Thermodynamics of Diffuse Interfaces

2003 ◽  
pp. 47-64
Author(s):  
G. J. Schmitz
Keyword(s):  
Diffuse Interfaces

Spin wave reflection from semi-infinite magnonic crystals with diffuse interfaces

Metamaterials ◽  
2009 ◽  
Vol 3 (1) ◽  
pp. 28-32 ◽  
Author(s):  
V.S. Tkachenko ◽  
V.V. Kruglyak ◽  
A.N. Kuchko
Keyword(s):  
Spin Wave ◽  
Wave Reflection ◽  
Diffuse Interfaces ◽  
Magnonic Crystals

scholarly journals A regularization approach for solving Poisson’s equation with singular charge sources and diffuse interfaces

2020 ◽  
Vol 102 ◽  
pp. 106144 ◽  
Author(s):  
Siwen Wang ◽  
Arum Lee ◽  
Emil Alexov ◽  
Shan Zhao
Keyword(s):  
Poisson’S Equation ◽  
Poisson's Equation ◽  
Diffuse Interfaces

Formation of a quasi-two-dimensional electron gas in GaN/AlxGa1−xN heterostructures with diffuse interfaces

2004 ◽  
Vol 95 (4) ◽  
pp. 1843-1848 ◽  
Author(s):  
K. A. Mkhoyan ◽  
J. Silcox ◽  
Z. Yu ◽  
W. J. Schaff ◽  
L. F. Eastman
Keyword(s):  
Electron Gas ◽  
Two Dimensional ◽  
Dimensional Electron ◽  
Two Dimensional Electron Gas ◽  
Diffuse Interfaces ◽  
Dimensional Electron Gas

Review on Phase-Field Modeling of Microstructure Evolutions: Application to Electron Beam Additive Manufacturing

2014 ◽  
Author(s):  
Seshadev Sahoo ◽  
Kevin Chou
Keyword(s):  
Electron Beam ◽  
Additive Manufacturing ◽  
Rapid Solidification ◽  
Phase Field ◽  
Solidification Process ◽  
Materials Processing ◽  
Rapid Solidification Process ◽  
Phase Field Modeling ◽  
Diffuse Interfaces ◽  
Field Modeling

Powder-bed electron beam additive manufacturing (EBAM) is a relatively new technology to produce metallic parts in a layer by layer fashion by melting and fusing metallic powders. EBAM is a rapid solidification process and the properties of the parts depend on the solidification behavior as well as the microstructure of the build material. Thus, the prediction of part microstructures during the process may be an important factor for process optimization. Nowadays, the increase in computational power allows for direct simulations of microstructures during materials processing for specific manufacturing conditions. Among different methods, phase-field modeling (PFM) has recently emerged as a powerful computational technique for simulating microstructure evolutions at the mesoscale during a rapid solidification process. PFM describes microstructures using a set of conserved and non-conserved field variables and the evolution of the field variables are governed by Cahn-Hilliard and Allen-Cahn equations. By using the thermodynamics and kinetic parameters as input parameters in the model, PFM is able to simulate the evolution of complex microstructures during materials processing. The objective of this study is to achieve a thorough review of PFM techniques used in various processes, attempted for an application to microstructure evolutions during EBAM. The concept of diffuse interfaces, phase field variables, thermodynamic driving forces for microstructure evolutions and the kinetic phase-field equations are described in this paper.

Heterogeneous diffuse interfaces: A new mechanism for arrested coarsening in binary mixtures

2011 ◽  
Vol 34 (9) ◽  
Author(s):  
R. Benzi ◽  
M. Bernaschi ◽  
M. Sbragaglia ◽  
S. Succi
Keyword(s):  
Binary Mixtures ◽  
Diffuse Interfaces

Modelling dynamic and irreversible powder compaction

2010 ◽  
Vol 664 ◽  
pp. 348-396 ◽  
Author(s):  
RICHARD SAUREL ◽  
N. FAVRIE ◽  
F. PETITPAS ◽  
M.-H. LALLEMAND ◽  
S. L. GAVRILYUK
Keyword(s):  
Powder Compaction ◽  
Gas Permeation ◽  
Acoustic Properties ◽  
Hyperbolic Model ◽  
Mechanical Relaxation ◽  
Hysteresis Phenomenon ◽  
Multiphase Model ◽  
Material Interfaces ◽  
Diffuse Interfaces ◽  
Comput Phys

A multiphase hyperbolic model for dynamic and irreversible powder compaction is built. Four important points have to be addressed in this case. The first one is related to the irreversible character of powder compaction. When a granular media is subjected to a loading–unloading cycle, the final volume is lower than the initial one. To deal with this hysteresis phenomenon, a multiphase model with relaxation is built. During loading, mechanical equilibrium is assumed corresponding to stiff mechanical relaxation, while during unloading non-equilibrium mechanical transformation is assumed. Consequently, the sound speed of the limit models are very different during loading and unloading. These differences in acoustic properties are responsible for irreversibility in the compaction process. The second point is related to dynamic effects, where pressure and shock waves play an important role. Wave dynamics is guaranteed by the hyperbolic character of the equations. Phase compressibility as well as configuration energy are taken into account. The third point is related to multi-dimensional situations that involve material interfaces. Indeed, most processes with powder compaction entail free surfaces. Consequently, the model should be able to solve interfaces separating pure fluids and granular mixtures. Finally, the fourth point is related to gas permeation that may play an important role in some specific powder compaction situations. This poses the difficult question of multiple-velocity description. These four points are considered in a unique model fitting the frame of multiphase theory of diffuse interfaces (Saurel & Abgrall, J. Comput. Phys., vol. 150, 1999, p. 425; Kapila et al., Phys. Fluids, vol. 13, 2001, p. 3002; Saurel et al., J. Comput. Phys., vol. 228, 2009, p. 1678). The ability of the model to deal with these various effects is validated on basic situations, where each phenomenon is considered separately. Except for the material EOS (hydrodynamic and granular pressures and energies), which are determined on the basis of separate experiments found in the literature, the model is free of adjustable parameter.

Size and Interface Effects on Thermal Conductivity of Superlattices and Periodic Thin-Film Structures

1997 ◽  
Vol 119 (2) ◽  
pp. 220-229 ◽  
Author(s):  
G. Chen
Keyword(s):  
Thin Film ◽  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Amorphous Materials ◽  
High Efficiency ◽  
Interface Roughness ◽  
Atomic Scale ◽  
Diffuse Interface ◽  
Boltzmann Transport ◽  
Diffuse Interfaces

Superlattices consisting of alternating layers of extremely thin films often demonstrate strong quantum size effects that have been utilized to improve conventional devices and develop new ones. The interfaces in these structures also affect their thermophysical properties through reflection and transmission of heat carriers. This work develops models on the effective thermal conductivity of periodic thin-film structures in the parallel direction based on the Boltzmann transport equation. Different interface conditions including specular, diffuse, and partially specular and partially diffuse interfaces, are considered. Results obtained from the partially specular and partially diffuse interface scattering model are in good agreement with experimental data on GaAs/AlAs superlattices. The study shows that the atomic scale interface roughness is the major cause for the measured reduction in the superlattice thermal conductivity. This work also suggests that by controlling interface roughness, the effective thermal conductivity of superlattices made of bulk materials with high thermal conductivities can be reduced to a level comparable to those of amorphous materials, while maintaining high electrical conductivities. This suggestion opens new possibilities in the search of high efficiency thermoelectric materials.

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