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You searched for subject:(interfacial thermal conductance). Showing records 1 – 3 of 3 total matches.

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University of Notre Dame

1. Kelsey M. Stocker. Development and Application of Non-Periodic and Non-Equilibrium Molecular Dynamics Simulation Methods</h1>.

Degree: Chemistry and Biochemistry, 2014, University of Notre Dame

In this dissertation I present work on the development and application of molecular dynamics simulation methodologies for non-periodidic and non-equilibrium systems, culminating in the direct simulation of the interfacial thermal conductance of solvated, ligand-capped nanoparticles. Non-periodic geometries present problems for traditional affine scaling techniques in constant-pressure constant-temperature simulations. In particular, explicitly non-periodic systems or those containing materials with very different compressibilities are very difficult to simulate using exisiting methods. Our new method, the Langevin Hull, maintains a spherical boundary without the use of perturbative restraining or hard wall potentials. Velocity shearing and scaling reverse non-equilibrium molecular dynamics (VSS-RNEMD) for periodic systems is used to study the effect of ligand chain length and mixtures of chain lengths on the interfacial thermal conductance (G) of Au(111) interfaces protected by a monolayer of alkanethiolate ligands and solvated in hexane. There is no dependence on chain length for non-mixed layers, and a non-monotonic dependence of G on the fraction of long ligands included in a mixture of chain lengths. Proposed mechanisms for heat transfer rely on two competing effects: mobility of the interfacial solvent and vibrational orientational ordering between ligand and solvent molecules. Combination of the Langevin Hull non-periodic simulation method with existing VSS-RNEMD methodology yields a new non-periodic, non-equilibrium simulation method. The ability to impose kinetic energy and angular momentum fluxes in non-periodic geometries allows for the direct computation of transport properties in explicitly non-periodic systems. The interfacial thermal conductance and interfacial rotational friction are calculated for gold nanostructures solvated in a droplet of hexane, as well as the thermal conductivity of homogeneous metal and water clusters. Finally, the new non-periodic VSS-RNEMD is utilized to compute the interfacial thermal conductance of alkanethiolate ligand-protected gold nanoparticles solvated in a droplet of hexane. There is no discernible dependence of G on nanoparticle size, but a strong dependence on the length of the ligand alkane chain. The proposed heat transfer mechanisms are based on ligand chain flexibility, solvent penetration of the ligand layer, and ligand-induced restructuring of the nanoparticle surface. Advisors/Committee Members: S. Alex Kandel, Committee Member, J. Daniel Gezelter, Committee Chair, Steven A. Corcelli, Committee Member, Jeffrey Peng, Committee Member.

Subjects/Keywords: interfacial thermal conductance; gold nanoparticles; transport properties

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Stocker, K. M. (2014). Development and Application of Non-Periodic and Non-Equilibrium Molecular Dynamics Simulation Methods</h1>. (Thesis). University of Notre Dame. Retrieved from https://curate.nd.edu/show/df65v694z04

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Stocker, Kelsey M.. “Development and Application of Non-Periodic and Non-Equilibrium Molecular Dynamics Simulation Methods</h1>.” 2014. Thesis, University of Notre Dame. Accessed July 04, 2020. https://curate.nd.edu/show/df65v694z04.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Stocker, Kelsey M.. “Development and Application of Non-Periodic and Non-Equilibrium Molecular Dynamics Simulation Methods</h1>.” 2014. Web. 04 Jul 2020.

Vancouver:

Stocker KM. Development and Application of Non-Periodic and Non-Equilibrium Molecular Dynamics Simulation Methods</h1>. [Internet] [Thesis]. University of Notre Dame; 2014. [cited 2020 Jul 04]. Available from: https://curate.nd.edu/show/df65v694z04.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Stocker KM. Development and Application of Non-Periodic and Non-Equilibrium Molecular Dynamics Simulation Methods</h1>. [Thesis]. University of Notre Dame; 2014. Available from: https://curate.nd.edu/show/df65v694z04

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


University of Notre Dame

2. Xin Mu. Molecular Dynamics Study of Thermal Energy Transport in Graphene-Based Materials</h1>.

Degree: Aerospace and Mechanical Engineering, 2018, University of Notre Dame

Self-heating is a critical issue in micro- and nano-electronics, and efficient heat removal is crucial for the long-term reliability and performance of micro- and nano-electronic devices. In many semiconductor devices, the power dissipation is non-uniform, which results in hot spots in the device and makes the heat removal very complicated. When two-dimensional materials are used for the electronic applications, heat dissipation problem can be aggregated because even a small amount of Joule heat can lead to a dramatic temperature rise in the ultrathin materials. In industrial practice, high-performance site-specific heat spreader and thermoelectric material based solid cooling component are two potential tools for the hot spot mitigation. Graphene, which has ultrahigh thermal conductivity, electrical conductivity and thermoelectric power factors, can potentially be used as the core material for these two applications. In my Ph.D. study, the thermal transport properties of graphene and its derivatives were investigated using classical molecular dynamics simulations. The research goal was to understand how the chemical functionalization, isotopic effects and structural modification to influence the phonon transport in graphene and across graphene-metal interfaces, which could provide important insights to the thermal transport physics in graphene, and are of practical significance for graphene-based devices in nano-electronics and thermal management applications. Four projects have been finished in my Ph.D. study. In the first project, the phonon transport physics of pristine graphene, hydrogenated graphene and graphene oxide was investigated using large-scale molecular dynamics simulations. For the pristine graphene, highly ballistic thermal transport was observed. As for the hydrogenated graphene and graphene oxide, the thermal conductivity was significantly reduced when the hydrogen and oxygen coverage increased. For example, an oxygen coverage of 5% could reduce the graphene’s thermal conductivity by ~90%, and a coverage of 20% oxygen could lower it to ~8.8 W/mK. This value is even smaller than the calculated thermal conductivity of graphene in amorphous limit (~11.6 W/mK), which is usually regarded as the lower boundary of graphene’s thermal conductivity. The vibrational power spectral analyses showed that this large reduction in thermal conductivity was due to the significantly enhanced phonon scattering induced by the oxygen and hydrogen defects. In the second project, the thermal conductivity of oxidized polycrystalline graphene was studied. Grain boundaries and the spontaneous oxidization around grain boundary regions are the inherent features of graphene. Our study found the thermal conductivity of oxidized polycrystalline graphene decreased as oxygen coverage increased, which was due to the phonon-defect scattering. However, the relative thermal conductivity reduction of oxidized polycrystalline graphene when the oxidization was localized at the grain boundary regions was much smaller compared… Advisors/Committee Members: David B. Go, Research Director, Zhangli Peng, Committee Member, William F. Schneider, Committee Member, Edward Maginn , Committee Member, Tengfei Luo, Research Director.

Subjects/Keywords: Thermal Conductivity; Molecular Dynamics Simulation; Graphene; Interfacial Thermal Conductance

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Mu, X. (2018). Molecular Dynamics Study of Thermal Energy Transport in Graphene-Based Materials</h1>. (Thesis). University of Notre Dame. Retrieved from https://curate.nd.edu/show/jw82794370g

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Mu, Xin. “Molecular Dynamics Study of Thermal Energy Transport in Graphene-Based Materials</h1>.” 2018. Thesis, University of Notre Dame. Accessed July 04, 2020. https://curate.nd.edu/show/jw82794370g.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Mu, Xin. “Molecular Dynamics Study of Thermal Energy Transport in Graphene-Based Materials</h1>.” 2018. Web. 04 Jul 2020.

Vancouver:

Mu X. Molecular Dynamics Study of Thermal Energy Transport in Graphene-Based Materials</h1>. [Internet] [Thesis]. University of Notre Dame; 2018. [cited 2020 Jul 04]. Available from: https://curate.nd.edu/show/jw82794370g.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Mu X. Molecular Dynamics Study of Thermal Energy Transport in Graphene-Based Materials</h1>. [Thesis]. University of Notre Dame; 2018. Available from: https://curate.nd.edu/show/jw82794370g

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


University of Delaware

3. Ye, Ning. The interfacial thermal conductance of epitaxial metal-semiconductor interfaces .

Degree: 2017, University of Delaware

Understanding heat transport at nanometer and sub-nanometer lengthscales is critical to solving a wide range of technological challenges related to thermal management and energy conversion. In particular, finite Interfacial Thermal Conductance (ITC) often dominates transport whenever multiple interfaces are closely spaced together or when heat originates from sources that are highly confined by interfaces. Examples of the former include superlattices, thin films, quantum cascade lasers, and high density nanocomposites. Examples of the latter include FinFET transistors, phase-change memory, and the plasmonic transducer of a heat-assisted magnetic recording head. An understanding of the physics of such interfaces is still lacking, in part because experimental investigations to-date have not bothered to carefully control the structure of interfaces studied, and also because the most advanced theories have not been compared to the most robust experimental data. ☐ This thesis aims to resolve this by investigating ITC between a range of clean and structurally well-characterized metal-semiconductor interfaces using the Time-Domain Thermoreflectance (TDTR) experimental technique, and by providing theoretical/computational comparisons to the experimental data where possible. By studying the interfaces between a variety of materials systems, each with unique aspects to their tunability, I have been able to answer a number of outstanding questions regarding the importance of interfacial quality (epitaxial/non-epitaxial interfaces), semiconductor doping, matching of acoustic and optical phonon band structure, and the role of phonon transport mechanisms apart from direct elastic transmission on ITC. In particular, we are able to comment on the suitability of the diffuse mismatch model (DMM) to describe the transport across epitaxial interfaces. ☐ To accomplish this goal, I studied interfacial thermal transport across CoSi2, TiSi2, NiSi and PtSi - Si(100) and Si(111), (silicides-silicon), interfaces with varying levels of disorder (epitaxial and non-epitaxial). The ITC values of silicides-silicon interfaces observed in this study are higher than those of other metallic interfaces to Si found in literature. Most surprisingly, it is experimentally found that ITC values are independent of interfacial quality and substrate orientation. Computationally, it is found that the non-equilibrium atomistic Green's Function technique (NEGF), which is specically designed to simulate coherent elastic phonon transport across interfaces, significantly underpredicts ITC values for CoSi2-Si interfaces, suggesting that energy transport does not occur purely by coherent transmission of phonons, even for epitaxial interfaces. In contrast, the Diffuse Mismatch Model closely mimics the experimentally observed ITC values for CoSi2-Si, NiSi-Si and TiSi2-Si interfaces, and only slightly overestimating the same for PtSi-Si interfaces. Furthermore, the results also show that ITC is independent of degenerate doping up to doping levels of 1*1019 cm-3,…

Subjects/Keywords: Applied sciences; Epitaxial interface; Interfacial thermal conductance; Metal-semiconductor; Phonon

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Ye, N. (2017). The interfacial thermal conductance of epitaxial metal-semiconductor interfaces . (Doctoral Dissertation). University of Delaware. Retrieved from http://udspace.udel.edu/handle/19716/22685

Chicago Manual of Style (16th Edition):

Ye, Ning. “The interfacial thermal conductance of epitaxial metal-semiconductor interfaces .” 2017. Doctoral Dissertation, University of Delaware. Accessed July 04, 2020. http://udspace.udel.edu/handle/19716/22685.

MLA Handbook (7th Edition):

Ye, Ning. “The interfacial thermal conductance of epitaxial metal-semiconductor interfaces .” 2017. Web. 04 Jul 2020.

Vancouver:

Ye N. The interfacial thermal conductance of epitaxial metal-semiconductor interfaces . [Internet] [Doctoral dissertation]. University of Delaware; 2017. [cited 2020 Jul 04]. Available from: http://udspace.udel.edu/handle/19716/22685.

Council of Science Editors:

Ye N. The interfacial thermal conductance of epitaxial metal-semiconductor interfaces . [Doctoral Dissertation]. University of Delaware; 2017. Available from: http://udspace.udel.edu/handle/19716/22685

.