No description available.

No description available.

Apart from being a support, the three substrates had their own roles in the growth of CNTs. Bamboo charcoal also acted as a catalyst provider. Au-coated silicon wafer participated in the formation of the silica/CNT composite nanowires. Copper foil itself was a catalyst. The silicate, the Au/Si droplet, and the copper particles were the catalysts for the growth of CNTs in these three substrates, respectively. The formation of the CNTs followed the vapor-liquid-solid (VLS) route which involved the decomposition of ethanol vapor into carbon, carbon dissolution inside the liquid catalyst and precipitation to form CNTs. / CNTs could be grown in a very wide temperature range (700-1400°C), but specific substrate for a particular temperature range was needed. The structures of the CNTs varied with the CVD processing conditions. The forms and the amount of catalytic material entering the interior of the CNTs depended on the characteristics of the catalyst for that process / The products formed on different substrates had their own characteristic features . Hollow or silicate filled CNTs with silicate droplet tips were formed on the surface of bamboo charcoal. Their diameter was in hundreds of nanometers and the length was about several microns. CNT-coated silica core-shell structures were obtained on Au-coated silicon wafer. The graphitic carbon shell was formed in thickness about 145 nm for the sample prepared at 1185°C, but amorphous carbon shell was produced in thickness more than 300 nm for the sample prepared at 1236°e. Lastly, CNTs with bamboo-like structure were synthesized on the copper foil substrate. The CNTs were getting thicker from 70 nm to 170 nm when temperature was increased from 700°C to 1000°C. The yield increased with temperature and annealing time if the sample was annealed for less than 30 min. / We report the growth of carbon nanotubes (CNTs) on different types of substrates with or without catalytic materials by using different approaches. The roles of the substrates and the catalysts in the formation of the CNTs are studied . We also characterized and identified the structural properties of the CNTs products. In this work, three types of substrates had been used, namely biomorphic bamboo charcoal , Au-coated silicon wafer, and copper foil. The CNTs were grown on different substrates by chemical vapor deposition (CVD) method at temperature range between 700°C and 1400°C. Ethanol vapor was used as the carbon source, while tetraethyl orthosilicate (TEOS) vapor was also applied to the process for bamboo charcoal. / Zhu, Jiangtao = 碳納米管在不同類型基底上的生長 / 朱江濤. / Adviser: D. H. L. Ng. / Source: Dissertation Abstracts International, Volume: 72-11, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Zhu, Jiangtao = Tan na mi guan zai bu tong lei xing ji di shang de sheng chang / Zhu Jiangtao.

No description available.

Neste trabalho foram imobilizados nanotubos de carbono de parede simples sobre um eletrodo de ouro policristalino gerando uma camada de nanotubos alinhados verticalmente na superfície do eletrodo. Para isto, foi utilizado um fragmento de DNA (ssDNA tiol-terminado (5-HS-TGG-GGT-TTA-TGG-AAA-TTGGAA-3)) que foi posicionado ao redor do nanotubo de carbono com o procedimento seguinte: 1,0 mg SWCNT funcionalizado foi misturado com 1,0 mL de uma solução de ssDNA de 1,0 &micro;mol L-1, e o ssDNA foi preparado em 0,1 molL-1 de PBS contendo cloreto de sódio a 10% (v / v). Em seguida, a mistura foi sonicada usando uma sonda de ultra-som por 45 min e depois centrifugada a 10000 rpm por 30 min. Finalmente, um eletrodo de Au previamente limpo foi imerso na solução de sobrenadante e monocamadas auto-organizadas (SAM), que consistem de ssDNA/SWCNT foram formadas durante 24 h numa sala refrigerada a 4 &deg;C. As características morfológicas dos eletrodos foram determinadas por microscopia de força atômica, observando-se o alinhamento vertical, que alterou a rugosidade do eletrodo de 1,95 nm para 47,5 nm, com a altura média dos SWCNTs de 260,3 nm, com um desvio padrão relativo de 19,9%. O comportamento eletroquímico do eletrodo de ouro modificado com o hibrido ssDNA/SWCNT foi caracterizado utilizando voltametria cíclica em meio de Na2SO4 0,1 mol L-1 contendo K3Fe(CN)6 5,0 mmol L-1, com velocidade de varredura de potencial de 50 mVs-1. Observou-se que a reversibilidade do par redox Fe(CN)63-/Fe(CN)64- é maior para o eletrodo modificado com ssDNA/SWCNT (&Delta;Epico= 80 mV) quando comparado ao eletrodo de Au (&Delta;Epico = 115 mV). A modificação proporcionou uma resposta mais eletrocatalítica com um deslocamento de 43 mV para valores menos positivos do potencial de oxidação do Fe(CN)63-. A oxidação no eletrodo de Au/ssDNA/SWCNTs ocorre em +417 mV e no eletrodo de Au em +460 mV. Este aumento de reversibilidade foi quantificado por espectroscopia eletroquímica de impedância faradaica, onde se encontrou os valores de constantes de velocidade de 7.56 &times; 10-5 cm s-1 para o eletrodo modificado e apenas 3,36 &times; 10-5 cm s-1 para o de ouro puro. O efeito da modificação da superfície Au com o nanohíbrido ssDNA / SWCNT na oxidação do bisfenol-A (BPA) foi avaliado em Na2SO4 0,1 mol L-1, pH 6,0, contendo 100 &micro;mol L-1 de BPA por voltametria cíclica a 50 mV s-1. Observou-se um processo de oxidação com um pico voltamétrico anódico num valor de potencial de 510 mV. Este processo de oxidação está relacionado com a eletro-oxidação de BPA para íons fenoxeno. O processo ocorreu em um potencial menos positivo do que o valor observado para o eletrodo de Au não modificado, ou seja 720 mV. Além disso, o processo oxidativo referente à superfície modificada mostrou-se mais catalítico, proporcionando um aumento do pico de oxidação de 163%. <br /> Para a metodologia analítica, procurou-se se maximizar o sinal analítico da técnica de voltametria de pulso diferencial, DPV, assim a resposta para o eletrodo de Au/ssDNA/SWCNT foi estudada em relação ao pH, salto de potenciais e a amplitude de pulso. Os valores ótimos encontrados foram 6,0, 2 mV e 50 mV, respectivamente. Nestas condições o eletrodo de Au/ssDNA/SWCNT foi aplicado para a determinação de BPA em uma solução de Na2SO4 0,1 mol L-1, pH 6,0. A resposta analítica tem um comportamento linear na faixa entre 1,0 - 4,5 &micro;mol L-1, de acordo com a seguinte equação: I (&micro;A) = 0.019 (&micro;A) + 5.82 (&micro;A/ &micro;molL-1) [BPA], com um coeficiente de correlação de 0,996 (n = 10) e um limite de detecção (LOD) de 11,0 nmol L-1 (2,51 &micro;g L-1) determinado de acordo com as recomendações da IUPAC. O valor obtido é menor que aqueles disponíveis na literatura. / In the present work, single-walled carbon nanotubes (SWCNT) were immobilized over top a polycrystalline gold electrode. This immobilization assembled a layer of vertically aligned nanotubes on the electrode surface. For this purpose, it was used a DNA probe (ssDNA thiolated (HS-5-TGG-TTA-TGG-GGT-AAA-TTGGAA-3)) that has been used to wrap the carbon nanotube as the following procedure: 1.0 mg of functionalized SWCNT was mixed with 1.0 mL of 1.0 &micro;mol L-1 of a ssDNA solution prepared in 0.1 mol L-1 of PBS containing 10% (v/v) of sodium chloride. Next, the mixture was sonicated using an ultrasonic horn probe and then centrifuged at 10000 rpm; each process took 45 min. Finally, a previously cleaned Au electrode was immersed in the supernatant solution. Self-assembled monolayers (SAMs) consisting of ssDNA/SWCNT were formed after 24 h in a refrigerated room at 4 &deg;C. The morphological characteristics of the electrodes were determined using atomic force microscopy. It was observed that the vertical alignment increased the electrode surface roughness of 1.95 nm to 47.5 nm. The average height of the SWCNT was calculated at 260.3 nm, with a relative standard deviation of 19.9%. The electrochemical behavior of gold electrode modified with the ssDNA/SWCNT hybrid was characterized using cyclic voltammetry (CV) in 0.1 mol L-1 of Na2SO4 containing 5.0 mmol L-1 of [K3Fe(CN)6], with a scan rate of 50 mVs-1. It was observed that the reversibility of the redox couple Fe(CN)63-/Fe(CN)64- decreased using the electrode modified with ssDNA/SWCNT (&Delta;Epeak = 80 mV), when compared with the Au electrode (&Delta;Epeak = 115 mV). The modification provided an electrocatalytic response with a shift of 43 mV to less positive values on the Fe(CN)63- oxidation potential value. The oxidation on the Au/ssDNA/SWCNT electrode occurs at +417 mV and the Au electrode at +460 mV. This improvement on the reversibility was quantified using the electrochemical impedance spectroscopy, in which it was observed an apparent constant rate at 7.56 x 10-5 cm s-1 for the modified electrode and 3.36 x 10-5 cm s-1 for pure gold. The effect of the modification of the Au surface with the nanohybrid ssDNA/SWCNT on the bisphenol A (BPA) oxidation was evaluated 0.1 mol L-1 of Na2SO4 (pH 6.0) containing 100 &micro;mol L-1 of BPA. The system was evaluated using CV at 50 mV s-1. The CV experiments showed an oxidation process with an anodic peak potential at 510 mV. This oxidation process is attributed to the electro-oxidation of the BPA forming the fenoxene ions. The process occurred at a less positive potential value when compared with the unmodified Au electrode, i.e. 720 mV. Moreover, surface modified with the nanohybrid presented more catalytic providing an increase of 163% on the oxidation current peak. For the analytical methodology, the analytical signal was maximized. For this, the differential pulse voltammetry (DPV) parameters such as: pulse amplitude and step potential and pH were optimized. The optimum values found were pH at 6.0, pulse amplitude at 50 mV and step potential at 2 mV. In these conditions, the Au/ssDNA/SWCNT electrode was applied for the BPA determination in 0.1 mol L-1 of Na2SO4. The analytical response showed a linear relationship in a range from 1.0 to 4.5 &micro;mol L-1, in accordance with the following equation: I (&micro;A) = 0.019 (&micro;A) + 5.82 (&micro;A / &micro;mol L-1) [BPA ], with a correlation coefficient of 0.996 (n = 10). The limit of detection (LOD) of 11.0 nmol L-1 (2.51 &micro;g L-1) was determined in accordance with the IUPAC recommendations. The obtained value is smaller than those available in the literature.

Low-dimensional systems are an important and intensely studied area of condensed matter physics. When a material is forced to adopt a low-dimensional structure, its behaviour is often dramatically different to that of the bulk phase. It is vital to predict the structures of low-dimensional systems in order to reliably predict their properties. To this end, the ab initio random structure searching (AIRSS) method, which has previously been used to identify the structures of bulk materials, has been extended to deal with the case of nanowires encapsulated inside carbon nanotubes. Such systems are a rapidly developing area of research with important nanotechnological applications, including information storage, energy storage and chemical sensing. The extended AIRSS method for encapsulated nanowires (ENWs) was implemented and used to identify the structures formed by germanium telluride, silver chloride, and molybdenum diselenide ENWs. In each of these cases, a number of novel nanowire structures were identified, and a phase diagram predicting the ground state nanowire structure as a function of the radius of the encapsulating nanotube was calculated. In the case of germanium telluride, which is a technologically important phase-change material, the potential use of GeTe ENWs as switchable nanoscale memory devices was investigated. The vibrational properties of silver chloride ENWs were also considered, and a novel scheme was developed to predict the Raman spectra of systems which can be decomposed into multiple weakly interacting subsystems. This scheme was used to obtain a close approximation to the Raman spectra of AgCl ENWs at a fraction of the computational cost that would otherwise be necessary. The encapsulation of AgCl was shown to produce substantial shifts in the Raman spectra of nanotubes, providing an important link with experiment. A method was developed to predict the stress-strain response of an ENW based on a polygonal representation of its surface, and was used to investigate the elastic response of molybdenum diselenide ENWs. This was used to predict stress-radius phase diagrams for MoSe_2 ENWs, and hence to investigate stress-induced phase change within such systems. The X-ray diffraction of ENWs was also considered. A program was written to simulate X-ray diffraction in low-dimensional systems, and was used to predict the diffraction patterns of some of the encapsulated GeTe nanowire structures predicted by AIRSS. By modelling the interactions within a bundle of nanotubes, diffraction patterns for bundles of ENWs were obtained.

Zhang, Yu. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 55-60). / Abstract also in Chinese. / Abstract --- p.i / Acknowledgement --- p.iii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Aim of Research --- p.2 / Chapter 1.3 --- Thesis Organization --- p.3 / Chapter 2 --- Literature Review --- p.4 / Chapter 2.1 --- Carbon Nanotubes in MEMS Devices --- p.4 / Chapter 2.1.1 --- CNT Integration and CNT sensors --- p.4 / Chapter 2.1.2 --- Prior Work in CMNS --- p.6 / Chapter 2.2 --- Overview of Motion Sensors --- p.7 / Chapter 2.2.1 --- Technology Overview --- p.7 / Chapter 2.2.2 --- Categories and Working Principles --- p.9 / Chapter 2.2.3 --- Application --- p.13 / Chapter 2.3 --- Thermal Convective Motion Sensors --- p.14 / Chapter 2.3.1 --- Micro Thermal Flow Sensors --- p.15 / Chapter 2.3.2 --- Research on Thermal Convective Motion Sensors --- p.17 / Chapter 2.3.3 --- Working Principle and Performances --- p.20 / Chapter 3 --- Design and Setup --- p.25 / Chapter 3.1 --- Methodology --- p.25 / Chapter 3.1.1 --- Research Method --- p.25 / Chapter 3.1.2 --- Critical Questions --- p.26 / Chapter 3.2 --- Sensor Chip Design and Fabrication --- p.27 / Chapter 3.2.1 --- Sensor Chip Mask Design --- p.27 / Chapter 3.2.2 --- Fabrication of Sensor Chip --- p.29 / Chapter 3.3 --- Sensor Prototyping --- p.30 / Chapter 3.3.1 --- CNT Deposition --- p.30 / Chapter 3.3.2 --- Sensor Building --- p.32 / Chapter 3.4 --- Setup of Experiment --- p.34 / Chapter 3.4.1 --- Source and Measure --- p.34 / Chapter 3.4.2 --- Acceleration Production --- p.35 / Chapter 4 --- Experiments and Results --- p.39 / Chapter 4.1 --- Hypotheses Verification --- p.39 / Chapter 4.1.1 --- Thermal Detection Using CNT --- p.39 / Chapter 4.1.2 --- Local Heating & Sensing --- p.40 / Chapter 4.2 --- Tilting Test --- p.42 / Chapter 4.2.1 --- Test Result --- p.42 / Chapter 4.2.2 --- Result Discussions --- p.43 / Chapter 4.3 --- Vibration Test --- p.45 / Chapter 4.3.1 --- Test Result --- p.45 / Chapter 4.3.2 --- Result Discussions --- p.52 / Chapter 5 --- Conclusion --- p.53 / Bibliography --- p.55

by Jia, Jiangying. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves ). / Abstracts in English and Chinese. / ABSTRACT --- p.i / 摘要 --- p.ii / ACKNOWLEDGEMENTS --- p.iii / TABLE OF CONTENTS --- p.iv / LIST OF FIGURES --- p.vii / LIST OF TABLES --- p.ix / Chapter CHAPTER ONE --- INTRODUCTION --- p.1 / Chapter 1.1 --- Background --- p.2 / Chapter 1.1.1 --- Vibration damping --- p.2 / Chapter 1.1.2 --- Carbon nanotubes --- p.4 / Chapter 1.1.3 --- Fabrication of carbon nanotube composites --- p.8 / Chapter 1.1.4 --- Literature review on carbon nanotube composites --- p.10 / Chapter 1.2 --- Research Objective --- p.13 / Chapter 1.3 --- Thesis Organization --- p.14 / Chapter CHAPTER TWO --- FABRICATION OF CNT AND CNT/EPOXY COMPOSITES --- p.15 / Chapter 2.1 --- Fabrication of CNT --- p.16 / Chapter 2.1.1 --- Fabrication requirements --- p.16 / Chapter 2.1.2 --- Substrate and catalyst preparation --- p.17 / Chapter 2.1.3 --- Aligned CNT film grown by PECVD method --- p.18 / Chapter 2.2 --- Fabrication of CNT/Epoxy Composite --- p.25 / Chapter 2.3 --- Measurement of CNT/Epoxy Composites --- p.31 / Chapter 2.4 --- Chapter Summary --- p.34 / Chapter CHAPTER THREE --- MODELLING OF THE CNT COMPOSITES --- p.35 / Chapter 3.1 --- Geometrical Configuration of Composites --- p.36 / Chapter 3.2 --- Critical Shear Stresses and “Stick-Slip´ح Behavior --- p.38 / Chapter 3.3 --- Nonlinear Viscoelastic Composite Model --- p.40 / Chapter 3.3.1 --- Maxwell model --- p.40 / Chapter 3.3.2 --- Three-parameter standard solid model --- p.45 / Chapter 3.4 --- Stress and Strain Evaluation --- p.50 / Chapter 3.5 --- Effective Moduli and Loss Factor of Composite --- p.56 / Chapter 3.6 --- Chapter Summary --- p.60 / Chapter CHAPTER FOUR --- PARAMETRIC STUDY OF THE CNT COMPOSITES --- p.61 / Chapter 4.1 --- Carbon Nanotube Dimensions --- p.62 / Chapter 4.2 --- Parametric Study --- p.65 / Chapter 4.3 --- Summary --- p.69 / Chapter CHAPTER FIVE --- CONCLUSIONS AND FUTURE WORK --- p.70 / Chapter 5.1 --- Conclusions --- p.70 / Chapter 5.2 --- Future Work --- p.72 / BIBLIOGRAPHY --- p.73 / APPENDIX --- p.78 / Chapter A. --- Epoxy Resin Datasheet --- p.78 / Chapter B. --- Matlab Program for Young´ةs Modulus Calculation --- p.80 / Chapter C. --- Matlab Program for Loss Factor Calculation --- p.82

Xiao, Peng. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 76-78). / Abstracts in English and Chinese. / ABSTRACT --- p.i / 摘要 --- p.iii / ACKNOWLEDGEMENTS --- p.iv / TABLE OF CONTENTS --- p.vi / LIST OF FIGURES --- p.viii / LIST OF TABLES --- p.xi / Chapter CHAPTER ONE --- INTRODUCTION --- p.1 / Chapter 1.1 --- The Thermal Characteristic of the CNT Heater --- p.1 / Chapter 1.2 --- CNT-Based Micro Bubble Generation in a Static Droplet of Water --- p.2 / Chapter 1.3 --- CNT-Based Micro Bubble Transportation in a Micro Channel --- p.4 / Chapter 1.4 --- CNT-Based Micro Bubble Stimulation by Pulsed Current --- p.4 / Chapter CHAPTER TWO --- THE THERMAL CHARACTERISTICS OF CARBON NANOTUBES --- p.6 / Chapter 2.1 --- Temperature Coefficient of Resistance (TCR) of Our Typical CNT Heater --- p.7 / Chapter 2.2 --- The Humidity Coefficient of the Resistance (HCR) for Our Typical CNT Heater --- p.13 / Chapter 2.3 --- The Conclusion of the CNT Heater's Thermal and Humidity Characteristics --- p.18 / Chapter CHAPTER THREE --- MICRO BUBBLE GENERATION WITH MICRO WATT POWER USING CARBON NANOTUBE HEATING ELEMENTS --- p.19 / Chapter 3.1 --- Micro Electrode Fabrication --- p.19 / Chapter 3.1.1 --- Methods for Metal Electrode Fabrication --- p.20 / Chapter 3.1.2 --- Advantages and Disadvantages of Two Micro Fabrication Methods --- p.22 / Chapter 3.1.3 --- The Fabrication of Micro Electrodes for Our CNT Heater --- p.24 / Chapter 3.1.4 --- The Mask Design for Metal Electrode Fabrication --- p.26 / Chapter 3.2 --- The Micro Bubble Generation Experimental Procedure --- p.28 / Chapter 3.2.1 --- Initial Analysis of the Experimental Device --- p.28 / Chapter 3.3 --- Theoretical Analysis of Bubble Generation Temperature on the CNT Heater --- p.31 / Chapter 3.3 --- The Analysis of the Micro Bubble Generation Experimental Results --- p.35 / Chapter 3.4 --- The Conclusion of Bubble Generation in a Static Droplet of Water --- p.44 / Chapter CHAPTER FOUR --- CARBON NANOTUBE-BASED MICRO BUBBLE GENERATION IN A MICRO CHANNEL WITH DYNAMIC FLUID --- p.45 / Chapter 4.1 --- Micro Channel Fabrication --- p.46 / Chapter 4.1.1 --- Rapid Prototyping --- p.46 / Chapter 4.1.2 --- PDMS Moulding --- p.47 / Chapter 4.1.3 --- Irreversible Sealing --- p.49 / Chapter 4.1.4 --- Mask Design --- p.50 / Chapter 4.2 --- Experimental Setup --- p.51 / Chapter 4.3 --- Experimental Procedure --- p.53 / Chapter 4.4 --- Experimental Results --- p.55 / Chapter 4.5 --- Conclusion for Bubble Generation in the Micro Channel with Dynamic Fluid --- p.59 / Chapter CHAPTER FIVE --- CNT-BASED MICRO BUBBLE STIMULATION BY PULSED CURRENT --- p.60 / Chapter 5.1 --- Attempt to Control the Micro Bubble Diameter --- p.61 / Chapter 5.2 --- The Pulsed Current for Micro Bubble Departure in the Micro Channel --- p.63 / Chapter 5.2.1 --- Manual Pulsed Current Stimulation for Micro Bubble Departure in the Micro Channel --- p.64 / Chapter 5.2.2 --- The Pulsed Current Circuit for Micro Bubble Departure in the Micro Channel --- p.67 / Chapter CHAPTER SIX --- FUTURE WORK AND SUMMARY --- p.70 / Chapter 6.1 --- Future Work for Micro Bubble Generation Projects --- p.70 / Chapter 6.1.1 --- The CNT-Based Micro Bubble Generation with Various Values of Input Current --- p.70 / Chapter 6.1.2 --- The CNT Heater in the Zig-Zag Micro Channel --- p.71 / Chapter 6.1.3 --- Summary --- p.72 / APPENDIX A --- p.73 / Fabrication Process --- p.73 / Chapter I. --- Micro Electrode Fabrication --- p.73 / Chapter II. --- Micro Channel Fabrication --- p.75 / BIBLIOGRAPHY --- p.76

Carbon nanotubes and graphene have been a trending research topic in the past decade. These graphitic compounds exhibit numerous advantageous properties (electronic, mechanical, thermal, optical, etc) which industry and researchers alike are excited to take advantage of. Beyond the challenges of yield and controlled growth, there are a number of standing questions which govern some of the more fundamental characteristics of these materials: What role do lattice defects play in the adsorption of gas molecules on the surface of carbon nanotubes? How are the electronic states of the carbon nanotubes influenced by these adsorbed molecules? And how can we develop models to predict useful applications of this knowledge? In order to address these questions, this study combines Raman spectroscopy and electronic measurements carried out in highly controlled environments of carbon nanotube transistors. Assessing these data in conjunction shows that the defect density of a carbon nanotube channel has no correlation with observed threshold voltage shifts, or change in Schottky barrier, due to the presence of ambient oxygen. With these insights in mind, a dynamic adsorption-desorption model is proposed which addresses the oxygen sensitivity of carbon nanotube transistors. Instrumentation and computational developments which facilitated these measurements are also disclosed.