The thermochemical transformation mechanisms of color centers in lithium and sodium fluorides

2019 ◽  
Author(s):  
N. T. Maksimova ◽  
V. M. Kostyukov
Keyword(s):  
Color Centers ◽  
Thermochemical Transformation ◽  
Transformation Mechanisms

Generation of 4H and 6H Structures During the Hexagonal-Rhombohedral Transformation in Dy2Co17

1975 ◽  
Vol 33 ◽  
pp. 38-39
Author(s):  
C. W. Allen ◽  
D. L. Kuruzar
Keyword(s):  
Elevated Temperatures ◽  
Layer Structure ◽  
Transition Element ◽  
Temperature Structure ◽  
Allotropic Transformation ◽  
Layer Plane ◽  
Planar Defects ◽  
Topologically Close Packed ◽  
Transformation Mechanisms ◽  
Shear Transformation

The rare earth/transition element intermetallics R2T17 are essentially topologically close packed phases for which layer structure models have already been presented. Many of these compounds are known to undergo allotropic transformation of the type at elevated temperatures. It is not unexpected that shear transformation mechanisms are involved in view of the layering character of the structures. The transformations are evidently quite sluggish, illustrated in furnace cooled Dy2Co17 by the fact that only rarely has the low temperature rhombohedral form been seen. The more usual structures observed so far in furnace cooled alloys include 4H and 6H in Dy2Co17 (Figs. 1 and 2) . In any event it is quite clear that the general microstructure is very complicated as a consequence of the allotropy, illustrated in Fig. 3. Numerous planar defects in the layer plane orientation are evident as are non-layer plane defects inherited from a high temperature structure.

scholarly journals Stimulated Emission Depletion Microscopy with Color Centers in Hexagonal Boron Nitride

ACS Photonics ◽  
2021 ◽  
Author(s):  
Prince Khatri ◽  
Ralph Nicholas Edward Malein ◽  
Andrew J. Ramsay ◽  
Isaac J. Luxmoore
Keyword(s):  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
Stimulated Emission ◽  
Color Centers ◽  
Stimulated Emission Depletion

scholarly journals Torrefaction of Woody and Agricultural Biomass: Influence of the Presence of Water Vapor in the Gaseous Atmosphere

Processes ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 30
Author(s):  
María González Martínez ◽  
Estéban Hélias ◽  
Gilles Ratel ◽  
Sébastien Thiéry ◽  
Thierry Melkior
Keyword(s):  
Water Vapor ◽  
Water Content ◽  
Wheat Straw ◽  
Beech Wood ◽  
High Water ◽  
High Water Content ◽  
Biomass Degradation ◽  
Moist Atmosphere ◽  
Thermochemical Transformation ◽  
Degradation Reactions

Biomass preheating in torrefaction at an industrial scale is possible through a direct contact with the hot gases released. However, their high water-content implies introducing moisture (around 20% v/v) in the torrefaction atmosphere, which may impact biomass thermochemical transformation. In this work, this situation was investigated for wheat straw, beech wood and pine forest residue in torrefaction in two complementary experimental devices. Firstly, experiments in chemical regime carried out in a thermogravimetric analyzer (TGA) showed that biomass degradation started from lower temperatures and was faster under a moist atmosphere (20% v/v water content) for all biomass samples. This suggests that moisture might promote biomass components’ degradation reactions from lower temperatures than those observed under a dry atmosphere. Furthermore, biomass inorganic composition might play a role in the extent of biomass degradation in torrefaction in the presence of moisture. Secondly, torrefaction experiments on a lab-scale device made possible to assess the influence of temperature and residence time under dry and 100% moist atmosphere. In this case, the difference in solid mass loss between dry and moist torrefaction was only significant for wheat straw. Globally, an effect of water vapor on biomass transformation through torrefaction was observed (maximum 10%db), which appeared to be dependent on the biomass type and composition.

Generation of laser radiation by color centers in diamond crystals (review)

2021 ◽  
Author(s):  
V. P. Mironov ◽  
E. A. Protasova ◽  
E. I. Lipatov ◽  
E. F. Martynovich
Keyword(s):  
Laser Radiation ◽  
Color Centers ◽  
Diamond Crystals

scholarly journals Near‐Field Energy Transfer between a Luminescent 2D Material and Color Centers in Diamond

2019 ◽  
Vol 3 (2) ◽  
pp. 1900088 ◽  
Author(s):  
Richard Nelz ◽  
Mariusz Radtke ◽  
Abdallah Slablab ◽  
Zai‐Quan Xu ◽  
Mehran Kianinia ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Near Field ◽  
Color Centers ◽  
Field Energy ◽  
2D Material

Phase Separation of β-SN in Strained, Compositionally Metastable Ge1-xSnx Alloys

1995 ◽  
Vol 398 ◽  
Author(s):  
Joshua W. Kriesel ◽  
Susanne M. Lee
Keyword(s):  
Phase Separation ◽  
Electron Microprobe ◽  
Rf Sputtering ◽  
Melting Behavior ◽  
Solubility Limit ◽  
X Ray Diffraction ◽  
Solid Solubility Limit ◽  
Transformation Mechanisms ◽  
Subsequent Phase ◽  
Kinetics Of

ABSTRACTUsing rf sputtering and post-deposition annealing in a differential scanning calorimeter (DSC), we manufactured bulk (4000 nm) films of crystalline Ge0.83Sn0.17. This Sn concentration is much greater than the solid solubility limit of Sn in Ge (x ≤ 0.01). Continued annealing thermally induces Sn phase separation from the alloy, limiting the ultimate attainable grain size in the metastable crystals. We examine, here, the mechanisms and kinetics of the processes limiting the size of the Ge0.83Sn0.17 polycrystals. From a combination of DSC, electron microprobe, and x-ray diffraction (XRD) measurements, we propose phase transformation mechanisms corresponding to crystallization of amorphous Ge0.83Sn0.17, crystallization of an as-yet unidentified phase of Sn, and phase separation of Sn from the Ge1-xSnx crystals. We were unable to observe the unidentified phase of Sn in XRD, but the phase must be present in the material to account for the quantitative discrepancies (as much as 8 at.%) in Sn percentages determined from each of the DSC, XRD, and electron microprobe measurements. Our models for the various transformation kinetics were corroborated by the subsequent phase-separated Sn melting behavior observed in the DSC: two Sn melting endotherms, one of which was 20–100°C lower than the bulk melting temperature of Sn. This depressed temperature endotherm we speculate represents liquefaction of nanometer-sized (β–Sn clusters.

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