Measurement of the self‐diffusion constant of aqueous calcium nitrate solutions by an NMR spin–echo technique

1976 ◽  
Vol 64 (11) ◽  
pp. 4287-4292 ◽  
Author(s):  
P. M. Gammell ◽  
R. Meister
Keyword(s):  
Spin Echo ◽  
Calcium Nitrate ◽  
Diffusion Constant ◽  
The Self ◽  
Self Diffusion ◽  
Spin Echo Technique ◽  
Nitrate Solutions

scholarly journals Time-of-flight modulated intensity small-angle neutron scattering measurement of the self-diffusion constant of water

2021 ◽  
Vol 54 (3) ◽  
Author(s):  
Stephen J. Kuhn ◽  
Niels Geerits ◽  
Christian Franz ◽  
Jeroen Plomp ◽  
Robert M. Dalgliesh ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Spin Echo ◽  
Time Of Flight ◽  
Diffusion Constant ◽  
The Self ◽  
Neutron Resonance ◽  
High Energy Resolution ◽  
Self Diffusion

The modulated intensity by zero effort small-angle neutron scattering (MI-SANS) technique is used to measure scattering with a high energy resolution on samples normally ill-suited for neutron resonance spin echo. The self-diffusion constant of water is measured over a q–t range of 0.01–0.2 Å−1 and 70–500 ps. In addition to demonstrating the methodology of using time-of-flight MI-SANS instruments to observe diffusion in liquids, the results support previous measurements on water performed with different methods. This polarized neutron technique simultaneously measures the intermediate scattering function for a wide range of time and length scales. Two radio frequency flippers were used in a spin-echo setup with a 100 kHz frequency difference in order to create a high-resolution time measurement. The results are compared with self-diffusion measurements made by other techniques and the general applicability of MI-SANS at a pulsed source is assessed.

Temperature and Pressure Dependence of Self Diffusion in Octamethylcyclotetrasiloxane and Hexamethylcyclotrisilazane

1990 ◽  
Vol 45 (11-12) ◽  
pp. 1281-1284 ◽  
Author(s):  
A. Greiner-Schmid ◽  
M. Has ◽  
H.-D. Lüdemann
Keyword(s):  
Magnetic Field ◽  
Pressure Dependence ◽  
Spin Echo ◽  
The Self ◽  
Self Diffusion ◽  
Field Gradients ◽  
Magnetic Field Gradients ◽  
Temperature And Pressure ◽  
Spin Echo Technique ◽  
Self Diffusion Coefficient

AbstractThe pressure dependence of the self diffusion coefficient D for octamethylcyclotetrasiloxane and hexamethylcyclotrisilazane has been determined by the NMR spin echo technique with pulsed magnetic field gradients at pressures up to 200 MPa and at temperatures between 490 K and 290 K. The data extend partially into the deeply supercooled range. The isobaric temperature dependence of these data is quantitatively described by the empirical Vogel-Fulcher-Tammann equation. For both substances the melting pressure curves were determined in addition.

Self-Diffusion in Molten Lithium Nitrate

1992 ◽  
Vol 47 (10) ◽  
pp. 1047-1050 ◽  
Author(s):  
C. Herdlicka ◽  
J. Richter ◽  
M. D. Zeidler
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Spin Echo ◽  
The Self ◽  
Lithium Nitrate ◽  
Equimolar Ratio ◽  
Self Diffusion ◽  
Field Gradients ◽  
Molten Lithium ◽  
Self Diffusion Coefficient

AbstractSelf-diffusion coefficients of 7Li+ ions have been measured in molten LiNO3 with several compositions of 6Li+ and 7Li+ over a temperature range from 537 to 615 K. The NMR spin-echo method with pulsed field gradients was applied. It was found that the self-diffusion coefficient depends on the isotopic composition and shows a maximum at equimolar ratio. At temperatures above 600 K this behaviour disappears.

On The Melting of Amorphous Ge and Si

1981 ◽  
Vol 7 ◽  
Author(s):  
David Turnbull
Keyword(s):  
Glass Transition ◽  
External Surface ◽  
Rapid Heating ◽  
Diffusion Constant ◽  
Nucleation And Growth ◽  
The Self ◽  
Metallic State ◽  
Equilibrium Melting Temperature ◽  
Self Diffusion ◽  
Limiting Values

ABSTRACTThe amorphous semiconducting phase (a-sc) of Si or Ge is so resistant to crystallization that rapid heating may bring it into a temperature regime in which it melts. Such melting might occur in one or the other of two ways, either homogeneously, by the reverse of the glass transition, to a viscous semi-conducting melt (ℓ-sc) or by transition, probably by nucleation and growth, to the molten metallic state (ℓm). Using the self-diffusion constant of the crystalline elements in conjunction with the Stokes-Einstein equation, upper limiting values of the glass transition (a-sc→ℓ-sc) temperatures of Si and Ge were calculated. These were of the order 0.6 to 0.65 Tcℓ for slow and 1.1 Tcℓ for ultra rapid heating, where Tcℓ is the equilibrium melting temperature of the crystal. Arguments are given that superheating to a temperature 1.15 to 1.25 Taℓ (a-sc↔ℓm in equilibrium at temperature T = Taℓ< Tcℓ) may be required for copious internal nucleation of im in a-sc. At lesser superheating the transition must be initiated at internal flaws (e.g. voids) or at the external surface of the a-sc film. Therefore the superheating at perceptible onset of the transition during rapid heating can vary widely from specimen to specimen, depending on the flaw concentration and how the external surface of a-sc was treated.

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