Point Defects and Diffusion in Ni3Ga

1998 ◽  
Vol 527 ◽  
Author(s):  
T. IKEDA ◽  
A. Almazouzi ◽  
A. Funao ◽  
H. Numakura ◽  
M. Koiwa ◽  
...  
Keyword(s):  
Point Defects ◽  
Positron Lifetime ◽  
Major Element ◽  
Tracer Diffusion ◽  
The Self ◽  
Self Diffusion ◽  
Order Of Magnitude ◽  
Constituent Elements ◽  
Tracer Diffusion Coefficients ◽  
And Diffusion

ABSTRACTThe properties of intrinsic point defects and the self-diffusion behaviour of the constituent elements in Ni3Ga have been studied by positron annihilation, tracer diffusion and interdiffusion experiments. Thermal vacancies have been detected by positron lifetime measurements for specimens quenched from high temperatures. The vacancy formation energy is in the range between 1.7 and 1.8 eV, and is not dependent strongly on the composition. The tracer diffusion coefficients of Ni and Ga are of the same order of magnitude, and the interdiffusion coefficient is about 10 times larger than the diffusion coefficient of Ni. The diffusion in Ni3Ga has been found to satisfy the Darken-Manning equation, as expected from the model of the self-diffusion in this type of materials, where both the species of atoms are assumed to migrate primarily in the sub-lattice of the major element via the ordinary vacancy mechanism.

On the Self - and Impurity Diffusion in High Entropy Alloys

2018 ◽  
Vol 17 ◽  
pp. 105-114
Author(s):  
Dezső L. Beke ◽  
Gábor Erdélyi
Keyword(s):  
Melting Point ◽  
Tracer Diffusion ◽  
The Self ◽  
Impurity Diffusion ◽  
Diffusion Activation Energy ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Self Diffusion ◽  
Law Of Corresponding States ◽  
Constituent Elements

General trends in self- and impurity diffusion data are analyzed in high entropy alloys. Our analysis is based on the similarity of inter-atomic potentials in metals, which is in fact equivalent to a three-parameter description of the system (the mass, m, the lattice spacing, a, and the melting point, Tm, are only used). This leads to the so-called law of corresponding states in metals, manifested in many empirical rules (e.g. compensation laws or the proportionality between the self-diffusion activation energy and the melting point) if one uses dimensionless/reduced variables (like the homologous temperature: T*=T/Tm). It was shown in our previous papers, using the concept of a hypothetical crystal composed of simple atomic species whose properties are an average of the components, that the tracer diffusion of any species (let it be either one of the constituent atoms or a foreign atom) can be considered as impurity diffusion in the pure many-component matrix. Using this concept, we illustrate that the diffusion coefficients, Di, follow the same rule which obtained for impurity diffusion in pure metals: lnDi=A(T*)(Tmi/Tm-1)+r, with the same fitting parameters A(T*) and r. According to this, the diffusion of the constituent elements in high entropy alloys indeed shows some sluggish character, which can be attributed to a more or less temperature independent factor.

Ab Initio Calculations of Kinetic Properties in ZrC and TiC Carbides

2011 ◽  
Vol 172-174 ◽  
pp. 990-995 ◽  
Author(s):  
Vsevolod I. Razumovskiy ◽  
Pavel A. Korzhavyi ◽  
Andrei V. Ruban
Keyword(s):  
Point Defects ◽  
First Principles ◽  
Reasonable Agreement ◽  
Nearest Neighbor ◽  
Diffusion Mechanism ◽  
The Self ◽  
Kinetic Properties ◽  
Self Diffusion ◽  
Metal Atoms ◽  
And Diffusion

Self-diffusion of the metal and carbon atoms in TiC and ZrC carbides is studied by first principles methods. Our calculations yield point defects energies, vacancy jump barriers and diffusion pre-factors in TiC and ZrC. The results are in reasonable agreement with the available experimental data and suggest that the self-diffusion mechanism for metal atoms in these carbides may involve nearest-neighbor vacancy pairs (one metal and one carbon vacancy).

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.

Diffusion in hydrogel-supported phospholipid bilayer membranes

2013 ◽  
Vol 723 ◽  
pp. 352-373 ◽  
Author(s):  
Chih-Ying Wang ◽  
Reghan J. Hill
Keyword(s):  
Tracer Diffusion ◽  
Membrane Dynamics ◽  
The Self ◽  
Phospholipid Bilayer ◽  
Total Force ◽  
Membrane Thickness ◽  
Bilayer Membranes ◽  
Self Diffusion ◽  
Planar Membrane ◽  
Self Diffusion Coefficient

AbstractWe model a cylindrical inclusion (lipid or membrane protein) translating with velocity$U$in a thin planar membrane (phospholipid bilayer) that is supported above and below by Brinkman media (hydrogels). The total force$F$, membrane velocity, and solvent velocity are calculated as functions of three independent dimensionless parameters:$\Lambda = \eta a/ ({\eta }_{m} h)$,${\ell }_{1} / a$and${\ell }_{2} / a$. Here,$\eta $and${\eta }_{m} $are the solvent and membrane shear viscosities,$a$is the particle radius,$h$is the membrane thickness, and${ \ell }_{1}^{2} $and${ \ell }_{2}^{2} $are the upper and lower hydrogel permeabilities. As expected, the dimensionless mobility$4\mathrm{\pi} \eta aU/ F= 4\mathrm{\pi} \eta aD/ ({k}_{B} T)$(proportional to the self-diffusion coefficient,$D$) decreases with decreasing gel permeabilities (increasing gel concentrations), furnishing a quantitative interpretation of how porous, gel-like supports hinder membrane dynamics. The model also provides a means of inferring hydrogel permeability and, perhaps, surface morphology from tracer diffusion measurements.

Site Preference and Diffusion in Ni3Al Alloyed with Ir, Ta or Re at 1200°C

2010 ◽  
Vol 297-301 ◽  
pp. 1322-1327 ◽  
Author(s):  
N. Garimella ◽  
H.J. Choi ◽  
Yong Ho Sohn
Keyword(s):  
Diffusion Coefficients ◽  
Tracer Diffusion ◽  
Site Preference ◽  
Solid Diffusion ◽  
Ordered Intermetallic ◽  
Ternary Alloying ◽  
Tracer Diffusion Coefficients ◽  
Interdiffusion Coefficients ◽  
And Diffusion

Diffusion in L12-Ni3Al with ternary alloying additions of Ir, Ta and Re was investigated at 1200°C using solid-to-solid diffusion couples, and examined with respect to site preference in ordered intermetallic compound. In addition to determination of average ternary interdiffusion coefficients [1-3], average effective interdiffusion coefficients were determined directly from the experimental concentration profiles. Ni has the largest magnitude of average effective interdiffusion coefficient, followed by Al, Ir, Re and Ta. The average effective interdiffusion coefficients for Ir, Re and Ta are much smaller than those for Ni and Al. Tracer diffusion coefficients determined by extrapolation technique, and available literature also followed the same trend. The relative tendency of Ni, Al, Ir, Re and Ta to occupy the -Ni and -Al sites are correlated to these diffusion coefficients, with due consideration for diffusion mechanisms and coordination of atoms.

scholarly journals Ultrafast Laplace NMR to study metal-ligand interactions in reversible polarisation transfer from parahydrogen

2021 ◽  
Author(s):  
Ben. J. Tickner ◽  
Vladimir V. Zhivonitko ◽  
Ville-Veikko Telkki
Keyword(s):  
Molecular Structure ◽  
Relaxation Times ◽  
The Self ◽  
Self Diffusion ◽  
Structure And Dynamics ◽  
Relaxation Parameters ◽  
Diffusion Constants ◽  
Ligand Interactions ◽  
And Diffusion ◽  
Metal Ligand

Laplace Nuclear Magnetic Resonance (NMR) can determine relaxation parameters and diffusion constants, giving valuable information about molecular structure and dynamics. Information about relaxation times (T1 and T2) and the self-diffusion...

Mg diffusion in forsterite from 1250–1600 °C

2020 ◽  
Vol 105 (4) ◽  
pp. 525-537 ◽  
Author(s):  
Michael C. Jollands ◽  
Irina Zhukova ◽  
Hugh St.C. O'Neill ◽  
Jörg Hermann
Keyword(s):  
Diffusion Coefficients ◽  
Inductively Coupled Plasma ◽  
Tracer Diffusion ◽  
Ion Microprobe ◽  
Inductively Coupled ◽  
Icp Ms ◽  
Order Of Magnitude ◽  
Plasma Mass Spectrometry ◽  
The Difference ◽  
Tracer Diffusion Coefficients

Abstract 26Mg tracer diffusion coefficients were determined in single crystals of pure synthetic forsterite (Mg2SiO4). Isotopically enriched powder sources both acted as the 26Mg source and buffered the activities of silica (aSiO2) at forsterite + protoenstatite (Mg2Si2O6) (high aSiO2) and forsterite + periclase (MgO) (low aSiO2). Experiments were conducted at atmospheric pressure between 1250 and 1600 °C, and at oxygen fugacities (fO2s) between 10–12 bars (CO-CO2 mix) and 10–0.7 bars (air). The resulting diffusion profiles were measured along the three principal crystallographic axes (a, b, and c; ||[100], ||[010], ||[001]) using laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS), with a quadrupole mass spectrometer. These measurements were corroborated by ion microprobe using the sensitive high resolution ion microprobe-reverse geometry (SHRIMP-RG) instrument. Mg tracer diffusion is anisotropic, with D[001] > D[010] > D[100], the difference in diffusion coefficients varying by about one order of magnitude at a given temperature with crystallographic orientation. Diffusion is faster in protoenstatite-buffered than periclase-buffered conditions, again with around one order of magnitude difference in diffusivity between buffering conditions. There is no apparent effect of fO2 on diffusion. A global fit to all data, including data from Chakraborty et al. (1994) and Morioka (1981) yields the relationship: log 10 D = log 10 D 0 ( m 2 s - 1 ) + 0 . 61 ( ± 0 . 03 ) log 10 a SiO 2 + - 359 ( ± 10 ) kJ / mol 2 . 303 R T where log10D0 is –3.15 (±0.08), –3.61 (±0.02), and –4.01 (± 0.05) m2 s–1 for the [001], [010], and [100] directions, respectively (1 s.d.). The LA-ICP-MS technique reproduces diffusion coefficients determined by SHRIMP-RG, albeit with slightly different absolute values of isotope ratios. This shows that LA-ICPMS, which is both accessible and rapid, is a robust analytical method for such tracer diffusion studies.

Solution and Diffusion in Silicone Rubber. I. A Comparison with Natural Rubber

1963 ◽  
Vol 36 (3) ◽  
pp. 642-650 ◽  
Author(s):  
R. M. Barrer ◽  
J. A. Barrie ◽  
N. K. Raman
Keyword(s):  
Statistical Theory ◽  
Natural Rubber ◽  
Silicone Rubber ◽  
Diffusion Coefficients ◽  
Molecular Size ◽  
Low Energy ◽  
Kcal Mole ◽  
Self Diffusion ◽  
Order Of Magnitude ◽  
And Diffusion

Abstract The diffusion and solubility of n- and isobutane and of n- and neopentane has been studied in the range 30° to 70° C, in polydimethylsiloxane rubbers. The solubilities are very similar to those in natural rubbers and show comparable agreement with the statistical theory of polymer penetrant mixtures. Diffusion coefficients are at least an order of magnitude greater in silicone than in natural rubbers. The very low energy of activation, ED, of about 4 kcal/mole is almost invariant among the hydrocarbons studied and is the same as for self-diffusion and viscous flow in this rubber. The low value of ED means that permeabilities of the hydrocarbons increase as the temperature falls. Because diffusion in silicones is less dependent upon molecular size and shape of penetrant than in natural rubber, the silicones are less selective though much more permeable separation barriers.

Tracer diffusion coefficients of tritiated water and acetonitrile in water + acetonitrile mixtures

1980 ◽  
Vol 33 (8) ◽  
pp. 1667 ◽  
Author(s):  
AJ Easteal
Keyword(s):  
Diffusion Coefficients ◽  
Structural Model ◽  
Tritiated Water ◽  
Tracer Diffusion ◽  
Solution Viscosity ◽  
Composition Region ◽  
Self Diffusion ◽  
Composition Variation ◽  
Diaphragm Cell ◽  
Tracer Diffusion Coefficients

Tracer diffusion coefficients of tritiated water (HTO) and 14C-labelled acetonitrile have been measured at 298.15 K by the diaphragm cell method, for the whole range of compositions of water+ acetonitrile binary mixtures. The composition variation of (a) the deviation of D from additivity and (b) the product Dη, for each component, has been evaluated. The variation of Dη is discussed in terms of the Naberukhin- Rogov structural model for solutions of non-electrolytes in water. ��� The diffusion data have been used to test a semiempirical relationship, between solution viscosity and self-diffusion coefficients, due to Albright. For the composition region of 5-55 mole % acetonitrile Albright's equation gives calculated viscosities which agree well with observed values. The calculation fails to reproduce the observed variation of viscosity for the composition region of 60-95 mole % acetonitrile.

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