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3. Overview of radiation induced point defects in silica-based optical fibersSylvain Girard, Antonino Alessi, Vincenzo De Michele, Youcef Ouerdane, A. Boukenter, Adriana Morana, Nicolas Richard, Philippe Paillet, Marco Cannas, Simonpietro Agnello, Imène Reghioua, Blaz Winkler, Layla Martin-Samos, Luigi Giacomazzi, Diego Di Francesca, Thierry Robin, 2019, pregledni znanstveni članek Ključne besede: optical fibers, point defects, radiation-induced attenuation, GLPC, NBOHC, STH, ODC, P-doping, Ge-doping, Al-doping
Objavljeno v RUNG: 09.05.2019; Ogledov: 4185; Prenosov: 0
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4. Role of Surface Cu-O-Zr Sites in the Photocatalytic Activity of TiO2 Nanoscale ParticlesOlena Pliekhova, Iztok Arčon, Nataša Novak Tušar, Urška Lavrenčič Štangar, 2016, objavljeni povzetek znanstvenega prispevka na konferenci Ključne besede: Photocatalysis, Titanium dioxide, Copper, Zirconia, co-doping, EXAFS, XANES
Objavljeno v RUNG: 23.08.2017; Ogledov: 5523; Prenosov: 0
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6. Correlations between photocatalytic activity and chemical structure of Cu-modified TiO2–SiO2 nanoparticle compositesT. Čižmar, Urška Lavrenčič Štangar, Iztok Arčon, 2016, izvirni znanstveni članek Opis: Copper-modified TiO2–SiO2photocatalysts were prepared by sol–gel method based on organic copper,silicon and titanium precursors. Copper concentration varied from 0.1 to 3.0 mol%. A widely appliedmodel reaction of photocatalytic oxidation of terephtalic acid (TPA) in water solution was used in order toevaluate the catalytic activities of elaborated samples. The crystal structures of the titania components ofall tested titania–silica species were studied using XRD analysis. The influence of Cu2+cation incorporationon the crystal structure of titania, as well as the chemical states and the neighbouring structures of coppercations, have been examined by means of Cu K-edge EXAFS and XANES analysis. The experimental datashow that there is a ten times increase in photocatalytic activity when TiO2–SiO2matrix is modified with0.1 mol% of Cu. It can be supposed that an enhancement of photocatalytic activity of low-concentratedcopper-modified titania–silica nanocomposites is probably due to a close attachment of Cu2+cationsto the surfaces of photocatalytically active TiO2nanoparticles. In this case, Cu2+cations may possiblyact as free electron traps reducing the intensity of recombination between opposite free charge carriers(electrons, holes) available at the photocatalyst’s surface.
Ključne besede: Cu-modified TiO2–SiO2photocatalysts, Titanium dioxide, Metal doping, Cu K-edge XANES, EXAFS, Photocatalytic activitya
Objavljeno v RUNG: 17.01.2017; Ogledov: 6130; Prenosov: 0
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7. Donor doping of K0.5Na0.5NbO3 ceramics with strontium and its implications to grain size, phase composition and crystal structureJitka Hreščak, Goran Dražić, Marco Deluca, Iztok Arčon, Alojz Kodre, M. Dapiaggi, Tadej Rojac, Barbara Malič, Andreja Benčan, 2017, izvirni znanstveni članek Opis: In this study, the particular effects of A-site donor doping in a lead-free piezoceramic material K0.5Na0.5NbO3 (KNN) doped with Sr2+, i.e., the crystal-structure change, the secondary-phase formation and the grain-size decrease, were investigated. The already-reported causes of these effects upon doping KNN were critically discussed and a mechanism of the effects’ formation was suggested and experimentally supported with advanced analytical methods. Extended X-ray absorption fine structure (EXAFS) analyses proved that the Sr occupies the perovskite A-sublattice, and locally modifies the KNN monoclinic structure to cubic. With the help of Sr K-edge EXAFS and wavelength-dispersive X-ray spectroscopy, the Sr was found to be homogenously distributed in the KNN perovskite lattice with 0.5, 1 and 2% Sr and no Sr segregation on the nano level was found in any of the studied samples with transmission electron microscopy. Introducing Sr into the A-sublattice, as well as accounting for the charge-compensating A-site vacancies in the starting composition, causes increasing lattice disorder and microstrain, as determined from a Rietveld refinement of the synchrotron X-ray diffraction data. Above 2% Sr the system segregates the A-site vacancies in a secondary phase in order to release the chemical pressure, as revealed by Raman spectroscopy. All these effects result in an increasing number of low-angle grain boundaries that limit the grain growth and finally lead to a significant grain-size decrease.
Ključne besede: perovskite, potassium sodium niobate, donor doping, cation vacancies
Objavljeno v RUNG: 17.01.2017; Ogledov: 5772; Prenosov: 329
 Celotno besedilo (2,11 MB) |
8. Photocatalytic Activity of Zirconium- and Manganese- Codoped Titania in Aqueous Media: The Role of the Metal Dopant and its Incorporation SiteO. L. Pliekhov, Iztok Arčon, Nataša Novak Tušar, Urška Lavrenčič Štangar, 2016, izvirni znanstveni članek Opis: The development of efficient TiO2-based photocatalysts for
water treatment is mainly performed by doping with transition
metals or by establishing junctions between different phases,
metal–semiconductor or semiconductor–semiconductor. We
present, for the first time, the synthesis of Zr- and Mn-modified
TiO2 by a redesigned sol–gel technique that allows the formation
of heterometallic bridges on the TiO2 surface. Cations of
the doping metals are located in the pores of mesoporous
anatase and attached to the crystalline TiO2 walls. The presence
of the Zr enhances the photoactivity of the TiO2 catalyst.
However, the introduction of Mn decreases the photocatalytic
efficiency in a nonadditive manner. The inhibition effect was
assigned to the side reaction between hydroxyl radicals and
Mn ions. The fact that Mn effectively scavenges the hydroxyl
radicals and, consequently, inhibits the whole oxidation process
is direct proof that hydroxyl radicals are the main reactive
species in the photocatalytic oxidative processes on TiO2 surfaces
in aqueous media and the process of COH generation is the
rate-determining step, which was confirmed using a method
based on the decolorization of a commercial dye Bezaktiv Blau
in a reaction with Fenton’s reagent as a source of hydroxyl radicals.
Ključne besede: doping, manganese, oxidation, X-ray absorption spectroscopy, zirconium
Objavljeno v RUNG: 21.07.2016; Ogledov: 4924; Prenosov: 0
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10. Gamma and x-ray irradiation effects on different Ge and Ge/F doped optical fibersAntonino Alessi, Sylvain Girard, Imene Reghioua, Mattia Fanetti, Diego Di Francesca, Simonpietro Agnello, Marco Cannas, Claude Marcandella, Layla Martin-Samos, N. Richard, Aziz Boukenter, Youcef Ouerdane, 2015, izvirni znanstveni članek Ključne besede: optical fibers, Germanium, doping, cathodoluminescence, irradiation effect
Objavljeno v RUNG: 11.04.2016; Ogledov: 6586; Prenosov: 0
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