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Author: Wing-ching Yiu (James)
Publisher:
ISBN:
Category : Nanostructured materials
Languages : en
Pages : 106
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Author: Wing-ching Yiu (James)
Publisher:
ISBN:
Category : Nanostructured materials
Languages : en
Pages : 106
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Book Description
Author: Wing-Ching James Yiu
Publisher:
ISBN: 9781361102794
Category :
Languages : en
Pages :
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This dissertation, "Synthesis of One-dimensional Tungsten Oxide Nano-structures by Thermal Evaporation" by Wing-ching, James, Yiu, 姚穎貞, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled SYNTHESIS OF ONE-DIMENSIONAL TUNGSTEN OXIDE NANO-STRUCTURES BY THERMAL EVAPORATION Submitted by Yiu Wing Ching James for the degree of Master of Philosophy at The University of Hong Kong in October 2005 Synthesis of one-dimensional nanomaterials (1D NM) is the essence of nanotechnology development. Thermal Evaporation by a tube furnace is commonly used to produce a wide range of 1D NM for studies on physical properties and corresponding applications. Presently, the studies on producing Tungsten Oxide (WO, X=1-3) NM is rare due to the high synthesis temperature required. For decades, the eutectic alloying technique has been used by materials engineers to obtain desirable alloys at a low temperature. Therefore, Thermal Evaporation may work with the eutectic alloying technique to synthesis WO NMs at a low temperature. It is known that by using potassium iodide (KI) as catalysts, tungsten (W) and potassium (K) form a eutectic alloy upon thermal evaporation; the alloys then act as seeds for 1D NMs growth. However, many important synthesis parameters of this technique are still unclear. It is not clear how air pressure, catalysts distribution methods, and humidity would affect the morphologies and quality of products. It is also not clear whether other halide salt can as well work as catalysts for WO NM growth. The lack of such information makes product quality, including diameter, length, and phase purity difficult. In order to improve the control growth of 1D WO NMs produced by thermal evaporation, a number of experiments were carried out as part of the study. The significance of air pressure on products quality was investigated by comparing specimens generated in atmospheric and in super-low pressures. The effect of catalysts distribution methods on products morphologies was shown by using a solution method to distribute catalysts, and by directly placing the catalyst powder on sample substrate. In addition, sodium chloride (NaCl) was used to test if other halide salt, apart from KI, work as the catalysts for WO NMs growth. The influence of humidity was examined by introducing a large amount of moisture during the thermal evaporation process. The final part of this project involved the fabrication method of Anodized Aluminum Membrane (AAM), which consists of many nanochannels that can be the template for WO 1D NMs growth. In these experiments, it is found that low pressures are critical for the monodispersity of nanoproducts. When KI catalysts are distributed by solution method, grown products have a finer diameter and the synthesis temperature is lower than those directly using KI powder as a catalyst. It is found that NaCl could not act as a catalyst for low temperature growth, therefore KI is essential for WO NMs synthesis. When moisture was introduced during thermal evaporation, large amount of nanoribbons was produced. Finally, high quality AAM could be fabricated by applying the optimum anodization voltage, which favors self-ordering of nanopores. An empirical equation was established to find the optimum anodization voltage for a particular electrolyte. DOI: 10.5353/th_b3204777 Subjects: Tungsten oxides - Synthesis Nanostructured materials - Synthesis Nanostructures Nanotechnology
Author: 洪昆權
Publisher:
ISBN: 9781374667396
Category :
Languages : en
Pages :
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This dissertation, "Synthesis of One-dimensional Tungsten Oxide Nanostructures" by 洪昆權, Kunquan, Hong, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled SYNTHESIS OF ONE-DIMENSIONAL TUNGSTEN OXIDE NANOSTRUCTURES Submitted by Hong Kunquan for the degree of Doctor of Philosophy at The University of Hong Kong in January 2008 Tungsten oxide has been used for various optical devices, sensors and so forth for its outstanding electrochromic, optochromic, gaschromic and electronic properties. One-dimensional (1D) tungsten oxide nanostructures are expected to improve the performance of those devices as well as to open up new applications. o Generally, high temperature (1200-2000 C) and special equipments are required in the synthesis of these tungsten oxide nanostructures, which can be obstacles for a wider application. In this thesis, some new methods have been developed to synthesize 1D tungsten oxide nanostructures. The relevant growth mechanisms were also investigated. Firstly, a simple method was devised to grow tungsten oxide nanostructures by thermal evaporation at low temperature and yet without using catalyst. By o heating tungsten powder at 650 C, and tungsten plate or tungsten powder covered o silicon substrates at 400 C, tungsten oxide (W O ) nanowires with diameter of 18 49 10-50 nm were obtained with high quantity. It was further shown that the presence of a pre-oxide layer on tungsten substrate is essential for high yield W O 18 49 nanowire growth. Under optimal conditions, the diameter of the nanowires can be decreased down to 4-7 nm. Second, when potassium iodide (KI) was introduced in the synthesis, various types of nanostructures or micro-structures, such as tungsten oxide and potassium tungstates (K W O ) micro-walls were obtained, depending 2 3 10 on the temperature of substrate, the gas flow and the pressure in the reactor. It was o found that tungsten oxide nanowires can be synthesized at 400 C in the presence of KI, and the addition of source materials will enhance the growth. Finally, by thermally evaporating tungsten trioxide powder source, tungsten oxide W O nanowires were also synthesized with high yield and on a large 18 49 scale. Depending on the temperature of the source (in the range of 900-1000 C), the diameter of the tungsten oxide nanowires varies from 10 nm to 100 nm, following an exponential relation. Nanowires with controllable diameter are therefore obtainable by this method. Under other conditions, nanowires, nanoplates, nanocrystals and comb-like nanostructures were obtained on silicon substrate. The growth mechanisms of these nanostructures, especially the dependence of nanowire size on source temperature, were further investigated. It is found that the diameter of nanowires increases with growth time but a maximum diameter seems to exist as determined by the source temperature. A theoretical model was used to analyze the growth mechanism for the diameter control where zero-dimensional (0D) and two-dimensional (2D) nucleation contribute to the growth of length and the diameter of the nanowire respectively. DOI: 10.5353/th_b3955855 Subjects: Tungsten oxides - Synthesis Nanostructures
Author: Kunquan Hong
Publisher:
ISBN:
Category : Nanostructures
Languages : en
Pages : 232
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Author: Tianyou Zhai
Publisher: John Wiley & Sons
ISBN: 1118310365
Category : Technology & Engineering
Languages : en
Pages : 857
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Book Description
Reviews the latest research breakthroughs and applications Since the discovery of carbon nanotubes in 1991, one-dimensional nanostructures have been at the forefront of nanotechnology research, promising to provide the building blocks for a new generation of nanoscale electronic and optoelectronic devices. With contributions from 68 leading international experts, this book reviews both the underlying principles as well as the latest discoveries and applications in the field, presenting the state of the technology. Readers will find expert coverage of all major classes of one-dimensional nanostructures, including carbon nanotubes, semiconductor nanowires, organic molecule nanostructures, polymer nanofibers, peptide nanostructures, and supramolecular nanostructures. Moreover, the book offers unique insights into the future of one-dimensional nanostructures, with expert forecasts of new research breakthroughs and applications. One-Dimensional Nanostructures collects and analyzes a wealth of key research findings and applications, with detailed coverage of: Synthesis Properties Energy applications Photonics and optoelectronics applications Sensing, plasmonics, electronics, and biosciences applications Practical case studies demonstrate how the latest applications work. Tables throughout the book summarize key information, and diagrams enable readers to grasp complex concepts and designs. References at the end of each chapter serve as a gateway to the literature in the field. With its clear explanations of the underlying principles of one-dimensional nanostructures, this book is ideal for students, researchers, and academics in chemistry, physics, materials science, and engineering. Moreover, One-Dimensional Nanostructures will help readers advance their own investigations in order to develop the next generation of applications.
Author: Ram K. Gupta
Publisher: CRC Press
ISBN: 1000844072
Category : Technology & Engineering
Languages : en
Pages : 429
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Book Description
This comprehensive resource covers the fundamentals of synthesis, characterizations, recent progress, and applications of nanowires for many emerging applications. Early chapters address their unique properties and morphology that enable their electronic, optical, and mechanical properties to be tuned. Later chapters address future perspectives and future challenges in areas where nanowires could provide possible solutions. All chapters are written by global experts, making this a suitable textbook for students and an up-to-date handbook for researchers and industry professionals working in physics, chemistry, materials, energy, biomedical, and nanotechnology. Covers materials, chemistry, and technologies for nanowires. Covers the state-of-the-art progress and challenges in nanowires. Provides fundamentals of the electrochemical behavior of various electrochemical devices and sensors. Offers insights on tuning the properties of nanowires for many emerging applications. Provides a new direction and understanding to scientists, researchers, and students.
Author:
Publisher: Academic Press
ISBN: 0123743966
Category : Science
Languages : en
Pages : 2785
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Book Description
From the Introduction: Nanotechnology and its underpinning sciences are progressing with unprecedented rapidity. With technical advances in a variety of nanoscale fabrication and manipulation technologies, the whole topical area is maturing into a vibrant field that is generating new scientific research and a burgeoning range of commercial applications, with an annual market already at the trillion dollar threshold. The means of fabricating and controlling matter on the nanoscale afford striking and unprecedented opportunities to exploit a variety of exotic phenomena such as quantum, nanophotonic and nanoelectromechanical effects. Moreover, researchers are elucidating new perspectives on the electronic and optical properties of matter because of the way that nanoscale materials bridge the disparate theories describing molecules and bulk matter. Surface phenomena also gain a greatly increased significance; even the well-known link between chemical reactivity and surface-to-volume ratio becomes a major determinant of physical properties, when it operates over nanoscale dimensions. Against this background, this comprehensive work is designed to address the need for a dynamic, authoritative and readily accessible source of information, capturing the full breadth of the subject. Its six volumes, covering a broad spectrum of disciplines including material sciences, chemistry, physics and life sciences, have been written and edited by an outstanding team of international experts. Addressing an extensive, cross-disciplinary audience, each chapter aims to cover key developments in a scholarly, readable and critical style, providing an indispensible first point of entry to the literature for scientists and technologists from interdisciplinary fields. The work focuses on the major classes of nanomaterials in terms of their synthesis, structure and applications, reviewing nanomaterials and their respective technologies in well-structured and comprehensive articles with extensive cross-references. It has been a constant surprise and delight to have found, amongst the rapidly escalating number who work in nanoscience and technology, so many highly esteemed authors willing to contribute. Sharing our anticipation of a major addition to the literature, they have also captured the excitement of the field itself in each carefully crafted chapter. Along with our painstaking and meticulous volume editors, full credit for the success of this enterprise must go to these individuals, together with our thanks for (largely) adhering to the given deadlines. Lastly, we record our sincere thanks and appreciation for the skills and professionalism of the numerous Elsevier staff who have been involved in this project, notably Fiona Geraghty, Megan Palmer and Greg Harris, and especially Donna De Weerd-Wilson who has steered it through from its inception. We have greatly enjoyed working with them all, as we have with each other.
Author: Alexander Charles Santulli
Publisher:
ISBN:
Category : Chemistry
Languages : en
Pages :
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Author: Rong Hu
Publisher:
ISBN: 9781374678644
Category :
Languages : en
Pages :
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Author: Arvind Kumar
Publisher: John Wiley & Sons
ISBN: 3527350276
Category : Technology & Engineering
Languages : en
Pages : 373
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Book Description
In-depth discussion on the physics, chemistry, and engineering beneath the construction of 1D semiconducting hybrid materials 1D Semiconducting Hybrid Nanostructures: Synthesis and Applications in Gas Sensing and Optoelectronics provides breakthrough research developments and trends in a variety of 1D hybrid nanostructures for chemi-resistive gas sensors and optoelectronics applications, including recent investigations and developments regarding the innovative designing approaches, fabrications, and methods used to characterize these hybrid nanostructures. The text also includes the surface and interface properties of 1D hybrid semiconducting nanostructured materials, as well as their optimization for applications in gas sensing and optoelectronics. This book further addresses the different issues of sensitivity, selectivity, and operating temperature of gas sensors based on hybrid 1D nanostructures. Moreover, it covers the novel and additional functional optoelectronic properties that originate at the interface of 1D semiconducting nanostructures combined with other low dimensional materials. Some of the specific sample topics covered in this book include: Gas sensing and optoelectronic applications of one-dimensional semiconducting hybrid nanostructures, plus synthesis and gas sensing application of 1D semiconducting hybrid nanostructures Room temperature gas sensing properties of metal oxide nanowire/graphene hybrid structures and highly sensitive room temperature gas sensors based on organic-inorganic nanofibers Synthesis and applications of 1D hybrid tin oxide nanostructures and recent advances in semiconducting nanowires-based hybrid structures for solar application Types of semiconducting hybrid nanostructures for optoelectronic devices and hybrid 1D semiconducting ZnO/GaN nanostructures Thanks to its comprehensive coverage of the subject from highly qualified authors who have significant experience in the field, 1D Semiconducting Hybrid Nanostructures is a must-have reference for senior undergraduate and graduate students, professionals, researchers, in the field of semiconductor physics, materials science, surface science, and chemical engineering.
