Дисертації: "Electrical Properties - Nanocomposites"

1

Schiţco, Cristina. "Thermal and electrical properties of PVDF/Cu nanocomposites." Master's thesis, Universidade de Aveiro, 2011. http://hdl.handle.net/10773/7531.

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Mestrado em Ciência e Engenharia de Materiais
Poly(vinylidene fluoride) (PVDF) nanocomposites films with spherical and 1 Dimension (1D) copper nanoparticles as fillers were prepared; the morphology, dielectric properties, and thermal conductivity were studied. The role of dimensionality of the fillers was assessed and discussed. Spherical or nanowires copper nanoparticles were incorporated into the polymeric matrix up to 0.30 wt % via solution casting from dimethylformamide DMF, which acts as a good solvent for PVDF. The obtained films were shown to be porous when investigated by Scanning Electron Microscopy (SEM). The porosity of the films was eliminated by a hot pressing step. Fourier transform infrared (FTIR) and Raman spectroscopy investigations indicated the formation of γ-phase in the pure polymer as for polymer matrix for both spherical and nanowires copper nanoparticles loading. The presence of Cu in the polymer matrix was only detected for high nanoparticles contents by UV-Vis spectroscopy and X Ray Diffraction (XRD). The crystallization of the polymer was not significantly affected in the case of Cu spheres nanoparticles loading. For Cu nanowires, an increase of the degree of crystallization (ΔXc) with Cu loading was observed (pressed samples). The dielectric and thermal conductivity measurements showed a significant improvement of the dielectric constant and thermal conductivity compared to pure PVDF. When the loading of Cu nanoparticles equals to 0.30%, the dielectric constant and thermal conductivity of the nanocomposites incorporating spherical particles is ~20 at 103 Hz and 0.39 W/mK, respectively. However and particularly interesting this effect is more noticeable for Cu nanowires nanocomposites for which the dielectric constant and the thermal conductivity reached values of 24.4 at 103 Hz and 0.45 W/mK, respectively. These results, until now not reported in the literature, have a unique relevance for future applications of PVDF as electric stress control, electromagnetic shielding and high storage capability of the electric energy devices.
Neste trabalho foram preparados filmes nanocompósitos de poli (fluoreto de vinilideno) (PVDF) com nanoesferas e nanofios de cobre. Foram estudadas a morfologia, propriedades dieléctricas e condutividade térmica. O papel da dimensionalidade do enchimento (fillers) foi avaliado e discutido. As nanopartículas esféricas ou nanofios de cobre foram incorporados na matriz polimérica até 0,30% em peso, através da conformação de soluções de dimetilformamida (DMF). Os filmes obtidos mostraram-se porosos quando analisados por microscopia electrónica de varrimento (SEM). A porosidade dos filmes foi eliminada por uma etapa de prensagem a quente. Espectroscopias de Infravermelho (FTIR) e Raman indicaram a formação da fase γ na matriz polimérica para ambos os tipos de fillers, nano esferas e nanofios de cobre. A presença de Cu na matriz do polímero só foi detectada por espectroscopia UV-VIS e Difracção de raios X (XRD) para altos teores de nanopartículas. A cristalização do polímero não foi significativamente afectada no caso da carga com nanoesferas de Cu. Contudo, foi observada um aumento do grau de cristalização (ΔXc) com a carga para os nanofios de Cu (amostras prensadas). Medições da resposta eléctrica e térmica revelaram uma melhoria significativa da constante dieléctrica e da condutividade térmica em comparação com PVDF puro. Quando a carga de nanopartículas de Cu equivale a 0,30%, a constante dieléctrica e a condutividade térmica dos nanocompósitos com partículas esféricas é de aproximadamente 20 a 103 Hz e 0,39 W/mK, respectivamente. No entanto, e particularmente interessante, este efeito é mais evidente para os nanocompósitos com nanofios de Cu, para os quais a constante dieléctrica e a condutividade térmica atingem valores de 24,4 a 103 Hz e 0,45 W/mK, respectivamente. Estes resultados, até agora não reportados na literatura, são de relevância para futuras aplicações de PVDF em dispositivos controladores de stress eléctrico, de blindagem electromagnética e de alta capacidade de armazenamento de energia eléctrica.

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2

Lau, K. Y. "Structure and electrical properties of silica-based polyethylene nanocomposites." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/358889/.

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The topic of polymer nanocomposites remains an active area of research in the dielectrics community, due to the unique electrical properties that these materials could exhibit. To explain the behaviour of these materials, the importance of clarifying the interfaces between nanoparticles and polymer matrices has been emphasised. However,understanding of the interface in nanocomposites is unsatisfactory and, consequently,many experimental results remain unexplained. This thesis reports on an investigation into a polyethylene nanocomposite system that contains varying amounts of nanosilica that differ with respect to their surface chemistry. The addition of nanosilica, even with different surface chemistries, was found to enhance the nucleation density of polyethylene and perturb the spherulitic development. While less organised lamellar structures would be expected to lead to a lower breakdown strength, this does not appearto be the case for the material systems considered here under alternating current (AC) fields. In addition, nanosilica filled polyethylene was found to absorb significantly more water than unfilled polyethylene, with the consequence that both the permittivity and the loss tangent increase with increasing duration of water immersion. However, appropriate surface treatment of nanosilica reduces the water absorption effect and modifies the dielectric response of the nanocomposites compared with those containing an equivalent amount of untreated nanosilica. Although water absorption may not be a technologically desirable characteristic, the results indicate that water molecules can act as effective dielectric probes of interfacial factors. Meanwhile, the direct current (DC) breakdown strength reduces with the inclusion of increasing amount of nanosilica in the polyethylene, but surface treatment of nanosilica improves the DC breakdown strength with respect to equivalent nanocomposites containing untreated nanosilica. Results from space charge studies reveal increased space charge accumulation in the presence of the untreated nanosilica and, upon surface treatment of the nanosilica, the charge development was suppressed in comparison with nanocomposites containing an equivalent amount of untreated nanosilica. This observation suggests that space charge accumulation and DC failure are related in these systems and it would seem that control of surface chemistry is particularly critical in connection with the use of nanocomposites in DC applications. Finally, the mechanisms underpinning the concept of filler functionalisation in nanocomposites were investigated via the use of different aliphatic chain length silane coupling agents, and the results show that long silane chains enhance the DC breakdown strength of the resulting nanocomposites. The possible further enhancement in DC breakdown strength is also highlighted. Overall, this thesis demonstrates how a nanoparticle’s interface chemistry can affect both the structure and the electrical properties of the resulting nanocomposites, and serves as an important foundation towards the engineering of nanocomposites as the reliable electricalinsulation materials of the future, through the understanding of the interface.

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3

Zhang, Guoqiang. "The Synthesis and Electrical Properties of Functional Polymer Nanocomposites." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case149010222646324.

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4

Lim, Chee-Sern. "Mechanical and electrical properties of aligned carbon nanofiber/epoxy nanocomposites." Thesis, Wichita State University, 2010. http://hdl.handle.net/10057/3315.

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Carbon Nanofibers (CNFs) are high aspect ratio nanofillers that possess excellent mechanical and electrical properties. Hence, CNFs have been incorporated into polymer to fabricate nanocomposites with superior mechanical and electrical properties. Studies have shown that nanocomposites with superior mechanical and electrical properties can be fabricated with relatively low concentration of nanofillers by properly aligning them in polymer resins through AC electric field. In this work, functionalized CNFs have been incorporated into a high-strength epoxy-based resin and aligned into a preferential direction using AC electric field to tailor aligned carboxylic-functionalized CNFs (O-CNFs) and amine-functionalized CNFs (A-CNFs) reinforced polymeric nanocomposites. Both mechanical and electrical properties were quantified in order to examine the effect of addition and alignment of functionalized CNFs on the properties of final nanocomposites. Optical images revealed negligible agglomeration before and after curing of nanocomposites, at the same time, they showed alignment arrays of functionalized CNFs in the nanocomposites that were subjected to AC electric field. Additionally, the configuration of alignment for low concentration of aligned O-CNFs and A-CNFs filled nancomposites was slightly different compare to aligned nanocomposites with high concentration possibly due to elevated localized interaction of adjacent functionalized CNFs. An increase of 11.34% in compressive modulus and 8.36% in compressive strength were achieved when adding 3wt% and 4.5wt% of O-CNFs to the base resin system, respectively. By comparing different concentration of aligned and non-aligned A-CNFs reinforced nanocomposites correspondingly, it was found that the percentage change of compressive modulus for aligned A-CNFs filled samples was two to three times higher than nonaligned samples. Meanwhile, a four order magnitude of reduction in electrical resistivity to 10⁶ Ω.cm was obtained by aligning the functionalized CNFs in the epoxy resin. Furthermore, the electrical percolation threshold of aligned O-CNFs filled nanocomposites was estimated to be 0.75wt%. A possible trend of electrical resistivity of aligned A-CNFs filled nanocomposites was extrapolated up to 4.5wt% and suggested that the percolation threshold of electrical resistivity would occur at 0.75wt%, which is similar to aligned O-CNFs nanocomposites. Moreover, it is also suggested that the electrical resistivity of 4.5wt% aligned A-CNFs filled nanocomposites would reduce to 10⁴ Ohm.cm range.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.

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5

Maruzhenko, Oleksii. "Structure, thermal and electrical properties of nanocomposites with hybrid fillers." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI131.

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Isolante. On a étudié les processus de formation d'une structure ségrégée, qui conduisait à la formation d'une distribution ordonnée de particules dans une matrice polymère. Il est montré que dans le système ségrégé, la valeur du seuil de percolation φc est d'un ordre de grandeur inférieur à celui d'un composite présentant une distribution aléatoire des charge (2,95% vol. pour le composite ségrégé contre 24,8% vol. pour le composite à distribution aléatoire). Le seuil de percolation dans le cas d'un mélange de charges est très inférieur à la valeur calculée à l'aide de la règle des mélanges. Il est montré que les résultats expérimentaux de conductivité thermique ne révèlent pas de comportement de percolation et peuvent être décrits de façon satisfaisante par le modèle de Lichtenecker. La valeur du paramètre λf traduisant la conductivité thermique de la charge en tenant compte de l’interface charge/matrice est de 4,4 fois plus élevé pour les systèmes ségrégés que pour un composite à distribution aléatoire de particules. Il est montré que dans les systèmes ségrégés, les paramètres de blindage sont considérablement augmentés en raison de l'absorption provoquée par la réflexion interne sur les parois conductrices du réseau de charges conductrices. Il est établi que les charges de carbone constituent la base la plus efficace, ce qui garantit une absorption élevée des rayonnements électromagnétiques (REM) aux faibles concentrations. Il est avéré que le plus grand effet de blindage est observé pour un mélange de charges hybrides GNP/CNT (nanoplaques en graphite / nanotubes de carbone). L'effet de synergie s'explique par la meilleure interaction du REM avec le réseau hybride ramifiée formés par les charges, ce qui entraîne une absorption accrue du REM. Les systèmes à structure ségrégée à base d'élastomères présentent un effet piézorésistif prononcé avec une relation linéaire de déformation / modification de l'intensité du courant. L'étude de l'effet piézorésistif dans une large gamme de température (-40 / +50°С) a montré la stabilité des caractéristiques principales et la possibilité d'utiliser le composite dans une large gamme de températures
The thesis determines the principles of the conductive phase structure formation in polymer composites containing conductive fillers, which will be different types of carbon fillers. The processes of segregated structure formation in which the particles of the filler are localized on the surfaces of polymer grains is studied. It is shown that the value of the percolation threshold φc for the segregated system is one order lower than in the composite with a random distribution of the filler 2.95 vol.% and 24.8 vol.%, respectively. The hybrid filler shows percolation threshold, much lower than the value calculated using the mixing rule. Experimental results of thermal conductivity for systems filled with anthracite, graphene and hybrid filler Gr/A do not reveal percolation behaviour and can be well described by the Lichtenecker model. It is shown that λf for segregated systems is 4.4 times higher than for a composite with a random distribution of filler particles. It is shown that in segregated systems the shielding parameters are significantly increased due to the absorption caused by the internal reflection on the conductive walls of the filler framework. Carbon fillers create the most effective basis that ensures a high absorption rate of EMI at low concentrations. It was found that the greatest shielding effect in the interaction of a composite with electromagnetic radiation was observed for the hybrid filler GNP/CNT (graphite nanoplatelets/carbon nanotubes). The synergistic effect is explained not by their higher electrical conductivity, but by the better interaction of the EMI with the developed hybrid framework of the filler, which causes increased absorption of the EMI. Systems with a segregated structure based on elastomer (ground rubber) with a polymer-adhesive and hybrid electroconductive nano-fillers exhibit a significant piezoresistive effect. The cyclic studies of electric response, depending on the applied external load, showed a linear relationship between composite deformation and current changes through the sample and demonstrate stable long-term stability. The study of the piezoresistive effect in a wide temperature range (-40 ÷ +50°C) showed the stability of the main characteristics and the possibility of exploiting the composite in a wide temperature range

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6

Noël, Amélie. "Electrical properties of film-forming polymer/graphene nanocomposites : Elaboration through latex route and characterization." Thesis, Saint-Etienne, EMSE, 2014. http://www.theses.fr/2014EMSE0767/document.

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Les dispersions de nanocomposite à base aqueuse sont produites pour des applications diverses telles que les adhésifs, les revêtements et plus récemment les encres. Ce projet consiste à réaliser des encres conductrices nanocomposites comprenant des particules de polymère (latex) à basse température de transition vitreuse, Tg, pour la formation de films à température ambiante, et des plaquettes de graphène, en raison de leurs excellentes propriétés conductrices. Les charges conductrices, appelées multi-feuillets de graphène, sont réalisées par broyage en voie aqueuse de graphite (1-10 µm) stabilisées par différents tensio-actifs et/ou stabilisants. Cette méthode sans solvant et à bas coût permet de produire des suspensions de multi-feuillets (1-10 feuillets) de graphène. Les particules de polymères utilisées sont synthétisées par polymérisation en émulsion de monomères acrylates. Dans un second temps, des mélanges physiques de suspensions de graphène et de latex acrylates ont permis d’obtenir des encres nanocomposites. L’ajout de graphène permet l’obtention d’un seuil de percolation à bas taux de charge et une nette amélioration des propriétés électriques et du renfort. Le diamètre des billes de latex a une influence importante sur ces propriétés et a également été étudié. Afin d’augmenter la stabilité des suspensions et les interactions graphène/latex, des nanocomposites structurés ont été synthétisés par polymérisation in situ en émulsion, miniemulsion ou dispersion en présence de graphène. Les excellentes propriétés électriques associées à leur flexibilité font de ces matériaux des candidats adaptés pour la réalisation d’encres conductrices pour impression sur textile
Printed electronics, particularly on flexible and textile substrates, raised a strong interest during the past decades. This project presents a procedure that provides a complete and consistent candidate for conductive inks based on a graphene/polymer nanocomposite material. It consists in the synthesis of conductive inks nanocomposites comprising polymer particles (latex) with low glass transition temperature, Tg, and graphene platelets, for the conductive properties. The conductive particles, named Nanosize Multilayered Graphene (NMG), are prepared by wet grinding delamination of micro-graphite suspensions stabilized by various surfactants and/or polymeric stabilizers. This solvent-free procedure allows the formation of NMG suspensions with low thickness (1-10 sheets). Polymer particles are synthetized by surfactant-free emulsion polymerization with acrylates monomers.Physical blending of latex particles and NMG platelets are performed to obtain conductive nanocomposites inks. Adding NMG induce a low percolation threshold and a sharp increase of the electrical and mechanical properties of the nanocomposites. Moreover, the polymer particles diameters have an impact on these properties.To increase the formation of a well-defined cellular microstructure, the nanocomposites are also synthetized by in situ polymerization in presence of NMG platelets, using emulsion, miniemulsion or dispersion polymerization. The excellent electrical properties of these nanocomposites associated to their flexibility make these materials suitable candidates for the production of conductive inks for textile printing applications

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7

MINNAI, CHLOE'. "OPTICAL AND ELECTRICAL PROPERTIES OF METAL POLYMER NANOCOMPOSITES FABRICATED WITH SUPERSONIC CLUSTER BEAM IMPLANTATION." Doctoral thesis, Università degli Studi di Milano, 2018. http://hdl.handle.net/2434/637068.

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Clusters are aggregates composed of a countable number of atoms or molecules, starting with the dimer and reaching, with a vaguely defined upper bound of several hundred thousand atoms, into that interesting size range. Clusters have properties that are different from both atoms and bulk materials as in these small aggregates the surface-to-volume ratio is very large and hence the surface atoms, play a dominant role compared to the bulk ones. By assembling preformed clusters, one can build nanostructured materials. These can be divided in two main categories: cluster assembled films and nanocomposites. In the former case nanoparticles are deposited on a substrate in the latter they are incorporated in a matrix, a polymer for instance. Nanostructured materials offer exciting pathway for the construction of macroscopic materials with designer-specified optical, electrical, and catalytic properties which reflect the ones of their building blocks. The object of this thesis is the study of the optical and electrical properties of metal-polymer nanocomposites (MPNs) in response to mechanical deformation. Reflectance of MPNs is also exploited to develop reflective and bendable diffracting gratings which can be adapted to concave surfaces in order to add focusing power to the diffracting one. A further study regards the evolution of the electrical resistance during the growing of the nanostructured materials on different substrates. Then, the electrical properties of the systems in response to a voltage applied are explored, to find if peculiar phenomena such as resistance switching could occur. Recipes to fabricate robust and reproducible devices which exhibit controllable resistance switching were developed, both for cluster-assembled thin films and MPNs; in this latter case the possibility of controlling the switching activity with mechanical bending is demonstrated as well.

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8

DeGeorge, Vincent G. "Chemical Partitioning and Resultant Effects on Structure and Electrical Properties in Co-Containing Magnetic Amorphous Nanocomposites for Electric Motors." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/885.

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chemical partitioning of Cobalt-containing soft magnetic amorphous and nanocomposite materials has been investigated with particular focus on its consequences on these materials’ nanostructure and electrical resistivity. Theory, models, experiment, and discussion in this regard are presented on this class of materials generally, and are detailed in particular on alloys of composition, (Fe65Co35)79.5+xB13Si2Nb4-xCu1.5, for X={0- 4at%}, and Co-based, Co76+YFe4Mn4-YB14Si2Nb4, for Y={0-4at%}. The context of this work is within the ongoing efforts to integrate soft magnetic metal amorphous and nanocomposite materials into electric motor applications by leveraging material properties with motor topology in order to increase the electrical efficiency and decrease the size, the usage of rare-earth permanent magnets, and the power losses of electric motors. A mass balance model derived from consideration of the partitioning of glass forming elements relates local composition to crystal state in these alloys. The ‘polymorphic burst’ onset mechanism and a Time-Temperature- Transformation diagram for secondary crystallization are also presented in relation to the partitioning of glass forming elements. Further, the intrinsic electrical resistivity of the material is related to the formation of virtual bound states due to dilute amounts of the glass forming elements. And lastly, a multiphase resistivity model for the effective composite resistivity that accounts for the amorphous, crystalline, and glass former-rich amorphous regions, each with distinct intrinsic resistivity, is also presented. The presented models are validated experimentally on the Co-containing alloys by Atom Probe Tomography performed through collaboration with Pacific Northwestern National Laboratory.

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9

Jung, de Andrade Mônica. "Study of electrical properties of 2- and 3-dimensional carbon nanotubes networks." Toulouse 3, 2010. http://thesesups.ups-tlse.fr/1288/.

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Des réseaux bi- et tridimensionnels de nanotubes de carbone (2D- et 3D-CNTNs) ont été préparés sur substrat de silice amorphe et dans une matrice silice. Les aptitudes de plusieurs types de CNTs (mono-, double- et multi-parois : SWCNTs, DWCNTs et MWCNTs) à former un réseau percolant ont été comparées par mesure de la conductivité électrique (EC) de suspensions dynamiques de ces CNTs dans le chloroforme. Les suspensions de SWCNTs présentent une EC normalisée maximale (3. 08 S. Cm2/g) d'où leur choix pour les 2D-CNTNs tandis que les suspensions de DWCNTs ont le plus faible seuil de percolation (0. 002-0. 06 vol. %) d'où leur choix pour les 3D CNTNs. Pour les 2D-CNTNs, des suspensions aqueuses de SWCNTs (avec surfactant et sonication par sonde (PS)) ont été déposées par trempage, filtration, spray et dépôt électrophorétique. La plupart des 2D-CNTNs forment un réseau percolant dont EC obéit à la loi de puissance (exposant d'environ 1,29). Leurs conductance de surface et transparence dans l'UV permettent leur utilisation dans les écrans d'affichage, les écrans tactiles, les tubes cathodiques et la dissipation des charges électrostatiques. Les CNTNs les plus lisses sont intéressants pour les cellules solaires. Les 3D-CNTNs (nanocomposites) ont été préparés par sol-gel avec des DWCNTs modérément fonctionnalisés (avec/sans séchage) dispersés par PS, puis densifiés par "spark-plasma sintering". La voie sèche conduit au plus faible seuil de percolation (0,35 vol. % DWCNT) alors que le matériau le plus conducteur de la voie humide présente une EC de 1,56 S/cm (6,43 vol. % DWCNT). Les EC sont suffisantes pour l'évacuation des charges électrostatiques ou pour servir d'éléments chauffants
Two and three dimensional carbon nanotube networks (2D- and 3D-CNTNs) were prepared over silica glass substrate and in silica matrix, respectively. The aptitudes of various CNTs (single-, double- and multi-walled CNTs: SWCNTs, DWCNTs and MWCNTs, respectively) to form percolating CNTNs were compared by measurement of their electrical conductivity (EC) in dynamic suspensions in chloroform. The SWCNTs suspensions show the highest maximum normalized EC (3. 08 S. Cm2/g) while the DWCNTs ones have the lowest percolation thresholds (0. 002-0. 06 vol. %). This led to choose SWCNTs for 2D-CNTNs and DWCNTs for 3D ones. To produce 2D-CNTNs, SWCNTs aqueous suspensions (prepared with surfactant and probe sonication, PS) were deposited over the substrates through: dip-coating (DC), filtration (FM), spray-coating (SC) and electrophoretic deposition (ED). Most of the 2D-CNTNs formed a percolating CNTN whose EC follow the power law (exponent ~1. 29). Their surface conductance and UV transparency allow their use in displays, touch screens, shielding in cathode tubes and electrostatic dissipation. The smoothest CNTNs obtained by DC and ED are also interesting for solar cells. The 3D-CNTNs were prepared by sol-gel route using mildly functionalized DWCNTs (with/without dry step) dispersed with PS. The nanocomposites were fully densified by spark-plasma sintering. The "Dry" route allowed the lowest percolation threshold (0. 35 vol. % DWCNT), while the more conductive material from "Wet" route shows EC of 1. 56 S/cm (6. 43 vol. % DWCNTs). Besides the dispersion of CNTs could be improved, the achieved EC of these nanocomposites is high enough for their use in anti-electrostatic or heating applications

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10

Takele, Haile [Verfasser]. "Optical and electrical properties of metal-polymer nanocomposites prepared by vapor-phase co-evaporation / Haile Takele." Kiel : Universitätsbibliothek Kiel, 2009. http://d-nb.info/1019810459/34.

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11

Houssat, Mohammed. "Nanocomposite electrical insulation : multiscale characterization and local phenomena comprehension." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30211.

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Анотація:

Dans le domaine de l'isolation électrique, il a été démontré que les matériaux hybrides organiques/inorganiques nanocomposites (NC) assurent une nette amélioration de leur fonctionnement à haute température/haute tension et permettent aux systèmes d'isolation électrique de renforcer leurs propriétés diélectriques. Récemment, il a été démontré que certaines modifications des propriétés électriques telles que la permittivité, la rupture diélectrique, la résistance aux décharges partielles ou la durée de vie étaient souvent attribuées à l'interphase nanoparticule/matrice, une région où la présence des nanoparticules modifie les propriétés de la matrice. De plus, des études récentes montrent qu'une fonctionnalisation de la surface des nanoparticules permet une meilleure dispersion dans la matrice hôte. Cette meilleure dispersion affecte la zone d'interphase et joue également un rôle majeur dans l'amélioration des propriétés des nanocomposites. Cependant, le rôle de l'interphase reste théorique et peu de résultats expérimentaux existent pour décrire ce phénomène. Par conséquent, en raison de l'échelle nanométrique de l'interphase, une caractérisation de ses propriétés demeure un défi. Au cours de cette thèse, deux études principales sont menées afin de mieux comprendre la relation structure-propriété dans les polymères nanocomposites. Tout d'abord, la microscopie à force atomique (AFM) est utilisée pour effectuer simultanément des mesures qualitatives et quantitatives de ces zones d'interaction dans le nanocomposite polyimide/nitrure de silicium (PI/Si3N4). Le mode Peak Force Quantitative Nano Mechanical (PF QNM) dérivé de l'AFM révèle la présence de l'interphase en mesurant les propriétés mécaniques (module de Young, déformation ou adhérence). Le mode microscopie à force électrostatique (EFM) est utilisé pour détecter et mesurer la permittivité locale de la matrice et de l'interphases. Par ailleurs, l'objectif de ce travail est de présenter l'effet de la fonctionnalisation de surface des nanoparticules de nitrure de silicium (Si3N4) sur les régions d'interphase. Ces résultats quantitatifs, à la fois mécaniques et électriques, permettent de comparer la dimension et les propriétés des interphase autour des nanoparticules traitées et non traitées. Par conséquent, cette nouvelle approche de caractérisation de cette zone confronte les résultats expérimentaux à des modèles théoriques. Un nouveau modèle basé sur les résultats expérimentaux obtenus est proposé. De plus, la deuxième partie de cette étude présente une caractérisation macroscopique des propriétés et de la rigidité diélectrique des films de polyimide pur, du nanocomposite avec des particules traitées et non traités. Les résultats révèlent le rôle de l'interphase sur la réduction du phénomène de polarisation de l'électrode (PE) dû aux mouvements ioniques surtout à haute température. Pour les nanoparticules non traitées, ces effets sont moins importants en raison de la formation d'agrégats. En revanche, une diminution nette de la PE est obtenue en fonctionnalisant la surface des nanoparticules avec le silane comme agent de couplage. Enfin, la rigidité diélectrique de l'ensemble des échantillons est mesurée et montre une augmentation considérable de la performance diélectrique des nanocomposites à haute température par rapport au PI pur
In the electrical insulation field, it was demonstrated that nanocomposite (NC) organic/inorganic hybrid materials assure a distinct improvement of their high temperature/high voltage functioning and allow the electrical insulation to strengthen its dielectric properties. Recently, it was shown that some modifications of the electrical properties such as permittivity, dielectric breakdown, partial discharges resistance or lifetime are often awarded to the nanoparticle/matrix interphase, a region where the presence of the nanoparticle changes the matrix properties. Moreover, recent studies show that the nanoparticle surface functionalization allows a better dispersion of the particles within the host matrix. This better dispersion affects the interphase zone and plays a major role in the nanocomposite properties improvement as well. However, the role of the interphase remains theoretical and few experimental results exist to describe this phenomenon. Accordingly, because of its nanometer scale, the interphase properties characterization remains a challenge. Two main studies are carried out, during this thesis work, that can provide a better understanding of structure-properties relationships in polymer nanocomposite. First, Atomic Force Microscopy (AFM) is employed to make at the same time qualitative and quantitative measurements of these interaction zones within Polyimide/Silicon Nitride (PI/Si3N4) nanocomposite. The Peak Force Quantitative Nano Mechanical (PF QNM) AFM mode reveals the presence of the interphase by measuring mechanical properties (Young modulus, deformation or adhesion). Electrostatic force microscope (EFM) mode is used in order to detect and measure the matrix and interphase local permittivity. Moreover, the aim of this work is to present the effect of the surface functionalization of silicon nitride (Si3N4) nanoparticles on the interphase regions. Mechanical and electrical quantitative results permit comparing the interphase dimension and properties between treated and untreated Si3N4 nanoparticles. As a result, this new approach to characterize the nanocomposite interphase zone using local measurements confronts experimental results with theoretical models. A new model based on the obtained experimental results is proposed. In addition, the second part of this study presents a macroscopic investigation on the dielectric properties and breakdown strength of neat polyimide, untreated and treated nanocomposite films. Results reveal the interphase role on the reduction of the electrode polarization (EP) phenomenon due to ionic movements especially at high temperatures. For untreated nanoparticles, these effects are less important due to the aggregate formation. In contrast, an EP drastic decrease is obtained by functionalizing the nanofiller surface with a silane coupling agent. Finally, the high temperature breakdown strength for all samples is investigated and shows a considerable increase of nanocomposites dielectric performance at high temperature compared to neat PI

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12

Pallon, Love. "Polyethylene/metal oxide nanocomposites for electrical insulation in future HVDC-cables : probing properties from nano to macro." Doctoral thesis, KTH, Polymera material, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-193591.

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Nanocomposites of polyethylene and metal oxide nanoparticles have shown to be a feasible approachto the next generation of insulation in high voltage direct current cables. In order to reach an operationvoltage of 1 MV new insulation materials with reduced conductivity and increased breakdown strengthas compared to modern low-density polyethylene (LDPE) is needed.In this work polyethylene MgO nanocomposites for electrical insulation has been produced andcharacterized both from an electrical and material perspective. The MgO nanoparticles weresynthesized into polycrystalline nanoparticles with a large specific surface area (167 m2 g–1). Meltprocessing by extrusion resulted in evenly dispersed MgO nanoparticles in LDPE for the silane surfacemodified MgO as compared to the unmodified MgO. All systems showed a reduction in conductivityby up to two orders of magnitude at low loading levels (1–3 wt.%), but where the surface modifiedsystems were able to retain reduced conductivity even at loading levels of 9 wt.%. A maximuminteraction radius to influence the conductivity of the MgO nanoparticles was theoretically determinedto ca. 800 nm. The interaction radius was in turn experimentally observed around Al2O3 nanoparticlesembedded in LDPE using Intermodulation electrostatic force microscopy. By applying a voltage on theAFM-tip charge injection and extraction around the Al2O3 nanoparticles was observed, visualizing theexistence of additional localized energy states on, and around, the nanoparticles. Ptychography wasused to reveal nanometre features in 3D of electrical trees formed under DC-conditions. Thevisualization showed that the electrical tree grows by pre-step voids in front of the propagatingchannels, facilitating further growth, much in analogy to mechanical crack propagation (Griffithconcept). An electromechanical effect was attributed as possible mechanism for the formation of the voids.
Nanokompositer av polyeten och metalloxidpartiklar anses vara möjliga material att använda i morgondagens isolationshölje till högspänningskablar för likström. För att nå en transmissionsspänning på 1 MV behövs isolationsmaterial som i jämförelse med dagens polyeten har lägre elektrisk ledningsförmåga, högre styrka mot elektriskt genomslag och som kan kontrollera ansamling av rymdladdningar. De senaste årens forskning har visat att kompositer av polyeten med nanopartiklar av metalloxider har potential att nå dessa egenskaper. I det här arbetet har kompositer av polyeten och nanopartiklar av MgO för elektrisk isolation producerats och karaktäriserats. Nanopartiklar av MgO har framställts från en vattenbaserad utfällning med efterföljande calcinering, vilket resulterade i polykristallina partiklar med en mycket stor specifik ytarea (167m2 g-1). MgO-nanopartiklarna ytmodifierades i n-heptan genom att kovalent binda oktyl(trietoxi)silan och oktadekyl(trimetoxi)silan till partiklarna för att skapa en hydrofob och skyddande yta. Extrudering av de ytmodifierade MgO nanopartiklarna tillsammans med polyeten resulterade i en utmärkt dispergering med jämnt fördelad partiklar i hela kompositen, vilket ska jämföras med de omodifierade partiklarna som till stor utsträckning bildade agglomerat i polymeren. Alla kompositer med låg fyllnadsgrad (1–3 vikt% MgO) visade upp till 100 gånger lägre elektrisk konduktivitet jämfört med värdet för ofylld polyeten. Vid högre koncentrationer av omodifierade MgO förbättrades inte de isolerande egenskaperna på grund av för stor andel agglomerat, medan kompositerna med de ytmodifierade fyllmedlen som var väl dispergerade behöll en kraftig reducerad elektrisk konduktivitet upp till 9 vikt% fyllnadshalt. Den minsta interaktionsradien för MgO-nanopartiklarna för att minska den elektriska konduktiviten i kompositerna fastställdes med bildanalys och simuleringar till ca 800 nm. Den teoretiskt beräknade interaktionsradien kompletterades med observation av en experimentell interaktionsradie genom att mäta laddningsfördelningen över en Al2O3-nanopartikle i en polyetenfilm med intermodulation (frekvens-mixning) elektrostatisk kraftmikroskop (ImEFM), vilket är en ny AFM-metod för att mäta ytpotentialer. Genom att lägga på en spänning på AFM-kantilevern kunde det visualiseras hur laddningar, både injicerades och extraherades, från nanopartiklarna men inte från polyeten. Det tolkades som att extra energinivåer skapades på och runt nanopartiklarna som fungerar för att fånga in laddningar, ekvivalent med den gängse tolkningen att nanopartiklar introducera extra elektronfällor i den polymera matrisen i nanokompositer. Nanotomografi användes för att avbilda elektriska träd i tre dimensioner. Avbildningen av det elektriska trädet visade att tillväxten av trädet hade skett genom bildning av håligheter framför den framväxande trädstrukturen. Håligheterna leder till försvagning av materialet framför det propagerande trädet och förenklar på det sättet fortsatt tillväxt. Bildningen av håligheter framför trädstrukturen uppvisar en analogi till propagering av sprickor vid mekanisk belastning, i enlighet med Griffiths koncept.

QC 20161006

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13

Kanbur, Yasin. "Conductive Polymer Nanocomposites Of Polypropylene And Organic Field Effect Transistors With Polyethylene Gate Dielectric." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613312/index.pdf.

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One of the aim of this study is to prepare conductive polymer nanocomposites of polypropylene to obtain better mechanical and electrical properties. Composite materials based on conductive fillers dispersed within insulating thermoplastic matrices have wide range of application. For this purpose, conductive polymer nanocomposites of polypropylene with nano dimentional conductive fillers like carbon black, carbon nanotube and fullerene were prepared. Their mechanical, electrical and thermal properties were investigated. Polypropylene (PP)/carbon black (CB) composites at different compositions were prepared via melt blending of PP with CB. The effect of CB content on mechanical and electrical properties was studied. Test samples were prepared by injection molding and compression molding techniques. Also, the effect of processing type on mechanical and electrical properties was investigated. Composites become semiconductive with the addition of 2 wt% CB. Polypropylene (PP) / Carbon Nanotube (CNT) and Polypropylene / Fullerene composites were prepared by melt mixing. CNT&rsquo
s and fullerenes were surface functionalized with HNO3 : H2SO4 before composite preparation. The CNT and fullerene content in the composites were varied as 0.5, 1.0, 2.0 and 3.0 % by weight. For the composites which contain surface modified CNT and fullerene four different compatibilizers were used. These were selected as TritonX-100, Poly(ethylene-block-polyethylene glycol), Maleic anhydride grafted Polypropylene and Cetramium Bromide. The effect of surface functionalization and different compatibilizer on mechanical, thermal and electrical properties were investigated. Best value of these properties were observed for the composites which were prepared with maleic anhydride grafted polypropylene and cetramium bromide. Another aim of this study is to built and characterize transistors which have polyethylene as dielectric layers. While doing this, polyethylene layer was deposited on gate electrode using vacuum evaporation system. Fullerene , Pentacene ve Indigo were used as semiconductor layer. Transistors work with low voltage and high on/off ratio were built with Aluminum oxide - PE and PE dielectrics.

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14

Weaver, Abigail. "Mechanical and electrical properties of 3D-printed acrylonitrile butadiene styrene composites reinforced with carbon nanomaterials." Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/35413.

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Master of Science
Department of Mechanical and Nuclear Engineering
Gurpreet Singh
3D-printing is a popular manufacturing technique for making complex parts or small quantity batches. Currently, the applications of 3D-printing are limited by the material properties of the printed material. The processing parameters of commonly available 3D printing processes constrain the materials used to a small set of primarily plastic materials, which have relatively low strength and electrical conductivity. Adding ﬁller materials has the potential to improve these properties and expand the applications of 3D printed material. Carbon nanomaterials show promise as ﬁller materials due to their extremely high conductivity, strength, and surface area. In this work, Graphite, Carbon Nanotubes, and Carbon Black (CB) were mixed with raw Acrylonitrile Butadiene Styrene (ABS) pellets. The resulting mixture was extruded to form a composite ﬁlament. Tensile test specimens and electrical conductivity specimens were manufactured by Fused Deposition Method (FDM) 3D-printing using this composite ﬁlament as the feedstock material. Weight percentages of ﬁller materials were varied from 0-20 wt% to see the eﬀect of increasing ﬁller loading on the composite materials. Additional tensile test specimens were fabricated and post-processed with heat and microwave irradiation in attempt to improve adhesion between layers of the 3D-printed materials. Electrical Impedance Spectroscopy tests on 15 wt% Multiwalled Carbon Nanotube (MWCNT) composite specimens showed an increase in DC electrical conductivity of over 6 orders of magnitude compared to neat ABS samples. This 15 wt% specimen had DC electrical conductivity of 8.74x10−6 S/cm, indicating semi-conducting behavior. MWCNT specimens with under 5 wt% ﬁller loading and Graphite specimens with under 1 wt% ﬁller loading showed strong insulating behavior similar to neat ABS. Tensile tests showed increases in tensile strength at 5 wt% CB and 0.5 wt% MWCNT. Placing the specimens in the oven at 135 °C for an hour caused increased the stiﬀness of the composite specimens.

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15

Arlindo, Elen Poliani da Silva [UNESP]. "Estudo das propriedades elétricas e ópticas de nanocompósitos transparentes e condutores." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/91968.

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Анотація:

Made available in DSpace on 2014-06-11T19:25:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-02-18Bitstream added on 2014-06-13T18:53:39Z : No. of bitstreams: 1 arlindo_eps_me_ilha.pdf: 3403830 bytes, checksum: 35e9bb51a7710370f78852b7519f78ec (MD5)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Nanocompósitos são materiais que combinam duas (ou mais) fases sólidas, uma das quais deve possuir dimensões nanométricas, que pode reunir em um único material várias propriedades melhoradas para uma dada aplicação e, portanto, podem permitir a coexistência de propriedades tradicionalmente antagônicas como, transparência e condutividade. O presente trabalho teve como objetivo a obtenção de um nanocompósito polimérico transparente e condutor de polimetilmetacrilato – PMMA com nanofitas do sistema Indium Tin Oxide – ITO. Para isto primeiramente estudou-se a influência da temperatura na síntese das nanoestruturas de ITO e depois de obtida a temperatura de síntese que proporcionou o crescimento de nanofitas de ITO com maior condutividade e maior transparência no espectro visível, estudou-se a influência da inserção destas nanofitas nas propriedades ópticas e elétricas de filmes nanocompósitos de PMMA. Como as nanofitas obtidas são emaranhadas, para a obtenção do nanocompósito foi realizada uma separação prévia das mesmas utilizando duas dispersões distintas: sendo a primeira em um ultrasom convencional e a segunda em uma ponta ultrasônica. Depois de dispersas, as nanofitas foram misturadas ao PMMA comercial dissolvido em concentrações mássicas de 1%, 2%, 5% e 10% de nanofitas. As soluções foram então depositadas sobre substrato de vidro e, depois de secos, os filmes foram destacados. As caracterizações ópticas mostraram que a transmitância no espectro visível dos filmes diminui em função do aumento da quantidade de nanofitas no compósito. Neste estudo, as caracterizações elétricas mostraram que ocorreu percolação das nanofitas no polímero após a inserção de 5% em massa de nanofitas. As imagens de MET para os filmes corroboraram os resultados previstos pelas caracterizações elétricas. Os filmes...
Nanocomposites are materials which have two or more solid phases, and one of these phases should be in nano-sized scale range. These materials can have several properties increased for special application and it is possible to obtain composites with traditionally antagonistic combinations of properties, such as transparence in the visible range of light and good conductivity. The main goal of this work is obtain a transparent and conductive polymer-based nanocomposite using polymethylmethacrylate – PMMA and ITO (Indium Tin Oxide) nanobelts. To reach this goal it was first studied the influence of temperature on the synthesis of nanostructured ITO. Once the temperature of synthesis was optimized to ensure the growth of ITO nanobelts with both good conductivity and good transparency in the visible spectrum, we studied the influence of ITO nanobelts on the electrical and optical properties of nanocomposites of PMMA. Because the synthesized nanobelts are entangled each other, to obtain the composite it was realized a separation of them using two different ways; first using a conventional ultrasound and after an ultrasonic tip. Then, nanobelts were mixed with commercial PMMA dissolved in THF 10% in mass concentrations of 1%, 2%, 5% and 10%. So, the solution was deposited over a glass substrate by casting. The results showed that films transmittance in visible range decreases by increasing the amount of nanobelts. The electrical characterization showed that percolation occurred after 5%wt of filler. TEM images of composites corroborate the results provided by the electrical measures. The films prepared using both dispersions had the same transmittance in the visible spectrum, despite of the films obtained by dispersing the nanobelts in ultrasonic tip had a lower electrical resistance. Thus it can be concluded that the dispersion by ultrasonic... (Summary complete electronic access click below)

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16

Jäverberg, Nadejda. "Electrical Insulating Properties of Poly(Ethylene-co-Butyl Acrylate) Filled with Alumina Nanoparticles." Doctoral thesis, KTH, Elektroteknisk teori och konstruktion, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-116862.

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In this work the electrical insulating properties of the nanocomposite materials based on poly(ethylene-co-butyl acrylate) filled with alumina nanoparticles are studied. The dielectric properties chosen for the evaluation are the dielectric permittivity and loss as well as the breakdown strength and the pre-breakdown currents. The reason for choosing these particular properties is partly due to the importance of these for the general electrical applications and partly due to the uncertainties involved for these particular properties of the nanocomposite materials. The importance of moisture absorption for the dielectric properties is outlined in this work. All measurements were performed in both dry conditions and after conditioning of the materials in humid environment until saturation. The data for moisture absorption was taken from the water absorption study performed at the Department of Fibre and Polymer Technology, KTH. The dielectric spectroscopy in frequency domain was employed for measuring dielectric permittivity and loss. Havriliak-Negami approximation was used for characterization of the measurement data and at the same time ensuring the fulfillment of the Kramers-Kronig relations. Results from the dielectric spectroscopy study in dry conditions suggest that dielectric spectroscopy can be used for evaluating nanoparticle dispersion in the host matrix, based on correlation between the morphology data obtained from SEM investigation and the scatter in the dielectric loss. The dielectric spectroscopy study performed on the nanocomposites after conditioning in humid environment showed that absorbed moisture has a distinct impact on the dielectric loss. Especially pronounced is its’ influence on the frequency behavior, when the dielectric loss peaks are shifted towards higher frequencies with increased moisture content. The nanocomposite materials characterized by higher specific surface area generally exhibit higher dielectric losses. Surface functionalization of the nanoparticles does not seem to have much influence on the dielectric loss in dry conditions. After conditioning in humid environment, however, the surface modification was shown to have a significant impact. Temperature is another significant factor for the frequency behavior of the dielectric loss: it was found that the studied nanocomposites can be characterized by Arrhenius activation. The breakdown strength and pre-breakdown currents study outlined the influence of moisture as well. The study indicated that surface treatment of the nanoparticles can enhance properties of the nanocomposite materials, namely aminopropyltriethoxy silane was an especially successful choice: • The highest breakdown strength was determined by the study for NDA6 material formulation in dry conditions. • After conditioning in humid environment the NDA6 material continued showing the best breakdown strength among the nanocomposite mate rials, as well as this value was close to the breakdown strength of the reference unfilled material. This study confirms the existence of the optimal nanofiller content or rather optimal specific surface area of the dispersed nanoparticles in the host matrix. The latter is supported by the comparison between the nanocomposites based on nanoparticles with two different specific surface areas, which shows that the dielectric properties worsen, i.e. the dielectric losses increase and the influence of absorbed moisture on the breakdown strength becomes more pronounced, for nanomaterials with larger specific surface area. The pre-breakdown currents were found to follow space-charge limited conduction mechanism reasonably well. The following conduction regimes were identified: constant region (likely due to measurement difficulties at low field strengths), Ohm’s regime, trap-filled-limit regime and trapfree dielectric regime. The breakdown usually occurred either during the trap-filled-limit regime, when the current increased dramatically for the small change in electric field, or during the trapfree dielectric regime. The threshold values between different conduction regimes seem to correlate well with the oxidation induction times (OIT), which in turn depend on the total specific surface area. The pre-breakdown currents tend to be highest for the materials filled with the untreated nanoparticles. Increased absorbed moisture content causes higher pre-breakdown currents for the nanocomposite materials, while for the reference unfilled material the pre-breakdown currents do not show such tendency. Generally it can be said that the repeatability in the measured data is higher for the nanocomposite materials in comparison to the unfilled host material, as was demonstrated by both dielectric spectroscopy and breakdown studies.

QC 20130207

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17

Safdari, Masoud. "A Computational and Experimental Study on the Electrical and Thermal Properties of Hybrid Nanocomposites based on Carbon Nanotubes and Graphite Nanoplatelets." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/49570.

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Carbon nanotubes (CNTs) and graphite nanoplatelets (GNPs) are carrying great promise as two important constituents of future multifunctional materials. Originating from their minimal defect confined nanostructure, exceptional thermal and electrical properties have been reported for these two allotropic forms of carbon. However, a brief survey of the literature reveals the fact that the incorporation of these species into a polymer matrix enhances its effective properties usually not to the degree predicted by the composite\\textquoteright s upper bound rule. To exploit their full potential, a proper understanding of the physical laws characterizing their behavior is an essential step. With emphasis on the electrical and thermal properties, the following study is an attempt to provide more realistic physical and computational models for studying the transport properties of these nanomaterials.

Originated from quantum confinement effects, electron tunneling is believed to be an important phenomenon in determining the electrical properties of nanocomposites comprising CNTs and GNPs. To assess its importance, in this dissertation this phenomenon is incorporated into simulations by utilizing tools from statistical physics. A qualitative parametric study was carried out to demonstrate its dominating importance. Furthermore, a model is adopted from the literature and extended to quantify the electrical conductivity of these nanocomposite. To establish its validity, the model predictions were compared with relevant published findings in the literature. The applicability of the proposed model is confirmed for both CNTs and GNPs.

To predict the thermal properties, a statistical continuum based model, originally developed for two-phase composites, is adopted and extended to describe multiphase nanocomposites with high contrast between the transport properties of the constituents. The adopted model is a third order strong-contrast expansion which directly links the thermal properties of the composite to the thermal properties of its constituents by considering the microstructural effects. In this approach, a specimen of the composite is assumed to be confined into a reference medium with known properties subjected to a temperature field in the infinity to predict its effective thermal properties. It was noticed that such approach is highly sensitive to the properties of the reference medium. To overcome this shortcoming, a technique to properly select the reference medium properties was developed. For verification purpose the proposed model predictions were compared with the corresponding finite element calculations for nanocomposites comprising cylindrical and disk-shaped nanoparticles.

To shed more light on some conflicting reports about the performance of the hybrid CNT/GNP/polymer nanocomposites, an experimental study was conducted to study a hybrid ternary system. CNT/polymer, GNP/polymer and CNT/GNP/polymer nanocomposite specimens were processed and tested to evaluate their thermal and electrical conductivities. It was observed that the hybrid CNT/GNP/polymer composites outperform polymer composites loaded solely with CNTs or GNPs.

Finally, the experimental findings were utilized to serve as basis to validate the models developed in this dissertation. The experimental study was utilized to reduce the modeling uncertainties and the computational predictions of the proposed models were compared with the experimental measurements. Acceptable agreements between the model predictions and experimental data were observed and explained in light of the experimental observations.

The work proposed herein will enable significant advancement in understanding the physical phenomena behind the enhanced electrical and thermal conductivities of polymer nanocomposites specifically CNT/GNP/polymer nanocomposites. The dissertation results offer means to tune-up the electrical and thermal properties of the polymer nanocomposite materials to further enhance their performance.

Ph. D.

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18

Cerezo, Frances Therese, and francestherese_cerezo@hotmail com. "Thermal stability and mechanical property of polymer layered graphite oxide composites." RMIT University. Applied Sciences, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080627.161157.

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Polymer composites formed from layered fillers with high surface volume ratio show enhanced reinforcement. Graphite oxide is a high modulus material that can be separated into thin layers with high surface area. The aim of this study is to prepare polymer layered graphite oxide composites using functionalised polyolefin to enhance compatibility with various forms of layered graphite oxide in varying concentration. Functionalised polyolefins reinforced with layered graphite oxides and expanded graphite oxides were prepared using solution blending and melt blending methods. Three different mixing methods with varying shear intensity were employed to prepare polymer layered graphite oxide composites. The crystalline structure, thermal and mechanical properties of the prepared polymer layered graphite oxide composites was studied. Oxidised graphite prepared from the Staudenmaier method and its exfoliated form were dispersed in poly(ethylene-co-methyl acrylate-co-acrylic acid) (EMAA) via solution blending to prepare EMAA layered composites. The thermal stability was determined using thermogravimetric analysis. The EMAA layered composites showed higher thermal stability in comparison with pure EMAA. The mechanical properties of these EMAA layered composites were determined through dynamic mechanical analysis. Shear modulus, yield stress and storage modulus of EMAA in the presence of graphite oxide fillers decreased. A solution blending method was used to prepare poly(propylene-grafted-maleic anhydride) layered expanded graphite oxide composites (PPMA-EGO). Two types of PPMA-EGO were prepared using different mixing methods - low and high shear were employed. The effects of preparative mixing methods on the PPMA-EGO properties were investigated. The mechanical properties of PPMA-EGO obtained from dynamic mechanical analysis indicated that EGO had a reinforcing effect on the elastic behaviour of PPMA-EGO. This is due to strong interfacial adhesion between PPMA and EGO as a result of hydrogen bonding. The elastic behaviour of PPMA-EGO was affected by the surface area of graphite flakes. Low sheared PPMA-EGO elastic behaviour was found to be higher compared with that of high sheared PPMA-EGO. A melt blending method was used to prepare PPMA-EGO with varying EGO concentration. The interconnected network structure of EGO in the PPMA-EGO was not observed as shown by its scanning electron microscopy images. Thermogravimetric analysis of PPMA-EGO indicates increased decomposition temperature of the PPMA matrix. Dynamic mechanical analysis showed enhanced storage modulus of PPMA-EGO. The maximum elastic modulus of PPMA-EGO was observed at 3 %wt of EGO. The electrical conductivity of PPMA-EGO was measured only for EGO concentrations above 2 %wt. The EGO concentration was found to be the most critical factor in the enhancement of the electrical conductivity of PPMA-EGO. Wide angle X-ray diffraction analysis of all polymer layered graphite oxide composites revealed no change in interlayer spacing of graphite layers, indicating the absence of EMAA intercalation in the graphite layers. The crystallisation temperature and crystallinity of all polymer layered graphite oxide composites were determined using differential scanning calorimetry. The results indicated that graphite oxide and expanded graphite oxides acted as nucleating agents in inducing the crystallisation of functionalised polyolefin in the layered composites. However, the degree of crystallinity of functionalised polyolefin decreased in the layered composites.

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19

Matsumura, Masashi. "Synthesis, electrical properties, and optical characterization of hybrid zinc oxide/polymer thin films and nanostructures." Birmingham, Ala. : University of Alabama at Birmingham, 2007. https://www.mhsl.uab.edu/dt/2009r/matsumura.pdf.

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Анотація:

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007.
Title from PDF t.p. (viewed Feb. 3, 2010). Additional advisors: Derrick R. Dean, Sergey B. Mirov, Sergey Vyazovkin, Mary Ellen Zvanut. Includes bibliographical references (p. 122-145).

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Fragneaud, Benjamin Cavaillé Jean-Yves Terrones Maldonado Mauricio Gonzalez Montiel Alfonso. "Synthesis and characterization of polymer/carbon nanotubes composites impact of polymer grafting on the surface of CNx MWNTs on the electrical and mechanical properties of the nanocomposites /." Villeurbanne : Doc'INSA, 2007. http://docinsa.insa-lyon.fr/these/pont.php?id=fragneaud.

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21

Arlindo, Elen Poliani da Silva. "Estudo das propriedades elétricas e ópticas de nanocompósitos transparentes e condutores /." Ilha Solteira : [s.n.], 2010. http://hdl.handle.net/11449/91968.

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Orientador: Marcelo Ornaghi Orlandi
Banca: Walter Katsumi Sakamoto
Banca: Emerson Rodrigues de Camargo
Resumo: Nanocompósitos são materiais que combinam duas (ou mais) fases sólidas, uma das quais deve possuir dimensões nanométricas, que pode reunir em um único material várias propriedades melhoradas para uma dada aplicação e, portanto, podem permitir a coexistência de propriedades tradicionalmente antagônicas como, transparência e condutividade. O presente trabalho teve como objetivo a obtenção de um nanocompósito polimérico transparente e condutor de polimetilmetacrilato - PMMA com nanofitas do sistema Indium Tin Oxide - ITO. Para isto primeiramente estudou-se a influência da temperatura na síntese das nanoestruturas de ITO e depois de obtida a temperatura de síntese que proporcionou o crescimento de nanofitas de ITO com maior condutividade e maior transparência no espectro visível, estudou-se a influência da inserção destas nanofitas nas propriedades ópticas e elétricas de filmes nanocompósitos de PMMA. Como as nanofitas obtidas são emaranhadas, para a obtenção do nanocompósito foi realizada uma separação prévia das mesmas utilizando duas dispersões distintas: sendo a primeira em um ultrasom convencional e a segunda em uma ponta ultrasônica. Depois de dispersas, as nanofitas foram misturadas ao PMMA comercial dissolvido em concentrações mássicas de 1%, 2%, 5% e 10% de nanofitas. As soluções foram então depositadas sobre substrato de vidro e, depois de secos, os filmes foram destacados. As caracterizações ópticas mostraram que a transmitância no espectro visível dos filmes diminui em função do aumento da quantidade de nanofitas no compósito. Neste estudo, as caracterizações elétricas mostraram que ocorreu percolação das nanofitas no polímero após a inserção de 5% em massa de nanofitas. As imagens de MET para os filmes corroboraram os resultados previstos pelas caracterizações elétricas. Os filmes... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Nanocomposites are materials which have two or more solid phases, and one of these phases should be in nano-sized scale range. These materials can have several properties increased for special application and it is possible to obtain composites with traditionally antagonistic combinations of properties, such as transparence in the visible range of light and good conductivity. The main goal of this work is obtain a transparent and conductive polymer-based nanocomposite using polymethylmethacrylate - PMMA and ITO (Indium Tin Oxide) nanobelts. To reach this goal it was first studied the influence of temperature on the synthesis of nanostructured ITO. Once the temperature of synthesis was optimized to ensure the growth of ITO nanobelts with both good conductivity and good transparency in the visible spectrum, we studied the influence of ITO nanobelts on the electrical and optical properties of nanocomposites of PMMA. Because the synthesized nanobelts are entangled each other, to obtain the composite it was realized a separation of them using two different ways; first using a conventional ultrasound and after an ultrasonic tip. Then, nanobelts were mixed with commercial PMMA dissolved in THF 10% in mass concentrations of 1%, 2%, 5% and 10%. So, the solution was deposited over a glass substrate by casting. The results showed that films transmittance in visible range decreases by increasing the amount of nanobelts. The electrical characterization showed that percolation occurred after 5%wt of filler. TEM images of composites corroborate the results provided by the electrical measures. The films prepared using both dispersions had the same transmittance in the visible spectrum, despite of the films obtained by dispersing the nanobelts in ultrasonic tip had a lower electrical resistance. Thus it can be concluded that the dispersion by ultrasonic... (Summary complete electronic access click below)
Mestre

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22

Seidel, Gary Don. "Micromechanics modeling of the multifunctional nature of carbon nanotube-polymer nanocomposites." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1881.

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23

Jäverberg, Nadejda. "Dielectric properties of poly(ethyelene-co-butyl acrylate) filled with Alumina nanoparticles." Licentiate thesis, KTH, Elektroteknisk teori och konstruktion, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-31407.

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In this work dielectric properties of the poly(ethylene-co-butyl acrylate)filled with alumina nanoparticles are evaluated. These nanocomposite materialswere manufactured at the department of Fibre and Polymer Technology,KTH.This study is limited to the properties of general importance for the AC applications.The dielectric permittivity of the nanocomposite materials wasstudied as a function of filler size, filler content, coating, temperature and airhumidity used for conditioning of the samples. The ultimate goal with thisproject is to describe the influence of material composition, temperature andair humidity on the dielectric properties and model these dependencies.In this thesis the experimental setup for voltage endurance testing of thenanocomposites, namely studying applied voltage frequency dependence ofpartial discharges in electrical trees, with a possibility of following electricaltreeing optically, was developed and described.The dielectric spectroscopy measurements were performed on thoroughly driednanocomposites - so-called dry DS study. It was shown that the experimentaldata can be fitted with Havriliak-Negami approximation, which justifiesthe correctness of the measurement results. It has been shown that addingnanoparticles to the EBA matrix changes the low frequency dispersion significantlyfor the dried samples. It was also indicated that the particle coatingused has very low impact on the resulting permittivity of the thoroughly driedsamples. From the dry DS studies it was suggested that the main cause ofthe scattering in data between the dry samples is most likely the influenceof the material inhomogeneity and possibly the moisture absorption. Thisleads to a possibility of using dielectric spectroscopy as a tool for probing thedispersion of nanoparticles in the polymer matrix.The dielectric spectroscopy measurements were also carried out on the nanocompositesconditioned in the environments with different humidity levels of air inorder to study the influence of absorbed water on the dielectric permittivity- so-called wet DS study. From the wet study it was shown that for the wetsamples the amplitude of the loss peak is defined by the filler size, filler contentand coating used; while its position in frequency domain is determinedby the coating and the humidity level used for conditioning.
QC 20110315

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Bera, Chandan. "Thermo electric properties of nanocomposite materials." Phd thesis, Ecole Centrale Paris, 2010. http://tel.archives-ouvertes.fr/tel-00576360.

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Cette thèse présente une étude théorique du transport de chaleur dans les matériaux composites nano poreux et nano fils ainsi qu'une étude théorique des propriétés thermoélectriques de l'alliage Si0:8Ge0:2 confrontée à des mesures expérimentales réalisées pour une partie, dans le cadre de l'étude.La première étude démontre que les alliages poreux affichent des réductions de conductivité thermique à des dimensions de pores beaucoup plus grandes que les matériaux poreux non alliés de même porosité nominale. Si on considère une taille de pores de 1000nm, la conductivité thermique de l'alliage Si0:5Ge0:5 avec 0:1 de porosité est deux fois plus faible que la conductivité thermique d'un matériau non poreux, alors que les pores plus petits que 100 nm sont nécessaires pour obtenir la même réduction relative dans le Si ou Ge pur. Nos résultats indiquent que les alliages nano poreux devraient être avantageux devant les matériaux nano poreux non alliés, et ceux pour les applications nécessitant une faible conductivité thermique, tels que les nouveaux matériaux thermoélectriques.La deuxième étude théorique sur la conductance thermique de nano fils révèle l'effet de la structure sur le transport des phonons. Avec un modèle théorique qui considère la dépendance en fréquence du transport des phonons, nous sommes en mesure quantitativement de rendre compte des résultats expérimentaux sur des nano fils droits et coudés dans la gamme de température qui montre qu'un double coude sur un fil réduit sa conductance thermique de 40% à la température de 5K. Enfin, nous avons procédé à une approche théorique des propriétés thermoélectriques des alliages SiGe frittés, en les comparant aux mesures expérimentales nouvelles et antérieures, tout en évaluant leur potentiel d'amélioration. L'approche théorique a été validée par comparaison de la mobilité prévue et la conductivité thermique prévues, en faisant varier la quantité de Ge et les concentrations de dopage, dans une gamme de température comprise entre 300 et 1000K. Nos calculs suggèrent qu'une optimisation par rapport à l'état de l'art actuel est possible pour le matériau de type n et type p, conduisant potentiellement à une augmentation de 6% (5%) du ZT _a 1000K et 25% (4%) _a température ambiante. Même des améliorations plus grandes devraient être possibles si la probabilité de diffusion des phonons aux joints de grains pouvait être augmentée au-delà de sa valeur actuelle de 10%.

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Omara, Shereen Said Shabaan [Verfasser], Andreas [Akademischer Betreuer] Schönhals, Manfred H. [Gutachter] Wagner, and Andreas [Gutachter] Schönhals. "Preparation, characterization and electrical properties of nanocomposites based on hyperbranched polymers / Shereen Said Shabaan Omara ; Gutachter: Manfred H. Wagner, Andreas Schönhals ; Betreuer: Andreas Schönhals." Berlin : Technische Universität Berlin, 2018. http://d-nb.info/116407640X/34.

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26

Fragneaud, Benjamin. "Synthesis and characterization of polymer/carbon nanotubes composites : impact of polymer grafting on the surface of CNx MWNTs on the electrical and mechanical properties of the nanocomposites." Lyon, INSA, 2006. http://theses.insa-lyon.fr/publication/2006ISAL0124/these.pdf.

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New hybrid materials from the grafting of polystyrene on the surface of nitrogen doped carbon nanotube were synthesized. These chemically modified nanotubes were further used in the fabrication of polymer based nanocomposites. In these works, we studied the impact of the polymer grafted nanotubes on the electrical and mechanical properties of a polystyrene (PS) and a poly (butadiene-co-styrene) (PSBS) matrices. The grafted nanotubes have a better dispersion in a PS matrix as compared to the as received ones. Nevertheless, this kind of functionalization does not lower the percolation threshold since the grafted polymer layer electrically isolates the nanotubes each others. On the other hand, the mechanical reinforcement (PS matrix) increases when the nanotubes are polymer grafted. Furthermore, a stronger mechanical reinforcement is observed for large strain deformation. Concerning the nano-structured PSBS matrix, we observed a stronger mechanical reinforcement as compared to the PS matrix. The PS grafted nanotubes permit to connect the PS nano-domains of the matrix and consequently forms a percolating rigid network with a very low threshold (PC<0. 05 vol. %)
ADes nouveaux matériaux hybrides, provenant du greffage de polystyrène à la surface de nanotubes de carbone dopés azote (CNx MWNTs) ont été synthètisés et utilisés dans l’élaboration de nano-composites à matrice polymère. Dans ces travux de recherche nous avons étudiés l’impacte de ces nanotubes de carbone greffés polystyrène sur les propriétés mécaniques et électriques de matrices polystyrène (PS et poly (butadiène-co-styrène) (PSBS). Les nanotubes greffés ont une meilleure dispersion dans une matrice de polystyrène que les nanotubes sans traitement chimique. Cependant, ce type de fonctionnement ne permet pas de baisser le seuil de percolation électrique, puisque le greffage tend à isoler électriquement les nanotubes. Par ailleurs, nous avons observé une sensible augmentation de l’effet de renfort mécanique de la matrice PS quand les tubes sont greffés ; particulièrement quand les composites sont soumis à de grandes déformations. Dans le cas particulier d’une matrice nano structurée comme le PSBS, nous avons observé un effet de renfort mécanique beaucoup plus important quand les nanotubes étaient greffés. En effet, la couche de PS à la surface des CNx MWNTs connecte les domaines de PS du copolymère, permettant l’apparition d’un réseau percolant rigide avec un seuil de percolation très bas (PC <0. 05 vol%)

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Athreya, Siddharth Ram. "Processing and characterization of carbon black-filled electrically conductive nylon-12 nanocomposites produced by selective laser sintering." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/39508.

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Electrically conductive polymer composites are suitable for use in the manufacture of antistatic products and components for electronic interconnects, fuel cells and electromagnetic shielding. The most widely used processing techniques for producing electrically conductive polymer composites place an inherent constraint on the geometry and architecture of the part that can be fabricated. Hence, this thesis investigates selective laser sintering (SLS), a rapid prototyping technique, to fabricate and characterize electrically conductive nanocomposites of Nylon-12 filled with 4% by weight of carbon black. The objective of the dissertation was to study the effects of the SLS process on the microstructure and properties of the nanocomposite. The effect of laser power and the scan speed on the flexural modulus and part density of the nanocomposite was studied. The set of parameters that yielded the maximum flexural modulus and part density were used to fabricate specimens to study the tensile, impact, rheological and viscoelastic properties. The electrical conductivity of the nanocomposite was also investigated. The thermo-mechanical properties and electrical conductivity of the nanocomposites produced by SLS were compared with those produced by extrusion-injection molding. The structure and morphology of the SLS-processed and extrusion-injection molded nanocomposites were characterized using gas pycnometry, gel permeation chromatography, differential scanning calorimetry, electron microscopy, polarized light microscopy and x-ray diffraction. Physical models were developed to explain the effects of the processing technique on the structure and properties of the nanocomposites. Finally, a one-dimensional heat transfer model of the SLS process that accounted for sintering-induced densification and thermal degradation of the polymer was implemented in order to study the variation in part density with respect to the energy density of the laser beam. This dissertation demonstrated that SLS can be successfully used to fabricate electrically conductive polymer nanocomposites with a relatively low percolation threshold. This capability combined with the ability of SLS to fabricate complicated three-dimensional objects without part-specific tooling could open up several new opportunities.

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Guehenec, Matthieu. "Etude de nanocomposites réalisés par extrusion bi-vis : cas d'un polymère thermostable et d'une charge nanométrique." Thesis, Pau, 2012. http://www.theses.fr/2012PAUU3048/document.

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Ce mémoire a pour objectif l’étude de la réalisation de nanocomposites polyétherétherkétone (PEEK) /nanotubes de carbone (NTC) par mélange en voie fondue. Il s’est articulé autour de trois axes principaux, qui sont : l’impact du pourcentage de nanotubes de carbone sur les propriétés rhéologiques et électriques, l’influence du procédé d’extrusion bivis sur l’état de dispersion, ainsi que la réalisation du composite hybride renforcé en fibres longues de carbone. Un modèle rhéologique (loi de Carreau-Yasuda à seuil) et un modèle électrique (loi puissance), ont été utilisés pour caractériser quantitativement le seuil de percolation ainsi que le degré de dispersion. L’état de dispersion par le procédé d’extrusion dépend des conditions opératoires (vitesse de rotation N et débit d’alimentation Q). Les relations entre le procédé et l’état de dispersion ont également été étudiées à l’aide de la distribution des temps de séjour, et des énergies mécaniques spécifiques. Enfin, le comportement mécanique et électrique des composites hybrides a été exploré. L’étude des temps de dégradation, de relaxation à permis d’établir une fenêtre de mise en oeuvre du composite hybride
The aim of this dissertation is the study of the formation of polyetherethercetone (PEEK) / carbon nanotubes (NTC) nanocomposites via melt compounding. It focused on three major part which are the fallowing: the effect of CNT content on rheological and electrical properties, the effect of twin screw extrusion parameters on CNT dispersion, and the manufacture of hybrid composite reinforced with carbon fibers as well. A Carreau-Yasuda rheological model with a yield stress and power law model are used to characterize quantitatively the rheological and electrical percolation threshold and the state of dispersion. The state of dispersion is depending on the operating conditions (screw speed N and feed rate Q). The relationships between processing conditions and the state of dispersion are also investigated, using the residence time distribution and the specific mechanical energy. Finally, the mechanical and the electrical behavior of the hybrid composite have been studied. The degradation time and relaxation time studies drew a process window for the hybrid composite

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Levchenko, Volodymyr. "Morphologie et propriétés électrophysiques de nanocomposites à base de polymères thermoplastiques et de nanotubes de carbone." Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00862137.

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La thèse détermine les principaux paramètres de la formation des structures de la phase conductrice de nanocomposites polymères chargés avec des nanotubes de carbone (NTC) ou des nanocharges combinées, pour étudier l'influence de la morphologie de la structure hétérogène du composite et l'interaction des nanocharges sur les propriétés électriques, thermophysiques et mécaniques des composites. Les trois types de systèmes polymères ont été étudiés, à savoir: 1) les systèmes ségrégés avec distribution ordonnée de nanocharges, 2) les mélanges polymère conducteur; 3) les composites avec des charges binaires où les nanotubes de carbone ont été combinés avec des composés organo-argileux modifiés (MOC) dans un cas et des nanoparticules métalliques d'autre part. Les résultats sur les composites polymères ségrégés chargés avec des NTC ont montré que dans de tels systèmes, la charge conductrice crée un réseau continu conducteur au sein de la matrice polymère. Cela conduit à un seuil de percolation ultra faible avec la valeur de φc~0,045vol.%. Il a été démontré que les systèmes conducteurs à base de mélanges de polymères ont un seuil de percolation inférieur en raison d'effet de double percolation. Il a été constaté que l'introduction simultanée de composés MOC et de NTC dans la matrice thermoplastique permet une meilleure répartition des nanotubes de carbone, ce qui empêche leur agrégation. Il en résulte une diminution du seuil de percolation des composites. Il a été démontré que la formation de la phase conductrice est plus efficace avec des charges mixtes CNT/nanométal en comparaison avec les charges individuelles

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Njuguna, Michael Kamau. "Characterisation of multi wall carbon nanotube–polymer composites for strain sensing applications." Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/54671/1/Michael_Kamau_Njuguna_Thesis.pdf.

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Carbon nanotubes (CNTs) have excellent electrical, mechanical and electromechanical properties. When CNTs are incorporated into polymers, electrically conductive composites with high electrical conductivity at very low CNT content (often below 1% wt CNT) result. Due to the change in electrical properties under mechanical load, carbon nanotube/polymer composites have attracted significant research interest especially due to their potential for application in in-situ monitoring of stress distribution and active control of strain sensing in composite structures or as strain sensors. To sucessfully develop novel devices for such applications, some of the major challenges that need to be overcome include; in-depth understanding of structure-electrical conductivity relationships, response of the composites under changing environmental conditions and piezoresistivity of different types of carbon nanotube/polymer sensing devices. In this thesis, direct current (DC) and alternating current (AC) conductivity of CNT-epoxy composites was investigated. Details of microstructure obtained by scanning electron microscopy were used to link observed electrical properties with structure using equivalent circuit modeling. The role of polymer coatings on macro and micro level electrical conductivity was investigated using atomic force microscopy. Thermal analysis and Raman spectroscopy were used to evaluate the heat flow and deformation of carbon nanotubes embedded in the epoxy, respectively, and related to temperature induced resistivity changes. A comparative assessment of piezoresistivity was conducted using randomly mixed carbon nanotube/epoxy composites, and new concept epoxy- and polyurethane-coated carbon nanotube films. The results indicate that equivalent circuit modelling is a reliable technique for estimating values of the resistance and capacitive components in linear, low aspect ratio-epoxy composites. Using this approach, the dominant role of tunneling resistance in determining the electrical conductivity was confirmed, a result further verified using conductive-atomic force microscopy analysis. Randomly mixed CNT-epoxy composites were found to be highly sensitive to mechanical strain and temperature variation compared to polymer-coated CNT films. In the vicinity of the glass transition temperature, the CNT-epoxy composites exhibited pronounced resistivity peaks. Thermal and Raman spectroscopy analyses indicated that this phenomenon can be attributed to physical aging of the epoxy matrix phase and structural rearrangement of the conductive network induced by matrix expansion. The resistivity of polymercoated CNT composites was mainly dominated by the intrinsic resistivity of CNTs and the CNT junctions, and their linear, weakly temperature sensitive response can be described by a modified Luttinger liquid model. Piezoresistivity of the polymer coated sensors was dominated by break up of the conducting carbon nanotube network and the consequent degradation of nanotube-nanotube contacts while that of the randomly mixed CNT-epoxy composites was determined by tunnelling resistance between neighbouring CNTs. This thesis has demonstrated that it is possible to use microstructure information to develop equivalent circuit models that are capable of representing the electrical conductivity of CNT/epoxy composites accurately. New designs of carbon nanotube based sensing devices, utilising carbon nanotube films as the key functional element, can be used to overcome the high temperature sensitivity of randomly mixed CNT/polymer composites without compromising on desired high strain sensitivity. This concept can be extended to develop large area intelligent CNT based coatings and targeted weak-point specific strain sensors for use in structural health monitoring.

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Pirondelli, Andrea. "Production and Electrical Characterization of Low Density Polyethylene-based Micro- and Nano-dielectrics containing Graphene Oxide, Functionalized Graphene and Carbon Black additives." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016.

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Oggigiorno la ricerca di nuovi materiali per gradatori di campo da impiegarsi in accessori di cavi ha iniziato a studiare alcuni materiali nano dielettrici con proprietà elettriche non lineari con la tensione ed aventi proprietà migliorate rispetto al materiale base. Per questo motivo in questo elaborato si sono studiati materiali nanostrutturati a base di polietilene a bassa densità (LDPE) contenenti nano polveri di grafene funzionalizzato (G*), ossido di grafene (GO) e carbon black (CB). Il primo obiettivo è stato quello di selezionare e ottimizzare i metodi di fabbricazione dei provini. La procedura di produzione è suddivisa in due parti. Nella prima parte è stata utilizzatala tecnica del ball-milling, mentre nella seconda un pressa termica (thermal pressing). Mediante la spettroscopia dielettrica a banda larga (BDS) si sono misurate le componenti reali e immaginarie della permettività e il modulo della conducibilità del materiale, in tensione alternata. Il miglioramento delle proprietà rispetto al provino di base composto dal solo polietilene si sono ottenute quando il quantitativo delle nanopolveri era maggiore. Le misure sono state effettuate sia a 3 V che a 1 kV. Attraverso misurazioni di termogravimetria (TGA) si è osservato l’aumento della resistenza termica di tutti i provini, soprattutto nel caso quando la % di nanopolveri è maggiore. Per i provini LDPE + 0.3 wt% GO e LDPE + 0.3 wt% G* si è misurata la resistenza alle scariche parziali attraverso la valutazione dell’erosione superficiale dei provini. Per il provino contenente G* è stato registrato una diminuzione del 22% del volume eroso, rispetto al materiale base, mentre per quello contenente GO non vi sono state variazioni significative. Infine si è ricercata la resistenza al breakdown di questi ultimi tre provini sopra citati. Per la caratterizzazione si è fatto uso della distribuzione di Weibull. Lo scale parameter α risulta aumentare solo per il provino LDPE + 0.3 wt% G*.

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32

Ovsík, Jiří. "Sledování elektrických vlastností nanokompozitních materiálů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2012. http://www.nusl.cz/ntk/nusl-219642.

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The present work deals with the electrical properties of nanocomposite materials. Samples for the experiment are made of epoxy resin as a matrix and oxides TiO2, Al2O3, WO3, SiO2 as nanofillers in 0.5 and 1 percent performance. The experimental samples are measured in temperature and frequency dependence of relative permittivity, dissipation factor, rezistivity and are broken down by the influence of filler on the electrical properties of the polymer. Attention is also paid to the mechanical properties of nanocomposites.

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33

Marashdeh, Wajeeh. "Relaxation Behavior and Electrical Properties of Polyimide/Graphene Nanocomposite." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1595850361812632.

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34

Backes, Eduardo Henrique. "Desenvolvimento de nanocompósitos híbridos de epóxi/NTCPM/cargas minerais e avaliação das propriedades mecânicas, elétricas e térmicas." Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/8537.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
In the present work epoxy/ MWCNT/ mineral fillers nanocomposites were obtained using ultrasonication and calendering. The effect of addition of mineral filler (calcium carbonate, montmorillonite and sepiolite) in electrical, mechanical and thermal properties of epoxy/ MWCNT were analyzed. Two different CNT were studied, with different aspect ration and purity, however only Nanocyl CNT’s presented improvement in the nanocomposites electrical properties and for that reason was employed for hybrid epoxy/ MWCNT/ mineral nanocomposites production. The electrical percolation threshold was determined as 0.04 wt% and for 0.3 wt% the electrical conductivity reached 1.29X10-2 S/m. The addition of calcium carbonate and montmorillonite improved electrical conductivity for epoxy nanocomposites produced with 0.05 wt% CNT and the same behavior was observed for epoxy/ MWCNT / sepiolite nanocomposites at 0.1 wt% CNT. The epoxy/ MWCNT nanocomposite at 0.05% CNT when produzed via calendering presented improvement in the electrical conductivity compared to the same nanocomposite produced via ultrasonication. For epoxy/ MWCNT at 0.05 wt% of CNT, the addition of calcium carbonate in the nanocomposite led to an electrical conductivity 1 decade higher than the epoxy/ 0.05 wt% CNT nanocomposite produced via calendering. The mineral fillers also modified thermal and mechanical behavior of the nanocomposites, and improvements in flexural modulus, thermal stability and Tg were observed.
Neste trabalho produziu-se nanocompósitos híbridos de resina epóxi/ NTCPM/ cargas minerais utilizando-se sonicação de alta energia e calandragem, e estudou-se a influência da adição de diferentes cargas minerais (carbonato de cálcio, montmorilonita e sepiolita) nas propriedades elétricas, térmicas e mecânicas de nanocompósitos epóxi/NTCPM. Neste trabalho foram utilizados dois diferentes tipos de nanotubos de carbono, com razões de aspecto e purezas diferentes, e verificou-se que somente um deles apresentou melhoria nas propriedades elétricas dos nanocompósitos epóxi/NTCPM, o qual foi empregado na produção de nanocompósitos híbridos epóxi/ NTCPM/ cargas minerais. A percolação elétrica dos nanotubos de carbono foi determinada em aproximadamente 0,04% em massa, e para um teor de 0,3% em massa de nanotubos de carbono, a condutividade elétrica atingiu 1,29X10-2 S/m. Nos nanocompósitos processados via sonicação de alta energia, observou-se elevação da condutividade elétrica com a adição de montmorilonita sódica e carbonato de cálcio para os teores de 0,05% em massa de NTCPM e com a adição de sepiolita somente para o teor de 0,1% em massa de NTCPM. Nos nanocompósitos processados via calandragem, o nanocompósito de resina epóxi/ 0,05% NTCPM apresentou condutividade elétrica duas vezes superior ao mesmo nanocompósito processado via sonicação de alta energia e a adição de carbonato de cálcio elevou a condutividade elétrica do nanocompósito de resina epóxi/ 0,05% NTCPM/ carbonato de cálcio em uma ordem de grandeza quando comparado ao nanocompósito epóxi/ 0,05% NTCPM processado via calandragem. A adição de NTCPM e cargas minerais também modificou os comportamentos mecânico e térmico dos nanocompósitos, elevando-se o módulo elástico em flexão, resistência térmica e Tg.
FAPESP: 2014/16299-8

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35

Nygren, Kristian. "Magnetron Sputtering of Nanocomposite Carbide Coatings for Electrical Contacts." Doctoral thesis, Uppsala universitet, Oorganisk kemi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-302063.

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Today’s electronic society relies on the functionality of electrical contacts. To achieve good contact properties, surface coatings are normally applied. Such coatings should ideally fulfill a combination of different properties, like high electrical conductivity, high corrosion resistance, high wear resistance and low cost. A common coating strategy is to use noble metals since these do not form insulating surface oxides. However, such coatings are expensive, have poor wear resistance and they are often applied by electroplating, which poses environmental and human health hazards. In this thesis, nanocomposite carbide-based coatings were studied and the aim was to evaluate if they could exhibit properties that were suitable for electrical contacts. Coatings in the Cr-C, Cr-C-Ag and Nb-C systems were deposited by magnetron sputtering using research-based equipment as well as industrial-based equipment designed for high-volume production. To achieve the aim, the microstructure and composition of the coatings were characterized, whereas mechanical, tribological, electrical, electrochemical and optical properties were evaluated. A method to optically measure the amount of carbon was developed. In the Cr-C system, a variety of deposition conditions were explored and amorphous carbide/amorphous carbon (a-C) nanocomposite coatings could be obtained at substrate temperatures up to 500 °C. The amount of a-C was highly dependent on the total carbon content. By co-sputtering with Ag, coatings comprising an amorphous carbide/carbon matrix, with embedded Ag nanoclusters, were obtained. Large numbers of Ag nanoparticles were also found on the surfaces. In the Nb-C system, nanocrystalline carbide/a-C coatings could be deposited. It was found that the nanocomposite coatings formed very thin passive films, consisting of both oxide and a-C. The Cr-C coatings exhibited low hardness and low-friction properties. In electrochemical experiments, the Cr-C coatings exhibited high oxidation resistance. For the Cr-C-Ag coatings, the Ag nanoparticles oxidized at much lower potentials than bulk Ag. Overall, electrical contact resistances for optimized samples were close to noble metal references at low contact load. Thus, the studied coatings were found to have properties that make them suitable for electrical contact applications.

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36

Libra, Miroslav. "Elektrické vlastnosti nanokompozitů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220101.

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The present master´s thesis deals with the electrical properties of nanocomposite materials. Samples for the experiment are made epoxi resin and oxides TiO2 and Al2O3 as nanofillers in different percent performace. The samples nanocomposites are measured temperature dependence of the resistivity inside, dissipation factor and relative permittivity. It discusses the effect of the filler on the resulting electrical properties of the polymer.

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37

Ayewah, Daniel Osagie Oyinkuro. "Characterization of surfactant dispersed single wall nanotube - polystyrene matrix nanocomposite." Thesis, [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1397.

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38

Bardash, Liubov. "Synthesis and investigation of nanostructured polymer composites based on heterocyclic esters and carbon nanotubes." Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10174/document.

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La thèse concerne les synthèse et caractérisation de composites polymères nanostructurés à base d’esters de cyanates de bisphénol a (DCBA) ou à base d’oligomères cycliques de butylène téréphtalate (CBT) et de nanotubes de carbone multi-parois (MWCNTS). L’effet catalytique des nanotubes de carbone sur la polycyclotrimerisation de DCBA et aussi sur la polymérisation du CBT est observé. L’augmentation de la température de cristallisation a été fixée pour tous les échantillons de nanocomposites à base de polybutylène téréphtalate (cPBT). L’effet de la méthode de mise en forme de cPBT/MWCNTS sur ses propriétés thermiques et électriques a été établi. Il est observé que le traitement thermique additionnel des échantillons (recuit) à des températures inférieures à celle de la fusion du cPBT cause la réagglomération des MWCNTS dans le système. Il est établi que l’ajout de très bas taux de MWCNTS (0.03-0.06 pour cent en masse) dans la matrice de polycyanurate (PCN) augmente les valeurs de résistance à la flexion (64-94 pour cent). De même l’ajout de 0.01 pourcent de MWCNTS en masse dans le CBT augmente considérablement le module d'élasticité des nanocomposites cPBT. Cet effet a été expliqué par la dispersion efficace de cette faible quantité de nanocharges pendant la synthèse in situ de la matrice de cPBT et est confirmée par les clichés en microscopie. Il est déterminé que les propriétés électriques des nanocomposites à base d’esters hétérocycliques et MWCNTS peuvent varier de matériaux isolants aux matériaux conducteurs. Les seuils de percolation des deux systèmes sont très bas (0.22 et 0.38 pourcent pour nanocomposites à base de cPBT et PCN respectivement). La conductivité des composites conducteurs est particulièrement stable sur un large domaine de température ce qui laisse présager des applications intéressantes dans le domaine de la microélectronique et pour des pièces d’avion et de navettes spatiales
The thesis relates to synthesis and investigation of nanostructured polymer composites based on oligomers of cyanate esters of bisphenol a (DCBA) or cyclic butylene terephthalate (CBT) and multiwalled carbon nanotubes (MWCNTS). Catalytic effect of mwcnts in process of DCBA polycyclotrimerization as well as in cbt polymerization has been observed. Significant increase in crystallization temperature of nanocomposites based on polybutylene terephthalate (cPBT) with adding of MWCNTS is observed. The effect of processing method of cpbt/mwcnts nanocomposites on its electrical properties has been found. It has been established that the additional heating of the samples (annealing) at temperatures above melting of cPBT leads to reagglomeration of MWCNTS in the system. It is established that reagglomeration of MWCNTS results in increase of conductivity values of nanocomposites due to formation of percolation pathways of MWCNTS through polymer matrix. In the case of polycyanurate matrix (PCN), it is found that addition of small mwcnts contents (0.03-0.06 weight percents) provides increasing tensile strength by 62-94 percents. It has been found that addition of even 0.01 weight percents of MWCNTS provides significant increase in storage modulus of cPBT matrix. This is explained by effective dispersing of small amount of the nanofiller during in situ synthesis of pcn or cpbt matrix that is confirmed by microscopy techniques. It has been established that the properties of the nanocomposites based on heterocyclic esters and MWCNTS can be varied from isolator to conductor and has low percolation thresholds (0.22 and 0.38 weight percents for cPBT and PCN nanocomposites respectively). The conductivity of samples is particularly stable on a very large range of temperature from 300 to 10 degrees Kelvin that make these materials perspective for practical applications in microelectronics, as parts of aircraft and space constructions

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39

Chu, Chun. "Development of polymer nanocomposites for automotive applications." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37128.

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Polymer nanocomposites (PNCs) have gained significant interest because they have outstanding performance that allows cost reduction, weight reduction, and product improvement. This research study focuses on the manufacture and characterization of PNCs in order to explore their potential in automotive applications. More specifically, polypropylene (PP) nanocomposites reinforced with xGnP and nanokaolin were fabricated by manufacturing methods that optimize their performances. Exfoliated graphite nanoplatelets (xGnP) are promising nanofillers that are cost effective and multifunctional with superior mechanical, thermo-mechanical and electrical properties. Nanokaolin is a newly introduced natural mineral mind in Georgia that has not been studied as of now. PNCs reinforced with these two nanofillers were characterized in terms of mechanical, thermo-mechanical, and various other properties, and then compared to talc- reinforced PP composites, which are the current state of the art for rear bumpers used by Honda Motor. Characterization results indicated that xGnP had better performance than talc and nanokaolin. Furthermore, the addition of xGnP introduces electrical conductivity in the PNCs, leading to more potential uses for PNCs in automotive applications such as the ability to be electrostatic painted. In order to fabricate PNCs with a desired conductivity value, there is need for a design tool that can predict electrical conductivity. Existing electrical conductivity models were examined in terms of model characteristics and parameters, and model predictions were compared to the experimental data. The percolation threshold is the most important parameter in these models, but it is difficult to determine experimentally, that is why a correlation between thermo-mechanical properties and electrical conductivity is also investigated in this study.

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40

Al, Mafarage Ali M. "Processing and Properties of Multifunctional Two-Dimensional Nanocomposite Based on Single Wall Carbon Nanotubes." Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1556310855748631.

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41

Olenych, I. B., O. I. Aksimentyeva, and Yu Yu Horbenko. "Electrical Properties of Hybrid Composites Based on Poly(3,4-ethylenedioxythiophene) with ZnO and Porous Silicon Nanoparticles." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42552.

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The electrical properties of hybrid nanosystem based on poly(3,4 ethylenedioxythiophene) with ZnO and porous silicon nanoparticles were studied by the methods of current-voltage characteristics and thermally stimulated conductivity. The dependence of electrical parameters of hybrid films on their composition has been found. The analysis of the temperature dependences of the composites conductivity in the temperature range of 80-330 К indicates the activation character of charge transfer and presence the trapping of unequilibrium carriers at the porous silicon and ZnO nanoparticle – polymer interface.

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42

Nedfors, Nils. "Synthesis and Characterization of Multifunctional Carbide- and Boride-based Thin Films." Doctoral thesis, Uppsala universitet, Oorganisk kemi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-219040.

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This thesis present research on synthesis, microstructure, and properties of carbide- and boride- based thin films. The films have been synthesized by dc magnetron sputtering, and their microstructures have been characterized mainly by X-ray photoelectron spectroscopy (XPS), X-ray diffraction, and transmission electron microscopy. One of the main objectives with this research has been to evaluate the thin films potential as materials for sliding electrical contact applications and this have influenced, which properties that have been evaluated. Co-sputtered Nb-C films have a microstructure comprising of nanocrystalline NbCx (nc-NbCx) grains embedded in a matrix of amorphous C (a-C). A thinner a-C matrix form in the Nb-C films compared to the well-studied Ti-C system. As a consequence, the Nb-C films have a higher hardness and conductivity than previously studied Ti-C sputtered under similar conditions. The promising electrical contact properties are attained for reactively sputtered Nb-C films under industrial conditions, at deposition rates two orders of magnitude higher. A reduction in crystallinity is seen when Si is added to the Nb-C films and amorphous films forms at Si content > 25 at.%. The alloying of Si was however not beneficial for the electrical contact properties. Substoichiometric CrB2-x (B/Cr = 1.5) and NbB2-x (B/Nb = 1.8) films are achieved when deposited from MeB2 targets. Boron segregates to grain boundaries forming a B-rich tissue phase. This result in superhardness for the NbB2-x films (42 ± 4 GPa) as well as a low friction attributed to the formation of a boric acid film. Carbon forms a solid solution in the MeB2 grains as well as segregating to grain boundaries forming an amorphous BCx (a-BCx) phase when alloyed to CrB2-x and NbB2-x films. The formation of the a-BCx phase drastically improves the electrical contact resistance of the NbB2-x films. However, the mechanical properties are degraded, which result in a high friction and wear rate. It was in TEM studies of the metastable amorphous structures for the Nb-Si-C films found that the electron beam induces crystallization. Hence, great care is required when studying these types of metastable structures.

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43

Ezat, Gulstan S. "The influence of multi-walled carbon nanotubes on the properties of polypropylene nanocomposite : the enhancement of dispersion and alignment of multiwalled carbon nanotube in polypropylene nanocomposite and its effect on the mechanical, thermal, rheological and electrical properties." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5703.

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Carbon nanotubes are known as ideal fillers for polymer systems; the main advantage of carbon nanotubes over other nano-reinforcing particles is the combination of superior strength and stiffness with large aspect ratio. Carbon nanotubes may improve the mechanical, electrical and thermal properties of polymers, but to realise their potential in polymer systems uniform dispersion, strong interfacial adhesion and alignment of nanotubes within the polymer matrix are necessary. These properties are not easy to achieve and they are key challenges in producing CNT/Polymer system. This research was carried out in an attempt to understand how the properties of CNT/Polymer composite can be optimised by manipulation of additives, compounding and postcompounding conditions. Polypropylene/Multi-Walled Carbon Nanotube (PP/MCNT) composites were prepared by conventional twin screw extrusion. Dispersants and compatibilisers were used to establish good interaction between filler and polymer. Several different extruder screw configurations were designed and the properties of PP/MCNT composite prepared by each configuration investigated. The results indicated that the addition of carbon nanotubes without additives enhanced mechanical, electrical and thermal properties of polypropylene polymer. Incorporation of compatibilisers into PP/MCNT improved the stiffness but decreased the strength of the nanocomposite, whilst addition of dispersants decreased the mechanical properties of the nanocomposite. Addition of both additives at high concentration improved electrical conductivity and induced electrical percolation in the nanocomposite. Extruder screw configuration was found to have significant effect on the electrical conductivity whilst only slightly affecting mechanical properties of the nanocomposite, possibly due to the competition between dispersion and degradation of polymer chains and possible reduction of carbon nanotube length by intensive shear during compounding. The use of screw configuration with high mixing intensity promoted the dispersion of nanotubes and favoured the conduction process in the nanocomposite. Finally in an attempt to improve dispersion and alignment of carbon nanotubes, compounded PP/MCNT composite was subjected to micromoulding, fibre spinning and biaxial stretching processes and the resultant properties investigated. Application of post-compounding process was found to have significant effect on mechanical and rheological properties of the nanocomposite. Stiffness and strength of the nanocomposites treated by post-compounding processes were found to increase by up to 160% and 300%, respectively. The reinforcement effect of carbon nanotubes in the stretched nanocomposites was found to be the greatest. Rheological analysis suggested that the application of post-compounding processes enhanced dispersion of carbon nanotubes within the nanocomposite. Overall, this finding of this research has shown that carbon nanotubes can be incorporated into polypropylene using conventional equipment to provide significant improvement in properties. By careful choices of additives, compounding and postcompounding conditions, specific properties can be further enhanced.

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44

Kim, Mu Seong. "Design, Synthesis, Processing, and Thermal Analysis of Nanocomposites with Tunable Properties." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4099.

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Polymer composites containing nanosized fillers have generated explosive interest since the early 1980's. Many recent studies have been conducted incorporating nano-fillers into polymer matrices to design and synthesize materials with tunable mechanical, thermal, and optical properties. Conventional filled polymers, where the reinforcement is on the order of microns, have been replaced by composites with discrete nanosized fillers. Gradually, theories that predicted that composite properties are independent of particle size in the micron range were challenged by nanocomposites. Rather, nanocomposite properties are greatly influenced by the surface area of the. All of this is complicated by the fact that nanoparticles are inclined to aggregate or migrate to interfaces. Much effort has been devoted to optimize dispersion of nanofillers in the polymer matrices, as polymer-nanoparticle interactions and adhesion greatly influence performance of the material. A well- dispersed composite system with various noncovalent interactions such as those that arise from hydrogen bonding, electrostatic attractions and π-π interactions between the filler and the matrix, can transfer stress and the interface will stop the development of cracks and impede stress concentrations. Overall, large reinforcement increases are noted at low nanoparticle loadings. Additionally, functional properties such as thermal, electrical conductivity and porosity can be tailored for specific applications. The design of high performance composites requires optimizing dispersion, nanoparticle-polymer noncovalent interactions and the chemistry of the materials. Therefore polymer composites with different types of nanofillers were investigated to prove various noncovalent interaction and to improve the mechanical, thermal and electrical properties in this study. Poly (methyl methacrylate) (PMMA) with BaTiO3 and Bi2O3 composites were fabricated by two different methods; sonication of fillers in PMMA and in situ polymerization. Samples were irradiated in air via a JL Shepherd Mark I cesium-137 source. The dose rate was 985 rads/min and the total dose was 2.0 Mrad. The polymer sonication (PSON) method has a greater effect than in situ polymerization on sample uniformity. With the PSON method there was a slight improvement in rad hardness in the barium titanate composites. This is the case with and without MWNTs and coupling agents. The storage modulus and loss modulus were measured via Dynamic Mechanical Analyzer (DMA) under the tension film mode using a heating rate of 5 °C min-1 from -150 °C to 200 °C and a scanning frequency range of 1-100 Hz. Scanning electron microscopy (SEM) provided images of the polymer-nanocomposites. An aliphatic isocyanate, polyether, polyol thermoplastic polyurethane, Tecoflex® SG-85A, was solution processed with the varying amounts of silica nanowire. A new grade polyurethane, Tecoflex®, was synthesized from the aliphatic 4,4-methylene dicyclohexyl diisocyanate (H12MDI) with polytetramethylene ether glycol. Despite Tecoflex®'s longevity and wide use, this polymer's dielectric behavior has not been widely studied. Therefore, the dielectric response of neat PU, Tecoflex®, and PU composites with silica nanowire from -150 to 150 °C is presented. The mechanism of nanowire growing with diameters ranging from 50 to 500 nm has been established to follow the vapour liquid solid (VLS) model via the PtSi phase acting as the catalyst. Our previous thermal stability study of PU nanowire composites have yielded increased heat stability to 330 °C. In comparison, neat PU only maintains thermal stability in temperatures that range to 250 °C. The onset of decomposition temperature was measured by thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) provided images of the polymer-nanocomposites. A series of PMMA-dodecyloxy NB and PHEMA-dodecyloxy NB composites were synthesized in situ and characterized. The dodecyl groups significantly alter the solubility of the nanoballs, imparting hydrophobicity to the surface of the nanoball. A comparison study was made between the PMMA-NB and PHEMA-NB nanocomposites. Structure property relations are discussed in terms of interactions between the polymer matrices and nanoball surfaces and interiors. These OC12 NB and the hydroxyl NB polymer composites are the first studies to date that probe relaxations and conductivity in discrete polyhedral metal-organic polymer composites. A novel ultra-flexible polycarbonate-polyurethane (PCPU) was synthesized with methylene bis(4-cyclohexylisocyanate), 1,4 butanediol as a chain extender and a polycarbonate polyol containing 1,6-hexanediol and 3-methyl-1,5-pentanediol. Through the techniques of water coagulation, the synthesis of self-healing PCPU with various concentrations of SWNT (Single-Walled Nanotubes) is possible. The resulting features of this synthesized rubber-like substance are to be evaluated to determine glass transition temperature. This novel type of polyurethane material targets growing markets for biocompatible polymers. Also, a secondary goal of this project is to obtain information useful to determining whether PCPU-carbon nanotube composites would be good candidates for use as a gel electrolyte in polymer batteries. All nanocomposites were characterized by differential scanning calorimetry (DSC) to determine glass transition temperatures. The dielectric permittivity (ε’) and loss factor (ε”) were also measured via Dielectric Analysis (DEA) in the frequency range 1Hz to 100 kHz and between the proper temperatures in all polymer composite. The electric modulus formalism was used to reveal structural relaxations including conductivity relaxation. The activation energies for the relaxations are presented.

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45

Folkenant, Matilda. "Synthesis and Characterization of Amorphous Carbide-based Thin Films." Doctoral thesis, Uppsala universitet, Oorganisk kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-247282.

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In this thesis, research on synthesis, structure and characterization of amorphous carbide-based thin films is presented. Crystalline and nanocomposite carbide films can exhibit properties such as high electrical conductivity, high hardness and low friction and wear. These properties are in many cases structure-related, and thus, within this thesis a special focus is put on how the amorphous structure influences the material properties. Thin films within the Zr-Si-C and Cr-C-based systems have been synthesized by magnetron sputtering from elemental targets. For the Zr-Si-C system, completely amorphous films were obtained for silicon contents of 20 at.% or higher. Modeling of these films, as well as experimental results suggest that the films exhibit a network-type structure where the bond types influence the material properties. Higher hardness and resistivity were observed with high amounts of covalent Si-C bonds. Several studies were performed in the Cr-C-based systems. Cr-C films deposited in a wide composition range and with substrate temperatures of up to 500 °C were found to be amorphous nanocomposites, consisting of amorphous chromium carbide (a-CrCx) and amorphous carbon (a-C) phases. The carbon content in the carbidic phase was determined to about 30-35 at.% for most films. The properties of the Cr-C films were very dependent of the amount of a-C phase, and both hardness and electrical resistivity decreased with increasing a-C contents. However, electrochemical analysis showed that Cr-C films deposited at higher substrate temperature and with high carbon content exhibited very high oxidation resistance. In addition, nanocomposite films containing Ag nanoparticles within an amorphous Cr-C matrix were studied in an attempt to improve the tribological properties. No such improvements were observed but the films exhibited a better contact resistance than the corresponding binary Cr-C films. Furthermore, electrochemical analyses showed that Ag nanoparticles on the surface affected the formation of a stable passive film, which would make the Cr-C/Ag films less resilient to oxidation than the pure Cr-C films.

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46

Dhahri, Abdelwaheb. "Synthèse et caractérisation de nanocomposites conducteurs à base de « graphène » et de polysaccharides." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1069/document.

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L'objectif principal de cette thèse a été d'expérimenter de nouvelles voies d'exfoliation des feuillets de graphène dans des matrices polysaccharides telles que la cellulose et le chitosane dopé avec des nanoparticules d'or (Au). Notre stratégie a été d'explorer de nouvelles voies de greffage de molécules et de macromolécules sur des feuillets d'oxyde de graphène (GO). Dans un premier temps, nous avons donc oxydé un graphite commercial par la méthode de Hummers qui est apriori la méthode la plus simple à mettre en oeuvre pour produire une suspension stable de feuillets d'oxyde de graphène totalement exfoliés dans l'eau. L'intérêt de cette oxydation est l'obtention de fonctions acide carboxylique et époxyde susceptibles d'être fonctionnalisées en deux étapes par l'éthylénediamine puis par un polysaccharide tel que la cellulose. En effet, afin d'améliorer la compatibilité du graphite oxydé avec des matrices organiques telle que la cellulose, l'idée est de lui greffer des chaînes polysaccharides. Ces résultats ont permis de mettre en évidence l'exfoliation partielle des feuillets de graphène après fonctionnalisation et l'obtention d'un taux de greffage massique d'environ 35% pour la cellulose. La conductivité électrique des nano-composites correspondants a aussi été étudiée par des mesures diélectriques à des températures variées. L'augmentation de la conductivité électrique après la fonctionnalisation du graphite oxydé a mis en évidence une solvo-thermoréduction simultanément à la fonctionnalisation. Enfin, le dopage de ce matériau par des particules d'or a permis d'obtenir une conductivité électrique de 1.60 10-4 S m-1. En ce qui concerne le matériau composite à base de chitosane, la démarche scientifique a été la même que pour l'analogue cellulose, le taux de greffage massique a été d'environ 68% et nous avons en plus testé son activité catalytique vis-à-vis de la conversion du 4-Nitrophénol en 4-Aminophénol et les résultats obtenus ont été très satisfaisants
The main objective of this thesis has been to experiment a new ways of exfoliation of graphene sheets in polysaccharide matrices such as cellulose and chitosan doped with gold nanoparticles (Au). Our strategy was to explore new routes for the grafting of molecules and macromolecules onto graphene oxide (GO). First, we have oxidized commercial graphite by the method of Hummers which is a priori the simplest method to implement to produce a stable suspension of graphene oxide sheets totally exfoliated in water. The advantage of this oxidation is the formation of carboxylic acid and epoxy functional groups onto the graphite surface that can be functionalized in two stages by ethylenediamine and then by a polysaccharide such as cellulose. Indeed, in order to improve the compatibility of graphite oxide with organic matrix such as cellulose, the idea is to graft it onto polysaccharide chains. These results made it possible to demonstrate the partial exfoliation of the graphene sheets after functionalization and to obtain a percentage of grafting of about 35wt% for cellulose. The electrical conductivity of the corresponding nanocomposites has also been studied by dielectric measurements at various temperatures. The increase of the electrical conductivity after the functionalization of graphite oxide showed a solvo-thermo reduction simultaneously with the functionalization. Finally, the doping of this material by gold particles made it possible to obtain an electrical conductivity of 1.60 10-4 S m-1. Concerning chitosan-based composite materials, the scientific approach was the same as cellulose substrate and we obtained a percentage of grafting of 68wt%. In addition, its catalytic activity for the conversion of 4-Nitrophenol to 4-Aminophenol was of high efficiency

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47

Mada, Mykanth Reddy Materials Science &amp Engineering Faculty of Science UNSW. "Fabrication and characterisation of SWCNT-PMMA and charcoal-PMMA composites with superior electrical conductivity and surface hardness properties." Awarded by:University of New South Wales. Materials Science & Engineering, 2009. http://handle.unsw.edu.au/1959.4/41831.

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Fabrication of SWCNT-PMMA and Activated Charcoal- PMMA composites was carried out by the compression moulding technique. Then Mechanical and Electrical properties of the composites were investigated. The morphological studies of composites showed a) good dispersion of fillers and b) good interaction between fillers and matrix. Electrical conductivity of SWCNT-PMMA composites was increased by 9 orders of magnitude (at 0.8 % volume fraction of SWCNT) and that of AC-PMMA composites increased by 16 orders of magnitude (at 17 % volume fraction of AC). The percolation threshold of both composites turned out to be lower compared to the theoretical values. A significant improvement in mechanical properties was obtained ??? particularly in AC-PMMA composites which showed a 400 % improvement in Vickers microhardness ??? raising the polymer matrix abrasion property literally to that of Aluminium alloys (Dobrazanski et al 2006). In conclusion, it is to be noted that Activated Charcoal - PMMA composites have a great potential for cost effective conducting polymer composite production by the use of cheap filler: In addition, the compression moulding technique shows good potential for cost effective fabricating technique for amorphous polymers with high electrical and mechanical properties.

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48

Dulgerbaki, Cigdem. "Synthesis And Characterization Of Polythiophene/montmorillonite And Polythiophene/polypropylene Composites." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607762/index.pdf.

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In this study, polythiophene(PTP)/montmorillonite(MMT) nanocomposites were synthesized by in situ intercalative polymerization and chemical oxidative polymerization. In in situ intercalative polymerization method, composites containing 90 and 95% MMT were prepared. In chemical oxidative polymerization method, a series of composites ranging from 1 to 15% by weight MMT were synthesized. Thermal and morphological properties of samples were investigated by Differential Scanning Calorimeter (DSC), Thermal Gravimetric Analysis (TGA), X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM)
electrical conductivities were measured by four probe technique. Since PTP/MMT composites are unprocessable PTP/polypropylene(PP) composites were prepared. Amounts of PTP were changed in the range 2-30 % by weight in the composites. Mechanical properties were investigated by tensile tests. Four probe technique was used for measurement of electrical conductivities. Morphological characterizations were made by SEM. Formation of PTP and its incorporation in PTP/MMT composite were confirmed by FTIR analysis. DSC results showed that PTP does not have any thermal transition in the range 25-300 0C. TGA results showed that PTP/MMT composites have outstanding stability compared to that of PTP. XRD analysis revealed the formation of nanocomposites resulting from intercalation of thiophene in MMT at high MMT contents. Composites were observed as globular particles and clusters in SEM studies. Conductivity values of PTP/MMT composites were in the order of 10-3 S/cm. It is observed that tensile modulus of PTP/PP composites increases by the addition of PTP, but percentage strain at break does not appreciably change. Increasing PTP content increased electrical conductivity.

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49

Benhadjala, Warda. "Fiabilité et miniaturisation des condensateurs pour l'aéronautique : de l'évaluation de composants céramique de puissance à l'étude de nanoparticules hybrides céramique / polymère pour technologies enterrées." Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR15271/document.

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L’amélioration des systèmes électroniques pour le déploiement de l'avion tout électrique dépend de la capacité des composants passifs, tels que les condensateurs, à réduire leur volume, leur masse et leur coût, et augmenter leurs performances et leur fiabilité, particulièrement dans l’environnement aéronautique. Dans ce contexte, cette thèse a eu pour objectif l’étude et le développement de nouvelles technologies de condensateurs pour des applications avioniques. Dans la première partie des travaux, nous abordons l’évaluation de condensateurs céramique de puissance. La technologie céramique constitue, en effet, l’une des rares solutions matures capables de répondre aux exigences des équipementiers. La caractérisation, l’analyse des mécanismes de défaillance, de leurs effets et de leur criticité (AMDEC) ainsi que l’étude de fiabilité et de robustesse de composants commerciaux présentant des architectures originales (condensateurs multi-chips) ont été réalisées. Ces résultats ont été complétés par une étude plus amont sur la caractérisation de céramiques frittées par frittage flash (SPS). Les permittivités colossales de ces matériaux permettraient d’accroitre la fiabilité et la miniaturisation des condensateurs tout en conservant de fortes valeurs de capacité et de tension nominale. La seconde partie, plus fondamentale, a été consacrée au développement de nanoparticules céramique/polymère coeur-écorce pour des applications de condensateurs enterrés, opérant aux radiofréquences. La synthèse et les caractérisations physico-chimiques des nanocomposites ainsi que les procédés de fabrication de condensateurs en couches épaisses sont, en premier lieu, décrits. Une méthode de caractérisation électrique large bande a été mise au point pour permettre l’analyse des propriétés diélectriques et des mécanismes de conduction des nanoparticules. Les performances des dispositifs ont été recherchées en fonction de la température et des procédés de mise en forme. En outre, la durabilité en température de ces derniers a été évaluée
The improvement of electronic systems for the deployment of all-electric aircrafts depends on the ability of passive components, such as capacitors, to reduce their volume, weight and cost, and to increase their performance and reliability, particularly in the aeronautical environment. In this context, the objective of this thesis was to study and develop novel capacitor technologies for avionics. In the first part of this work, the evaluation of power ceramic capacitors has been discussed. Indeed, the ceramic technology appeared to be one of the few mature solutions meeting the requirements of OEMs. The characterization, the failure mode, effects and criticality analysis (FMECA) and reliability and robustness assessment of commercial components using original architectures (multi-chip capacitors) have been performed. These results have been completed by a more advanced study on the characterization of new ceramics sintered by spark plasma sintering (SPS). The colossal permittivity of these materials could allow to increase reliability and miniaturization of capacitors while maintaining high values of capacitance and voltage rating. The second part, more fundamental, is devoted to the development of core-shell ceramic/polymer nanoparticles for embedded capacitors operating at radiofrequencies. The synthesis and the physicochemical characterization of the nanocomposites as well as the manufacturing processes of the thick film capacitors are first described. A new broadband electrical characterization methodology has been developed to analyze the dielectric properties and the conduction mechanisms of the nanoparticles. The effects of the temperature and the manufacturing process on the device performance have been investigated. In addition, the durability was evaluated

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50

Bardash, Liubov, and Liubov Bardash. "Synthesis and investigation of nanostructured polymer composites based on heterocyclic esters and carbon nanotubes." Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00821160.

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The thesis relates to synthesis and investigation of nanostructured polymer composites based on oligomers of cyanate esters of bisphenol a (DCBA) or cyclic butylene terephthalate (CBT) and multiwalled carbon nanotubes (MWCNTS). Catalytic effect of mwcnts in process of DCBA polycyclotrimerization as well as in cbt polymerization has been observed. Significant increase in crystallization temperature of nanocomposites based on polybutylene terephthalate (cPBT) with adding of MWCNTS is observed. The effect of processing method of cpbt/mwcnts nanocomposites on its electrical properties has been found. It has been established that the additional heating of the samples (annealing) at temperatures above melting of cPBT leads to reagglomeration of MWCNTS in the system. It is established that reagglomeration of MWCNTS results in increase of conductivity values of nanocomposites due to formation of percolation pathways of MWCNTS through polymer matrix. In the case of polycyanurate matrix (PCN), it is found that addition of small mwcnts contents (0.03-0.06 weight percents) provides increasing tensile strength by 62-94 percents. It has been found that addition of even 0.01 weight percents of MWCNTS provides significant increase in storage modulus of cPBT matrix. This is explained by effective dispersing of small amount of the nanofiller during in situ synthesis of pcn or cpbt matrix that is confirmed by microscopy techniques. It has been established that the properties of the nanocomposites based on heterocyclic esters and MWCNTS can be varied from isolator to conductor and has low percolation thresholds (0.22 and 0.38 weight percents for cPBT and PCN nanocomposites respectively). The conductivity of samples is particularly stable on a very large range of temperature from 300 to 10 degrees Kelvin that make these materials perspective for practical applications in microelectronics, as parts of aircraft and space constructions.

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Дисертації з теми "Electrical Properties - Nanocomposites"

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