EAM Potential for Hydrogen Storage Application

2017 ◽  
Author(s):  
Y. H. Park ◽  
I. Hijazi
Keyword(s):  
Computational Models ◽  
High Mobility ◽  
Miscibility Gap ◽  
Fast Diffusion ◽  
Physical Mechanisms ◽  
Efficient Storage ◽  
Atomic Simulations ◽  
Eam Potential ◽  
Huge Challenge ◽  
Absorption Of Hydrogen

Palladium is capable of storing a large atomic percent of hydrogen at room temperature and allows for hydrogen to diffuse with a high mobility. These unique properties make it an efficient storage medium for hydrogen and hydrogen isotopes, such as tritium, a byproduct of nuclear reaction. Palladium thus can be used for applications where fast diffusion and large storage density are important. Better understanding of molecular level phenomena such as hydride phase transformation in the metal and the effect of defects in the materials provides clues to designing metal hydrides that perform better. Atomic simulations are useful in the evaluation of palladium-hydrides (Pd-H) systems as changes in composition can be more easily explored than with experiments. However, the complex behavior of the Pd-H system such as phase miscibility gap presents a huge challenge to developing accurate computational models. In this paper, we present the palladium hydride potentials to investigate and identify the relevant physical mechanisms necessary to describe the absorption of hydrogen within a metal lattice.

Palladium Hydride Atomic Potentials for Hydrogen Storage/Separation

2014 ◽  
Author(s):  
Y. H. Park ◽  
I. Hijazi
Keyword(s):  
Room Temperature ◽  
Molecular Level ◽  
High Mobility ◽  
Fast Diffusion ◽  
Palladium Hydride ◽  
Physical Mechanisms ◽  
Efficient Storage ◽  
Atomic Simulations ◽  
Hydrogen Systems ◽  
Absorption Of Hydrogen

Palladium is capable of storing a large atomic percent of hydrogen at room temperature and allows for hydrogen to diffuse with a high mobility. These unique properties make it an efficient storage medium for hydrogen and hydrogen isotopes, such as tritium, a byproduct of nuclear reaction. Palladium thus can be used for applications where fast diffusion and large storage density are important. Better understanding of molecular level phenomena such as hydride phase transformation in the metal and the effect of defects in the materials provides clues to designing metal hydrides that perform better. Atomic simulations are useful in the evaluation of palladium-hydrogen systems as changes in composition can be more easily explored than with experiments. In this paper, we present the palladium hydride potentials to investigate and identify the relevant physical mechanisms necessary to describe the absorption of hydrogen within a metal lattice.

An embedded-atom method interatomic potential for Pd–H alloys

2008 ◽  
Vol 23 (3) ◽  
pp. 704-718 ◽  
Author(s):  
X.W. Zhou ◽  
J.A. Zimmerman ◽  
B.M. Wong ◽  
J.J. Hoyt
Keyword(s):  
Computational Models ◽  
Mechanical Response ◽  
Hydrogen Diffusion ◽  
Interatomic Potential ◽  
Diffusion Mechanism ◽  
Miscibility Gap ◽  
Embedded Atom Method ◽  
Embedded Atom ◽  
Formidable Challenge ◽  
Embedded Atom Method Potential

Palladium hydrides have important applications. However, the complex Pd–H alloy system presents a formidable challenge to developing accurate computational models. In particular, the separation of a Pd–H system to dilute (α) and concentrated (β) phases is a central phenomenon, but the capability of interatomic potentials to display this phase miscibility gap has been lacking. We have extended an existing palladium embedded-atom method potential to construct a new Pd–H embedded-atom method potential by normalizing the elemental embedding energy and electron density functions. The developed Pd–H potential reasonably well predicts the lattice constants, cohesive energies, and elastic constants for palladium, hydrogen, and PdHx phases with a variety of compositions. It ensures the correct hydrogen interstitial sites within the hydrides and predicts the phase miscibility gap. Preliminary molecular dynamics simulations using this potential show the correct phase stability, hydrogen diffusion mechanism, and mechanical response of the Pd–H system.

ANALYSIS OF BLOOD FLOW PASSING THROUGH AORTIC AND MITRAL VALVES USING A COMPUTATIONAL MODEL OF CONCENTRATED PARAMETERS

2014 ◽  
Vol 26 (06) ◽  
pp. 1450068
Author(s):  
J. Del Río Palma ◽  
E. Romero V. ◽  
M. Cerrolaza
Keyword(s):  
Blood Flow ◽  
Heart Valves ◽  
Computational Models ◽  
Flow Behavior ◽  
Flow Analysis ◽  
High Mobility ◽  
Abnormal Behavior ◽  
Factors Affecting ◽  
Main Factors ◽  
The Impact

Blood flow has been extensively studied because of its close relationship with cardiovascular disease. Heart valves blood flow analysis is particularly complex due to the high mobility of its leaflets, a fact that has stimulated the development of computational models aimed to its better understanding. For studying heart valves blood flow, we developed a mathematical model derived from clinical observations based on echocardiographic images, which describe valve leaflets motion and its influence on blood flow. This work presents a concentrated-parameters-based model of heart valves blood flow that takes into consideration five main factors affecting such a flow in the mitral and aortic valves. This model considers factors that are related to blood fluid and valve leaflets characteristics. Considering the main factors involved, it was found that blood flow exhibit an abnormal behavior in response to small variations (less than 10%) in blood pressure gradient or in leaflets stiffness. Likewise, after changing the roughness of the leaflets, the impact is smaller, only slightly affecting blood flow behavior with changes beyond 30%. Moreover, it was observed that the influence of fluid vortices originated behind the valves can be disregarded and the kinetic energy induced by them is almost negligible.

Empirical Eigenfunctions and Medial Surface Dynamics of a Human Vocal Fold

2005 ◽  
Vol 44 (03) ◽  
pp. 384-391 ◽  
Author(s):  
N. Tayama ◽  
D. A. Berry ◽  
M. Döllinger
Keyword(s):  
Vocal Fold ◽  
High Speed ◽  
Computational Models ◽  
Imaging System ◽  
Vocal Folds ◽  
Sustained Oscillation ◽  
Medial Surface ◽  
Physical Mechanisms ◽  
Vocal Fold Vibration ◽  
Modes Of Vibration

Summary Objectives: The purpose of this investigation was to use an excised human larynx to substantiate physical mechanisms of sustained vocal fold oscillation over a variety of phonatory conditions. During sustained, flow-induced oscillation, dynamical data was collected from the medial surface of the vocal fold. The method of Empirical Eigenfunctions was used to analyze the data and to probe physical mechanisms of sustained oscillation. Methods: Thirty microsutures were mounted on the medial margin of a human vocal fold. Across five distinct phonatory conditions, the vocal fold was set into oscillation and imaged with a high-speed digital imaging system. The position coordinates of the sutures were extracted from the images and converted into physical coordinates. Empirical Eigenfunctions were computed from the time-varying physical coordinates, and mechanisms of sustained oscillation were explored. Results: Using the method of Empirical Eigenfunctions, physical mechanisms of sustained vocal fold oscillation were substantiated. In particular, the essential dynamics of vocal fold vibration were captured by two dominant Empirical Eigenfunctions. The largest Eigenfunction primarily captured the alternating convergent/ divergent shape of the medial surface of the vocal fold, while the second largest Eigenfunction primarily captured the lateral vibrations of the vocal fold. Conclusions: The hemi-larynx setup yielded a view of the medial surface of the vocal folds, revealing the tissue vibrations which produced sound. Through the use of Empirical Eigenfunctions, the underlying modes of vibration were computed, disclosing physical mechanisms of sustained vocal fold oscillation. The investigation substantiated previous theoretical analyses and yielded significant data to help evaluate and refine computational models of vocal fold vibration.

Simple Pd-Ag-H EAM Potentials for Hydrogen Storage Applications

2019 ◽  
Author(s):  
Robert Fuller ◽  
Iyad Hijazi
Keyword(s):  
Hydrogen Storage ◽  
Room Temperature ◽  
Nuclear Radiation ◽  
Miscibility Gap ◽  
Embedded Atom Method ◽  
Embedded Atom ◽  
Fitting Procedure ◽  
Atomic Simulations ◽  
Dynamics Simulations ◽  
Palladium Silver

Abstract The palladium–hydrogen system has attracted a vast amount of research interest. Palladium’s ability to absorb hydrogen at room temperature is reversible, and therefore suitable for many applications, including fuel cells, hydrogen storage, and nuclear radiation adsorption. Alloying palladium with silver can increase its performance in many applications as well as substantially lowering the materials cost. Palladium silver alloys can offer increased H diffusivity and a less pronounced miscibility gap with much improved mechanical properties over pure palladium. However, the relative insolubility of hydrogen in silver necessitates proper alloying of Pd-Ag to obtain the best combination of properties. Atomic simulations are useful in the evaluation of palladium-silver hydride systems as changes in composition can be more easily explored than with experiments. In this work we introduce fully analytical Embedded Atom Method (EAM) potentials for the Pd-Ag-H system, with fewer fitting parameters than previously developed EAM models. The central atom method is used, without the need for time-consuming molecular dynamics simulations during the fitting procedure.

A Simple Palladium Hydride Embedded Atom Method Potential for Hydrogen Energy Applications

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Iyad Hijazi ◽  
Yang Zhang ◽  
Robert Fuller
Keyword(s):  
Elevated Temperatures ◽  
Clean Energy ◽  
Md Simulations ◽  
Miscibility Gap ◽  
Embedded Atom Method ◽  
Hydrogen Energy ◽  
Hydrogen Purification ◽  
Palladium Hydride ◽  
Embedded Atom ◽  
Eam Potential

When hydrogen is produced from a biomass or coal gasifier, it is necessary to purify it from syngas streams containing components such as CO, CO2, N2, CH4, and other products. Therefore, a challenge related to hydrogen purification is the development of hydrogen-selective membranes that can operate at elevated temperatures and pressures, provide high fluxes, long operational lifetime, and resistance to poisoning while still maintaining reasonable cost. Palladium-based membranes have been shown to be well suited for these types of high-temperature applications and have been widely utilized for hydrogen separation. Palladium's unique ability to absorb a large quantity of hydrogen can also be applied in various clean energy technologies, like hydrogen fuel cells. In this paper, a fully analytical interatomic embedded atom method (EAM) potential for the Pd-H system has been developed, that is easily extendable to ternary Palladium-based hydride systems, such as Pd-Cu-H and Pd-Ag-H. The new potential has fewer fitting parameters than previously developed EAM Pd-H potentials and is able to accurately predict the cohesive energy, lattice constant, bulk modulus, elastic constants, melting temperature, and the stable Pd-H structures in molecular dynamics (MD) simulations with various hydrogen concentrations. The EAM potential also well predicts the miscibility gap, the segregation of the palladium hydride system into dilute (α), and concentrated (β) phases.

A Simple EAM Potential for Hydrogen-Selective Palladium Based Membranes for Biomass Derived Syngas Processing

2018 ◽  
Author(s):  
Iyad Hijazi ◽  
Yang Zhang ◽  
Robert Fuller
Keyword(s):  
Elevated Temperatures ◽  
Clean Energy ◽  
Md Simulations ◽  
Miscibility Gap ◽  
Hydrogen Purification ◽  
Embedded Atom ◽  
Energy Technologies ◽  
Renewable Feedstock ◽  
Operational Lifetime ◽  
Eam Potential

Biomass offers the potential to economically produce hydrogen via gasification from an abundant and renewable feedstock. When hydrogen is produced from a biomass gasifier, it is necessary to purify it from syngas streams containing components such as CO, CO2, N2, CH4, and other products. Therefore, a challenge related to hydrogen purification is the development of hydrogen-selective membranes that can operate at elevated temperatures and pressures, provide high fluxes, long operational lifetime, and resistance to poisoning while still maintaining reasonable cost. Palladium based membranes have been shown to be well suited for these types of high-temperature applications and have been widely utilized for hydrogen separation. Palladium’s unique ability to absorb a large quantity of hydrogen can also be applied in various clean energy technologies, like hydrogen fuel cells. In this paper, a fully analytical interatomic Embedded Atom Potential (EAM) for the Pd-H system has been developed, that is easily extendable to ternary Palladium based hydride systems such as Pd-Cu-H and Pd-Ag-H. The new potential has fewer fitting parameters than previously developed EAM Pd-H potentials and is able to accurately predict the cohesive energy, lattice constant, bulk modulus, elastic constants, melting temperature, and the stable Pd-H structures in molecular dynamics (MD) simulations with various hydrogen concentrations. The EAM potential also well predicts the miscibility gap, the segregation of the palladium hydride system into dilute (α) and concentrated (β) phases.

A Comparison of Tem and Apfim to the Interpretation of Modulated Microstructures

1985 ◽  
Vol 43 ◽  
pp. 70-71
Author(s):  
M.G. Burke ◽  
M.K. Miller
Keyword(s):  
Low Temperature ◽  
Microstructural Characterization ◽  
Superlattice Reflection ◽  
High Volume ◽  
Atom Probe ◽  
Dark Field ◽  
Miscibility Gap ◽  
Second Phase ◽  
Two Phase ◽  
Probe Field

Interpretation of fine-scale microstructures containing high volume fractions of second phase is complex. In particular, microstructures developed through decomposition within low temperature miscibility gaps may be extremely fine. This paper compares the morphological interpretations of such complex microstructures by the high-resolution techniques of TEM and atom probe field-ion microscopy (APFIM).The Fe-25 at% Be alloy selected for this study was aged within the low temperature miscibility gap to form a <100> aligned two-phase microstructure. This triaxially modulated microstructure is composed of an Fe-rich ferrite phase and a B2-ordered Be-enriched phase. The microstructural characterization through conventional bright-field TEM is inadequate because of the many contributions to image contrast. The ordering reaction which accompanies spinodal decomposition in this alloy permits simplification of the image by the use of the centered dark field technique to image just one phase. A CDF image formed with a B2 superlattice reflection is shown in fig. 1. In this CDF micrograph, the the B2-ordered Be-enriched phase appears as bright regions in the darkly-imaging ferrite. By examining the specimen in a [001] orientation, the <100> nature of the modulations is evident.

Strain analysis with nanometer resolution using a conventional transmission electron microsopy technique: electron diffraction contrast imaging revisited

1995 ◽  
Vol 53 ◽  
pp. 168-169
Author(s):  
Koenraad G F Janssens ◽  
Omer Van der Biest ◽  
Jan Vanhellemont ◽  
Herman E Maes ◽  
Robert Hull
Keyword(s):  
Electron Diffraction ◽  
Strain Field ◽  
Elastic Strain ◽  
Strain Analysis ◽  
Local Strain ◽  
Contrast Imaging ◽  
Strain Characterization ◽  
Physical Mechanisms ◽  
Diffraction Contrast ◽  
Transmission Electron

There is a growing need for elastic strain characterization techniques with submicrometer resolution in several engineering technologies. In advanced material science and engineering the quantitative knowledge of elastic strain, e.g. at small particles or fibers in reinforced composite materials, can lead to a better understanding of the underlying physical mechanisms and thus to an optimization of material production processes. In advanced semiconductor processing and technology, the current size of micro-electronic devices requires an increasing effort in the analysis and characterization of localized strain. More than 30 years have passed since electron diffraction contrast imaging (EDCI) was used for the first time to analyse the local strain field in and around small coherent precipitates1. In later stages the same technique was used to identify straight dislocations by simulating the EDCI contrast resulting from the strain field of a dislocation and comparing it with experimental observations. Since then the technique was developed further by a small number of researchers, most of whom programmed their own dedicated algorithms to solve the problem of EDCI image simulation for the particular problem they were studying at the time.

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