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Zheng, Yishan. "Activated carbon & carbon-cryogel composites for haemoperfusion based applications." Thesis, University of Brighton, 2013. https://research.brighton.ac.uk/en/studentTheses/daf37d00-4da8-4b0d-8bb5-a91941fed23d.
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A number of pathological conditions are associated with the build up of toxic substances within the systemic circulation. For example, renal and hepatic failure can lead to the accumulation of metabolites which are usually processed by these organs. There has been much interest over a number of years in techniques such as haemoperfusion that could help clear these toxins from the body and improve patient outcome. Haemoperfusion is an extracorporeal blood purification technique in which a patient’s blood is passed over a column containing a material designed to adsorb a board spectrum of biological toxic molecules. Direct blood contact with the adsorbent requires a material that is able to display good haemocompatibility whilst maintaining adsorption efficiency. Activated carbons (AC) have great adsorption capacity and have previously been used as haemoadsorbents. However the haemocompatibility of carbons has been questioned and they are often coated with biocompatible polymers that increase their haemocompatibility but also act as a barrier to the removal of larger toxins and middle molecules.
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Sun, Xinxin. "Conductive behaviour of carbon nanotube based composites." Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/6280.
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This project was basically exploratory in the electrical properties of carbon nanotube (CNT) based materials. The direct current (DC) conductivity of CNT/polymer composites was computed by using equivalent circuit method and a three dimensional (3-D) numerical continuum model with the consideration of tunneling conduction. The effects of the potential barrier of polymer and the tortousity of CNTs on the conductivity were analyzed. It was found that both of percolation threshold and DC conductivity can be strongly affected by the potential barrier and the tortousity. The influence of contact resistance on DC conductivity was also computed, and the results revealed that contact resistance and tunneling resistance had significant influences on the conductivity, but did not affect the percolation threshold. The microstructure-dependent alternating current (AC) properties of CNT/polymer composites were investigated using the 3-D numerical continuum model. It was found that AC conductivity and critical frequency of CNT/polymer composites can be enhanced by increasing the curl ratio of CNTs. In the mid-range CNT mass fraction, with increasing curl ratio of CNTs, AC conductivity, interestingly, became frequency-dependent in low frequency range, which cannot be explained by reference to the percolation theory. A proper interpretation was given based on the linear circuit theory. It was also found that the critical frequency can also be affected by the size of CNT cluster. Series numerical formulas were derived by using a numerical capacitively and resistively junction model. In particular, this work introduced an equivalent resistor-capacitor (RC) circuit with simple definitions of the values of contact resistance and average mutual capacitance for CNT/polymer nanocomposites. Theoretical results were in good agreement with experimental data, and successfully predicted the effect of morphology on the AC properties of CNT/polymer composites. DC and AC conductivities of multi-walled carbon nanotube (MWCNT)/graphene oxide (GO) hybrid films were measured for selected MWCNT mass fractions of 10%, 33.3%, 50%, 66.7%, and 83.3% using four-probe method. The experimental results were fitted using scaling law, and relatively high percolation threshold was found. This high percolation threshold was understood in terms of the potential energy and intrinsic ripples and warping in the freestanding graphene sheets. The capacitance of these hybrid films were measured using the voltmeter-ammeter-wattmeter test circuit with different voltages and heat treatments. The MWCNT/GO film showed relatively high specific capacitance (0.192F/cm3 for the mass fraction of 83.3%) and power factor compared to conventional dielectric capacitors. Both of measured capacitance and power factor can be enhanced by increasing testing voltages. The capacitance of MWCNT/GO films rapidly decreased after heat treatments above 160 ℃. This decrease was caused by redox reaction in the GO sheets. The capacitive behaviour of MWCNT/GO hybrid films was also interpreted by using the equivalent circuit model. Single-walled carbon nanotube (SWCNT) and SWCNT/Poly(vinyl alcohol) (PVA) films were used to form a piezoresistive strain sensor. Both of static and dynamic strain sensing behaviours of SWCNT and SWCNT/PVA films were measured. It was found that the sensitivities of these films decreased with increasing their thicknesses. The SWCNT film with a thickness of 1900 nm and SWCNT/PVA film exhibited viscoelastic sensing behaviour, because van der Waals attraction force allowed axial slippages of the smooth surface of nanotubes. A numerical model was derived based on the dynamic strain sensing behaviour. This model could be useful for designing CNT strain sensors. Finally, thermoelectric power (TEP) of deformed SWCNT films with various thicknesses was measured. It was observed that positive TEP of SWCNT films increased with increasing stain above the critical point. The experimental results were fitted by using a numerical model in terms of a variation of Nordheim-Gorter relation and fluctuation induced tunneling (FIT) model. From the numerical model, it was found that the increase of TEP above the critical strain resulted from the positive term of the contribution from the barrier region, and the effect of barrier regions decreases with increasing the thickness of the film.
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Raza, Mohsin Ali. "Carbon nanofiller-based composites for thermal interface applications." Thesis, University of Leeds, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.574596.
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Carbon nanofillers such as graphite nanoplatelets (GNPs) and vapour grown carbon nanofibres (VGCNFs) have enormous potential for developing thermal interface materials (TIMs), mainly due to their high thermal conductivity. In this project GNPs, VGCNFs and carbon black (CB) fillers were dispersed in the compliant polymer matrices, rubbery epoxy and silicone, to form composites. Mechanical mixing, dual asymmetric centrifuge speed mixing, three-roll milling or combined sonication and solvent mixing were used to produce composites. The effects of processing technique, wt.% offiller(s), particle size and silane-functionalisation of fillers on the properties of composites were studied. Composites were characterised mainly in terms of morphology, texture, thermal conductivity, electrical conductivity and mechanical properties. The interfacial thermal transport performance of carbon nanofiller/polymer composites was studied using a steady state method, with a view to their use as 'thermal interface adhesives and thermal pads. Roll milling was found to be the best method for producing composites with superior transport properties. GNP/rubbery epoxy and GNP/silicone composites produced by roll milling have thermal conductivities in the range of 1-3 W/m.K with 8-25 wt.% GNP. The thermal conductivities of the composites increase with increasing GNP loading and particle size but slightly decrease with silane-functionalisation of GNPs. Composites produced using GNPs ) synthesised (in-ho~se) via graphite, oxidation and thermal exfoliation offered improved transport properties compared to corresponding composites produced with commercial GNPs. Development of good interconnects between carbon nanofillers was found to be vital for producing composites with improved transport properties. GNP/silicone composites are more compliant materials than GNP/rubbery epoxy composites. VGCNF/rubbery epoxy composites have thermal conductivities in the range of 0.2-1.8 W/m.K with 2-40 wt.% VGCNF. VGCNFs increase the compressive strength of both rubbery epoxy and silicone without compromising their compliant nature. The thermal conductivity of CB/polymer composites reached ~O.2-0.3 W/m.K with 8-36 wt.% CB, depending upon the CB used. CB incorporation improved dispersion of GNPs in hybrid CB/GNP/rubbery epoxy composites and produced a thermal paste-type morphology. Similarly, VGCNFs improved the dispersion of GNPs in GNPNGCNF/rubbery epoxy hybrid composites but reduced the density of interconnects between GNPs. GNP/rubbery epoxy and VGCNF/rubbery epoxy composites offered the best performance as thermal interface adhesives compared to CB/rubbery epoxy and commercial thermal interface adhesive. The thermal contact resistance of the adhesives depends on their viscosity/conformability, bond line thickness, filler particle size, surface roughness of the substrate and thermal conductivity.
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BAYAT, AHMAD. "RF characterization and applications of carbon based composites." Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2715629.
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Graphene is a monolayer of carbon atoms with remarkable electronic and mechanical properties. The attractive electronic properties of thin and thick films made of carbon nanotubes (CNTs) and graphene are increasingly being exploited for environmental and biological sensors. In particular, their sensitivity, selectivity, fast response time, ability to operate at room temperature, and their passive nature (no power consumption) provide competitive advantages of CNTs in sensor applications. However, their design as RF wireless sensors requires the integration of an antenna with the sensor element. Moreover, while the plasmonic nature of graphene at terahertz frequency has been widely reported, investigations on the practical utility of graphene at the microwave frequencies used in wireless sensor nodes are sparse which is indicated in this thesis.
First, an ink comprising graphene thick films of different concentrations (12.5%, 25% and 33% in weight) is prepared for deposition, by screen printing. Detailed investigation of the surface morphology of the films using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) reveals that the graphene films present a homogeneous dispersion of the filler with a comparatively lower surface roughness at higher concentrations, and negligible agglomerates. The films are then printed in between copper electrodes on FR-4 substrate, commonly used in RF circuits, and the measured scattering parameters analyzed. A measurement-based RF equivalent circuit model of the graphene film is developed using a microstrip transmission line with a gap loaded by the film.
Second, investigation on various patch antennas with different substrates using Multi-Walled Carbon Nanotube (MWCNT) thin film deposition is addressed. Screen printing technique is used to insert a CNT film in a loading stub connected to the antenna patch. The variation of the CNT surface impedance modifies the resonant frequency from the reference value, as revealed by comparison of return loss measured with and without the CNT loading. This CNT stub loaded patch antenna can be used as a bio sensor.
Third, a printed RF slot ring resonator is configured with a graphene thin-film for sensor application. The conductive losses in the graphene film are characterized by dielectric spectroscopy and considered in the design. The graphene sensing element comprising the slot ring can be integrated with control electronics as a passive wireless sensor node. The novelty of this research is that RF losses are minimized by capacitively loading the ring at selective locations along its periphery. Dielectric spectroscopy is used to study variation in surface impedance of the film for various graphene loadings, and RF simulations are corroborated with measurements on graphene loaded slot ring resonators used in ammonia gas sensor application. The measurement steps are taken into consideration. As mentioned, the ring resonant frequency shift in presence of the ammonia gas is the factor used to sense the gas.
Fourth, a novel design of an aperture coupled antenna which is weakly coupled to an interdigitated capacitor (IDC) is presented that serves the dual purpose of antenna impedance matching and the sensing function, the latter enabled by a thick film of CNTs deposited on the IDC surface. Simulations using CNT films of varying conductivity (or surface impedance) reveal that a strong antenna resonance can be produced. Furthermore, a study of the patch antenna radiation pattern with and without the CNT film shows weak coupling between the film and the antenna (loss of 0.5 dB or less relative to patch alone). Thus, the sensor film and geometry can be independently optimized without affecting radiation pattern.
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Gan, Kok Dian Patrick. "Electrochemical studies at carbon-based electrodes." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:1a566ceb-8968-42d0-94fa-586ca2e6191c.
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Carbon electrodes have found widespread use in electrochemistry due to its broad versatility and low cost amongst other advantages. Recent innovations in carbon materials have added new dimensions to their utility in electrochemical applications. This thesis aims to investigate aspects of carbon materials, in particular boron-doped diamond (BDD) and nanocarbon composites, mainly for electrochemical analysis and energetics studies. The electrochemical behaviour of estradiol and other endocrine disrupting compounds was examined on the BDD electrode with different surface pretreatments, as well as on a nanocarbon-modified BDD electrode. It was shown that the precise control of surface chemical termination enabled the electrode to be tuned to exhibit diffusional or adsorptive voltammetry at oxidised and hydrogenated BDD interfaces respectively. Adsorption effects were also observed on the modified electrode leading to significant pre-concentration of the analyte onto the nanocarbon and a corresponding lowering of the limit of detection by ca three orders of magnitude to nanomolar levels. Surface modification of the BDD electrodes was then explored using a simple and convenient dropcast technique to deposit microcrystalline copper phthalocyanine onto the electrode. The influence of the surface chemical termination towards the interaction with the modifier compound was demonstrated in relation to the oxygen reduction reaction. Hydrogen terminated BDD modified in such a manner was able to significantly decrease the overpotential for the cathodic reaction by ca 500 mV when compared to the unmodified electrode while modified oxidised BDD showed no such electrocatalysis, signifying greater interaction of the phthalocyanine modifier with the hydrogenated surface. The lack of a further conversion of the peroxide product was attributed to its rapid diffusion away from the triple phase boundary (comprising the phthalocyanine microcrystallite, aqueous solution and BDD electrode) at which the reaction is expected to exclusively occur. Next carbon composites were studied in the form of carbon paste electrodes (CPEs). The practicality of a nanocarbon paste was established by cyclic voltammetry with several well-characterised redox systems commonly used to test electrode activity and was found to exhibit comparable behaviour to the more typical graphitic formulation. Reversible uptake of some analytes was observed at the CPEs, giving rise to complex double peak voltammetry. This uptake phenomenon was then further examined at the nanocarbon paste electrode to monitor the transfer of species between two dissimilar liquid phases. The interfacial behaviour gave rise to voltammetric peaks which were assigned to species originating from the aqueous, binder and carbon phases respectively and this enabled the measurement of Gibbs energies of transfer between oil and aqueous phases. Finally the effect of different ionic liquids as binder for carbon-ionic liquid composite electrodes was studied. Some ionic liquids were demonstrated to offer benefits in comparison to oil in the fabrication of carbon paste type electrode due to an increased adsorption of analytes. The ionic âliquidâ (with a melting point above room temperature) <i>n</i>-octyl-pyridinium hexafluorophosphate [C<sub>8</sub>py][PF<sub>6</sub>] was shown to be useful in combination with carbon nanotubes as a composite electrode or as a modifier to a screen-printed electrode to significantly enhance the sensitivity of electrochemical detection via adsorptive stripping voltammetry. Overall the carbon-based electrodes studied have demonstrated excellent utility as electrode materials in the areas of electrochemical sensing and energetics investigations.
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Kuemmerle, Daniel Lange. "Strengthening of concrete bridge decks using carbon-based composite materials." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/20694.
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Böhm, Robert, Mike Thieme, Daniel Wohlfahrt, Daniel Sebastian Wolz, Benjamin Richter, and Hubert Jäger. "Reinforcement Systems for Carbon Concrete Composites Based on Low-Cost Carbon Fibers." Molecular Diversity Preservation International MDPI, 2018. https://tud.qucosa.de/id/qucosa%3A33323.
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Carbon concrete polyacrylonitrile (PAN)/lignin-based carbon fiber (CF) composites are a new promising material class for the building industry. The replacement of the traditional heavy and corroding steel reinforcement by carbon fiber (CF)-based reinforcements offers many significant advantages: a higher protection of environmental resources because of lower CO2 consumption during cement production, a longer lifecycle and thus, much less damage to structural components and a higher degree of design freedom because lightweight solutions can be realized. However, due to cost pressure in civil engineering, completely new process chains are required to manufacture CF-based reinforcement structures for concrete. This article describes the necessary process steps in order to develop CF reinforcement: (1) the production of cost-effective CF using novel carbon fiber lines, and (2) the fabrication of CF rebars with different geometry profiles. It was found that PAN/lignin-based CF is currently the promising material with the most promise to meet future market demands. However, significant research needs to be undertaken in order to improve the properties of lignin-based and PAN/lignin-based CF, respectively. The CF can be manufactured to CF-based rebars using different manufacturing technologies which are developed at a prototype level in this study.
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Camponeschi, Erin L. "Dispersion and alignment of carbon nanotube polymer based composites." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/26503.
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Thesis (Ph.D)--Materials Science and Engineering, Georgia Institute of Technology, 2008.<br>Committee Co-Chair: Dr. Hamid Garmestani; Committee Co-Chair: Dr. Rina Tannenbaum; Committee Member: Dr. Kenneth Gall; Committee Member: Dr. Meisha Shofner; Committee Member: Dr. Thomas Sanders. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Zhang, Shengwen. "Carbon nanotube based composites for electricity storage in supercapacitors." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/13095/.
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In the context of fossil-fuel shortage and climate change, the production, conversion, storage and distribution of energy have become the focus of today's world. Supercapacitors, with their unique energy and power density specifications, cover the application gap between batteries and conventional capacitors and hence making valuable contributions in energy storage and distribution. Caron nanotubes (CNTs), with their unique aspect ratio and other distinctive physical, electrochemical and electronic properties have been chosen to enhance traditional electrode materials for supercapacitors, i.e. conducting polymer and transition metal oxides. Polypyrrole/CNTs (PPy/CNTs), polyaniline/CNTs (PAni/CNTS) and manganese oxides/CNTs (MnOx/CNTs) nanocomposites have been synthesised through chemical redox reaction in aqueous solutions. The nanocomposites have been characterised with scanning electron microscopy (SEM), transition electron microscopy (TEM), BET nitrogen surface adsorption, X-Ray diffraction (XRD), thermogravimetric analysis (TGA), infrared and X-ray photoelectron spectroscopy (XPS) to examine and to select the appropriate candidates as electrode materials. Electrochemical characterisations, i.e. cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), have been conducted with the selected nano-composites in a classic three-electrode compartment cell. Desirable capacitive behaviour, with long-term cycling stability, has been identified within appropriate potential windows for each of the nanocomposites. Asymmetric and symmetric supercapacitor prototypes have been constructed with the nanocomposites synthesised and characterised in this work. Carbon materials, due to their higher hydrogen overpotential in aqueous systems, have been proved to be good negative electrode materials in this study. Excellent specific capacitances of 1.2 F cm-2, 0.83 F cm-2 and 0.96 F cm-2 have been achieved with PAni/CNTs, PPy/CNTS and MnOx/CNTs electrodes respectively. Supercapacitor-stacks with multiplied cell voltage have been constructed with both symmetric and asymmetric prototype cells. Therefore, it has been confirmed that desirable cell voltage and capacitance can be achieved by connecting appropriate individual cells in parallel and in series to cater the requirements of the end-users. Last but not least, the prototype cells have been fitted with equivalent circuits to gain an insight into the resistive and capacitive contributions from each component. Suggestion for improvement has been given based on the simulation results of the prototype cells.
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Rajpurohit, Ashok. "Development of advanced carbon/glass fibre based hybrid composites." Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLM020.
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Les composites hybrides offrent un moyen efficace d'améliorer les propriétés mécaniques des matériaux composites. Cette thèse vise à comprendre le comportement mécanique et l'effet synergique offerts par de tels composites hybrides sous plusieurs conditions de chargement. L'accent est mis, non seulement sur la caractérisation mécanique, mais également sur le développement et l'optimisation de nouvelles générations de renforts hybrides, permettant ainsi une hybridation aussi bien au niveau des nappes, qu’au niveau des mèches et des fibres. Dans ce travail, les fibres de carbone et de verre sont choisies comme les deux types de renforts pour les composites hybrides. Les propriétés de ces fibres unitaires sont d'abord caractérisées pour étudier l'impact des procédés textiles. De nouveaux renforts unidirectionnels ont été fabriqués après avoir optimisé les procédés, tels que la technologie UD cousu et l'étalement des fibres. Les composites ont été fabriqués via RTM basse pression en utilisant une résine époxy. Les caractéristiques en raideur et en résistance des composites de référence, des hybrides inter-plis, intra-plis et fibre à fibre ont ensuite été caractérisées dans des conditions de charge quasi-statique en traction, compression et flexion. L'effet d’hybridation (synergique) a été évalué pour ces composites en comparant les propriétés du composite hybride avec un composite de référence en carbone. Afin de comprendre le comportement à rupture de ces composites dans différentes conditions de charge, une étude de fractographie a été réalisée. Les hybrides inter-plis font apparaître une légère augmentation de la déformation à rupture en traction mais présentent une synergie négative pour toutes les autres conditions. Les hybrides intra-plis montrent eux, un effet synergique pour les résistances à la traction et à la compression, sans réduire leur déformation à rupture. Un composite hybride fibre à fibre réalisé par étalement montre une performance mécanique supérieure par rapport à d'autres hybrides. Les résultats présentés révèlent les avantages potentiels de l'hybridation à différents niveaux et dispersions. Les résultats ouvrent une voie pour les futurs travaux sur les composites hybrides et leurs procédés<br>Hybrid composites offer an effective way of enhancing mechanical properties of composite materials. This thesis aims to understand the mechanical behaviour and synergistic effect offered by such hybrid composites in several loading conditions. The focus not only lies on mechanical characterisation but also on development and optimization of new generation of hybrid reinforcements thus allowing hybridization both at ply levels and at tow and fibre levels. In this work, carbon and glass fibres are chosen as the two types of reinforcements for hybrid composites. Single fibre properties of these fibres were first characterised to study the effect of textile processes. Novel unidirectional reinforcements have been fabricated after optimising the processes such as unidirectional stitching and spreading technology. Composites were manufactured via low pressure RTM process using an epoxy resin. Stiffness and failure characteristics of reference, interply, intraply and intermingled hybrid composites were then characterised in quasi-static tensile, compression and flexural loading conditions. The hybrid (synergistic) effect were evaluated for these composites by comparing the hybrid composite properties with a carbon reference composite. To understand the failure behaviour under different loading conditions, a fractography study was conducted. Interply hybrids slightly increase the failure strain in tension but demonstrate negative synergy in all other properties. On the other hand, intraply hybrids show a synergistic effect in both tensile and compressive strengths, while not reducing the failure strain. A spread tape intermingled hybrid composite demonstrates a superior mechanical performance when compared to other hybrids. The presented results reveal the potential benefits of hybridisation at different levels and dispersions. The results provide a driving force for future work on hybrid composites and their processing
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Alresheedi, Bakheet. "Supercapacitors Based on Carbon Nanotube Fuzzy Fabric Structural Composites." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1354600361.
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Di, Giacomo Raffaele. "Carbon nanotube based networks, bio-nano-composites and sensors." Doctoral thesis, Universita degli studi di Salerno, 2013. http://hdl.handle.net/10556/1326.
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2011 - 2012<br>The formation of a photosensitive device due to the local breakdown in an MOS structure with an impurity containing oxide layer has been observed. A stepwise breakdown of the oxide layer resulted in the formation of a transistor like characteristics with further on stable current-voltage characteristics. A high value of the photosensitivity of the resulting structure has been found, when illuminated with white or blue light. This can be explained by the formation of a local p-n junction during electrical breakdown due to out-diffusion of dopants from the oxide into the underlying silicon substrate. The development of the photocurrent has been monitored during breakdown formation. This monitoring procedure can be used for the optimization of the photosensitive device.
After these experiments a defect-free oxide was produced and tested. Multi walled carbon nanotubes (MWCNTs) have been deposited by casting electrophoresis on top of this SiO2 layer.
Using three different microscopy techniques: namely Atomic Force Microscopy, Secondary Electron Microscopy and Focused Ion Beam Microscopy, the geometry of the interconnection of a single junction between the deposited MWCNTs has been investigated in detail. A very particular twisted interconnection geometry has been observed. Furthermore a strong stability of the sample in time has been observed proving a strong adhesion of the tubes to the SiO2 surface.
Furthermore, MWCNTs were deposited from two different solutions leading to different results regarding their morphology: an almost bi-dimensional “carpet” of MWCNTs, and a network composed of a very limited number of MWCNTs. The “carpet” was obtained using a solution with 1% of sodium dodecyl sulfate in de-ionized water, saturated with MWCNTs. This solution was very stable in time and reproducible carbon nanotube networks could be obtained. All the pure nanotube networks were deposited by di-electrophoresis inside an aluminium contact gap with a contact
distance of 3μm. After the deposition the temperature dependent conductivity of the MWCNTs “carpet” inside the aluminum contact gap has been determined. The temperature behavior of the conductivity shows a good qualitative agreement with the fluctuation induced tunneling model for disordered materials. A rapid reduction of the random telegraph noise present in the virgin devices has been observed after relatively short application of a constant voltage. This increases the possibilities to use aluminum contacts for electronic CNT devices like sensors, where device stability is more important than high current levels. When a different solvent has been used, that resulted in a much lower concentration of CNTs within the micro-gap, a stable electrical behavior has not been achieved.
Successively using the same technique for the solution of MWCNTs a Candida albicans/multi walled carbon nanotube (Ca/MWCNTs) composite material has been produced. It can be used as a temperature-sensing element operative in a wide temperature range (up to 180 °C). The Ca/MWCNTs composite has excellent linear current-voltage characteristics when combined with coplanar gold electrodes. Growing cells of C. albicans were used to structure the carbon nanotube-based composite. The fungus C. albicans combined with MWCNTs co-precipitated as an aggregate of cells and nanotubes that formed a viscous material. Microscopic analyses showed that Ca/MWCNTs formed an artificial tissue. Slow temperature cycling was performed for up to 12 days showing a stabilization of the temperature response of the material. As another application of this new bio-nano-composite layer, the realization of a flexible transparent conductive film has been demonstrated.
A more general procedure in order to obtain novel artificial materials has been proposed and realized using isolated tobacco cells in combination with carbon nanotubes. The electrical, mechanical, optical, thermo-electrical properties of these materials have been determined. Using tobacco cells, a material with low mass density and mechanical properties suitable for structural applications, along with high values of the electrical conductivity has been obtained. Measurements of the mechanical and electrical behavior have been combined with theoretical modeling. These findings indicate a procedure for next generation cyborg nano-composite materials. [edited by authors]<br>XI n.s.
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Daga, Vijay. "High temperature deformation of pan-based carbon fiber precursors." Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/11185.
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NARASIMHADEVARA, SUHASINI. "PROCESSING OF NANOCOMPOSITES BASED ON EPOXY AND CARBON NANOTUBES." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1119466758.
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Rangie, Massod. "The processing and thermal stability of PMR based carbon fibre composites." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265586.
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Volodin, A. A., B. P. Tarasov, A. A. Belmesov, E. V. Gerasimova, A. D. Zolotarenko, and D. V. Shchur. "Electro-Conductive Composites Based on Metal Oxides and Carbon Nanostructures." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35124.
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Optimal conditions were found for the formation of carbon-oxide composites by the treatment of mixtures
of oxides of aluminum or titanium with carbon nanotubes and nanofibers in a planetary ball mill.
The dependences of the electrical conductivity of composites on the content of carbon nanomaterials (1-5%
by mass) were determined. It is shown that the addition of 3%(wt) of CNT to the oxides leads to a sharp increase
in the electrical conductivity: from 5.0×10-8 to 2.8×10-4 S/cm for Al2O3 and from 5.0×10-6 to 2.2×10-2
S/cm for TiO2. It was shown that the carbon-oxide composites are promising carriers of the catalysts of
electrode processes in electrochemical devices. It was revealed that Pt/TiO2 - CNT catalyst containing 5%
(mass) of carbon nanotubes has the best catalytic activity in oxygen reduction, in an electrode-modeling
cathode of a fuel cell.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35124
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Yesil, Sertan. "Processing And Characterization Of Carbon Nanotube Based Conductive Polymer Composites." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611984/index.pdf.
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The aim of this study was to improve the mechanical and electrical properties of conductive polymer composites. For this purpose, different studies were performed in this dissertation. In order to investigate the effects of the carbon nanotube (CNT) surface treatment on the morphology, electrical and mechanical properties of the composites, poly(ethylene terephthalate) (PET) based conductive polymer composites were prepared by using as-received, purified and modified carbon nanotubes in a twin screw extruder.
During the purification of carbon nanotubes, surface properties of carbon nanotubes were altered by purifying them with nitric acid (HNO3), sulfuric acid (H2SO4), ammonium hydroxide (NH4OH) and hydrogen peroxide (H2O2) mixtures. Electron Spectroscopy for Chemical Analysis (ESCA) results indicated the removal of metallic catalyst residues from the structure of carbon nanotubes and increase in the oxygen content of carbon nanotube surface as a result of purification procedure. Surface structure of the purified carbon nanotubes was also modified by treatment with sodium dodecyl sulfate (SDS), poly(ethylene glycol) (PEG) and diglycidyl ether of Bisphenol A (DGEBA). Fourier Transformed Infrared Spectroscopy (FTIR) spectra of the carbon nanotube samples indicated the existence of functional groups on the surfaces of carbon nanotubes after modification. All composites prepared with purified and modified carbon nanotubes had higher electrical resistivities, tensile and impact strength values than those of the composite based on as-received carbon nanotubes, due to the functional groups formed on the surfaces of carbon nanotubes during surface treatment.
In order to investigate the effects of alternative composite preparation methods on the electrical and mechanical properties of the composites, in-situ microfiber reinforced conductive polymer composites consisting of high density polyethylene (HDPE), poly(ethylene terephthalate) and carbon nanotubes were prepared in a twin screw extruder followed by hot stretching of PET/CNT phase in HDPE matrix. Composites were produced by using as-received, purified and PEG treated carbon nanotubes. SEM micrographs of the hot stretched composites pointed out the existence of in-situ PET/CNT microfibers dispersed in HDPE matrix up to 1 wt. % carbon nanotube loadings. Electrical conductivity values of the microfibrillar composites were higher than that of the composites prepared without microfiber reinforcement due to the presence of continuous PET/CNT microfibers with high electrical conductivity in the structure.
To investigate the potential application of conductive polymer composites, the effects of surfactant usage and carbon nanotube surface modification<br>on the damage sensing capability of the epoxy/carbon nanotube/glass fiber composite panels during mechanical loadings were studied. Surface modification of the carbon nanotubes was performed by using hexamethylene diamine (HMDA). 4-octylphenol polyethoxylate (nonionic) (Triton X-100) and cetyl pyridinium chloride (cationic) (CPC) were used as surfactants during composite preparation. Electrical resistivity measurements which were performed during the impact, tensile and fatigue tests of the composite panels showed the changes in damage sensing capabilities of the composites. Surface treatment of carbon nanotubes and the use of surfactants decreased the carbon nanotube particle size and improved the dispersion in the composites which increased the damage sensitivity of the panels.
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Hsieh, Yu-Yun. "Nanostructured Carbon-Based Composites for Energy Storage and Thermoelectric Applications." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin157322525150617.
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Seon, Guillaume. "Finite element-based failure models for carbon/epoxy tape composites." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28117.
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Perkins, Mark James. "Carbon-based negative electrode materials for rechargeable lithium batteries." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326801.
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Chaganti, Pradeep. "PROTECTION OF CARBON/CARBON AIRCRAFT BRAKES FROM OXIDATION USING PHOSPHOROUS BASED ANTI-OXIDANT SYSTEM." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/644.
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Carbon/Carbon (C/C) composite is defined as a carbon fiber reinforced carbon matrix. Since 1958 research has been carried out on the C/C composites. The main reason for the development of new C/C composites is the number of advantages it has to offer when compared with the regular materials. The areas where C/C composites are being used extensively are aerospace, military, etc. These C/C composites have better physical, mechanical, thermal properties when compared to steel. That is the reason C/C brakes made a huge impact in the aerospace industry. The main drawback associated with the C/C brakes which are used in aerospace applications is the oxidation of the composite at higher temperatures. Also other problem linked with the C/C brake is the migration of the inhibitors on to the friction surface of the brake which can eventually decrease the friction coefficient of the brake material. So, characterizing the commercially available Anti-Oxidant(A/O) system, developing a new A/O system which can not only provide better oxidation protection, but also an improved anti-oxidant migration resistance will be our main goal of this project.
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Ho, Mui Yen. "Transition metal oxide and phosphate-based/carbon composites as supercapacitor electrodes." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/40274/.
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Electrochemical capacitors, also known as supercapacitors, have attracted considerable attention over the past decades owing to their higher power density, long cycle life and moderate energy density compared. A high-performance supercapacitor integrates innovative electrode materials with desirable properties coupled with low cost and sustainability. In this thesis, a series of low cost transition metal oxide-activated carbon composite materials, lithium iron phosphate-activated carbon composite materials as well as metal oxide-graphene composite materials were prepared, characterized and evaluated as supercapacitor electrodes. Iron oxide (Fe3O4) – activated carbon (AC), zinc oxide (ZnO) – AC and titanium oxide (TiO2) – AC nanocomposites were prepared by using simple mechanical mixing method. The charge storage capabilities of these metal oxide-based composites with different loading ratios were evaluated in both mild aqueous 1 M Na2SO3 and 1 M Na2SO4 electrolytes. The incorporation of small amount of metal oxides onto AC could effectively enhance the capacitive performance of pure AC electrodes. It is believed that the presence of metal oxide nanoparticles can provide favourable surface adsorption sites for sulphite anions (SO32-). Nevertheless, bulk increasing of the metal oxide content is found to distort the capacitive performance and deteriorate the specific surface area of the electrode, mainly due to the aggregation of the metal oxide particles within the composite. On the other hand, composite materials consisting of lithium iron phosphate (LiFePO4) and AC exhibit high specific capacitance of 112.41 F/g in 1 M Na2SO3 with the incorporation of 40 wt % of LiFePO4. The synergistic effect between the faradaic battery type materials and the EDLC-based materials is greatly demonstrated. The intercalation and extraction of Li+ ions in LiFePO4 lattices are responsible for the reversible Faradaic reaction on top of the adsorption and de-adsorption of SO32- anions from Na2SO3 electrolyte. In the preparation of SnO2-graphene and MoO3-graphene nanocomposites, low-temperature solvothermal method using mild reducing agents was adopted. The preparation steps do not require high pressure or extreme synthetic condition and do not involve the usage of hazardous reactants. The electrochemical results of SnO2-graphene composite electrodes demonstrate that the composite electrodes possess a high specific energy (14 Wh/kg) with 93 % capacitive retention after 1500 cycles while MoO3-graphene composite electrodes yield an enhanced specific energy (16.3 Wh/kg) which is 28 % higher than that of pure MoO3 (11.8 Wh/kg). A maximum specific capacitance of 99 F/g was obtained from the optimized SnO2-graphene composite electrodes while a high average specific capacitance of 148 F/g was achieved for MoO3-graphene composites at a scan rate of 5mV/s in neural 1 M Na2SO3 electrolyte. The incorporation of graphene onto both SnO2 and MoO3 respectively, can promote the electrochemical utilization of metal oxides as well as the electrical conductivity of the electrodes. The graphene sheet serves as a good support in promoting effective charge transfer for redox reactions of MoO3. Additionally, deposition of metal oxides on graphene sheets prevents the graphene sheets from agglomeration, resulting in facile ion transportation pathway for electrolyte to access the surface of active material.
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Hoang, Van Chinh. "Biomass-derived carbon dot-based composites for energy storage and conversion." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/25016.
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This thesis focuses on the fabrication of sustainable and environment-friendly carbon dots (CDs) using agricultural biomass as natural abundant carbon precursors, followed by the synthesis of 3D hierarchical porous aerogels of biomass-derived CDs with reduced graphene oxide (RGO). The electrochemical properties of the CD-based composites have been systematically studied for their use in supercapacitors and oxygen reduction reaction (ORR).
First, we investigated the effect of the mass loading of nitrogen-doped CDs on the electrochemical properties of the RGO/CDs hybrid by varying the mass ratio of graphene oxide to CDs from 4:1, 2:1 to 1:1. We found that cauliflower leaf-derived N-doped CDs acted as intercalators to hamper the aggregation/restacking of graphene interlayers effectively, which resulted in greater specific surface area and total pore volume. The incorporation of intrinsically N-doped CDs onto graphene nanosheets has significantly increased pseudo-capacitance active sites generated by O/N-containing groups on N-doped CDs, decreased the impedance, and enhanced the proton diffusion to the electrodes, compared to those of RGO.
Next, the electrochemical performance of the RGO/CDs was further improved by a simple chemical reduction by means of HI acid, which not only deoxygenated the hybrid to enhance its electronic/ionic conductivity, but also doped iodine heteroatoms into the carbon frameworks. We optimized the percentage of I-doping by controlling the time of the HI vapor reduction process ranging from 0 to 30 minutes. The HI vapor reduction significantly affected the electronic/ionic conductivity, the formation of active sites for pseudocapacitance induced by O/I functional groups, charge transfer resistance and OH- ion diffusivity.
Finally, the synthesized materials were also employed as ORR electrocatalysts in 0.1 M KOH. We found that the I-doping remarkably increased the ORR catalytic active sites, leading to a rise in its electrochemically active surface area.
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Lutz, Vincent. "Carbon nanotubes as nanofillers or fibers for multifunctional epoxy-based composites." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0039.
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L’utilisation de composites à matrice thermodurcissable et fibres continues est en constante progression dans le secteur aéronautique, ferroviaire, et automobile. Afin d’améliorer les composites obtenus, notamment leur résistance à l’impact et leur conductivité électrique, des nanocharges organiques ou inorganiques peuvent être ajoutées. Les nanotubes de carbone (CNT) font partie des candidats les plus prometteurs pour le renforcement de composites à multi-échelle. Cependant, il s’avère difficile de contrôler la dispersion, la répartition et l’orientation des CNT, après les avoir mélangés aux prépolymères. Une nouvelle stratégie d’insertion des CNT dans un composite consiste à combiner des fibres de CNT avec des fibres de carbone. L’orientation et l’organisation structurelle des CNT au sein de la fibre permettent d’obtenir d’excellentes propriétés mécaniques et électriques. Dans notre étude, les propriétés de fibres contenant exclusivement des CNT, obtenues par direct spinning, ont été comparées à celles de fibres de carbone (non-ensimées, ensimées, et CNT en surface). Différentes interfaces entre les fibres de CNT, fibres de carbone et deux types de matrices époxy (de TG très différentes) ont été générées et testées par des essais de fragmentation de fibre dans la matrice. La contrainte de cisaillement interfaciale fibre/matrice a été évaluée afin de déterminer l’influence des diverses fibres et ensimages sur les performances mécaniques de composites à matrice organique et à fibres continues. En outre, la nature de l’adhésion et la qualité de l’interphase entre la matrice et la fibre ont été caractérisées par plusieurs techniques d’analyses et d’observations à multi-échelles<br>Nowadays, polymer-matrix composites reinforced with carbon fibers are increasingly used in the whole transport sector (aerospace, automotive and railway industries). However, the obtained parts still suffer from low impact resistance and low damage tolerance. To improve these properties, the matrix precursors have to be combined with organic or inorganic compounds to lead to multi-phased matrices. Among them, carbon nanotubes (CNT) are especially promising for targeting multi-scale reinforcement. Since high quality of the parts are required, continuous-fibers-reinforced composites can be produced by resin transfer molding (RTM) which also offers a reduced cost if compared with high temperature- and high pressure-based processes. However, RTM requires a very low viscosity of the polymer precursors and CNT-filled precursors are far too viscous to be injected on dry performs. In addition, this strategy does not allow for a control of the CNT location and orientation in the final part. In this study, innovative ways have been developed to insert CNT in the preform with local positioning and defined orientation. Deliveries of CNT in the matrix, from a neat carbon multi-nanotubes fiber produced by direct spinning, or from a CNT grown on carbon fiber were investigated in two types of epoxy matrices (with very different TG). Different polymer matrix/fiber interfaces have been generated using neat carbon multi-nanotubes fiber, CNT grown on carbon fiber and conventional carbon fiber, with or without sizing. A fine mechanical characterization of various fibers and particularly the measurement of single fiber interfacial properties have been performed in order to determine mechanical performance of continuous fiber reinforced composites. In addition, the nature of adhesion and quality of matrix/fiber interface have been fully evaluated by different multi-scale analyses and suitable microstructural observations
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LASIO, BARBARA. "Fabrication of Cu-based metal matrix composites reinforced with carbon nanofillers." Doctoral thesis, Università degli Studi di Cagliari, 2019. http://hdl.handle.net/11584/260760.
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The thesis takes inspiration from the worldwide issues related to the shortage of critical raw materials (CRMs) and the need of finding sustainable alternatives to CRMs within fields and sectors strategic to the well-being and economy of industrialized countries.
The research activity has been focused on the fabrication of Cu-matrix composites reinforced with carbon nanofillers, nano-graphite and graphene in particular. This class of composites attracts considerable interest as a consequence of the broad spectrum of applications Cu-MCs could find due to their thermal and electric conductivities, self-lubricating properties of graphite, cost-effectiveness and availability.
Ball milling (BM) and spark plasma sintering (SPS) have been combined to provide an innovative methodology to fabricate Cu-MCs reinforced with carbon nanofillers enabling the fine dispersion of nanoparticles into the Cu matrix. Specifically, a two-stage cycle involving BM first and, then, SPS has been shown to result in the dispersion of graphite particles in relatively large Cu grains. The iteration of cycles allows the refinement of graphite nanoparticles and their dispersion in Cu powders on the microscopic scale, mostly at grain boundaries, and the subsequent incorporation of nanoparticles into Cu grains due to grain growth mechanisms activated and promoted by high temperatures during SPS.
Molecular level mixing has been also tested to obtain Cu-MCs reinforced with graphene starting from liquid solutions of Cu nanoparticles and graphene. In particular, graphene was dispersed during the redox synthesis to obtain Cu nanopowder, subsequently consolidated by SPS.
Despite the intrinsic different between the two methods, it has been possible to prepare Cu-MCs with graphite nanoparticles and graphene as dispersoids. Structural and microstructural characterization indicate that dispersoids are finely dispersed into the Cu matrix. Nanoindentation measurements clearly demonstrate the significant enhancement of mechanical properties, thus providing an important clue to the validity of the methodology developed.
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Imbayan, Mike. "DEVELOPMENT OF SILLICON BASED OVERCOAT FOR HIGH TEMPERATURE OXIDATION PROTECTION OF CARBON-CARBON COMPOSITES AIRCRAFT BRAKE." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1680.
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Much research of Anti-Oxidant has been developed and is still being developed to protect Carbon-Carbon(C/C) material from oxidizing. C/C materials tend to lose their mechanical properties due to the oxidation. The aerospace brake industries have conducted a lot of research on this, because C/C material is an excellent material to be used for brake systems if a good oxygen protection is developed for it. The research performed by Dr.Jarlen Don detected a problem with the oxidation at high temperatures with the current composition. Phosphorus based coating does not protect C/C for more than 15 hours at 871C. By doing a multi-layer coating of the anti-oxidant, the anti-oxidant will be able to protect the brake systems better at a high temperature. To address the problem, research and experiments were conducted to protect oxidation at higher temperatures by using a silicon-based anti-oxidant. Silicon based overcoat will be the top layer of the anti-oxidant while the bottom will be the phosphorus based anti-oxidant that previously has been coated.
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Adusei, Paa Kwasi. "Carbon Nanotube-Based Composite Fibers for Supercapacitor Application." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1561996824580323.
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Boehle, Matthew C. "Synthesis and Characterization of a Carbon Nanotube Based Composite Strain Sensor." University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1462201576.
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Sok, Vibol. "Amperometric enzyme-based detection of agriculturalpesticides on novel carbon nano-onion composites." Doctoral thesis, Universitat Rovira i Virgili, 2018. http://hdl.handle.net/10803/665119.
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Actualment hi ha una gran preocupació sobre l'ús de pesticides en l'agricultura i els seus possibles efectes secundaris. Això fa que el desenvolupament de sistemes de detecció sensibles i robustos sigui un pas important en aquesta direcció. D'altra banda, les nano-cebes de carboni (CNOs) són materials molt atractius i prometedors amb estructures definides i propietats electroquímiques notables que amb prou feines s'han estudiat en biosensors. L'objectiu general d'aquesta tesi és estudiar la interacció de diferents plaguicides amb peroxidasa i tirosinasa amb l'objectiu de desenvolupar biosensors per a la seva detecció basats en elèctrodes modificats amb CNOs. Per aconseguir aquest objectiu general, s'ha estudiat: 1) la inhibició de les activitats de peroxidasa i tirosinasa per tres dels plaguicides més utilitzats (2,4-D, 2,4,5-T i glifosat), 2) l'ús d'CNOs oxidades com a suports per a la immobilització d'enzims i un estudi de l'activitat i estabilitat dels enzims immobilitzades, 3) el desenvolupament de biosensors electroquímics per a detecció dels plaguicides abans esmentats basats en els elèctrodes modificats amb composites contenint enzims i CNOs. Aquesta tesi és, per tant, una contribució a un camp de ràpid creixement relacionat amb el desenvolupament de noves classes de nanomaterials de carboni que té com a objectiu ampliar les seves aplicacions actuals en la construcció de sistemes de detecció nous amb millors prestacions.<br>Actualmente existe una gran preocupación sobre el uso de pesticidas en la agricultura y sus posibles efectos secundarios. Esto hace que el desarrollo de sistemas de detección sensibles y robustos sea un paso importante en esta dirección. Por otro lado, las nano-cebollas de carbono (CNOs) son materiales muy atractivos y prometedores con estructuras definidas y propiedades electroquímicas notables que apenas se han estudiado en biosensores. El objetivo general de esta tesis es estudiar la interacción de diferentes plaguicidas con peroxidasa y tirosinasa con el objetivo de desarrollar biosensores para su detección basados en electrodos modificados con CNOs. Para lograr este objetivo general, se ha estudiado: 1) la inhibición de las actividades de peroxidasa y tirosinasa por tres de los plaguicidas más utilizados (2,4-D, 2,4,5-T y glifosato), 2) el uso de CNOs oxidadas como soportes para la inmovilización de enzimas y un estudio de la actividad y estabilidad de las enzimas inmovilizadas, 3) el desarrollo de biosensores electroquímicos para detección de los plaguicidas antes citados basados en los electrodos modificados con composites conteniendo enzimas y CNOs. Esta tesis es, por lo tanto, una contribución a un campo de rápido crecimiento relacionado con el desarrollo de nuevas clases de nanomateriales de carbono que tiene como objetivo ampliar sus aplicaciones actuales en la construcción de sistemas de detección novedosos con mejores prestaciones.<br>There is currently a strong concern on the use of pesticides in agriculture and their possible side effects. This makes the development of sensitive and robust detection systems an important step in this direction. On the other hand, carbon nano-onions are very attractive and promising materials with defined structures and remarkable electrochemical properties that have been scarcely studied in biosensing. The overall objective of this thesis is to study the interaction of different pesticides with peroxidase and tyrosinase with the aim to develop biosensors for pesticide detection based on CNO-modified electrodes. To achieve this general objective, the following aspects have been focused on: 1) the inhibition of peroxidase and tyrosinase activities by three of the most used pesticides (2,4-D, 2,4,5-T and glyphosate), 2) the use of oxidized CNOs as supports for the immobilization of enzymes and a study of the activity and stability of the immobilized enzymes, 3) the development of electrochemical biosensors for pesticide detection based on the prepared CNO-enzyme modified electrodes. This thesis is thus a contribution to a rapidly growing field related with the development of new classes of carbon nano-onion based nanomaterials that aims at expanding their current applications in the construction of novel detection systems with improved performances.
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Ma, Peng Cheng. "Novel surface treatment, functionalization and hybridization of carbon nanotubes and their polymer-based composites /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?MECH%202008%20MA.
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Schneider, Kai, Matthias Lieboldt, Marco Liebscher, et al. "Mineral-Based Coating of Plasma-Treated Carbon Fibre Rovings for Carbon Concrete Composites with Enhanced Mechanical Performance." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-227074.
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Surfaces of carbon fibre roving were modified by means of a low temperature plasma treatment to improve their bonding with mineral fines; the latter serving as an inorganic fibre coating for the improved mechanical performance of carbon reinforcement in concrete matrices. Variation of the plasma conditions, such as gas composition and treatment time, was accomplished to establish polar groups on the carbon fibres prior to contact with the suspension of mineral particles in water. Subsequently, the rovings were implemented in a fine concrete matrix and their pull-out performance was assessed. Every plasma treatment resulted in increased pull-out forces in comparison to the reference samples without plasma treatment, indicating a better bonding between the mineral coating material and the carbon fibres. Significant differences were found, depending on gas composition and treatment time. Microscopic investigations showed that the samples with the highest pull-out force exhibited carbon fibre surfaces with the largest areas of hydration products grown on them. Additionally, the coating material ingresses into the multifilament roving in these specimens, leading to better force transfer between individual carbon filaments and between the entire roving and surrounding matrix, thus explaining the superior mechanical performance of the specimens containing appropriately plasma-treated carbon roving.
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Grove, Dale A. III. "Mathematical model of solid state thermo-oxidative stabilization of acrylic precursors for carbon fibers : evaluation of the properties of carbon fibers produced from melt-spun pan-based fibers." Thesis, Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/11111.
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Dinh, Nghia Trong, and Olfa Kanoun. "Temperature-Compensated Force/Pressure Sensor Based on Multi-Walled Carbon Nanotube Epoxy Composites." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-175255.
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In this study, we propose a multi-walled carbon nanotube epoxy composite sensor for force and pressure sensing in the range of 50 N–2 kN. A manufacturing procedure, including material preparation and deposition techniques, is proposed. The electrode dimensions and the layer thickness were optimized by the finite element method. Temperature compensation is realized by four nanocomposites elements, where only two elements are exposed to the measurand. In order to investigate the influence of the filler contents, samples with different compositions were prepared and investigated. Additionally, the specimens are characterized by cyclical and stepped force/pressure loads or at defined temperatures. The results show that the choice of the filler content should meet a compromise between sensitivity, temperature influence and noise behavior. At constant temperature, a force of at least 50N can be resolved. The measurement error due to the temperature influence is 150N in a temperature range of –20°C–50°C.
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Hart, Robert James. "Electrical resistance based damage modeling of multifunctional carbon fiber reinforced polymer matrix composites." Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5493.
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In the current thesis, the 4-probe electrical resistance of carbon fiber-reinforced polymer (CFRP) composites is utilized as a metric for sensing low-velocity impact damage. A robust method has been developed for recovering the directionally dependent electrical resistivities using an experimental line-type 4-probe resistance method. Next, the concept of effective conducting thickness was uniquely applied in the development of a brand new point-type 4-probe method for applications with electrically anisotropic materials. An extensive experimental study was completed to characterize the 4-probe electrical resistance of CFRP specimens using both the traditional line-type and new point-type methods. Leveraging the concept of effective conducting thickness, a novel method was developed for building 4-probe electrical finite element (FE) models in COMSOL. The electrical models were validated against experimental resistance measurements and the FE models demonstrated predictive capabilities when applied to CFRP specimens with varying thickness and layup. These new models demonstrated a significant improvement in accuracy compared to previous literature and could provide a framework for future advancements in FE modeling of electrically anisotropic materials. FE models were then developed in ABAQUS for evaluating the influence of prescribed localized damage on the 4-probe resistance. Experimental data was compiled on the impact response of various CFRP laminates, and was used in the development of quasi- static FE models for predicting presence of impact-induced delamination.
The simulation-based delamination predictions were then integrated into the electrical FE models for the purpose of studying the influence of realistic damage patterns on electrical resistance. When the size of the delamination damage was moderate compared to the electrode spacing, the electrical resistance increased by less than 1% due to the delamination damage. However, for a specimen with large delamination extending beyond the electrode locations, the oblique resistance increased by 30%. This result suggests that for damage sensing applications, the spacing of electrodes relative to the size of the delamination is important. Finally CT image data was used to model 3-D void distributions and the electrical response of such specimens were compared to models with no voids. As the void content increased, the electrical resistance increased non-linearly. The relationship between void content and electrical resistance was attributed to a combination of three factors: (i) size and shape, (ii) orientation, and (iii) distribution of voids. As a whole, the current thesis provides a comprehensive framework for developing predictive, resistance-based damage sensing models for CFRP laminates of various layup and thickness.
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Nitze, Florian. "Synthesis and characterization of palladium based carbon nanostructure-composites and their clean-energy application." Doctoral thesis, Umeå universitet, Institutionen för fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-68852.
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Carbon nanostructures are a wide field with many applications. The use of carbon nanostructures as support in heterogeneous catalysis is a key development that led together with the use of nanoparticles to a significant cost reduction of catalysts. Catalysts designed in this way are widely applied in fuel cell technologies. For portable devices especially low temperature fuel cells are desirable with low hazards for the user. One technology which fulfills these requirements is the direct formic acid fuel cell (DFAFC). DFAFC have many promising characteristics, such as high electromotive force and easy fuel handling. However, they still suffer from too low power output and lifetime for commercialization. This thesis focusses on two main aspects: the synthesis of carbon nanostructures by chemical vapor deposition (CVD) and their application as catalyst support. The materials are investigated by many different techniques ranging from transmission electron microscopy (TEM) to fuel cell tests. Different carbon nanostructures could be synthesized by catalytic CVD on palladium (Pd) nanoparticles. Multi-walled carbon nanotubes (MWCNTs), carbon nanofibers (CNFs) and helical carbon nanofibers (HCNFs) were grown, selectively, dependent on temperature, using acetylene as carbon precursor. Especially HCNF raised further interest due to their unique structure. A growth model for HCNFs was developed based on an anisotropic extrusion model. The synthesis conditions for HCNFs were optimized until an almost 100 % purity with very high efficiency was obtained. The unique helical but fiber-like structure made the material very interesting as support for heterogeneous catalysis. Several catalysts based on Pd nanoparticle decorated HCNFs were developed. The synthesis methods ranged from standard methods like the polyol method to phase-transfer methods. The catalysts showed very promising results for the electro-oxidation of methanol, ethanol and formic acid. This makes them highly attractive for fuel cell applications. The catalysts were tested in DFAFC. The superiority of HCNF-based catalysts is attributed to the good attachment of nanoparticles to the defect-rich and easy to functionalize surface of HCNFs in combination with adequate film forming properties during electrode preparation.<br>Nanostrukturerat kol är ett mycket brett fält med ett stort antal tillämpningar. Användning av kolnanostrukturer som support för heterogena katalysmaterial har tillsammans med utvecklingen av nanopartiklar lett till en avsevärd minskning av kostnaden för katalysatorer. Katalysatorer designade på detta sätt används frekvent i bränsleceller. För portabla tillämpningar är utvecklingen av säkra och miljövänliga lågtemperaturceller mycket viktig. En teknologi som uppfyller dessa kriterier är bränsleceller som drivs med myrsyra (DFAFC). Sådana bränsleceller har många önskvärda egenskaper, såsom en hög elektromotorisk kraft och en enkel hantering av bränslet. Trots dessa goda egenskaper har de också en del nackdelar som hindrar en full kommersialisering. De två mest problematiska är en för låg genererad effekt samt en för kort livslängd på katalysatorerna. Denna avhandling fokuserar på två huvudpunkter som adresserar dessa problem; tillverkning och karaktärisering av kolnanostrukturer producerade med CVD, och deras tillämpningar som support för katalysatorer. Materialen karaktäriseras med en rad olika tekniker, allt från transmission-elektronmikroskopi till bränslecellstester. Olika kolnanostrukturer har syntetiserats med katalytisk CVD på palladium (Pd) nanopartiklar. Produktionen av flerväggiga kolnanorör, kolfibrer och heliska kolnanofibrer har tillverkats med acetylen som kolkälla och genom att variera temperaturen kunde innehållet av olika typer av nanostrukturerat kol kontrolleras. Särskilt stort intresse har de heliska kolnanofibrerna rönt på grund av deras unika struktur. Vi beskriver en tillväxtmekanism baserad på en anisotrop diffusionsmodell. Genom att justera produktionsparametrarna visar vi att heliska kolnanofibrer kunde tillverkas med nära 100 %-ig renhet och hög effektivitet. Den unika heliska och fiberlika strukturen är mycket intressant for tillämpningar som support för heterogena katalysatorer. Ett flertal kompositer för katalytiska tillämpningar har utvecklats baserade på heliska kolnanofibrer, dekorerade med heterogena katalysatorer genom en rad olika kemiska/fysikaliska tekniker. De syntetiserade materialen visar mycket goda katalytiska egenskaper för att oxidera metanol, etanol och myrsyra. Därigenom blir de mycket attraktiva för användning i bränsleceller. Vi korrelerar de goda katalytiska egenskaperna med en bra vidhäftning av nanopartiklarna på de heliska kolnanofibrerna defekter, deras goda ledningsförmåga, bra egenskaper för att förbereda elektroder, samt deras stora yta i förhållande till deras volym och vikt.
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Kim, Il Tae. "Carbon-based magnetic nanohybrid materials for polymer composites and electrochemical energy storage and conversion." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45876.
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The role of nanohybrid materials in the fields of polymer composites and electrochemical energy systems is significant since they affect the enhanced physical properties and improved electrochemical performance, respectively. As basic nanomaterials, carbon nanotubes and graphene were utilized due to their outstanding physical properties. With these materials, hybrid nanostructures were generated through a novel synthesis method, modified sol-gel process; namely, carbon nanotubes (CNTs)-maghemite and reduced graphene oxide (rGO)-maghemite nanohybrid materials were developed. In the study on polymer composities, developed CNTs-maghemite (magnetic carbon nanotbues (m-CNTs)) were readily aligned under an externally applied magnetic field, and due to the aligned features of m-CNTs in polymer matrices, it showed much enhanced anisotropic electrical and mechanical properties. In the study on electrochemical energy system (Li-ion batteries), rGO-maghemite were used as anode materials; as a result, they showed improved electrochemical performance for Li-ion batteries due to their specific morphology and characteristics.
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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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Bolimowski, Patryk Adam. "Microcapsule-based self-healing in carbon fibre reinforced polymer composites : towards design and application." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.705473.
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Musrizal, Muin. "Alternative approach to the preservative treatment of wood-based composites using supercritical carbon dioxide." Kyoto University, 2003. http://hdl.handle.net/2433/148986.
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Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(農学)<br>甲第10260号<br>農博第1332号<br>新制||農||867(附属図書館)<br>学位論文||H15||N3781(農学部図書室)<br>UT51-2003-H681<br>京都大学大学院農学研究科森林科学専攻<br>(主査)教授 今村 祐嗣, 教授 川井 秀一, 助教授 角田 邦夫<br>学位規則第4条第1項該当
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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<br>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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Kannan, R. "Functionalized carbon nanotube based polymer composites as electrolytes in proton exchange membrane fuel cells." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2010. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/3752.
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Wang, Sanwu 1971. "Carbonation of cement-based products with pure carbon dioxide and flue gas." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100734.
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CO2 absorption behaviour of four commonly used cement based building products: cement paste, concrete block, expanded polystyrene bead (EPB) and cement-bonded cellulose fiberboard are studied. Cement products are manufactured following industry formulation and process, and carbonation curing takes place in a chamber under a pressure of 0.5 MPa, at ambient temperature, for durations of mostly 2 to 8 hours with both pure carbon dioxide gas and flue gas. The flue gas of 13.8% CO2 content is collected from a typical cement kiln without separation. Influencing factors on carbon uptake, long-term strength as well as microstructure development are studied.<br>It is found that the CO2 uptake ability of those cement-based products follows the same order when exposed to either pure gas or flue gas: fiberboard has the highest uptake capacity, followed by cement paste, bead board and concrete. For fiberboard, the best CO2 uptake in flue gas is 8.1%, it reaches 23.6% if pure gas used. Introduction of cellulose fiber in the fiberboard significantly increases voids volume and cement paste surface area through dispersing the paste onto fiber surface, effectively increasing carbonation reaction sites and thus CO2 uptake.<br>For pure gas carbonation with high reaction rate, it takes longer time for carbonated products to further develop strength from subsequent hydration, due to the high water loss during carbonation, the densified cement matrix structures and even fast decalcified cement minerals. Fast carbonation with pure gas is detrimental to cement paste in its long-term strength. For flue gas carbonation, both immediate strengths and long-term strength of the products are comparable with those by pure gas carbonation, although with less CO 2 uptake ability.<br>Five CO2 uptake determination methods are evaluated. Weight gain method is suitable for both pure gas and flue gas carbonation systems. Mass curve method is more suited for pure gas carbonation. For flue gas carbonation, CO2 concentration method agreed well with the weight gain method. Pressure drop method is relatively less accurate because of water vapor generation during carbonation.
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Nelson, Anthony Joseph. "Effects of Proton Irradiation on the Mechanical and Physical Properties of Carbon Nanotube Based Composites." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/25153.
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In this study, the effects of proton irradiation on carbon nanotube (CNT)-epoxy composites are investigated for potential applications in radiation shielding for spacecraft. CNT-epoxy composites were prepared using multiwall and single wall CNTs and exposed to proton beams of energies ranging from 6 MeV to 12 MeV. The nanocomposites shielding capabilities against the different energetic proton beams were measured by tracking the beam's energy before and after penetrating the samples. The microstructures of the samples were characterized using scanning electron microscopy (FESEM). The effect of proton irradiation on the electrical resistivity was measured using a high resolution multimeter. Finally the influence of the irradiation on the mechanical properties, such as the elastic modulus and hardness, was probed using instrumented nanoindentation tests.
The proton stopping power of the epoxy was shown to be unchanged by the addition of CNTs, which is a promising result since the hardness of the samples was shown to be increased by addition of CNTs. Unfortunately, however, the surface of the samples proved to be too rough for nanoindentation to yield more detailed results. This was due to the use of a diamond saw in cutting the samples to size. The addition of CNTs was shown to reduce the volume electrical resistivity of the neat epoxy by almost five orders of magnitude and the irradiation further reduced it by a factor of 2-16.<br>Master of Science
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GADE, SRINIVAS. "CHARACTERIZATION OF THE MECHANICAL PROPERTIES OF CARBON NANOTUBE-BASED COMPOSITES USING THE FINITE ELEMENT METHOD." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1131990503.
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Morgan, James Randall. "The influence of orientation on the stabilization and carbonization of acrylic precursors and the influence of phosphorous-containing comonomers on the electrical conductance of acrylic-based carbon fibers." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/8631.
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Vicentini, Nicola. "Screening on the functionalization of carbon nanostructures and their compatibilization in polymer-based composite materials." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3424578.
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Composites of carbon nanostructures (CNSs) and biocompatible polymers are promising materials for a series of advanced technological applications, ranging from biomedicine and bioelectronics to smart packaging and soft robotics. In this thesis, we present three types of organic functionalized CNSs, namely 4-methoxyphenyl functionalized multi-walled carbon nanotubes, carbon nanohorns and reduced graphene oxide, used as nanofillers for the preparation of homogeneous and well-dispersed composites of poly(l-lactic acid), a biocompatible and biodegradable FDA approved polymer. A thorough characterization of the composites is given in terms of calorimetric response, electrical and mechanical properties. Significant differences are observed among the different types of CNS nanofillers, underlying the key role played by the nanoscale shape, and distribution of the components in driving the macroscopic behavior of the composite material. Surface properties are probed through advanced atomic force microscopy techniques, on both flat substrates (films) and confined systems (nanofibers). All these composites are found to be fully biocompatible when tested as scaffolds for supporting the proliferation, and differentiations of human neuronal precursor cell line SH-SY5Y, and of human Circulating Multipotent stem Cells (hCMCs). Prototypes of Nerve Guide Conduits (NGCs) for in vivo tests were also designed, and obtained using the material based on functionalized Multi Walled Carbon Nanotubes (MWCNTs), and tested on mice, finding promising results. We also propose the functionalization of MWCNTs with “functional” organic groups (4-benzoic acids and styrene), and performed an additional derivatization on them respectively through an amidation reaction, and a “grafting from” polymerization. The so obtained CNSs are promising for the preparation of more complex composite materials. Finally, we analyzed the reaction pathway of the Tour functionalization of CNSs, and we hypothesized that the real reaction scheme could be a balance between two different pathways.<br>Le nanostrutture di carbonio (CNS) e i polimeri biocompatibili sono materiali molto promettenti in un grande numero di applicazioni tecnologicamente avanzate, che vanno dalla biomedicina e bioelettronica, allo smart packaging e alla robotica soft. In questa tesi presentiamo la funzionalizzazione organica tramite addizione della p-metossianilina di 3 diverse CNS: i nanotubi di carbonio a parete multipla, i nanoconi di carbonio e il grafene ossido risotto. Questi materiali sono impiegati come additivi per la preparazione di materiali compositi nanostrutturati a base di acido polilattico (PLLA). In questa tesi è riportata una completa caratterizzazione in termini di proprietà termiche, elettriche e meccaniche. Sono evidenti differenze significative tra le tre nanostrutture e sul loro effetto sulle proprietà dei compositi; ciò sottolinea il ruolo chiave giocato dalla morfologia e forma a livello nanometrico nell’interazione nanostruttura-polimero e quindi nella determinazione delle caratteristiche finali del composito. La superfice dei materiali è stata caratterizzata tramite AFM e CAFM sia nella forma di film piatti sia nella forma di nanofibre ottenute tramite eletrospinning. Sono state quindi testate le proprietà di biocompatibilità e induzione/controllo della differenziazione sia su cellule umane neuronali (SH-SY5Y), sia su cellule staminali umane (hCMCs). I materiali a base di nanotubi di carbonio a parete multipla (MWCNT) ottenuti sono stati utilizzati per la preparazione di prototipi di nerve guide conduits (NGC) per operazioni in-vivo su topi, ottenendo risultati molto promettenti. Presentiamo anche la funzionalizzazione dei MWCNT con 2 gruppi organici “funzionali” (l’acido p-benzoico e lo stirene) sui quali è stata effettuata una derivatizzazione aggiuntiva sfruttando rispettivamente una reazione di ammidazione e una reazione di polimerizzazione “grafting from”. Infine abbiamo analizzato lo schema di reazione della funzionalizzazione di Tour delle CNS a abbiamo ipotizzato che la reale via sintetica sia costituita da due differenti vie in equilibrio tra di loro.
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Woelfle, Caroline. "Study of Nanoparticle/Polymer Composites: I) Microstructures and Nonlinear Optical Solutions Based on Single-Walled Carbon Nanotubes and Polymers and II) Optical Properties of Quantum Dot/Polymer Composites." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/26657.
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The overall research theme of this dissertation was the study of nanoparticle/polymer composites. Two types of nanoparticles were utilized: Single-Walled Carbon Nanotubes and quantum dots. Chapter 1 of this thesis comprises an extensive literature review on Carbon Nanotubes, which presents theoretical aspects relevant to the structure and properties of CNTs, methods of purifying and solubilizing CNTs in aqueous and organic solvents and selected applications. This literature review is followed by the study and comparison of the optical limiting performances of different Single-Walled Carbon Nanotubes/conjugated polymer dispersions (Chapter 2). The results obtained are discussed in terms of dispersion of the SWNTs in the polymer solutions and resulting SWNT bundle diameters. Chapter 3 presents the spontaneous assembly of dendrimer patterns induced by SWNTs. Finally, chapter 4 presents a new method for fabricating quantum dot/polymer composites, which uses the extraction of positively charged quantum dot into a hydrophobic liquid. The resulting solution is used as a compatible polymerization medium for poly(methylmethacrylate ) networks enabling the formation of transparent and fluorescent composites.<br>Ph. D.
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Fechler, Nina. "Salts as highly diverse porogens : functional ionic liquid-derived carbons and carbon-based composites for energy-related applications." Phd thesis, Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2013/6477/.
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The present thesis is to be brought into line with the current need for alternative and sustainable approaches toward energy management and materials design. In this context, carbon in particular has become the material of choice in many fields such as energy conversion and storage.
Herein, three main topics are covered:
1)An alternative synthesis strategy toward highly porous functional carbons with tunable porosity using ordinary salts as porogen (denoted as “salt templating”)
2)The one-pot synthesis of porous metal nitride containing functional carbon composites
3)The combination of both approaches, enabling the generation of highly porous composites with finely tunable properties
All approaches have in common that they are based on the utilization of ionic liquids, salts which are liquid below 100 °C, as precursors.
Just recently, ionic liquids were shown to be versatile precursors for the generation of heteroatom-doped carbons since the liquid state and a negligible vapor pressure are highly advantageous properties. However, in most cases the products do not possess any porosity which is essential for many applications. In the first part, “salt templating”, the utilization of salts as diverse and sustainable porogens, is introduced. Exemplarily shown for ionic liquid derived nitrogen- and nitrogen-boron-co-doped carbons, the control of the porosity and morphology on the nanometer scale by salt templating is presented. The studies within this thesis were conducted with the ionic liquids 1-Butyl-3-methyl-pyridinium dicyanamide (Bmp-dca), 1-Ethyl-3-methyl-imidazolium dicyanamide (Emim-dca) and 1 Ethyl 3-methyl-imidazolium tetracyanoborate (Emim-tcb). The materials are generated through thermal treatment of precursor mixtures containing one of the ionic liquids and a porogen salt. By simple removal of the non-carbonizable template salt with water, functional graphitic carbons with pore sizes ranging from micro- to mesoporous and surface areas up to 2000 m2g-1 are obtained. The carbon morphologies, which presumably originate from different onsets of demixing, mainly depend on the nature of the porogen salt whereas the nature of the ionic liquid plays a minor role. Thus, a structural effect of the porogen salt rather than activation can be assumed. This offers an alternative to conventional activation and templating methods, enabling to avoid multiple-step and energy-consuming synthesis pathways as well as employment of hazardous chemicals for the template removal.
The composition of the carbons can be altered via the heat-treatment procedure, thus at lower synthesis temperatures rather polymeric carbonaceous materials with a high degree of functional groups and high surface areas are accessible. First results suggest the suitability of the materials for CO2 utilization.
In order to further illustrate the potential of ionic liquids as carbon precursors and to expand the class of carbons which can be obtained, the ionic liquid 1-Ethyl-3-methyl-imidazolium thiocyanate (Emim-scn) is introduced for the generation of nitrogen-sulfur-co-doped carbons in combination with the already studied ionic liquids Bmp-dca and Emim-dca. Here, the salt templating approach should also be applicable eventually further illustrating the potential of salt templating, too.
In the second part, a one-pot and template-free synthesis approach toward inherently porous metal nitride nanoparticle containing nitrogen-doped carbon composites is presented. Since ionic liquids also offer outstanding solubility properties, the materials can be generated through the carbonization of homogeneous solutions of an ionic liquid acting as nitrogen as well as carbon source and the respective metal precursor. The metal content and surface area are easily tunable via the initial metal precursor amount. Furthermore, it is also possible to synthesize composites with ternary nitride nanoparticles whose composition is adjustable by the metal ratio in the precursor solution.
Finally, both approaches are combined into salt templating of the one-pot composites. This opens the way to the one-step synthesis of composites with tunable composition, particle size as well as precisely controllable porosity and morphology. Thereby, common synthesis strategies where the product composition is often negatively affected by the template removal procedure can be avoided. The composites are further shown to be suitable as electrodes for supercapacitors. Here, different properties such as porosity, metal content and particle size are investigated and discussed with respect to their influence on the energy storage performance.
Because a variety of ionic liquids, metal precursors and salts can be combined and a simple closed-loop process including salt recycling is imaginable, the approaches present a promising platform toward sustainable materials design.<br>Die vorliegende Arbeit basiert auf der Notwendigkeit für eine alternative und nachhaltige Energiewirtschaft sowie alternativer Herstellungsmethoden der damit verbundenen Materialien.
Hierbei kommt besonders Kohlenstoffen und kohlenstoffbasierten Systemen eine hohe Bedeutung zu. Im Rahmen der Dissertation wurden drei Ansätze verfolgt, die zu der Entwicklung alternativer Strategien zur Herstellung poröser Heteroatom-enthaltender Kohlenstoffe und deren Komposite beitragen. Die Materialien wurden des Weiteren für die CO2 Nutzung sowie Energiespeicherung in Form von Superkondensatoren getestet. Allen Materialien ist gemeinsam, dass sie ausgehend von ionischen Flüssigkeiten, Salze mit einem Schmelzpunkt unterhalb von 100 °C, als Kohlenstoffvorstufe durch Hochtemperaturverfahren hergestellt wurden.
Im ersten Teil wird ein alternatives und nachhaltiges Verfahren zur Herstellung hochporöser Stickstoff und Stickstoff-Bor-haltiger Kohlenstoffe vorgestellt. Bei dieser als „Salztemplatierung“ bezeichneten Methode werden herkömmliche Salze als Porogen verwendet. Damit sind sehr hohe Oberflächen erreichbar, die neben der Porengröße und dem Porenvolumen durch die Variation der Salzspezies und Salzmenge einstellbar sind. Dies bietet gegenüber herkömmlichen Templatierungsverfahren den Vorteil, dass das Salz nach erfolgter Karbonisierung der ionischen Flüssigkeit in Anwesenheit der nicht karbonisierbaren Salzspezies einfach mit Wasser auswaschbar ist. Hierbei ist ein Recyclingprozess denkbar. Bei hohen Synthesetemperaturen werden graphitische, bei niedrigen hochfunktionalisierte, polymerartige Produkte erhalten. Letztere erwiesen sich als vielversprechende Materialien für die CO2 Nutzung. Unter Verwendung einer bisher nicht eingesetzten ionische Flüssigkeit konnte weiterhin die Einführung von Schwefel als Heteroatom ermöglicht werden.
Im zweiten Teil wird eine Templat-freie Einschrittsynthese von porösen Kompositen aus Metallnitrid Nanopartikeln und Stickstoff-dotiertem Kohlenstoff vorgestellt. Die Materialien werden ausgehend von einer Lösung aus einer ionischen Flüssigkeit und einem Metallvorläufer hergestellt, wobei die ionische Flüssigkeit sowohl als Kohlenstoffvorläufer als auch als Stickstoffquelle für die Metallnitride dient. Der Metallgehalt, das Metallverhältnis in ternären Nitriden und die Oberfläche sind über den Anteil des Metallvorläufers einstellbar.
Schließlich werden beide Ansätze zur Salztemplatierung von den Kompositen kombiniert. Dadurch wird die Einschrittsynthese von Kompositen mit einstellbarer Oberfläche, Zusammensetzung, Partikelgröße und Morphologie ermöglicht. Diese Materialien wurden schließlich als Elektroden für Superkondensatoren getestet und der Einfluss verschiedener Parameter auf die Leistungsfähigkeit untersucht.
Aufgrund verschiedener Kombinationsmöglichkeiten von ionischen Flüssigkeiten, Metallvorläufern und Salzen, stellen die hier präsentierten Ansätze eine vielversprechende Plattform für die nachhaltige Materialsynthese dar.
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Xenopoulos, Constantinos. "Polyimide-silica hybrids based on polyamic acid and an acetylene-terminated isoimide as matrices for carbon fibre composites." Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/25276.
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A study was carried out on formulations of organic-inorganic hybrids and their subsequent use as matrices for unidirectional carbon fibre-reinforced composites. The hybrids consist of low molecular weight polyimide precursors and silica which is generated in-situ via the sol-gel route. A special feature of these systems is the use of organofunctional trialkoxysilanes as coupling agents for the two phases and for controlling the resultant morphology. Enhancements are obtained in physicochemical, thermal and mechanical properties of hybrids through morphological modifications achieved in the parent polyimide and silicate materials. Small variations to the composition of the precursors display a substantial effect both on the kinetics of the associated reactions and the final properties of hybrids, often as a result of a change in miscibility of the organic and the inorganic components of the system. The processability of the matrix was evaluated with respect to the fabrication of composites, which in this case is strongly influenced by the gelation behaviour of both the organic pre-polymer and also the inorganic sol-gel component. The kinetics of gelation reactions were examined by dynamic viscometry and by practical tests based on visual observation of the cessation of flow. Differential scanning calorimetry, infrared spectroscopy, thermogravimetric analysis and electron microscopy formed part of the evaluation of the matrix materials. Composites were produced by application of the matrix solution from a variety of formulations on pre-tensioned fibres, followed by vacuum drying and curing under pressure at high temperatures. The properties of these composites were determined by such methods as dynamic mechanical thermal analysis, flexural testing and thermomechanical analysis. From the results obtained in this study, it is concluded that the inclusion of silicate phase in a polyimide matrix in the form of fine co-continuous networks improves the thermal and mechanical properties of the base material, although these are dependent on the overall silicate content and the amount of the coupling agent. High loadings of the coupling agent can cause degradation by chain scission and a reduction of the crosslinking density of the organic pre-polymer.
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Babaev, A. A., P. P. Khokhlachev, Yu A. Nikolaev, et al. "Temperature Dependence of Resistivity and Current-Voltage Characteristics of the Films of Composites Based on Modified Carbon Multiwalled Nanotubes and Graphite." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35160.
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A film composites based on modified multiwalled carbon tubes and polymer (95/5 wt. %) Respectively on paper, without the paper by directional spinning from the liquid phase and graphite. The temperature dependence of the resistivity () in the range T 77-410 K and the corresponding current-voltage charac-teristics. Detected irreversible transitions from semiconducting to metallic conductivity in carbon nono-trubkah and a maximum at T 340 K.
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