Search results for "Faces"
showing 10 items of 3167 documents
The effect of hydration layers on the anodic growth and on the dielectric properties of Al2O3 for electrolytic capacitors
2014
Hydrous films were grown on high purity and cubicity Al foils for electrolytic capacitors in deionized water, ethylene glycol - deionized water and in glycerol - deionized water for different immersion times. According to the X-ray diffraction patterns the hydration treatment allowed to grow a pseudo boehmite layer on Al surface whose morphology is appreciably affected by the bath composition. Capacitance measurements and photoelectrochemical findings suggest that a more compact barrier layer forms during the immersion in alcohol containing solutions. The hydration in water allowed to save energy and to prepare more blocking oxide films. The beneficial effect of hydration in hot water on th…
First operation of the superconducting Darmstadt linear electron accelerator as an energy recovery linac
2020
The superconducting Darmstadt linear electron accelerator (S-DALINAC) has been operated as an energy recovery linac (ERL) for the first time. The S-DALINAC is a recirculating superconducting radio-frequency (SRF) accelerator and had been upgraded with an additional recirculation beamline. It features a path length adjustment system that provides a freedom of choice of 360\ifmmode^\circ\else\textdegree\fi{} for the rf phase difference between the electron bunches recirculated through the new beamline and the phase of the accelerating ${\mathrm{TM}}_{010}$ mode of the oscillating electromagnetic field in the SRF cavities of the accelerator. A choice of around 180\ifmmode^\circ\else\textdegree…
Simultaneous determination of carrier lifetime and electron density-of-states in P3HT:PCBM organic solar cells under illumination by impedance spectr…
2010
We report new insights into recombination kinetics in poly(3-hexylthiophene):methanofullerene (P3HT:PCBM) bulk heterojunction (BHJ) solar cells, based on simultaneous determination of the density of states (DOS), internal recombination resistance, and carrier lifetime, at different steady states, by impedance spectroscopy. A set of measurements at open circuit under illumination was performed aiming to better understand the limitations to the photovoltage, which in this class of solar cells remains far below the theoretical limit which is the difference between the LUMO level of PCBM and the HOMO of P3HT (∼1.1 eV). Recombination kinetics follows a bimolecular law, being the recombination ti…
Study of the annealing conditions and photoelectrochemical characterization of a new iron oxide bi-layered nanostructure for water splitting
2016
Iron oxide nanostructures have emerged as promising materials for being used as photocatalysts for hydrogen production due to their advantageous properties. However, their low carrier mobility and short hole diffusion length limit their efficiency in water splitting. To overcome these drawbacks, in the present study, we synthetized a new hematite (alpha-Fe2O3) bi-layered nanostructure consisting of a top nanosphere layer and a nanotubular underneath one by electrochemical anodization. Annealing parameters such as temperature, heating rate and atmosphere were studied in detail in order to determine the optimum annealing conditions for the synthetized nanostructure. The obtained new bi-layere…
SURFACE EFFECTS ON THE GROWTH OF SOLUTION PROCESSED PENTACENE THIN FILMS
2008
13,6-N-Sulfinylacetamidopentacene (SAP) has been transferred on solid substrates both by water-rich environment and organic solvents without altering his chemical structure. Thermal conversion of SAP to pentacene leads to crystals showing similar features of vacuum-sublimated pentacene both in the bulk and thin-film phases. The thin-film phase is strongly affected by the substrate surface properties. Low energy Si-CH3 rich surfaces allow for the formation of compact micrometric crystals following a Volmer-Weber like growth with orientation suitable for field-effect carrier mobility. Screw dislocations along with straight edges are found on these systems as an indication of a loose interlaye…
Ab Initio Calculations of the Transfer and Aggregation of F Centers in CaF2
2012
The F center and R center in CaF2 crystals have been studied by using density functional theory (DFT) with a hybrid B3PW description of exchange and correlation. Our calculations show that the F-center diffusion barrier is equal to 1.67 eV. During the F-center transfer, the trapped electron is more delocalized than that in the regular F-center case, and the gap between defect level and CB in the α-spin state decreases. The surface F-center investigation shows the trend of F centers to locate near the surface. The association energy calculations of R centers indicate stable aggregations of isolated F centers. During the F-center aggregation, a considerable covalency forms between two neighbo…
Electron Transfer from the Singlet and Triplet Excited States of Ru(dcbpy)2(NCS)2into Nanocrystalline TiO2Thin Films
2002
Time-resolved absorption spectroscopy was used to study the femtosecond and picosecond time scale electron injection from the excited singlet and triplet states of Ru(dcbpY)(2)(NCS)(2) (RuN3) into titanium dioxide (TiO2) nanocrystalline particle film in acetonitrile. The fastest resolved time constant of similar to30 fs was shown to reflect a sum of two parallel ultrafast processes, nonergodic electron transfer (ET) from the initially excited singlet state of RuN3 to the conduction band of TiO2 and intersystem crossing (ISC). The branching ratio of 1.5 between the two competing processes gives rate constants of 1/50 fs(-1) for ET and 1/75 fs(-1) for ISC. Following the ultrafast processes, a…
First-principles calculations for SrTiO3() surface structure
2002
As a continuation of our recent abinitio calculations of SrTiO 3(1 0 0) surface relaxation for the two different terminations (SrO and TiO2) [Phys. Rev. B 64 (2001) 23417], we analyze here their electronic structures (band structure, density of states, and the electronic density redistribution with emphasis on the covalency effects). We compare results of abinitio Hartree–Fock method with electron correlation corrections and density functional theory with different exchange-correlation functionals, including hybrid (B3PW, B3LYP) exchange techniques. Our results are also compared with previous abinitio plane-wave local density approximation calculations and experiments when availab le. Consi…
Heterovalent BiIII/PbII ionic substitution in one-dimensional trimethylsulfoxonium halide pseudo-perovskites (X = I, Br)
2021
We report on the synthesis and characterization of novel lead and bismuth hybrid (organic-inorganic) iodide and bromide pseudo-perovskites (ABX3) containing the trimethylsulfoxonium cation (CH3)3SO+ (TMSO) in the A site, Pb/Bi in the B site, and Br or I as X anions. All of these compounds are isomorphic and crystallize in the orthorhombic Pnma space group. Lead-based pseudo-perovskites consist of one-dimensional (1D) chains of face-sharing [PbX6] octahedra, while in the bismuth-based ones, the chains of [BiX6] are interrupted, with one vacancy every third site, leading to a zero-dimensional (0D) local structure based on separated [Bi2I9]3- dimers. Five solid solutions for the iodide with di…
Graph-based analysis of ethylene glycol decomposition on a palladium cluster
2017
The ethylene glycol, CH2OH-CH2OH, decomposition mechanism, occurring on a subnanometric palladium cluster shaped by 12 atoms, was investigated by means of density functional theory. Different reaction routes were identified leading to H2 and CO. The whole reaction network was analyzed, framing the results within the graph theory. The possible decomposition pathways were discussed and compared, allowing one to draw a whole picture of all the parallel, possibly competitive, routes that starting from CH2OH-CH2OH originate H2 and CO.