scholarly journals Radiation defects in NaCl matrix with reduced lattice symmetry caused by light cation doping and elastic uniaxial deformation

2021 ◽  
Vol 61 (3) ◽  
Author(s):  
K. Shunkeyev ◽  
Zh. Ubaev ◽  
A. Lushchik ◽  
L. Myasnikova
Keyword(s):  
Elastic Deformation ◽  
Elastic Stress ◽  
Electronic Excitations ◽  
Uniaxial Deformation ◽  
Thermally Stimulated Luminescence ◽  
Absorption Bands ◽  
Radiative Relaxation ◽  
X Ray ◽  
Lattice Symmetry ◽  
Subsequent Thermal Annealing

The processes of radiation defect creation and radiative relaxation of electronic excitations under applied local or/and uniaxial elastic deformation have been studied in NaCl crystals by means of optical absorption, luminescence and thermoactivation spectroscopy methods. In NaCl:Li at 80 K, X-ray-induced absorption bands peaked around 3.35 and 4.6 eV have been detected and ascribed to interstitial halide atoms located nearby Li impurity cations, HA(Li) centres. Subsequent thermal annealing of HA(Li) centres leads to the formation of polyhalide centres responsible for the absorption band at 5.35 eV. In an X-irradiated and stressed NaCl:Li crystal (degree of uniaxial elastic deformation of ε = 0.9%), the peak of thermally stimulated luminescence at ~115 K is composed of the ~2.7-eV emission appearing, in our opinion, due to the recombination of the electron, thermally released from an F′ centre, with a hole-type HA(Li) centre. The applied uniaxial elastic stress facilitates the self-trapping of anion excitons in regular regions of a NaCl lattice and impedes the energy transfer by mobile excitons to impurities/defects and, in turn, attenuates the Br-related luminescence peaked at 3.95 eV with respect to the π-emission of self-trapped excitons (~3.35 eV). The 3.95 eV emission has been detected in a natural NaCl crystal containing homologous Br impurity ions.

Thermally Activated Processes in CaMoO4 Crystals

2013 ◽  
Vol 200 ◽  
pp. 220-224 ◽  
Author(s):  
Volodymyr Tsybulskyi ◽  
Myron R. Panasyuk ◽  
Ivan M. Solskii ◽  
Viktor Rudyk ◽  
Volodymyr B. Kapustianyk
Keyword(s):  
Activation Energy ◽  
Glow Curve ◽  
High Temperature Annealing ◽  
Thermally Stimulated Luminescence ◽  
Absorption Bands ◽  
X Ray ◽  
Thermally Activated ◽  
Calcium Molybdate ◽  
Activated Processes ◽  
Thermally Stimulated Depolarization

The effect of annealing in the oxygen flow atmosphere of calcium molybdate crystals on their absorption spectra and thermally stimulated luminescence (TSL) glow curve was studied. The thermally stimulated depolarization (TSD), polarization (TSP) currents and temperature dependence of X-ray luminescence of CaMoO4were investigated in the temperature range of 100-320 K. One of the trap detected by TSL was found to disappear after high-temperature annealing of calcium molybdate single crystals. The nature of the absorption bands is discussed. The values of activation energy were calculated for the detected traps.

scholarly journals The features of deformation-stimulated RbI luminescence

2021 ◽  
Vol 5 (4) ◽  
pp. 218-228
Author(s):  
L. N. Myasnikova ◽  
A. G. Maratova ◽  
K. Sh. Shunkeyev
Keyword(s):  
Elastic Deformation ◽  
Thermal Activation ◽  
Spectral Composition ◽  
Activation Energies ◽  
Luminescence Spectra ◽  
Radiation Defects ◽  
Thermally Stimulated Luminescence ◽  
Radiative Relaxation ◽  
Interstitial Atoms

This paper studies deformation-stimulated features of radiative relaxation of self-trapped excitons and recombination assembly of exciton-like luminescence in RbI crystal. Methods of research were luminescence and thermal activation spectroscopy. The identity of the mechanism of manifestation of the X-ray luminescence, tunnel luminescence and thermally stimulated luminescence spectra were found in the elastically deformed RbI crystal, interpreted by the luminescence of self-trapped exciton, tunnel recharge of F′, VK -pairs and thermally stimulated recombination of e−, VK -centres, respectively.The temperatures of the maximum destruction peaks of thermally stimulated luminescence, their spectral composition and activation energies were determined experimentally, on the basis of which the mechanisms of recombination assembly of exciton-like luminescences in a RbI crystal were interpreted. Uniaxial elastic deformation leads to the effective formation of point radiation defects ( F′, HA, VK -centers) in comparison with an unbroken lattice, where the predominant mechanism is the association of interstitial atoms ( H -centres) with the formation of I3−-centres.

Synthesis of HTCMgFe for the degradation of indigo carmine through heterogeneous photo-Fenton treatment

MRS Advances ◽  
2020 ◽  
Vol 5 (62) ◽  
pp. 3273-3282
Author(s):  
I. Cosme-Torres ◽  
M.G. Macedo-Miranda ◽  
S.M. Martinez-Gallegos ◽  
J.C. González-Juárez ◽  
G. Roa-Morales ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Treatment Time ◽  
Uv Light ◽  
Indigo Carmine ◽  
Oh Radicals ◽  
Absorption Bands ◽  
Chromophore Group ◽  
X Ray ◽  
Catalytic Sites ◽  
Scanning Electron

AbstractThe heterogeneous catalyst HTCMgFe was used in the degradation of the IC, through the heterogeneous photo-fenton treatment, this material in combination with H2O2 and UV light degraded the dye in 30 min at pH 3. As the amount of HTCMgFe increases the degradation it was accelerated because there are more active catalytic sites of Fe2+ on the surface of the material, which generates a greater amount of •OH radicals. The HTCMgFe was characterized by infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray energy dispersive elemental analysis (EDS). The UV-vis spectrum shows that the absorption bands belonging to the chromophore group of the IC disappear as the treatment time passes, indicating the degradation of the dye.

scholarly journals Effect of tungsten disulfide nanotubes on crystallization of polylactide under uniaxial deformation and annealing

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Fausta Loffredo ◽  
Loredana Tammaro ◽  
Tiziana Di Luccio ◽  
Carmela Borriello ◽  
Fulvia Villani ◽  
...  
Keyword(s):  
Biomedical Applications ◽  
Structural Evolution ◽  
Tungsten Disulfide ◽  
Fine Tuning ◽  
Nanocomposite Films ◽  
Uniaxial Deformation ◽  
Scanning Calorimetry ◽  
X Ray ◽  
X Ray Scattering

AbstractTungsten disulfide (WS2) nanotubes (NTs) are examined here as a filler for polylactide (PLA) for their ability to accelerate PLA crystallization and for their promising biocompatibility in relevant to biomedical applications of PLA-WS2 nanocomposites. In this work, we have studied the structural and thermal properties of PLA-WS2 nanocomposite films varying the concentration of WS2 NTs from 0 (neat PLA) to 0.6 wt%. The films were uniaxially drawn at 90 °C and annealed at the same temperature for 3 and 10 min. Using wide angle x-ray scattering, Raman spectroscopy and differential scanning calorimetry, we probed the effects of WS2 NT addition on the structure of the PLA films at various stages of processing (unstretched, stretching, annealing). We found that 0.6 wt% of WS2 induces the same level of crystallinity in as stretched PLA-WS2 as annealing in neat PLA for 10 min. These data provide useful insights into the role of WS2 NTs on the structural evolution of PLA-WS2 composites under uniaxial deformation, and extend their applicability to situations where fine tuning of PLA crystallinity is desirable.

Crack Driving Force in Anisotropic Media due to Non-Elastic Deformation

2004 ◽  
Vol 261-263 ◽  
pp. 75-80
Author(s):  
G.H. Nie ◽  
H. Xu
Keyword(s):  
Elastic Deformation ◽  
Driving Force ◽  
Strain Energy ◽  
Elastic Stress ◽  
Complex Function ◽  
Crack Driving Force ◽  
Special Cases ◽  
Degree Of Anisotropy ◽  
Minimum Strain Energy ◽  
Orthotropic Media

In this paper elastic stress field in an elliptic inhomogeneity embedded in orthotropic media due to non-elastic deformation is determined by the complex function method and the principle of minimum strain energy. Two complex parameters are expressed in a general form, which covers all characterizations of the degree of anisotropy for any ideal orthotropic elastic body. The stress acting on the long side of ellipse can be considered as a crack driving force and applied in failure and fatigue analysis of composites. For some special cases, the resulting solutions will reduce to the known results.

scholarly journals Electronic Excitations and Radiation Damage in Macromolecular Crystallography

Crystals ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 273 ◽  
Author(s):  
José Brandão-Neto ◽  
Leonardo Bernasconi
Keyword(s):  
Chemical Information ◽  
X Rays ◽  
Electronic Excitations ◽  
Macromolecular Crystallography ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Structures ◽  
Successful Approach ◽  
Structural Research

Macromolecular crystallography at cryogenic temperatures has so far provided the majority of the experimental evidence that underpins the determination of the atomic structures of proteins and other biomolecular assemblies by means of single crystal X-ray diffraction experiments. One of the core limitations of the current methods is that crystal samples degrade as they are subject to X-rays, and two broad groups of effects are observed: global and specific damage. While the currently successful approach is to operate outside the range where global damage is observed, specific damage is not well understood and may lead to poor interpretation of the chemistry and biology of the system under study. In this work, we present a phenomenological model in which specific damage is understood as the result of a single process, the steady excitation of crystal electrons caused by X-ray absorption, which acts as a trigger for the bulk effects that manifest themselves in the form of global damage and obscure the interpretation of chemical information from XFEL and synchrotron structural research.

scholarly journals A large-solid-angle X-ray Raman scattering spectrometer at ID20 of the European Synchrotron Radiation Facility

2017 ◽  
Vol 24 (2) ◽  
pp. 521-530 ◽  
Author(s):  
S. Huotari ◽  
Ch. J. Sahle ◽  
Ch. Henriquet ◽  
A. Al-Zein ◽  
K. Martel ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Raman Scattering ◽  
Solid Angle ◽  
European Synchrotron Radiation Facility ◽  
Electronic Excitations ◽  
Raman Scattering Spectroscopy ◽  
X Ray ◽  
Area Detector ◽  
Spectroscopic Tool

An end-station for X-ray Raman scattering spectroscopy at beamline ID20 of the European Synchrotron Radiation Facility is described. This end-station is dedicated to the study of shallow core electronic excitations using non-resonant inelastic X-ray scattering. The spectrometer has 72 spherically bent analyzer crystals arranged in six modular groups of 12 analyzer crystals each for a combined maximum flexibility and large solid angle of detection. Each of the six analyzer modules houses one pixelated area detector allowing for X-ray Raman scattering based imaging and efficient separation of the desired signal from the sample and spurious scattering from the often used complicated sample environments. This new end-station provides an unprecedented instrument for X-ray Raman scattering, which is a spectroscopic tool of great interest for the study of low-energy X-ray absorption spectra in materials under in situ conditions, such as in operando batteries and fuel cells, in situ catalytic reactions, and extreme pressure and temperature conditions.

Synthesis of Galactomannan Sulfate-Citrate

2022 ◽  
Vol 1049 ◽  
pp. 218-223
Author(s):  
Aleksandr S. Kazachenko ◽  
Yuriy N. Malyar ◽  
Anna S. Kazachenko
Keyword(s):  
Biological Activity ◽  
Ftir Spectroscopy ◽  
X Ray Diffraction ◽  
Absorption Bands ◽  
X Ray ◽  
Mixed Ester ◽  
First Time ◽  
Derivatives Of

Sulfated derivatives of polysaccharides have anticoagulant, hypolipedimic and other biological activity. In this work, a complex mixed ester of galactomannan, its sulfate-citrate, was obtained for the first time. The introduction of citrate and sulfate groups was proved by FTIR spectroscopy by the appearance of corresponding absorption bands. It was shown by X-ray diffraction that the introduction of the citrate group leads to the amorphization of the galactomannan structure.

scholarly journals Kinetics of CxNy formation on electrode surface using the electrochemical method

2008 ◽  
Vol 40 (2) ◽  
pp. 147-154
Author(s):  
A. Chekhovskii ◽  
T. Tomila ◽  
A. Ragulya ◽  
I. Timofeeva ◽  
A. Ivanchuk ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Ir Spectroscopy ◽  
Electrode Material ◽  
Electrode Surface ◽  
Electrochemical Method ◽  
Deposition Process ◽  
Absorption Bands ◽  
X Ray ◽  
Kinetics Of ◽  
Electrolysis Products

Powded CxNy coatings were deposited from acetonitrile on Ni, Si, and C surfaces at a voltage 500-2000 V by the electrochemical method. Electrolysis products were analyzed by IR spectroscopy, X-ray phase analysis and electron microscopy. According to FTIR data, at frequencies 1370 and 1530 cm-1, absorption bands characteristic for stretching C-N and C=N oscillations are observed. The obtained results indicate that the deposition process occurs in a different manner in each specific case, i.e., the kinetics of the electrode depends on the electrode material (Ni, Si, and C).

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