Understanding Reactivity at Very Low Temperatures: The Reactions of Oxygen Atoms with Alkenes

Science ◽  
2007 ◽  
Vol 317 (5834) ◽  
pp. 102-105 ◽  
Author(s):  
H. Sabbah ◽  
L. Biennier ◽  
I. R. Sims ◽  
Y. Georgievskii ◽  
S. J. Klippenstein ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Oxygen Atoms

A study of chromium-exchanged zeolites as potential catalysts for thermolysis of water

1986 ◽  
Vol 64 (7) ◽  
pp. 1332-1339 ◽  
Author(s):  
K. M. Miedzinska ◽  
B. R. Hollebone
Keyword(s):  
Low Temperatures ◽  
Metal Ion ◽  
Redox Cycle ◽  
Zeolite 13X ◽  
Irreversible Reduction ◽  
Very High ◽  
Oxygen Atoms

Evidence was found that the Cr(III)/Cr(II) redox cycle previously described to occur upon dehydration and rehydration of exchanged zeolite 13X, does not occur reversibly. Data suggest dimerization of the metal ion at high levels of exchange. The bridging provideu by the oxygen atoms of the lattice probably stabilize these dimers and lead to initial but irreversible reduction at very low temperatures. Evidence also indicates irreversible formation of new lattices at very high dehydration temperatures.

Out Diffusion of Oxygen in Czochralski Silicon at Low Temperatures

1998 ◽  
Vol 527 ◽  
Author(s):  
S.A. McQuaid ◽  
B.K. Johnson ◽  
D. Gambaro ◽  
R. Falster ◽  
M. Ashwin ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Conversion Rate ◽  
Catalytic Mechanism ◽  
Diffusion Rate ◽  
Hydrogen Plasma ◽  
Surface Concentration ◽  
Czochralski Silicon ◽  
Simultaneous Loss ◽  
Diffusion Profiles ◽  
Oxygen Atoms

ABSTRACTPreviously reported measurements of anomalously high rates of oxygen out-diffusion in Czochralski silicon at low temperatures (T≤450°C) are confirmed. The surface concentration is shown to decrease with increasing time while the depth to which the concentration is depleted remains constant. Exposure to a hydrogen plasma under conditions known to catalyse the diffusion of isolated oxygen atoms causes an increased rate of decrease of the surface concentration without significantly affecting the depth to which the concentration is depleted. The evolution of the out-diffusion profiles cannot be explained by a catalytic mechanism operating on the isolated oxygen atoms. A slow conversion of Oi to a complex containing oxygen which can diffuse rapidly over long distances before being trapped either on the surface or in the bulk of the sample can account for both out-diffusion and simultaneous loss of [Oi] in the bulk. The conversion rate is enhanced by exposure to a hydrogen plasma, indicating that it is controlled by the diffusion rate of isolated atoms.

Ordering of Oxygen Atoms in YBA2CU3O6+X and its Effects on Superconducting Properties

1987 ◽  
Vol 99 ◽  
Author(s):  
Keikichi Nakamura ◽  
Takeshi Hatano ◽  
Shozo Ikeda ◽  
Keiichi Ogawa
Keyword(s):  
Experimental Data ◽  
Oxygen Content ◽  
Low Temperatures ◽  
Room Temperature ◽  
Orthorhombic Phase ◽  
Superconducting Phase ◽  
Superconducting Transition ◽  
Superconducting Properties ◽  
Good Agreement ◽  
Oxygen Atoms

ABSTRACTOrdering of oxygen atoms in YBa2Cu3O6+x has been analysed by employing statistical thermodynamics ana the results are compared with the experimental data. The axial lengths a and b at room temperature were determined experimentally as a function of oxygen content and were found to show good agreement with the calculated lengths a and b. Special care was taken in the above experiment to dope oxygen atoms into the sample at low temperatures, typically 400° C. The superconducting transition temperature of the sample doped with oxygen at 400°C(starting material:YBa2Cu3O6.1.(decreases linearly with decreasing the oxygen content from 6+x=6.9(92 K) to 6.38(30 K) and decreased sharply around 6+x=6.35(5 K). No distinct superconducting phase corresponding to further ordered orthorhombic phase has been observed in this case.

Low activation energies for interstitial oxygen conduction in the layered perovskites La1+xSr1−xInO4+δ

2015 ◽  
Vol 3 (34) ◽  
pp. 17797-17803 ◽  
Author(s):  
L. Troncoso ◽  
J. A. Alonso ◽  
A. Aguadero
Keyword(s):  
Activation Energy ◽  
Low Temperatures ◽  
Conduction Mechanism ◽  
Activation Energies ◽  
Interstitial Oxygen ◽  
Difference Fourier ◽  
Layered Perovskites ◽  
Oxygen Atoms

Interstitial oxygen atoms (δ), identified by difference Fourier maps from NPD data, enhance the conductivity of La1.2Sr0.8InO4.11, with an extremely low activation energy of only 0.51 eV for the conduction mechanism of O2− at low temperatures.

The conversion of isolated oxygen atoms to a fast diffusing species in Czochralski silicon at low temperatures

1999 ◽  
Vol 86 (4) ◽  
pp. 1878-1887 ◽  
Author(s):  
S. A. McQuaid ◽  
B. K. Johnson ◽  
D. Gambaro ◽  
R. Falster ◽  
M. J. Ashwin ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Czochralski Silicon ◽  
Oxygen Atoms

Interpretation of irradiation-induced changes in electron diffractograms and images of extinction contours at low temperatures

1984 ◽  
Vol 42 ◽  
pp. 268-269
Author(s):  
E. Knapek ◽  
H. Formanek ◽  
G. Lefranc ◽  
I. Dietrich
Keyword(s):  
Low Temperatures ◽  
Carbon Films ◽  
Organic Crystals ◽  
Wide Spread ◽  
Lens System ◽  
Preparation Conditions ◽  
Thin Carbon ◽  
Electron Diffractograms ◽  
Diffraction Patterns ◽  
Induced Changes

A few years ago results on cryoprotection of L-valine were reported, where the values of the critical fluence De i.e, the electron exposure which decreases the intensity of the diffraction reflections by a factor e, amounted to the order of 2000 + 1000 e/nm2. In the meantime a discrepancy arose, since several groups published De values between 100 e/nm2 and 1200 e/nm2 /1 - 4/. This disagreement and particularly the wide spread of the results induced us to investigate more thoroughly the behaviour of organic crystals at very low temperatures during electron irradiation.For this purpose large L-valine crystals with homogenuous thickness were deposited on holey carbon films, thin carbon films or Au-coated holey carbon films. These specimens were cooled down to nearly liquid helium temperature in an electron microscope with a superconducting lens system and irradiated with 200 keU-electrons. The progress of radiation damage under different preparation conditions has been observed with series of electron diffraction patterns and direct images of extinction contours.

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