Search results for "doping"
showing 10 items of 801 documents
Water Adsorption on Clean and Defective Anatase TiO2 (001) Nanotube Surfaces: A Surface Science Approach
2018
We use ab initio molecular dynamics simulations to study the adsorption of thin water films with 1 and 2 ML coverage on anatase TiO2 (001) nanotubes. The nanotubes are modeled as 2D slabs, which consist of partially constrained and partially relaxed structural motifs from nanotubes. The effect of anion doping on the adsorption is investigated by substituting O atoms with N and S impurities on the nanotube slab surface. Due to strain-induced curvature effects, water adsorbs molecularly on defect-free surfaces via weak bonds on Ti sites and H bonds to surface oxygens. While the introduction of an S atom weakens the interaction of the surface with water, which adsorbs molecularly, the presence…
First principles modeling of 3d-metal doped three-layer fluorite-structured TiO2 (4,4) nanotube to be used for photocatalytic hydrogen production
2017
This study has been supported by the EC ERA.Net RUS Plus project No. 237 WATERSPLIT, Russian Basic Research Foundation No. 16-53-76019, and additionally by the IMIS2 Program (Latvia). The authors are also indebted to R. A. Evarestov and O. Lisovski for stimulating discussions as well as to A. Chesnokov for technical assistance.
The Effect of Ni Doping on the Performance and Electronic Structure of LSCF Cathodes Used for IT-SOFCs
2018
We investigated the effect of nickel doping on the electronic structure and performance of nanostructured La0.6Sr0.4Co0.2Fe0.8-0.03Ni0.03O3-delta prepared by the one-pot sol gel method. The commercial undoped La0.6Sr0.4Co0.2Fe0.8O3-delta (ISCF0.8) was used as reference. Moreover, for comparison, Ni (3 mol %) was deposited by wetness impregnation over the La0.6Sr0.4Co0.2Fe0.8O3-delta. We show by in situ X-ray absorption spectroscopy at 900 degrees C under air flow that nickel enters the B perovskite site of the material and favors the stabilization of the cobalt oxidation state, as evidenced by the delay in the decrease of the average Co valence with respect to undoped samples. Our results a…
F centre production in CsI and CsI–Tl crystals under Kr ion irradiation at 15 K
2000
Abstract We present results of simultaneous in situ luminescence and optical absorption studies in scintillator CsI and CsI–Tl crystals, exposed to very dense electronic excitations induced by 86Kr ions (8.63 MeV/amu). Irradiation at 15 K leads to the formation of the prominent F absorption band. In addition, several other features of the broad absorption between exciton and F bands were ascribed to an anion vacancy, α centre (240 nm), self-trapped hole, Vk centre (410 nm) and interstitials, H centres (560 nm). We have found that low doping of thallium (∼1017 cm−3) causes the F centre formation to proceed more rapidly than in pure crystal. On the other hand, we were not able to create any a…
Synchrotron radiation studies on luminescence of Eu2+-doped LaCl3 microcrystals embedded in a NaCl matrix
2012
Abstract LaCl3:Eu2+ microcrystals dispersed in the NaCl matrix have been obtained in the NaCl–LaCl3(1 mol.%)–EuCl3(0.1 mol.%) crystalline system. The low-temperature luminescent properties of these microcrystals have been studied upon the VUV and UV excitation by the synchrotron radiation. The spectroscopic parameters as well as decay time constants of Eu2+-doped LaCl3 host have been established. The excitation mechanism of divalent europium centers through energy transfer and reabsorption is discussed.
Radiation displacement defect formation in some complex oxide crystals
2000
The work is devoted to an analysis of the formation processes of radiation displacement defects (RDDs) and color centers (CCs) under irradiation of complex oxide crystals. The results of the displacement process simulation as well as the analysis of the RDDs and CCs accumulation kinetics in some complex oxide crystals are presented. New experimental results on additional absorption spectra induced by neutron irradiation of LiNbO3 (LNO) crystals doped with Fe and Cr and YAlO3 (YAP) crystals doped with Nd and Er as well are presented. Dose dependencies are compared and their peculiarities are discussed. ” 2000 Elsevier Science B.V. All rights reserved.
Germanium Doped CHxMicroshells for LMJ Targets
2011
AbstractAt the CEA Laser “Megajoule” facility, amorphous hydrogenated carbon (a-C:H or CHx) is the nominal ablator used to achieve inertial confinement fusion experiments. These targets are filled with a fusible mixture of deuterium-tritium in order to perform ignition.Since the achievement of ignition greatly depends on the physical properties of the shell, there must be precise control of thicknesses, doping concentration, and roughness. Experimental devices associated with suitable characterizations are described in this paper. The tolerances and yields for each specification are also presented. Some specifications are largely reached; high-frequency surface roughness due to isolated sur…
Influence of <formula formulatype="inline"><tex Notation="TeX">${\hbox{O}}_2$</tex></formula>-Loading Pretreatment on the Rad…
2014
We investigated the impact of an oxygen preloading on pure-silica-core or fluorine-doped-core fiber responses to high irradiation doses (up to 1 MGy (SiO 2 )). Oxygen enrichment was achieved through a diffusion-based technique, and the long-term presence of O 2 molecules was confirmed by micro-Raman experiments. Online radiation induced attenuation (RIA) experiments were carried out in both the pristine and the O 2 -loaded optical fibers to investigate the differences induced by this pretreatment in the UV and visible ranges. Contrary to results recently published on the positive impact of O 2 on infrared RIA, our results reveal a RIA increase with O 2 presence. Data are analyzed in order t…
Rare Earth Activated Oxyfluoride Glasses and Glass-Ceramics for Scintillation Applications
2012
Oxyfluoride glasses 49SiO2·6Al2O3·24Li2O·20LaF3 activated with Tb, Ce, Eu have been synthesized and studied. After heating at 580°C and 750°C crystalline phases were obtained. The samples were studied by DTA (Differential thermal analyzer), CL (cathodoluminescence), XRD (X-ray diffraction), SEM (scanning electron microscope), EDS (energy dispersive x-ray spectroscopy) methods. We found out that presence of crystalline phase enhances the CL of Tb activated samples significantly; whereas, the shortest decay time of 0.29 μs has been observed for less intense Ce doped glass sample.
Luminescence Properties of ZnO Nanocrystals and Ceramics
2008
The luminescence excitation spectra, luminescence spectra and the nanosecond-scale decay kinetics were studied. The ZnO and ZnO:Al nanopowders were prepared by vaporization-condensation in a solar furnace using different raw powders: commercial, hydrothermal and those obtained by plasma synthesis. Exciton-phonon as well as exciton-exciton interaction processes in nanopowders, a bulk crystal and ZnO ceramics were studied and compared. The fast decay and low afterglow intensity of ZnO nanopowders and ceramics support these materials for scintillators.