Thermal Transport And Mechanical Properties Of Carbon Nanotube Arrays

Electronic Chip cooling has become an important issue with the ever increasing transistor densities and computing power demands. One of the crucial components of the thermal management system is high-performance thermal interface materials (TIMs), the materials connecting various solid-solid interfaces in packaged electronic devices. Ideal TIMs have the characteristics of high mechanical compliance and high intrinsic thermal conductivity. Vertically Aligned Carbon Nanotube (CNT) arrays are promising for advanced TIMs since they possesses both characters yet poor contact to the target surface can limit the overall performance. Recently, indium-assisted bonding has been found to enhance the contact conductance by a factor of 10, which inspires a comprehensive study of the CNT-array thermal transport properties. This thesis presents a systematic study on the thermal transport and mechanical properties of CNT arrays. The CNT array density and length are controlled via the thermal annealing duration and ethylene exposure duration in water-assisted chemical vapor deposition synthesis. The thermal transport properties are measured accurately by phase-sensitive photo thermal reflectance thermometry. The thermal contact conductance between CNT array and Glass increased close to linearly by increasing the volume fraction of the CNT array. The increase of volume fraction can potentially increase the number of contacting tubes which further enhance the contact area. In addition, the effective thermal conductivity increases monotonically with the increase of volume fraction of the CNT array. Quantitatively, it has been found that the increasing trend of thermal conductivity is larger than the increasing trend of volume fraction. The strain and buckling behavior of CNT arrays under compressive stress were systematically studied. It has been verified both experimentally and analytically that buckling in lower density CNT array results in a further decrease of thermal conductivity. The thermal conductivity of CNT array decreases as the structure changes from vertically aligned to buckled, while the thermal conductivity rises back as the buckling structure becomes more compact. The rise of thermal conductivity with the buckling structure is attributed to the rise of the thermal contact conductance between tubes. The thermal contact conductance between CNT array and glass increases as the compressive stress increases to certain degree, while further increase of stress causes fatigue at the contacts, which decreases the contact conductance. These results demonstrate how thermal transport properties vary as a function of CNT array density and as a function of the strain of CNT array. With such trends, the thermal properties can be further increased by understanding the underlying mechanisms for such trends.

This book shows the recent advances of the applications of carbon nanotubes (CNTs), in particular, the polymer functionalized carbon nanotubes. It also includes a comprehensive description of carbon nanotubes' preparation, properties, and characterization. Therefore, we have attempted to provide detailed information about the polymer-carbon nanotube composites. With regard to the unique structure and properties of carbon nanotubes, a series of important findings have been reported. The unique properties of carbon nanotubes, including thermal, mechanical, and electrical properties, after polymer functionalization have been documented in detail. This book comprises 18 chapters. The chapters include different applications of polymer functionalization CNTs, e.g. photovoltaic, biomedical, drug delivery, gene delivery, stem cell therapy, thermal therapy, biological detection and imaging, electroanalytical, energy, supercapacitor, and gas sensor applications.

Since their discovery in 1977, the evolution of conducting polymers has revolutionized modern science and technology. These polymers enjoy a special status in the area of materials science yet they are not as popular among young readers or common people when compared to other materials like metals, paper, plastics, rubber, textiles, ceramics and composites like concrete. Most importantly, much of the available literature in the form of papers, specific review articles and books is targeted either at advanced readers (scientists / technologists / engineers / senior academicians) or for those who are already familiar with the topic (doctoral / postdoctoral scholars). For a beginner or even school / college students, such compilations are bit difficult to access / digest. In fact, they need proper introduction to the topic of conducting polymers including their discovery, preparation, properties, applications and societal impact, using suitable examples and already known principles/knowledge/phenomenon. Further, active participation of readers in terms of "question & answers", "fill-in-the-blanks", "numerical" along with suitable answer key is necessary to maintain the interest and to initiate the "thought process". The readers also need to know about the drawbacks and any hazards of such materials. Therefore, I believe that a comprehensive source on the science / technology of conducting polymers which maintains a link between grass root fundamentals and state-of-the-art R&D is still missing from the open literature.

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.

Since their discovery more than a decade ago, carbon nanotubes (CNTs) have held scientists and engineers in captive fascination, seated on the verge of enormous breakthroughs in areas such as medicine, electronics, and materials science, to name but a few. Taking a broad look at CNTs and the tools used to study them, Carbon Nanotubes: Properties and Applications comprises the efforts of leading nanotube researchers led by Michael O’Connell, protégé of the late father of nanotechnology, Richard Smalley. Each chapter is a self-contained treatise on various aspects of CNT synthesis, characterization, modification, and applications. The book opens with a general introduction to the basic characteristics and the history of CNTs, followed by discussions on synthesis methods and the growth of “peapod” structures. Coverage then moves to electronic properties and band structures of single-wall nanotubes (SWNTs), magnetic properties, Raman spectroscopy of electronic and chemical behavior, and electromechanical properties and applications in NEMS (nanoelectromechanical systems). Turning to applications, the final sections of the book explore mechanical properties of SWNTs spun into fibers, sidewall functionalization in composites, and using SWNTs as tips for scanning probe microscopes. Taking a fresh look at this burgeoning field, Carbon Nanotubes: Properties and Applications points the way toward making CNTs commercially viable.

This book provides a single-source reference on the use of carbon nanotubes (CNTs) as interconnect material for horizontal, on-chip and 3D interconnects. The authors demonstrate the uses of bundles of CNTs, as innovative conducting material to fabricate interconnect through-silicon vias (TSVs), in order to improve the performance, reliability and integration of 3D integrated circuits (ICs). This book will be first to provide a coherent overview of exploiting carbon nanotubes for 3D interconnects covering aspects from processing, modeling, simulation, characterization and applications. Coverage also includes a thorough presentation of the application of CNTs as horizontal on-chip interconnects which can potentially revolutionize the nanoelectronics industry. This book is a must-read for anyone interested in the state-of-the-art on exploiting carbon nanotubes for interconnects for both 2D and 3D integrated circuits.

To improve the energy efficiency in many electronics and machinery applications, advanced Thermal Interface Materials (TIMs) with high heat dissipation ability and more pliability must be employed. Among a variety of promising choices to make the advanced TIMs, Vertically Aligned Carbon Nanotube (VACNT) turfs (arrays) outstand with their exceptional mechanical and thermal properties. Individual CNTs are quite flexible due to their quasi-one-dimensional structure and presence of strong sp2 bonds among the carbon atoms gives them great strength. Also, the dominance of ballistic phonon transport in the CNTs endows them superior thermal conductivity when compared to many metallic substrates. However, the defects in CNTs, misaligned axial contacts between CNTs in a CNT turf, and the CNTs/substrate resistance reduce the practical thermal conductivity of the material. It is hypothesized that the application of metal coatings on each CNT in a CNT turf would enhance the overall thermal conductivity of the material and improve the connectivity between the CNT turfs and the metallic substrate. As the diameter of the CNTs in a CNT turf is in the order of several nanometers, Molecular Dynamics (MD) atomistic simulations is selected as a tool which provide a deeper understanding in studying the thermal transport at the fundamental level. Thermal conduction in the metals is electron dominant whereas regular MD procedures are incapable of considering the energy exchange between these electrons and phonons. Therefore, a different mechanism called Two-temperature Model (TTM) coupled with Non-Equilibrium MD is used in this study and proved to be effective. MD code to procure the coefficient of thermal conductivity (kappa) was developed and the effects of the metal thickness, number of walls in the CNT and the role of diameter of CNT on kappa of the metal-coated CNTs was individually investigated. It was shown that the increase in the thickness of metal coating would impede the kappa of individual CNTs following an inverse power trend. Also, it was found that among the number of shells in the CNT and its diameter, the former parameter tends to contribute more towards the thermal transport than the latter. The results of this work are capable of predicting the optimal design structure for metal-coated VACNT composite for advanced thermal management applications.

Nanocomposites with Carbon-based nanofillers (e.g., carbon nanotubes, graphene sheets and nanoribbons etc.) form a class of extremely promising materials for thermal applications. In addition to exceptional material properties, the thermal conductivity of the carbon-based nanofillers can be higher than any other known material, suggesting the possibility to engineer nanocomposites that are both lightweight and durable, and have unique thermal properties. This potential is hindered by thermal boundary resistance (TBR) to heat transfer at the interface between nanoinclusions and the matrix, and by the difficulty to control the dispersion pattern and the orientation of the nanoinclusions. Thermal Behaviour and Applications of Carbon-Based Nanomaterials: Theory, Methods and Applications explores heat transfer in nanocomposites, discusses techniques predicting and modeling the thermal behavior of carbon nanocomposites at different scales, and methods for engineering applications of nanofluidics and heat transfer. The chapters combine theoretical explanation, experimental methods and computational analysis to show how carbon-based nanomaterials are being used to optimise heat transfer. The applications-focused emphasis of this book makes it a valuable resource for materials scientists and engineers who want to learn more about nanoscale heat transfer. Offers an informed overview of how carbon nanomaterials are currently used for nanoscale heat transfer Discusses the major applications of carbon nanomaterials for heat transfer in a variety of industry sectors Details the major computational methods for the analysis of the thermal properties of carbon nanomaterials

This Handbook covers the fundamentals of carbon nanotubes (CNT), their composites with different polymeric materials (both natural and synthetic) and their potential advanced applications. Three different parts dedicated to each of these aspects are provided, with chapters written by worldwide experts in the field. It provides in-depth information about this material serving as a reference book for a broad range of scientists, industrial practitioners, graduate and undergraduate students, and other professionals in the fields of polymer science and engineering, materials science, surface science, bioengineering and chemical engineering. Part 1 comprises 22 chapters covering early stages of the development of CNT, synthesis techniques, growth mechanism, the physics and chemistry of CNT, various innovative characterization techniques, the need of functionalization and different types of functionalization methods as well as the different properties of CNT. A full chapter is devoted to theory and simulation aspects. Moreover, it pursues a significant amount of work on life cycle analysis of CNT and toxicity aspects. Part 2 covers CNT-based polymer nanocomposites in approximately 23 chapters. It starts with a short introduction about polymer nanocomposites with special emphasis on CNT-based polymer nanocomposites, different manufacturing techniques as well as critical issues concerning CNT-based polymer nanocomposites. The text deeply reviews various classes of polymers like thermoset, elastomer, latex, amorphous thermoplastic, crystalline thermoplastic and polymer fibers used to prepare CNT based polymer composites. It provides detailed awareness about the characterization of polymer composites. The morphological, rheological, mechanical, viscoelastic, thermal, electrical, electromagnetic shielding properties are discussed in detail. A chapter dedicated to the simulation and multiscale modelling of polymer nanocomposites is an additional attraction of this part of the Handbook. Part 3 covers various potential applications of CNT in approximately 27 chapters. It focuses on individual applications of CNT including mechanical applications, energy conversion and storage applications, fuel cells and water splitting, solar cells and photovoltaics, sensing applications, nanofluidics, nanoelectronics and microelectronic devices, nano-optics, nanophotonics and nano-optoelectronics, non-linear optical applications, piezo electric applications, agriculture applications, biomedical applications, thermal materials, environmental remediation applications, anti-microbial and antibacterial properties and other miscellaneous applications and multi-functional applications of CNT based polymer nanocomposites. One chapter is fully focussed on carbon nanotube research developments: published papers and patents. Risks associated with carbon nanotubes and competitive analysis of carbon nanotubes with other carbon allotropes are also addressed in this Handbook.

This discovery of carbon nanotubes (CNT) three decades ago ushered in the technological era of nanotechnology. Among the most widely studied areas of CNT research is their use as structural reinforcements in composites. This book describes the development of CNT reinforced metal matrix composites (CNT-MMCs) over the last two decades. The field of CNT-MMCs is abundant in fundamental science, rich in engineering challenges and innovations and ripe for technological maturation and commercialization. The authors have sought to present the current state of the-art in CNT-MMC technology from their synthesis to their myriad potential end-use applications. Specifically, topics explored include: • Advantages, limitations, and evolution of processing techniques used to synthesize and fabricate CNT-MMCs • Emphasizes dispersion techniques of CNTs in metallic systems, a key challenge to the successful and widespread implementation of CNT-MMCs. Methods for quantification and improved control of CNT distributions are presented • Methods for quantification and improved control of CNT distributions are presented • Characterization techniques uniquely suited for charactering these nanoscale materials and their many chemical and physical interactions with the metal matrix, including real-time in-situ characterization of deformation mechanisms • Electron microscope images from premier studies enrich discussions on micro-mechanical modeling, interfacial design, mechanical behavior, and functional properties • A chapter is dedicated to the emergence of dual reinforcement composites that seek to enhance the efficacy of CNTs and lead to material properties by design This book highlights seminal findings in CNT-MMC research and includes several tables listing processing methods, associated CNT states, and resulting properties in order to aid the next generation of researchers in advancing the science and engineering of CNT-MMCs. In addition, a survey of the patent literature is presented in order to shed light on what the first wave of CNT-MMC commercialization may look like and the challenges that will have to be overcome, both technologically and commercially.