Effect of Pressure on Self Diffusion in Crystalline Silicon

1984 ◽  
Vol 36 ◽  
Author(s):  
M. J. Aziz ◽  
E. Nygren ◽  
W. H. Christie ◽  
C. W. White ◽  
D. Turnbull
Keyword(s):  
Pressure Range ◽  
High Pressures ◽  
Activation Volume ◽  
Crystalline Silicon ◽  
Tracer Diffusion ◽  
Effect Of Pressure ◽  
Self Diffusion

ABSTRACTThe effect of pressure on self diffusion in crystalline silicon is being studied using 30Si as a tracer. Diffusion experiments have been carried out in the pressure range of 1 to 35000 atmospheres at 1000°C. The 30Si is observed to diffuse faster at high pressures, indicating a negative activation volume.

Responses of cerebral arteries and arterioles to acute hypotension and hypertension

1978 ◽  
Vol 234 (4) ◽  
pp. H371-H383 ◽  
Author(s):  
H. A. Kontos ◽  
E. P. Wei ◽  
R. M. Navari ◽  
J. E. Levasseur ◽  
W. I. Rosenblum ◽  
...  
Keyword(s):  
Pressure Range ◽  
High Pressures ◽  
Cerebral Arteries ◽  
Pial Arteries ◽  
Small Vessels ◽  
Size Dependent ◽  
Arterial Blood ◽  
Vascular Bed ◽  
Acute Hypotension ◽  
Very High

The responses of cerebral precapillary vessels to changes in arterial blood pressure were studied in anesthetized cats equipped with cranial windows for the direct observation of the pial microcirculation of the parietal cortex. Vessel responses were found to be size dependent. Between mean arterial pressures of 110 and 160 mmHg autoregulatory adjustments in caliber, e.g., constriction when the pressure rose and dilation when the pressure decreased, occurred only in vessels larger than 200 micron in diameter. Small arterioles, less than 100 micron in diameter, dilated only at pressures equal to or less than 90 mmHg; below 70 mmHg their dilation exceeded that of the larger vessels. When pressure rose to 170- 200 mmHg, small vessels dilated while the larger vessels remained constricted. At very high pressures (greater than 200 mmHg) forced dilation was frequently irreversible and was accompanied by loss of responsiveness to hypocapnia. Measurement of the pressure differences across various segments of the cerebral vascular bed showed that the larger surface cerebral vessels, extending from the circle of Willis to pial arteries 200 micron in diameter, were primarily responsible for the adjustments in flow over most of the pressure range.

Self-diffusion in single crystalline silicon nanowires

2018 ◽  
Vol 123 (16) ◽  
pp. 161515 ◽  
Author(s):  
T. Südkamp ◽  
G. Hamdana ◽  
M. Descoins ◽  
D. Mangelinck ◽  
H. S. Wasisto ◽  
...  
Keyword(s):  
Silicon Nanowires ◽  
Crystalline Silicon ◽  
Single Crystalline Silicon ◽  
Single Crystalline ◽  
Self Diffusion

Self-diffusion of Ag+ and Na+ in molten Ca(NO3)2-KNO3

1972 ◽  
Vol 25 (8) ◽  
pp. 1613 ◽  
Author(s):  
BJ Welch ◽  
CA Angell
Keyword(s):  
Electrical Conductance ◽  
Ionic Species ◽  
Tracer Diffusion ◽  
Dilute Solution ◽  
Self Diffusion ◽  
Capillary Method ◽  
Arrhenius Temperature Dependence ◽  
Radio Tracer ◽  
Tracer Diffusion Coefficients ◽  
Arrhenius Temperature

In order to explore the behaviour of diffusing ionic species in a molten salt in which non-Arrhenius behaviour of other transport properties is established, the diffusivities in dilute solution of Ag+ and Na+ in 38.1 mol% Ca(NO3)2+ 61.9 mol% KNO3 have been measured. For both ions limited radio-tracer diffusion coefficients, determined using a diffusion-out-of-capillary method, are reported. D(Ag+) has also been measured by chronopotentiometry, by which means the range and reliability of the measurements were considerably extended. Chronopotentiometric and tracer data agree within expected errors of measurement. Both ionic diffusivities show a non-Arrhenius temperature dependence which is indistinguishable in magnitude from that of the electrical conductance of the solvent melt.

scholarly journals Self-Diffusion Coefficients of Methane/n-Hexane Mixtures at High Pressures: An Evaluation of the Finite-Size Effect and a Comparison of Force Fields

2019 ◽  
Author(s):  
Thiago José Pinheiro dos Santos ◽  
Charlles Abreu ◽  
Bruno Horta ◽  
Frederico W. Tavares
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficients ◽  
High Pressures ◽  
Force Fields ◽  
Transport Coefficients ◽  
Finite Size ◽  
Finite Size Effect ◽  
Self Diffusion ◽  
Analytical Correction ◽  
Dynamics Simulations

Mass transport coefficients play an important role in process design and in compositional grading of oil reservoirs. As experimental measurements of these properties can be costly and hazardous, Molecular Dynamics simulations emerge as an alternative approach. In this work, we used Molecular Dynamics to calculate the self-diffusion coefficients of methane/n-hexane mixtures at different conditions, in both liquid and supercritical phases. We evaluated how the finite box size and the choice of the force field affect the calculated properties at high pressures. Results show a strong dependency between self-diffusion and the simulation box size. The Yeh-Hummer analytical correction [J. Phys. Chem. B, 108, 15873 (2004)] can attenuate this effect, but sometimes makes the results depart from experimental data due to issues concerning the force fields. We have also found that different all-atom and united-atom models can produce biased results due to caging effects and to different dihedral configurations of the n-alkane.

Pressure-dependent self-diffusion and activation volume in solids: Sodium

1994 ◽  
Vol 49 (2) ◽  
pp. 844-848 ◽  
Author(s):  
Mithlesh Kumari ◽  
Narsingh Dass
Keyword(s):  
Activation Volume ◽  
Self Diffusion

Effect of pressure and temperature of the self-diffusion of water

1974 ◽  
Vol 14 (6) ◽  
pp. 911-914 ◽  
Author(s):  
V. V. Kisel'nik ◽  
N. G. Malyuk ◽  
A. N. Toryanik ◽  
V. M. Toryanik
Keyword(s):  
The Self ◽  
Effect Of Pressure ◽  
Self Diffusion

Activation Volume Measurements

1971 ◽  
Vol 26 (2) ◽  
pp. 291-299 ◽  
Author(s):  
Michele Beyeler ◽  
David Lazarus
Keyword(s):  
Sodium Chloride ◽  
Hydrostatic Pressure ◽  
Ionic Conductivity ◽  
Activation Volume ◽  
Tracer Diffusion ◽  
Accurate Temperature ◽  
Volume Measurements ◽  
Accurate Temperature Control ◽  
Effect Of Hydrostatic Pressure

Abstract The determination of the activation volume of diffusion is one of the best methods for the in­vestigation of the relaxation of atoms or ions around defects. This paper discusses two experimental techniques for the determination of the activation volume for diffusion, by studying the effect of hydrostatic pressure on tracer diffusion and on ionic conductivity. Such experiments require a very clean hydrostatic pressure environment, accurate temperature control and measurement, and well defined specimen geometry. The difficulties encountered during such experiments are discussed. Results are given for the activation volumes of diffusion in beryllium and in sodium chloride.

Lithium tracer diffusion in near stoichiometric LiNi0.5Mn1.5O4 cathode material for lithium-ion batteries

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Daniel Uxa ◽  
Harald Schmidt
Keyword(s):  
Cathode Material ◽  
Secondary Ion Mass Spectrometry ◽  
Lithium Ion ◽  
Tracer Diffusion ◽  
Side Reactions ◽  
Battery Materials ◽  
Self Diffusion ◽  
Thermally Activated ◽  
Average Grain Size ◽  
And Migration

Abstract The compound LiNi0.5Mn1.5O4 is used as novel cathode material for Li-ion batteries and represents a variant to replace conventional LiMn2O4. For a further improvement of battery materials it is necessary to understand kinetic processes at and in electrodes and the underlying diffusion of lithium that directly influences charging/discharging times, maximum capacities, and possible side reactions. In the present study Li tracer self-diffusion is investigated in polycrystalline sintered bulk samples of near stoichiometric LiNi0.5Mn1.5O4 with an average grain size of about 50–70 nm in the temperature range between 250 and 600 °C. For analysis, stable 6Li tracers are used in combination with secondary ion mass spectrometry (SIMS). The tracer diffusivities can be described by the Arrhenius law with an activation enthalpy of (0.97 ± 0.05) eV, which is interpreted as the sum of the formation and migration energy of a thermally activated Li vacancy.

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