scholarly journals Tracer Diffusion Mechanism in Amorphous Solids

2011 ◽  
Vol 2011 ◽  
pp. 1-11
Author(s):  
P. K. Hung ◽  
P. H. Kien ◽  
H. V. Hue
Keyword(s):  
Thermal Annealing ◽  
Amorphous Alloys ◽  
Reasonable Agreement ◽  
Diffusion Mechanism ◽  
Amorphous Solid ◽  
Relaxation Effect ◽  
Amorphous Solids ◽  
Tracer Diffusion ◽  
Large Bubble ◽  
Spherical Void

Tracer diffusion in amorphous solid is studied by mean of nB-bubble statistic. The nB-bubble is defined as a group of atoms around a spherical void and large bubble that represents a structural defect which could be eliminated under thermal annealing. It was found that amorphous alloys such as CoxB100−x (x=90, 81.5 and 70) and Fe80P20 suffer from a large number of vacancy bubbles which function like diffusion vehicle. The concentration of vacancy bubble weakly depends on temperature, but essentially on the relaxation degree of considered sample. The diffusion coefficient estimated for proposed mechanism via vacancy bubbles is in a reasonable agreement with experiment for actual amorphous alloys. The relaxation effect for tracer diffusion in amorphous alloys is interpreted by the elimination of vacancy bubbles under thermal annealing.

Development of the Grain Size Distribution During the Crystallization of an Amorphous Solid

2011 ◽  
Vol 1308 ◽  
Author(s):  
Andreas Bill ◽  
Ralf B. Bergmann
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Growth Rates ◽  
Amorphous Solid ◽  
Amorphous Solids ◽  
Nucleation And Growth ◽  
Analytic Description ◽  
Silicon Thin Films ◽  
Random Nucleation

ABSTRACTWe present an overview of the theory developed over the last few years to describe the crystallization of amorphous solids. The microstructure of the crystallizing solid is described in terms of the grain size distribution (GSD). We propose a partial differential equation that captures the physics of crystallization in random nucleation and growth processes. The analytic description is derived for isotropic and anisotropic growth rates and allows for the analysis of different stages of crystallization, from early to full crystallization. We show how the timedependence of effective nucleation and growth rates affect the final distribution. In particular, we demonstrate that for cases described by the Kolmogorov-Avrami-Mehl-Johnson (KAMJ) model applicable to a large class of crystallization processes a lognormal type distribution is obtained at full crystallization. The application of the theory to the crystallization of silicon thin films is discussed.

Macroscopic theory of dielectric solids. I. The model of molecular optics

1977 ◽  
Vol 55 (24) ◽  
pp. 2169-2179 ◽  
Author(s):  
J. E. Sipe
Keyword(s):  
Constitutive Relations ◽  
Pair Correlation ◽  
Finite Size ◽  
Amorphous Solid ◽  
Amorphous Solids ◽  
Uniform Density ◽  
Macroscopic Theory ◽  
Standard Result ◽  
Dielectric Solids ◽  
Spatially Varying

An improved derivation is given of the macroscopic electrodynamic equations for dielectric solids of finite size composed of molecules with a given polarizability, α = α(ω), interacting only via the retarded dipole–dipole coupling. We present a derivation of the constitutive relations for both crystalline and amorphous solids, which is not based on an expansion in powers of α, and in which the radiative reaction forces are carefully taken into account. The spatially varying density and pair correlation function of an amorphous solid, defined with the help of spatial averaging procedures, are shown to satisfy an integral 'counting' relation, which puts a condition on any physically consistent model of an amorphous solid. In the absence of dissipative damping, a medium is shown to be characterized by a real, in general spatially varying, dielectric constant. For solids of uniform density, crystalline or amorphous, we obtain the standard result that inside such a medium light propagates without scattering. For amorphous solids with varying density, the theory forms the basis of the macroscopic theory of light scattering from density in-homogeneities.

Tracer Diffusion in Amorphous Alloys

1988 ◽  
pp. 409-413 ◽  
Author(s):  
J. HORVÁTH ◽  
J. OTT ◽  
K. PFAHLER ◽  
W. ULFERT
Keyword(s):  
Amorphous Alloys ◽  
Tracer Diffusion

Dislocation Core Spreading at Interfaces between Crystalline and Amorphous Solids

2001 ◽  
Vol 673 ◽  
Author(s):  
Huajian Gao ◽  
Lin Zhang ◽  
Shefford P. Baker
Keyword(s):  
Dislocation Core ◽  
Amorphous Solid ◽  
Amorphous Solids ◽  
Equilibrium Structure ◽  
Fundamental Question ◽  
Closed Form Solutions ◽  
Transmission Electron ◽  
Dependent Behavior ◽  
Amorphous Substrate ◽  
Core Width

ABSTRACTA fundamental question addressed here is concerned with the equilibrium structure of a dislocation core at an interface between a crystalline and an amorphous solid. This is motivated by experimental observations that the contrast of dislocations at an interface between a crystalline film and an amorphous substrate disappears under transmission electron microscopy. We have developed a mathematical moedl to describe the time-dependent behavior of dislocation core spreading as a function of the adhesive strength of the interface. The equilibrium core width and the rate of core spreading are determined in closed form solutions.

About the diffusion mechanism in amorphous alloys

2010 ◽  
Vol 356 (25-27) ◽  
pp. 1213-1216 ◽  
Author(s):  
P.K. Hung ◽  
L.T. Vinh ◽  
P.H. Kien
Keyword(s):  
Amorphous Alloys ◽  
Diffusion Mechanism

Effect of Microalloying with Ti or Cr on the Corrosion Behavior of Al-Ni-Y Amorphous Alloys

CORROSION ◽  
10.5006/2451 ◽  
2017 ◽  
Vol 74 (1) ◽  
pp. 66-74 ◽  
Author(s):  
L.M. Zhang ◽  
A.L. Ma ◽  
H.X. Hu ◽  
Y.G. Zheng ◽  
B.J. Yang ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Behavior ◽  
Photoelectron Spectroscopy ◽  
Amorphous Alloys ◽  
Diffusion Mechanism ◽  
High Surface ◽  
Control Sample ◽  
Surface Concentration ◽  
Passive Films ◽  
High Surface Concentration

The effect of microalloying with Ti or Cr on the corrosion behavior of Al-Ni-Y amorphous alloys in 0.1 M NaCl solution was studied by potentiodynamic polarization, Mott-Schottky, and x-ray photoelectron spectroscopy techniques. Microalloying with Ti or Cr could greatly improve the corrosion resistance of Al-Ni-Y amorphous alloys. A high surface concentration of Ti or Cr in the passive films was detected, which should be responsible for the improved corrosion resistance compared to the control sample. The possible process of Ti or Cr involved in the passive films was proposed in terms of the point defect model and the vacancy diffusion mechanism. Furthermore, the effect of Ti was stronger than Cr because of the higher film resistance as well as the higher surface concentration. The different passivation abilities and atomic radiuses between Ti and Cr were presented to explain the better microalloying effect of Ti compared to Cr.

The Influence of Thermodynamic Properties of Alloys on Effective Interdiffusion Coefficients in Ternary Systems

2007 ◽  
Vol 263 ◽  
pp. 141-146 ◽  
Author(s):  
Ü. Ugaste ◽  
Tony Laas ◽  
T. Škled-Gorbatšova
Keyword(s):  
Thermodynamic Properties ◽  
Diffusion Coefficients ◽  
Reasonable Agreement ◽  
Ternary Systems ◽  
Tracer Diffusion ◽  
Diffusion Couples ◽  
Experimental Values ◽  
Tracer Diffusion Coefficients ◽  
Interdiffusion Coefficients ◽  
The Relationship

To prove the validity of Dayananda’s phenomenological model of interdiffusion in ternary systems the effective interdiffusion coefficients for a few diffusion couples in the system Cu-Ni-Fe, annealed at 1000 oC, are calculated on the basis of this model using available tracer diffusion and thermodynamic data. It is found that the calculated values of effective interdiffusion coefficients are in reasonable agreement with experimental values extracted independently from experimental concentration--penetration curves. Using the relationship between effective interdiffusion coefficients, tracer diffusion coefficients and thermodynamic factors, it is shown that thermodynamic properties of alloys play a significant role in interdiffusion processes in the system Cu-Fe-Ni.

scholarly journals Commentary: Considerations in the Measurement of Glass Transition Temperatures of Pharmaceutical Amorphous Solids

2019 ◽  
Vol 21 (1) ◽  
Author(s):  
Ann Newman ◽  
George Zografi
Keyword(s):  
Glass Transition ◽  
Amorphous Solid ◽  
Amorphous Solids ◽  
Scanning Calorimetry ◽  
Modulated Differential Scanning Calorimetry ◽  
Preparation Methods ◽  
Glass Transition Temperatures ◽  
Pharmaceutical Applications ◽  
Sample Preparation Methods

AbstractAn increased interest in using amorphous solid forms in pharmaceutical applications to increase solubility, dissolution, and bioavailability has generated a need for better characterization of key properties, such as the glass transition (Tg) temperature. Although many laboratories measure and report this value, the details around these measurements are often vague or misunderstood. In this article, we attempt to highlight and compare various aspects of the two most common methods used to measure pharmaceutical Tg values, conventional and modulated differential scanning calorimetry (DSC). Issues that directly impact the Tg, such as instrumental parameters, sample preparation methods, data analysis, and “wet” vs. “dry” measurements, are discussed.

Tracer diffusion in amorphous alloys

1988 ◽  
Vol 97 ◽  
pp. 409-413 ◽  
Author(s):  
J. Horváth ◽  
J. Ott ◽  
K. Pfahler ◽  
W. Ulfert
Keyword(s):  
Amorphous Alloys ◽  
Tracer Diffusion
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