Repozitorij Univerze v Novi Gorici

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11.
Dislocation properties of coesite from an ab-initio parametrized interatomic potential
Sandro Scandolo, Philippe Carrez, Luigi Giacomazzi, Patrique Cordier, 2011, izvirni znanstveni članek

Najdeno v: ključnih besedah
Ključne besede: coesite, ab-initio, dislocations, silica
Objavljeno: 15.10.2018; Ogledov: 326; Prenosov: 0
.pdf Polno besedilo (1,83 MB)

12.
Photoactivated processes in optical fibers: generation and conversion mechanisms of twofold coordinated Si and Ge atoms
Nicolas Richard, Stefano De Gironcoli, Antonino Alessi, Sylvain Girard, A. Boukenter, Youcef Ouerdane, Layla Martin-Samos, Luigi Giacomazzi, 2017, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...ODC(II), silica, color centers, first-principles, twofold Si, GLPC...
Ključne besede: ODC(II), silica, color centers, first-principles, twofold Si, GLPC
Objavljeno: 15.10.2018; Ogledov: 450; Prenosov: 0
.pdf Polno besedilo (1,39 MB)

13.
Accelerating GW calculations with optimal polarizability basis
Geoffrey Stenuit, Stefano Baroni, Nicola Marzari, Xiaofeng Qian, Luigi Giacomazzi, Paolo Umari, 2011, samostojni znanstveni sestavek ali poglavje v monografski publikaciji

Najdeno v: ključnih besedah
Povzetek najdenega: ...GW, silicon nitride, DFT, silica, electronic structure...
Ključne besede: GW, silicon nitride, DFT, silica, electronic structure
Objavljeno: 19.10.2018; Ogledov: 384; Prenosov: 0
.pdf Polno besedilo (274,33 KB)

14.
Radiation induced color centers in Silica: a first-principles investigation.
Nicolas Richard, Layla Martin-Samos, Luigi Giacomazzi, 2013, objavljeni znanstveni prispevek na konferenci

Najdeno v: ključnih besedah
Ključne besede: Silica, EPR, E' centers, ODC
Objavljeno: 22.10.2018; Ogledov: 396; Prenosov: 0
.pdf Polno besedilo (130,79 KB)

15.
First principles vibrational spectra of tetrahedrally-bonded glasses: sio2, geo2 and gese2
Luigi Giacomazzi, 2007, doktorska disertacija

Najdeno v: ključnih besedah
Povzetek najdenega: ... Silica, Germania, Chalcogenide Glasses, Vibrational Spectra, Raman Spectroscopy,...
Ključne besede: Silica, Germania, Chalcogenide Glasses, Vibrational Spectra, Raman Spectroscopy, Infrared, First-principles
Objavljeno: 31.01.2019; Ogledov: 467; Prenosov: 0
.pdf Polno besedilo (2,03 MB)

16.
Investigating silica from first-principles
Luigi Giacomazzi, druga izvedena dela

Opis: Silica (SiO2 ) is a prototypical binary compound showing a complex phase diagram. It is the most abundant mineral in the Earth’s crust, and it has many important technological applications. From a theoretical point of view, SiO2 is a benchmark requiring both accurate atomistic models and a multi-scale approach. As an example of the capabilities of state- of-the-art theoretical modeling, we discuss the vibrational spectra of vitreous SiO2 with particular attention to the information that these spectra can provide on the medium-range structure of the oxide network. Then, as an example of multi-scale approach we present our work on dislocations in coesite within the framework of the Peierls-Nabarro model.
Najdeno v: ključnih besedah
Ključne besede: silica, coesite, dislocations, Peierls-Nabarro
Objavljeno: 08.04.2019; Ogledov: 258; Prenosov: 0
.pdf Polno besedilo (16,44 KB)

17.
EuroSLAB - The rheology of the subducting slab and mantle
Luigi Giacomazzi, Sandro Scandolo, 2011, končno poročilo o rezultatih raziskav

Opis: The aim of this Individual Project was to study the microscopic phenomena of deformation in mantle minerals by means of atomistic modeling. Understanding such mechanisms and determining their relative importance in different minerals and in the wide range of pressure and temperature found in the mantle, is a prerequisite for any interpretation of deformation experiments, of texture modeling, and of their geophysical implications. The project was approved for funding in mid 2006, and was carried out in large part in collaboration with a postdoctoral fellow funded by CNR (Luigi Giacomazzi), whose fellowship ended on December 15, 2009.
Najdeno v: ključnih besedah
Povzetek najdenega: ...gypsum, coesite, silica, dislocations, rheology...
Ključne besede: gypsum, coesite, silica, dislocations, rheology
Objavljeno: 08.04.2019; Ogledov: 232; Prenosov: 0
.pdf Polno besedilo (2,04 MB)

18.
OXYGEN-EXCESS RELATED DEFECTS IN SiO2-BASED MATERIALS: COUPLING THEORY AND EXPERIMENTS
Blaž Winkler, doktorska disertacija

Opis: This work is primarily focused on application of standard first-principle computational approaches to model oxygen excess related point defects in amorphous silica. Atomic models with their respective electronic and optical properties are explored together with some conversion mechanisms between defect models. The first chapter overviews extensive literature about the already known properties of oxygen related defects. Second chapter briefly introduces main methods that have been used in this research, in particular Density Functional Theory (DFT) as energy and force engine with short description of minimal energy path (MEP) algorithm used for modeling chemical/migration reactions, GW approximation for charged electronic excitations (band structure) and Bethe-Salpeter Equation (BSE) for neutral excitations (optical absorption and excitonic structure including electron hole interaction). The third chapter is devoted to the presentation of results. Thanks to the calculation of optical properties of peroxy bridge (POL), a correlation has been found between structural disorder, specifically dihedral angle dispersion, and low coupling with light, which has been identified as main reason why no clear absorption bands have been assigned to the POL. Structure and stability of some other defects, like interstitial ozone molecule (ozonyl) and dioxasilirane (silicon analogy of dioxirane), have been studied. These defects are usually not considered as most important species, however their calculated formation energies are lower compared to some known defects, which indicates they might be present in silica. From a detailed study on possible reaction mechanisms, it has been found that ozonyl might be one of the most important intermediate steps for oxygen exchange reactions. Results also show that dioxasilirane can be spontaneously created during the interaction of oxygen with lone pair defects. By exploring different reactions between oxygen and pre-existing oxygen deficiency centers (ODCs), calculations predict two kinds of passivation behaviors: single-barrier reversible mechanisms with the formation of dioxasilirane-like groups, for which the network keeps the memory of the precursory lone pair defects, and single or multiple-barrier mechanisms, for which the network loses its memory, either because of the high reverse barrier or because of a reconstruction. Final part of this research has been devoted to experimental characterization of the response and tolerance of optical fibers loaded with oxygen under irradiation. These include experiments on commercial fiber along with canonical samples (Optical fibers developed with the intention of studying correlations between different fabrication parameters, dopant/impurity concentration and doping concentrations). Studied fibers also include rare-earth doped fibers.
Najdeno v: ključnih besedah
Povzetek najdenega: ...oxygen excess related point defects in amorphous silica. Atomic models with their respective electronic and...
Ključne besede: Silica, DFT, GW-approximation, Bethe-Salpeter equation, NEB, defect, oxygen, oxygen excess centers, oxygen deficiency centers, optical absorption, optical fibers, radiation induced attenuation.
Objavljeno: 07.05.2019; Ogledov: 427; Prenosov: 30
.pdf Polno besedilo (13,18 MB)

19.
20.
Photoactive nanocomposite thin films on glass and thermosensitive substrates
Nives Vodišek, 2019, doktorska disertacija

Opis: Photocatalysis is a well-known process for the last few decades; it is predominantly used for water and air purification, but also for self-cleaning and antibacterial surfaces. The photocatalytic process is one of the advanced oxidation processes, where semiconductors are mainly used as photocatalysts. The most known and used semiconductor is nanosized titania, which can non-selectively decompose organic matters. One of the side effects of nano TiO2 under UV irradiation is photoinduced hydrophilicity, which furthermore improves the self-cleaning effect. The main drawback of TiO2 is that for its activation UV light is needed, which represents only 5 percent of the solar spectrum. Consequently, actinic irradiance power is low and the response of photocatalyst is limited. Novel approaches are being introduced to improve TiO2 response to visible light such as doping, coupling, modification of surface morphology and others. The thesis consists of five principal chapters. The first chapter is focused on a short literature review and explanation of some basic terms and principles that are related to this thesis. The aim of the research was to prepare transparent photocatalytically active thin films on glass and thermosensitive substrates. Four thermosensitive substrates were used: polyvinyl chloride (PVC) foil, polymethyl methacrylate (PMMA) sheet and polyester (PES) fabric coated with a polyvinyl and acrylic coating, with (D1) or without (D2) an additional polyvinylidene fluoride topcoat. The synthesis of films was modified with the introduction of zirconium aiming at improving the photocatalytic activity of the TiO2 films, and the final films had a SiO2 phase present for increased mechanical robustness. The third chapter is dedicated to the experimental part of the thesis. The detailed process of synthesis is described. The sol-gel process was used to prepare initial Ti-Zr sols, colloidal aqueous solutions with TiO2 and ZrO2 nanoparticles derived from titanium and zirconium alkoxides. The four different Ti-Zr sols were prepared with 0, 5, 10 and 20 molar % of Zr according to Ti. The depositing solution was prepared by mixing Ti-Zr sol, SiO2 sol binder, 1-propanol and 2-propoxyethanol, and then thin films were deposited by dip-coating technique. After the deposition, samples did not require high-temperature calcination since the photocatalytic anatase phase was present already after drying the deposited layers. Coated glass slides were put into a furnace at 150 °C, while samples on thermosensitive substrates were just treated by a heat gun. Samples in powder and thin film form were characterized by UV-Vis, FTIR-ATR and laser beam deflection spectroscopy, X-ray diffraction, scanning electron microscopy and thermal analysis. One of the main aspects of the photocatalyst is its activity. Photocatalytic activity of the thin films was determined, either quantitatively by the formation of fluorescent hydroxyterephthalic acid, one of the first degradation products of terephthalic acid deposit, or qualitatively by a visual-based method where degradation of resazurin ink was observed. Two additional methods were used on glass samples, electron paramagnetic resonance, and degradation of methyl stearate by observing the change in water contact angle under UVA irradiation. Mechanical stability of films on various substrates is an essential factor, describing how successful was immobilization of the photocatalytic materials on the substrate. It was determined by the pencil hardness test, i.e., Wolff-Wilborn method. In the fourth chapter, titled “Results and Discussion,” the most important part of the thesis is placed. Materials characterization and associated discussion of the results are divided into three major parts: i) powder samples characterization; ii) characterization of thin films on a glass substrate, and iii) characterization of films on thermosensitive substrates. In the conclusions, the main findings of the Ph.D. research work are summarized. One of our initial hypotheses was disapproved, thin films were not more active with a higher content of zirconium. However, they were more durable. All the obtained films were transparent and photoactive, despite the low-temperature synthesis procedure. Besides commonly used glass substrate, immobilization on thermosensitive substrates was also successful.
Najdeno v: ključnih besedah
Povzetek najdenega: ...nanomaterials, PES, photocatalysis, PMMA, PVC, self-cleaning surfaces, silica, plastic substrates, thin films, titania, zirconia...
Ključne besede: glass substrate, immobilization, nanocomposite, nanomaterials, PES, photocatalysis, PMMA, PVC, self-cleaning surfaces, silica, plastic substrates, thin films, titania, zirconia
Objavljeno: 14.10.2019; Ogledov: 131; Prenosov: 8
.pdf Polno besedilo (6,23 MB)

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