Download or read book Thermal Transport in Nanostructured Thin Films for Thermoelectric Applications written by Suzanne Lee Singer and published by . This book was released on 2009 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thermoelectric Thin Films written by Paolo Mele and published by Springer. This book was released on 2019-07-17 with total page 211 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book will provide readers with deep insight into the intriguing science of thermoelectric thin films. It serves as a fundamental information source on the techniques and methodologies involved in thermoelectric thin film growth, characterization and device processing. This book involves widespread contributions on several categories of thermoelectric thin films: oxides, chalcogenides, iodates, nitrides and polymers. This will serve as an invaluable resource for experts to consolidate their knowledge and will provide insight and inspiration to beginners wishing to learn about thermoelectric thin films. Provides a single-source reference on a wide spectrum of topics related to thermoelectric thin films, from organic chemistry to devices, from physical chemistry to applied physics, from synthesis to device implementation; Covers several categories of thermoelectric thin films based on different material approaches such as oxides, chalcogenides, iodates, nitrides and polymers; Discusses synthesis, characterization, and device processing of thermoelectric thin films, as well as the nanoengineering approach to tailor the properties of the used materials at the nanoscale level.

Download or read book Thin Film and Flexible Thermoelectric Generators Devices and Sensors written by Sergey Skipidarov and published by Springer Nature. This book was released on 2021-03-13 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents and facilitates new research and development results with hot topics in the thermoelectric generators (TEGs) field. Topics include: novel thin film; multilayer, composite and nanostructured thermoelectric materials; simulation of phenomena related to thermoelectricity; thermoelectric thin film and multilayer materials manufacturing technologies; measurement techniques for characterization; thermoelectric generators; and the simulation, modeling, design, thermal, and mechanical degradation problems. This book helps researchers tackle the challenges that still remain in creating cheap and effective TEGs and presents the latest trends and technologies in development and production of advanced thermoelectric generation devices.

Download or read book Thermal Characterization of Nanostructures and Advanced Engineered Materials written by Vivek Kumar Goyal and published by . This book was released on 2011 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: Continuous downscaling of Si complementary metal-oxide semiconductor (CMOS) technology and progress in high-power electronics demand more efficient heat removal techniques to handle the increasing power density and rising temperature of hot spots. For this reason, it is important to investigate thermal properties of materials at nanometer scale and identify materials with the extremely large or extremely low thermal conductivity for applications as heat spreaders or heat insulators in the next generation of integrated circuits. The thin films used in microelectronic and photonic devices need to have high thermal conductivity in order to transfer the dissipated power to heat sinks more effectively. On the other hand, thermoelectric devices call for materials or structures with low thermal conductivity because the performance of thermoelectric devices is determined by the figure of merit Z=S 2 [sigma]/ K, where S is the Seebeck coefficient, K and [sigma] are the thermal and electrical conductivity, respectively. Nanostructured superlattices can have drastically reduced thermal conductivity as compared to their bulk counterparts making them promising candidates for high-efficiency thermoelectric materials. Other applications calling for thin films with low thermal conductivity value are high-temperature coatings for engines. Thus, materials with both high thermal conductivity and low thermal conductivity are technologically important. The increasing temperature of the hot spots in state-of-the-art chips stimulates the search for innovative methods for heat removal. One promising approach is to incorporate materials, which have high thermal conductivity into the chip design. Two suitable candidates for such applications are diamond and graphene. Another approach is to integrate the high-efficiency thermoelectric elements for on-spot cooling. In addition, there is strong motivation for improved thermal interface materials (TIMs) for heat transfer from the heat-generating chip to heat-sinking units. This dissertation presents results of the experimental investigation and theoretical interpretation of thermal transport in the advanced engineered materials, which include thin films for thermal management of nanoscale devices, nanostructured superlattices as promising candidates for high-efficiency thermoelectric materials, and improved TIMs with graphene and metal particles as fillers providing enhanced thermal conductivity. The advanced engineered materials studied include chemical vapor deposition (CVD) grown ultrananocrystalline diamond (UNCD) and microcrystalline diamond (MCD) films on Si substrates, directly integrated nanocrystalline diamond (NCD) films on GaN, free-standing polycrystalline graphene (PCG) films, graphene oxide (GOx) films, and "pseudo-superlattices" of the mechanically exfoliated Bi 2 Te 3 topological insulator films, and thermal interface materials (TIMs) with graphene fillers.

Download or read book Transport Phenomena in Thermoelectric and Ferromagnetic Nanostructures written by Johannes Kimling and published by Cuvillier Verlag. This book was released on 2013-09-23 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research on transport phenomena in a variety of materials has played a decisive role in the development of solidstate physics and has led to important applications of functional materials, e.g. for the conversion and storage of energy or in the fi eld of storage and processing of data. This thesis deals with transport phenomena in nanoscale systems. The Seebeck effect is explored in Bi2Te3 nanowires, the anisotropic magnetothermal resistance effect in Ni nanowires, and the giant magnetothermal resistance effect in Co/Cu multilayers.

Download or read book Thermal Transport in Nanoporous Materials for Energy Applications written by Jin Fang and published by . This book was released on 2012 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present study investigates the complex relationship between nanostructures and microscale thermal transport in nanoporous thin films for energy applications. It experimentally and numerically demonstrates that the effective thermal conductivity of nanoporous materials can be tuned by controlling their nanoscale architectures including porosity, pore diameter, wall thickness, nanocrystal size, and crystallinity as well as surface passivation. This study reports measurements of the cross-plane thermal conductivity of nanoporous thin films with various architectures between 25 and 315 K. Physics-based models combining phonon transport theory and effective medium approximations were developed to interpret the experimental data. Ordered mesoporous titania and silicon thin films were prepared based on evaporation-induced self-assembly method. Pure silica zeolite films were produced by either in-situ growth or by spin coating a zeolite nanoparticle suspension followed by crystal growth upon heating. These synthesized thin films were systematically and fully characterized. They featured ordered nanopores with porosity, pore diameter, and film thickness ranging from 30% to 59%, 0.5 to 25 nm, and 120 to 370 nm, respectively. Their dense matrix was amorphous, polycrystalline, or consisted of an aggregate of nanocrystals. The thermal conductivity of all synthesized nanoporous films increased monotonically with temperature within the temperature range considered. At low temperatures, the nanoporous films behaved like amorphous or strongly disordered materials and their thermal conductivity was proportional to T^n with n varied between 1 and 2.3. At high temperatures, the thermal conductivity increased slowly with temperature or reached a plateau due to strong phonon Umklapp scattering and the saturation of phonon modes. The presence of pores in amorphous mesoporous thin films had a purely geometrical effect by reducing the cross-sectional area through which heat can diffuse. By contrast, in crystalline mesoporous thin films the presence of pores also increased phonon scattering. In addition, the film thickness generally did not affect the measured thermal conductivity. Indeed, phonon scattering by pores and by nanocrystal grain boundary dominated over boundary scattering and were identified as the dominant scattering mechanisms for nanoscale energy transport in the synthesized nanoporous films. This study further establishes that the effective thermal conductivity keff of crystalline nanoporous silicon was strongly affected not only by the porosity fv and the system's length Lz but also by the pore interfacial area concentration Ai. A modified effective medium approximation combining kinetic theory and the coherent potential approximation suggested that keff was proportional to (1-1.5fv) and inversely proportional to the sum (Ai/4+1/Lz). This scaling law was in excellent agreement with the thermal conductivity of nanoporous silicon predicted by molecular dynamics simulations for spherical pores as well as for cylindrical pores and vacancy defects. Finally, this study demonstrated, using equilibrium molecular dynamics simulations, that surface passivation added another parameter for reducing the thermal conductivity of nanostructured materials. To do so, there should be strong acoustic vibrational modes coupling between surface and passivation atoms. For example, oxygen passivation reduced the thermal conductivity of nanoporous crystalline silicon. In addition, the effect of passivation reduced with temperature because of increasing contribution of Umklapp scattering. These results could help establish new strategies to control the thermal conductivity of nanoporous materials for a wide range of applications including thermoelectric devices, supercapacitors, dye-sensitized solar cells, and hydrogen storage devices.

Download or read book Nanostructured Thermoelectric Films written by Zhiyu Hu and published by Springer Nature. This book was released on 2020-07-10 with total page 275 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a range of low-dimensional superlattice thermoelectric materials based on physical vapor deposition (PVD) methods and explores various material types, thicknesses, and processing conditions. With the advances made in the performance of semiconductor thermoelectric materials and the efficiency of thermoelectric devices in recent years, thermoelectric power generation systems are likely to replace traditional mechanical heat engines, offering an environmentally friendlier alternative. The use of low-dimensional, nanostructured materials can significantly increase the density of states near the Fermi level and greatly improve the thermoelectric properties of materials. In addition, the book demonstrates that it is possible to influence thermoelectric performance, establish more accurate mathematical models through the regulation of relevant parameters, and ultimately improve the thermoelectric figure of merit (ZT).

Download or read book Thermal Energy Transport and Conversion in Disordered Materials written by Jianlin Zheng and published by . This book was released on 2018 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermal properties (thermal conductivity and specific heat) of the disordered materials, such as amorphous silicon (a-Si), polymer, and nano-crystalline semiconductors, are of significant interests for fundamental understanding of thermal transport process and for technical applications in thermal energy management and conversion. Due to the random distribution of atoms or molecules in disordered materials, the study of thermal transport is more challenging than that in crystalline materials. Understanding of the heat carrier transport behavior can be utilized to engineer the thermal properties in disordered materials, which can be applied for better devices thermal design and improving thermal energy conversion efficiency. We have studied the size dependent thermal conductivity of a-Si thin films and nanotubes, and observed unusually high and anisotropic thermal conductivity in the isotropic a-Si nanostructure. This manifests surprisingly broad mean free path distribution of the propagating modes (propagons), which is found to range from 10 nm to 10 [mu]m, in the disordered and isotropic structure. Constraining the long MFP propagons by boundary scattering in thin film and nanotubes explains the appreciable size effect in a-Si. Additionally, we developed a novel platform to measure the specific heat of low-dimensional disordered materials. By measuring the frequency dependent temperature rise data along the Nylon nanofibers (NFs), we are able to extract the specific heat and thermal conductivity simultaneously. While the thermal conductivity is increased by 50% over the bulk value in the 600 nm NFs, the specific heat exhibits bulk-like behavior. Finally we engineered the thermal conductivity in nano-crystalline bismuth-antimony-telluride (BST) by embedding SiO2 or diamond nanoparticles (NPs) at temperature below 300K, which has important application in thermoelectric cooling. We have shown that the embedded NPs work as additional scattering centers for lattice vibration (or called phonons), and can efficiently scatter the long MFP phonons in BST. We have observed 23% reduction of thermal conductivity, and 15% improvement of thermoelectric figure of merit (ZT) in the 0.5 vol. % Diamond NPs mixing sample, compared to the non-NPs nano-crystalline BST.

Download or read book Thermoelectric Bi2Te3 Nanomaterials written by Oliver Eibl and published by John Wiley & Sons. This book was released on 2015-04-23 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: Edited by the initiators of a priority research program funded by the German Science Foundation and written by an international team of key players, this is the first book to provide an overview of nanostructured thermoelectric materials -- putting the new developments into perspective alongside conventional thermoelectrics. As such, it reviews the current state of research on thermoelectric Bi2Te3 nanomaterials, covering advanced methods of materials synthesis, characterization of materials structures and thermoelectric properties, as well as advances in the theory and modeling of transport properties. Nanomaterials-based thermoelectric devices are also discussed with respect to their properties, their suitability for different energy generation applications, and in light of their commercialization potential. An outlook on the chances, challenges and future directions of research rounds off the book, giving a straightforward account of the fundamental and technical problems - plus ways to overcome them.

Download or read book Materials Preparation and Characterization in Thermoelectrics written by David Michael Rowe and published by CRC Press. This book was released on 2017-12-19 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book includes updated theoretical considerations which provide an insight into avenues of research most likely to result in further improvements in material performance. It details the latest techniques for the preparation of thermoelectric materials employed in energy harvesting, together with advances in the thermoelectric characterisation of nanoscale material. The book reviews the use of neutron beams to investigate phonons, whose behaviour govern the lattice thermal conductivity and includes a chapter on patents.

Download or read book Oxide Thin Films Multilayers and Nanocomposites written by Paolo Mele and published by Springer. This book was released on 2015-03-26 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive overview of the science of nanostructured oxides. It details the fundamental techniques and methodologies involved in oxides thin film and bulk growth, characterization and device processing, as well as heterostructures. Both, experts in oxide nanostructures and experts in thin film heteroepitaxy, contribute the interactions described within this book.

Download or read book Phonon Thermal Transport in Silicon Based Nanomaterials written by Hai-Peng Li and published by Springer. This book was released on 2018-09-08 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this Brief, authors introduce the advance in theoretical and experimental techniques for determining the thermal conductivity in nanomaterials, and focus on review of their recent theoretical studies on the thermal properties of silicon–based nanomaterials, such as zero–dimensional silicon nanoclusters, one–dimensional silicon nanowires, and graphenelike two–dimensional silicene. The specific subject matters covered include: size effect of thermal stability and phonon thermal transport in spherical silicon nanoclusters, surface effects of phonon thermal transport in silicon nanowires, and defects effects of phonon thermal transport in silicene. The results obtained are supplemented by numerical calculations, presented as tables and figures. The potential applications of these findings in nanoelectrics and thermoelectric energy conversion are also discussed. In this regard, this Brief represents an authoritative, systematic, and detailed description of the current status of phonon thermal transport in silicon–based nanomaterials. This Brief should be a highly valuable reference for young scientists and postgraduate students active in the fields of nanoscale thermal transport and silicon-based nanomaterials.

Download or read book Experimental and Theoretical Investigation of Thermal and Thermoelectric Transport in Nanostructures written by Arden Lot Moore and published by . This book was released on 2010 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work presents the development and application of analytical, numerical, and experimental methods for the study of thermal and electrical transport in nanoscale systems, with special emphasis on those materials and phenomena which can be important in thermoelectric and semiconductor device applications. Analytical solutions to the Boltzmann transport equation (BTE) using the relaxation time approximation (RTA) are presented and used to study the thermal and electrical transport properties of indium antimonide (InSb), indium arsenide (InAs), bismuth telluride (Bi2Te3), and chromium disilicide (CrSi2) nanowires. Experimental results for the thermal conductivity of single layer graphene supported by SiO2 were analyzed using an RTA-based model and compared to a full quantum mechanical numerical BTE solution which does not rely on the RTA. The ability of these models to explain the measurement results as well as differences between the two approaches are discussed. Alternatively, numerical solutions to the BTE may be obtained statistically through Monte Carlo simulation for complex geometries which may prove intractable for analytical methods. Following this approach, phonon transport in silicon (Si) sawtooth nanowires was studied, revealing that thermal conductivity suppression below the diffuse surface limit is possible. The experimental investigation of energy transport in nanostructures typically involved the use of microfabricated devices or non-contact optical methods. In this work, two such approaches were analyzed to ascertain their thermal behavior and overall accuracy as well as areas for possible improvement. A Raman spectroscopy-based measurement design for investigating the thermal properties of suspended and supported graphene was examined analytically. The resulting analysis provided a means of determining from measurement results the thermal interface conductance, thermal contact resistance, and thermal conductivity of the suspended and supported graphene regions. Previously, microfabricated devices of several different designs have been used to experimentally measure the thermal transport characteristics of nanostructures such as carbon nanotubes, nanowires, and thin films. To ascertain the accuracy and limitations of various microdevice designs and their associated conduction analyses, finite element models were constructed using ANSYS and measurements of samples of known thermal conductance were simulated. It was found that designs with the sample suspended were generally more accurate than those for which the sample is supported on a bridge whose conductance is measured separately. The effects of radiation loss to the environment of certain device designs were also studied, demonstrating the need for radiation shielding to be at temperatures close to that of the device substrate in order to accurately calibrate the resistance thermometers. Using a suspended microdevice like those analyzed using finite element analysis, the thermal conductivities of individual bismuth (Bi) nanowires were measured. The results were correlated with the crystal structure and growth direction obtained by transmission electron microscopy on the same nanowires. Compared to bulk Bi in the same crystal direction, the thermal conductivity of a single-crystal Bi nanowires of 232 nm diameter was found to be 3 - 6 times smaller than bulk between 100 K and 300 K. For polycrystalline Bi nanowires of 74 nm to 255 nm diameter the thermal conductivity was reduced by a factor of 18 - 78 over the same temperature range. Comparable thermal conductivity values were measured for polycrystalline nanowires of varying diameters, suggesting a grain boundary scattering mean free path for all heat carriers in the range of 15 - 40 nm which is smaller than the nanowire diameters. An RTA-based transport model for both charge carriers and phonons was developed which explains the thermal conductivity suppression in the single-crystal nanowire by considering diffuse phonon-surface scattering, partially diffuse surface scattering of electrons and holes, and scattering of phonons and charge carriers by ionized impurities such as oxygen and carbon of a concentration on the order of 1019 cm−3. Using a similar experimental setup, the thermoelectric properties (Seebeck coefficient, electrical conductivity, and thermal conductivity) of higher manganese silicide (HMS) nanostructures were investigated. Bulk HMS is a passable high temperature thermoelectric material which possesses a complex crystal structure that could lead to very interesting and useful nanoscale transport properties. The thermal conductivities of HMS nanowires and nanoribbons were found to be reduced by 50 - 60 % compared to bulk values in the same crystal direction for both nanoribbons and nanowires. The measured Seebeck coefficient data was comparable or below that of bulk, suggesting unintentional doping of the samples either during growth or sample preparation. Difficulty in determining the amorphous oxide layer thickness for nanoribbons samples necessitated using the total, oxide-included cross section in the thermal and electrical conductivity calculation. This in turn led to the determined electrical conductivity values representing the lower bound on the actual electrical conductivity of the HMS core. From this approach, the measured electrical conductivity values were comparable or slightly below the lower end of bulk electrical conductivity values. This oxide thickness issue affects the determination of the HMS nanostructure thermoelectric figure of merit ZT as well, though the lower bound values obtained here were found to still be comparable to or slightly smaller than the expected bulk values in the same crystal direction. Analytical modeling also indicates higher doping than in bulk. Overall, HMS nanostructures appear to have the potential to demonstrate measurable size-induced ZT enhancement, especially if optimal doping and control over the crystallographic growth direction can be achieved. However, experimental methods to achieve reliable electrical contact to quality four-probe samples needs to be improved in order to fully investigate the thermoelectric potential of HMS nanostructures.

Download or read book Thermal Radiative Wavelength Selectivity of Nanostructured Layered Media written by Yi Zheng and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermal radiative transport yields unique thermal characteristics of microscopic thin films-wavelength selectivity. This chapter focuses on a methodology about adjusting the wavelength selectivity of thin films embedded with nanoparticles in the far-field and near-field regimes. For nanostructured layered media doped with nanoparticles, Maxwell-Garnett-Mie theory is applied to determine the effective dielectric function for the calculation of radiative thermal transport. The thermal radiative wavelength selectivity can be affected by volume fraction and/or the size of the embedded nanoparticles in thin films. To characterize wavelength selectivity and optical property of nanostructured materials, both real and imaginary parts of effective refractive index need to be analyzed. It has been shown that the nanoparticles made of polar or metallic materials have different influence on thermal radiative wavelength selectivity of microscopic thin films.

Download or read book Thermal Phenomena in Nanostructured Materials and Devices written by Amy Marie Marconnet and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanostructuring leads to unique material properties and combinations of properties not naturally available in bulk materials. The study of these properties is critical to improving the device performance and reliability for a range of applications including electronics, thermoelectrics, and nanophotonics. This work focuses on efforts to push the thermal conductivity of nanostructured materials to the extremes: the thermal conductivity of carbon nanotubes (CNT) and nanotube-based materials can exceed that of metals, while the introduction of nanoscale boundaries (e.g. nanoscale pores in silicon nanowires) yields extremely low thermal conductivity materials. Furthermore, this nanostructuring also leads to unique combinations of properties. Porous silicon nanowires are a step towards the desired electron-crystal, phonon-glass combination ideal for thermoelectric applications, while thermally-conductive, mechanically-compliant carbon nanotube films for promising for electronics packaging. This work first explores how the high axial thermal conductivity of carbon nanotubes can be leveraged effectively in thin film and composites through detailed understanding of the phonon transport and measurements of CNT-based films. This work then investigates how nanostructuring silicon significantly reduces the thermal conductivity through enhanced boundary scattering and the possibility of phononic crystal effects. Specifically, measurements of individual, porous silicon nanowires and arrays of silicon nanowires show significant reduction in the thermal conductivity compared to bulk silicon. A detailed model for reduced thermal conductivity due to phonon boundary scattering is developed in conjunction with measurements. Finally, this work also examines how the composition and annealing conditions impact both thermal transport and photoluminescence in silicon-rich silicon nitride films.

Download or read book Novel Thermal Properties of Nanostructured Materials written by and published by . This book was released on 1999 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new class of heat transfer fluids, termed nanofluids, has been developed by suspending nanocrystalline particles in liquids. Due to the orders-of-magnitude larger thermal conductivities of solids compared to those of liquids such as water, significantly enhanced thermal properties are obtained with nanofluids. For example, an approximately 20% improvement in effective thermal conductivity is observed when 5 vol.% CuO nanoparticles are added to water. Even more importantly, the heat transfer coefficient of water under dynamic flow conditions is increased more than 15% with the addition of less than 1 vol.% CuO particles. The use of nanofluids could impact many industrial sectors, including transportation, energy supply and production, electronics, textiles, and paper production by, for example, decreasing pumping power needs or reducing heat exchanger sizes. In contrast to the enhancement in effective thermal transport rates that is obtained when nanoparticles are suspended in fluids, nanocrystalline coatings are expected to exhibit reduced thermal conductivities compared to coarse-grained coatings. Reduced thermal conductivities are predicted to arise because of a reduction in the mean free path of phonons due to presence of grain boundaries. This behavior, combined with improved mechanical properties, makes nanostructured zirconia coatings excellent candidates for future applications as thermal barriers. Yttria-stabilized zirconia (YSZ) thin films are being produced by metal-organic chemical vapor deposition techniques. Preliminary results have indicated that the thermal conductivity is reduced by approximately a factor-of-two at room temperature in 10 nm grain-sized YSZ compared to coarse-grained or single crystal YSZ.

Download or read book Nanostructured Thin Films written by Maria Benelmekki and published by Elsevier. This book was released on 2019-08-25 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanostructured Thin Films: Fundamentals and Applications presents an overview of the synthesis and characterization of thin films and their nanocomposites. Both vapor phase and liquid phase approaches are discussed, along with the methods that are sufficiently attractive for large-scale production. Examples of applications in clean energy, sensors, biomedicine, anticorrosion and surface modification are also included. As the applications of thin films in nanomedicine, cell phones, solar cell-powered devices, and in the protection of structural materials continues to grow, this book presents an important research reference for anyone seeking an informed overview on their structure and applications. Shows how thin films are being used to create more efficient devices in the fields of medicine and energy harvesting Discusses how to alter the design of nanostructured thin films by vapor phase and liquid phase methods Explores how modifying the structure of thin films for specific applications enhances their performance