Download or read book A Temperature Dependent Study of Phonons and the Thermal Conductivity of Boron Arsenide written by and published by . This book was released on 2008 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Phonon Transport in Ultrahigh and Ultralow Thermal Conductivity Materials written by Joonsang Kang and published by . This book was released on 2019 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced materials with extreme thermal conductivity are critically important for various technological applications including energy conversion, storage, and thermal management. Low thermal conductivity is needed for thermal insulation and thermoelectric energy harvesting, while high thermal conductivity is desirable for efficient heat spreading in electronics. However, practical application deployments are usually limited by the materials availability in nature. Moreover, understanding the fundamental origins for extreme thermal conductivity still remains challenging. My PhD research focuses on finding new thermal materials and unveiling fundamental phonon transport mechanisms in extreme thermal conductivity matters to push the frontier of thermal science. My dissertation is composed of three topics. The first topic is focused on developing and investigating a new group of ultrahigh conductivity materials. High-quality boron phosphide (BP) and boron arsenide (BAs) crystal are synthesized and measured with thermal conductivities of 460 and 1300 W/mK, respectively. In particular, our result shows that BAs is the best thermal conductor among common bulk metals and semiconductors. To better understand the fundamental origin of such an ultrahigh thermal conductivity, advanced phonon spectroscopy and temperature dependent characterizations are performed. Our measurements, in conjunction with atomistic theory, reveal that, unlike the commonly accepted rule for most materials near room temperature, high-order anharmonicity through the four-phonon process is significant in BA because of its unique band structure. Our result underscores the promise of using BP and BAs for thermal management and develops microscopic understanding of the phonon transport mechanisms. The second topic of my thesis is to investigate phonon transport in ultralow thermal conductivity material with a focus on tin selenide (SnSe). SnSe is a recently discovered material for high performance thermoelectricity. However, the thermal properties of intrinsic SnSe remain elusive in literature. To understand the dominant phonon transport mechanisms for the extremely low thermal conductivity of SnSe, temperature-dependent sound velocity, lattice expansion, and Gr neisen parameter was measured. The measurement result shows that high-order anharmonicity introduces strong phonon renormalization and the ultralow thermal conductivity. The third topic of the thesis is to investigate in-situ dynamic tuning of thermal conductivity in layered materials. A novel device platform based on lithium ion battery is developed to characterize the interactions between ions and phonons of layered materials. We observe a highly reversible modulation and anisotropy of thermal conductivity from phonon scattering introduced by ionic intercalation in the interspacing layers. This study provides a unique approach to explore the fundamental energy transport involving lattices and ions and open up new opportunities in thermal engineering.
Download or read book Peak Thermal Conductivity Measurements of Bulk Boron Arsenide Crystals and Individual Carbon Nanotubes written by Yuanyuan Zhou and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: High-thermal conductivity materials are useful for thermal management applications and fundamental studies of phonon transport. Conventional criteria suggests high thermal conductivity only exists in strongly bonded simple crystal structures of light elements, such as diamond, graphite, graphene, and carbon nanotubes (CNTs). In comparison, recent theories and experiments have shown zincblende boron Arsenide (BAs) as the first known semiconductor with a room-temperature thermal conductivity close to 1000 W m−1 K−1. The unusual high thermal conductivity is achieved via an unconventional route based on isotopically pure heavy atom and a large mass ratio of constituent atoms, the latter of which results in a large energy gap between the acoustic and option phonon polarizations and bunching of the acoustic phonon dispersions. These features in the phonon band structure limit three-phonon scattering and scattering by isotopic impurities. Past measurements of several ultrahigh thermal conductivity materials, including BAs bulk crystals, were not able to obtain the peak thermal conductivity, which is expected to appear at a low temperature and contains insight into the competition between extrinsic phonon-defect and phonon-boundary scattering with intrinsic phonon-phonon processes. Meanwhile, past thermal conductivity measurements of CNTs are subjected to errors caused by contact thermal resistance. The observed peak temperatures are much higher than those reported for bulk graphite. The results suggest that extrinsic phonon scattering mechanisms dominate intrinsic phonon-phonon scattering that is predicted to give rise to non-diffusive phonon transport phenomena including hydrodynamic, ballistic, and quantized phonon transport regimes. Here we report a peak thermal conductivity measurement method based on differential Wheatstone bridge measurements of the small temperature drop between two thin film resistance thermometers patterned directly on a bulk sample. With the use of a mesoscale silicon bar sample as the calibration standard, this method is able to obtain results that agree with past measurements of large bulk silicon crystals at high temperatures and first principles calculation results that accounts for additional phonon-boundary scattering in the sample. The agreement demonstrates the accuracy of this measurement method for peak thermal conductivity measurements of high-thermal conductivity materials. This method was employed to measure the peak thermal conductivity of several BAs crystals. In addition, a multi-probe thermal transport measurement method was used to determine both the contact thermal resistance and the intrinsic thermal conductance of different segments of the same individual multi-walled CNT samples simultaneously and directly. The differential thin film resistance thermometry method is expected to address the need of accurate peak thermal conductivity measurement methods and find use in the ongoing search of high-thermal conductivity materials for thermal management. The obtained peak thermal conductivity measurements of BAs can help to advance the understanding of phonon scatterings by phonons, boundaries, and defects in ultrahigh thermal conductivity materials. The thermal transport measurement of CNTs validates the multi-probe method for probing intrinsic thermal conductivity of nanostructures, and can provide an essential tool for further studying hydrodynamic, ballistic, and quantized phonon transport phenomena in high-quality CNTs and other low-dimensional structures
Download or read book The Boron Arsenides written by David J. Fisher and published by Materials Research Forum LLC. This book was released on 2023-01-25 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: Boron Arsenide offers very interesting electronic properties, as well as a high thermal conductivity; nearly 10 times higher than that of silicon. It has been hailed as ‘the best semiconductor material ever found’. The present book presents a detailed review of this material and its potential applications. The materials covered include Icosahedral Boron Arsenide, Hexagonal Boron Arsenide, Amorphous Boron Arsenide and Cubic Boron Arsenide. The book references 166 original resources with their direct web links for in-depth reading. Keywords: Boron Arsenides, Electron Mobility, Hole Mobility, Band-gap, Monolayers, Defects, Mechanical Properties, Photo-electrodes, Thermal Conductivity, Heat-spreading.
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1976 with total page 964 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studying Phonon Mean Free Paths at the Nanoscale written by Lingping Zeng and published by . This book was released on 2016 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: Heat conduction in semiconductors and dielectrics involves cumulative contributions from phonons with different frequencies and mean free paths (MFPs). Knowing the phonon MFP distribution allows us to gain insight into the fundamental microscopic transport physics and has important implications for many energy applications. The key metric that quantifies the relative contributions of different phonon MFPs to thermal conductivity is termed thermal conductivity accumulation function. In this thesis, we advance a thermal conductivity spectroscopy technique based upon experimental observation of non-diffusive thermal transport using wire grid linear polarizer in conjunction with time-domain thermoreflectance (TDTR) pump-and-probe measurement setup. Consistent algorithm based on solution from the phonon Boltzmann transport equation (BTE) is also developed to approximately extract the thermal conductivity accumulation functions in materials studied. The heat flux suppression function appropriate for the experimental sample geometry relates the measured apparent thermal conductivities to the material's phonon MFP distributions. We develop a multi-dimensional thermal transport model based on the gray phonon BTE to find the suppression function relevant to our spectroscopy experiment. The simulation results reveal that the suppression function depends upon both the heater size and the heater array period. We also find that the suppression function depends significantly on the location of the temperature measurement. Residual suppression effect is observed for finite filling fractions (ratio of heater size to heater array period) due to the transport coupling in the underlying substrate induced by the neighboring heaters. Prior phonon MFP spectroscopy techniques suffer from one or several of the following limitations: (1) diffraction limited to micrometer lengthscales by focusing optics, (2) applying only to transparent materials, or (3) involving complex micro-fabrications. We explore an alternate approach here using wire grid linear polarizer in combination with TDTR measurement. The wire grid polarizer is designed with sub-wavelength gaps between neighboring heaters to prevent direct photo-excitation in the substrate while simultaneously functioning as heaters and thermometers during the measurement. The spectroscopy technique is demonstrated in crystalline silicon by studying length-dependent thermal transport across a range of lengthscales and temperatures. We utilize the calculated heat flux suppression functions and the measured size-dependent effective thermal conductivities to reconstruct the phonon MFPs in silicon and achieve reasonably good agreement with calculation results from first principle density function theory. Knowledge of phonon MFP distributions in thermoelectric materials will help design nanostructures to further reduce lattice thermal conductivity to achieve better thermoelectric performance in the next-generation thermoelectric devices. We apply the developed wire grid polarizer spectroscopy technique to study phonon MFP distributions in two thermoelectric materials: Nb0.95 Ti0.05FeSb and boron-doped nanocrystalline Si80Ge20B. We find that the dominant phonon MFPs that contribute to thermal conductivity in those two materials are in the a few tens to a few hundreds of nanometers. The measurement results also shed light on why nanostructuring is an effective approach to scattering phonons and improve the thermoelectric behavior.
Download or read book Modeling Characterization and Production of Nanomaterials written by Vinod Tewary and published by Woodhead Publishing. This book was released on 2022-11-09 with total page 628 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nano-scale materials have unique electronic, optical, and chemical properties that make them attractive for a new generation of devices. In the second edition of Modeling, Characterization, and Production of Nanomaterials: Electronics, Photonics, and Energy Applications, leading experts review the latest advances in research in the understanding, prediction, and methods of production of current and emerging nanomaterials for key applications. The chapters in the first half of the book cover applications of different modeling techniques, such as Green’s function-based multiscale modeling and density functional theory, to simulate nanomaterials and their structures, properties, and devices. The chapters in the second half describe the characterization of nanomaterials using advanced material characterization techniques, such as high-resolution electron microscopy, near-field scanning microwave microscopy, confocal micro-Raman spectroscopy, thermal analysis of nanoparticles, and applications of nanomaterials in areas such as electronics, solar energy, catalysis, and sensing. The second edition includes emerging relevant nanomaterials, applications, and updated modeling and characterization techniques and new understanding of nanomaterials. Covers the close connection between modeling and experimental methods for studying a wide range of nanomaterials and nanostructures Focuses on practical applications and industry needs through a solid outlining of the theoretical background Includes emerging nanomaterials and their applications in spintronics and sensing
Download or read book Boron Rich Solids written by David Emin and published by AIP Conference Proceedings (Nu. This book was released on 1991 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Contribution of Longitudinal Phonons to the Lattice Thermal Conductivity written by Raul Adriano Brito Orta and published by . This book was released on 1982 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Physics of Phonons written by Gyaneshwar P. Srivastava and published by Routledge. This book was released on 2019-07-16 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt: There have been few books devoted to the study of phonons, a major area of condensed matter physics. The Physics of Phonons is a comprehensive theoretical discussion of the most important topics, including some topics not previously presented in book form. Although primarily theoretical in approach, the author refers to experimental results wherever possible, ensuring an ideal book for both experimental and theoretical researchers. The author begins with an introduction to crystal symmetry and continues with a discussion of lattice dynamics in the harmonic approximation, including the traditional phenomenological approach and the more recent ab initio approach, detailed for the first time in this book. A discussion of anharmonicity is followed by the theory of lattice thermal conductivity, presented at a level far beyond that available in any other book. The chapter on phonon interactions is likewise more comprehensive than any similar discussion elsewhere. The sections on phonons in superlattices, impure and mixed crystals, quasicrystals, phonon spectroscopy, Kapitza resistance, and quantum evaporation also contain material appearing in book form for the first time. The book is complemented by numerous diagrams that aid understanding and is comprehensively referenced for further study. With its unprecedented wide coverage of the field, The Physics of Phonons will be indispensable to all postgraduates, advanced undergraduates, and researchers working on condensed matter physics.
Download or read book Phonon Transport in Barium Titanate and Rutile written by Alexander Johan Hendrik Mante and published by . This book was released on 1970 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book 21st Century Nanoscience written by Klaus D. Sattler and published by CRC Press. This book was released on 2022-01-18 with total page 4153 pages. Available in PDF, EPUB and Kindle. Book excerpt: This 21st Century Nanoscience Handbook will be the most comprehensive, up-to-date large reference work for the field of nanoscience. Handbook of Nanophysics, by the same editor, published in the fall of 2010, was embraced as the first comprehensive reference to consider both fundamental and applied aspects of nanophysics. This follow-up project has been conceived as a necessary expansion and full update that considers the significant advances made in the field since 2010. It goes well beyond the physics as warranted by recent developments in the field. Key Features: Provides the most comprehensive, up-to-date large reference work for the field. Chapters written by international experts in the field. Emphasises presentation and real results and applications. This handbook distinguishes itself from other works by its breadth of coverage, readability and timely topics. The intended readership is very broad, from students and instructors to engineers, physicists, chemists, biologists, biomedical researchers, industry professionals, governmental scientists, and others whose work is impacted by nanotechnology. It will be an indispensable resource in academic, government, and industry libraries worldwide. The fields impacted by nanoscience extend from materials science and engineering to biotechnology, biomedical engineering, medicine, electrical engineering, pharmaceutical science, computer technology, aerospace engineering, mechanical engineering, food science, and beyond.
Download or read book Phonon Scattering Processes and Thermal Conduction in Copper Alloys at Very Low Temperatures written by Alan Charles Bouley and published by . This book was released on 1977 with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Thermal Management Materials for Electronic Packaging written by Xingyou Tian and published by John Wiley & Sons. This book was released on 2023-12-11 with total page 373 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermal Management Materials for Electronic Packaging Practical resource exploring the theoretical and experimental basis as well as solutions for the development of new thermal management materials for electronic packaging Thermal Management Materials for Electronic Packaging: Preparation, Characterization, and Devices provides in-depth and systematic summaries on cutting-edge thermal management materials for high-power density electronic devices, introducing the preparation methods and application scenarios of thermal management materials for electronic packing, covering refinements of thermal conductivity theory and performance prediction models for multiphase composites, and overall focusing on key scientific issues related to the subject, such as the internal interface of new high thermal conductive substrate materials and the mechanism of spatial topology on performance. The text also discusses key issues on the design and preparation of thermal conductive substrate materials with high thermal conductive properties, including their characterization, properties, and manipulation, as well as the latest methods, techniques, and applications in this rapidly developing area. Sample topics covered in Thermal Management Materials for Electronic Packaging include: Basic concepts and laws of thermal conduction, heat conduction differential equation and finite solution, and thermal conductivity of solids Definition and classification of electronic packaging, thermal management in electronic equipment, and requirements of electronic packaging materials Synthesis and surface modification of high thermal conductive filler and the synthesis of substrates and preparation of thermal conductive composites with inorganic ceramic skeleton structure Assembly of thermal conductive materials in different dimensions and preparation of composite materials, and reliability analysis and environmental performance evaluation Thermal Management Materials for Electronic Packaging serves as an ideal reference for researchers and workers in related fields to significantly improve the mechanical and thermal management properties of materials, expand the material selection and design margin of substrates, and develop substrates that meet the application needs of different gradients.
Download or read book Monte Carlo Study of Phonon Heat Conduction in Silicon Thin Films written by Arpit Mittal and published by . This book was released on 2009 with total page 85 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Heat conduction in crystalline semiconductor materials occurs by lattice vibrations that result in the propagation of quanta of energy called phonons. The Boltzmann Transport Equation (BTE) for phonons is a powerful tool to model both equilibrium and non-equilibrium heat conduction in crystalline solids. Non-equilibrium heat conduction occurs either when the length scales (of the device in question) are small or at low temperatures. The BTE describes the evolution of the number density (or energy) distribution for phonons as a result of transport (or drift) and inter-phonon collisions. The Monte-Carlo (MC) method has found prolific use in the solution of the Boltzmann Transport Equation (BTE) for phonons. This thesis contributes to the state-of-the-art by performing a systematic study of the role of the various phonon modes on thermal conductivity predictions-in particular, optical phonons. A procedure to calculate three-phonon scattering time-scales with the inclusion of optical phonons is described and implemented. The roles of various phonon modes are assessed. It is found that Transverse Acoustic (TA) phonons are the primary carriers of energy at low temperatures. At high temperatures (T> 200 K), Longitudinal Acoustic (LA) phonons carry more energy than TA phonons. When optical phonons are included, there is a significant change in the amount of energy carried by various phonons modes, especially at room temperature, where optical modes are found to carry about 25% of the energy at steady state in silicon thin films. Most importantly, it is found that inclusion of optical phonons results in better match with experimental observations for silicon thin-film thermal conductivity. The inclusion of optical phonons is found to decrease the thermal conductivity at intermediate temperatures (50-200 K) and increase it at high temperature (>200 K), especially when the film is thin. The effect of number of stochastic samples, the dimensionality of the computational domain (two-dimensional versus three-dimensional), and the lateral (in-plane) dimension of the film on the statistical accuracy and computational efficiency is systematically studied and elucidated for all temperatures. For thin film thermal conductivity predictions, it has been found that the dimensionality of the computational domain has no impact on the accuracy of the numerical solution. In the diffusion dominated regime, three-dimensional Monte-Carlo calculations are found to be comparable to two-dimensional Monte-Carlo calculations in terms of computational efficiency. It has also been found that irrespective of dimensionality of the computational domain, the impact of the size of the lateral boundaries can be accounted for by tuning the resistance provided by the boundaries, i.e., the degree of specularity. It is also shown that the time averaging of the statistically stationary data can be used to reduce statistical noise and can result in considerable computational savings.
Download or read book Luminescence Thermometry written by Miroslav Dramićanin and published by Woodhead Publishing. This book was released on 2018-04-21 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: Luminescence Thermometry: Methods, Materials, and Applications presents the state-of-the art applications of luminescence thermometry, giving a detailed explanation of luminescence spectroscopic schemes for the read-out of temperature, while also describing the diverse materials that are capable of sensing temperature via luminescence. Chapters cover the fundamentals of temperature, traditional thermometers and their figures of merit, a concise description of optical thermometry methods, luminescence and instrumentation, and an explanation of the ways in which increases in temperature quench luminescence. Additional sections focus on materials utilized for luminescence thermometry and the broad range of applications for luminescence thermometry, including temperature measurement at the nanoscale and the application of multifunctional luminescent materials. Provides an overview of luminescence thermometry applications, including high-temperature, biomedical, nanoscale and multifunctional Delves into luminescence thermometry by materials group, including Rare-earth and transition Metal Ion Doped, Semiconductors, Quantum Dots and Organic materials Gives a concise introduction of the latest methods of temperature measurement, including luminescence spectroscopic schemes and methods of analysis
Download or read book Nanoscale Energy Transport written by LIAO and published by IOP Publishing Limited. This book was released on 2020-03-20 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book brings together leading names in the field of nanoscale energy transport to provide a comprehensive and insightful review of this developing topic. The text covers new developments in the scientific basis and the practical relevance of nanoscale energy transport, highlighting the emerging effects at the nanoscale that qualitatively differ from those at the macroscopic scale. Throughout the book, microscopic energy carriers are discussed, including photons, electrons and magnons. State-of-the-art computational and experimental nanoscale energy transport methods are reviewed, and a broad range of materials system topics are considered, from interfaces and molecular junctions to nanostructured bulk materials. Nanoscale Energy Transport is a valuable reference for researchers in physics, materials, mechanical and electrical engineering, and it provides an excellent resource for graduate students.
