Dissertations / Theses: 'Synthesis of carbon nanotubes (CNTs)'

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Bera, Debasis. "ARC-DISCHARGE IN SOLUTION: A NOVEL SYNTHESIS METHOD FOR CARBON NANOTUBES AND IN SITU DECORATION OF CARBON NANOTUBES WITH NANOPAR." Doctoral diss., University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2609.

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Nanotechnology has reached the status of the 21st century's leading science and technology based on fundamental and applied research during the last two decades. An important feature of nanotechnology is to bridge the crucial dimensional gap between the atomic and molecular fundamental sciences and microstructural scale of engineering. Accordingly, it is very important to have an in-depth understanding of the synthesis of nanomaterials for the use of state-of-the-art high technological devices with enhanced properties. Recently, the 'bottom-up' approach for the fabrication of nanomaterials has received a great deal of attention for its simplicity and cost effectiveness. Tailoring the various parameters during synthesis of selected nanoparticles can be used to fabricate technologically important components. During the last decade, carbon nanotubes (CNTs) have been envisioned for a host of different new applications. Although carbon nanotubes can be synthesized using a variety of techniques, large-scale synthesis is still a great challenge to the researchers. Three methods are commonly used for commercial and bulk productions of carbon nanotubes: arc-discharge, chemical vapor deposition and laser ablation. However, low-cost, large-scale production of high-quality carbon nanotubes is yet to be reported. One of the objectives of the present research is to develop a simplified synthesis method for the production of large-scale, low-cost carbon nanotubes with functionality. Herein, a unique, simple, inexpensive and one-step synthesis route of CNTs and CNTs decorated with nanoparticles is reported. The method is simple arc-discharge in solution (ADS). For this new method, a full-fledged optoelectronically controlled instrumen is reported here to achieve high efficiency and continuous bulk production of CNTs. In this system, a constant gap between the two electrodes is maintained using a photosensor which allows a continuous synthesis of the carbon nanostructures. The system operates in a feedback loop consisting of an electrode-gap detector and an analogue electronic unit, as controller. This computerized feed system was also used in single process step to produce in situ-decorated CNTs with a variety of industrially important nanoparticles. To name a few, we have successfully synthesized CNTs decorated with 3-4 nm ceria, silica and palladium nanoparticles for many industrially relevant applications. This process can be extended to synthesize decorated CNTs with other oxide and metallic nanoparticles. Sixty experimental runs were carried out for parametric analysis varying process parameters including voltage, current and precursors. The amount of yield with time, rate of erosion of the anode, and rate of deposition of carbonaceous materials on the cathode electrode were investigated. Normalized kinetic parameters were evaluated for different amperes from the sets of runs. The production rate of pristine CNT at 75 A is as high as 5.89 ± 0.28 g.min-1. In this study, major emphasis was given on the characterizations of CNTs with and without nanoparticles using various techniques for surface and bulk analysis of the nanostructures. The nanostructures were characterized using transmission electron microscopy, high resolution transmission electron microscopy, scanning transmission electron microscopy, energy dispersive spectroscopy and scanning electron microscopy, x-ray photo electron spectroscopy, x-ray diffraction studies, and surface area analysis. Electron microscopy investigations show that the CNTs, collected from the water and solutions, are highly pure except the presence of some amorphous carbon. Thermogravimetric analysis and chemical oxidation data of CNTs show the good agreement with electron microscopy analysis. The surface area analysis depicts very high surface area. For pristine multi-walled carbon nanotubes, the BET surface area is approximately 80 m2.g-1. X-ray diffraction studies on carbon nanotubes shows that the products are clean. Nano-sized palladium decorated carbon nanotubes are supposed to be very efficient for hydrogen storage. The synthesis for in-situ decoration of palladium nanoparticles on carbon nanotubes using the arc discharge in solution process has been extensively carried out for possible hydrogen storage applications and electronic device fabrication. Palladium nanoparticles were found to form during the reduction of palladium tetra-chloro-square planar complex. The formation of such a complex was investigated using ultraviolet-visible spectroscopic method. Pd-nanoparticles were simultaneously decorated on carbon nanotubes during the rolling of graphene sheets in the arc-discharge process. Zero-loss energy filtered transmission electron microscopy and scanning transmission electron microscopy confirm the presence of 3 nm palladium nanoparticles. The deconvoluted X-ray photoelectron spectroscopy envelope shows the presence of palladium. Surface area measurements using BET method show a surface area of 28 m2.g-1. The discrepancy with pristine CNTs can be explained considering the density of palladium (12023 kg.m-3). Energy dispersive spectroscopy suggests no functionalization of chlorine to the sidewall of carbon nanotubes. The presence of dislodged graphene sheets with wavy morphology as observed with high-resolution transmission electron microscopy supports the formation of CNTs through the 'scroll mechanism'. Ph.D. Department of Mechanical, Materials and Aerospace Engineering; Engineering and Computer Science Materials Science and Engineering

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Zhang, Qiuhong. "Carbon Nanotubes on Carbon Fibers: Synthesis, Structures and Properties." Dayton, Ohio : University of Dayton, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1272515887.

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Thesis (Ph.D. in Materials Engineering) -- University of Dayton. Title from PDF t.p. (viewed 06/23/10). Advisor: Liming Dai. Includes bibliographical references (p. 136-162). Available online via the OhioLINK ETD Center.

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Wasel, Wahed Rezk. "HEAT TRANSFER AND CHEMICAL PROCESSES IN CHEMICAL VAPOR DEPOSITION REACTOR FOR SYNTHESIS OF CARBON NANOTUBES." UKnowledge, 2006. http://uknowledge.uky.edu/gradschool_diss/386.

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A small-scale model of a CVD reactor was built. Axial and radial of major species concentrations and temperature profiles were obtained with a micro gas chromatograph and a fine thermocouple. Those temperature and species concentrations revealed detailed thermal and chemical structures of the CVD reactor. The concentrations of argon plus hydrogen, methane, and C2Hx (C2H2 + C2H4 + C2H6) resulting from xylene decomposition were measured along the CVD at different temperatures. Ferrocene was added to xylene to investigate the effect of a catalyst on composition profiles. The results with ferrocene indicated an increase in CH4 and C2Hx concentrations. At 1000 C and above, the increase of C2Hx concentration is higher than that for CH4. The effect of ferrocene was very minor on the concentration of the gases. Finally composition and temperature profiles were measured and plotted for the radial direction at X=75 cm and T=1200 C. The overall rate constant for the gas-phase reaction was calculated based on the measured species concentration data using the Benson and Shaw reaction mechanism. Our study showed that the Benson and Shaw mechanism could be used in the temperature range lower than 800 C. Also the effect of hydrogen in the syntheses of CNTs, in the CVD reactor using xylene and ferrocene, was studied. Both single-step and two-step methods were applied. In the single-step method, the ferrocene was dissolved in the xylene. In the two step-method the catalyst preparation step was performed first; ferrocene powder was placed in the preheater for a certain period of time and carried by a mixture of argon and hydrogen at fixed concentration to get catalyst nanoparticles deposited on the reactor wall. Xylene then was injected to the reactor. To study the effect of hydrogen, the synthesized materials were observed by SEM and TEM. The results showed that the presence of hydrogen is essential for CNTs to be synthesized by the CVD method, and also the concentration of hydrogen in the reactor has a great effect on the quality of CNTs. The yield of CNTs in the two-step method was slightly higher than that in the one-step method.

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Almkhelfe, Haider H. "Scalable carbon nanotube growth and design of efficient catalysts for Fischer-Tropsch synthesis." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/38213.

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Doctor of Philosophy Department of Chemical Engineering Placidus B. Amama The continued depletion of fossil fuels and concomitant increase in greenhouse gases have encouraged worldwide research on alternative processes to produce clean fuel. Fischer-Tropsch synthesis (FTS) is a heterogeneous catalytic reaction that converts syngas (CO and H₂) to liquid hydrocarbons. FTS is a well-established route for producing clean liquid fuels. However, the broad product distribution and limited catalytic activity are restricting the development of FTS. The strong interactions between the active metal catalyst (Fe or Co) and support (Al₂O₃, SiO₂ and TiO₂) during post-synthesis treatments of the catalyst (such as calcination at ~500°C and reduction ~550°C) lead to formation of inactive and unreducible inert material like Fe₂SiO₄, CoAl₂O₄, Co₂SiO₄. The activity of FTS catalyst is negatively impacted by the presence of these inactive compounds. In our study, we demonstrate the use of a modified photo-Fenton process for the preparation of carbon nanotube (CNT)-supported Co and Fe catalysts that are characterized by small and well-dispersed catalyst particles on CNTs that require no further treatments. The process is facile, highly scalable, and involves the use of green catalyst precursors and an oxidant. The reaction kinetic results show high CO conversion (85%), selectivity for liquid hydrocarbons and stability. Further, a gaseous product mixture from FTS (C1-C4) was utilized as an efficient feedstock for the growth of high-quality, well-aligned single-wall carbon nanotube (SWCNT) carpets of millimeter-scale heights on Fe and (sub) millimeter-scale heights on Co catalysts via chemical vapor deposition (CVD). Although SWCNT carpets were grown over a wide temperature range (between 650 and 850°C), growth conducted at optimal temperatures for Co (850°C) and Fe (750°C) yielded predominantly SWCNTs that are straight, clean, and with sidewalls that are largely free of amorphous carbon. Also, low-temperature CVD growth of CNT carpets from Fe and Fe–Cu catalysts using a gaseous product mixture from FTS as a superior carbon feedstock is demonstrated. The efficiency of the growth process is evidenced by the highly dense, vertically aligned CNT structures from both Fe and Fe–Cu catalysts even at temperatures as low as 400°C–a record low growth temperature for CNT carpets obtained via conventional thermal CVD. The use of FTS-GP facilitates low-temperature growth of CNT carpets on traditional (alumina film) and nontraditional substrates (aluminum foil) and has the potential of enhancing CNT quality, catalyst lifetime, and scalability. We demonstrate growth of SWCNT carpets with diameter distributions that are smaller than SWCNTs in conventional carpets using a CVD process that utilizes the product gaseous mixture from Fischer-Tropsch synthesis (FTS-GP). The high-resolution transmission electron microscopic (HR-TEM) and Raman spectroscopic results reveal that the use of a high melting point metal as a catalyst promoter in combination with either Co (1.5 nm ± 0.7) at 850ºC or Fe (1.9 nm ± 0.8) at 750ºC yields smaller-diameter SWCNT arrays with narrow diameter distributions. Scalable synthesis of carbon nanotubes (CNTs), carbon nanofibers (CNFs), and onion like carbon (OLC) in a batch reactor using supercritical fluids as a reaction media is demonstrated. The process utilizes toluene, ethanol, or butanol as a carbon precursor in combination with ferrocene that serves as a catalyst precursor and a secondary carbon source. The use of supercritical fluids for growth does not only provide a route for selective growth of a variety of carbon nanomaterials, but also provides a unique one-step approach that is free of aggressive acid treatment for synthesis of CNT-supported metallic nanoparticle composites for catalysis and energy storage applications.

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Turano, Stephan Parker. "Carbon Nanotubes chemical vapor deposition synthesis and application in electrochemical double layer supercapacitors /." Thesis, Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-02242005-094827/unrestricted/turano%5Fstephan%5Fp%5F200505%5Fmast.pdf.

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Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2005. Ready, Jud, Committee Co-Chair ; Carter, Brent, Committee Co-Chair ; Snyder, Bob, Committee Member ; Wang, Zhong Lin, Committee Member. Includes bibliographical references.

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Paul, Aniruddha. "Synthesis of Graphene - Carbon Nanotube Hybrid Structures." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-290574.

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Graphene and Carbon nanotubes (CNTs) have been researched for more than a decade due to their extraordinary properties and advantages towards applications like electronics, structural re-enforcements, thermal management and energy storage. Graphene-CNT hybrid structures have been predicted to further enhance the exceptional properties and overcome some of the shortcomings of the individual materials. Advantages of a structure consisting of vertically aligned carbon nanotubes (VACNTs) covalently bonded with graphene layers have been predicted to be especially favourable for applications like TIM, supercapacitors and battery electrodes. This project investigates two growth mechanisms for obtaining Graphene-VACNT structures using scalable processes. Shortcomings of previously done research on similar structures like graphene transfer and bad CNT alignment is solved. A novel growth mechanism is also investigated to set the foundation for research into a new approach to grow Graphene-CNT hybrid structures in the future. Chemical Vapor Deposition (CVD) was the method used to grow the graphene and CNT structures. The characterization was done using optical microscopy, Scanning electron microscopy (SEM) and Raman spectroscopy. Grafen- och kolnanorör (CNT) har forskats i mer än ett decennium på grund av deras extraordinära egenskaper och fördelar gentemot applikationer som elektronik, strukturförstärkning, termisk hantering och energilagring. Grafen-CNT hybridstrukturer har förutspåtts ytterligare förbättra de exceptionella egenskaperna och övervinna några av bristerna i de enskilda materialen. Fördelar med en struktur som består av vertikalt inriktade kolnanorör (VACNT) som är kovalent bundna med grafenskikt har förutspåtts vara särskilt fördelaktiga för applikationer som TIM, superkondensatorer och batterielektroder. Detta projekt undersöker två tillväxtmekanismer för att erhålla Graphene-VACNT-strukturer med hjälp av skalbara processer. Brister i tidigare utförd forskning om liknande strukturer som grafenöverföring och dålig CNT-anpassning är lösta. En ny tillväxtmekanism undersöks också för att lägga grunden för forskning om ett nytt tillvägagångssätt för att växa Graphene- CNT hybridstrukturer i framtiden. Chemical Vapor Deposition (CVD) var metoden som användes för att odla grafen- och CNT-strukturerna. Karakteriseringen gjordes med optisk mikroskopi, Scanning electron microscopy (SEM) och Raman-spektroskopi.

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De, Jager Nicolaas Jacobus. "The investigation and development of gas sensors with carbon nanomaterials." Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/17872.

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Thesis (MScEng)--Stellenbosch University, 2011. ENGLISH ABSTRACT: In this research the possible utilization of carbon nanomaterials in gas sensing applications are investigated. These materials include the 2-dimensional honeycomb-lattice carbon structure called graphene, and the 1-dimensional structures referred to as carbon nanotubes (CNTs). The extraordinary properties and unique morphology of these nanomaterials, make them excellent candidates for sensory applications. This research thus entails the investigation and development of gas sensors with these carbon nanomaterials. This includes the synthesis of CNTs via a chemical vapour deposition (CVD) technique and the fabrication of resistive thin film sensors with the various materials. The functionalization of carbon nanomaterials is also explored, which delivers promising results for sensing gases at room temperature, especially acetylene (C2H2). Furthermore, a unique method is developed to fabricate ultra thin aluminium microstructures. These metallic electrodes are found to be ideal for nanomaterial integration. An experiment is performed to manufacture an integrated sensor with MWCNTs and following the results, a refinement of the procedure and the investigation of FET-based devices are recommended. The results obtained during this work, indicate that engineered carbon nanostructures, such as CNTs and graphene, can potentially be applied in future sensing technologies. AFRIKAANSE OPSOMMING: Hierdie navorsing ondersoek die moontlike toepassing van koolstof nano-materiale as gas-sensor tegnologie. Hierdie materiale sluit die 2-dimensionele koolstof struktuur, grafeen, asook die sogenaamde 1-dimensionele koolstof nano-buise in. Die buitengewone eienskappe en unieke morfologie van hierdie nano-materiale, maak hul uitstekende kandidate vir sensor toepassings. Hierdie navorsing ondersoek dus die ontwikkeling van gas-sensors met koolstof nano-materiale, insluitend die sintese van koolstof nano-buise deur middel van ’n chemiese damp-neerslag proses, asook die fabrikasie van resistiewe dun film sensors. Die funksionalisering van koolstof nano-materiale is ook ondersoek en belowende resultate is opgelewer met betrekking tot die deteksie van gasse by kamertemperatuur, veral vir asetileen (C2H2) gas. Verder is ’n unieke metode ontwikkel om ultra dun aluminium mikrostrukture te vervaardig en hierdie metaal elektrodes word as ideaal beskou vir die integrasie van nano-materiale. ’n Eksperiment is uitgevoer om ’n geïntegreerde sensor te vervaardig met multi-wand koolstof nano-buise, waarvan die resultate aandui dat die proses verfyn moet word en dat die moontlike toepassing van veld-effek-transistor toestelle ondersoek moet word. Die resultate wat opgelewer is gedurende hierdie navorsing dui daarop dat ontwikkelde nanostrukture, soos koolstof nano-buise en grafeen, as toekomstige sensor tegnologie geïmplementeer kan word.

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Halonen, N. (Niina). "Synthesis and applications of macroscopic well-aligned multi-walled carbon nanotube films." Doctoral thesis, Oulun yliopisto, 2013. http://urn.fi/urn:isbn:9789526202105.

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Abstract The main objectives of this thesis are to synthesize macroscopic well-aligned multi-walled carbon nanotube films and, based on their electrical conductivity, porosity and structural uniformity, highlight potential applications for further development. In this thesis, catalytic chemical vapour deposition from ferrocene-xylene precursors is optimized to grow high quality films of long, aligned multi-walled carbon nanotubes on lithographically patterned templates in high (~800ºC) temperatures. The impacts of reaction time, temperature and precursor concentration on MWCNT film quality (film thickness, purity, density and nanotube diameter distribution) are studied. Because of the excellent control of growth selectivity and film thickness inherent to the method, several interesting applications, including solar cell and capacitor electrodes, contact brushes, coolers, particulate filters and catalyst membranes, have been developed for nanotube films in collaboration between Finnish and international research groups over the past few years. In this thesis, advanced capacitor electrodes with improved charge storage and efficient particulate filters are discussed in closer detail. As the high temperatures used for growing high quality carbon nanotubes often cause complications in cases where nanotubes need to be directly integrated with other materials, experiments were also conducted with the aim of making the growth temperature as low as possible. After testing several catalyst and precursor combinations, cobalt nanoparticles deposited on silica surfaces were found to form carbon nanotubes from vaporized cyclopentene oxide precursor already at 470°C. The results show that catalytic chemical vapour deposition is a feasible and versatile method that can be combined with photolithography to produce multi-walled carbon nanotube films with desired footprint area and thickness on various substrates. The demonstrated new applications and technical solutions are expected to contribute to further development leading to competitive practical devices based on carbon nanotubes Tiivistelmä Tämän väitöstyön päätavoitteina ovat makroskooppisten, yhdensuuntaisista moniseinämäisistä hiilinanoputkista koostuvien kalvojen valmistaminen ja sovellutusten esittäminen perustuen kalvojen sähkönjohtavuuteen, huokoisuuten ja rakenteelliseen yhdenmukaisuuteen. Katalyyttis-kemiallinen höyryfaasikasvatusmenetelmä on optimoitu korkealaatuisten, yhdensuuntaisista, pitkistä moniseinämäisistä hiilinanoputkista koostuvien kalvojen tuottamiseen korkeissa lämpötiloissa (~800ºC) fotolitografialla kuvioiduille kasvualustoille käyttäen ferroseeni/ksyleeni-lähtöainetta. Reaktioajan, lämpötilan ja lähtöainepitoisuuden vaikutusta nanoputkikalvon laatuun on tutkittu tarkastelemalla kalvon paksuutta, puhtautta, tiheyttä ja nanoputkien läpimittajakaumaa. Erinomaisen kasvuselektiivisyyden ja kalvon paksuuden kontrolloimisen ansiosta nanoputkikalvoja voidaan räätälöidä useisiin mielenkiintoisiin sovellutuksiin (esim. aurinkokennot ja kondensaattorin elektrodit, hiiliharjat, jäähdyttimet, partikkelisuodattimet ja katalyyttikalvot), joita olemme kehittäneet viime vuosina yhdessä suomalaisten ja kansainvälisten tutkimusryhmien kanssa. Tässä väitöstyössä on tarkasteltu lähemmin uudentyyppisiä kondensaattorielektrodeja, joilla on parantunut sähkövarauksen varastointikyky, sekä tehokkaita partikkelisuodattimia. Hiilinanoputkien kasvattaminen korkeissa lämpötiloissa aiheuttaa usein ongelmia integroitaessa nanoputkia toisiin materiaaleihin. Tästä johtuen tutkimuksessa pyrittiin saamaan nanoputkien kasvatuslämpötila mahdollisimman alhaiseksi testaamalla useita lähtöaine-katalyytti-kombinaatioita, joista koboltti-nanopartikkelit piidioksidin päällä ja syklopenteenioksidi lähtöaineena muodostivat hiilinanoputkia jo 470°C:ssa. Tulosten perusteella katalyyttis-kemiallinen höyryfaasikasvatusmenetelmä yhdistettynä fotolitografiaan on hyvin monipuolinen tapa tuottaa moniseinämäisiä hiilinanoputkia halutulla kuviolla ja kalvonpaksuudella erilaisille substraateille. Tässä väitöstyössä demonstroitujen uusien sovellutusten ja teknisten ratkaisujen odotetaan johtavan uusiin, hiilinanoputkiin perustuviin kilpailukykyisiin käytännön laitteisiin

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Jayasinghe, Chaminda. "Synthesis and Characterization of Carbon Nanotube, Threads, Yarns, and Sheets." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1312292744.

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Pitkänen, O. (Olli). "On-device synthesis of customized carbon nanotube structures." Doctoral thesis, Oulun yliopisto, 2019. http://urn.fi/urn:isbn:9789526223179.

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Abstract Carbon nanotubes (CNTs) are known for their excellent mechanical, electrical and thermal properties, that have fostered a vast number of applications during the last two decades, from composites, electrodes and nanoelectonics components, to sensors and biological scaffolds. Direct integration of CNTs into devices is not straightforward, as high growth temperatures (above 600 °C) challenge the chemical and thermal stability of substrates, catalysts and other nearby materials or components. However, by decreasing growth temperature and/or working out protocols that take into account the thermal stability of the materials involved, it is possible to create several new types of architectures and devices with functionalities not shown before. In this work, we show that, with selection of the appropriate substrate, diffusion barrier and catalyst materials, direct growth of functional CNT films and their micropatterns may be achieved, not only on Si chips, but also on other atypical surfaces, using chemical vapor deposition. This thesis explores low-temperature CNT synthesis over bi- and trimetallic catalysts, and investigates the effect of diffusion barrier layers on the electrical properties of substrate-to-CNT contacts. On one hand, the lowest achieved CNT synthesis temperature (400 °C) is compatible with most silicon technologies, thus enabling direct integration of CNTs with materials and devices with low thermal budgets. On the other hand, the results of diffusion barrier studies helped us in designing and demonstrating on-chip micropatterned CNT structures for super and pseudocapacitor electrodes. In addition, we also show a method for maskless growth of CNT micropatterns using laser-treated steel and superalloy surfaces, whose surface diffusion properties change as a result of barrier-type metal oxide formation. Furthermore, we present CNT growth on carbon materials and demonstrate entirely carbon-based hierarchical composites for electromagnetic interference shielding applications, exhibiting outstanding absorption-based shielding performance. The results presented in this thesis are expected to contribute to a further expansion of CNT-based technologies, in particular with potential for future advances in high-frequency devices (arrays, amplifiers and shielding materials), energy materials (electrodes and scaffolds), as well as in nanoelectromechanical systems (sensors and actuators) Tiivistelmä Hiilinanoputket tunnetaan niiden erinomaisista mekaanisista, sähköisistä ja termisistä ominaisuuksista, joita on hyödynnetty lukuisissa sovelluksissa viimeisen kahden vuosikymmenen aikana alkaen komposiiteista, elektrodeista, nanoelektroniikkakomponenteista ja sensoreista aina biologisiin tukirakenteisiin. Nanoputkien synteesi suoraan laitteessa ei ole suoraviivaista, sillä korkeat, yli 600 °C synteesilämpötilat asettavat haasteita substraatin, katalyytin sekä muiden lähellä olevien materiaalien ja komponenttien kemialliselle ja termiselle vakaudelle. Alentamalla synteesilämpötilaa ja/tai kehittämällä termisen vakauden huomioivia menetelmiä on mahdollista luoda uudenlaisia arkkitehtuureja ja sovelluksia ennennäkemättömillä ominaisuuksilla. Tässä työssä osoitetaan, että sopivan substraatin, diffuusiosuojan ja katalyyttimateriaalin valitsemalla funktionaalisten hiilinanoputkien synteesi on mahdollista piin lisäksi myös muille, epätavallisille pinnoille käyttäen kemiallista kaasufaasipinnoitusta. Väitöstyössä käsitellään hiilinanoputkien matalan lämpötilan synteesiä hyödyntäen kaksi- ja kolmimetallisia katalyyttejä sekä tutkitaan diffuusiosuojakerroksen sähköistä vaikutusta substraatin ja hiilinanoputkien väliseen kontaktiin. Alin saavutettu synteesilämpötila (400 °C) on yhteensopiva useimpien piiteknologioiden kanssa, mikä mahdollistaa nanoputkien suoran integroinnin matalaa lämpötilaa edellyttäville materiaaleille. Työssä tutkitun diffuusiosuojakerroksen kehitys mahdollisti myös piisirun päälle toteutettujen hiilinanoputkipohjaisten super- ja pseudokondensaattorielektrodien demonstroinnin. Lisäksi työssä esitetään menetelmä, jossa laserkäsittelemällä teräs- ja supermetalliseospinta, jonka avulla mikrokuvioitu hiilinanoputkien kasvu ilman litografiaprosessia on mahdollista. Viimeisenä työssä esitetään hiilinanoputkien synteesi suoraan toiselle hiilimateriaalille ja demonstroidaan täysin hiilipohjainen, hierarkkinen komposiittimateriaali erinomaisella absorptioon perustuvalla suojauskyvyllä sähkömagneettisiin häiriösuojaussovelluksiin. Väitöstyössä esitettyjen tulosten odotetaan osaltaan edistävän hiilinanoputkipohjaisten teknologioiden kehitystä erityisesti korkean taajuuden laitteissa, energiamateriaaleissa sekä nanosähkömekaanisissa järjestelmissä

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Löffler, Markus. "Nanomanipulation and In-situ Transport Measurements on Carbon Nanotubes." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-33242.

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With the advent of microelectronics and micromechanical systems, the benefits of miniaturized technology became evident. With the discovery of carbon nanotubes by Iijima in 1991, a material has been found that offers superior porperties such as high tensile strength, excellent electrical and heat conductivity while being lightweight, flexible and tunable by the specific atomic arrangement in its structure. The first part of this thesis deals with a new synthesis approach, which combines the known routes of chemical vapour deposition and laser ablation. The results concerning diameter and yield fit well within an established model for the nucleation and growth of carbon nanotubes and extend it by considering a larger parameter space. Furthermore, conventional laser ablation has been used to synthesize C-13 augmented carbon nanotubes, whose diameters depend among the usual synthesis parameters also on the C-13 content, an influence which is in line with the changed thermal conductivities of isotope mixtures. Manipulation of carbon nanotubes inside a transmission electron microscope forms the second part of this thesis. With the help of an in-situ nanomanipulator, several experiments involving the mechanical and electrical properties of carbon nanotubes have been performed. Two-probe resistances of individual nanotubes have been measured and the observation of individual shell failures allowed for the determination of current limits per carbon shell. With the help of electrical current, a nanotube was modified in its electrical characteristics by reshaping its structure. By application of DC-currents or square current pulses, the filling of iron- or cementite-filled multi-wall carbon nanotubes has been found to move in a polarity-defined direction guided by the nanotube walls. Depending on the current, nanotube shape, and composition of the filling different regimes of material transport have been identified, including the reworking of the inner nanotube shells. The application of a high driving current leads to a complete reworking of the host nanotube and the current-induced growth of carbonaceous nanostructures of changed morphology. Utilizing the obtained results, a transport mechanism involving momentum transfer from the electron wind to the filling atoms and a solid filling core during transport is developed and discussed. Finally, measurements of mechanical properties using electrically induced resonant or non-resonant vibrations inside the transmission electron microscope have been observed and important mechanical parameters have been determined with the help of a modified Euler-Bernoulli-beam approach Mit dem Aufkommen von Mikroelektronik und mikromechanischen Systemen wurden die Vorteile miniaturisierter Geräte augenscheinlich. Mit der Entdeckung von Kohlenstoff-Nanoröhren durch Iijima 1991 wurde ein Material gefunden, welches überlegene Eigenschaften wie hohe Festigkeit, exzellente elektrische und Wärmeleitfähigkeit zeigt, während es zeitgleich leicht und flexibel ist. Diese Eigentschaften können durch eine Änderung der spezifischen atomaren Anordnung in der Nanoröhrenhülle beeinflusst werden. Der erste Teil dieser Dissertationsschrift behandelt einen neuartigen Syntheseansatz, welche die bekannten Syntheserouten der chemischen Gasphasenabscheidung und Laserablation kombiniert. Die Ergebnisse bezüglich des Durchmessers und der Ausbeute lassen sich gut mit einem etablierten Modell der Nukleation und des Wachstums von Kohlenstoff-Nanoröhren beschreiben - sie erweitern es, indem sie einen größeren Parameterraum berücksichtigen. Des Weiteren wurde konventionelle Laserablation benutzt, um C-13 angereicherte Kohlenstoff-Nanoröhren herzustellen, deren Durchmesser nicht nur von den üblichen Parametern, sondern auch vom C-13 Anteil abhängt. Diese Abhängigkeit geht mit der veränderten thermischen Leitfähigkeit von Isotopenmischungen einher. Die Manipulation von Kohlenstoff-Nanoröhren in einem Transmission-Elektronenmikroskop formt den zweiten Teil der Dissertationschrift. Mit Hilfe eines in-situ Manipulators wurden vielfältige Experimente durchgeführt, um die mechanischen und elektrischen Eigenschaften der Kohlenstoff-Nanoröhren zu bestimmen. Zweipunktmessungen des Widerstands einzelner Nanoröhren und die Beobachtung des Versagens einzelner Kohlenstoffschichten erlaubte die Bestimmung der Stromtragfähigkeit einzelner Hüllen. Mit Hilfe eines elektrischen Stromes konnte eine Nanoröhre durch die veränderung der Struktur in ihren elektrischen Eigenschaften verändert werden. Unter Verwendung dauerhaften oder gepulsten Gleichstroms konnte die Eisen- oder Zementit-Füllung der Kohlenstoff-Nanoröhren in eine polaritätsabhängige Richtung bewegt werden. Die Füllung wurde dabei durch die Wände der Nanoröhre geführt. Abhängig von Strom, Form der Nanoröhre und Zusammensetzung der Füllung ließen sich verschiedene Bereiche des Materialtransports identifizieren, u.a. das Umarbeiten einiger innerer Kohlenstoffschichten. Ein hoher Strom hingegen bewirkt eine Umarbeitung der kompletten Nanoröhre und strominduziertes Wachstum von Kohlenstoff-Nanostrukturen mit veränderter Morphologie. Mit Hilfe der gewonnenen Resultate wurde ein Transportmodell entwickelt, welches den Impulstransfer von Elektronen an Füllungsatome sowie einen festen Füllungskern während des Transports diskutiert. Messungen der mechanischen Eigenschaften, welche mit Hilfe von resonanter oder nicht-resonanter elektrischer Anregung von Schwingungen im Transmissions-Elektronenmikroskop durchgeführt wurden bilden den Abschluss der Arbeit. Durch die Beobachtungen konnten mit einem modifizierten Euler-Bernoulli-Balkenmodell wichtige mechanische Eigenschaften bestimmt werden

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Olszewski, Amy L. "Synthesis, Biological Functionalization, and Integration ofCarbon Nanotubes for Bio-Sensing Textiles." Youngstown State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1369854838.

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13

García, Enrique J. "Characterization of composites with aligned carbon nanotubes (CNTs) as reinforcement." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35578.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006. This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. Includes bibliographical references (p. 185-201). Carbon nanotubes' (CNTs) superlative combination of electrical, thermal, and especially mechanical properties make them ideal candidates for composite reinforcement. Nanocomposites and hybrid composite architectures employing traditional advanced composites and CNTs offer significant potential mechanical and multifunctional performance benefits. CNT/polymer composites and two different hybrid architectures are experimentally investigated in this work. A novel process for rapidly growing dense, long, high-quality aligned CNT forests is employed. The first architecture is comprised of aligned fibers with CNTs grown radially on their surface. For the second architecture, dense forests of vertically aligned CNTs are placed between the plies of a laminate, in the through-thickness direction. Fundamental issues related to realizing hybrid composite architectures are investigated experimentally: wetting of the CNTs by commercially available polymers for the different architectures, effective reinforcement of the polymer matrices due to the addition of CNTs, and retention of mechanical (stiffness and strength) properties of the fibers after the CNT growth process. (cont.) Wetting of CNT forests by several commercial polymers (including a highly-viscous epoxy) is demonstrated at rates conducive to creating a fully-dispersed CNT/matrix region for the two hybrid architectures previously described. Direct measurements of the mechanical properties of nanocomposites are reported for the first time in the literature. Increases in the Young's modulus of the polymer as high as 220% with just 2% volume fraction of aligned CNTs are observed. Equivalent reinforcement had been obtained previously by other authors with 5% volume fraction of randomly oriented CNTs. Single-fiber tension tests indicate no mechanical degradation (stiffness and strength) for alumina fibers undergoing the CNT growth process. Preliminary results on the fabrication of the two hybrid architectures are also presented. All the experimental results presented in this work indicate that hybrid CNT/composite architectures are feasible and future work focuses on mechanical and multifunctional property characterization of these and other hybrid architectures, and scaling to a continuous CNT growth process. by Enrique J. García. S.M.

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Singh, Charanjeet. "Synthesis of carbon nanotubes." Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/272043.

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Yu, Zhixin. "Synthesis of Carbon Nanofibers and Carbon Nanotubes." Doctoral thesis, Norwegian University of Science and Technology, Department of Chemical Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-508.

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Carbon nanofibers (CNFs) and carbon nanotubes (CNTs) have attracted intense research efforts with the expectation that these materials may have many unique properties and potential applications. The most promising way for large-scale synthesis of CNFs and CNTs is chemical vapor deposition (CVD). CNFs were synthesized on a series of hydrotalcite (HT) derived 77 wt.% Ni-Fe/Al2O3 catalysts in order to achieve the optimization of productivity and quality. It was found that only the Fe catalyst was active in CO disproportionation and only the Ni catalyst was active in ethylene decomposition, whereas all catalysts were active in ethylene decomposition when the reactants were a mixture of C2H4/CO. More control over the structure and diameter of the CNFs has been realized with the HT catalysts. At the same time, a high yield can be obtained. The synthesis process has been further studied as a function of various process parameters. It turned out that high hydrogen concentration, space velocity, and reaction temperature would enhance the production of CNFs. However, a slightly lower quality was associated with the higher productivity. The optimum CNF yield of 128 gCNF/gcat could be reached within 8 h on the HT catalyst with a Ni/Fe ratio of 6:1. Therefore, HT derived catalysts present a new promising route to large-scale controlled synthesis of CNFs. CNTs has been synthesized from CO disproportionation on Ni-Fe/Al2O3 supported catalysts with metal loadings of 20 and 40 wt.%. A high space velocity resulted in a high production rate but a short lifetime and a low carbon capacity. Increasing the metal loading to 40 wt.% significantly increased the reaction rate and productivity, and produced similarly uniform CNTs. Furthermore, H2 was found to be necessary for a high productivity, and the H2 partial pressure could be changed to adjust the orientation angle of the graphite sheets. The effects of catalyst particle size and catalyst support on the CNT growth rate during CO disproportionation were studied over SiO2 and Al2O3 supported Fe catalysts with varying particle sizes. It was found that there was an optimum particle size at around 13-15 nm for the maximum growth rate, and the growth rate was influenced both by the particle size and the support but the particle size was the dominating factor. The trends have been demonstrated at two different synthesis temperatures of 600 and 650°C. The effect of gas precursors on the yield and structure of carbon growth has been systematically investigated over powder Fe and Fe/Al2O3 catalysts. CO/H2, CO, CH4, and C2H6/H2 were the gas precursors studied. The carbon yield was higher on powder Fe from CO, but the yield was higher on Fe/Al2O3 from hydrocarbons. Completely different or similar carbon nanostructures were synthesized, depending on the gas precursors. It was suggested that the reactivity of gas precursors and the structures of carbon deposits are determined by the size and crystallographic faces of the catalyst particles, which are dictated by the interactions among metal particles, support, and the reactants. Controlled synthesis of CNT, platelet nanofiber, fishbone-tubular nanofiber, and onion-like carbon with high selectivity and yield was realized. A mechanism was proposed to illustrate the growth of different carbon nanostructures.

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Höcker, Christian. "On the dynamics within a gas phase process for continuous carbon nanotube synthesis." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/276111.

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Extrapolating the properties of individual carbon nanotubes (CNTs) into macro-scale CNT materials using a continuous and cost effective process offers enormous potential for a variety of applications. The floating catalyst chemical vapour deposition (FCCVD) method discussed in this dissertation bridges the gap between generating nano- and macro-scale CNT material and has already been adopted by industry for exploitation. A deep understanding of the phenomena that occur within the FCCVD reactor and how to control the formation of the catalyst nanoparticles is, therefore, essential to producing a desired CNT product and successfully scaling up the FCCVD process. This dissertation connects information on the decomposition of reactants, axial catalyst nanoparticle dynamics and the morphology of the resultant CNTs and demonstrates how these factors are strongly related to the temperature and chemical availability of reactants within the reactor. For the first time, in-situ measurements of catalyst particle size distributions paired with reactant decomposition profiles and detailed axial SEM studies of formed CNT materials revealed specific temperature domains that have important implications for scaling up the FCCVD process. A novel observation was that the evaporation and re-condensation of catalyst nanoparticles results in the formation, disappearance and reformation of the nanoparticles along the reactor axis. The combined influences of pyrolytic carbon species and catalytic nanoparticles are shown to influence CNT aerogel formation. This work also examines the source of carbon in the formed CNTs and the location of aerogel formation. Axial measurements using isotopically-labelled methane (C13H4) demonstrate that carbon within all CNTs is primarily derived from CH4 rather than some of the early-forming CNTs being predominantly supplied with carbon from decomposed catalytic precursor components. Quantification of CNT production along the axis of the reactor dispels the notion that injection parameters influence CNT formation and shows that bulk CNT formation occurs near the reactor exit regardless of the carbon source (CH4, toluene or ethanol). By supplying carbon to different reactor locations, it was discovered that CNT aerogel formation will occur even when carbon is delivered near the exit of the reactor provided the carbon source reaches a temperature sufficient to induce pyrolysis (>1000°C). Furthermore, experimental studies that identify a new role of sulphur (S) in the CNT formation process are discussed in this work. Analogous to effects observed in other aerosol systems containing S, in the FCCVD reactor, S lowers the nucleation barrier of the catalyst nanoparticles and enhances not only CNT growth but catalyst particle formation itself. The new concept of critical catalyst mass concentration for CNT aerogel formation was identified by implementing the novel approach of completely decoupling catalyst particle formation from CNT aerogel production. Rather than aerogel formation being dependent on a critical particle number concentration and ideal sized catalyst nanoparticles at the entrance of the reaction furnace, it was identified that the important metric is instead a minimum critical catalyst mass concentration. Application of the principle using other catalyst precursors such as cobaltocene, with continuous CNT aerogel formation from cobalt based catalyst nanoparticles being reported for the first time, and iron-based nanoparticles from a spark generator, provides proof of the new principle’s robustness and ubiquity. In addition to the experimental studies above, theoretical studies have been carried out to understand the agglomeration occurring in a CNT aerosol. The agglomeration eventually leads to a gas phase synthesized CNT aerogel at the end of the reactor, which can be collected and spun continuously. The results of this work are not only scientifically interesting, they also provide a strong foundation for further research aimed at optimizing and controlling large-scale CNT reactors by modifying downstream dynamics.

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Andrews, Robert. "Carbon nanotubes : synthesis and functionalization." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/2395.

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This thesis focuses on two of the major challenges of carbon nanotube (CNT) research: understanding the growth mechanism of nanotubes by chemical vapour deposition (CVD) and the positioning of nanotubes on surfaces. The mechanism of growth of single–walled nanotubes (SWNTs) has been studied in two ways. Firstly, a novel iron nanoparticle catalyst for the production of single–walled nanotubes was developed. CVD conditions were established that produced high quality tubes. These optimised CVD conditions were then used as the basis of several comparative CVD experiments showing that the quality of nanotubes and the yield of carbon depended on the availability of carbon to react. The availability could be controlled by the varying concentration of methane in the gas phase or the residence time of the methane over the catalyst. Evidence is presented that the diameters of the tubes produced were affected by the availability of methane. A second mechanistic investigation was carried out to study the validity of the previously proposed ring addition mechanism for the growth of carbon nanotubes from camphor. In this mechanism, the formation of tubes is thought to occur through the addition of preformed carbon rings: so it would be expected that there would be a relationship between the molecular structure of the precursor and the resulting SWNTs. To explore this relationship, comparative CVDs were carried out to produce SWNTs with several different cyclic and acyclic compounds similar in structure to camphor. The vapour pressure and the chemical stability of the precursor were found to be important to the formation of nanotubes, while the compound’s structure was not related to the quality of tubes produced. The lack of a relationship between the structure of the precursor and the production of SWNTs suggests that preformed rings are not vital to the production of SWNTs. Differences in the growth of SWNT from benzene and methane were related to the stability of each compound. In particular, differences in the distributions of the diameters of the tubes formed from methane and benzene have been observed. These differences have been explained in terms of the relative kinetic stabilities of these molecules, and in terms of a competition between end–cap and sidewall growth. Positioning of nanotubes on surfaces has been explored using two approaches. In the first approach, commercially obtained SWNTs were functionalized by a sulfur plasma so that the products would form bonds with gold surfaces. The nanotubes were found to selectively deposit themselves onto gold surfaces from ethanolic dispersions of the functionalized samples. This selective deposition of the nanotubes allowed the production of prototype carbon nanotube field–effect transistors with higher device yields than were obtained with unfunctionalized tubes. In a second approach to positioning of carbon nanotubes, the growth of tubes on surfaces by CVD was explored. Iron nitrate and different magnesium compounds were dip–coated onto SiO2 surfaces so that MgO supported–Fe catalysts would be formed by calcination. SWNTs were grown on the surfaces by CVD. Surface area measurements of the equivalent powdered catalysts showed that a high surface area was vital to produce dense growth of high quality SWNTs. The morphology of the surface was also found to play a key role in the growth of the tubes. Patterned growth of carbon nanotubes was accomplished using soft lithography techniques to control the localization of catalyst deposition onto a surface. A long calcination step (10 h, 950 °C) before CVD, was found to improve the quality of nanotubes grown. Catalysts that had been calcined for 10 hours were also found to produce smaller diameter nanotubes than uncalcined samples. The formation of smaller diameter tubes was explained in terms of the formation of MgFe2O4 alloys, consistent with results reported previously in the literature. In addition, Raman spectroscopy of the calcined catalysts with 3% w/w loadings of Fe was used to confirm directly the presence of MgFe2O4.

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Stoppiello, Craig Thomas. "Inorganic synthesis inside carbon nanotubes." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/41855/.

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The use of single-walled carbon nanotubes (SWNTs) as test tubes for the encapsulation of metallic nanoparticles (MNPs) and the formation of inorganic nanomaterials has been advanced. A methodology to encapsulate the group 10 and 11 metals inside SWNTs to investigate their properties has been optimised. Each metal interacts with carbon differently at the atomic level, as shown by aberration-corrected high resolution transmission electron microscopy (AC-HRTEM), leading to the promotion of a plethora of different processes stimulated by MNPs under the electron beam. Additionally, interactions between SWNTs and small clusters of the group 10 metals have been examined, revealing marked differences between metal-carbon bonding for each metal. This has allowed for a useful insight into metal-carbon interactions on the atomic level which could have profound implications on the future development of new catalysts or nanoscale devices. Following on from this, a series of chemical reactions with platinum compounds were carried out within SWNTs which have shown SWNTs to be both a very effective reaction vessel and template for the formation of low-dimensional PtX2 (X = I, S) nanocrystals, materials that are difficult to create by traditional synthetic methods. The stepwise synthesis within SWNTs has enabled the formation of the platinum compounds to be monitored at each reaction stage by AC-HRTEM, verifying the atomic structures of the products and intermediates, and also by an innovative combination of fluorescence-detected X-ray absorption spectroscopy (FD-XAS) and Raman spectroscopy, monitoring the oxidation states of the platinum guest compounds within the nanotube and the vibrational properties of the host SWNT respectively. The stepwise synthesis has appeared to offer only limited preparative potential because of the lack of stoichiometric control in the resultant inorganic nanomaterials. A new approach for nanoscale synthesis in nanotubes developed in this study utilises the versatile coordination chemistry of platinum which has enabled the insertion of the required chemical elements (e.g. metal, and halogens or chalcogens) into the nanoreactor in the correct proportions for the controlled formation of PtI¬2 and PtS2 with the exact stoichiometry and structure. FD-XAS has also been used to probe the transformations of Pt(acac)2@SWNT to Pt@SWNT, and Cu(acac)2@SWNT to Cu2Ox@SWNT (where x > 1). It was shown that the temperature of both transformations was significantly lower than required for the same reactions in the bulk, which demonstrates the ability of SWNTs to lower the activation energy by polarising encapsulated molecules. Finally, a variety of novel MNPs and MO¬x¬ (M = Pt, Pd, Ni) materials were encapsulated within hollow graphitised carbon nanofibres (GNFs) and evaluated for the sensing of glucose. MOx@GNFs were revealed to be more active sensors than their corresponding MNPs which can be attributed to the increase in Lewis acidity of the metal centres upon oxide formation. Furthermore, the effectiveness of each metal and their corresponding oxides for glucose detection was found to increase in the order Pt > Pd > Ni which can be attributed to both physical and chemical properties of the respective metals. Overall, this thesis demonstrates that nanotubes can be used effectively to not only investigate chemical transformations on the atomic level, but also act as nano-sized test tubes and templates for the formation of novel, low-dimensional inorganic materials with bespoke structure and composition.

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19

Hou, Guangfeng. "Multiphysics Gas Phase Pyrolysis Synthesis of Carbon Nanotube Yarn and Sheet." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491559118937508.

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20

Kerr, Brittany. "Strengthening Potential of Single-Walled Carbon Nanotubes in Phenolic Resin Composites." Master's thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2219.

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Strengthening potential of single-walled carbon nanotubes (SWCNTs) in a phenolic resin composite was evaluated by characterization of purified and phenyl sulfonated SWCNTs, investigation of the load transfer capability of the purified SWCNTs, and characterization of the composites. Purified and phenyl sulfonated SWCNTs, as well as their composites, were examined by Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy equipped with energy dispersive spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and ultra violet-visible spectrometry. Fabrication of the SWCNT/phenolic resin composite was performed by first dispersing the SWCNTs in ethylene glycol and then homogenizing the mixture with phenolic resin. The ethylene glycol was then evaporated from the mixture and the SWCNT/phenolic resin composite was cured at 200°C for 1 hour. The dispersion of SWCNTs in the phenolic resin was reduced with higher SWCNT concentrations. Load was transferred from the phenolic resin to the purified SWCNTs. This demonstrated the potential to strengthen phenolic resin composite with SWCNT reinforcement. The load transfer efficiency in total tension (0.8%) decreased with an increase in SWCNT concentration, while in total compression (-0.8%), the load transfer efficiency remained constant. At very low strain (± 0.2%), the load transfer efficiency remained constant regardless of SWCNT concentration in both tension and compression. Characterization of the phenyl sulfonated SWCNTs indicated that calcium was introduced as a contaminant that interfered with functionalization of the SWCNTs. The use of contaminated phenyl sulfonated SWCNTs resulted in macroscopic inhomogeneity within the composite. M.S. Department of Mechanical, Materials and Aerospace Engineering; Engineering and Computer Science Materials Science & Engr MSMSE

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21

Deck, Christian Peter. "Carbon nanotubes synthesis, characterization, and applications /." Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3350004.

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Thesis (Ph. D.)--University of California, San Diego, 2009. Title from first page of PDF file (viewed May 4, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 329-375).

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22

Pattinson, Sebastian William. "Controlling the synthesis of carbon nanotubes." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607932.

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23

Li, Qiang. "Growth of carbon nanotubes on electrospun cellulose fibres for high performance supercapacitors and carbon fibre composites." Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/34360.

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The production of cellulose derived hybrid carbon nanofibre (CNF)/carbon nanotubes (CNTs) electrodes for the fabrication of supercapacitors and carbon fibre composites was investigated. The CNTs were grown via a floating catalyst chemical vapor deposition (CVD) method on the top surface of electrospun cellulose derived CNFs. These CNF and CNF/CNTs samples were then used as electrodes to produce liquid electrolyte-based supercapacitors. The growth of CNTs leads to an improvement of electrochemical performance compared to the plain CNFs. This improvement is due to the grown CNTs enlarging the reactive sites through enhanced surface area and porosity, and thereby increasing the conductivity of the system. CNTs have been also grown onto CNFs containing ferrocene and SiC particles. Composites were fabricated by combining the fibres and CNTs grown fibres with model polymers. The stress transfer properties of these materials have been estimated using an in situ Raman spectroscopic method by observing the shift of the Raman band during the tensile deformation of model polymer composites. Using this method, the elastic modulus of CNF/SiC/CNTs fibres has been estimated to be 208 ± 26 GPa. No shifts in the peak positions of bands relating to the carbon structure were obtained for in situ Raman spectroscopic studies of the CNF/CNTs fibres made from the ferrocene embedded fibres. This was thought to be due to the low yield of CNTs on the surface of the fibres. Furthermore, CNF/CNTs electrode-based structural supercapacitors, combining a solid electrolyte with the carbonized fibres, have been produced. These CNF/CNTs electrodes have a better capacitive performance than the plain CNF electrodes. There was a decrease in this performance with increased curing time of the resin, from 2 to 24 h, due to a lack of charge carrier mobility in the latter samples. A Raman spectroscopic study of the deformation of the carbon structures showed that the G-band shift towards a lower wavenumber position for the CNF and CNF/CNTs samples processed at a carbonization temperature of 2000 °C. Moduli of these fibres were estimated to be ~145 GPa and ~271 GPa, respectively, suggesting the growth of CNTs not only enhances the capacitive performance but also the mechanical properties of the structural supercapacitors. No Raman bend shift was found for the CNFs and CNF/CNTs samples processed below a carbonization temperature of 2000 °C, e.g. 900 °C and 1500 °C. This is because the graphitic structures are not well developed at carbonization temperatures below 1500 °C.

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Boehle, Matthew C. "Synthesis and Characterization of a Carbon Nanotube Based Composite Strain Sensor." University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1462201576.

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25

Vinten, Phillip A. "Chemical Vapour Deposition Growth of Carbon Nanotube Forests: Kinetics, Morphology, Composition, and Their Mechanisms." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24165.

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This thesis analyzes the chemical vapour deposition (CVD) growth of vertically aligned carbon nanotube (CNT) forests in order to understand how CNT forests grow, why they stop growing, and how to control the properties of the synthesized CNTs. In situ kinetics data of the growth of CNT forests are gathered by in situ optical microscopy. The overall morphology of the forests and the characteristics of the individual CNTs in the forests are investigated using scanning electron microscopy and Raman spectroscopy. The in situ data show that forest growth and termination are activated processes (with activation energies on the order of 1 eV), suggesting a possible chemical origin. The activation energy changes at a critical temperature for ethanol CVD (approximately 870°C). These activation energies and critical temperature are also seen in the temperature dependence of several important characteristics of the CNTs, including the defect density as determined by Raman spectroscopy. This observation is seen across several CVD processes and suggests a mechanism of defect healing. The CNT diameter also depends on the growth temperature. In this thesis, a thermodynamic model is proposed. This model predicts a temperature and pressure dependence of the CNT diameter from the thermodynamics of the synthesis reaction and the effect of strain on the enthalpy of formation of CNTs. The forest morphology suggests significant interaction between the constituent CNTs. These interactions may play a role in termination. The morphology, in particular a microscale rippling feature that is capable of diffracting light, suggest a non-uniform growth rate across the forest. A gas phase diffusion model predicts a non-uniform distribution of the source gas. This gas phase diffusion is suggested as a possible explanation for the non-uniform growth rate. The gas phase diffusion is important because growth by acetylene CVD is found to be very efficient (approximately 30% of the acetylene is converted to CNTs). It is seen that multiple mechanisms are active during CNT growth. The results of this thesis provide insight into both the basic understanding of the microscopic processes involved in CVD growth and how to control the properties of the synthesized CNTs.

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geng, xi. "synthesis and characterization of nanostructured carbon supported Pt-based electrocatalysts." Digital WPI, 2012. https://digitalcommons.wpi.edu/etd-theses/83.

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Fuel cell, as an alternative green power source for automobiles and portable electronics, has attracted worldwide attention due to its desirable properties such as high energy density and low greenhouse gas emission. Despite great progress in the past decades, several challenges still remain as obstacles for the large-scale commercialization. Among them, the high cost of Pt-based electrode material is considered as a major barrier, while the life span or stability of electrode catalysts is another concern since the electrocatalysts can be easily poisoned during the fuel cell operation. In order to overcome these issues, nanostructured carbon materials, especially carbon nanotubes (CNTs), are studied as catalyst support. In addition, recent research also suggests that the coupling of a second metal element with Pt can effectively protect the electrocatalysts from being poisoned and thus improve their long-term durability. The objective of the present work was to demonstrate an efficient synthetic method for the preparation of CNTs supported binary PtM (M=Ru, Sn) electrocatalysts. In this project, a polymer wrapping technique along with an in-situ polyol reduction strategy was adopted to decorate well-dispersed binary PtM nanoparticles on the surface of modified-CNTs. The unique nanostructures as well as the excellent catalytic activities of the as-prepared nanohybirds were investigated through a diversity of physiochemical and electrochemical characterization techniques. This fabrication method provided a simple and convenient route to assemble Pt-based catalyst on carbon substrates, which is useful for the further development of high-performance fuel cell catalysts.

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Linck, Nicholas W. "PRECISE CONTROL OF CARBON NANOTUBE MEMBRANE STRUCTURE FOR ENZYME MIMETIC CATALYSIS." UKnowledge, 2014. http://uknowledge.uky.edu/cme_etds/35.

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The ability to fabricate a charge-driven water pump is a crucial step toward mimicking the catalytic ability of natural enzyme systems. The first step towards making this water pump a reality is the ability to make a carbon nanotube (CNT) membrane with uniform, 0.8 nm pore diameter. Proposed in this work is a method for synthesizing these carbon nanotubes via VPI-5 zeolite templated, transition metal catalyzed pyrolysis. Using a membrane composed of these CNTs, it is possible to get water molecules to flow single file at a high flow rate, and to orient them in such a way that would maximize their ability to be catalyzed. Additionally, using the ability to plate a monolayer of precious metal catalyst molecules around the exit to the membrane, catalyst efficiency can be maximized by making every catalyst atom come into contact with a substrate molecule. In this work, we also demonstrate the ability to plate a monolayer of precious metal catalyst atoms onto an insulating, mesoporous, support material. By combining these two chemical processes, it is possible to mimic the catalytic efficiency of natural enzyme systems.

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Ecton, Philip. "Low-Energy Electron Irradiation of Preheated and Gas-Exposed Single-Wall Carbon Nanotubes." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc955114/.

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We investigate the conditions under which electron irradiation of single-walled carbon nanotube (SWCNT) bundles with 2 keV electrons produces an increase in the Raman D peak. We find that an increase in the D peak does not occur when SWCNTs are preheated in situ at 600 C for 1 h in ultrahigh vacuum (UHV) before irradiation is performed. Exposing SWCNTs to air or other gases after preheating in UHV and before irradiation results in an increase in the D peak. Small diameter SWCNTs that are not preheated or preheated and exposed to air show a significant increase in the D and G bands after irradiation. X-ray photoelectron spectroscopy shows no chemical shifts in the C1s peak of SWCNTs that have been irradiated versus SWCNTs that have not been irradiated, suggesting that the increase in the D peak is not due to chemisorption of adsorbates on the nanotubes.

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Pokhrel, Sewa. "FISCHER- TROPSCH SYNTHESIS ON FUNCTIONALIZED CARBON NANOTUBES." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1408.

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The aim of this research was to investigate the role of chemical functionalization on carbon nanotubes surfaces and its effect on FT catalysis. Multi walled carbon nanotubes (MWNT) were first treated with acid (HCl) to remove the residual metal particles and were then functionalized using H2O2 and HNO3 to introduce oxygen-containing groups to the MWNT surface. These treatments also add defects on MWNT surface. Morphological analyses were performed on the MWNT samples with TEM and it was found that the peroxide and acid treated MWNTs showed an increase oxygen functional groups and created additional surface defects on the MWNTs. Results of FT experiments showed enhanced CO conversion, FT activity and product selectivity towards liquid hydrocarbons due to functionalization. The liquid selectivity was found to be significantly high for H2O2 treated catalyst. HNO3 treated catalyst had highest activity although selectivity to methane and CO2 was found higher than the H2O2 treated catalyst. It was observed that the chemical treatments increase the carbon chain length of the produced hydrocarbons. While comparing hydrocarbon distribution of as-produced and H2O2 treated MWNT, it was found that carbon-chain length increases for peroxide treated catalyst. Along with as-produced and functionalized nanotube, FT experiments were also conducted using B-doped sponge, un-doped sponge and N-doped CNT catalyst. B-doped sponge showed enhanced CO conversion and FT activity as compared to un-doped sponge. Conversion and product selectivity were found to be affected by temperature when test was conducted with N-CNT. Operating conditions like temperature, syngas feed flow rate and syngas ratio were also to impact the FT performance.

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Sunden, Erik Oscar. "Carbon Nanotube Synthesis for Microsystems Applications." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11528.

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Modern day engineering systems research presently lacks techniques to exploit the unique properties of many nanomaterials; coupled with this challenge exists the need to interface these nanomaterials with microscale and macroscale platforms. A nanomaterial of particular interest is the carbon nanotube (CNT), due to its enhanced physical properties. In addition to varied electrical properties, the CNT has demonstrated high thermal conductivity and tensile strength compared to conventional fiber materials. CNTs are beginning to see commercial applications in areas in which sufficient study has been dedicated. While a large part of the worldwide focus of CNT research has been in synthesis, an equally important area of research lies in CNT integration processes. The unique and useful properties of many nanostructured materials will never be realized in mainstream manufacturing processes and commercial applications without the proper exploration of integration methods such as those detailed in this thesis. The primary motivation for the research detailed in this thesis has been to develop CNT synthesis processing techniques that allow for novel interfacing methods between carbon nanotubes and eventual applications. In this study, an investigation was performed to look at several approaches to integrating CNTs into micro-electromechanical systems (MEMS). Synthesis of CNTs was studied in two different settings. Synthesis was first performed, directly on the microsystem, via a global scale chemical vapor deposition (CVD) process. Secondly, synthesis was performed directly onto a microsystem device via localized resistive heating. Following synthesis, the application of atomically layered, protective coatings was then investigated. Integration methods were then investigated to allow for CNT transfer to microsystem applications incapable of withstanding synthesis temperatures. The developed integration methods were evaluated by creating functional microscale electrical circuits in flexible substrates via hot emboss imprint lithography. Lastly, post synthesis processing methods were used to create micropatterned cell guidance substrates as well as neuronal stimulating substrates.

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31

Bayazit, Mustafa Kemal. "Synthesis and properties of chemically modified carbon nanotubes." Thesis, Durham University, 2010. http://etheses.dur.ac.uk/390/.

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Since their discovery single-walled carbon nanotubes (SWNTs) have gained the interest of many scientists and engineers due to their prominent structural, mechanical and electronic properties which make them applicable in various areas including electronics, chemical and biological sensing and reinforced composite materials. Although SWNTs have many application areas their use can be limited since they are synthesised as a mixture of metallic and semiconducting species with different diameters and helicities and they have limited solubility in aqueous and non-aqueous solvents. Covalent modification of SWNTs is an important tool to introduce new functional groups onto the surface of nanotubes to improve their solubility and processability. It can also be used to separate metallic from semiconducting nanotubes. The work presented here has concentrated on the non-disruptive covalent modification of SWNTs using pyridine diazonium salt addition, 1,3-dipolar cycloaddition and reductive alkylation. The selectivitiy of the addition was probed by UV-vis-NIR and Raman spectroscopy where the metallic were found to be more selective than semiconducting SWNTs. The location and distribution of the functional groups was determined by AFM using electrostatic interactions with gold nanoparticles. Rheological data showed that the pyridine modified SWNTs were able to act as crosslinkers and hydrogen bond to poly(acrylic acid) to form SWNT hydrogels. The indolizine modified SWNTs, emitted blue light when excited ca. 330 nm, were capable of sensing 4-nitrophenol, 3-nitrophenol, 2-nitrophenol, 2-nitrosotoluene and 2,4-dinitrotoluene with a detection limit of ca. 10-8 M. The modified SWNTs were further characterised using FTIR, XPS, TGA-MS and optical microscopy.

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Hudziak, Stephen. "Iron-filled carbon nanotubes : Synthesis, characterisation and applications." Thesis, Queen Mary, University of London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.528419.

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Bondi, Scott Nicholas. "LCVD synthesis of carbon nanotubes and their characterization." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-08112004-143541/unrestricted/bondi%5Fscott%5Fn%5F200412%5Fphd.pdf.

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Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2005. Z.L. Wang, Committee Member ; Thomas Starr, Committee Member ; Mostafa Ghiaasiaan, Committee Member ; W. Jack Lackey, Committee Chair; Shreyes Melkote, Committee Member. Vita. Includes bibliographical references.

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Height, Murray John 1975. "Flame synthesis of carbon nanotubes and metallic nanomaterials." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/49807.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2003. Includes bibliographical references. Carbon nanotubes are a remarkable material with many appealing properties. Despite the appeal of this material, there are few synthesis techniques capable of producing nanotubes in large quantities at low-cost. The broad objective of this study was to examine the potential of a premixed flame for the synthesis of carbon nanotubes with the view that flame synthesis may prove a means of continuous production at low-cost. The specific approach focused on the formation of metallic nanoparticles in flames; identification of nanotube formation zones, time scales, and transition conditions; characterization of material properties; and the development of a formation mechanism and associated flame-model. Carbon nanotube formation requires a source of carbon, a source of heat and the presence of metal particles. A fuel-rich flame is a high-temperature, carbon-rich environment and addition of metal is likely to give conditions suitable for nanotube growth. This study considered a premixed acetylene/oxygen/15 mol% argon flame doped with iron pentacarbonyl (Fe(CO)₅) vapor (typically 6100 ppm), operated at 50 Torr pressure and 30 cm/s cold gas feed velocity. The flame was investigated with regard to the growth of metal particles and subsequent formation and growth of carbon nanotubes. Thermophoretic samples were extracted from the flame at various heights above burner (HAB) and analyzed using transmission electron microscopy (TEM). HAB is representative of residence time in the flame. Size distribution and number density data were extracted from TEM images using a quantitative image analysis technique. The mean particle size for a precursor concentration of 6100 ppm was observed to increase from around 2 to 4 nm between 20 and 75 mm HAB. (cont.) The particle number density results showed a decreasing number density with increasing HAB, giving a complementary picture of the particle dynamics in the flame. Single-walled carbon nanotubes (SWNT) were also observed to form in the premixed flame. Thermophoretic sampling and TEM analysis gave insight into nanotube formation dynamics. Nanotube structures were observed to form as early as 30 mm HAB (20 ms) with growth proceeding rapidly within the next 10 to 20 mm HAB. The growth-rate for the nanotubes in this interval is estimated to be between 10 and 100 ptm per second. The upper region of the flame (50 to 70 mm HAB; 35 to 53 ms) is dominated by tangled web structures formed via the coalescence of individual nanotubes formed earlier in the flame. The nanotube structures are exclusively single-walled with no multi-walled nanotubes observed in any of the flame samples. The effect of carbon availability on nanotube formation was tested by collecting samples over a range of fuel equivalence ratios at fixed HAB. The morphology of the collected material revealed a nanotube formation 'window' of 1.5 < < 1.9, with lower dominated by discrete particles and higher favoring soot-like structures. These results were also verified using Raman spectroscopy. A clear trend of improved nanotube quality (number and length of nanotubes) is observed at lower . More filaments were observed with increasing concentration, however the length (and quality) of the nanotubes appeared higher at lower concentrations ... by Murray John Height. Ph.D.

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Alagiri, Praveenkumar. "FISCHER-TROPCH SYNTHESIS ON COMMERCIALLY AVAILABLE CARBON NANOTUBES." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/2052.

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The aim of this research is to investigate the role of chemical functionalization on carbon nanotubes and its effect on the FT synthesis. Multi walled carbon nanotubes (MWNT) bought from the market were functionalized using HNO3 to introduce oxygen-containing groups to the MWNT surface. This treatment also adds defects on MWNT surface. Carboxyl functionalized multiwall carbon nanotubes (-COOH) and hydroxyl functionalized multiwall carbon nanotubes (-OH) were also bought from the market and used in the experiments, Results of FT experiments showed very high CO conversion. Fischer Tropsch activity and product selectivity were towards liquid hydrocarbons due to functionalization. Highly desired product distribution were obtained due to chemical functionalization of CNTs. The performance of all the functionalized Multi wall nanotubes was better than the pure Multi wall nanotubes. Operating conditions like temperature, syngas feed flow rate and syngas ratio were also to impact the FT performance.

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Chizari, Kambiz. "Synthesis of nitrogen-doped carbon nanotubes : catalytic applications." Strasbourg, 2011. http://www.theses.fr/2011STRA6047.

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Depuis la découverte des nanotubes de carbone (CNT) en 1991, beaucoup d'efforts ont été faits afin de connaître leurs propriétés intrinsèques et les applications possibles. Une des méthodes les plus efficaces, utilisée pour modifier ses propriétés physiques et chimiques, est le dopage de CNT à l'azote ou le bore. L’objectif de ce travail est de réaliser la synthèse de nanotubes de carbone dopés à l’azote (N-CNT) et d'étudier les performances catalytiques de ce matériau soit en tant que support de catalyseur soit directement comme catalyseur. L'influence des différents paramètres de synthèse sur les propriétés des N-CNT a été étudiée. Par la suite, les N-CNT ont été utilisés comme support de catalyseur pour l'hydrogénation du cinnamaldéhyde et leurs performances catalytiques ont été comparées à celles des CNT non-dopés. Il a été montré que les N-CNT synthétisés dans des conditions différentes présentent différentes performances catalytiques. Les N-CNT ont également été utilisés en tant que catalyseur pour l'oxydation sélective de l'H2S en soufre élémentaire et les résultats sont discutés dans cette thèse. Enfin, les études réalisées avec les nanotubes de carbone ont été transposées sur un matériau nouveau et prometteur qu’est le graphène et/ou graphène multi-couche. Nous avons dans un premier temps synthétisé ce matériau à partir de graphite expansé en utilisant les irradiations micro-ondes, puis une étude préliminaire a également été faite sur le dopage à l’azote de ce matériau par un traitement aux micro-ondes du graphite expansé dispersé dans de l'hydroxyde d'ammonium. Le FLG est utilisé dans ce travail comme support de catalyseur pour la réaction d'hydrogénation du cinnamaldéhyde et ses performances catalytiques sont comparées à d'autres catalyseurs supportés sur des supports tels que le graphite naturel, le graphite expansé et les nanotubes de carbone Since the discovery of carbon nanotubes (CNT) in 1991, a lot of efforts have been done in order to find out their intrinsic properties and their possible applications. One of the most efficient methods used for tuning its physical and chemical properties is doping CNTs by nitrogen or boron. The aim of this work deals with the synthesis of nitrogen-doped carbon nanotubes (N-CNTs) and with the study of the catalytic performance of this material either as catalyst support or as a metal-free catalyst. The influence of the different synthesis parameters on the physical and chemical properties of the N-CNTs was investigated. Afterwards, the N-CNTs were used as catalyst support for the hydrogenation of cinnamaldehyde and its catalytic performance was compared to that obtained on the undoped CNTs. It was shown that N-CNTs synthesized in different conditions lead to different catalytic performances which was mainly linked with the nature of the incorporated nitrogen species. The N-CNTs were also employed as a metal-free catalyst for the selective oxidation of H2S into elemental sulfur and the results are discussed within this thesis. Recently 2D carbon material, namely graphene, has received a great interest due to its special physical properties. The previous investigations on the other graphitic material such as carbon nanotubes facilitate the understanding of the properties and behavior of this material. In this thesis we also worked on the synthesis of the few-layer graphene (FLG), using microwave irradiations. A preliminary study has also done on the nitrogen-doping of this material by microwave treatment on the expanded graphite dispersed in ammonium hydroxide. The FLGs were used as a catalyst support for the hydrogenation of cinnamaldehyde and its catalytic performance is compared to other graphitic materials such as natural graphite, expanded graphite and carbon nanotubes

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Huang, Guannan. "Evaluation of airborne particle emissions from commercial products containing carbon nanotubes." Thesis, University of Iowa, 2012. https://ir.uiowa.edu/etd/2899.

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In this study, we developed and standardized a sanding method to evaluate the emission of airborne particles from products that contain carbon nanotubes (CNTs) under different conditions, including three types of sandpaper and three sanding disc speed. We also characterized the emission of the airborne particles from one neat epoxy test sample, four CNTs-incorporating test samples with different CNTs loading, and two commercial products. The total number concentration, respirable mass concentration, and particle size number/mass distribution of the emitted particles were calculated and compared, followed by an electron microscopy (EM) analysis. These data suggest that the sanding process can produce substantial quantities of airborne particles. Also, the emission of airborne particles was associated with different test conditions. EM analysis of the airborne particle samples showed embedded CNTs protruding from the outer surface, which was different from CNTs-incorporating bulk material. Our study suggests a potential generation of particles during the life cycle event of sanding. Further studies should be carried out to investigate the potential human health hazard in other life cycle events.

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Islam, Md Mazharul. "Printed transparent conducting electrodes based on carbon nanotubes (CNTs), reduced graphene oxide (rGO), and a polymer matrix." Thesis, Umeå universitet, Institutionen för fysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-156366.

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The main focus of this project was to prepare transparent and conductive electrodes (TCEs). TCEs were made out of multi-walled carbon nanotubes (MWCNTs), reduced graphene oxide (rGO), and polyvinylpyrrolidone (PVP). Based on the theoretical aspect, MWCNTs has emerged as a promising nanofiller in the polymer matrix due to its high electrical conductivity. As a nanofiller, MWCNTs were used with a small ratio of rGO with PVP as a polymer matrix in this project to prepare TCEs having low sheet resistance with high transparency. An appropriate amount of PVP has been shown to be a good combination with MWCNTs and rGO in the solvent to keep MWCNTs dispersed for a long time. Carboxyl group (-COOH) functionalized MWCNTs (FMWCNTs) was produced in a controlled oxidative procedure due to enabling good dispersion of FMWCNTs in water and ethanol solvents. In contrast, water dispersible rGO was chemically prepared by using GO and sodium borohydride where GO was produced from graphite by using improved Hummer's method. Drop casting and spray coating methods were applied to fabricate TCEswhere only water was used as the solvent for drop casted TCEs and a mixing ratio of water and ethanol was 70:30 as solvent for spray coated TCEs. It was also determined in this project that the spray coating method was more suitable for preparing TCEs rather than thedrop casting method due to easy fabrication, large area coating possibility, and the smoothness of the coated film surface. The sheet resistance was obtained as 5026 Ω/ ⃣ where the transparency was 65% in the case of the drop casted electrode for the ratio of rGO:FMWCNTs:PVP was 1.2:60:1 with 0.02 mg FMWCNTs. In the case of spray coated electrode at the same ratio of rGO:FMWCNTs:PVP, the sheet resistance was measured as 5961 Ω/ ⃣ where the transparency was 73%. But in the case of 60:1 mass ratio of FMWCNTs:PVP with 0.02 mg FMWCNTs, the sheet resistance was 7729 Ω/ ⃣ and transparency was 77% for spray coated electrode. So, it is clear that the sheet resistance was improved by adding a small mass ratio of rGO with FMWCNTs:PVP.

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Wicks, Sunny S. "Mechanical enhancement of woven composites with radially aligned carbon nanotubes (CNTs) : investigation of Mode I fracture toughness." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59697.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2010. Cataloged from PDF version of thesis. Includes bibliographical references (p. 69-74). Composites have seen an increasing role in aerospace structures that demand lightweight, strong, and stiff materials. Composites are attractive structural materials with outstanding mechanical and physical properties, as well as directional fabrication control and tailorability, though these advantages come with increased complexity and challenging failure modes. Matrix-rich regions at ply interfaces especially are susceptible to damage and matrix cracking, leading to delamination and a reduction of mechanical properties. Several manufacturing solutions such as stitching, z-pinning, and braiding have been developed by the aerospace industry to provide through-thickness reinforcement and improve interlaminar properties, though these improvements come with concomitant reductions in important in-plane properties. This thesis describes the design, manufacturing, and testing of woven composites with aligned carbon nanotubes (CNTs) integrated into the bulk composite, focusing here particularly on interlaminar reinforcement at ply interfaces. Implementing aligned CNTs takes advantage of their scale and superior specific stiffness and strength, with in-plane properties maintained while interlaminar properties are enhanced by the CNTs bridging across matrix-rich interfaces. Significant improvement in Mode I fracture toughness is observed experimentally with over 60% increase in both initiation and steady-state Mode I fracture toughnesses (steady-state toughness improves from 2.1 to 3.7 kJ/m² ). This enhancement is attributed to CNT crackbridging and pullout, in agreement with a first-order model, confirming the viability of CNTs to improve composite interlaminar properties. Future work to follow this thesis will focus on development of a vacuum-assisted infusion manufacturing process implementation of the 'fuzzy'-fiber reinforced nano-engineered composite architecture with alternate fiber and polymer systems, and exploring multifunctional applications of these materials. by Sunny S. Wicks. S.M.

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40

Ahmed, Muhammad Shafiq. "Characterization of carbon nanotubes grown by chemical vapour deposition." Thesis, UOIT, 2009. http://hdl.handle.net/10155/26.

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Carbon nanotubes (CNTs), discovered by Ijima in 1991, are one of the allotropes of carbon, and can be described as cylinders of graphene sheet capped by hemifullerenes. CNTs have excellent electrical, mechanical, thermal and optical properties and very small size. Due to their unique properties and small size, CNTs have a great potential for use in electronics, medical applications, field emission devices (displays,scanning and electronprobes/microscopes) and reinforced composites. CNTs can be grown by different methods from a number of carbon sources such as graphite, CO,C2H4, CH4 and camphor. Under certain conditions, a metallic catalyst is used to initiate the growth. The three main methods used to grow CNTs are: Arc-discharge, laser ablation (LA) and chemical vapour deposition (CVD). In the present work CNTs were grown from a mixture of camphor (C10H16O) and ferrocene (C10H10Fe) using Chemical Vapour Deposition (CVD) and argon was used as a carrier gas. The iron particles from ferrocene acted as catalysts for growth. The substrates used for the growth of CNTs were crystalline Si and SiO2 (Quartz) placed in a quartz tube in a horizontal furnace. Several parameters have been found to affect the CNT growth process. The effects of three parameters: growth temperature, carrier gas (Ar) flow rate and catalyst concentration were investigated in the present work in order to optimize the growth conditions with a simple and economical CVD setup. The samples were characterized using electron microscopy (EM), thermogravimetirc analysis (TGA), Raman and FTIR spectroscopy techniques. It was found that the quality and yield of the CNTs were best at 800°C growth temperature, 80sccm flow rate and 4% catalyst concentration.

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Liu, JingJing. "Carbon nanotubes developed on ceramic constituents through chemical vapour deposition." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/9967.

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Carbon nanotubes (CNTs) were successfully grown on the surface of carbon fibre reinforcements in carbon fibre architecture through in-situ catalytic chemical vapour deposition (CCVD). Success was also implemented on powders of oxides and non-oxides, including Y-TZP powder, ball milled alumina powder, alumina grits, silicon carbide powder. Preliminary results have been achieved to demonstrate the feasibility of making ceramic composites consisting of CNTs reinforcements.

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Costa, Pedro M. F. J. "The synthesis and filling of double-walled carbon nanotubes." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401164.

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Friedrichs, Steffi. "The synthesis and filling of single-walled carbon nanotubes." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249550.

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Bailey, Sam R. "The synthesis and modification of single-walled carbon nanotubes." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275643.

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45

Weißker, Uhland. "Synthesis and mechanical properties of iron-filled carbon nanotubes." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-135707.

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Carbon forms the basis of a variety of compounds. The allotropic forms of carbon include graphene, fullerenes, graphite, carbon nanotubes and diamond. All these structures possess unique physical and chemical properties. This work focusses on the usage of carbon nanotubes (CNT), especially iron-filled CNT. An industrial application of CNT requires the understanding of the growth mechanism and the control of the synthesis process parameters. Regarding iron-filled CNT the shell formation as well as the filling process has to be understood in order to control the CNT morphology and distribution and dimension of the iron filling. The thesis involves two topics - synthesis of CNT and characterization of their mechanical properties. Chapter 2 of the present work deals with the synthesis of iron-filled CNT. In this thesis all experiments and the discussion about the growth process were conducted with respect to the demands of magnetic force microscopy probes. The experimental work was focused on the temperature profile of the furnace, the aluminum layer of the substrate, the precursor mass flow and their impact on the morphology of in-situ iron-filled CNT. By selecting appropriate process parameters for the temperature, sample position, gas flow and by controlling the precursor mass flow, CNT with a continuous filling of several microns in length were created. Existing growth models have been analyzed and controversially discussed in order to explain the formation of typical morphologies of in-situ filled CNT. In this work a modified growth model for the formation of in-situ filled CNT has been suggested. The combined-growth-mode model is capable to explain the experimental results. Experiments which were conducted with respect to the assumptions of this model, especially the role of the precursor mass flow, resulted in the formation of long and continuous iron nanowires encapsulated inside multi-walled CNT. The modified growth model and the synthesis results showed, that besides the complexity of the parameter interaction, a control of the morphology of in-situ iron-filled CNT is possible. In chapter 3 the measurements of mechanical properties of in-situ iron-filled CNT are presented. Two different experimental methods and setups were established, whereby one enabled a static bending measurement inside a TEM and another a dynamical excitation of flexural vibration of CNT inside SEM. For the first time mechanical properties and in particular the effective elastic modulus Eb of in-situ iron-filled CNT were determined based on the Euler-Bernoulli beam model (EBM). This continuum mechanic model can be applied to describe the mechanical properties of CNT and especially MWCNT in consideration of the restriction that CNT represent a macro molecular structure built of nested rolled-up graphene layers. For evaluation and determination of the elastic modulus the envelope of the resonant vibrating state was evaluated by fitting the EBM to the experimental data. The experiments also showed, that at the nanoscale the properties of sample attachment have to be taken into account. Thus, instead of a rigid boundary condition a torsion spring like behavior possessing a finite stiffness was used to model an one side clamped CNT. The extended data evaluation considering the elastic boundary conditions resulted in an average elastic modulus of Eb = 0.41 ± 0.11 TPa. The low standard deviation gives evidence for the homogeneity of the grown material. To some extend a correlation between the formation process, the morphology and the mechanical properties has been discussed. The obtained results prove the usability of this material as free standing tips for raster scanning microscopy and especially magnetic force microscopy. The developed methods provide the basis for further investigations of the CNT and the understanding of mechanical behavior in greater detail.

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Hofmann, Mario. "Synthesis and fluid interaction of ultra long carbon nanotubes." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/46606.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009. MIT Barker Library copy printed in pages. Includes bibliographical references (leaves 49-50). The successful integration for carbon nanotubes in future electronic applications relies on advances in their synthesis. In this work optimization of growth parameters was conducted to obtain ultra long carbon nanotubes. Their morphology was analyzed by means of different techniques and evidence of the occurrence of nanotube bundles was found. The effect of varying several parameters on the morphology of the obtained nanotubes was investigated and successful growth of ultra long nanotubes was achieved. The settling process, i.e. the sinking of the nanotubes to the substrate, of those nanotubes was investigated by a newly developed in-situ rotation tool and statistical data for their behavior during growth was obtained. by Mario Hofmann. S.M.

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Goswami, Gopal Krishna. "From Synthesis To Applications Of Pristine And Nitrogen-Doped Carbon Nanotubes." Thesis, 2012. http://hdl.handle.net/2005/2445.

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Carbon nanotubes (CNTs) are well known as excellent electrical conductors. However, their transport properties are limited by electrical breakdown in ambient. Moreover, the electronic properties can further be modulated by doping. Devices such as Schottky diodes, transistors and logic gates based on un-doped and doped CNT junctions have been realized. Recently, nitrogen doped CNTs show potential application in replacing platinum cathode catalyst in fuel cell technology. We synthesize pristine, nitrogen-doped and nitrogen-doped:pristine CNT intratubular junctions by one-step co-pyrolysis and explore them for different applications. We show that the position of electrical breakdown can be predicted which is essential to know for high current applications. Among other applications, we show that individual CNT intratubular junction exhibits rectifying characteristics. Further investigation indicates the intratubular junction behaves like Schottky diode. Lastly, the potential replacement of platinum by nitrogen doped CNTs in direct methanol fuel cell has been explored.

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Bhatia, Ravi. "Low Temperature Charge Transport And Magnetic Properties Of MWNTs/MWNT-Polystyrene Composites." Thesis, 2011. http://etd.iisc.ernet.in/handle/2005/2409.

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Carbon nanotubes (CNTs) have been recognized as potential candidates for mainstream device fabrication and technologies. CNTs have become a topic of interest worldwide due to their unique mechanical and electrical properties. In addition, CNTs possess high aspect ratio and low density that make them an important material for various technological applications. The field of carbon nanotube devices is rapidly evolving and attempts have been made to use CNTs in the fabrication of devices like field emitters, gas sensors, flow meters, batteries, CNT-field effect transistors etc. These molecular nanostructures are proposed to be an efficient hydrogen storage material. CNT cylindrical membranes are reported to be used as filters for the elimination of multiple components of heavy hydrocarbons from petroleum and for the filtration of bacterial contaminants of size less than 25 nm from water. Recently, CNT bundles have been proposed to be a good material for low-temperature sensing. CNTs have also been considered as promising filler materials due to extraordinary characteristics mentioned above. Fabrication of nanocomposites using CNTs as reinforcing material has completely renewed the research interest in polymer composites. The conductive and absorptive properties of insulating polymer doped with conducting filler are sensitive to the exposure to gas vapors and hence they can be used in monitoring various gases. The application of fiibre reinforced polymer composites in aeronautic industry are well known due to their high mechanical strength and light weight. Also, the conductive composite materials can be used for electromagnetic shielding. Desired properties in CNT-composites can be attained by adding small amount of CNTs in comparison to traditional filler materials. Due to high aspect ratio and low density of CNTs, percolation threshold in CNT-polymer composites can be achieved at 0.1 vol % as compared to ~16 vol. % in case of carbon particles. The research work ׽0.1 vol. %, as compared to reported in this thesis includes the preparation of multiwall carbon nanotube (MWNTs) and MWNT-polystyrene composites, experimental investigations on low temperature charge transport, and magnetic properties in these systems. This thesis contains 7 chapters. Chapter 1 provides an overview of CNTs and CNT-polymer composites. This chapter briefly describes the methods for synthesizing CNTs and fabricating CNT-polymer composites, charge transport mechanisms in CNTs and composites, and their magnetic properties as well. Chapter 2 deals with the concise introduction of various structural characterization tools and experimental techniques employed in the present work. An adequate knowledge of the strengths and limitations of experimental equipment can help in gathering necessary information about the sample, which helps in studying and interpreting its physical properties correctly. Chapter 3 describes the synthesis of MWNTs and their use as filler material for the fabrication of composites with polystyrene (PS). The characterization results of as-prepared MWNT and composites show that MWNTs possess high aspect ratio (~4000), and are well dispersed in the composite samples (thickness ~50-70 µm). The composite samples are prepared by varying the MWNT concentration from 0.1 to 15 wt %. The as¬fabricated composites are electrically conductive and expected to display novel magnetic properties since MWNTs are embedded with iron (Fe) nanoparticles. Chapter 4 presents the study of charge transport properties of aligned and random MWNTs in the temperature range 300-1.4 K. The low temperature electrical conductivity follows the weak localization (WL) and electron-electron (e-e) interaction model in both samples. The dominance of WL and e-e interaction is further verified by magneto-conductance (MC) measurements in the perpendicular magnetic field up to 11 T at low temperatures. The MC data of these samples consists of both positive and negative contributions, which originates from WL (at lower fields and higher temperatures) and e-e interaction (at higher fields and lower temperatures). Chapter 5 contains the results of charge transport studies in MWNT-PS composite near the percolation threshold (~0.4 wt %) at low temperatures down to 1.4 K. Metallic-like transport behavior is observed in composite sample of 0.4 wt %, which is quite unusual. In general, the usual activated transport is observed for systems near the percolation threshold. The unusual weak temperature dependence of conductivity in MWNT-PS sample at percolation threshold is further verified from the negligible frequency dependence of conductivity, in the temperature range from 300 to 5 K. Chapter 6 accounts on the experimental results of magnetization studies of MWNTs and MWNT-PS composites. The observation of maxima in coercivity and squareness ratio at 1 wt % of Fe-MWNT in a polymer matrix show the dominance of dipolar interactions among the encapsulated Fe-nanorods within MWNTs. The hysteresis loop of 0.1 wt % sample shows anomalous narrowing at low temperatures, which is due to significant contribution from shape anisotropy of Fe-nanorods. Chapter 7 presents brief summary and future perspectives of the research work reported in the thesis.

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Nhlabatsi, Zanele Precious. "Synthesis and characterization of copper-containing carbon nanotubes (CNTs) and their use in the removal of pollutants in water." Thesis, 2012. http://hdl.handle.net/10210/5040.

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M.Sc. Improper disposal of industrial effluents that contain heavy metals such as mercury causes a threat to the environment due to the toxic effects of such matal even at low concentrations. It is also known that sewage waste in water contains bacteria that pose a health hazard to human beings, animals and micro-organisms. One major concern is the transmission of diseases through drinking this water; which destabilizes the water supply. Water for human consumption therefore needs to be of high quality. In this study copper-containing multiwalled carbon nanotubes (Cu/MWCNTs) were investigated for their ability to remove and kill mercury (Hg2+) and Escherichia coli (E. coli), a major species found in the coliform bacteria. These Cu/MWCNTs were synthesized “in situ” by using an electric arc-discharge apparatus and separately via one of two multi-step wet chemical techniques namely; an electroless plating and impregnation method respectively. MWCNTs used for the wet techniques were synthesized by a nebulized spray pyrolysis (NSP) process using ferrocene/toluene under argon flow. These MWCNTs were purified and functionalized to introduce functional groups that made provision for the nucleation of the copper metal on the surface of MWCNTs. Infrared spectroscopy confirmed the successful introduction of COOH and O-H groups on the surface of MWCNTs. Raman spectroscopy confirmed a relative increase in the intensity the ratio of the D-band after functionalization. Deposition of the copper nanoparticles by electroless plating method in different volumes of 100 ml, 80 ml and 60 ml produced copper nanoparticles of varying sizes and distribution on the surface of MWCNTs. SEM images revealed densely and homogeneously distributed small sized copper nanoparticles that followed the trend; 100 ml> 80 ml > 60 ml. The volume proved to be a critical factor of the electroless plating bath with an increase or decrease of the volume affecting the concentration of the Cu2+ ions and HCHO, which also affected the pH of the plating solution.

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50

Singh, Laishram Tomba. "Synthesis Of Various Carbon Nanostructures And The Transport Properties Of Carbon Nanotubes." Thesis, 2011. http://etd.iisc.ernet.in/handle/2005/1940.

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Different carbon nanostructures have different properties and different applications. It is needed to synthesize good quality and also on large scale. From the point of industrial applications, highly productive and low cost synthesis method is very essential. Research has been done extensively on the intrinsic and individual properties of both single walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWC-NTs) in the range of nanometer to micrometer length scale. The important question is how the properties change beyond this length scale and if they are used in group in the form of an array instead of the individual carbon nanotubes (CNTs). Some applications require large current output, large energy production etc. For such kind of applications, it becomes essential to use CNTs in large number in the form of arrays or array, instead of using large numbers of CNTs in individual level. Future nanotechnology scope requires large scale application using the very rich intrinsic properties of the CNTs and nanomaterials. Keeping these problems and challenges in front, this thesis work is devoted to the research of the large scale synthesis of mm long MWCNTs, having different morphology and studies on various physical properties of MWCNTs in the form of arrays. Synthesis of mm long aligned and buckled MWCNTs have been reported for the first time. Generally buckled CNTs were obtained by compressing the straight CNTs. Apart from this, different morphologies like, aligned straight, helical or coiled CNTs are also synthesized. Resistance of the individual CNT increases with the increase in length. Resistance versus length of an array of CNT also shows similar behaviour. The thermal conductivity of CNT array is observed to decrease with the increase of array diameter (diameter �100 µm). There are few reports of the similar behaviour with the experiments done on small diameter CNT arrays (diameter �100 nm). From these observations, it seems that in the arrays of CNT, their intrinsic individual property is preserved though the magnitudes are different. The conductance measurements done on buckled CNT array by compressing it to apply uniaxial strain, shows the conductance oscillation. This conductance oscillation seems to be originating from the band gap change due to strain when the CNTs bend during compression. Recent research focuses on the arrays of CNT as they can carry large current of the order of several milliamperes that make the arrays suitable in nanoscale electronics and in controlling macroscopic devices such as light emitting diodes and electromotors. Regarding this aspect, a part of this thesis work is devoted on the application of CNT array to field effect transistor (FET) and study of thermoelectric power generation using CNT arrays. The entire thesis is based on the works discussed above. It has been organized as follows: Chapter 1 deals with introduction about the different carbon nanostructures and different synthesis methods. A brief introduction about the different current-voltage (IV) characteristics of SWCNTs and MWCNTs, length and diameter dependence and effect of the mode of contacts, are given. Some applications of the array of CNTs like buckling effect on compression, stretching of CNT into the form of rope, and conduction change on compression are discussed. Application of CNT as FET, as a thermometer, and thermoelectric effect of CNT are discussed. The electromechanical effect of CNT is also discussed briefly. Chapter 2 deals with experimental setup for synthesis of different morphologies of carbon nanostructures. The samples are characterized using common characterization techniques like, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. A brief introduction about Raman Spectroscopy of CNT is given. Chapter 3 reports the unusual IV characteristics and breakdown of long CNT arrays. The current carrying ability and the threshold voltage as a function of array diameter are reported. The effect of the ambient like temperature and pressure are discussed. Chapter 4 deals with theoretical models to analyze the IV characteristics reported in Chapter 3. It has been shown that a set of classical equations are applicable to quantum structures and the band gap can be evaluated. Chapter 5 describes with application of CNT arrays as temperature sensors. It has been shown that CNT arrays of suitable diameters are used as temperature sensors after calibration. Chapter 6 reports the high current FET application of CNT arrays. Effects of temperature and ambient pressure are discussed. The type of the majority charge carrier is determined. Chapter 7 deals with application of CNT arrays as thermoelectric power generator to get large thermoelectric current. Effects of different array diameter are discussed. Modulation of thermoemf with gate voltage is discussed. The type of the majority charge carrier is determined. Chapter 8 reports the effect of compressive strain on buckled MWCNT arrays. Conductance is measured during the compression of the array. Quantum electromechanical conductance oscillation is observed. The structural changes are observed with SEM. Raman spectroscopic study supports the explanation of the effect. Chapter 9 provides the conclusion and overall summary of the thesis.

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