Defects and Diffusion in d-AlNiCo-Quasicrystals - Application of Mechanical Spectroscopy

2005 ◽  
Vol 237-240 ◽  
pp. 322-327 ◽  
Author(s):  
M. Weller ◽  
B. Damson ◽  
Michael Feuerbacher
Keyword(s):  
Tracer Diffusion ◽  
Atomic Diffusion ◽  
Local Defect ◽  
Mechanical Spectroscopy ◽  
Self Diffusion ◽  
Loss Maximum ◽  
Friction Measurements ◽  
Intergranular Diffusion ◽  
And Diffusion ◽  
Range Of Values

Mechanical loss (internal friction) measurements were applied to polycrystalline d- AlNiCo quasicrystals for compositions ranging from Al72.8Ni7.5Co19.7 to Al71.1Ni18Co10.9 and to an Al71.3Ni13.4Co15.3 mono-quasicrystal The measurements were carried out in the temperature range from 290 K up to 1220 K for measuring frequencies between 0.1Hz and 10 kHz. A loss maximum of Debye type is observed at ≈ 700 K (2Hz) for both the I-phase and the bCo-phase, which is attributed to local rearrangement of point defects. The activation enthalpy of the peak of H = 1.9 - 2.4 eV is in the range of values obtained from tracer diffusion experiments. This indicates that local defect rearrangement and self diffusion are governed by the same atomic diffusion process.. A high temperature viscoelastic damping background is only observed in polycrystalline samples with H = 2.4 – 3 eV. The background is assigned to viscolealastic relaxation based on intergranular diffusion.

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.

Atomic diffusion mediated by intrinsic point defects in GaAs and AlxGa1−xAs–GaAs superlattices

1991 ◽  
Vol 6 (7) ◽  
pp. 1542-1552 ◽  
Author(s):  
Hidehiko Iguchi
Keyword(s):  
Point Defect ◽  
Point Defects ◽  
Atomic Diffusion ◽  
Self Diffusion ◽  
Related Point ◽  
Diffusion Phenomena ◽  
Growth Method ◽  
Antisite Defects ◽  
And Diffusion ◽  
Growth Methods

Point-defect-mediated atomic diffusion in GaAs and AlxGa1−xAs–GaAs superlattices is examined thermodynamically by focusing on activation enthalpy of diffusion. Through a review of available experimental results of impurity diffusion of Si, Zn, and Be, their diffusion phenomena are discussed by taking the characteristics of column-III-site-related point defect, such as Ga vacancy and arsenic-antisite, into consideration. It is suggested that Zn and Be diffusion should be mediated by As-antisite defects. On the other hand, Si diffusion is mediated by either Ga vacancy or As-antisite, depending on the growth method of materials and diffusion conditions. It is argued that As-antisite should be a mediator of diffusion in As-antisite-rich materials and with using As-rich diffusion source under p-type conditions. Cation self-diffusion or interdiffusion is also discussed in the same manner. Impurity-enhanced layer-disordering phenomena are examined by considering the reduction of defect energy of Ga vacancy and As antisite under n-type and p-type conditions, respectively. Beryllium enhanced and suppressed interdiffusion (cation self-diffusion) in MBE-grown AlxGa1−xAs–GaAs superlattices are interpreted in view of point-defect-mediated cation diffusion on the basis of the Fermi-energy dependence of point defect. In order to explain the phenomena, crystal-growth methods and surface-localized point defects which is responsible for Fermi-level stabilization are taken into consideration.

scholarly journals Water and Deuterium Oxide Permeability through Aquaporin 1: MD Predictions and Experimental Verification

2007 ◽  
Vol 130 (1) ◽  
pp. 111-116 ◽  
Author(s):  
Artem B. Mamonov ◽  
Rob D. Coalson ◽  
Mark L. Zeidel ◽  
John C. Mathai
Keyword(s):  
Deuterium Oxide ◽  
Diffusion Constant ◽  
Structural Data ◽  
Md Simulations ◽  
Water Model ◽  
Aquaporin 1 ◽  
Self Diffusion ◽  
Osmotic Permeability ◽  
Protein Channels ◽  
And Diffusion

Determining the mechanisms of flux through protein channels requires a combination of structural data, permeability measurement, and molecular dynamics (MD) simulations. To further clarify the mechanism of flux through aquaporin 1 (AQP1), osmotic pf (cm3/s/pore) and diffusion pd (cm3/s/pore) permeability coefficients per pore of H2O and D2O in AQP1 were calculated using MD simulations. We then compared the simulation results with experimental measurements of the osmotic AQP1 permeabilities of H2O and D2O. In this manner we evaluated the ability of MD simulations to predict actual flux results. For the MD simulations, the force field parameters of the D2O model were reparameterized from the TIP3P water model to reproduce the experimentally observed difference in the bulk self diffusion constants of H2O vs. D2O. Two MD systems (one for each solvent) were constructed, each containing explicit palmitoyl-oleoyl-phosphatidyl-ethanolamine (POPE) phospholipid molecules, solvent, and AQP1. It was found that the calculated value of pf for D2O is ∼15% smaller than for H2O. Bovine AQP1 was reconstituted into palmitoyl-oleoyl-phosphatidylcholine (POPC) liposomes, and it was found that the measured macroscopic osmotic permeability coefficient Pf (cm/s) of D2O is ∼21% lower than for H2O. The combined computational and experimental results suggest that deuterium oxide permeability through AQP1 is similar to that of water. The slightly lower observed osmotic permeability of D2O compared to H2O in AQP1 is most likely due to the lower self diffusion constant of D2O.

Atomic Diffusion and its Relation to Thermodynamic Forces in Al-Ni Melts

2009 ◽  
Vol 289-292 ◽  
pp. 705-710 ◽  
Author(s):  
Axel Griesche ◽  
Bo Zhang ◽  
Jürgen Horbach ◽  
Andreas Meyer
Keyword(s):  
Chemical Diffusion ◽  
Atomic Diffusion ◽  
Dynamic Simulations ◽  
X Ray ◽  
Self Diffusion ◽  
Ni Alloys ◽  
Quasielastic Neutron ◽  
Cross Correlations ◽  
Quasielastic Neutron Scattering ◽  
Thermodynamic Forces

We make use of a novel X-ray radiography method to measure chemical diffusion in capillaries in binary Al-Ni melts. Data are compared to self diffusion coefficients of Ni obtained by quasielastic neutron scattering as well as diffusion and thermodynamic data obtained by molecular dynamic simulations. Interdiffusion compared to self diffusion is enhanced with a maximum at Al40Ni60. We show that this enhancement is caused by thermodynamic forces as described by the Darken-Manning equation. In liquid Al-Ni alloys the Manning factor that is smaller than one can be attributed to collective cross correlations.

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.

Vacancy-Mediated Diffusion and Diffusion-Controlled Processes in Ordered Binary Intermetallics by Kinetic Monte Carlo Simulations

2021 ◽  
Vol 29 ◽  
pp. 95-115
Author(s):  
Rafal Kozubski ◽  
Graeme E. Murch ◽  
Irina V. Belova
Keyword(s):  
Monte Carlo ◽  
Kinetic Monte Carlo ◽  
Simulation Studies ◽  
Self Diffusion ◽  
Monte Carlo Techniques ◽  
Diffusion Controlled ◽  
Kinetic Monte Carlo Simulations ◽  
Kinetic Effects ◽  
Kinetics Of ◽  
And Diffusion

We review the results of our Monte Carlo simulation studies carried out within the past two decades in the area of atomic-migration-controlled phenomena in intermetallic compounds. The review aims at showing the high potential of Monte Carlo methods in modelling both the equilibrium states of the systems and the kinetics of the running processes. We focus on three particular problems: (i) the atomistic origin of the complexity of the ‘order-order’ relaxations in γ’-Ni3Al; (ii) surface-induced ordering phenomena in γ-FePt and (iii) ‘order—order’ kinetics and self-diffusion in the ‘triple-defect’ β-NiAl. The latter investigation demonstrated how diverse Monte Carlo techniques may be used to model the phenomena where equilibrium thermodynamics interplays and competes with kinetic effects.

Experimental Determination of Statistical Properties of Two-Phase Turbulent Motion

1960 ◽  
Vol 82 (3) ◽  
pp. 609-621 ◽  
Author(s):  
S. L. Soo ◽  
H. K. Ihrig ◽  
A. F. El Kouh
Keyword(s):  
Gas Phase ◽  
Tracer Diffusion ◽  
Statistical Properties ◽  
Solid Particles ◽  
Turbulent Motion ◽  
Two Phase ◽  
Gaseous State ◽  
Diffusion Technique ◽  
And Diffusion

Experimental methods for the determination of certain statistical properties of turbulent conveyance and diffusion of solid particles in a gaseous state are presented. Methods include a tracer-diffusion technique for the determination of gas-phase turbulent motion and a photo-optical technique for the determination of motion of solid particles. Results are discussed and compared with previous analytical results.

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.

Deformation and Diffusion: Quantitative Relations

1993 ◽  
Author(s):  
Brian Bayly
Keyword(s):  
Normal Stress ◽  
Arc Length ◽  
Self Diffusion ◽  
Quantitative Form ◽  
Stress Components ◽  
And Diffusion ◽  
Pressure Driven

The purpose of this chapter is to put the ideas of Chapter 11 into quantitative form. The first step is to link L0 to N and K; L0 is the arc-length of the imaginary quarter-cylinders in Figure 11. 5b, N is the material's viscosity (Pa-sec), and K is its coefficient for pressure-driven self-diffusion (m2/Pa-sec). The point emphasized in Chapter 11 is that if two migration paths exist, one curved and one straight, but both having the same length and the same variation of normal-stress components along their length, migration will be equally vigorous along the two paths. Further, the shortening rates at the source-ends of the two paths will be equal. The procedure used to find the relation of L0 to (NK)1/2 is to write the two shortening rates and equate them.

Sign in / Sign up

Export Citation Format

Share Document