Search results for "kinetics"
showing 10 items of 2224 documents
Kinetics of the electronic center annealing in Al2O3 crystals
2018
Authors are greatly indebted to A. Ch. Lushchik, V. Kortov, M. Izerrouken and R.Vila for stimulating discussions. This work has been carried out within the framework of the Eurofusion Consortium and has received funding from the Euroatom research and training programme 2014–2018 under grant agreement No 633053 . The views and opinions expressed herein do not necessarily reflect those of the European Commission. The calculations were performed using facilities of the Stuttgart Supercomputer Center (project DEFTD 12939 ).
ESR and PL centers induced by gamma rays in silica
1996
We have studied the point defects created by γ irradiation in various types of commercial silica glasses, including both natural and synthetic samples, with different OH content, in the low dose regime (0.05–100 Mrad). We found that the growth rate of E′ centers depends strongly on the silica type, ranging from 2 × 1015 cm−3 Mrad−1 to 6 × 1017 cm−3 Mrad−1. Samples of natural silica are rather susceptible to γ ray exposure, as E′ concentration saturates (typically 5 × 1017 cm−3) for doses as low as a few Mrads. For both synthetic and natural samples, the radiation hardness is higher in wet than in dry silica. Moreover, we found a strict correlation between the concentration of E′ centers and…
Time-resolved luminescence of YAG:Ce and YAGG:Ce ceramics prepared by electron beam assisted synthesis
2020
Abstract The luminescence characteristics of YAG:Ce and YAGG:Ce ceramic phosphors produced by electron beam assisted synthesis have been investigated. The obtained emission and decay kinetics characteristics have been compared with those for commercial phosphors synthesized by conventional methods and showed good qualitative and quantitative correspondence. In our opinion, the used electron-beam-assisted synthesis method could be considered as a perspective production method of high refractory multicomponent oxide ceramics.
Transient color centers in GGG crystals
2002
Electron pulse induced absorption and their decay kinetics have been investigated in samples of GGG crystals with different starting absorption spectra. It is shown that for all samples there appears a wide transient absorption (TA) band with two maxima in the region 14,000-17,000 v cm m 1 and 22,000-26,000 v cm m 1 . TA decay kinetics measurements in 14,000 v cm m 1 and 22,000 v cm m 1 are two-exponential (with half-time order several tens and several hundreds ns). Analyzing the obtained results, we can suppose that low and high energy TA bands are connected with the F + (or O m ) and F transient color centers (TCC) respectively.
The kinetics of defect aggregation: A novel lattice formalism
1995
We introduce a stochastic model for the A + B → O reaction on a discrete lattice. The system may include mono- and bimolecular steps (i. e. reaction and diffusion steps). The resulting infinite chain of equations is truncated at a certain level via a modified Kirkwood approximation.
Theoretical simulations of I-center annealing in KCl crystals
1995
Abstract This paper focus on theory of diffusion-controlled annealing of the most mobile radiation-induced defects—I centers—in KCl crystals. The kinetics of annealing of pairs of close oppositely charged defects—α-I centers (arising as a result of the tunnelling recombination of primary Frenkel defects—F and H centers) and F-I centers (when H center trap electrons) is calculated taking into account defect diffusion and Coulomb/elastic interaction. Special attention is paid to the conditions under which multi-stage annealing arises; theoretical results are compared with the relevant experimental data.
Solid-state NMR investigation on the interactions between a synthetic montmorillonite and two homopolypeptides.
2006
Abstract Interactions of two homopolypeptides (polylysine and polyglutamic acid) with a synthetic montmorillonite were studied by 1H MAS, 1H–27Al HETCOR and 1H–13C CP-MAS NMR experiments. 1H–27Al HETCOR with 1H spin-diffusion NMR appears to be a powerful probe for the identification of the polypeptide fragments, which interact with the montmorillonite interlayer surfaces. In particular, selective interactions were observed between the polypeptide side-chains and the montmorillonite octahedral aluminum atoms. 1H–13C CP-MAS NMR experiments were used to assess the dynamics of the two polypeptides through the measurement of the t1/2 characteristic time of selected carbons. Results indicate that…
Time resolved photoluminescence associated with non-bridging oxygen hole centers in irradiated silica
2008
Abstract We report time resolved photoluminescence spectra of irradiated silica under excitation with a laser tunable in the visible and UV range. The investigated samples exhibit the emission band at 1.9 eV associated with non-bridging oxygen hole centers, whose spectral and kinetics properties do not depend on the kind of irradiation (γ, β and neutrons). The 1.9 eV luminescence decay follows a multi-exponential curve with a characteristic lifetime that increases from 8.9 μs to 10.4 μs on increasing the emission energy. This dependence accounts for the blue-shift of the emission band during its decay and is interpreted as due to the inhomogeneous properties of silica leading to a distribut…
The Influence of a Magnetic Field on the Formation of Corrosion Defects in Selected Metals and Steels, Analysed Using Positron Annihilation Method
2014
The method of positron lifetime measurement was used to analyse the in uence of a magnetic eld on the kinetics of corrosion defect formation in near-surface layers of iron, titanium as well as S20 and S0H18N9 steel grades. The listed metals, which belong to ferroand paramagnetic materials, have di erent sensitivity to corrosion. It was found that not only the presence of a magnetic eld, but also its direction in uence the dimensions and the concentration of defects formed during corrosion.
Nucleation kinetics in deionized charged colloidal suspension
2011
A systematic experimental study on the nucleation, crystallization and crystal-growth of one-componentcharged colloidal particles (122 nm diluted in pure water with densities between 0.5 μm−3bnpb5 ...