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In this study, vertically aligned multiwalled carbon nanotube films were grown by microwave plasma chemical vapor deposition (MWCVD). Through controlling the thickness of the iron thin film, carbon nanotubes with different diameters were obtained. When the thickness of the iron layer was reduced to 0.3-0.5 nm, single-wall and double-wall nanotubes were obtained with a high areal density (~ 1012/cm2) and vertical alignment. Scanning electron microscopy, Raman spectroscopy and high resolution transmission electron microscopy were employed to characterize the as-deposited nanotubes. In addition, a systematic study of the internal structure transition of the carbon nanotubes has been conducted and a growth model was proposed in terms of carbon surface and bulk diffusion. The field emission of the carbon nanotube films has also been explored in this study. Different measurement systems including a variable distance field emission system, a field emission imaging system, and a field electron emission system (FEEM) were employed. The effects of the diameter (multi-wall vs single- and double- wall), the adsorbates, and the temperature on the field emission properties of carbon nanotubes have been exhibited. Finally, two processes including hydrogen plasma etching and re-growth were used to treat the as-deposited film, and an increased emission site density was observed for the re-grown carbon nanotube film.
Carbon nanotubes (CNTs) have novel properties that make them potentially useful in many applications in nanotechnology, electronics, optics and other fields of materials science. These characteristics include extraordinary strength, unique electrical properties, and the fact that they are efficient heat conductors. Field emission is the emission of electrons from the surface of a condensed phase into another phase due to the presence of high electric fields. CNT field emitters are expected to make a breakthrough in the development of field emission display technology and enable miniature X-ray sources that will find a wide variety of applications in electronic devices, industry, and medical and security examinations. This first monograph on the topic covers all aspects in a concise yet comprehensive manner - from the fundamentals to applications. Divided into four sections, the first part discusses the preparation and characterization of carbon nanotubes, while part two is devoted to the field emission properties of carbon nanotubes, including the electron emission mechanism, characteristics of CNT electron sources, and dynamic behavior of CNTs during operation. Part three highlights field emission from other nanomaterials, such as carbon nanowalls, diamond, and silicon and zinc oxide nanowires, before concluding with frontier R&D applications of CNT emitters, from vacuum electronic devices such as field emission displays, to electron sources in electron microscopes, X-ray sources, and microwave amplifiers. Edited by a pioneer in the field, each chapter is written by recognized experts in the respective fields.
Carbon nanotubes represent one of the most exciting research areas in modern science. These molecular-scale carbon tubes are the stiffest and strongest fibres known, with remarkable electronic properties, and potential applications in a wide range of fields. Carbon Nanotube Science is a concise, accessible book, presenting the basic knowledge that graduates and researchers need to know. Based on the successful Carbon Nanotubes and Related Structures, this book focuses solely on carbon nanotubes, covering the major advances made in recent years in this rapidly developing field. Chapters focus on electronic properties, chemical and bimolecular functionalisation, nanotube composites and nanotube-based probes and sensors. The book begins with a comprehensive discussion of synthesis, purification and processing methods. With its comprehensive coverage of this active research field, this book will appeal to researchers in a broad range of disciplines, including nanotechnology, engineering, materials science and physics.
Carbon nanotubes (CNTs) are known to have exceptional field emission properties such as low turn-on voltage and high current density. Nilsson et al. reported that field emission properties depend highly on the density of the CNT films. The CNTs must have low density in order to minimize electrostatic field screening from neighboring nanotubes. At the same time, the CNT films must have a high number of emitting sites to achieve a desirable current density. Recently, the direct growth of CNTs on metal alloys containing Ni, Cr, and Fe has been shown to be an attractive alternative for fabrication of CNT emitters without requiring a metal catalyst deposition step. Herein, we report the field emission properties of multi-walled carbon nanotube (MWNT) films grown on polished smooth 80/20 and 70/30 NiCr surfaces by thermal chemical vapor deposition. We show that 80/20 NiCr surfaces prohibit growth of MWNTs at the grain boundaries resulting in a lower turn-on field in comparison to a continuous MWNT film obtained with 70/30 NiCr substrates.
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.
Carbon nanotubes are one of the most intriguing new materials with extraordinary properties being discovered in the last decade. The unique structure of carbon nanotubes provides nanotubes with extraordinary mechanical and electrical properties. The outstanding properties that these materials possess have opened new interesting researches areas in nanoscience and nanotechnology. Although nanotubes are very promising in a wide variety of fields, application of individual nanotubes for large scale production has been limited. The main roadblocks, which hinder its use, are limited understanding of its synthesis and electrical properties which lead to difficulty in structure control, existence of impurities, and poor processability. This book makes an attempt to provide indepth study and analysis of various synthesis methods, processing techniques and characterization of carbon nanotubes that will lead to the increased applications of carbon nanotubes.