To see the other types of publications on this topic, follow the link: Conducting Polymer Nanotubes.
Dissertations / Theses on the topic 'Conducting Polymer Nanotubes'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Conducting Polymer Nanotubes.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Tahhan, May. "Carbon nanotubes and conducting polymer composites." Intelligent Polymers Research Institute - Faculty of Science, 2004. http://ro.uow.edu.au/theses/407.
Full textAbstract:
A nanocomposite is defined as a material of more than one solid phase, where at least one dimension falls in the nanometer range. The combination of carbon nanotubes (CNT) and conducting polymers offers an attractive route for the production of novel compounds that can be used in a variety of application such as sensors, actuators, and molecular scale electronic devices. The ultimate goal of this work is to develop and investigate CNT composites that provide a structural functionality together with one or more other key functions. A variety of novel CNT dispersions were prepared using commercially available CNT systems such as Rice single-walled carbon nanotubes (RCNT), HiPco single-walled carbon nanotubes (HCNT), and Multi-walled carbon nanotube (MWCNT). This study explored the application of novel functional dispersing agents. Deoxyribose Nucleic Acid (DNA) a biological molecule, N- sopropylacrylamide 2-acrylamido-2-methyl-1-propanesulfonic acid (NIPPAm-AMPS) a polyelectrolyte, Didodecyldimethyl ammonium bromide (DDAB) a polymerizable compound, Poly(methoxyaniline-5-sulfonic acid) (PMAS) an inherently conducting polymer, and PVA an insulating polymer were some of the agents used to disperse the CNT. These dispersions were then evaluated in term of their stability and ability to effectively disperse the CNT. Solid-state CNT composites (mats) were then prepared by means of pressure filtration of the CNT/dispersant solutions. These mats were characterized using a variety of different techniques to determine their viability to be used as mechanical actuators or electrochemical devices. The characterization methods included cyclic voltammetry, conductivity, capacitance, atomic force microscopy, scanning electron microscopy, Young’s modulus, and actuation measurements. Abstract RCNT/conducting polymer composites were prepared by the electropolymerization of Pyrrole with a range of different dopant anions in the presence of different RCNT dispersions. In these composites, the RCNT were completely covered by the polymer, consequently the electrochemical responses of these composites were dominated by the electrochemistry of the polymers with the CNT functioning as a conductor element. Polypyrrole was also electropolymerized using functionalized multi-walled carbon nanotubes (FMWCNT) as dopant. Electropolymerization was carried out using galvanostatic and potentiostatic techniques on gold-coated Mylar and ITO-glass. It was determined that PPy/FMWCNT composites deposited on either electrode using potentiostatic deposition exhibited redox peaks. This redox behavior was not observed when the galvanostatic deposition was employed. HCNT/Polyaniline (PAn) composites were prepared by either casting a film from a solution of HCNT and PAn in 1,2-Dichlorobenzene, or by casting a film of PAn onto an existing HCNT mat. The latter exhibited the highest conductivity. The actuation behavior of these CNT composites was investigated and it was determined that the PAn component contributes to the actuation strain while the HCNT component contributes to Young’s modulus. The combination of the HCNT (with their mechanical properties) and PAn (with its actuator behavior) offers and attractive route not only to reinforce the polymer film but also to introduce new electronic properties based on morphological modifications or electronic interactions between the two components giving a robust blend of optimum properties. These results open the door for these composites to be used in a variety of applications that require a combination of the above characteristics such as mechanically reinforced actuator devices, robotics, optical fiber switches, prosthetic devices, and anti-vibration systems. In addition, PPy with a range of dopant anions was electrodeposited galvanostatically, potentiostatically, and potentiodynamically on the surface of four different carbon electrodes, RCNT mat (unannealed), RCNT mat (annealed), glassy carbon, and carbon foil. It was found that the method of electrodeposition was crucial to the electroactivity of the deposited polymers, particularly when deposited onto a RCNT mat due to the different interaction between the deposited polymer and the RCNT mat. Finally, HCNT/SDS, HCNT/PMAS, and HCNT/DNA fibers were prepared using the Particle Coagulating Spinning method (PCS). The annealing process resulted in a dramatic increase in conductivity of up to 2600 times higher compared to the unannealed fibers. However, the annealing process did not play any role in keeping the fibers together or modifying the alignment of the carbon nanotubes ropes within the fibers. The HCNT/DNA fibers, with their biocompatibility, high conductivity, and good mechanical properties can be used as artificial muscles, bioelectronic sensors, or even as platforms to support the growth of nerve cells. This thesis delineates the methods of successful production of solid sate CNT mats and fibers, utilizing traditional polymeric and more novel multi- functional dispersant materials. Thereby, providing a series of new framework for which future device structures can be fabricated.
2
Xi, Binbin. "Novel conducting polymer structures for electrochemical actuators." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060517.100903/index.html.
Full text
3
Li, Jing. "Electrical conducting polymer nanocomposites containing graphite nanoplatelets and carbon nanotubes /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?MECH%202006%20LI.
Full text
4
Keng, Yenmei. "The effects of temperature and carbon nanotubes on conducting polymer actuator performance." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61879.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 102-103).
Conducting polymers serve as electrically conductive actuators via ion diffusion in and out of the polymer when voltages are applied. Their actuation performance can be largely affected by deposition setup, post-deposition processing, type of electrolyte, applied voltage for actuation, and temperature. It was shown that increasing temperature caused higher active stress in polypyrrole, an attractive conducting polymer actuator material. However, detailed characterizations were lacking to determine whether the improved active stress was caused by structural change in the polymer and/or charging effect. A temperature-controlled solvent bath was integrated with a custom-built electrochemical dynamic mechanical analyzer to conduct isometric and isotonic tests on polypyrrole under elevated temperature. Experimental results showed that heating increased the charge transport through the polymer and thermal expansion in the polymer allowed more room for charge uptake. As a result, increase in ion movement largely contributed to improvements in actuation stress (rate) and strain (rate), while the decrease in stiffness due to heating had limited effect. Moreover, actuation performance was further improved by choosing large active ion type, BMIM. Although the active stress and strain increased via heating, creep limits the reversibility of conducting polymer actuators. To reduce creep rate, functionalized multi-walled carbon nanotubes (fCNTs) were introduced to fabricate composites with polypyrrole and with PEDOT. Out of four attempted fabrication techniques, drop-casted multilayer structure demonstrated that increasing the amount of fCNTs reduced creep rate, but also decreased active strain, stiffness, and conductivity. Applying higher preload (up to 3 MPa) improved active strain in the composites by providing more space for charge uptake. The amount of sCNTs that provided optimal performance was approximately 20-30% by weight.
by Yenmei (Kerri) Keng.
S.M.
5
Oh, Jungmin. "Preparation and application of conducting polymer-carbon nanotube composite." [Johnson City, Tenn. : East Tennessee State University], 2004. https://dc.etsu.edu/etd/960.
Full textAbstract:
Thesis (M.S.)--East Tennessee State University, 2004.Title from electronic submission form. ETSU ETD database URN: etd-1110104-211520 Includes bibliographical references. Also available via Internet at the UMI web site.
6
Chiguma, Jasper. "Conducting polymer nanocomposites loaded with nanotubes and fibers for electrical and thermal applications." Diss., Online access via UMI:, 2009.
Find full text
7
Wasem, Klein Felipe. "Photoactive polymer – carbon nanotubes hybrid nanostructures." Thesis, Strasbourg, 2021. http://www.theses.fr/2021STRAE004.
Full textAbstract:
L’objectif de cette thèse est la préparation de matériaux hybrides polymères conjugués (P3HT et un copolymère dérivé) - nanotubes de carbone, ainsi que leur caractérisation par des méthodes spectroscopiques et par microscopie électronique. Des nanohybrides non-covalents sont obtenus par la sonication des deux composants dans le THF. L’interaction entre ces composants entraîne l’enroulement du polymère autour des nanotubes ainsi que la formation d'agrégats de polymère sur leur surface. L’effet de différents paramètres, tels que la masse molaire du polymère, ont été étudiés. Des nanohybrides covalents sont obtenus en utilisant un copolymère portant une aniline au bout de la chaîne alkyle. Les spectroscopies optique et Raman suggèrent un faible taux de fonctionnalisation ainsi qu’une conformation plus désordonnée des chaînes de polymères par rapport aux nanohybrides non-covalents. Des études préliminaires montrent que le copolymère peut fonctionnaliser aussi des dispositifs à base de nanotubes de carbone. Le bas taux de fonctionnalisation ne permet pas de conclure sur la modification des propriétés électroniques, mais les défauts induits permettent l’observation d’un photocourantThe objective of this thesis is the preparation of conjugated polymers (P3HT and a derivated copolymer) – carbon nanotubes hybrid materials and their characterization through different spectroscopies and transmission electron microscopy. Non-covalent nanohybrids can be obtained by sonicating both components together in THF. The interaction between both components leads to the wrapping of the polymer around the carbon nanotubes as well as the formation of polymer aggregates on the surface of the nanotubes. The effect of different parameters such as the polymer chain length are described. Covalent nanohybrids can be obtained using a specially designed copolymer bearing an aniline at the end of its side chain. Optical and Raman spectroscopies indicate a low level of functionalization, and suggest that the polymer chains are in a more disordered state compared to non-covalent nanohybrids. Preliminary studies show that the obtained copolymer can be used for functionalizing carbon nanotube based devices. Modification of electrical properties of the devices were small and compatible with the low functionalization degree, but the induced defects allow observation of a photocurrent
8
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.
Full textAbstract:
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.
9
Vignal, Thomas. "Développement d’électrodes utilisant un PCE déposé sur VACNT/Al selon un procédé continu et leur utilisation dans des pseudosupercondensateurs." Thesis, Cergy-Pontoise, 2019. http://www.theses.fr/2019CERG1044.
Full textAbstract:
Les travaux réalisés ont porté sur l’élaboration d’électrodes composites à base de polymère conducteur électronique déposé électrochimiquement sur des tapis de nanotubes de carbone verticalement alignés sur substrat d’aluminium (VACNT/Al). Ces nouveaux tapis VACNT/Al ont une densité de nanotube très élevée (10^11 - 10^12 CNT/cm²) et proposent une architecture nanométrique très intéressante pour l’élaboration d’électrode dans des dispositifs de stockage d’énergie de type supercondensateur. Le dépôt de polymère sur ces électrodes permet d’augmenter l’énergie spécifique des supercondensateurs. De plus, ces travaux ont aussi été dédiés à l’élaboration d’un procédé de dépôt en continu en vue d’une montée en échelle des synthèses du composite. Dans une première partie, les matériaux utilisés dans les électrodes composites ont été caractérisés individuellement. Ainsi, des dépôts en milieu liquide ionique des polymères poly(3-méthylthiophène) (P3MT) et polypyrrole (PPy) à la surface d’électrodes planes ont été réalisés et, des tapis VACNT ont été caractérisés. La deuxième partie de ce travail a été consacrée à l’optimisation de la synthèse électrochimique par une méthode chronoampérométrique pulsée en milieu liquide ionique.de nanocomposites P3MT/VACNT/Al avec des proportions massiques de P3MT dans l’électrode variant de 10 à 90 %. Ces composites ont par la suite été utilisés en tant qu’électrodes dans des supercondensateurs symétrique et asymétrique sous forme de pile-bouton permettant des énergies et puissances spécifiques de 52 Wh/kg et 12 kW/kg, respectivement. Dans la troisième partie, un procédé de dépôts du P3MT sur un tapis en mouvement a été mis au point pour étudier l’élaboration en continu d’électrodes composites et permettre la préparation d’électrodes de plus grande dimension, 80 cm² dans cette étude. Ces composites ont montré des capacitances spécifiques équivalentes aux composites obtenus avec des dépôts statiques. De plus, les bandes de 80 cm2 ont été utilisées pour la réalisation de supercondensateurs de type zig-zag symétrique et asymétrique et ont aussi montré des énergies et puissance spécifiques très similaire à celles des piles bouton. Dans une dernière partie, un transfert de méthode a été réalisé pour la synthèse de composite PPy/VACNT, en statique puis en procédé continuThe work carried out focused on the development of composite electrodes by electrochemically deposition of conductive polymer onto carbon nanotube vertically aligned on aluminum substrate (VACNT/Al). These new VACNT / Al have a very high nanotube density (10^11 - 10^12 CNT/cm²) and offer a very interesting nanometric architecture for the elaboration of electrodes in energy storage devices as supercapacitor. The deposition of polymer on these electrodes allows the increase of the supercapacitors’ specific energies. In addition, this work has also been dedicated to the development of a continuous deposition process for scaling syntheses of the composite. In a first part, the materials used in the composite electrodes have been characterized individually. Thus, ionic liquid medium deposits of poly (3-methylthiophene) (P3MT) and polypyrrole (PPy) polymers at the surface of planar electrodes were made and VACNT were characterized. The second part of this work was devoted to the optimization of electrochemical synthesis by a pulsed chronoamperometric method in ionic liquid medium. P3MT/VACNT/Al nanocomposites with mass proportions of P3MT in the electrode ranging from 10 to 90%. These composites have subsequently been used as electrodes in symmetric and asymmetric supercapacitors in coin-cell devices allowing specifics energies and powers of 52 Wh/kg and 12 kW/kg, respectively. In the third part, a P3MT deposition process onto moving VACNT was developed to study the continuous elaboration of composite electrodes and to allow the preparation of larger electrodes, 80 cm² in this study. These composites showed specific capacitances equivalent to the composites obtained with static deposits. In addition, the 80 cm2 strips were used for the realization of symmetric and asymmetric zig-zag supercapacitors and also showed specific energies and power very similar to those of coin-cells. In a last part, a transfer of method was realized for the synthesis of composite PPy / VACNT, in static then continuous process
10
Lay, Makara. "Conductive nanopaper from cellulose nanofibers and conductive polymers and/or carbon nanotubes." Doctoral thesis, Universitat de Girona, 2017. http://hdl.handle.net/10803/401711.
Full textAbstract:
Coming from renewable and sustainable raw materials, nanocelluloses are rapidly emerging as one of the most promising future materials. Recently, the use of nanocellulose nanocomposites in flexible electrodes, biosensors or supercapacitors it is been studied.
The main objective of this thesis is to produce conductive nanopapers from cellulose nanofibers (CNF) or bacterial cellulose (BC) and tree different conductive materials: polypyrrole (PPy), poly(3,4-ethylenedioxythiophene : polystyrene sulfonate (PEDOT:PSS) and multi-walled carbon nanotubes (MWCNT).
The structure and morphology of nanocomposites were studied, as well as their thermal, mechanical, and electrical conductivity properties. The results revealed the semiconductor or conductor character of the obtained nanocomposites, with specific capacitances up to 300 F g-1 for CNF-PPy and CNF-PEDOT:PSS-PPy nanocomposites. This work demonstrates the feasibility of using cellulose nanofibers in the field of green and flexible electronics, biosensors, and energy storage devicesLes nanofibres de cel·lulosa són un dels materials del futur, gràcies al seu origen natural i renovable, i per les seves propietats físico-químiques, i mecàniques. Recentment, s’està estudiant el seu ús en elèctrodes flexibles, biosensors o supercapacitants. L’objectiu central de la tesis és produir nanopapers conductors a partir de nanofibres de cel·lulosa (CNF) o de cel·lulosa bacteriana (BC), i tres tipus de càrrega conductora, el polipirrol (PPy), el poli(3-4-etilendioxitiofè):poliestirè sulfonat (POEDOT:PSS) i els nanotubs de carboni de paret múltiple (MWCNT). S’ha avaluat l’estructura i morfologia dels materials nanocompòsits, així com les seves propietats tèrmiques, mecàniques i elèctriques. Els resultats mostren el caràcter semiconductor o conductor dels nanocompòsits obtinguts, amb capacitàncies específiques de més de 300 F·g-1 per als nanocompòsits de CNF-PPy i CNF-PEDOT:PSS-PPy. Es demostra la viabilitat de l’ús de nanofibres de cel·lulosa per la fabricació de productes electrònics flexibles, biosensors, o com a dispositius d’emmagatzematge d’energia
11
Hughes, M. "Composites of carbon nanotubes and conducting polymers." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604735.
Full textAbstract:
Carbon nanotubes and conducting polymers are both interesting for their unique electrochemical properties that make them well suited to use in electrochemical capacitors (sources of high power pulses of electrical energy) and actuators (artificial muscles). In the case of carbon nanotube films, it is their high surface area and electrical conductivity that makes them attractive, particularly in terms of their fast response times. In contrast, the redox chemistry of conducting polymers enables them to achieve large charge storage capacities and dimensional changes in response to potential cycling (often several orders of magnitude larger than those of carbon nanotubes). This thesis reports on the structure and electrochemical properties of composites of multi-walled nanotubes and conducting polymers (polypyrrole and poly(3-methylthiophene)) in addition to their performance in electrochemical capacitors and actuators. The composite film growth conditions were manipulated so as to merge the desirable properties of multi-walled nanotubes with those of conducting polymers. The results composite films were capable of charge storage capacitances, response times and cycle lives superior to those of pre conducting polymer films produced and tested using similar conditions. The alignment, concentration, production route, dimensions and chemical treatment of the carbon nanotubes were all found to play an important role in determining the nanostructure, doping and electrochemical behaviour of the composite films produced. The electrochemical capacitors tested illustrated the power and energy gains that are possible when using carbon nanotube-conducting polymer composite films. Composite film actuators made from multi-walled nanotubes and polypyrrole demonstrated the importance of orienting the nanotubes perpendicular to the desired direction of actuation in order to improve actuation kinetics (through increased electrical conductivity) without constraining actuation of the conducting polymer.
12
Bethani, Aikaterini. "Synthèse de copolymères de type polymère semi-conducteur-bloc-polymère hydrosoluble : application à la dispersion de nanotubes de carbone." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14707/document.
Full textAbstract:
Cette thèse porte pour l'essentiel sur la synthèse de copolymères à blocs bien définis composés au moins d'un bloc polymère semi-conducteur et d'un segment hydrosoluble pour être utilisés comme agents dispersants de nanotubes de carbone (NTCs) dans des milieux aqueux. Des copolymères de différentes masses molaires ont été synthétisés en suivant des procédés de polymérisation sans métaux et l’influence de la fraction volumique de la partie hydrosoluble a été étudiée au regard de leur solubilité en milieux aqueux. La capacité de ces copolymères à s'organiser ou s'auto-assembler tant en solution qu'en film a été examinée. Enfin, des dispersions de NTCs avec ces copolymères ainsi que leurs films obtenus par différents types de dépôts ont été réalisés et caractérisés pour déterminer notamment leurs caractéristiques électro-optiquesOur work focused on the synthesis of well-defined copolymers constituted with at least a conductive polymer segment along with hydrophilic moieties in order to disperse CNTs in aqueous media. Using metal free polymerizations, copolymers with different molecular weights were synthesized in order to study the influence of the hydrophilic part on these materials. Besides the self-assembly behavior of these copolymers, both in bulk and in solution, were addressed. This type of copolymers were successfully used to disperse both single and multi wall carbon nanotubes. Electrical and optical characteristics of the dispersions together with their films will also be discussed
13
Kim, Yong Hyun. "Alternative Electrodes for Organic Optoelectronic Devices." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-113279.
Full textAbstract:
This work demonstrates an approach to develop low-cost, semi-transparent, long-term stable, and efficient organic photovoltaic (OPV) cells and organic light-emitting diodes (OLEDs) using various alternative electrodes such as conductive polymers, doped ZnO, and carbon nanotubes. Such electrodes are regarded as good candidates to replace the conventional indium tin oxide (ITO) electrode, which is expensive, brittle, and limiting the manufacturing of low-cost, flexible organic devices. First, we report long-term stable, efficient ITO-free OPV cells and transparent OLEDs based on poly(3,4-ethylene-dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) electrodes by using a solvent post-treatment or a structure optimization. In addition, a high performance internal light out-coupling system for white OLEDs based on PEDOT:PSS-coated metal oxide nanostructures is developed. Next, we demonstrate highly efficient ITO-free OPV cells and OLEDs with optimized ZnO electrodes doped with alternative non-metallic elements. The organic devices based on the optimized ZnO electrodes show significantly improved efficiencies compared to devices with standard ITO. Finally, we report semi-transparent OPV cells with free-standing carbon nanotube sheets as transparent top electrodes. The resulting OPV cells exhibit very low leakage currents with good long-term stability. In addition, the combination of various kinds of bottom and top electrodes for semi-transparent and ITO-free OPV cells is investigated. These results demonstrate that alternative electrodes-based OPV cells and OLEDs have a promising future for practical applications in efficient, low-cost, flexible and semi-transparent device manufacturingDie vorliegende Arbeit demonstriert einen Ansatz zur Verwirklichung von kostengünstigen, semi-transparenten, langzeitstabilen und effizienten Organischen Photovoltaik Zellen (OPV) und Organischen Leuchtdioden (OLEDs) durch die Nutzung innovativer Elektrodensysteme. Dazu werden leitfähige Polymere, dotiertes ZnO und Kohlenstoff-Nanoröhrchen eingesetzt. Diese alternativen Elektrodensysteme sind vielversprechende Kandidaten, um das konventionell genutzte Indium-Zinn-Oxid (ITO), welches aufgrund seines hohen Preises und spröden Materialverhaltens einen stark begrenz Faktor bei der Herstellung von kostengünstigen, flexiblen, organischen Bauelementen darstellt, zu ersetzten. Zunächst werden langzeitstabile, effiziente, ITO-freie Solarzellen und transparente OLEDs auf der Basis von Poly(3,4-ethylene-dioxythiophene):Poly(styrenesulfonate) (PEDOT:PSS) Elektroden beschrieben, welche mit Hilfe einer Lösungsmittel-Nachprozessierung und einer Optimierung der Bauelementstruktur hergestellt wurden. Zusätzlich wurde ein leistungsfähiges, internes Lichtauskopplungs-System für weiße OLEDs, basierend auf PEDOT:PSS-beschichteten Metalloxid-Nanostrukturen, entwickelt. Weiterhin werden hoch effiziente, ITO-freie OPV Zellen und OLEDs vorgestellt, bei denen mit verschiedenen nicht-metallischen Elementen dotierte ZnO Elektroden zur Anwendung kamen. Die optimierten ZnO Elektroden bieten im Vergleich zu unserem Laborstandard ITO eine signifikant verbesserte Effizienz. Abschließend werden semi-transparente OPV Zellen mit freistehenden Kohlenstoff-Nanoröhrchen als transparente Top-Elektrode vorgestellt. Die daraus resultierenden Zellen zeigen sehr niedrige Leckströme und eine zufriedenstellende Stabilität. In diesem Zusammenhang wurde auch verschiedene Kombinationen von Elektrodenmaterialen als Top- und Bottom-Elektrode für semi-transparente, ITO-freie OPV Zellen untersucht. Zusammengefasst bestätigen die Resultate, dass OPV und OLEDs basierend auf alternativen Elektroden vielversprechende Eigenschaften für die praktische Anwendung in der Herstellung von effizienten, kostengünstigen, flexiblen und semi-transparenten Bauelement besitzen
14
Peng, Chuang. "Electrochemical synthesis of composites of conducting polymers and carbon nanotubes for supercapacitors." Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486715.
Full textAbstract:
The power units in modem electric vehicles are required to store large amount of energy and to provide a high power. Supercapacitors being able to export a pulsed high power can be used in combination with batteries or fuel cell to meet the energy and power demand of electric vehicles. Carbon nanotubes with high surface area and conducting polymers with large pseudocapacitance are both powerful candidates for supercapacitors. This thesis describes a novel electrochemical route for synthesis of composites of conducting polymer and nanotubes via co-deposition from solutions containing ionic CNTs and monomers. The resulting deposits exhibited a unique porous network structure composed of individual nanotubes coated with a layer of conducting polymers. Carbon nanotubes served as charge carriers during the polymerisation and also acted as both a strong backbone and effective dopant within the composite materials. Therefore, the composites have improved mechanical integrity and an open structure that facilitates ion and solvent motion during the electrochemical processes. Moreover, the large immobile CNT anions exert an electrostatic repulsion to the electrons on the polymer chain. This repulsion makes it easier to remove electrons from the polymer chains. As a result, the composites showed good conductivity and capacitive properties even at negative potentials. A systematic study on the charge storage properties of the composites has been carried out using various electrochemical methods, including CV, AC impedance spectroscopy, chronocoulometry, chronoamperometry and chronopotentiometry. FTIR and XPS have been used to study the interaction between CNTs and conducting polymers. Prototype supercapacitors were built with the composites as electrode material. Both symmetric and asymmetric prototypes showed ideal capacitive behaviour, indicating a good potential for application in supercapacitors using the novel composite materials.
15
Yesil, Sertan. "Processing And Characterization Of Carbon Nanotube Based Conductive Polymer Composites." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611984/index.pdf.
Full textAbstract:
The aim of this study was to improve the mechanical and electrical properties of conductive polymer composites. For this purpose, different studies were performed in this dissertation. In order to investigate the effects of the carbon nanotube (CNT) surface treatment on the morphology, electrical and mechanical properties of the composites, poly(ethylene terephthalate) (PET) based conductive polymer composites were prepared by using as-received, purified and modified carbon nanotubes in a twin screw extruder.
During the purification of carbon nanotubes, surface properties of carbon nanotubes were altered by purifying them with nitric acid (HNO3), sulfuric acid (H2SO4), ammonium hydroxide (NH4OH) and hydrogen peroxide (H2O2) mixtures. Electron Spectroscopy for Chemical Analysis (ESCA) results indicated the removal of metallic catalyst residues from the structure of carbon nanotubes and increase in the oxygen content of carbon nanotube surface as a result of purification procedure. Surface structure of the purified carbon nanotubes was also modified by treatment with sodium dodecyl sulfate (SDS), poly(ethylene glycol) (PEG) and diglycidyl ether of Bisphenol A (DGEBA). Fourier Transformed Infrared Spectroscopy (FTIR) spectra of the carbon nanotube samples indicated the existence of functional groups on the surfaces of carbon nanotubes after modification. All composites prepared with purified and modified carbon nanotubes had higher electrical resistivities, tensile and impact strength values than those of the composite based on as-received carbon nanotubes, due to the functional groups formed on the surfaces of carbon nanotubes during surface treatment.
In order to investigate the effects of alternative composite preparation methods on the electrical and mechanical properties of the composites, in-situ microfiber reinforced conductive polymer composites consisting of high density polyethylene (HDPE), poly(ethylene terephthalate) and carbon nanotubes were prepared in a twin screw extruder followed by hot stretching of PET/CNT phase in HDPE matrix. Composites were produced by using as-received, purified and PEG treated carbon nanotubes. SEM micrographs of the hot stretched composites pointed out the existence of in-situ PET/CNT microfibers dispersed in HDPE matrix up to 1 wt. % carbon nanotube loadings. Electrical conductivity values of the microfibrillar composites were higher than that of the composites prepared without microfiber reinforcement due to the presence of continuous PET/CNT microfibers with high electrical conductivity in the structure.
To investigate the potential application of conductive polymer composites, the effects of surfactant usage and carbon nanotube surface modificationon the damage sensing capability of the epoxy/carbon nanotube/glass fiber composite panels during mechanical loadings were studied. Surface modification of the carbon nanotubes was performed by using hexamethylene diamine (HMDA). 4-octylphenol polyethoxylate (nonionic) (Triton X-100) and cetyl pyridinium chloride (cationic) (CPC) were used as surfactants during composite preparation. Electrical resistivity measurements which were performed during the impact, tensile and fatigue tests of the composite panels showed the changes in damage sensing capabilities of the composites. Surface treatment of carbon nanotubes and the use of surfactants decreased the carbon nanotube particle size and improved the dispersion in the composites which increased the damage sensitivity of the panels.
16
Mottaghitalab, Vahid. "Development and characterisation of polyaniline-carbon nanotube conducting composite fibres." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060731.095628/index.html.
Full text
17
Bajpai, Vardhan. "SYNTHESES, CHARACTERIZATION AND APPLICATIONS OF MICRO-/NANO-STRUCTURED CONDUCTING POLYMERS AND CARBON NANOTUBES." University of Akron / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=akron1131983430.
Full text
18
Valente, Gustavo Monteiro da Silva. "Celula solar organica de heterojunção de poli[2-metoxi-5-[(3,7-dimetiloctoxi) fenileno vinileno]] e nanotubos de carbono." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/261959.
Full textAbstract:
Orientadores: Vitor Baranauskas, Ana Flavia NogueiraDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
Made available in DSpace on 2018-08-12T11:11:13Z (GMT). No. of bitstreams: 1 Valente_GustavoMonteirodaSilva_M.pdf: 2272217 bytes, checksum: c82b3f59d489a35f76f4e4d2a2263828 (MD5) Previous issue date: 2008
Resumo: Novas fontes de energia limpa de baixo custo devem ser obtidas nas próximas décadas para sustentar o consumo de energia mundial e manter o meio-ambiente livre de gases de efeito estufa. Enquanto células solares inorgânicas são uma fonte limpa de energia, essa tecnologia é restrita devido a seu alto custo de produção. Células solares orgânicas têm sido desenvolvidas para solucionar este problema, pelo menos para dispositivos pequenos, isto é, para aplicações de baixa corrente. Recentemente novos materiais tal como polímeros condutores e nanotubos de carbono vêm sendo utilizados em células solares orgânica de heterojunção. Uma célula solar eficiente deve absorver toda (ou boa parte) da luz solar e gerar e transportar portadores de carga livre para seus eletrodos para assim produzir corrente elétrica e um potencial interno. Neste trabalho usamos o polímero poli[2-methoxy-5-[(3,7-dimethyloctyloxy) phenylene vinylene] (MDMO-PPV) como material absorvedor e transportador de buracos e nanotubos de carbono para dissociação do exciton e tranporte de elétrons. A morfologia e foto-fisica das células, bem como a caracterização do dispositivo é estudada.
Abstract: New sources of low cost and clean energy must be achieved in the coming decades to sustain world consumption while also keeping the environment free of green house gases. While inorganic solar cells are a source of clean energy, they are plagued by high production costs. Organic solar cells have been developed as a solution to this problem as a means to harvest light while keeping production costs low. Recently, new materials such as conductive polymers, carbon nanotubes (CNT) and fullerenes have been utilized in bulk heterojunction organic solar cells1,2. Increasing the effi-ciency of these organic solar cells is crucial for them to become economically viable. An efficient solar cell must harvest all the possible light from the Sun and produce and transport free charges carriers to their electrodes to produce electrical current with a built-in potential. In this work we use a poly[2-methoxy-5-[(3,7-dimethyloctyloxy) phenylene vinylene] (MDMO-PPV) as the absorption and hole transport material and CNT for exciton dissociation and electron transport. The morphology and photophysics of the films, as well as the characteristic J-V curves for the devices were obtained.
Mestrado
Eletrônica, Microeletrônica e Optoeletrônica
Mestre em Engenharia Elétrica
19
Tiwari, Ashutosh, Yashpal Sharma, Shinya Hattori, Dohiko Terada, Ashok K. Sharma, Anthony P. F. Turner, and Hisatoshi Kobayashi. "Influence of poly(N-isopropylacrylamide)-CNT-polyaniline three-dimensional electrospun microfabric scaffolds on cell growth and viability." Linköpings universitet, Biosensorer och bioelektronik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-85583.
Full textAbstract:
This study investigates the effect on: 1) the bulk surface; and 2) the three-dimensional non-woven microfabric scaffolds of poly(N-isopropylacylamide)-CNT-polyaniline on growth and viability of mice fibroblast cells L929. The poly(N-isopropylacylamide)-CNT-polyaniline was prepared using coupling chemistry and electrospinning was then used for the fabrication of responsive, nonwoven microfabric scaffolds. The electrospun microfabrics were assembled in regular three-dimensional scaffolds with OD: 400-500 mm; L: 6-20 cm. Mice fibroblast cells L929 were seeded on the both poly(N-isopropylacylamide)-CNT-polyaniline bulk surface as well as non-woven microfabric scaffolds. Excellent cell proliferation and viability was observed on poly(N-isopropylacylamide)-CNT-polyaniline non-woven microfabric matrices in compare to poly(N-isopropylacylamide)-CNT-polyaniline bulk and commercially available Matrigel™ even with a range of cell lines up to 168 h. Temperature dependent cells detachment behaviour was observed on the poly(N-isopropylacylamide)-CNT-polyaniline scaffolds by varying incubation at below lower critical solution temperature (LCST) of poly(N-isopropylacylamide). The results suggest that poly(N-isopropylacylamide)-CNT-polyaniline non-woven microfabrics could be used as a smart matrices for applications in tissue engineering.European Commission FP7 (PIIF-GA-2009-254955), JSPS, JST-CREST and MEXT
20
CARADONNA, ANDREA. "Carbon-based polymer nanocomposites with enhanced conductive properties." Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2703852.
Full textAbstract:
Nowadays the development of new technologies requires materials with unconventional combination of properties. Polymers are classified as electrical and thermal insulating materials, which limits their use for several important technological applications. However, conductive polymers could be used in order to overcame drawbacks in the use of metals, metal alloys and ceramic materials as conductive media. Thermal conductive polymers could be profitably exploited in heat management applications (e.g. heat sink, heat exchangers), while electrical conductive polymers could be used in different fields depending on their electrical conductive values. To enhance the conductive properties of polymers, several approaches has been reported in literature. However, the most established way to achieve this goal consists in the development of suitable composite materials by means of the incorporation of conductive fillers within the polymeric matrix. The choice of the conductive filler is a crucial point in the development of the final material. Due to their extremely high thermal and electrical conductivity, coupled with the low density, the nano-metric scale and the outstanding mechanical properties, carbon-based nanomaterials are the most promising fillers suitable for processing conductive polymers. Since graphene nanoplatelets (GNPs) are considered young materials with potentials not yet fully exploited, multiwall carbon nanotubes (MWCNTs) are nowadays the most established materials used as conductive filler.
In this thesis work thermally and electrically conductive polymer composites, filled with carbon-based nanomaterials were investigated.
In the first part of the experimental work, particular attention was devoted to the development of GNPs-based thermally conductive polymers. By properly selecting several polymeric matrices and comparing several available processing techniques it was possible to outline a guideline in the use of GNPs as thermally conductive fillers. A strong filler characterization reveals that, in spite to the amount of defects and to the filler purity, the main GNPs properties able to enhance the thermal conductivity of polymers is the lateral dimension.
With the aim of developing metal-free circuits integrated in nanocomposite, a laser printing process was successfully exploited in order to obtain electrical conductive paths on the surface of a polymeric materials containing MWCNTs. Starting from the literature knowhow and new experimental results, a complete comprehension of the parameters that affect the laser printing process was achieved by applying a statistical approach. By analysing the experimental outcomes with a statistical approach, it was possible to focus the attention on the main laser parameters that govern the process, thus obtaining multifunctional and multidirectional conductive materials with surface electrical resistance per unit length (inside the tracks) lower than 1 kΩ/cm at 0.5 wt.% of MWCNTs loading content.
Finally, by combining outcomes obtained as described above, hybrid carbon-based nanocomposites were developed, with the purpose of enhancing contemporaneously thermal and electrical conductivity. Hybrid materials, obtained starting from a commercial masterbatch containing MWCNTs, demonstrated the possibility to partially replace the high amounts of carbon nanotubes with low cost carbon based materials without worsening the good conductive properties.
Not only conductive properties were investigated, but all the studied materials were also characterized by means of mechanical and thermal stability tests, thus demonstrating the possibility of adopting carbon-based polymer nanocomposites as multifunctional materials.
21
Soroudi, Azadeh. "Melt Spun Electro-Conductive Polymer Composite Fibers." Doctoral thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-3590.
Full textAbstract:
One interesting approach is the development of conductive polymer composite fibers for innovative textile applications such as in sensors, actuators and electrostatic discharge. In this study, conductive polymer composite fibers were prepared using several different blends containing conductive components: a conjugated polymer (polyaniline-complex) and/or carbon nanotubes. Different factors such as processing parameters, the morphology of the initial blends and the final fibers, fiber draw ratio and material selection were studied separately to characterize their effects on the fiber properties. In binary blends of PP/polyaniline-complex, the processing conditions, the matrix viscosity and the fiber draw ratio had substantial effects on the electrical conductivity of the fibers and linearity of resistance-voltage dependence. These factors were associated with each other to create conductive pathways through maintaining an appropriate balance of fibril formation and breakage along the fiber. The blend morphology was defined as the initial size of the dispersed conductive phase (polyaniline-phase), which depended on the melt blending conditions as well as the PP matrix viscosity. Depending on the initial droplet phase size, an optimum draw ratio was necessary to obtain maximum conductivity by promoting fibril formation (sufficient stress) and preventing fibril breakage (no excess stress) to create continuous pathways of conductive phase. Ternary blend fibers of PP/PA6/polyaniline-complex illustrated at least three-phase morphology with matrix/core-shell dispersed phase style. When ternary fibers were compared to binary fibers, the former could combine better mechanical and electrical properties only at a specific draw ratio; this showed that draw ratio was a more determinant factor for the ternary fibers, as both conductivity and tensile strength depended on the formation of fibrils from the core-shell droplets of the PA6/polyaniline-complex through the polypropylene matrix. The achieved maximum conductivity so far was in the range of 10 S/cm to 10 S/cm, which for different samples were observed at different fiber draw ratios depending on the mixing conditions, the matrix viscosity or whether the fiber was a binary or ternary blend. To improve the properties, PP/polyaniline-complex blends were filled with CNTs. The CNTs and the polyaniline-complex both had an increasing effect on the crystallization temperature and the thermal stability of PP. Furthermore, the maximum conductivity was observed in samples containing both CNTs and polyaniline-complex rather than the PP with either one of the fillers. Although increasing the content of CNTs improved the conductivity in PP/CNT fibers, the ease of melt spinning, diameter uniformity and mechanical properties of fibers were adversely affected. Diameter variation of PP/CNT as-spun fibers was shown to be an indication of hidden melt-drawings that had occurred during the fiber extrusion; this could lead to variations in morphology such as increases in the insulating microcracks and the distance between the conductive agglomerates in the drawn parts of the fiber. Variations in morphology result in variations in the electrical conductivity; consequently, the conductivity of such inhomogeneous fiber is no longer its physical property, as this varies with varying size.Thesis to be defended in public on Friday, May 20, 2011 at 10.00 at KC-salen, Kemigården 4, Göteborg, for the degree of Doctor of Philosophy.
22
Li, Yilong. "Vapor sensing behavior of sensor materials based on conductive polymer nanocomposites." Technische Universität Dresden, 2019. https://tud.qucosa.de/id/qucosa%3A38069.
Full textAbstract:
This work aims to investigate the vapor sensing behavior of conductive polymer composites (CPCs). In connection with the protection of the environment and human beings, sensing of different kinds of chemical vapors is of increasing importance. At the moment, four kinds of vapor sensors are widely investigated and reported, namely semiconducting metal oxide sensors (MO), conjugated polymer sensors, carbonaceous nanomaterial based sensors, and CPC based sensors. Due to their unique component systems, the different sensor types are based on different sensing mechanisms resulting in different potential application ranges.
In consideration of cost and processability, CPC based vapor sensors are promising owning to their low cost, excellent processability, and designable compositions. In terms of vapor sensing behavior of CPC sensors, the interaction between the polymer and the organic vapor is a decisive factor in determining the sensing performance of CPCs. Ideally, the chosen polymer matrix should be able to swell without dissolving during vapor exposure so that the conductive network within the matrix can be disconnected, giving rise to the resistance change of CPCs. In some reported cases, polymers such as PLA and polycaprolactone (PCL) are degradable polymers, which are not durable when being exposed to environmental conditions for a long time. Therefore, it is necessary to make sure whether the selected polymers are resistive to vapors or not. There are two options for the polymer selection. One is to select a polymer that is only swellable in a specific or few organic solvents; another one is to select a polymer that is swellable to a variety of solvents. Since CPC sensors are used for detecting as many as possible hazardous chemicals to human beings or environment, the second case is more desired because of its broader window of detection. The solubility parameter is effective to characterize the interaction of polymers and organic solvents/vapors, which was firstly proposed by Charles Hansen. Initially, the Hansen solubility parameter (HSP) was used to predict the compatibility between polymer partners, chemical resistance, permeation rates, and even to characterize the surface of fillers. Liquids with similar solubility parameter (δ) are miscible, and polymers will dissolve in solvents whose δ is similar to their own value. This behavior is recognized as “like dissolves like”. Based on the description above, CPCs that can be used as liquid/vapor sensor materials should meet the following two requirements: 1) the chosen polymer should be swellable to vapors; 2) the CPCs as sensor materials have to be electrically conductive. Therefore, the relationship between conductive network and vapor sensing behavior of CPCs was investigated from the following aspects:
1) According to the previous studies, CB/polymer composites exhibit poor reversibility in cyclic vapor sensing tests because of the susceptible conductive network formed by CB particles. Thus, there is a need to improve the reversibility and increase the relative resistance change (Rrel) of CPCs. MWCNTs, as 1-dimensional carbon fillers with high aspect ratio, have excellent electrical and mechanical properties. Therefore, a hybrid filler system (MWCNT and CB) was utilized and incorporated in polycarbonate (PC) via melt compounding. PC was selected as the polymer matrix of CPCs because it showed high affinity with many commercial organic solvents/vapors as well as high and fast volume change upon organic solvents/vapors. In order to discuss the effect of conductive network formation on the vapor sensing behavior of PC/MWCNT/CB composites, two MWCNT contents were selected, which were lower and higher than the electrical percolation threshold of the PC/MWCNT composites. In the following, three CB contents were selected for the mixtures with MWCNT. The conductive networks composed of either MWCNT or hybrid CB/MWCNT are compared. The morphology of CPCs with different hybrid filler ratios was observed and investigated using SEM and OM. Moreover, to quantify the vapor sensing behavior of CPCs, some organic solvents were chosen and characterized by Flory-Huggins interaction parameter to demonstrate the polymer-vapor interaction. Afterwards, the cyclic vapor sensing was applied to illustrate the vapor sensing behavior of CPCs with different conductive network formations.
2) At moment, the filler dispersion is still a big challenge for MWCNT filled polymer composites due to the fact that the strong Van der Waals force among nanotubes makes them easily to entangle with each other resulting in the formation of agglomerates. A good filler dispersion state is desirable to achieve CPCs with low φc and. In order to reduce the φc of CPCs, immiscible polymer blend systems are introduced, which can have different blend microstructures by adjusting the polymer component ratios. In the second section, an immiscible polymer blend system based on two amorphous component, namely PC and polystyrene (PS), was chosen aiming to explain the influence of the blend morphology on the sensing performance of CPCs. PC/PS blends with different compositions filled with MWCNT were fabricated by melt mixing. The selective localization of MWCNTs in the blends was predicted using the Young’s equation. Moreover, the composite morphology, filler dispersion, and distribution were characterized by SEM and TEM. In the following, three kinds of CPCs ranging from sea-island structure to co-continuous structure were selected for the cyclic sensing measurement. The relationship between composite microstructure and resulting vapor sensing behavior was evaluated and discussed.
3) The poor reversibility of CPCs towards good solvent vapors is still a problem that hinders the cyclic use of CPC sensor materials. As an important class of polymer, crystalline polymers are rigid and less affected by solvent penetration because of the well-arranged polymer chains. Therefore, the effect of polymer crystallinity on the vapor sensing behavior of CPCs is imperative to be studied. In the third section, poly(lactic acid) (PLA), a semi-crystalline polymer, was selected to melt-mixed with PS and MWCNTs with the aim to improve the sensing reversibility of CPCs towards organic vapors, especially good solvent vapors. Thermal annealing was utilized to tune the PLA crystallinity and the polymer blend microstructure of CPCs. The electrical, morphological, and thermal behavior of CPCs after different thermal annealing times is discussed. In the following, the effect of crystallinity on the vapor sensing behavior of the CPCs was studied in detail. Besides, the different sensing performances of the CPCs towards different vapors resulted from the selective localization of MWCNTs and increased polymer matrix crystallinity were investigated and compared.
4) As discussed for the amorphous polymer blends and crystalline polymer blends and their vapor sensing behavior. The comparison of compact and porous structure of CPCs is going to be studied. In the fourth section, studies to further improve the sensing performance and to find out the exact sensing mechanism of CPCs were performed. Therefore, poly(vinylidene fluoride) (PVDF), a solvent resistive polymer, was chosen to be melt-mixed with PC and MWCNTs. In order to compare the MWCNT dispersion and localization in the blends, three kinds of PCs with different molecular weights were selected; hence, the viscosity ratio of immiscible blends was varied. Rheological, morphological, and electrical properties of CPCs were characterized. After that, the cyclic sensing and long-term immersion tests of CPCs towards different vapors were carried out to evaluate the vapor sensing behavior of compact CPCs with different blend viscosity ratios. Moreover, porous CPC sensors were prepared by extracting the PC component. The same sensing protocols were also applied to these porous sensor materials. The sensing mechanisms between compact CPC sensor and porous CPC sensor were compared and investigated.
23
Combessis, Anthony. "Appport des nanotubes de carbone à la conduction électrique de matériaux organiques." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENI062.
Full textAbstract:
Ce travail de thèse propose, par une approche multi-échelles, une compréhension de certains mécanismes de constitution des réseaux percolants de nanotubes de carbone initialement dispersés au sein de polymères thermoplastiques. L'impact du phénomène de « percolation dynamique » sur les propriétés électriques d.c. et a.c. des nanocomposites a ainsi été étudié par l'établissement d'inter-relations entre l'organisation des charges et les propriétés résultantes. L'effet de cette auto-organisation des systèmes sur les paramètres critiques d.c. de la loi de percolation statistique sont discutés. Des origines à la percolation dynamique sont proposées et permettent d'envisager de nombreuses applications industrielles. A titre d'exemple, le contrôle sur plusieurs ordres de grandeur de la permittivité et de la conductivité est proposé, certaines valeurs n'étant pas accessibles avec les méthodes conventionnellesThe present thesis proposes a multi-scale understanding of some mechanisms that govern the genesis of percolating networks constituted with carbon nanotubes in thermoplastic polymers. The effect of "dynamic percolation" on the d.c. and a.c. electrical properties of the resulting nanocomposites was studied by means of the identification of the relationships between the filler organization and the use properties. The consequences of this controlled self-organization on the statistic percolation law d.c. critical parameters are discussed. Two possible origins of the dynamic percolation are proposed. From an applicative point of view, thermal treatments were applied to design new materials. The range of accessible permittivity and conductivity values is also discussed
24
Taubert, Clinton J. "Low Percolation Threshold in Electrically Conductive Adhesives using Complex Dimensional Fillers." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1542727822099192.
Full text
25
Kumar, Bijandra. "Development of smart textiles with low environmental footprint from Conductive polymer nanoComposites." Lorient, 2010. http://www.theses.fr/2010LORIS195.
Full textAbstract:
Ce travail concerne le développement de textiles multifonctionnels innovants basés sur les composites polymères conducteurs (CPC), travail réalisé dans le cadre du projet européen intitulé « INTELTEX ». Des nanotubes de carbones multi-parois ont été utilisés pour leurs excellentes propriétés électriques afin de créer un réseau de charges conductrices au sein de matrices thermoplastiques synthétiques mais également bio-sourcées. La détection de composés organiques volatiles (COV) par ces systèmes sous forme de film mince exposé à des vapeurs de solvants a été démontrée. De nouvelles stratégies sont présentées pour développer et contrôler l’architecture multi-échelles du réseau conducteur. Les capteurs ainsi développés sont capables de détecter et de discriminer différentes vapeurs de solvants. Ces résultats ont ensuite aboutis à la réalisation d’échantillons textiles mono- et bi-phasiques capables de répondre à la présence de vapeurs. Enfin des systèmes di-phasiques textiles, basés sur le principe de double-percolation ont été préparés. Ces composites présentent une transition nette (PTC) dans la gamme de température visée (30-60°C). Pour les deux applications (vapeur et température) des formulations à base de matrices diminuant l’impact environnemental ont été proposées. Pour conclure, les composites polymères conducteurs (CPC) basés sur les nanotubes de carbones ont prouvés leur potentiel et intérêt d’utilisation comme matériaux intelligents sous forme de textile pour la détection de vapeurs et de températureThis research work concerns the investigation and development of innovative eco-friendly smart multi-reactive textiles made of Conductive Polymer nanoComposite (CPC) within the frame of the European Union Commission funded project entitled “INTELTEX”. Multiwalled Carbon Nanotubes (CNT) have been used as conductive nanofiller to create conductive networks within both synthetic and bio-sourced polymer matrices. The ability of CPC thin films based sensor to detect Volatile Organic Compound (VOC) has been investigated by exposing them to a wide set of solvent vapours. Novel strategies have been introduced to fabricate vapour sensor with controlled hierarchical condictive architecture. The sensors developed were found to have a high potential to detect as well as to discriminate the studied vapours. In a second part the knowledge developed with CPC thin film was transferred to both mono-phasic and bi-phasic conductive textiles, which were demonstrated to be sensitive to vapours and temperature. In particular novel bi-phasic CPC textiles structured using double percolation were found to exhibit a sharp positive temperature coefficient (PTC) characteristic in the range 30 - 60°C. In the last part it has been shown that eco-friendly matrices could be proposed in substitution of synthetic polymers to decrease their environmental footprint. Finally, it has been demonstrated that CNT based CPC had a high potential as smart material to develop multi-reactive smart textile for vapour and temperature sensing
26
Otto, Christian [Verfasser], and Volker [Akademischer Betreuer] Abetz. "Electrically Conductive Composite Materials from Carbon Nanotube Decorated Polymer Powder Particles / Christian Otto ; Betreuer: Volker Abetz." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2017. http://d-nb.info/1150183748/34.
Full text
27
Lu, Jianbo. "Development of intelligent textiles from conductive polymer composites (CPC) for vapour and temperature sensing." Lorient, 2009. http://www.theses.fr/2009LORIS149.
Full text
28
Nag, Chowdhury Suvam. "Conductive Polymer nanoComposite Quantum Resistive strain Sensors for structural composites damage monitoring." Thesis, Lorient, 2014. http://www.theses.fr/2014LORIS343.
Full textAbstract:
Un nouveau type de Senseur de déformation Résistif Quantique (QRS) à base de nanotubes de carbone (CNT) a été développé pour le suivi de santé de structures composites (SHM). Les senseurs ont été fabriqués directement par pulvérisation en couche par couche (sLBL) sur la surface de fibres de verre ou de carbone d'une formulation de nanoComposites Polymères Conducteurs (CPC). La réponse des transducteurs CPC a été étudiée sous diverses sollicitations mécaniques en mode statique et dynamique. Différentes stratégies de suivi de santé des composites à l'aide de senseurs piézo-résistifs ont été comparées en termes d'efficacité de suivi des sollicitations mécaniques dans les domaines élastique et plastique et des endommagements. Les résultats montrent que les réponses des senseurs conservent toutes les caractéristiques statiques et dynamiques d'entrée fournissant ainsi des informations utiles pour le SHM. Cela permet d'envisager leur déploiement dans des pièces composites de grandes dimensions, pour évaluer les déformations et les concentrations de contraintes locales et ainsi faciliter la simulation et la modélisation dans ces zones critiques. La réponse électrique des QRS a aussi été utilisée pour évaluer l'accumulation d'endommagement dans les composites en association avec la microscopie et l'émission acoustique (AE) afin de détecter l'initiation de fissures et leur propagation dans des composites stratifiés. Sur la base des résultats obtenus dans cette étude, les QRS étudiés peuvent être considérées comme des capteurs en temps réel peu intrusifs qui semblent être tout à fait appropriés pour effectuer des mesures dvnamioues dans des aoolications d'inoénierie structurelleA new type of carbon nanotubes based Quantum Resistive Strain sensor (QRS sensor) for structural health monitoring (SHM) has been developed directly on glass fibers' surface via spray layer by layer (slbl) technique. The response of similar transducers was investigated under varying static and dynamic sollicitations. Different strategies of piezo-resistive sensing in GFRP are compared in terms of efficiency to follow mechanical solicitations and damages in both elastic and plastic demains. The results demonstrate that the sensors' output retains ail static and dynamic features of the input thus providing useful information for SHM and further can be extended for composite parts with large dimensions, to probe local stress/strain concentrations and facilitate the simulation of these critical areas. The electrical responses of QRS combined with those of the acoustic emission (AE) technique and microscopy have allowed investigating damage initiation and propagation in laminated composites. Based on the results obtained in this study, the investigated QRS can be considered as real time in situ non strongly invasive sensors which appear to be suitable for performing dynamic measurements in structural engineering applications
29
Saint-Aubin, Karell. "Etude de dispersions de nanotubes de carbone par des polymères pour l’élaboration de composites conducteurs et structurés." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14021/document.
Full textAbstract:
Cette thèse rapporte l’étude de dispersions de nanotubes de carbone par des polymères, la mise en forme de films composites et l’étude de leurs propriétés mécaniques ou de conduction électrique. La première partie est centrée autour de l’utilisation de l’acide poly-acrylique (PAA), qui se révèle un excellent agent dispersant des nanotubes dans l’eau. Une étude des interactions entre le polyélectrolyte et les nanotubes en fonction du pH est réalisée afin d’identifier les conditions de dispersion optimales. La réalisation de composites pour de potentielles applications dans les encres et peintures conductrices révèle qu’un contrôle suffisamment fin de l’adsorption du PAA et de la stabilité de la dispersion permet l’obtention de films à la fois homogènes et conducteurs électriques. La seconde partie de ce travail concerne l’utilisation d’un copolymère à blocs, le SBM, possédant des propriétés remarquables d’auto-organisation pour la réalisation de composites par voie solvant à base de nanotubes. L’originalité du système réside dans le fait que le SBM est à la fois agent dispersant des nanotubes mais également matrice structurante. Ce travail montre que la structure adoptée par le copolymère, qui dépend beaucoup du solvant employé, influence directement les propriétés mécaniques du matériau. De plus, l’addition de nanotubes améliore sensiblement les performances du compositeThis thesis deals with the study of carbon nanotube dispersions by polymers, the processing of composite films and the study of their mechanical and electrical properties. The first part of the work focuses on the use of poly(acrylic) acid (PAA), which proves to be an excellent dispersing agent in water. A study of the interactions between the PAA and the nanotubes is realised, tuned by the pH conditions. The fabrication of composite films, for future applications in the field of conductive inks and paints, shows that a fine control of the PAA adsorption and the dispersion stability allows the formation of homogeneous and conductive composites. In a second part, nanotube composites are elaborated from a block copolymer, the SBM, well-known for its remarkable self organization properties. Interestingly, the copolymer is at the same time the nanotube dispersing agent in the solvent and the structuring matrix of the final composite. This thesis shows that the copolymer structure, which strongly depends on the solvent used, influences the mechanical properties of composite films, and that the addition of nanotubes noticeably improves the performances
30
Benchirouf, Abderrahmane. "Carbonaceous Nanofillers and Poly(3,4-ethylenedioxythiophene) Poly(styrenesulfonate) Nanocomposites for Wireless Sensing Applications." Universitätsverlag der Technischen Universität Chemnitz, 2018. https://monarch.qucosa.de/id/qucosa%3A31903.
Full textAbstract:
The current state of wireless sensing technologies possesses a good reliability in terms of time response and sensing on movable parts or in embedded structures. Nevertheless, these tech- nologies involve energy supply such as battery and suffer from low resolution and bulky signal conditioning system for data processing. Thus, a RFID passive wireless sensor is a good candidate to overcome these issues. The feasibility of implementing microstrip patch antennas for sensing application were successfully investigated; however, low sensitivity was always a big issue to be concerned. Sensors based on nanocomposites attracted a lot of attention because of their excellent performance in term of light weight, high sensitivity, good stability and high resistance to corrosion but it lacks the capability of high conductivity, which limit their implication into RFID applications. This work introduces a novel high sensitive passive wireless strain and temperature sensors based on nanocomposites as sensing layer. To accomplish this, intrinsically conductive polymer based on carbon nanofillers nanocomposites are deeply studied and characterized. Then it’s performance is evaluated. Among them a novel tertiary nanocomposite is introduced, which opens the gate to new nanocomposite applications and thus broad- ens the application spectrum. Understanding the transport mechanism to improve the conductivity of the nanocomposite and extracting individually different models based on physical explanation of their piezoresistivity, and behavior under temperature and humidity have been developed. Afterwards, selected nanocomposites based on their high sensitivity to either strain or temperature are chosen to be used as sensing layer for patch antenna. The fabricated patch antenna has only one fundamental frequency, by determining the shift in its resonance frequency as function of the desired property to be measured; the wireless sensor characteristics are then examined. For strain sensing, the effect of strain is tested experimentally with the help of end-loaded beam measurement setup. For temperature sensing, the sensors are loaded in a controlled temperature/humid chamber and with the help of a vector network analyzer, the sensitivity of the antennas are extracted by acquiring the shift in the resonance frequency. The fabricated wireless sensors based on patch antenna are fabricated on very low lossy material to improve their gain and radiation pattern. This approach could be expanded also to include different type of substrates such as stretchable substrates i.e. elastomer polymer, very thing substrates such as Kapton, paper-based substrates or liquid crystal polymer.
31
Hashemi, Sanatgar Razieh. "FDM 3D printing of conductive polymer nanocomposites : A novel process for functional and smart textiles." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1I052/document.
Full textAbstract:
Le but de cette étude est d’exploiter les fonctionnalités des nano-Composites Polymères Conducteurs (CPC) imprimés en utilisant la technologie FDM (modélisation par dépôt de monofilament en fusion) pour le développement de textiles fonctionnels et intelligents. L’impression 3D présente un fort potentiel pour la création d’une nouvelle classe de nanocomposites multifonctionnels. Par conséquent, le développement et la caractérisation des polymères et nanocomposites fonctionnels et imprimables en 3D sont nécessaires afin d’utiliser l’impression 3D comme nouveau procédé de dépôt de ces matériaux sur textiles. Cette technique introduira des procédés de fonctionnalisation de textiles plus flexibles, économes en ressources et très rentables, par rapport aux procédés d'impression conventionnels tels que la sérigraphie et le jet d'encre. L’objectif est de développer une méthode de production intégrée et sur mesure pour des textiles intelligents et fonctionnels, afin d’éviter toute utilisation d'eau, d'énergie et de produits chimiques inutiles et de minimiser les déchets dans le but d’améliorer l'empreinte écologique et la productivité. La contribution apportée par cette thèse consiste en la création et la caractérisation de filaments CPC imprimables en 3D, le dépôt de polymères et de nanocomposites sur des tissus et l’étude des performances en termes de fonctionnalité des couches de CPC imprimées en 3D. Dans un premier temps, nous avons créé des filaments de CPC imprimables en 3D, notamment des nanotubes de carbone à parois multiples (MWNT) et du noir de carbone à haute structure (Ketjenblack) (KB), incorporés dans de l'acide polylactique (PLA) à l'aide d'un procédé de mélange à l'état fondu. Les propriétés morphologiques, électriques, thermiques et mécaniques des filaments et des couches imprimées en 3D ont été étudiées. Deuxièmement, nous avons déposé les polymères et les nanocomposites sur des tissus à l’aide d’une impression 3D et étudié leur adhérence aux tissus. Enfin, les performances des couches de CPC imprimées en 3D ont été analysées sous tension et force de compression appliquées. La variation de la valeur de la résistance correspondant à la charge appliquée permet d’évaluer l'efficacité des couches imprimées en tant que capteur de pression / force. Les résultats ont montré que les nanocomposites à base de PLA, y compris MWNT et KB, sont imprimables en 3D. Les modifications des propriétés morphologiques, électriques, thermiques et mécaniques des nanocomposites avant et après l’impression 3D nous permettent de mieux comprendre l’optimisation du procédé. De plus, différentes variables du procédé d’impression 3D ont un effet significatif sur la force d'adhérence des polymères et des nanocomposites déposés sur les tissus. Nous avons également développé des modèles statistiques fiables associés à ces résultats valables uniquement pour le polymère et le tissu de l’étude. Enfin, les résultats démontrent que les mélanges PLA/MWNT et PLA/KB sont de bonnes matières premières piézorésistives pour l’impression 3D. Elles peuvent être potentiellement utilisées dans l’électronique portable, la robotique molle et la fabrication de prothèses, où une conception complexe, multidirectionnelle et personnalisable est nécessaireThe aim of this study is to get the benefit of functionalities of fused deposition modeling (FDM) 3D printed conductive polymer nanocomposites (CPC) for the development of functional and smart textiles. 3D printing holds strong potential for the formation of a new class of multifunctional nanocomposites. Therefore, development and characterization of 3D printable functional polymers and nanocomposites are needed to apply 3D printing as a novel process for the deposition of functional materials on fabrics. This method will introduce more flexible, resource-efficient and cost-effective textile functionalization processes than conventional printing process like screen and inkjet printing. The goal is to develop an integrated or tailored production process for smart and functional textiles which avoid unnecessary use of water, energy, chemicals and minimize the waste to improve ecological footprint and productivity. The contribution of this thesis is the creation and characterization of 3D printable CPC filaments, deposition of polymers and nanocomposites on fabrics, and investigation of the performance of the 3D printed CPC layers in terms of functionality. Firstly, the 3D printable CPC filaments were created including multi-walled carbon nanotubes (MWNT) and high-structured carbon black (Ketjenblack) (KB) incorporated into a biobased polymer, polylactic acid (PLA), using a melt mixing process. The morphological, electrical, thermal and mechanical properties of the 3D printer filaments and 3D printed layers were investigated. Secondly, the performance of the 3D printed CPC layers was analyzed under applied tension and compression force. The response for the corresponding resistance change versus applied load was characterized to investigate the performance of the printed layers in terms of functionality. Lastly, the polymers and nanocomposites were deposited on fabrics using 3D printing and the adhesion of the deposited layers onto the fabrics were investigated. The results showed that PLA-based nanocomposites including MWNT and KB are 3D printable. The changes in morphological, electrical, thermal, and mechanical properties of nanocomposites before and after 3D printing give us a great understanding of the process optimization. Moreover, the results demonstrate PLA/MWNT and PLA/KB as a good piezoresistive feedstock for 3D printing with potential applications in wearable electronics, soft robotics, and prosthetics, where complex design, multi-directionality, and customizability are demanded. Finally, different variables of the 3D printing process showed a significant effect on adhesion force of deposited polymers and nanocomposites onto fabrics which has been presented by the best-fitted model for the specific polymer and fabric
32
Ressam, Ibitissam. "Élaboration et caractérisation de nouvelles membranes composites à conduction protonique pour les piles à combustible." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066732.
Full textAbstract:
Le Nafion a été considéré comme électrolyte modèle pour les piles à combustible (PAC), grâce à sa stabilité thermique et chimique ainsi que sa bonne conductivité protonique. Cependant, la conductivité protonique du Nafion se détériore à des taux d’humidité < 50% et à des températures >80°C. Pour cette raison de nouvelles membranes hybrides ont été élaborées afin d’en améliorer les performances. Plusieurs pistes ont été envisagées comme par exemple i) Membranes à base de chitosane, considéré comme le second polysaccharide le plus abondant après la cellulose. Ce polymère naturel permet d’assurer la stabilité physique et chimique de la membrane en présence d’eau, sans oublier son coût de revient qui reste moins cher en comparaison avec celui du Nafion et ii) Membranes à base de Nafion et d'argiles fibreuses (HNT), ces dernières confèrent à la membrane une conductivité protonique élevée en construisant des voies de transfert larges et continues. Cela permet aussi d'améliorer les propriétés thermiques et mécaniques des PEM. Notre étude est basée sur l'élaboration de membranes composites, nafion, chitosane et HNT. Des mesures de conductivité ont été entreprises et les valeurs obtenues comparées à celles du nafion. Des mesures d'ac-électrogravimétrie ont aussi été entreprises afin de mieux aborder les mécanismes de conductionThe perfluoro-sulfonated ionomer membranes are employed as separators in many industrialapplications such as fuel cells, chloro-alkali industry, electrodialysis and gaining inclininginterest in aqueous rechargeable or redox-flow batteries where the knowledge of their ionictransport and transfer properties is fundamental.Particularly, Nafion is adopted as a referencemembrane for polymer electrolyte membrane (PEM) fuel cells due to its thermal stability andgood proton conductivity. However, Nafion membranes have several disadvantages such as a decrease in the proton conductivity at low relative humidity (<50%) and high temperatures(>80°C), and excessive dimensional changes due to the swelling/deswelling, leading tomechanical instabilities.To circumvent these problems, novel proton conducting membraneshave been developed, either by completely replacing or by using organic and/or inorganiccomponents to Nafion.3 In this regard, a large spectrum of membranes have been elaboratedconsidering many attributes such as high proton conductivity, physical separation between theanode and the cathode and fuel barrier characteristics, good chemical and physical stability andlow elaboration cost of the membrane. Two types of additives were examined to improve the performances, particularly : Membranes based on Nafion with Chitosan biopolymer. This naturel polymer is consideredas the second most abundant polysaccharide after cellulose.6 Chitosan improves the physical andchemical stability of the membrane in the presence of water, and it is considered as a less costlyadditive to Nafion7.The improvement of the proton conductivity with pristine chitosan isessentially challenging. Previous studies demonstrated that vehicularandGrotthuss mechanismjointly govern the proton transfer in chitosan membranes.In the vehicular mechanism, the protons diffuse together with solvent molecules in the form of hydronium ions byforming acomplex such as H5O2+ and H9O4+. In the Grotthuss mechanism, however, the protons jump fromone solvent molecule or functional group to the next by the continuous formation and breakingof hydrogen bonds. Membranes based on Nafion with Halloysite nanotubes (HNT). These clays confer to themembrane high proton conductivity by constructing large and continuous conductionpathways.These inorganic additives also improve the thermal and mechanical properties of PEM. Composite membranes of Nafion/Chitosan- SO3H and Nafion/HNT-SO3H are prepared. Theresulting composite membranes were studied by various conventional structural characterizationtechniques. H+ conductivity measurements were performed and the values obtained are higherthan those of pristine Nafion at various relative humidity (RH%) levels and temperatures (30°C-80°C). Our results highlight the beneficial character of functionalized chitosan biopolymer andHalloysite nanotube clays as additives to improve PEM performances
33
El, Sawi Ihab. "Dispersion de nanotubes de carbone et intégration de la fonction de conductivité électrique dans les matériaux composites structuraux." Toulouse 3, 2010. http://thesesups.ups-tlse.fr/897/.
Full textAbstract:
Un procédé de dispersion des NTC dans l'eau puis dans une matrice époxy en présence de molécules amphiphiles est proposé ici. Le mélange NTC/Epoxy a fait l'objet d'une étude de cinétique de réaction et rhéologie. Le mode de conduction électrique des composites NTC/époxy en fonction de la fréquence et la température est déterminé. Une étude Thermomécanique Dynamique du composite NTC/Epoxy montre que module de cisaillement augmente avec le taux de NTC pour des températures supérieures à la Tg de la matrice. La dernière partie est dédiée à l'élaboration et caractérisation de stratifiés composites NTC/fibres de carbone/époxy. La conductivité électrique des stratifiés est améliorée par la présence de NTC. Enfin, les NTC ont permis d'améliorer de 30% le taux de restitution d'énergie (GIC)A process of dispersion of Double-Welled Carbon Nantubes (DWCNTs) assisted with amphiphilic molecules in water then in an epoxy matrix is proposed here. The DWCNTs/Epoxy mixtures were subject to reaction kinetic and shear flow study. The electrical conductivity of the DWCNTs/epoxy composites according to the frequency and the temperature is analysed. Dynamic Mechanical Analysis of the DWCNTs/Epoxy composites shows increasing of elastic shear modulus with DWCNTs content for temperatures higher than Tg of the matrix. The last part is dedicated to the development and characterization of composite laminates DWCNTs/Carbon fibres/Epoxy resin. The electric conductivity of the laminates is increased by the presence of DWCNTs and the DWCNTs improve the (GIC) by 30% compared with laminates made without DWCNTs
34
Maillaud, Laurent. "Formulation d’encres conductrices à base de nanotubes de carbone pour le développement d’électrodes transparentes." Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14904/document.
Full textAbstract:
Cette thèse rapporte l’étude des propriétés de films transparents conducteurs obtenus à partir de dispersions de nanotubes de carbone. La formulation des dispersions représente une étape clé dans le but d’obtenir des films homogènes avec de bonnes propriétés électro-optiques. Plus particulièrement, la création d’interactions attractives en solution entre les nanotubes de carbone permet d’une part de modifier le comportement rhéologique des dispersions et d’améliorer leur dépôt en couche mince par enduction. D’autre part, les travaux présentent une étude concernant l’influence des interactions sur la structuration du réseau de nanotube de carbone qui constitue les films. Ces changements de structuration sont notamment mis en parallèle avec les propriétés électriques des films selon leur épaisseur. L’utilisation de polymères semi-conducteurs a aussi fait l’objet de travaux expérimentaux pour améliorer la formation et les propriétés des films transparents conducteursThis thesis reports the study of the properties of transparent conductive films obtained from carbon nanotube dispersions. The dispersion formulation is a key step in order to obtain uniform films with good opto-electrical properties. In particular, the formation of attractive interactions between dissolved carbon nanotubes allows the modification of the rheological behavior of the dispersions and the improvement of their deposition in thin layer by coating. Also, the influence of the interactions on the carbon nanotube network morphology is presented. The structural changes of the networks are then related to both electrical properties and thickness of the films. Finally, the use of semiconducting polymers was analyzed in order to improve the fabrication and the properties of transparent conductive films
35
Islam, Rakibul. "Electrical and thermal transport properties of polymer/carbonaceous nanostructured composites." Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10131/document.
Full textAbstract:
Les polymères conducteurs composites présentent des propriétés thermoélectriques qui en font une solution prometteuse, peu coûteuse, propre et efficace pour la récupération de pertes de chaleur. L’objet de cette thèse est l’étude des propriétés de composites nanostructurés à base de polyaniline (PANI) en fonction de la concentration en nanoobjets: nanotubes de carbone (1-D) et oxyde de graphène réduit (RGO) (2-D). Leur structure et morphologie ont été étudiées par MEB, MET, diffraction des rayons X et diffusion Raman. Les conductivités électrique et thermique, le coefficient Seebeck, la figure de mérite thermoélectrique ZT, ont été mesurés. La conductivité électrique montre une augmentation importante avec la concentration en charges alors que la conductivité thermique ne croît que légèrement, ceci améliore ZT de plusieurs ordres de grandeur. L’effet de la dimensionnalité des charges a été mis en évidence. Mais quelle que soit cette dimension, la conductivité électrique contrairement à la conductivité thermique, suit un comportement de percolation à travers un processus de conduction à 2-D. Ce comportement a été également observé pour la capacité thermique volumique des nanohybrides PANI/RGO ce qui en fait des candidats potentiels dans le domaine des matériaux à haute capacité thermique. Leur facteur de stockage de chaleur est traité avec un nouveau modèle analytique. Les échantillons de PANI/RGO ont été étudiés par spectroscopie diélectrique à différentes températures. Les résultats font apparaître un phénomène intéressant de piégeage de charges à l’interface PANI/RGO qui pourrait trouver des applications dans les supercondensateurs et les mémoires électroniquesConducting polymer nanocomposites exhibit for instance interesting thermoelectric properties which make them a promising, inexpensive, clean and efficient solution for heat waste harvesting. This thesis reports on properties of polyaniline (PANI) nanostructured composites as a function of various carbonaceous nano-fillers content such as carbon nanotubes (1-D), and 2-D reduced graphene oxide (RGO). SEM, TEM, X-ray diffraction, and Raman spectroscopy have been employed to investigate their structure and morphology. Electrical and thermal conductivity, Seebeck coefficient, and thermoelectric figure of merit (ZT) have been systematically performed. An important increase of electrical conductivity has been observed with increasing filler fraction whereas thermal conductivity only slightly increases, which enhances ZT of several orders of magnitude. Fillers dimension effect is evidenced, but, whatever this dimension, it is shown that, in contrast with thermal conductivity, electrical conductivity follows a percolation behavior through 2D conduction process. This behavior is also observed in the case of the volumetric heat capacity of PANI/RGO nanohybrids which make them potential candidates as high heat capacitive materials. For the first time their heat storage factor is assessed with a new analytical model proposed in this study. The PANI/RGO samples have also been investigated by Dielectric Spectroscopy at different temperatures. Results evidence an interesting charge trapping phenomenon occurring at the PANI/RGO interface which might find promising applications in supercapacitors or gate memory devices
36
Pillet, Guillaume. "Diffusion thermique de nanocarbones au voisinage d'une surface de polymère thermoplastique." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30247.
Full textAbstract:
Les applications intégrant les nanotubes de carbone augmentent rapidement maintenant que leur bio-toxicité a été évaluée comme limitée. Une fois intégrés dans une matrice polymère, il est possible d'ajuster les propriétés mécaniques et électriques de celle-ci. Dans cette thèse, nous avons étudié la formation et la diffusion de films minces de nanotubes de carbones multi-parois (MWCNT) à la surface d'un polymère thermoplastique haute performance, le poly éther éther cétone (PEEK) possédant un point de fusion élevé (342 ° C). La synthèse des films composites conducteurs électriques comportent différentes étapes de préparation (dispersion dans des liquides, création d'interface en jouant sur les miscibilités). L'optimisation des paramètres de recuit a permis d'avoir des mesures électriques et optiques exploitables. Nous avons analysé en détail la diffusion du polymère dans le film de nanotubes et étudié la dynamique du front de diffusion à l'aide de la microscopie électronique. Un modèle simple pour la conductivité électrique permet expliquer quantitativement les observations expérimentales. La corrélation entre la conductivité électrique et la transmittance optique d'une couche composite donnée, permet d'étudier la diffusion en fonction de la durée de recuit. Les propriétés piézo-électriques des films composites minces fabriqués ne sont que partiellement réversibles en raison du transfert limité des contraintes mécaniques au réseau de nanotubes de carbone. En contrôlant l'imprégnation des agglomérats de nanotubes par le polymère, il est possible de contrôler les propriétés électriques de la surface, ce qui peut avoir des applications pour la réparation de surfaces composites et la restauration de leurs propriétés électriques ou mécaniques. La spectroscopie Raman et la microscopie électronique à transmission ont été utilisées pour la caractérisation structurelle. Le travail présenté est définitivement multidisciplinaire couvrant la synthèse, la caractérisation structurelle et mesures de transport électronique pour comprendre la formation de surface composites conductrices électriqueThe use of carbon nanotubes is growing fast since their limited bio-toxicity has been assessed. When embedded in a polymeric matrix, one can tailor the mechanical and electrical properties. In this thesis, we studied the formation and diffusion of multiwall carbon nanotube (MWCNT) thin films at the surface of a high performance thermoplastic polymer, poly-ether-ether-ketone (PEEK) with a high temperature melting point (342 °C). The synthesis and characterization of the electrically conductive composite films consists of different preparation steps (dispersion in liquids, creation of interface by playing on the miscibilities) and the optimization of the annealing parameters followed by electrical and optical measurements. We analyzed in detail the diffusion of the polymer into the nanotube film and studied the diffusion front using electron microscopy. A simple model of the electrical conductivity can explain quantitatively the experimental observations. Correlating the electrical conductivity and optical transmittance of a given composite layer allows studying the diffusion as a function annealing time. Piezo-electrical properties of the fabricated thin composite film are only partially reversible due to limited transfer of mechanical stress to the carbon nanotube network. By controlling the impregnation of the agglomerated nanotubes by the polymer, it is possible to control the electrical properties of the surface which may have applications for the repair of composite surfaces and the restoration of electrical or mechanical surface properties. Raman spectroscopy and transmission electron microscopy have been used for the structural characterization. The presented work is definitively multidisciplinary covering synthesis, structural characterization and electronic transport measurements to understand the formation of electrically conducting surface composites
37
Hamdi, Khalil. "Fonctionnalisation de matériaux composites à renfort carbone et matrice thermoplastique par adjonction de nanocharges : élaboration et étude du comportement." Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2388/document.
Full textAbstract:
Pour étendre l'utilisation des composites dans des applications plus variées (applications intelligentes et multifonctionnelles), l'une des barrières est leur faible conductivité électrique et thermique. Dans le cas de composites renforcés par des fibres de carbone, la matrice organique est responsable des propriétés isolantes du composite résultant. L'une des solutions pour améliorer les conductivités des matériaux est l'utilisation des nanocharges conductrices. L'amélioration des propriétés électriques et thermiques des polymères nanochargés est une problématique récurrente dans la littérature. Cependant, étudier les propriétés des composites à fibre de carbone continue et nanochargés est moins abordée. Ce travail porte sur la fabrication et la caractérisation des composites nanochargés par du noir de carbone et des nanotubes de carbone. Tout d'abord, un intérêt particulier a été accordé à la phase délicate de la fabrication. Comme mentionné ci-dessus, la mise en œuvre des composites à renfort continu et matrice nanochargée implique des problèmes liés à l'agglomération et à la dispersion inhomogène des nanocharges dans le composite final. Pour résoudre ces problèmes, le choix de la matrice thermoplastique (Polyamide 6) était judicieux. En fait, la dispersion des nanocharges a été faite par extrusion bi-vis qui est connue comme l'une des voies les plus efficaces de séparation d'agglomérats. De plus, la méthode de fabrication à base de films de Polyamide 6, appelée film stacking, assure une partition homogène dès le début du processus. Des observations MEB ont été effectuées pour localiser les nanoparticules. Ceux-là ont montré que les particules pénétraient dans la zone des fibres. En effet, en atteignant le cœur des torons, les nano-charges ont créé un réseau de connectivité entre les fibres pour le passage de courant. Ceci explique l'amélioration constatée de la conductivité électrique des composites en présence de noir de carbone et des nanotubes de carbone. Ces essais ont été réalisés avec la méthode à 4 points. La conductivité électrique du composite à matrice « pure » est passée de 20S / cm à 80S / cm en ajoutant 8% en poids de noir de carbone et à 15S / cm en ajoutant 18% en poids de la même charge nanométrique. Pour les nanotubes de carbone, avec 2,5% en poids, la conductivité était d'environ 150S / cm. Pour les propriétés thermiques, des tests basés sur l'effet Joule ont été réalisés. L'augmentation de la température a été enregistrée en utilisant une caméra IR. Les résultats obtenus sont en accord avec ceux de la conductivité électrique, montrant une amélioration du comportement thermique en présence de nanocharges. Grâce à ces résultats, l'utilisation de ces composites comme outil de suivi d’endommagement était possible. Par ailleurs, la méthode de variation de la résistance électrique a été effectuée. Les matériaux nanochargés ont montré une meilleure sensibilité aux endommagements. Les résultats ont été comparés aux outils classiques de suivi d’endommagement. A la fin, plusieurs applications « intelligentes » ont été testées telles que : le composite à gradients de propriétés et des matériaux nanochargés coususTo extend the use of composites in more varied application (smart applications, multifunctional issues), one of the actual barrier is their poor electrical and thermal conductivities. In the case of carbon fiber reinforced composites, organic matrix are in charge of the insulating properties of the resulting composite. One of the solutions to enhance conductivities of materials is the use of conductive nanofillers. Improving the electrical and thermal properties of nanofilled polymers has been investigated in several studies. However, studiing the properties of continuous carbon fiber nano-filled composites is less approached. This work tends to fabricate and characterize carbon black and carbon nanotubes nano-filled composites. First of all, special interest was given to the delicate phase of manufacturing. As mentioned before, processing continuous fiber reinforced nanofilled polymers implies issues related to nanofillers agglomeration and inhomogeneous dispersion in the final composite. To resolve these problems, the choice of the thermoplastic (Polyamide6) matrix seemed preferable. In fact, the dispersion of nanofillers was made by twin screw extrusion which is known as one of the most effective agglomeration separation ways. Adding to this, the fabrication method based on Polyamide 6 shects called film stacking, ensure a homogeneous partition at the beginning of the process. SEM observations were performed to localize the nano-particles. It showed that particles penetrated on the fiber zone. In fact, by reaching the fiber zone, the nano-fillers created network connectivity between fibers which means an easy pathway for the current. It explains the noticed improvement of the electrical conductivity of the composites by adding carbon black and carbon nanotube. This test was performed with the 4 points electrical circuit. It shows that electrical conductivity of 'neat' matrix composite passed from 20S/cm to 80S/cm by adding 8wt% of carbon black and to 15S/cm by adding 18wt% of the same nano-filler. For carbon nanotubes, with '2.5wt% the conductivity was around 150S/cm. For the thermal properties, tests based on Joule's effect were performed. The rise of temperature was recorded using IR camera. Results obtained are in agreement with the electrical conductivity ones, showing enhancement of the thermal behavior in presence of nanofillers. Thanks to these results, the use of these composites as a damage-monitoring tool was possible. By the way, the electrical resistance change method was performed. Nanofilled materials showed better sensitivity to damage. Results were compared with classical damage monitoring tools. At the end, several 'smart' applications were tested such as graded functionalities composite and stitched nanofilled materials
38
Choudhury, Paramita Kar. "Conformation And Charge Transpsort In Conducting Polymers, Carbon Nanotubes And Their Nanocomposites." Thesis, 2010. https://etd.iisc.ac.in/handle/2005/1987.
Full textAbstract:
The main motivation in this thesis is to compare the conformation and charge transport in conducting polymers and carbon nanotubes (CNTs) and to investigate those physical properties in their combined form of nanocomposites. It is known that both conducting polymers and carbon nanotubes are intrinsically 1-dimensional systems which consist of delocalized π-electrons. However, the main difference between these is the fact that flexibility of conducting polymers can be varied depending on the extent of conjugation while CNTs are rigid. Hence a comparison of electronic properties as correlated to their morphology has been carried out and their individual role in nanocomposites is further studied.
The thesis consists of 6 chapters and appendix. Chapter 1 consists of brief introduction of general properties of both conducting polymers, CNTs and their nanocomposites. Chapter 2 deals with the sample preparation and experimental techniques used for the work. Chapter 3 elaborates on the conformational / structural studies on the systems. Chapter 4 focuses on the transport measurements to study the electronic properties of the samples. Chapter 5 reveals the magnetic properties of these systems which can be applied in technological devices. And chapter 6 gives the conclusion and future directions of the work being done.
Chapter 1: Nanocomposites represent a guest-host matrix consisting of easily processible functionalized conjugated polymer as host, incorporating carbon nanotubes as fillers with versatile electronic and magnetic properties, which provide a wide range of technological applications. The conformation, charge dynamics as well as magnetic properties of these conducting polymers and carbon nanotubes, and various aspects of transport mechanism and spin dynamics present in the nanocomposite matrix are studied and presented in a consistent framework.
Chapter 2: The multiwall carbon nanotubes (MWNTs) are grown by thermal chemical vapor deposition (CVD). The MWNTs are dispersed in solution of conducting polymers by ultrasonication and then the suspension is cast on glass substrate and slowly dried by moderate heating. Once dried completely, the free-standing films of thickness 15-25 μm are peeled off the substrate for measurements. The MWNTs, above a certain concentration, form an interconnected network in the 3-dimensional polymer matrix, following percolation mechanism. The disorder is brought into the system mainly by bundling of tubes and bundle intersections. The morphology and conformation of the samples are studied by SEM, TEM and small angle X-ray scattering (SAXS) techniques.
Chapter 3: Small angle X-ray scattering (SAXS) studies in polymeric systems are carried out to probe local nanoscale morphology at various length scales to show the correlation among conformation and assembly of chains.
Small angle X-ray scattering (SAXS) studies are carried out in poly [2-methoxy5-(2’–ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) solution of varying conjugation lengths as well as different solvents. By increasing the extent of πconjugation from 30 to 100 %, the persistence length increases by a factor of three. Moreover, a pronounced second peak in the pair distribution function is observed in fully conjugated chain, at larger length scales which indicates that the chain segments tend to self-assemble as the conjugation along the chain increases.
The chain assembly and aggregation are further studied for suspensions of MWNTs in polyethylene dioxythiophene-polystyrene (PEDOT-PSS) with aqueous medium and DMSO (dimethyl sulphoxide). The SAXS profile of MWNT dispersion in aqueous PEDOT-PSS clearly show rigid-rod feature of the individual nanotubes evident by the q-1 behavior at short ranges. The crossover from q-1 to q-2 in the longer range further suggest that the suspension consists of individual nanotubes, nanotubes bundles and aggregates that give rise to a 3-dimensonal meshwork of intersecting tubes and ropes. For the MWNT dispersion in PEDOT-PSS with DMSO, however, such q-1 behavior is absent; which evidently shows that the rods are not isolated in the solution and are rather agglomerated. How these conformations affect the electrical and magnetic properties of these systems are studied further in Chapter 4.
Chapter 4: Transport mechanism in single wall carbon nanotubes (SWNT), MWNT
pellets, and nanocomposite films of MWNT and PEDOT-PSS is studied.
The positive and negative magnetoresistance (MR) data in various SWNT samples are analyzed by taking into account the electron-electron interaction (EEI) contribution, in addition to the weak localization (WL) regime. The contribution from EEI to the total MR is confirmed from the universal scaling of MC relation showing that EEI plays a significant role at higher fields and lower temperatures. Intrinsic parameters like inelastic scattering length extracted for barely metallic sample follows the T-3/4 dependence due to inelastic electron-electron scattering in the dirty limit.
Conductivity and magnetoresistance (MR) measurements on nanocomposite films with varying MWNT content (0.03 - 3 %) are performed at a field range 0-11 Tesla, and temperature range 1.3–300 K. The temperature dependence of resistance above 4 K suggests a Coulomb-gap variable range hopping (CG-VRH) transport in the network. Alhough solely negative MR (~ 5-6 %) is observed for pristine MWNT pellets; the nanocomposite films show a combination of large negative MR (~ 80 %) at T < 4 K, and a comparatively weaker positive MR (~ 30 %) for T > 4 K. This suggest that there are two mechanism interplaying and dominant at different temperature regimes which can be explained by the mechanism of transport of the charge carriers of MWNT intervened by that of the polymer matrix.
In conclusion how the individual properties of conducting polymer and carbon
nanotubes contribute to the unique electronic and conformational properties in their
nanocomposites is framed in this investigation.
Chapter 5: Magnetic properties of the pristine MWNTs as well as metal nanowires of nickel, nickel-iron (NiFe), nickel-iron-cobalt (NiFeCo) encapsulated in the MWNTs are studied using superconducting quantum interference device (SQUID) magnetometer.
A typical example of Ni nanowires encapsulated in MWNT (Ni-MWNT) is taken and the results are compared to other forms of nickel (bulk, nanorod cluster, nanowire) to see the effect of size, shape and environment on the magnetic kproperties. The saturation magnetization and coercivity for Ni-MWNTs are 1.0 emu/gm and 230 Oe.
The temperature dependence of magnetization indicates superparamagnetic which is supported by the field-cooled and zero-field-cooled plots determining a blocking temperature ~ 300 K. These altered magnetic properties of Ni-MWNTs are mainly due to the contribution from carbon nanotube encapsulation.
Both the shape and environment enhance the total magnetic anisotropy of encapsulated nanowires at least by a factor of four.
The encapsulation of metal nanowires in MWNTs tunes the magnetic properties of the system widely, e.g. from diamagnetic (pristine MWNTs) to paramagnetic (Ni-MWNT) to ferromagnetic (NiFe-MWNT) and a combination of para and ferro (NiFeCo-MWNT).
Chapter 6: The conclusions of the different works presented in the thesis are coherently summarized in this chapter. Thoughts for future directions are also summed up.
Appendix A: Spin dynamics in conducting polymer PEDOT-PSS in its pristine, processed with DMSO and nanocomposite form (with carbon nanotubes) is studied using solid state nuclear magnetic resonance (NMR). Plots of proton spin lattice relaxation times vs. temperature at a fixed frequency 23.4 MHz are compared to study the effect of the external agents on the polymer dynamics.
39
Choudhury, Paramita Kar. "Conformation And Charge Transpsort In Conducting Polymers, Carbon Nanotubes And Their Nanocomposites." Thesis, 2010. http://etd.iisc.ernet.in/handle/2005/1987.
Full textAbstract:
The main motivation in this thesis is to compare the conformation and charge transport in conducting polymers and carbon nanotubes (CNTs) and to investigate those physical properties in their combined form of nanocomposites. It is known that both conducting polymers and carbon nanotubes are intrinsically 1-dimensional systems which consist of delocalized π-electrons. However, the main difference between these is the fact that flexibility of conducting polymers can be varied depending on the extent of conjugation while CNTs are rigid. Hence a comparison of electronic properties as correlated to their morphology has been carried out and their individual role in nanocomposites is further studied.
The thesis consists of 6 chapters and appendix. Chapter 1 consists of brief introduction of general properties of both conducting polymers, CNTs and their nanocomposites. Chapter 2 deals with the sample preparation and experimental techniques used for the work. Chapter 3 elaborates on the conformational / structural studies on the systems. Chapter 4 focuses on the transport measurements to study the electronic properties of the samples. Chapter 5 reveals the magnetic properties of these systems which can be applied in technological devices. And chapter 6 gives the conclusion and future directions of the work being done.
Chapter 1: Nanocomposites represent a guest-host matrix consisting of easily processible functionalized conjugated polymer as host, incorporating carbon nanotubes as fillers with versatile electronic and magnetic properties, which provide a wide range of technological applications. The conformation, charge dynamics as well as magnetic properties of these conducting polymers and carbon nanotubes, and various aspects of transport mechanism and spin dynamics present in the nanocomposite matrix are studied and presented in a consistent framework.
Chapter 2: The multiwall carbon nanotubes (MWNTs) are grown by thermal chemical vapor deposition (CVD). The MWNTs are dispersed in solution of conducting polymers by ultrasonication and then the suspension is cast on glass substrate and slowly dried by moderate heating. Once dried completely, the free-standing films of thickness 15-25 μm are peeled off the substrate for measurements. The MWNTs, above a certain concentration, form an interconnected network in the 3-dimensional polymer matrix, following percolation mechanism. The disorder is brought into the system mainly by bundling of tubes and bundle intersections. The morphology and conformation of the samples are studied by SEM, TEM and small angle X-ray scattering (SAXS) techniques.
Chapter 3: Small angle X-ray scattering (SAXS) studies in polymeric systems are carried out to probe local nanoscale morphology at various length scales to show the correlation among conformation and assembly of chains.
Small angle X-ray scattering (SAXS) studies are carried out in poly [2-methoxy5-(2’–ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) solution of varying conjugation lengths as well as different solvents. By increasing the extent of πconjugation from 30 to 100 %, the persistence length increases by a factor of three. Moreover, a pronounced second peak in the pair distribution function is observed in fully conjugated chain, at larger length scales which indicates that the chain segments tend to self-assemble as the conjugation along the chain increases.
The chain assembly and aggregation are further studied for suspensions of MWNTs in polyethylene dioxythiophene-polystyrene (PEDOT-PSS) with aqueous medium and DMSO (dimethyl sulphoxide). The SAXS profile of MWNT dispersion in aqueous PEDOT-PSS clearly show rigid-rod feature of the individual nanotubes evident by the q-1 behavior at short ranges. The crossover from q-1 to q-2 in the longer range further suggest that the suspension consists of individual nanotubes, nanotubes bundles and aggregates that give rise to a 3-dimensonal meshwork of intersecting tubes and ropes. For the MWNT dispersion in PEDOT-PSS with DMSO, however, such q-1 behavior is absent; which evidently shows that the rods are not isolated in the solution and are rather agglomerated. How these conformations affect the electrical and magnetic properties of these systems are studied further in Chapter 4.
Chapter 4: Transport mechanism in single wall carbon nanotubes (SWNT), MWNT
pellets, and nanocomposite films of MWNT and PEDOT-PSS is studied.
The positive and negative magnetoresistance (MR) data in various SWNT samples are analyzed by taking into account the electron-electron interaction (EEI) contribution, in addition to the weak localization (WL) regime. The contribution from EEI to the total MR is confirmed from the universal scaling of MC relation showing that EEI plays a significant role at higher fields and lower temperatures. Intrinsic parameters like inelastic scattering length extracted for barely metallic sample follows the T-3/4 dependence due to inelastic electron-electron scattering in the dirty limit.
Conductivity and magnetoresistance (MR) measurements on nanocomposite films with varying MWNT content (0.03 - 3 %) are performed at a field range 0-11 Tesla, and temperature range 1.3–300 K. The temperature dependence of resistance above 4 K suggests a Coulomb-gap variable range hopping (CG-VRH) transport in the network. Alhough solely negative MR (~ 5-6 %) is observed for pristine MWNT pellets; the nanocomposite films show a combination of large negative MR (~ 80 %) at T < 4 K, and a comparatively weaker positive MR (~ 30 %) for T > 4 K. This suggest that there are two mechanism interplaying and dominant at different temperature regimes which can be explained by the mechanism of transport of the charge carriers of MWNT intervened by that of the polymer matrix.
In conclusion how the individual properties of conducting polymer and carbon
nanotubes contribute to the unique electronic and conformational properties in their
nanocomposites is framed in this investigation.
Chapter 5: Magnetic properties of the pristine MWNTs as well as metal nanowires of nickel, nickel-iron (NiFe), nickel-iron-cobalt (NiFeCo) encapsulated in the MWNTs are studied using superconducting quantum interference device (SQUID) magnetometer.
A typical example of Ni nanowires encapsulated in MWNT (Ni-MWNT) is taken and the results are compared to other forms of nickel (bulk, nanorod cluster, nanowire) to see the effect of size, shape and environment on the magnetic kproperties. The saturation magnetization and coercivity for Ni-MWNTs are 1.0 emu/gm and 230 Oe.
The temperature dependence of magnetization indicates superparamagnetic which is supported by the field-cooled and zero-field-cooled plots determining a blocking temperature ~ 300 K. These altered magnetic properties of Ni-MWNTs are mainly due to the contribution from carbon nanotube encapsulation.
Both the shape and environment enhance the total magnetic anisotropy of encapsulated nanowires at least by a factor of four.
The encapsulation of metal nanowires in MWNTs tunes the magnetic properties of the system widely, e.g. from diamagnetic (pristine MWNTs) to paramagnetic (Ni-MWNT) to ferromagnetic (NiFe-MWNT) and a combination of para and ferro (NiFeCo-MWNT).
Chapter 6: The conclusions of the different works presented in the thesis are coherently summarized in this chapter. Thoughts for future directions are also summed up.
Appendix A: Spin dynamics in conducting polymer PEDOT-PSS in its pristine, processed with DMSO and nanocomposite form (with carbon nanotubes) is studied using solid state nuclear magnetic resonance (NMR). Plots of proton spin lattice relaxation times vs. temperature at a fixed frequency 23.4 MHz are compared to study the effect of the external agents on the polymer dynamics.
40
Sangeeth, Suchand C. S. "Charge Transport In Conducting Polymers, Polymer-Carbon Nanotube Composites And Devices." Thesis, 2012. http://etd.iisc.ac.in/handle/2005/2279.
Full textAbstract:
The Thesis reports charge transport studies on conducting polymers, polymer carbon nanotube composites and organic semiconductor devices. Conducting and semiconducting polymers consisting of π-conjugated chains have attracted
considerable attention as they combine the optoelectronic properties of
semiconductors with mechanical properties and processing advantages of plastics. The chemical/electrochemical/photodoping of these semiconducting polymers can tune the Fermi levels and conductivity in a controlled way, and hence the properties of devices can be easily tailored to suit in several applications. Carbon nanotube (CNT) is another another novel promising material for electronic/optoelectronic applications. Lately there has been a great interest in developing composites of polymer and CNTs to utilize the advantages of both CNTs and polymers. The inclusion of CNTs in polymers improves the mechanical, electrical and thermal properties since the aspect ratio (ratio of length to diameter) is very large, as well its density is rather low.
The Thesis consists of 6 chapters. First chapter is a brief introduction of general
and transport properties of conducting polymers and polymer-carbon nanotube
composites. In Chapter 2, the sample preparation and experimental techniques used in this work are discussed. The charge transport in poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) is presented in Chapter 3. Chapter 4 focuses on the transport measurements in the polymer-CNT composite samples. Chapter 5 elaborates the ac and dc characterization of organic field-effect transistors (OFETs). And chapter 6 presents the conclusion and future directions of the work that has been presented in the Thesis.
Chapter 1: In the scientific and technological revolution of the last few years, the study of high performance materials has been steadily increasing including the study of carbon-based materials. Conducting polymers have special properties that are interesting for this new technology. The charge transport in conjugated polymers is important to optimize the performance of devices. The discovery of CNTs with exceptional thermal, mechanical, optical, electrical and structural properties has facilitated the synthesis of new type of nanocomposites with very interesting properties. Nanocomposites represent a guest-host matrix consisting of easily processible functionalized conjugated polymer as host, incorporating CNTs as fillers with versatile electronic and magnetic properties, which provide a wide range of technological applications. To optimize their electrical properties it is essential to understand the charge transport mechanism in detail.
Chapter 2: The multi-wall carbon nanotubes (MWNTs) grown by thermal chemical vapor deposition (CVD) are mixed with a 1:1 mixture of 98% H2SO4 and 70% HNO3 to produce sulfonic acid functionalized multi-wall carbon nanotubes (s-MWNTs). The s-MWNTs are dispersed in a solution of Nafion by ultrasonication and then cast on a glass substrate and slowly dried by moderate heating to obtain the composite films. Polyaniline (PANI)-MWNT composites were obtained by carrying out the chemical synthesis of nanofibrilar PANI in the presence of CNTs. This water dispersible PANIMWNT composite contains well segregated MWNTs partially coated by nanofibrilar PANI. The ac and dc charge transport measurements suggest hopping transport in these materials. OFETs are fabricated with pentacene, poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene)(PBTTT) and poly(3-hexylthiophene) (P3HT) as active materials. A novel technique is used to characterize the acphotoresponse of these OFETs.
Chapter 3: Charge transport studies on PEDOT-PSS have been carried out and
found that it correlates with the morphology. The dc conductivity of PEDOT–PSS shows enhanced delocalization of the carriers upon the addition of dimethyl sulfoxide (DMSO) and this is attributed to the extended chain conformation. PEDOT-PSS is known to form a phase-segregated material comprising highly conducting PEDOT grains that are surrounded by a sea of weakly ionic-conducting PSS and a wide variation in the charge transport properties of PEDOT-PSS films is attributed to the degree of phasesegregation of the excess insulating polyanion. The magnetotransport and temperature dependent ac transport parameters across different conducting grades of PEDOT-PSS processed with DMSO were compared. Depending on the subtle alterations in morphology, the transport at low temperatures is shown to vary from the hopping regime (Baytron P) to critical regime of the metal-insulator transition (Baytron PH510) There is a significant positive magnetoresistance (MR) for P–films, but this is considerably less in case of PH510-film. From the low temperature ac conductance it is found that the onset frequency for PH510 is nearly temperature independent, whereas in P type it is strongly temperature dependent, again showing the superior transport in PH510. The presence of ‘shorter network connections’ together with a very weak temperature dependence down to ~ 5 K, suggest that the limitation on transport in PH510 arises from the connectivity within the PEDOT-rich grain rather than transport via the PSS barriers.
Chapter 4: DC and AC charge transport properties of Nafion s-MWNT and PANI-MWNT composites are studied. Such a detailed investigation is required to optimize the correlation among morphology and transport properties in these composites towards applications in field-effect transistors, antistatic coating, electromagnetic shielding, etc. The conductivity in Nafion s-MWNT shows a percolative transport with percolation threshold pc = 0.42 whereas such a sharp percolation is absent in PANI-MWNT composite since the conduction via PANI matrix smears out the onset of rapid increase in conductivity. Three-dimensional variable range hopping (VRH) transport is observed in Nafion s-MWNT composites. The positive and negative MR data on 10 wt. % sample are analyzed by taking into account forward interference mechanism (negative MR)
and wave-function shrinkage (positive MR), and the carrier scattering is observed to be in the weak limit. The electric-field dependence, measured to high fields, follows the predictions of hopping transport in high electric-field regime. The ac conductivity in 1 wt. % sample follows a power law: ( ) A s , and s decreases with increasing temperature as expected in the correlated barrier hopping (CBH) model. In general, Mott’s VRH transport is observed in PANI-MWNT samples. It is found that the MWNTs are sparingly adhered with PANI coatings, and this facilitates inter-tube hopping at low temperatures. The negative MR of MWNT-PANI composites suggest that the electronic transport at low temperatures is dominated by MWNT network. AC impedance measurements at low temperatures with different MWNT loading show that ac conductivity become temperature independent as the MWNT content increases. The onset frequency for the increase in conductivity is observed to be strongly dependent on the MWNT weight percentage, and the ac conductivity can be scaled onto a master
curve given by ( ) 0[1 k( 0 )s ].
Chapter 5: Organic field-effect transistors (OFETs) based on small molecules and polymers have attracted considerable attention due to their unique advantages, such as low cost of fabrication, ease of processing and mechanical flexibility. Impedance characterization of these devices can identify the circuit elements present in addition to the source-drain (SD) channel, and the bottlenecks in charge transport can be identified. The charge carrier trapping at various interfaces and in the semiconductor can be estimated from the dc and ac impedance measurements under illumination. The equivalent circuit parameters for a pentacene OFET are determined from low frequency impedance measurements in the dark as well as under light illumination. The charge accumulation at organic semiconductor–metal interface and dielectric semiconductor interface is monitored from the response to light as an additional parameter to find out the contributions arising from photovoltaic and photoconductive effects. The shift in threshold voltage is due to the accumulation of photogenerated carriers under SD electrodes and at dielectric–semiconductor interface, and also this dominates the carrier transport. Similar charge trapping is observed in an OFET with PBTTT as the active material. This novel method can be used to differentiate the photophysical phenomena occurring in the bulk from that at the metal-semiconductor interface for the polymer.
Chapter 6: The conclusions from the various works presented in the thesis are
coherently summarized in this chapter. Thoughts for future directions are also
summed up.
41
Sangeeth, Suchand C. S. "Charge Transport In Conducting Polymers, Polymer-Carbon Nanotube Composites And Devices." Thesis, 2012. http://etd.iisc.ernet.in/handle/2005/2279.
Full textAbstract:
The Thesis reports charge transport studies on conducting polymers, polymer carbon nanotube composites and organic semiconductor devices. Conducting and semiconducting polymers consisting of π-conjugated chains have attracted
considerable attention as they combine the optoelectronic properties of
semiconductors with mechanical properties and processing advantages of plastics. The chemical/electrochemical/photodoping of these semiconducting polymers can tune the Fermi levels and conductivity in a controlled way, and hence the properties of devices can be easily tailored to suit in several applications. Carbon nanotube (CNT) is another another novel promising material for electronic/optoelectronic applications. Lately there has been a great interest in developing composites of polymer and CNTs to utilize the advantages of both CNTs and polymers. The inclusion of CNTs in polymers improves the mechanical, electrical and thermal properties since the aspect ratio (ratio of length to diameter) is very large, as well its density is rather low.
The Thesis consists of 6 chapters. First chapter is a brief introduction of general
and transport properties of conducting polymers and polymer-carbon nanotube
composites. In Chapter 2, the sample preparation and experimental techniques used in this work are discussed. The charge transport in poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) is presented in Chapter 3. Chapter 4 focuses on the transport measurements in the polymer-CNT composite samples. Chapter 5 elaborates the ac and dc characterization of organic field-effect transistors (OFETs). And chapter 6 presents the conclusion and future directions of the work that has been presented in the Thesis.
Chapter 1: In the scientific and technological revolution of the last few years, the study of high performance materials has been steadily increasing including the study of carbon-based materials. Conducting polymers have special properties that are interesting for this new technology. The charge transport in conjugated polymers is important to optimize the performance of devices. The discovery of CNTs with exceptional thermal, mechanical, optical, electrical and structural properties has facilitated the synthesis of new type of nanocomposites with very interesting properties. Nanocomposites represent a guest-host matrix consisting of easily processible functionalized conjugated polymer as host, incorporating CNTs as fillers with versatile electronic and magnetic properties, which provide a wide range of technological applications. To optimize their electrical properties it is essential to understand the charge transport mechanism in detail.
Chapter 2: The multi-wall carbon nanotubes (MWNTs) grown by thermal chemical vapor deposition (CVD) are mixed with a 1:1 mixture of 98% H2SO4 and 70% HNO3 to produce sulfonic acid functionalized multi-wall carbon nanotubes (s-MWNTs). The s-MWNTs are dispersed in a solution of Nafion by ultrasonication and then cast on a glass substrate and slowly dried by moderate heating to obtain the composite films. Polyaniline (PANI)-MWNT composites were obtained by carrying out the chemical synthesis of nanofibrilar PANI in the presence of CNTs. This water dispersible PANIMWNT composite contains well segregated MWNTs partially coated by nanofibrilar PANI. The ac and dc charge transport measurements suggest hopping transport in these materials. OFETs are fabricated with pentacene, poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene)(PBTTT) and poly(3-hexylthiophene) (P3HT) as active materials. A novel technique is used to characterize the acphotoresponse of these OFETs.
Chapter 3: Charge transport studies on PEDOT-PSS have been carried out and
found that it correlates with the morphology. The dc conductivity of PEDOT–PSS shows enhanced delocalization of the carriers upon the addition of dimethyl sulfoxide (DMSO) and this is attributed to the extended chain conformation. PEDOT-PSS is known to form a phase-segregated material comprising highly conducting PEDOT grains that are surrounded by a sea of weakly ionic-conducting PSS and a wide variation in the charge transport properties of PEDOT-PSS films is attributed to the degree of phasesegregation of the excess insulating polyanion. The magnetotransport and temperature dependent ac transport parameters across different conducting grades of PEDOT-PSS processed with DMSO were compared. Depending on the subtle alterations in morphology, the transport at low temperatures is shown to vary from the hopping regime (Baytron P) to critical regime of the metal-insulator transition (Baytron PH510) There is a significant positive magnetoresistance (MR) for P–films, but this is considerably less in case of PH510-film. From the low temperature ac conductance it is found that the onset frequency for PH510 is nearly temperature independent, whereas in P type it is strongly temperature dependent, again showing the superior transport in PH510. The presence of ‘shorter network connections’ together with a very weak temperature dependence down to ~ 5 K, suggest that the limitation on transport in PH510 arises from the connectivity within the PEDOT-rich grain rather than transport via the PSS barriers.
Chapter 4: DC and AC charge transport properties of Nafion s-MWNT and PANI-MWNT composites are studied. Such a detailed investigation is required to optimize the correlation among morphology and transport properties in these composites towards applications in field-effect transistors, antistatic coating, electromagnetic shielding, etc. The conductivity in Nafion s-MWNT shows a percolative transport with percolation threshold pc = 0.42 whereas such a sharp percolation is absent in PANI-MWNT composite since the conduction via PANI matrix smears out the onset of rapid increase in conductivity. Three-dimensional variable range hopping (VRH) transport is observed in Nafion s-MWNT composites. The positive and negative MR data on 10 wt. % sample are analyzed by taking into account forward interference mechanism (negative MR)
and wave-function shrinkage (positive MR), and the carrier scattering is observed to be in the weak limit. The electric-field dependence, measured to high fields, follows the predictions of hopping transport in high electric-field regime. The ac conductivity in 1 wt. % sample follows a power law: ( ) A s , and s decreases with increasing temperature as expected in the correlated barrier hopping (CBH) model. In general, Mott’s VRH transport is observed in PANI-MWNT samples. It is found that the MWNTs are sparingly adhered with PANI coatings, and this facilitates inter-tube hopping at low temperatures. The negative MR of MWNT-PANI composites suggest that the electronic transport at low temperatures is dominated by MWNT network. AC impedance measurements at low temperatures with different MWNT loading show that ac conductivity become temperature independent as the MWNT content increases. The onset frequency for the increase in conductivity is observed to be strongly dependent on the MWNT weight percentage, and the ac conductivity can be scaled onto a master
curve given by ( ) 0[1 k( 0 )s ].
Chapter 5: Organic field-effect transistors (OFETs) based on small molecules and polymers have attracted considerable attention due to their unique advantages, such as low cost of fabrication, ease of processing and mechanical flexibility. Impedance characterization of these devices can identify the circuit elements present in addition to the source-drain (SD) channel, and the bottlenecks in charge transport can be identified. The charge carrier trapping at various interfaces and in the semiconductor can be estimated from the dc and ac impedance measurements under illumination. The equivalent circuit parameters for a pentacene OFET are determined from low frequency impedance measurements in the dark as well as under light illumination. The charge accumulation at organic semiconductor–metal interface and dielectric semiconductor interface is monitored from the response to light as an additional parameter to find out the contributions arising from photovoltaic and photoconductive effects. The shift in threshold voltage is due to the accumulation of photogenerated carriers under SD electrodes and at dielectric–semiconductor interface, and also this dominates the carrier transport. Similar charge trapping is observed in an OFET with PBTTT as the active material. This novel method can be used to differentiate the photophysical phenomena occurring in the bulk from that at the metal-semiconductor interface for the polymer.
Chapter 6: The conclusions from the various works presented in the thesis are
coherently summarized in this chapter. Thoughts for future directions are also
summed up.
42
Lien, Hsiang-Ting, and 連香婷. "Surface Charateristics of Polymer-Dispersed Single-Wall Carbon Nanotubes for Transparent Conducting Film Application." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/9kfem2.
Full textAbstract:
碩士國立臺北科技大學
有機高分子研究所
97
Transparent electrodes are used in the electronic device such as touch screen, flat panel display, and solar cell technologies. While carbon nanotube(CNTs) electrodes show promise, characteristically poor dispersion properties have limited their practicality. In this study, we demonstrate a simple method for forming uniform carbon nanotube network electrodes directly deposited on the substrate by using spin coating. CNTs are more easily dispersed in chloric solvents in the presence of regioregular poly(3-hexylthiophene) (rr-P3HT). Due to the more conducting nature of these polymers compared with typical surfactants. By introducing conjugated polymers rr-P3HT to carbon nanotube suspensions in chlorobenzene, we significantly improve both the dispersion in solution and the quality of spin-coated CNT films on substrate.
43
Ravikumar, K. "Development of Multifunctional Biomaterials and Probing the Electric Field Stimulated Cell Functionality on Conducting Substrates : Experimental and Theoretical Studies." Thesis, 2015. http://etd.iisc.ac.in/handle/2005/3197.
Full textAbstract:
Materials with appropriate combinations of multifunctional properties (strength, toughness, electrical conductivity and piezoelectricity) together with desired biocompatibility are promising candidates for biomedical applications. Apart from these material properties, recent studies have shown the efficacy of electric field in altering cell functionality in order to elicit various cell responses, like proliferation, differentiation, apoptosis (programmed cell death) on conducting substrates in vitro. In the above perspective, the current work demonstrates how CaTiO3 (CT) addition to Hydroxyapatite (HA) can be utilised to obtain an attractive combination of long crack fracture toughness (up to 1.7 MPa.m1/2 measured using single edge V-notch beam technique) and a flexural strength of 155 MPa in addition to moderate electrical conductivity. The enhancement of fracture toughness in HA-CT composites has been explained based on the extensive characterization of twinned microstructure in CT along with the use of theoretical models for predicting the enhancement of toughening through crack tip tilt and twist mechanisms. Subsequent in vitro studies on HA-CT composites with human Mesenchymal Stem cells (hMSCs) in the presence of electric field has shown enhanced differentiation towards bone like cells (osteogenic lineage) as evaluated by ALP activity, Collagen content and gene expression analyses through Polymerase Chain Reaction (PCR) at the end of two weeks. he extracellular matrix mineralization analysis at the end of 4 weeks of hMSC culture further substantiated the efficacy of electric field as a biochemical cue that can influence the stem cell fate processes on conducting substrates. The electric field stimulation strategy was also implemented in in vitro studies with C2C12 mouse myoblast (muscle) cells on elastically compliant poly(vinylidene difluoride) (PVDF)-multiwall carbon nanotube (MWNT) composite substrates. PVDF is a piezoelectric polymer and the addition of MWNTs makes the composite electrically conducting. Upon, electric field stimulation of C2C12 mouse myoblast cells on these composites, has been observed that in a narrow window of electric field parameters, the cell viability was enhanced along with excellent cell alignment and cell-cell contact indicating a potential application of PVDF-based materials in the muscle cell regeneration. In an effort to rationalise such experimental observations, a theoretical model is proposed to explain the development of bioelectric stress field induced cell shape stability and deformation. A single cell is modelled as a double layered membrane separating the culture medium and the cytoplasm with different dielectric properties. This system is linearized by invoking Debye-Huckel approximation of the Poisson-Boltzmann equation. With appropriate boundary conditions, the system is solved to obtain intracellular and extracellular Maxwell stress as a function of multiple parameters like cell size, intracellular and extracellular permittivity and electric field strength. Based on the stresses, we predict shape changes of cell membrane by approximating the deformation amplitude under the influence of electric field. Apart from this, the shear stress on the membrane has been used to determine the critical electric field required to induce membrane breakdown. The analysis is conducted for a cell in suspension/on a conducting substrate and on an insulating substrate to illustrate the effect of substrate properties on cell response under the influence of external electric field.
44
Ravikumar, K. "Development of Multifunctional Biomaterials and Probing the Electric Field Stimulated Cell Functionality on Conducting Substrates : Experimental and Theoretical Studies." Thesis, 2015. http://hdl.handle.net/2005/3197.
Full textAbstract:
Materials with appropriate combinations of multifunctional properties (strength, toughness, electrical conductivity and piezoelectricity) together with desired biocompatibility are promising candidates for biomedical applications. Apart from these material properties, recent studies have shown the efficacy of electric field in altering cell functionality in order to elicit various cell responses, like proliferation, differentiation, apoptosis (programmed cell death) on conducting substrates in vitro. In the above perspective, the current work demonstrates how CaTiO3 (CT) addition to Hydroxyapatite (HA) can be utilised to obtain an attractive combination of long crack fracture toughness (up to 1.7 MPa.m1/2 measured using single edge V-notch beam technique) and a flexural strength of 155 MPa in addition to moderate electrical conductivity. The enhancement of fracture toughness in HA-CT composites has been explained based on the extensive characterization of twinned microstructure in CT along with the use of theoretical models for predicting the enhancement of toughening through crack tip tilt and twist mechanisms. Subsequent in vitro studies on HA-CT composites with human Mesenchymal Stem cells (hMSCs) in the presence of electric field has shown enhanced differentiation towards bone like cells (osteogenic lineage) as evaluated by ALP activity, Collagen content and gene expression analyses through Polymerase Chain Reaction (PCR) at the end of two weeks. he extracellular matrix mineralization analysis at the end of 4 weeks of hMSC culture further substantiated the efficacy of electric field as a biochemical cue that can influence the stem cell fate processes on conducting substrates. The electric field stimulation strategy was also implemented in in vitro studies with C2C12 mouse myoblast (muscle) cells on elastically compliant poly(vinylidene difluoride) (PVDF)-multiwall carbon nanotube (MWNT) composite substrates. PVDF is a piezoelectric polymer and the addition of MWNTs makes the composite electrically conducting. Upon, electric field stimulation of C2C12 mouse myoblast cells on these composites, has been observed that in a narrow window of electric field parameters, the cell viability was enhanced along with excellent cell alignment and cell-cell contact indicating a potential application of PVDF-based materials in the muscle cell regeneration. In an effort to rationalise such experimental observations, a theoretical model is proposed to explain the development of bioelectric stress field induced cell shape stability and deformation. A single cell is modelled as a double layered membrane separating the culture medium and the cytoplasm with different dielectric properties. This system is linearized by invoking Debye-Huckel approximation of the Poisson-Boltzmann equation. With appropriate boundary conditions, the system is solved to obtain intracellular and extracellular Maxwell stress as a function of multiple parameters like cell size, intracellular and extracellular permittivity and electric field strength. Based on the stresses, we predict shape changes of cell membrane by approximating the deformation amplitude under the influence of electric field. Apart from this, the shear stress on the membrane has been used to determine the critical electric field required to induce membrane breakdown. The analysis is conducted for a cell in suspension/on a conducting substrate and on an insulating substrate to illustrate the effect of substrate properties on cell response under the influence of external electric field.
45
"Preparation and Application of Conducting Polymer Carbon Nanotube Composite." East Tennessee State University, 2004. http://etd-submit.etsu.edu/etd/theses/available/etd-1110104-211520/.
Full text
46
Lin, Yen-Wen, and 林彥文. "Preparation and Characterization of Sulfonated Conducting Polymer/Carbon Nanotube Composites." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/87049952155409128270.
Full textAbstract:
博士國立中興大學
材料科學與工程學系所
98
The water-soluble sulfonated polyaniline (SPANI)/carboxylic groups containing multi-walled carbon nanotube (c-MWCNT) composites with core-shell tubular structure have been prepared by solution mixing of c-MWCNT and SPANI aqueous colloids. Fourier-transform infrared spectroscopy, Raman spectroscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), field- emission scanning (SEM) and high-resolution transmission electron microscopy (HRTEM) were used to characterize their structure and morphology of composites. The results of Raman, UV-Vis and XPS spectra revealed the presence of electrostatic interaction between the C-N+ species of the SPANI and the COO- species of the c-MWCNTs. The addition of c-MWCNTs can improve the thermal stability of SPANI specimens. The conductivity of 3 wt% SPANI/c-MWCNT composites at room temperature is sixteen times higher than that of SPANI. The above results demonstrate that the addition of a small number of c-MWCNTs into SPANI matrix can efficiently form a conducting network in the well dispersed composites, thus increasing the electrical properties of the composites. In addition, similar methodology has been applied to fabricate the water-soluble sulfonated polypyrrole (SPPy)/c-MWCNT composites by aqueous mixing of c-MWCNT dispersions and SPPy colloids. The electrochemical performances of these SPANI/c-MWCNT composites have been investigated using cyclic voltammetry and electrochemical impedance spectro- scopy. The incorporation of the c-MWCNTs to SAPNI increases the electrochemical activity of SPANI/c-MWCNT composite films and promotes the electron transfer of the redox processes. Furthermore, the presence of c-MWCNTs also leads to more active sites for electrochemical reactions and a faster electron transfer than pure SAPNI. In addition, the morphology of SPANI/c-MWCNT composites measured by SEM and atomic force microscopy indicates the presence of well-distributed tubular structures that are individually coated with ED-SPANI on the surface of composite films. The relatively rough topography of composite films would provide a large surface area for electrolyte access. Therefore, it is expected that the difference in the structure of the composite films can result in high electrochemical properties of the electrodes constructed from these composite films. The electrospinning process has been successfully used to fabricate ultrafine fibers consisting of the mixture of SPANI and poly(ethylene oxide) (PEO). The key factor of fiber formation with uniform size of fibers were dependent on the solution viscosity. The SEM images showed that the average diameter of SPANI/PEO electrospun fibers were evidently decreased with increasing loading of SPANI content. This trendency may be attributed to the increase in the net charge density of the solution with the presence of SPANI, which favors the formation of thin fibers. The conductivity of SPANI/PEO electrospun fibers fabricated with the weight ratio of SPANI/PEO at 0.33 is about five times of magnitude higher than that of electrospun fibers with SPANI/PEO at 0.2. In addition, conducting composite fibers were also obtained through electro- spinning of SPANI/PEO solution containing different contents of c-MWCNTs. HRTEM images confirmed that the c-MWCNTs were encapsulated within the fibers as individual elements, mostly aligned along the fiber axis. The measured results showed that the electrical conductivity of the electrospun fiber mats improved with increasing the content of c-MWCNTs.
47
Wang, Shih-Han, and 王仕漢. "Conductivity Research on the Conducting Polymer of Multi-Walled Carbon Nanotube/Conducting Carbon Black Composite." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/93035965255774283099.
Full textAbstract:
碩士國立交通大學
工學院半導體材料與製程產業專班
96
The polymer of extrinsically conducting polymer (ECP) can not conduct electricity, so it needs to add electricity conducting fillers to make it conduct electricity. In this study, Carbon black-Polydimethyl siloxane (CB-PDMS) and Carbon nanotube-Polydimethyl siloxane (CNT-PDMS) can be fabricated to become nano composites by high shear force mixing synthesis. Furthermore, the relation between the degree of dispersion and electric conductivity by adding different proportion of CNT, CB and dispersant will also be discussed. Polymeric dispersants that comprise an anchoring group and a binder-compatible chain, can be used in the surface modification of nano-sized particles. After surface modification, the nano particle can disperse in polymer uniformly and promote the electric conductivity. Scientific evidence proves that the best proportion of CNT is 3wt%, and the electrical conductivity may promote to 10-1 S/cm; the best proportion of CB is 30wt%, and the electrical conductivity may promote to 10-4 S/cm. The dispersant reached 30wt% of conductor can not only promote the electrical conductivity of ECP, but also make the conductor disperse stably in polymer. When the proportion of dispersant reaches 30wt% of conductor, the electrical conductivity of conducting polymer with dispersant still maintains its dispersible characteristic after 8 weeks.
48
Moriarty, Gregory P. "Tailoring the Thermoelectric Behavior of Electrically Conductive Polymer Composites." Thesis, 2013. http://hdl.handle.net/1969.1/151038.
Full textAbstract:
Numerous alternative energy sources are being researched for sustainable energy applications, but their overall benefit is still too costly for them to be considered viable. Commonly produced temperature gradients created by the environment, or are man-made, can be converted into useful energy by using thermoelectric materials. Inorganic semiconductors are the most commonly used thermoelectric materials, but have raised concerns due to toxicity issues, rarity of heavy elements used, and high fabrication temperatures. These concerns have led research efforts into electrically conductive polymer composites prepared in ambient conditions from aqueous solutions. By combining polymer latex with carbon nanotubes (CNT), electrical conductivity can resemble metals while thermal conductivity remains similar to polymers. Using different CNT stabilizers for these fully organic composites can tailor the thermoelectric properties and harvest thermal gradients from previously inconceivable places (e.g., body heat converted into a voltage).
A semiconducting CNT stabilizer, meso-tetra(4-carboxyphenyl) porphine (TCPP), was used to investigate the influence stabilizers have on composite thermoelectric properties. As TCPP was compared to a similar system containing an insulating stabilizer, sodium deoxycholate (DOC), the multi-walled carbon nanotube (MWNT)-filled composites showed a 5x increase in the Seebeck coefficient (S). TCPP did not have a distinct effect on the electrical conductivity (σ), demonstrating the tailorability of S with this molecule.
An intrinsically conductive polymer, poly(3,4-ethylenedioxythiophene) :poly(styrene sulfonate) (PEDOT:PSS), was used to stabilize highly conductive double-walled carbon nanotubes (DWNT) and demonstrate the promise of fully organic composites as thermoelectric materials. This combination of CNT and stabilizer produced metallic electrical conductivity (200,000 S m-1) and power factors (S2σ) within an order of magnitude of commonly used semiconductors (~400 μW m-1 K-2). Electrical conductivity was doubled by stabilizing single-walled carbon nanotubes (SWNT) with PEDOT:PSS in a thin film without the insulating polymer latex.
To further demonstrate the tailorability of polymer composites, a dual stabilizer approach using semiconducting and intrinsically conductive stabilizers was used. This approach effectively provided the high electrical conductivity from PEDOT:PSS and the enhanced Seebeck coefficients of TCPP. By using multiple stabilizers for CNTs within the same composite, power factors among the highest reported for fully organic composites are achieved (~500 μW m-1 K-2). These water-based, flexible composites are becoming real competition as their conversion efficiencies, when normalized by density, are similar to commonly used semiconductors.
49
Shien, Lu-Chien, and 呂建賢. "The Conducting Polymer-Carbon Nanotube Composites and Their Applications in Thermoelectrics." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/44177264833678973101.
Full text
50
Chuang, Su-han, and 莊舒涵. "Pt-Sn on conducting polymer modified carbon nanotube for ethanol oxidation." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/63156872592293205319.
Full textAbstract:
碩士國立中央大學
化學研究所
100
Catalytic activity of ethanol oxidation reaction is the most critical property dictating ethanol fuel cell performance. In addition to the metal nano-particle, the support material which fixes the nano-catalysts also contributes to the catalytic activity. The most common and widely used catalyst support is carbon black and carbon nanotube. However, the nano-catalysts tend to aggregate during reaction on the smooth graphene-like surface. Recently, there has been numerous report of heterogeneous catalysis that uses nitric acid to functionalize carbon nano-tubes surface which circumvent these deficiencies by forming CNx（nitrogen-doped carbon (CNx) nanotubes. Wrapping carbon nanotube with conducting polymers was recently explored to disperse metallic particles. When metallic platinum and compounds of transition metals are immobilized in the conducting polymer layer, the catalysts system delivered high electronic and protonic conductance, durable thermal stability, higher hydrophilicity, larger specific surface area, and considerable increase in active surface area. Current study demonstrated a novel support based on polyaniline-coated carbon nanotubes can substantially enhance ethanol oxidation activity and mitigate the problems of aggregation and leaching out related to Pt, Pt-Ru or Pt-Sn nano-catalysts. The Pt-Sn nanoparticle supported on PANICNT is sharply distributed with particle sizes ranging from 2.0 to 4.0 nm. For comparison, Pt-Sn particles loaded on bare CNT and XC-72 shows worse dispersion with larger particle size and lower surface area. This is attributed to the presence of strong Pt-N chelating bond between the nano-paticle with the nitrogen on polyaniline. The current densities derived from cyclovoltametry indicated PtSn/PANICNT yielded distinctively higher value （748.7 A g-1 Pt），which is 458.9 A g-1 Pt higher compared to PtSn/CNT without PANI functionalization. Through accelerated degradataion test（ADTs）, the novel catalysts system maintains 77.8 % or the current output after 5000 cycles, thus demonstrated its superior electrochemical stability compared to other supports. This study confirms Pt-Sn binary catalysts support on PANICNT yields superior catalytic activity for ethanol oxidation, higher Pt utilization efficiency, and displayed much better life-time durability when compared to that of PtSn/CNT or PtSn/XC-72. In second part of the work, we compared PtSn/PANICNT catalysts prepared by four different methods：EG- PtSn/PANICNT (ethylene glycol as solvent)、FA- PtSn/PANICNT(formic acid as solvent)、pH12- PtSn/PANICNT (ethylene glycol solvent at PH=12) and R- PtSn/PANICNT (NaBH4 as reducing agent). The result shows higher pH deteriorates the particle quality, while NaBH4 is too strong a reducing agent leading to particle aggregation. Ethylene glycol as a mild reducing agent, provided the best nanao-catalysts growth condition which lead to best Pt-Sn particle dispersion and most homogeneous particle size distribution. Cyclic voltammetry measurement shows EG- PtSn/PANICNT displayed the best electrochemical active surface area （ECSA）and highest catalytic activity for ethanol oxidation.