Author
Stephen L. Hodson
Bio: Stephen L. Hodson is an academic researcher from Purdue University. The author has contributed to research in topics: Carbon nanotube & Thermal resistance. The author has an hindex of 13, co-authored 32 publications receiving 512 citations.
Papers
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TL;DR: In this paper, the effect of direct electron-phonon coupling across the metal-dielectric interface was investigated by employing transient thermo-reflectance (TTR) measurements on Au-Si samples.
Abstract: Heat transfer across a metal-dielectric interface involves coupled transport of electrons and phonons in metal and phonons in dielectric, which can be accomplished by coupling between phonons in metal and dielectric or direct coupling between electrons in metal and phonons in dielectric. Direct electron-phonon coupling across the metal-dielectric interface is neglected in some studies [1, 2] but considered in some others [3–5]. We investigate heat transfer across metal-dielectric interfaces during ultrafast-laser heating by employing transient thermo-reflectance (TTR) measurements on Au-Si samples. With ultrafast-laser heating that creates strong thermal non-equilibrium between electrons and phonons in metal, it is possible to isolate the effect of direct electron-phonon coupling across the interface. Simulation results based on the two-temperature model (TTM) are compared with the measurement results. The comparison shows a strong direct coupling between electrons in metal and phonons in dielectric.Copyright © 2011 by ASME
74 citations
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TL;DR: The structure, composition, and morphology of these Bi2Te3 films were characterized and the thermoelectric figure of merit, both parallel and perpendicular to the substrate surface, were determined by measuring the Seebeck coefficient, electrical conductivity, and thermal conductivity in each direction.
Abstract: Highly oriented [1 1 0] Bi2Te3 films were obtained by pulsed electrodeposition. The structure, composition, and morphology of these films were characterized. The thermoelectric figure of merit (zT), both parallel and perpendicular to the substrate surface, were determined by measuring the Seebeck coefficient, electrical conductivity, and thermal conductivity in each direction. At 300 K, the in-plane and out-of-plane figure of merits of these Bi2Te3 films were (5.6 ± 1.2)·10(-2) and (10.4 ± 2.6)·10(-2), respectively.
69 citations
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TL;DR: In this article, the effect of the addition of a surfactant, sodium lignosulfonate (SLS), on the thermoelectric properties of tellurium films prepared by electrochemical deposition is studied.
52 citations
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TL;DR: In this article, the authors developed functional nTIMs based on short, verticallyaligned carbon nanotubes (CNTs) grown on both sides of a thin interposer foil and interfaced with substrate materials via metallic bonding.
Abstract: The next generation of Thermal Interface Materials (TIMs) are currently being developed to meet the increasing demands of high-powered semiconductor devices. In particular, a variety of nanostructured materials, such as carbon nanotubes (CNTs), are interesting due to their ability to provide low resistance heat transport from device to spreader and compliance between materials with dissimilar coefficients of thermal expansion (CTEs). As a result, nano-Thermal Interface Materials (nTIMs) have been conceived and studied in recent years, but few application-ready configurations have been produced and tested. Over the past year, we have undertaken major efforts to develop functional nTIMs based on short, vertically-aligned CNTs grown on both sides of a thin interposer foil and interfaced with substrate materials via metallic bonding. A high-precision 1-D steady-state test facility has been utilized to measure the performance of nTIM samples, and more importantly, to correlate performance to the
49 citations
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15 Jul 2011-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: The compositional effects in ZrB2-SiC-ZrC ultra high temperature composites with four different compositions were investigated via Spark Plasma Sintering (SPS) at a maximum temperature of 1800°C as discussed by the authors.
Abstract: The compositional effects in ZrB2–SiC–ZrC ultra high temperature composites with four different compositions were investigated via Spark Plasma Sintering (SPS) at a maximum temperature of 1800 °C. Density, Rockwell hardness, and thermal conductivity were measured, along with structural X-ray diffraction (XRD) and microstructural characterization. The relative amounts of SiC and ZrC had an influence on the composites’ density, mechanical and thermal properties.
34 citations
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01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.
29,323 citations
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TL;DR: In this paper, a detailed review of heat conduction research on both individual carbon nanotubes and nanostructured films consisting of arrays or disordered nanotube mats is presented.
Abstract: The extremely high thermal conductivities of carbon nanotubes have motivated a wealth of research. Progress includes innovative conduction metrology based on microfabricated platforms and scanning thermal probes as well as simulations exploring phonon dispersion and scattering using both transport theory and molecular dynamics. This article highlights these advancements as part of a detailed review of heat conduction research on both individual carbon nanotubes and nanostructured films consisting of arrays of nanotubes or disordered nanotube mats. Nanotube length, diameter, and chirality strongly influence the thermal conductivities of individual nanotubes and the transition from primarily diffusive to ballistic heat transport with decreasing temperature. A key experimental challenge, for both individual nanotubes and aligned films, is the separation of intrinsic and contact resistances. Molecular dynamics simulations have studied the impacts of specific types of imperfections on the nanotube conductance and its variation with length and chirality. While the properties of aligned films fall short of predictions based on individual nanotube data, improvements in surface engagement and postfabrication nanotube quality are promising for a variety of applications including mechanically compliant thermal contacts.
379 citations
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Wright-Patterson Air Force Base1, Vanderbilt University2, University of Manchester3, University of Cambridge4, Lawrence Livermore National Laboratory5, University of Southern California6, Massachusetts Institute of Technology7, Kansas State University8, Yale University9, Rice University10, Texas A&M University11, Aix-Marseille University12, National Institute of Advanced Industrial Science and Technology13, Waseda University14, National Research Council15, Aalto University16, University of Wisconsin-Madison17, Georgia Institute of Technology18, Tsinghua University19, Brookhaven National Laboratory20, University of Pennsylvania21, Peking University22, Pennsylvania State University23, Oak Ridge National Laboratory24, University of Tokyo25
TL;DR: While the primary focus of this review is on the science framework of SWCNT growth, connections to mechanisms underlying the synthesis of other 1D and 2D materials such as boron nitride nanotubes and graphene are drawn.
Abstract: Advances in the synthesis and scalable manufacturing of single-walled carbon nanotubes (SWCNTs) remain critical to realizing many important commercial applications. Here we review recent breakthroughs in the synthesis of SWCNTs and highlight key ongoing research areas and challenges. A few key applications that capitalize on the properties of SWCNTs are also reviewed with respect to the recent synthesis breakthroughs and ways in which synthesis science can enable advances in these applications. While the primary focus of this review is on the science framework of SWCNT growth, we draw connections to mechanisms underlying the synthesis of other 1D and 2D materials such as boron nitride nanotubes and graphene.
354 citations
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TL;DR: Thermal conductivity data suggest that, unlike in drawn crystalline fibres, in the authors' fibres the dominant phonon-scattering process at room temperature is still related to structural disorder, so effective heat transfer at critical contacts in electronic devices operating under high-power conditions at 200 °C over numerous cycles is demonstrated.
Abstract: Polymers are usually considered thermal insulators, because the amorphous arrangement of the molecular chains reduces the mean free path of heat-conducting phonons. The most common method to increase thermal conductivity is to draw polymeric fibres, which increases chain alignment and crystallinity, but creates a material that currently has limited thermal applications. Here we show that pure polythiophene nanofibres can have a thermal conductivity up to ∼ 4.4 W m(-1) K(-1) (more than 20 times higher than the bulk polymer value) while remaining amorphous. This enhancement results from significant molecular chain orientation along the fibre axis that is obtained during electropolymerization using nanoscale templates. Thermal conductivity data suggest that, unlike in drawn crystalline fibres, in our fibres the dominant phonon-scattering process at room temperature is still related to structural disorder. Using vertically aligned arrays of nanofibres, we demonstrate effective heat transfer at critical contacts in electronic devices operating under high-power conditions at 200 °C over numerous cycles.
332 citations
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TL;DR: DSSCs with submicrometer-sized graphite as a catalyst on fluorine-doped tin oxide TCO showed an energy conversion efficiency greater than 6.0%, which demonstrated that the graphite layer could be used both as a conducting layer and as a catalytic layer.
Abstract: Sub-micrometer-sized colloidal graphite (CG) was tested as a conducting electrode to replace transparent conducting oxide (TCO) electrodes and as a catalytic material to replace platinum (Pt) for I...
248 citations