclusive hadroproduction of forward jets with high transverse momenta separated by a large rapidity gap at the LHC, the so-called Mueller–Navelet jets, has been one of the most studied reactions so far. Interesting observables associated to this process are the azimuthal correlation momenta, showing a very good agreement with experimental data at the LHC. However, new BFKL-sensitive observables should be considered in the context of the LHC physics program. With the aim the to further and deeply probe the dynamics of QCD in the Regge limit, we give phenomenological predictions for four distinct semi-hard process. On one hand, we continue the analysis of reactions with two objects identified in the final state (i) by addressing open problems in the Mueller– Navelet sector and (ii) by studying the inclusive dihadron production in the full NLA BKFL accuracy. Hadrons can be detected at the LHC at much smaller values of the transverse momentum than jets, allowing us to explore an additional kinematical range, complementary to the one studied typical of Mueller– Navelet jets. Furthermore, this process permits to constrain not only the parton distribution functions for the initial proton, but also the parton fragmentation functions describing the detected hadron in the final state. On the other hand, we show how inclusive multi-jet production processes allow us to define new, generalised and suitable BFKL observables, where transverse momenta and rapidities of the tagged jets, well separated in rapidity from each other, appear in new combinations. We give the first phenomenological predictions for the inclusive three-jet production, encoding the effects of higher-order BFKL corrections. Then, making use of the same formalism, we present the first complete BFKL analysis for the four-jet production.Item Nano materials and innovative laser-based accelerators for cultural heritage(2017-07-12) Veltri, Simona; Pantano, Pietro; Bonanno, Assunta; Antici, PatrizioUniversità della Calabria, Dipartimento di FisicaItem TiO2 nanotubes in nanotechnologies(2010-12-14) Jimenez, Leticia; Versace, CarloItem 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, GiovanniIn 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.Item Critical properties of 2D Z(N) vector models for N > 4(2011-12-19) Cortese, Gennaro; Papa, A.; Falcone, G.