Novel Three-dimensional Carbon Nanotube Networks as High Performance Thermal Interface Materials PDF Download

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Category :
Languages : en
Pages :

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Author: Jungkyu Park
Publisher:
ISBN:
Category : Graphene
Languages : en
Pages : 0

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Three-dimensional (3D) nanostructures comprised of one-dimensional (1D) and/or two-dimensional (2D) nanomaterials have several advantages over their base nanomaterials. Due to their dimensionally confined structures, for example, 1D carbon nanotubes (CNTs) and 2D graphene exhibit strong direction-dependent thermal transport properties with extremely inefficient cross-plane properties. However, 3D carbon nanostructures such as pillared graphene structures (PGS) are expected to be efficient in both in-plane and cross-plane thermal transport. The aim of this thesis is providing the detailed understanding of thermal transport in 3D carbon nanostructures comprised of CNTs and graphene. Reverse non-equilibrium molecular dynamics simulations were used to show that PGS and CNT networks can have both high in-plane and high cross-plane thermal conductivities comparable to their base nanomaterials, i.e. CNTs and graphene, and also to show that their thermal properties are tunable through altering their architectures. The results indicate that thermal resistances at CNT-graphene junctions result from the combined effect of phonon scattering at the junctions with distorted carbon-carbon bonds and the change in dimensionality of the phonon transport medium as phonons propagate from CNTs (1D) to graphene (2D) and then again to CNT. Moreover, wave packet analysis on SWCNT networks revealed that SWCNT-SWCNT junctions with lager diameter transmit thermal energy more efficiently than the junctions with smaller diameter, and also revealed that SWCNT-SWCNT T-junctions are more efficient in thermal energy transmission than X-junctions. A new experimental method for thermal conductivity measurements in 2D nanosheets was developed. The new method ensures a 1D heat conduction in a 2D sample by creating a spatially uniform temperature profile on the heated side of the sample, and thus improves the accuracy of the measurement in a 2D structure. A MEMS device that can measure the thermal conductivity of a graphene layer using this method is currently being fabricated for the validation of the method.

Author: Win Hon Tan
Publisher:
ISBN:
Category :
Languages : en
Pages : 67

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Author: Gang Zhang
Publisher: Elsevier
ISBN: 0323473466
Category : Technology & Engineering
Languages : en
Pages : 386

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Thermal Transport in Carbon-Based Nanomaterials describes the thermal properties of various carbon nanomaterials and then examines their applications in thermal management and renewable energy. Carbon nanomaterials include: one-dimensional (1D) structures, like nanotubes; two-dimensional (2D) crystal lattice with only one-atom-thick planar sheets, like graphenes; composites based on carbon nanotube or graphene, and diamond nanowires and thin films. In the past two decades, rapid developments in the synthesis and processing of carbon-based nanomaterials have created a great desire among scientists to gain a greater understanding of thermal transport in these materials. Thermal properties in nanomaterials differ significantly from those in bulk materials because the characteristic length scales associated with the heat carriers, phonons, are comparable to the characteristic length. Carbon nanomaterials with high thermal conductivity can be applied in heat dissipation. This looks set to make a significant impact on human life and, with numerous commercial developments emerging, will become a major academic topic over the coming years. This authoritative and comprehensive book will be of great use to both the existing scientific community in this field, as well as for those who wish to enter it. Includes coverage of the most important and commonly adopted computational and experimental methods to analyze thermal properties in carbon nanomaterials Contains information about the growth of carbon nanomaterials, their thermal properties, and strategies to control thermal properties and applications, allowing readers to assess how to use each material most efficiently Offers a comprehensive overview of the theoretical background behind thermal transport in carbon nanomaterials

Author: K.R.V. Subramanian
Publisher: CRC Press
ISBN: 1000041778
Category : Technology & Engineering
Languages : en
Pages : 151

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In this book, meshes and networks formed out of multiwalled carbon nanotubes are investigated and analyzed, including their use in niche applications such as electro-optic devices, advanced mechanical, thermal and electrical property enhancement, and gene editing. Different properties of multi-walled carbon nanotubes, including random network formation, ordering the meshes and networks by mechanical agitation and application of an external field, using crystallization and cross-linking induced phase separation in homopolymers-CNT composites are discussed with theoretical analysis. The book is aimed at researchers and graduate students in Electrical Engineering; Materials Science and Engineering; Chemical Engineering and Nanotechnology, Electronic circuit design, manufacturing, and characterization.

Author: Davood Askari
Publisher:
ISBN:
Category : Nanotubes
Languages : en
Pages : 482

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The third part of this dissertation investigates the growth of vertically aligned, long, and high density arrays of CNTs and novel 3-D carbon nanotube nano-forests. A Chemical vapor deposition technique is used to grow radially aligned CNTs on various types of fibrous materials such as silicon carbide, carbon, Kevlar, and glass fibers and clothes that can be used for the fabrication of multifunctional high performing laminated nanocomposite structures. Using the CNTs nano-forest clothes, nanocomposite samples are prepared and tested giving promising results for the improvement of mechanical properties and performance of composites structures.

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Category :
Languages : en
Pages : 34

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Carbon/carbon composites offer lightweight thermal protection capable of producing excellent thermal materials. To further improve the thermal conductivity along the thickness direction and the interlaminar shear strength, we studied and demonstrated a novel method to stitch carbon nanotube yarns along the through-thickness direction of carbon fiber two-dimensional precursor felt perform to make novel 3D reinforced carbon/carbon (C/C) composites. By stitching nanotube yarns, high strength and thermal conductive CNTs were incorporated into the preform to significantly reinforce and improve thermal conductivity along the thickness direction. In this study, we illustrated the effectiveness of the stitching method to improve through-thickness conductivity (Kz) through both modeling estimations and experimental studies. The C/C composites with 1wt.%-8wt.% stitched nanotube yarns were fabricated using in situ densification process with T300 plane weave precursors. The through-thickness conductivity measurements results using a laser-flash method showed the Kz values of the C/C composites samples with stitched nanotube yarns had large variations. The C/C composite samples with 8wt.% stitched nanotube yarns showed a Kz as high as 24.5W/mK, which was approximately a 44 percent increase compared to 17 W/mK conductivity of the control sample. The Rule of Mixture estimated the conductivity of the nanotube yarns is possibly in the range of 110W/mK through 375W/mK. Scanning electron microscopy (SEM) and Raman analysis also proved that the nanotubes survived after consolification and carbonization processing temperatures of 2500 to 2800?C. These results demonstrate the feasibility of using stitched nanotube yarns to effectively improve through-thickness conductivity.

Author: Mildred S. Dresselhaus
Publisher: Springer Science & Business Media
ISBN: 354039947X
Category : Technology & Engineering
Languages : en
Pages : 461

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After a short introduction and a brief review of the relation between carbon nanotubes, graphite and other forms of carbon, the synthesis techniques and growth mechanisms for carbon nanotubes are described. This is followed by reviews on nanotube electronic structure, electrical, optical, and mechanical properties, nanotube imaging and spectroscopy, and nanotube applications.

Author: Wei Lin
Publisher:
ISBN:
Category : Microelectronic packaging
Languages : en
Pages :

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As the integration scale of transistors/devices in a chip/system keeps increasing, effective cooling has become more and more important in microelectronics. To address the thermal dissipation issue, one important solution is to develop thermal interface materials with higher performance. Carbon nanotubes, given their high intrinsic thermal and mechanical properties, and their high thermal and chemical stabilities, have received extensive attention from both academia and industry as a candidate for high-performance thermal interface materials.\r : The thesis is devoted to addressing some challenges related to the potential application of carbon nanotubes as thermal interface materials in microelectronics. These challenges include: 1) controlled synthesis of vertically aligned carbon nanotubes on various bulk substrates via chemical vapor deposition and the fundamental understanding involved; 2) development of a scalable annealing process to improve the intrinsic properties of synthesized carbon nanotubes; 3) development of a state-of-art assembling process to effectively implement high-quality vertically aligned carbon nanotubes into a flip-chip assembly; 4) a reliable thermal measurement of intrinsic thermal transport property of vertically aligned carbon nanotube films; 5) improvement of interfacial thermal transport between carbon nanotubes and other materials.\r : The major achievements are summarized.\r : 1. Based on the fundamental understanding of catalytic chemical vapor deposition processes and the growth mechanism of carbon nanotube, fast synthesis of high-quality vertically aligned carbon nanotubes on various bulk substrates (e.g., copper, quartz, silicon, aluminum oxide, etc.) has been successfully achieved. The synthesis of vertically aligned carbon nanotubes on the bulk copper substrate by the thermal chemical vapor deposition process has set a world record. In order to functionalize the synthesized carbon nanotubes while maintaining their good vertical alignment, an in situ functionalization process has for the first time been demonstrated. The in situ functionalization renders the vertically aligned carbon nanotubes a proper chemical reactivity for forming chemical bonding with other substrate materials such as gold and silicon.\r : 2. An ultrafast microwave annealing process has been developed to reduce the defect density in vertically aligned carbon nanotubes. Raman and thermogravimetric analyses have shown a distinct defect reduction in the CNTs annealed in microwave for 3 min. Fibers spun from the as-annealed CNTs, in comparison with those from the pristine CNTs, show increases of ~35% and ~65%, respectively, in tensile strength (~0.8 GPa) and modulus (~90 GPa) during tensile testing; an ~20% improvement in electrical conductivity (~80000 S m−1) was also reported. The mechanism of the microwave response of CNTs was discussed. Such an microwave annealing process has been extended to the preparation of reduced graphene oxide.\r : 3. Based on the fundamental understanding of interfacial thermal transport and surface chemistry of metals and carbon nanotubes, two major transfer/assembling processes have been developed: molecular bonding and metal bonding. Effective improvement of the interfacial thermal transport has been achieved by the interfacial bonding.\r : 4. The thermal diffusivity of vertically aligned carbon nanotube (VACNT, multi-walled) films was measured by a laser flash technique, and shown to be ~30 mm2 s−1 along the tube-alignment direction. The calculated thermal conductivities of the VACNT film and the individual CNTs are ~27 and ~540 W m−1 K−1, respectively. The technique was verified to be reliable although a proper sampling procedure is critical. A systematic parametric study of the effects of defects, buckling, tip-to-tip contacts, packing density, and tube-tube interaction on the thermal diffusivity was carried out. Defects and buckling decreased the thermal diffusivity dramatically. An increased packing density was beneficial in increasing the collective thermal conductivity of the VACNT film; however, the increased tube-tube interaction in dense VACNT films decreased the thermal conductivity of the individual CNTs. The tip-to-tip contact resistance was shown to be ~1×10−7 m2 K W−1. The study will shed light on the potential application of VACNTs as thermal interface materials in microelectronic packaging.\r : 5. A combined process of in situ functionalization and microwave curing has been developed to effective enhance the interface between carbon nanotubes and the epoxy matrix. Effective medium theory has been used to analyze the interfacial thermal resistance between carbon nanotubes and polymer matrix, and that between graphite nanoplatlets and polymer matrix.

Author: Premkumar Nagarathnam
Publisher:
ISBN:
Category : Heat
Languages : en
Pages :

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The thermal interface layer can be a limiting element in the cooling of microelectronic devices. Conventional solders, pastes and pads are no longer sufficient to handle the high heat fluxes associated with connecting the device to the sink. Carbon nanotubes(CNTs) have been proposed as a possible thermal interface material(TI M), due to their thermal and mechanical properties, and prior research has established the effectiveness of vertically arranged CNT arrays to match the capabilities of the best conventional TIMs. However, to reach commercial applicability, many improvements need to be made in terms of improving thermal and mechanical properties as well as cost and manufacturing ease of the layer. Prior work demonstrated a simple method to transfer and bond CNT arrays through the use of a nanometer thin layer of gold as a bonding layer. This study sought to improve on that technique. By controlling the rate of deposition, the bonding temperature was reduced. By using different metals and thinner layers, the potential cost of the technique was reduced. Through the creation of a patterned array, a phase change element was able to be incorporated into the technique. The various interfaces created are characterized mechanically and thermally.