Anomalous self-diffusion, structural and energy relaxations and temporal scaling laws in pure tantalum and pure vanadium metallic glasses

2019 ◽  
Vol 126 (21) ◽  
pp. 215110
Author(s):  
Donghua Xu ◽  
Zhengming Wang ◽  
Jaskaran S. Saini ◽  
Fangzheng Chen
Keyword(s):  
Metallic Glasses ◽  
Scaling Laws ◽  
Temporal Scaling ◽  
Self Diffusion ◽  
Pure Tantalum

Hydrogen Diffusion in Zr-Cu-Ni-Al Metallic Glasses

2003 ◽  
Vol 801 ◽  
Author(s):  
Tomaz Apih ◽  
Lioba Jastrow ◽  
Lyudmila Lyubenova ◽  
Janez Dolinšek ◽  
Daniela Zander ◽  
...  
Keyword(s):  
Hydrogen Content ◽  
Metallic Glasses ◽  
Hydrogen Diffusion ◽  
Spin Echo ◽  
Diffusion Constant ◽  
Superconducting Magnet ◽  
Inhomogeneous Magnetic Field ◽  
Fringe Field ◽  
Hydrogen Atoms ◽  
Self Diffusion

AbstractZr-based metallic glasses are known to absorb high amounts of hydrogen, but exhibiting less severe embrittlement than their crystalline counterparts; therefore, they might be useful for hydrogen storage application. In order to understand kinetics of hydrogen absorption and desorption in more detail, data on hydrogen diffusion are necessary. The aim of this paper is to present hydrogen diffusivities in melt-spun amorphous Zr69.5Cu12Ni11Al7.5 alloys.Hydrogen charging was performed electrochemically in a 2:1 glycerin-phosphoric acid electrolyte. Hydrogen contents were measured by a microbalance with accuracy of ±1 μg as well as by LECO. Diffusivities of hydrogen atoms were measured at different temperatures by the technique of Nuclear Magnetic Resonance (NMR) diffusion in a static fringe field of a superconducting magnet. The diffusion of hydrogen nuclei in an inhomogeneous magnetic field is accompanied by the change of its NMR resonance frequency, which produces motional destruction of the spin echo signal. The analysis of the echo damping allows a model-independent determination of the hydrogen self-diffusion constant, with the low limit of sensitivity D>10−10 cm2/s.Within the temperature interval between room temperature and 420 K diffusivities in the range between 4×10−8 and 1.2×10−9 cm2/s were observed. The Arrhenius-type temperature dependence indicate a simple classical over-barrier-hopping hydrogen diffusion; the activation energy increases slightly with the hydrogen content. Whereas in a number of metallic glasses hydrogen diffusion is known to increase with the hydrogen content, in Zr69.5Ni12Cu11Al7.5 the opposite effect was observed, at least for hydrogen contents between H/M = 0.2 and 1.2. The results will be compared with other measurements known for Zr-based metallic glasses (e.g., Zr-Ni) and discussed in detail, e.g. in regard to the density of the glass.

Irradiation-Enhanced Diffusion in Metallic Glasses

1998 ◽  
Vol 540 ◽  
Author(s):  
T. Schuler ◽  
P. Scharwaechter ◽  
W.F.J. Frank
Keyword(s):  
Point Defects ◽  
Metallic Glasses ◽  
Ion Beam ◽  
Ion Beam Sputtering ◽  
Radiotracer Technique ◽  
Enhanced Diffusion ◽  
Self Diffusion ◽  
Beam Sputtering ◽  
Diffusion Mechanisms ◽  
Dynamics Simulations

AbstractThe influence of irradiation with particles (H+, He+, 15N+) on the self-diffusion in relaxed metallic glasses (59Fe in Fe91Zr9, 59Fe in Co58Fe5Ni10Si11B16, 95Zr in Fe24Zr76) has been investigated by means of the radiotracer technique using ion-beam sputtering for serial sectioning of the specimens. Combination of the results of these experiments with accompanying molecular-dynamics simulations not only leads to an understanding of a novel phenomenon of irradiation-enhanced diffusion observed on these materials, but also confirms and refines our previous view that, in the absence of irradiation, diffusion in relaxed metallic glasses occurs by collective diffusion mechanisms not involving intrinsic point defects as diffusion vehicles.

Self-Diffusion in Bulk Metallic Glasses

1998 ◽  
Vol 554 ◽  
Author(s):  
K. Knorr ◽  
M.-P. Macht ◽  
H. Mehrer
Keyword(s):  
Metallic Glasses ◽  
Diffusion Mechanism ◽  
Bulk Metallic Glasses ◽  
Supercooled Liquid ◽  
Radiotracer Method ◽  
Self Diffusion ◽  
Diffusion Studies ◽  
Supercooled Melt ◽  
First Time ◽  
Single Set

AbstractWe have studied self-diffusion in the bulk metallic glasses Zr46.75Ti8.25Cu7.5Ni10Be27.5 and Zr65Cu17.5Ni10A17.5 by means of the radiotracer method. Diffusion of 63Ni has been investigated as a function of temperature in both alloys and also as a function of hydrostatic pressure in Zr46.75Ti8.25Cu7.5Ni10Be27.5. With the isotope 95Zr diffusion studies of the major component Zr were performed in Zr46.75Ti8.25Cu7.5Ni10Be27.5. The diffusivity of 95Zr is much smaller than that of 63Ni. The temperature dependence of 63Ni self-diffusion into Zr46.75Ti8.25Cu7.5Ni10Be27.5 and into Zr65Cu17.5Ni10A17.5 cannot be described by a single set of Arrhenius parameters, breaks in the Arrhenius curves are observed. We attribute the non-linear Arrhenius behaviour to the transition from the glassy to the supercooled liquid state. For the first time activation volumes of diffusion in a supercooled melt have been determined. From the pressure dependence of 63Ni diffusion in Zr46.75Ti8.25Cu7.5 Ni10Be27.5 we get activation volumes around one mean atomic volume favouring a diffusion mechanism via vacancy-like defects.

The temporal scaling laws of compressible turbulence

2016 ◽  
Vol 30 (23) ◽  
pp. 1650297 ◽  
Author(s):  
Bohua Sun
Keyword(s):  
Mach Number ◽  
Scaling Laws ◽  
Similarity Theory ◽  
Power Laws ◽  
Compressible Turbulence ◽  
Scaling Analysis ◽  
Temporal Scaling ◽  
Weighted Energy ◽  
Incomplete Similarity ◽  
Rate Frequency

This paper proposes temporal scaling laws of the density-weighted energy spectrum for compressible turbulence in terms of dissipation rate, frequency and the Mach number. The study adopts the incomplete similarity theory in the scaling analysis of compressible turbulence motion. The investigation shows that the temporal Eulerian and Lagrangian energy spectra approach the [Formula: see text] and [Formula: see text] power laws when the Mach number M tends to reach unity and infinity, respectively.

Siphon Flows in Stratified Coronal Loops

1994 ◽  
Vol 144 ◽  
pp. 185-187
Author(s):  
S. Orlando ◽  
G. Peres ◽  
S. Serio
Keyword(s):  
Heat Flux ◽  
Scaling Laws ◽  
Flow Model ◽  
Supersonic Flows ◽  
Coronal Loops ◽  
Characteristic Parameters

AbstractWe have developed a detailed siphon flow model for coronal loops. We find scaling laws relating the characteristic parameters of the loop, explore systematically the space of solutions and show that supersonic flows are impossible for realistic values of heat flux at the base of the upflowing leg.

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