Documents disponibles écrits par cet auteur

Anharmonic phonon interactions at interfaces and contributions to thermal boundary conductance / Patrick E. Hopkins in Journal of heat transfer, Vol. 133 N° 6 (Juin 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 6 (Juin 2011) . - pp. [062401/1-11] Titre : Anharmonic phonon interactions at interfaces and contributions to thermal boundary conductance Type de document : texte imprimé Auteurs : Patrick E. Hopkins, Auteur ; John C. Duda, Auteur ; Pamela M. Norris, Auteur Année de publication : 2011 Article en page(s) : pp. [062401/1-11] Note générale : Physique Langues : Anglais (eng) Mots-clés : Thermal  boundary  conductance  Kopitza  resistance  Phonon  interfacial  scattering  Elastic  and  inelastic  scattering  Harmonic  and  anharmonic  processes Index. décimale : 536 Chaleur. Thermodynamique Résumé : Continued reduction in characteristic dimensions in nanosystems has given rise to increasing importance of material interfaces on the overall system performance. With regard to thermal transport, this increases the need for a better fundamental understanding of the processes affecting interfacial thermal transport, as characterized by the thermal boundary conductance. When thermal boundary conductance is driven by phononic scattering events, accurate predictions of interfacial transport must account for anharmonic phononic coupling as this affects the thermal transmission. In this paper, a new model for phononic thermal boundary conductance is developed that takes into account anharmonic coupling, or inelastic scattering events, at the interface between two materials. Previous models for thermal boundary conductance are first reviewed, including the diffuse mismatch model, which only considers elastic phonon scattering events, and earlier attempts to account for inelastic phonon scattering, namely, the maximum transmission model and the higher harmonic inelastic model. A new model is derived, the anharmonic inelastic model, which provides a more physical consideration of the effects of inelastic scattering on thermal boundary conductance. This is accomplished by considering specific ranges of phonon frequency interactions and phonon number density conservation. Thus, this model considers the contributions of anharmonic, inelastically scattered phonons to thermal boundary conductance. This new anharmonic inelastic model shows improved agreement between the thermal boundary conductance predictions and experimental data at the Pb/diamond and Au/diamond interfaces due to its ability to account for the temperature dependent changing phonon population in diamond, which can couple anharmonically with multiple phonons in Pb and Au. We conclude by discussing phonon scattering selection rules at interfaces and the probability of occurrence of these higher order anharmonic interfacial phonon processes quantified in this work. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Anharmonic phonon interactions at interfaces and contributions to thermal boundary conductance [texte imprimé] / Patrick E. Hopkins, Auteur ; John C. Duda, Auteur ; Pamela M. Norris, Auteur . - 2011 . - pp. [062401/1-11]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 6 (Juin 2011) . - pp. [062401/1-11] Mots-clés : Thermal  boundary  conductance  Kopitza  resistance  Phonon  interfacial  scattering  Elastic  and  inelastic  scattering  Harmonic  and  anharmonic  processes Index. décimale : 536 Chaleur. Thermodynamique Résumé : Continued reduction in characteristic dimensions in nanosystems has given rise to increasing importance of material interfaces on the overall system performance. With regard to thermal transport, this increases the need for a better fundamental understanding of the processes affecting interfacial thermal transport, as characterized by the thermal boundary conductance. When thermal boundary conductance is driven by phononic scattering events, accurate predictions of interfacial transport must account for anharmonic phononic coupling as this affects the thermal transmission. In this paper, a new model for phononic thermal boundary conductance is developed that takes into account anharmonic coupling, or inelastic scattering events, at the interface between two materials. Previous models for thermal boundary conductance are first reviewed, including the diffuse mismatch model, which only considers elastic phonon scattering events, and earlier attempts to account for inelastic phonon scattering, namely, the maximum transmission model and the higher harmonic inelastic model. A new model is derived, the anharmonic inelastic model, which provides a more physical consideration of the effects of inelastic scattering on thermal boundary conductance. This is accomplished by considering specific ranges of phonon frequency interactions and phonon number density conservation. Thus, this model considers the contributions of anharmonic, inelastically scattered phonons to thermal boundary conductance. This new anharmonic inelastic model shows improved agreement between the thermal boundary conductance predictions and experimental data at the Pb/diamond and Au/diamond interfaces due to its ability to account for the temperature dependent changing phonon population in diamond, which can couple anharmonically with multiple phonons in Pb and Au. We conclude by discussing phonon scattering selection rules at interfaces and the probability of occurrence of these higher order anharmonic interfacial phonon processes quantified in this work. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Controlling thermal conductivity of alloys via atomic ordering / John C. Duda in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 04 p. Titre : Controlling thermal conductivity of alloys via atomic ordering Type de document : texte imprimé Auteurs : John C. Duda, Auteur ; Timothy S. English, Auteur ; Donald A. Jordan, Auteur Année de publication : 2012 Article en page(s) : 04 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Molecular  dynamics  method  Order-disorder  transformations  Phonons  Solid  solutions  Thermal  conductivity Index. décimale : 536 Chaleur. Thermodynamique Résumé : Many random substitutional solid solutions (alloys) will display a tendency to atomically order given the appropriate kinetic and thermodynamic conditions. Such order–disorder transitions will result in major crystallographic reconfigurations, where the atomic basis, symmetry, and periodicity of the alloy change dramatically. Consequently, phonon behavior in these alloys will vary greatly depending on the type and degree of ordering achieved. To investigate these phenomena, the role of the order–disorder transition on phononic transport properties of Lennard–Jones type binary alloys is explored via nonequilibrium molecular dynamics simulations. Particular attention is paid to regimes in which the alloy is only partially ordered. It is shown that by varying the degree of ordering, the thermal conductivity of a binary alloy of fixed composition can be tuned across an order of magnitude at 10% of the melt temperature, and by a factor of three at 40% of the melt temperature. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...] [article] Controlling thermal conductivity of alloys via atomic ordering [texte imprimé] / John C. Duda, Auteur ; Timothy S. English, Auteur ; Donald A. Jordan, Auteur . - 2012 . - 04 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 04 p. Mots-clés : Molecular  dynamics  method  Order-disorder  transformations  Phonons  Solid  solutions  Thermal  conductivity Index. décimale : 536 Chaleur. Thermodynamique Résumé : Many random substitutional solid solutions (alloys) will display a tendency to atomically order given the appropriate kinetic and thermodynamic conditions. Such order–disorder transitions will result in major crystallographic reconfigurations, where the atomic basis, symmetry, and periodicity of the alloy change dramatically. Consequently, phonon behavior in these alloys will vary greatly depending on the type and degree of ordering achieved. To investigate these phenomena, the role of the order–disorder transition on phononic transport properties of Lennard–Jones type binary alloys is explored via nonequilibrium molecular dynamics simulations. Particular attention is paid to regimes in which the alloy is only partially ordered. It is shown that by varying the degree of ordering, the thermal conductivity of a binary alloy of fixed composition can be tuned across an order of magnitude at 10% of the melt temperature, and by a factor of three at 40% of the melt temperature. DEWEY : 536 ISSN : 0022-1481 En ligne : http://www.asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013400 [...]

On the linear temperature dependence of phonon thermal boundary conductance in the classical limit / John C. Duda in Journal of heat transfer, Vol. 133 N° 7 (Juillet 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 7 (Juillet 2011) . - pp. [074501/1-4] Titre : On the linear temperature dependence of phonon thermal boundary conductance in the classical limit Type de document : texte imprimé Auteurs : John C. Duda, Auteur ; Pamela M. Norris, Auteur ; Patrick E. Hopkins, Auteur Année de publication : 2011 Article en page(s) : pp. [074501/1-4] Note générale : Physique Langues : Anglais (eng) Mots-clés : Thermal  boundary  conductance  Phonon  Classical  limit  Silicon  Germanium  Diffuse  mismatch  model  Molecular  dynamics Index. décimale : 536 Chaleur. Thermodynamique Résumé : We present a new model for predicting thermal boundary conductance in the classical limit. This model takes a different form than those of the traditionally used mismatch theories in the fact that the temperature dependence of thermal boundary conductance is driven by the phononic scattering mechanisms of the materials comprising the interface as opposed to the heat capacities of those materials. The model developed in this work assumes that a phonon on one side of an interface may not scatter at the interface itself but instead scatter with phonons in the adjacent material via the scattering processes intrinsic in the adjacent material. We find that this model is in good agreement with classical molecular dynamics simulations of phonon transport across a Si/Ge interface. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013300 [...] [article] On the linear temperature dependence of phonon thermal boundary conductance in the classical limit [texte imprimé] / John C. Duda, Auteur ; Pamela M. Norris, Auteur ; Patrick E. Hopkins, Auteur . - 2011 . - pp. [074501/1-4]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 7 (Juillet 2011) . - pp. [074501/1-4] Mots-clés : Thermal  boundary  conductance  Phonon  Classical  limit  Silicon  Germanium  Diffuse  mismatch  model  Molecular  dynamics Index. décimale : 536 Chaleur. Thermodynamique Résumé : We present a new model for predicting thermal boundary conductance in the classical limit. This model takes a different form than those of the traditionally used mismatch theories in the fact that the temperature dependence of thermal boundary conductance is driven by the phononic scattering mechanisms of the materials comprising the interface as opposed to the heat capacities of those materials. The model developed in this work assumes that a phonon on one side of an interface may not scatter at the interface itself but instead scatter with phonons in the adjacent material via the scattering processes intrinsic in the adjacent material. We find that this model is in good agreement with classical molecular dynamics simulations of phonon transport across a Si/Ge interface. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013300 [...]

Prediction and measurement of thermal transport across interfaces between isotropic solids and graphitic materials / Pamela M. Norris in Journal of heat transfer, Vol. 134 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 2 (Fevrier 2012) . - 07 p. Titre : Prediction and measurement of thermal transport across interfaces between isotropic solids and graphitic materials Type de document : texte imprimé Auteurs : Pamela M. Norris, Auteur ; Justin L. Smoyer, Auteur ; John C. Duda, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Carbon  nanotubes  Gold  Graphene  Heat  conduction  Phonons  Thermal  conductivity  Thermoreflectance  Thin  films Index. décimale : 536 Chaleur. Thermodynamique Résumé : Due to the high intrinsic thermal conductivity of carbon allotropes, there have been many attempts to incorporate such structures into existing thermal abatement technologies. In particular, carbon nanotubes (CNTs) and graphitic materials (i.e., graphite and graphene flakes or stacks) have garnered much interest due to the combination of both their thermal and mechanical properties. However, the introduction of these carbon-based nanostructures into thermal abatement technologies greatly increases the number of interfaces per unit length within the resulting composite systems. Consequently, thermal transport in these systems is governed as much by the interfaces between the constituent materials as it is by the materials themselves. This paper reports the behavior of phononic thermal transport across interfaces between isotropic thin films and graphite substrates. Elastic and inelastic diffusive transport models are formulated to aid in the prediction of conductance at a metal-graphite interface. The temperature dependence of the thermal conductance at Au-graphite interfaces is measured via transient thermoreflectance from 78 to 400 K. It is found that different substrate surface preparations prior to thin film deposition have a significant effect on the conductance of the interface between film and substrate. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000002 [...] [article] Prediction and measurement of thermal transport across interfaces between isotropic solids and graphitic materials [texte imprimé] / Pamela M. Norris, Auteur ; Justin L. Smoyer, Auteur ; John C. Duda, Auteur . - 2012 . - 07 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 2 (Fevrier 2012) . - 07 p. Mots-clés : Carbon  nanotubes  Gold  Graphene  Heat  conduction  Phonons  Thermal  conductivity  Thermoreflectance  Thin  films Index. décimale : 536 Chaleur. Thermodynamique Résumé : Due to the high intrinsic thermal conductivity of carbon allotropes, there have been many attempts to incorporate such structures into existing thermal abatement technologies. In particular, carbon nanotubes (CNTs) and graphitic materials (i.e., graphite and graphene flakes or stacks) have garnered much interest due to the combination of both their thermal and mechanical properties. However, the introduction of these carbon-based nanostructures into thermal abatement technologies greatly increases the number of interfaces per unit length within the resulting composite systems. Consequently, thermal transport in these systems is governed as much by the interfaces between the constituent materials as it is by the materials themselves. This paper reports the behavior of phononic thermal transport across interfaces between isotropic thin films and graphite substrates. Elastic and inelastic diffusive transport models are formulated to aid in the prediction of conductance at a metal-graphite interface. The temperature dependence of the thermal conductance at Au-graphite interfaces is measured via transient thermoreflectance from 78 to 400 K. It is found that different substrate surface preparations prior to thin film deposition have a significant effect on the conductance of the interface between film and substrate. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000002 [...]