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Author : Martin Dionne
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (713 download)
Download or read book Optimized Carbon Nanotube Array Cathodes for Thermo-field Emission in Plasmas written by Martin Dionne and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : M. Cahay
Publisher : The Electrochemical Society
ISBN 13 : 9781566773423
Total Pages : 432 pages
Book Rating : 4.7/5 (734 download)
Download or read book Cold Cathodes II written by M. Cahay and published by The Electrochemical Society. This book was released on 2002 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Niraj Sinha
Publisher :
ISBN 13 : 9780494433478
Total Pages : 161 pages
Book Rating : 4.4/5 (334 download)
Download or read book Characterization of Carbon Nanotube Based Thin Film Field Emitter written by Niraj Sinha and published by . This book was released on 2008 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, carbon nanotubes (CNTs) have emerged as one of the best field emitters for a variety of technological applications. The field emitting cathodes have several advantages over the conventional thermionic cathodes: (i) current density from field emission would be orders of magnitude greater than in the thermionic case, (ii) a cold cathode would minimize the need for cooling, and (iii) a field emitting cathode can be miniaturized. In spite of good performance of such cathodes, the procedure to estimate the device current is not straight forward and the required insight towards design optimization is not well understood. In addition, the current in CNT-based thin film devices shows fluctuation. Such fluctuation in field emission current is not desirable for many biomedical applications such as x-ray devices. The CNTs in a thin film undergo complex dynamics during field emission, which includes processes such as (i) evolution, (ii) electromechanical interaction, (iii) thermoelectric heating, (iv) ballistic transport, and (v) electron gas flow. These processes are coupled and nonlinear. Therefore, they must be analyzed accurately from the stability and long-term performance point of view. In this research, we develop detailed physics-based models of CNTs considering the aspects mentioned above.
Author : Jianfeng Wu
Publisher :
ISBN 13 :
Total Pages : 143 pages
Book Rating : 4.:/5 (668 download)
Download or read book Fabrication, Field Emission Properties and Theoretical Simulation of Triode-type Carbon Nanotube Emitter Arrays written by Jianfeng Wu and published by . This book was released on 2010 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes exhibit excellent field emission properties and will likely be prime candidates as electron sources in future vacuum electronic applications. Recent research has focused on enhancing field emission from traditional diode-type emitters by adding a gate electrode between the anode and the cathode. Since the gate to cathode (emitter) distance in this triode-type structure is small relative to the anode to cathode distance, this structure allows relatively small gate voltages to significantly enhance or dampen field emission. The key challenge for this research is: synthesizing vertically aligned carbon nanotube field emitters inside arrays of triode-type devices. The most common "top-down", etch-deposit-synthesis method of synthesizing carbon nanotubes inside gated cavities is discussed here, and a novel "bottom-up" method is presented. This new approach bypasses the lithography and wet chemistry essential to the etch-deposit-synthesis method, instead using a dual-beam focused ion beam (FIB) system to mill cavities into a multi-layered substrate. Here the substrate is designed such that the act of milling a hole simultaneously creates the gate structure and exposes the catalyst from which carbon nanotubes can then be grown. Carbon nanotubes are synthesized using plasma enhanced chemical vapor deposition (PECVD) rather than thermal chemical vapor deposition, due to the superior alignment of the PECVD growth. As dual-beam FIB and PECVD can both be largely computerized, this synthesis method is highly reproducible. The dual-beam FIB also permits a high degree of controllability in gate radius, cavity depth and emitter spacing. The effects of a host of PECVD growth parameters (initial catalyst thickness, gas concentration, growth temperature, temperature ramping rate, chamber pressure, and plasma voltage) were characterized so that the morphology of the carbon nanotube emitters could be controlled as well. This "bottom-up" method is employed to construct functional, large area carbon nanotube field emitter arrays (CNT FEAs). The role of the gate layer in field emission is examined experimentally as well as through theoretical models. Field emission testing revealed that increasing gate voltage by as little as 0.3 V had significant impact on the local electric fields, lowering the turn-on and threshold fields by 3.6 and 3.0 V/um, respectively, and increasing the field enhancement factor from 149 to 222. A quantum mechanical model of such triode-type field emission indicates that the local electric field generated by a negatively or positively biased gate directly impacts the tunneling barrier thickness and thus the achievable emission current. However, the geometry of triode-type devices (gate height, gate radius, emitter density) can influence the degree to which the gate voltage influences field emission. I demonstrate here an effective method of analytically calculating the effect of various such geometric parameters on the field emission. Results show that gate type (the height of the gate relative the emitter tip) can significantly impact the local electric field and hence the type of applications a device is suitable for. Side gates (gate height emitter height) induced the highest local electric field, while top gates (gate height emitter height) provided the greatest controllability. For all gate types, increasing the size of the gate opening increased the local electric field by diminishing the gate-emitter screening effect. However, gate voltages were able to enhance or inhibit the local electric field much more readily with smaller gate radii. Due to the strength of gate-emitter field screening in the triode-type structure, the spacing between emitters had virtually no impact on the local electric field, allowing relatively high emitter densities. These theoretical results, combined with a highly controllable synthesis method, provide valuable information and methodology for those designing and optimizing triode-type devices targeted at specific applications.
Author : Paul Albert Miller
Publisher :
ISBN 13 :
Total Pages : 29 pages
Book Rating : 4.:/5 (316 download)
Download or read book Nanotube Cathodes written by Paul Albert Miller and published by . This book was released on 2006 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes have shown promise for applications in many diverse areas of technology. In this report we describe our efforts to develop high-current cathodes from a variety of nanotubes deposited under a variety of conditions. Our goal was to develop a one-inch-diameter cathode capable of emitting 10 amperes of electron current for one second with an applied potential of 50 kV. This combination of current and pulse duration significantly exceeds previously reported nanotube-cathode performance. This project was planned for two years duration. In the first year, we tested the electron-emission characteristics of nanotube arrays fabricated under a variety of conditions. In the second year, we planned to select the best processing conditions, to fabricate larger cathode samples, and to test them on a high-power relativistic electron beam generator. In the first year, much effort was made to control nanotube arrays in terms of nanotube diameter and average spacing apart. When the project began, we believed that nanotubes approximately 10 nm in diameter would yield sufficient electron emission properties, based on the work of others in the field. Therefore, much of our focus was placed on measured field emission from such nanotubes grown on a variety of metallized surfaces and with varying average spacing between individual nanotubes. We easily reproduced the field emission properties typically measured by others from multi-wall carbon nanotube arrays. Interestingly, we did this without having the helpful vertical alignment to enhance emission; our nanotubes were randomly oriented. The good emission was most likely possible due to the improved crystallinity, and therefore, electrical conductivity, of our nanotubes compared to those in the literature. However, toward the end of the project, we learned that while these 10-nm-diameter CNTs had superior crystalline structure to the work of others studying field emission from multi-wall CNT arrays, these nanotubes still had a thin coating of glassy carbon surrounding them in a sheath-like manner. This glassy carbon, or nano-crystalline graphite, is likely to be a poor conductor due to phonon scattering, and should actually be deleterious for extracting electrons with electric fields. While we did not achieve the field emission reported for single-wall carbon nanotubes that spurred the idea for this project, at the year's very end, we had a breakthrough in materials growth and learned to control the growth of very-small diameter nanotubes ranging from 1.4 to 7 nm. The 1.4-nm nanotubes are single-walled and grow at only 530 C. This is the lowest temperature known to result in single-wall carbon nanotubes, and may be very important for many applications that where certain substrates could not be used due to the high temperatures commonly used for CNT growth. Critically important for field emission, these small diameter nanotubes, consisting of only a few concentric graphene cylindrical walls, do not show the presence of a poorly-conductive sheath material. Therefore, these nanotubes will almost definitely have superior field emission properties to those we already measured, and it is possible that they could provide the necessary field emission to make this project successful. Controlled spacing and lengths of these single-wall nanotubes have yet to be explored, along with correlating their structures to their improved field emission. Unfortunately, we did not discover the methods to grow these highly-crystalline and small diameter CNTs until late in the year. Since we did not achieve the necessary emission properties by mid-year, the project was ''prematurely'' terminated prior to the start of the second year. However, it should be noted that with the late developments, this work has not hit the proverbial ''brick wall''. Clearly the potential still exists to reproduce and even exceed the high emission results reported for randomly-oriented and curly single-wall carbon nanotubes, both in terms of total field emitting currents and perhaps more importantly, in reproducibility.
Author : Alexander Kuznetsov
Publisher :
ISBN 13 :
Total Pages : 190 pages
Book Rating : 4.:/5 (298 download)
Download or read book Physics of Electron Field Emission by Self-assembled Carbon Nanotube Arrays written by Alexander Kuznetsov and published by . This book was released on 2008 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: Extensive study of electrochemical charge injection of CNTs and its applications in electron field emission was performed. It was shown that work function of carbon nanotubes can be tuned in a wide range by means of electrochemical charging. The problem of charge dissipation in air is especially important for negative charging. It was found that larger size and higher valence of injected ions can significantly increase the stability of charging.
Author : Yong Mui Wong
Publisher :
ISBN 13 : 9781109919073
Total Pages : 149 pages
Book Rating : 4.9/5 (19 download)
Download or read book Aligned Carbon Nanotubes Vacuum Field Emission Devices written by Yong Mui Wong and published by . This book was released on 2006 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: A consistent and reproducible CNTs synthesis method comprising plasma pretreatment of the catalysts prior to CNT synthesis was developed to tailor the surface profile of vertically aligned CNTs. The study found that the plasma pretreatment time and the array spacing of the micropatterned CNT emitters play an important role in achieving the desired field emission characteristics of low turn-on field, high current density and emission stability.
Author : 胡嘉德
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (11 download)
Download or read book Carbon Nanotube Intramolecular Junction Fabricated by Oxygen Plasma Treatment for Optoelectronics, Field Emission, and Ballistic Characteristic Optimization written by 胡嘉德 and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Niraj Narasinha Kulkarni
Publisher :
ISBN 13 :
Total Pages : 62 pages
Book Rating : 4.:/5 (59 download)
Download or read book Field emission from vertically aligned carbon nanotube arrays written by Niraj Narasinha Kulkarni and published by . This book was released on 2002 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Nikolay Egorov
Publisher : Springer
ISBN 13 : 3319565613
Total Pages : 578 pages
Book Rating : 4.3/5 (195 download)
Download or read book Field Emission Electronics written by Nikolay Egorov and published by Springer. This book was released on 2017-06-01 with total page 578 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is dedicated to field emission electronics, a promising field at the interface between “classic” vacuum electronics and nanotechnology. In addition to theoretical models, it includes detailed descriptions of experimental and research techniques and production technologies for different types of field emitters based on various construction principles. It particularly focuses on research into and production of field cathodes and electron guns using recently developed nanomaterials and carbon nanotubes. Further, it discusses the applications of field emission cathodes in new technologies such as light sources, flat screens, microwave and X-ray devices.
Author :
Publisher :
ISBN 13 :
Total Pages : 974 pages
Book Rating : 4.F/5 ( download)
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 974 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Stephanie Reich
Publisher : John Wiley & Sons
ISBN 13 : 3527618058
Total Pages : 224 pages
Book Rating : 4.5/5 (276 download)
Download or read book Carbon Nanotubes written by Stephanie Reich and published by John Wiley & Sons. This book was released on 2008-09-26 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes are exceptionally interesting from a fundamental research point of view. Many concepts of one-dimensional physics have been verified experimentally such as electron and phonon confinement or the one-dimensional singularities in the density of states; other 1D signatures are still under debate, such as Luttinger-liquid behavior. Carbon nanotubes are chemically stable, mechanically very strong, and conduct electricity. For this reason, they open up new perspectives for various applications, such as nano-transistors in circuits, field-emission displays, artificial muscles, or added reinforcements in alloys. This text is an introduction to the physical concepts needed for investigating carbon nanotubes and other one-dimensional solid-state systems. Written for a wide scientific readership, each chapter consists of an instructive approach to the topic and sustainable ideas for solutions. The former is generally comprehensible for physicists and chemists, while the latter enable the reader to work towards the state of the art in that area. The book gives for the first time a combined theoretical and experimental description of topics like luminescence of carbon nanotubes, Raman scattering, or transport measurements. The theoretical concepts discussed range from the tight-binding approximation, which can be followed by pencil and paper, to first-principles simulations. We emphasize a comprehensive theoretical and experimental understanding of carbon nanotubes including - general concepts for one-dimensional systems - an introduction to the symmetry of nanotubes - textbook models of nanotubes as narrow cylinders - a combination of ab-initio calculations and experiments - luminescence excitation spectroscopy linked to Raman spectroscopy - an introduction to the 1D-transport properties of nanotubes - effects of bundling on the electronic and vibrational properties and - resonance Raman scattering in nanotubes.
Author : Mohamed Berber
Publisher : BoD – Books on Demand
ISBN 13 : 9535124692
Total Pages : 508 pages
Book Rating : 4.5/5 (351 download)
Download or read book Carbon Nanotubes written by Mohamed Berber and published by BoD – Books on Demand. This book was released on 2016-07-20 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Author : Parveen Saini
Publisher : John Wiley & Sons
ISBN 13 : 1119137101
Total Pages : 684 pages
Book Rating : 4.1/5 (191 download)
Download or read book Fundamentals of Conjugated Polymer Blends, Copolymers and Composites written by Parveen Saini and published by John Wiley & Sons. This book was released on 2015-04-30 with total page 684 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Author : Michael Matthew Micci
Publisher : AIAA
ISBN 13 : 9781600864391
Total Pages : 520 pages
Book Rating : 4.8/5 (643 download)
Download or read book Micropropulsion for Small Spacecraft written by Michael Matthew Micci and published by AIAA. This book was released on 2000 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : M. Meyyappan
Publisher : CRC Press
ISBN 13 : 0203494938
Total Pages : 306 pages
Book Rating : 4.2/5 (34 download)
Download or read book Carbon Nanotubes written by M. Meyyappan and published by CRC Press. This book was released on 2004-07-28 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes, with their extraordinary mechanical and unique electronic properties, have garnered much attention in the past five years. With a broad range of potential applications including nanoelectronics, composites, chemical sensors, biosensors, microscopy, nanoelectromechanical systems, and many more, the scientific community is more moti
Author : M. Endo
Publisher : Elsevier
ISBN 13 : 008054553X
Total Pages : 200 pages
Book Rating : 4.0/5 (85 download)
Download or read book Carbon Nanotubes written by M. Endo and published by Elsevier. This book was released on 2013-10-22 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes have been studied extensively in relation to fullerenes, and together with fullerenes have opened a new science and technology field on nano scale materials. A whole range of issues from the preparation, structure, properties and observation of quantum effects in carbon nanotubes in comparison with 0-D fullerenes are discussed. In addition, complementary reviews on carbon nanoparticles such as carbon nano-capsules, onion-like graphite particles and metal-coated fullerenes are covered. This book aims to cover recent research and development in this area, and so provide a convenient reference tool for all researchers in this field. It is also hoped that this book can serve to stimulate future work on carbon nanotubes.
