Tesi sul tema "Composite materials C/C"
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Goettler, Christoph Michael. "EFFECT OF DENSITY ON FRICTION AND WEAR PERFORMANCE OF CARBON-CARBON COMPOSITE MATERIALS". OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2780.
Ozcan, Soydan. "Microstructure-property-performance relationships of c-fiber-reinforced carbon composite friction materials /". Available to subscribers only, 2008. http://proquest.umi.com/pqdweb?did=1686179081&sid=4&Fmt=2&clientId=1509&RQT=309&VName=PQD.
"Department of Engineering Science." Keywords: Carbon composite, Friction materials, Carbon-fiber reinforcement Includes bibliographical references (p. 106-115). Also available online.
Voirin, Thibaut. "Etude du comportement mécanique et de l’endommagement des composites C/C à basses et hautes températures". Thesis, Lyon, 2021. http://www.theses.fr/2021LYSEI008.
Carbon/Carbon composites are used in aeronautics and space industries for their excellent thermomechanical properties, from room temperature to very high temperatures (up to 3000°C). Nevertheless, these properties and their evolution at elevated temperatures are not known well enough, specifically for braking-like solicitations such as plane braking or motorsport braking.The main objectives of this work was to study the mechanical behavior of this composite under mechanical solicitations that may occur during a braking situation. Thereby, compressive and shear behavior were studied in particular, in order to determine the evolution of the damage mechanisms depending on the temperature for these loading modes. In order to lead this study successfully, various experimental aspects have been approached, such as sample geometry, as well as measurements issues due to the mechanical testing at high temperatures. This is how original mechanical testing of the interlaminar shear behavior have been performed. Concurrently with these tests, the material microstructure has been studied in-situ and post-mortem with a multi-scale approach (at ply level, at yarn level and at fiber level inside the strands). The evolution of the mechanical properties has been linked to the microstructure evolution for the different loading modes (Z-compression, XY-compression and interlaminar shear) in order to propose damage scenario of the material as a function of the temperature. This approach allowed us to understand the major role of the thermal differential dilatations of the yarn on the shrinking of the needles for temperatures up to 1500°C. For temperatures higher than 1500°C, plasticity effects have been identified
Tariq, Amna. "Design and implementation of a plasma enhanced chemical vapour deposition (PECVD) system for the study of C₆₀-polymer composite thin films and surface fuctionalization effects on C₆₀". Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81572.
Sen, Gupta Jayant. "Mésodynamique et rupture des composites 3D C/C sous choc : une stratégie numérique dédiée". Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2005. http://tel.archives-ouvertes.fr/tel-00133772.
Kouri, Jeffrey Victor. "Improved finite element analysis of thick laminated composite plates by the predictor corrector technique and approximation of C[superscript]1 continuity with a new least squares element". Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/20762.
Iqbal, Sardar S. "IMPACT OF HEAT TREATMENT AND OXIDATION OF C/C COMPOSITES ON MICROSTRUCTURE AND PHYSICAL PROPERTIES". OpenSIUC, 2011. https://opensiuc.lib.siu.edu/dissertations/430.
DUTRA, RITA M. "Estudo da oxidação eletroquímica do etanol em meio acido utilizando os eletrocatalisadores PtSnAuRh/C e PtRuAuRh/C". reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/27126.
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Os eletrocatalisadores quartenários PtSnAuRh/C e PtRuAuRh/C foram preparados nas proporções 50:40:5:5, 60:30:5:5, 70:20:5:5, 80:10:5:5, 90:4:3:3 e para as composições terciárias PtSnAu/C, PtSnRh/C, PtRuAu/C, PtRuRh/C preparados na proporção atômica 50:45:5 com (20% em massa) pelo método da redução por álcool utilizando H2PtCl6.6H2O, RuCl3·xH2O, SnCl2.2H2O, HAuCl4.3H2O e RhCl3.xH2O, como fonte de metais e carbono Vulcan XC72 como suporte e, por último, etileno glicol como agente redutor. Os eletrocatalisadores obtidos foram caracterizados fisicamente por difração de raios-X (DRX), energia dispersiva de raios X (EDX) e microscopia eletrônica de transmissão (MET). As análises por EDX mostraram que as razões atômicas dos diferentes eletrocatalisadores, preparados pelo método da redução por álcool, foram similares às composições nominais de partida indicando que esta metodologia é eficiente para a preparação destes eletrocatalisadores. Em todos os difratogramas para os eletrocatalisadores preparados observa-se um pico largo em aproximadamente 2θ = 25°, o qual é associado ao suporte de carbono e quatro outros picos de difração em aproximadamente 2θ = 40°, 47°, 67° e 82°, que por sua vez são associados aos planos (111), (200), (220) e (311), respectivamente, da estrutura cúbica de face centrada (CFC) de platina. Os resultados de difração de raios X apresentaram tamanhos médios de cristalitos entre 2,0 e 5,2 nm para PtSnAuRh/C, PtSnAu/C, PtSnRh/C e 2,0 a 2,6 nm para PtRuAuRh/C, PtRuAu/C, PtRuRh/C. Os estudos para a oxidação eletroquímica do etanol em meio ácido foram realizados utilizando as técnicas de voltametria cíclica e de cronoamperometria em uma solução 0,5 mol.L-1 H2SO4, + 1,0 mol.L-1 de C2H5OH. As curvas de polarização obtidas na célula a combustível unitária, alimentada diretamente por etanol, estão de acordo com os resultados de voltametria e cronoamperometria constatando o efeito benéfico da adição do ouro e ródio na composição dos eletrocatalisadores.
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
Mtawa, Alexander Nikwanduka. "Influence of geometry and material properties on the optimum performance of the C-shape piezo-composite actuator". Thesis, Cape Peninsula University of Technology, 2008. http://hdl.handle.net/20.500.11838/1301.
In recent years, due to rapid advances in technology there has been an increasingly high demand for large displacement and large force, precise positioning, fast response, low power consuming miniature piezoelectric actuators. In certain smart structure applications, the use of curved piezoelectric actuators is necessary. The present work extends the earlier investigations on the C- shape actuator by providing a detailed investigation on the influence of geometric and material properties of the individual layers of the C-shape piezocomposite for its optimal performance as an actuator. Analytical models have. been used to optimize the geometry of the actuator. Experimental and finite element analyses (using general purpose finite element software i.e. CoventerWare and MSC. Marc) have been used for validation. The present work has established that, by maintaining the thickness of the substrate and piezoceramic layers constant; changing the external radius, for example increasing it, the stiffness of the structure decreases and thus yielding large displacement This has a negative effect on the force produced by the actuator. With fixed thickness of the substrate and varying the thickness of the piezoceramic (for fixed external radius) the result is as follows: Increasing the thickness of the piezoceramic layer has the effect of decreasing the displacement while the force increases. With fixed PZT thickness as well as the external radius, varying the substrate thickness has the following effect: As the thickness of the substrate increases the displacement increases reaching a maximum. Subsequent increase in the thickness of the substrate the displacement is reduced. The force continues increasing at least for the ratios up to 1.0, further increase of the substrate, subsequent decrease of force is also noted. In addition to changing the thickness of the substrate, the choice of different material for the substrate has the following effect: For substrate/PZT ratios of up to 0.6. an actuator with substrate material having higher elastic modulus will produce larger displacement while for ratios beyond this ratio the situation is reversed. The causes for this kind of behaviour have been addressed. In all cases both force and displacement are found to be directly proportional to applied voltage.
Chelaghma, Saber Ayoub. "Fonctionnalisation de composites C/PEKK pour application aérospatiale : caractérisation, modélisation et influence sur les propriétés du composite". Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30362.
Reducing aircraft weight is one of the major challenges facing the aerospace industry. In order to achieve the ambitious goals of fuel consumption and emission reduction, carbon-fiber reinforced composites have been introduced to the market. These materials are attracting increasing interest, however, they have low electrical conductivity to ensure protection against lightning strike. For this reason, composites filled with conductive particles are the subject of ongoing research activities. The objective is the development of multifunctional composites with enhanced electrical properties. Actually, the most used thermoplastic matrix is PEEK, but this polymer remains expensive, and its processing temperature is high. For this purpose, thermoplastic matrices, such as PEKK, are again studied. Between the raw material and the final part, the thermoplastic matrix undergoes several thermal steps with high temperature exposure (impregnation, consolidation, forming and assembly processes) during which its ability to crystallize evolves continuously. In order to evaluate the impact of the process and the composite constituents on its properties, crystallization has been the subject of particular attention. Two complementary experimental devices were used to characterize the crystallization. The heating stage, allows to apply a thermal cycle and observe the crystallization in optical microscopy and differential scanning calorimetry. The influence of carbon fibers and conductive fillers on the crystallization kinetics was evaluated. A decrease in crystallization times was observed through the increase of the nucleation rate. The collected data were used to develop a kinetic model identified through an original approach based on microscopic data. This model makes it possible to predict the crystallization kinetics of PEKK composites. Nevertheless, it does not make it possible to predict the final microstructure. However, the microstructure has a significant impact on mechanical properties as it has been proven through nano-indentation tests. To predict the final microstructure, a model based on the pixel coloring approach has been developed. The influence of carbon fibers has been introduced through the formation of a transcrystalline phase. A good correlation is found between the analytical approach, the simulation and the experimental data in terms of crystallization kinetics. Mechanical and electrical characterizations were performed to evaluate the performance of these new materials. On the studied materials, the mechanical response is not homogeneous as observed on tensile tests followed in stereo-correlation. The study of matter health shows the existence of defects, in particular, at the microstructure level. In order to take this particularity into account, it is thus necessary to describe the microstructure more finely. For this, X-ray tomography was used to characterize the composite. Recent developments in this technique allow, in combination with segmentation tools, to reconstruct a representative geometry of the material. This geometry is used to simulate the mechanical behaviour as well as the crystallization. The numerical simulations of an RVE are able to calculate the properties of a ply, then those of a laminate. This multi-scale modelling could reduce the number and cost of experimental campaigns. Thus, determining the properties of the final structure based on characterizations and simulation at the microstructure scale is a strategic scientific and industrial issue. This work is a contribution towards this approach
Shaw, John Henry. "Effects of Fiber Architecture on Damage and Failure in C/SiC Composites". Thesis, University of California, Santa Barbara, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3682976.
Carbon-fiber/SiC-matrix composites are under development for applications in hypersonic vehicles due to their exceptional capabilities at high temperatures. As a subset of these materials, textile-based composites are of particular interest because they offer the possibility of accommodating complex geometries and features in engineering components. Among the numerous obstacles hindering the widespread adoption of these composites, two are addressed in the present work: (i) the incomplete understanding of the influence of textile architecture on thermoelastic properties, damage initiation and failure, and (ii) the lack of robust computational tools for predicting their thermomechanical performance at the appropriate length scales. Accordingly, an experimental study is performed of the thermal and mechanical properties of several prototypical textile C/SiC composites with various fiber architectures. In turn, the experimental results are used to guide the development of computational tools for predicting composite response that explicitly account for fiber architecture.
Textile architecture is found to influence composite response at four length-scales: the panel, the coupon, the tow, and the sub-tow. At the panel scale, distortions to the architecture introduced during weaving or handling of the fabric influence the packing density and the relative rotation of tows. Even when large distortions are intentionally introduced their influence on mechanical response is minimal. At the coupon scale the tow architecture has the largest effects on composite mechanical response. Young's modulus, ultimate tensile strength, and strain to failure are all influenced. Changes in each of these are a function of tow shape, tow anisotropy, and the degree of constraint provided by the matrix. At the tow scale, architecture effects give rise to heterogeneity in measured surface strains under both tensile and thermal loading. Methods for the calibration of tow-scale elastic and thermoelastic properties were developed to enable simulation of these effects with a geometrically-accurate virtual model. Virtual tensile and thermal tests using this model have indicated that interaction between tows has an important influence on local strains. At the sub-tow scale, architecture effects influence the location of matrix cracking. Simulations of the cooling cycle following matrix processing predict that matrix cracks should develop in the matrix above underlying tows due to thermal expansion mismatch between the tows and the matrix. This is consistent with experimental observations. Two methods are presented to extend the virtual tests to explicitly simulate the onset and evolution of these cracks.
Zhang, Hai. "Comparative study of infrared thermography, ultrasonic C-scan, X-ray computed tomography and terahertz imaging on composite materials". Doctoral thesis, Université Laval, 2017. http://hdl.handle.net/20.500.11794/36573.
Non-destructive testing (NDT) of composite materials is complicated due to the wide range off laws encountered (including delamination, micro-cracking, fiber fracture, fiber pullout, matrix cracking, inclusions, voids, and impact damage). The ability to quantitatively characterize the type, geometry, and orientation of flaws is essential. Infrared thermography (IRT), as an image diagnostic technique, can satisfy the increasing industrial need for NDT&E. In the thesis, optical and mechanical excitation thermography were used to investigate different composite materials, including 1) carbon fiber dry preforms, 2) natural fiber composites, 3) basalt-carbon fiber hybrid composites subjected to impact loading (sandwich-like and intercalated stacking sequence), 4) micro-sized flaws in a stitched T-joint 3D carbon fiber reinforced polymer composite (CFRP), and 5) paintings on canvas which can be considered as composite materials. Of particular interest, a new IRT technique micro-laser line thermography (micro-LLT) was proposed for the evaluation of submillimeter porosities in CFRP. Micro-laser spot thermography (micro-LST) and micro-vibrothermography (micro-VT) were also presented with the usage of a micro-lens. Pulsed thermography (PT) and lock-in thermography (LT) were compared with x-ray computed tomography (CT) for validation. Ultrasonic C-scan (UT) and continuous wave terahertz imaging (CW THz) were also conducted for the comparative purpose. The inspection by thermographic techniques is an open matter to be discussed for the scientific audience. In fact, pulse phase thermography (PPT) based on phase transform was used to estimate the damage depth. Basic thermographic signal reconstruction (B-TSR), principal component thermography (PCT) and partial least squares thermography (PLST) (another more recent advanced image processing technique) were also used to pro-cess the thermographic data. Finally, a comprehensive and comparative analysis based on thermographic image diagnostics was conducted in view of potential industrial applications.
Champagne, Matthieu. "« Endommagement utile » et « dialogue surface/volume » : Investigations numérique et expérimentale du comportement des composites C/C sous sollicitations tribologiques". Thesis, Lyon, INSA, 2014. http://www.theses.fr/2013ISAL0135.
Carbon/Carbon (or C/C) composite is used as a friction material in aeronautical braking applications. This is a complex material from both microstructural and tribological behavior points of view. Thus, it has been studied through various works for several years, aiming at understanding what mechanisms guide this material response (friction, damage, wear) under tribological conditions. In this study, a focus is performed on mechanical aspects such as damages that occur in the numerical and experimental approach, in view to identify and classify the damages as well as to build a numerical model used to investigate wear mechanisms. It is underlined how first-body accommodation mechanisms have a great influence on particles detachment at the interface, as a surface/volume tribological dialogue take place. This model is based on the Discrete Elements method and represents simultaneously first- and third-body; such model is able to represent fist-body degradation as well as creation and flow of third-body particles. Its representativeness is ensured through experimental comparisons, particularly on mechanical aspects. A procedure is proposed for the research of a Representative Elementary Volume under contact conditions. Model results and material observations allow proposing a global scenario explaining C/C composite behavior under tribological conditions, which are representative of different aeronautical braking cases. Damages, identified in the volume of the first-body, reveal themselves to be sometimes beneficial, and could be characterized as “useful damages”. The scenario takes into account this phenomenon, as well as thermal, mechanical and physicochemical ones, identified from this work or literature. It explains the influences of these parameters on C/C tribology and show how the dynamic equilibrium between them results on the C/C response, particularly its wear mechanism
Margueritat-Regenet, Caroline. "Elaboration et caractérisation de fils composites C/Al : infiltration spontanée et continue par activation chimique du mouillage". Phd thesis, École Nationale Supérieure des Mines de Paris, 2002. http://tel.archives-ouvertes.fr/tel-00005642.
La mèche de fibre (Torayca T700S-12K) étant commercialisée avec 1% en masse densimage, une première étape a consisté en l'élimination de cette couche d'époxy par dégradation thermique sous air. D'une part, il a été construit un diagramme pour le choix des paramètres de désensimage (température du four, vitesse de défilement) minimisant la perte des propriétés mécaniques des fibres. D'autre part, la cinétique du phénomène de désensimage a été établie afin de prévoir le désensimage " dynamique " sur le pilote en connaissant le profil thermique de la mèche pour les conditions opératoires données.
La mèche est ensuite trempée dans une solution aqueuse saturée d'un sel fluoré à 95°C puis séchée sous air, dans la seconde étape, dite de traitement au flux pour laquelle les paramètres opératoires sont la vitesse de défilement et la composition du flux. Il s'est agi ici d'étudier, plus particulièrement, le vieillissement de la solution aqueuse et la qualité du dépôt de cristaux sur la mèche (morphologie, répartition et quantité). D'une manière générale, le coeur de la mèche est beaucoup moins bien traité que sa surface. Laction de plusieurs composés fluorés sur le mouillage des fibres par l'aluminium a été regardé. Un schéma réactionnel s'appuyant essentiellement sur une étude ATD a mis en évidence le rôle favorable de l'oxydation par l'air de l'aluminium natif pour l'imprégnation du coeur du composite. Comparée à la toute première réaction flux/alumine, cest principalement la réaction flux/aluminium liquide qui engendre lélévation suffisante de température permettant dinitier l'infiltration.
Enfin, la mèche passe par un bain d'aluminium liquide (99,7% en masse) à 710°C sous air : c'est l'étape d'infiltration dont les paramètres sont la température du bain et la vitesse de défilement. Dans cette dernière étape, le but était de définir la microstructure et les propriétés du fil composite élaboré selon les conditions optimales. Des observations fines au MET indiquent la présence de précipités Al3Zr et Al4C3 à linterface fibre/matrice. Cette adhésion chimique contribue à limiter la tenue mécanique du fil tout comme la distribution inhomogène des fibres, la présence de porosités naturelles et de cryolithe solidifiée. Le meilleur fil composite a été obtenu pour une vitesse lente (1m/min) et une température moyenne du bain (710°C)°. Sa résistance à la traction ne dépasse pas 520Mpa pour une fraction volumique de fibres de 40%, ce qui suggère de minimiser les dégradations diverses subies par le renfort dans les trois étapes et les défauts liés à l'infiltration réactive.
Thaury, Claire. "Optimisation de matériaux composites Si/Intermétallique/Al/C utilisés comme électrode négative dans des accumulateurs Li-ion". Thesis, Paris Est, 2015. http://www.theses.fr/2015PEST1068/document.
This study focuses on the optimization of innovative composite materials Si/Intermetallic/Al/C used as negative electrode in lithium-ion batteries. The aim of this work is optimization of the composition for the material (20Ni-48Sn-20Si-3Al-9C) to improve its electrochemical performances. All materials are made up of silicon nanoparticles embedded in a sub micrometrical matrix. Several issues have been studied in this essay: optimization of the silicon and carbon contents, influence of the silicon surface composition, and substitution of the former intermetallic Ni3+xSn4 by other ones: zinc aluminium compound Al0,23Zn0,77 and two intermetallics Cu6Sn5 et CoSn. Metallic compounds and composites have been synthesised by powder metallurgy and mechanical alloying, respectively. Their chemical and structural properties have been determined by electron probe microanalysis, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Electrochemical characterisations have been carried out by galvanostatic cycling and cyclic voltammetry in coin and Swagelok half cells. This report details the influence of the studied parameters on the structural properties of the composite materials. A large study was devoted to the influence of carbon and silicon contents on the achievement of a homogeneous matrix, which is mandatory to get good electrochemical performances. Influence of the composition of silicon surface and intermetallic on the microstructure and electrochemical properties of the composites was also studied. Thus, we have shown that intermetallics reacting moderately with Si during mechanical alloying have better electrochemical properties. The best electrochemical properties have been obtained for the nominal composition Ni0.13Sn0.15Si0.26Al0.04C0.42. This material provides a reversible capacity of 650 mAh.g-1 during 1000 cycles. The use of carbon coated silicon improves the stability of the SEI during cycling even if this composite still has to be optimized
Bertran, Xavier. "Comportement en milieu oxydant d’un composite carbone/carbone pour applications structurales entre 150 et 400°c dans l’aéronautique civile". Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14922/document.
A 2D Carbon/Carbon composite is envisaged for structural parts, operating between 150 and 400°C, in civil aircraft. In this temperature range, the durability of these materials remains unknown because they have never been developed for this kind of applications. A first approach allowed us to correlate the chemical reactivity of the elemental constituents (fiber and matrix) to their structural organization. Then, thermal ageing tests performed on the composite material have demonstrated that a low rate of oxidation could be responsible to a significant reduction of residual mechanical properties. Cracks and fiber/matrix debonding resulting to the elaboration process create an extended pathway to a preferential oxidation of the most reactive compound. This latter is followed by a premature failure by delamination. The reduction of the material properties over long periods is finally discussed in order to evaluate its ability to replace metallic materials in aircraft structural parts
Liang, Wenfeng. "Metal Organic Composites Derived Tin Dioxide/C Nanoparticles For Sodium-Ion Battery". University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1460304081.
Rampai, Tokoloho. "Synthesis of Ti₂AlC, Ti₃AlC₂ and Ti₃SiC₂ MAX phase ceramics; and their composites with c-BN". Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/18463.
Degnan, Craig Cambell. "Processing and wear properties of a (W,Ti)C particulate reinforced ferrous-based metal matrix composite". Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285253.
Batocchi, Pierre. "Pile à combustible à céramique conductrice protonique : développement, optimisation des matériaux, réalisation de cellules élémentaires PCFC opérant dans le domaine de température 400-600 °C". Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20022.
Materials components for a Proton Conducting Fuel Cell (PCFC) operating in the 400 – 600 °C temperature range have been optimised. Electrolyte material optimisation involved finding the best compromise between chemical stability and conductivity. BaCe0.9Y0.1O2.95, synthesised by flash combustion, exhibits the highest protonic conductivity (10-2 S.cm-1 at 600 °C) but reacts strongly with CO2. Partial substitution of cerium by zirconium (BCZY) and niobium (BCYN30) led to a significant improvement of the chemical stability without drastic effect on the conductivity (5 × 10-3 S.cm-1 at 600 °C). The aim for the electrodes is to develop materials which exhibit high electronic conductivity, sufficient degree of porosity and good mechanical properties. The approach comprised the development of elaboration strategies (one-step synthesis, use of porogen) that allow the control of microstructure in order to minimize area specific resistances (ASR) at the anode. As in the case of SOFCs, cathodic materials are mixed ionic-electronic conductors (MIEC). Development of composite cathodes MIEC-electrolyte led to a significant reduction of ASR. PCFC single cell tests showed that performance was mostly dependent on electrolyte thickness and composition, and on the characteristics of nanostructured electrodes with controlled architecture and porosity. Optimisation of assemblies led to fuel cells performances of 156 mW.cm-2 at 600 °C
Edfouf, Zineb. "Étude de nouveaux matériaux composites de type Si/Sn Ni/Al/C pour électrode négative de batteries lithium ion". Phd thesis, Université Paris-Est, 2011. http://tel.archives-ouvertes.fr/tel-00673220.
Rousseau, Guillaume. "Elaboration de voies innovantes pour la protection contre l’oxydation de matériaux composites carbone/carbone utilisés en aéronautique". Electronic Thesis or Diss., Université de Lille (2018-2021), 2021. http://www.theses.fr/2021LILUR035.
This work has been developed as part of a collaboration between the UCCS laboratory and the Safran Landing Systems (Safran LS) company. The aim of this work was to elaborate a new anti-oxidation protection (AOP) for carbon/carbon (C/C) composites marketed as airplane brakes components. The principle of this innovative AOP is based on a so-called internal silicate vitreous diffusion barrier because it is applied under the surface of the C/C composite, combined with an aluminophosphate phase which has a trapping role for the oxidation catalysts. This PAO is formed by impregnating the porosities of the C/C composite with a liquid mixture of precursors, followed by a heat treatment. Several ways of impregnating the C/C composite have been explored: (i) a sequential impregnation of the C/C composite with a first layer of aluminophosphate and a second layer of vitreous phase (or vice versa) or (ii) a simultaneous impregnation of the material with a mixture combining the precursors of the two phases. First, a study of the chemical (by NMR, X-ray micro-tomography synchrotron and XRD) and morphological (by MEBE-HT) evolutions at high temperature of the aluminophosphate was carried out. This study allowed to understand the origin of the loss of efficiency of the aluminophosphate based AOP after a thermal flash at 1200 °C. Then, for the two impregnation routes that we have developed, AOP performance tests were carried out in industrial conditions and characterizations (by NMR, MEBE-HT, thermal analyzes ATD, ATG, HSM) made it possible to link these performances to the chemical structure of the AOP. We have shown that some sequential AOP formulations improve anti-oxidation performance compared to the performance of an industrial AOP based only on aluminophosphate
Gopagoni, Sundeep. "Microstructure Evolution in Laser Deposited Nickel-Titanium-Carbon in situ Metal Matrix Composite". Thesis, University of North Texas, 2010. https://digital.library.unt.edu/ark:/67531/metadc33154/.
Zhang, Zhong Yi. "Visualisation and quantification of the defects in glass-fibre reinforced polymer composite materials using electronic speckle pattern interferometry". Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/22078.
Appiah, Kwadwo Ampofo. "Microstructural and microanalytical characterization of laminated (C-SiC) matrix composites fabricated by forced-flow thermal-gradient chemical vapor infiltration (FCVI)". Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/14910.
Pedoto, Giuseppe. "Characterization and Modelling of the Thermomechanical and Ageing Behavior of PEKK and C/PEKK Composites for Aircraft Applications at High Temperatures (above the Glass Transition Temperature) Characterization of the mechanical behavior of PEKK polymer and C/PEKK composite materials for aeronautical applications below and above the glass transition temperature". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0011.
The nowadays increased awareness towards environmental issues concerns aircraft structures in terms of environmental impact and end-of-life disposal. In this optics, the possibility of replacing in the organic matrix composites (CMO) employed for aircraft applications the non-recyclable thermosetting matrix with a recyclable thermoplastic one is investigated. Moreover, thermoplastic polymers, such PEKK, have the possibility of being employed in warmer structures (e.g. the aircraft pylon), undergoing long duration solicitations (creep).The service temperatures for those structures are higher than the PEKK glass transition temperature, provoking, in the material, a loss of properties deriving from a change of state from solid to rubber, and possibly the activation of crystallization and degradation phenomena, which could also interact. This work aims to identify and model the mechanisms characterizing PEKK behavior, under the structure operative service conditions. This is achieved from the analysis of the results of thermomechanical, physical-chemical and coupled thermomechanical/oxidation tests. The resulting 1-D analytical model of the PEKK behavior, is extended in 3-D and implemented in a multi-scale semi-analytical homogenization / localization method to simulate PEKK based composites under the same conditions, varying the plies orientation and stacking sequence
Rocabois, Philippe. "Stabilité thermochimique des composites céramiques base SiC : approche thermodynamique et expérimentale du système Si-O-C-N". Grenoble INPG, 1993. http://www.theses.fr/1993INPG0085.
Shamshurov, A. V., V. M. Beresnev e N. A. Volovicheva. "Nano-reinforced Quartz Composites". Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35246.
Oubenali, Mustapha. "Synthèse par dépôt chimique en phase vapeur catalytique (C-CVD) de nanostructures de carbone et leurs applications en catalyse et pour des matériaux composites". Thesis, Toulouse, INPT, 2011. http://www.theses.fr/2011INPT0058/document.
In this work, we describe the different forms, the catalytic growth, the structure and properties of carbon nanotubes and nanofibres (Chapter I). Hydroxyapatite was used as catalyst support for the synthesis of multi-walled carbon nanotubes (MWCNTs) and nanofibres (CNFs) by catalytic chemical vapour deposition (C-CVD) in a fluidized bed reactor (Chapter II). After support removal by washing with diluted hydrochloric acid, a theoretical and experimental study of surface oxidation of carbon nanotubes by nitric acid treatment has been performed. It allows to identify and quantify the groups formed on the surface of carbon nanostructures and also to propose a mechanism for the formation of these groups (Chapter III). The functionalized nanotubes and nanofibers have been used as supports for heterogeneous catalysis. The hydrogenation of p-halonitrobenzene was used as model reaction to compare the catalytic performances of ruthenium supported on MWCNTs or CNFs-H catalysts. The influence of experimental parameters such as temperature, nature of the substrate and prior heat treatment (activation) of the catalyst on the catalytic activity and selectivity is presented. The catalytic performances have been correlated to the structure of the catalyst as determined from TEM, TPD, TPR and PZC analysis (Chapter IV). The carbon nanostructures produced have also been used as reinforcement fillers for hydroxyapatite-nanotube composites. We have studied in particular, the germination of octacalcium phosphate crystals under conditions of constant solution composition on the surface of the composite (Chapter V)
Gomina, Moussa. "Etude mecanique de materiaux a structure grossiere : comportement a la rupture de composites a fibres c-sic et sic-sic". Caen, 1987. http://www.theses.fr/1987CAEN2042.
Binte, Mokhtar Hanan. "Contribution to the study of impact damage on composite laminates : the effect of hygrothermal ageing and preloading". Thesis, Dijon, 2012. http://www.theses.fr/2012DIJOS045.
This study examines impact damage processes in three types of CFRP composite materials simultaneously subjected to different hygrothermal and mechanical loading conditions. The composite structures tested are chosen for having particular global isotropic responses when loaded, the aim being to ascertain the exact influence of lay-up sequence on impact damage propagation. The work is presented in four main sections. Firstly by establishing hygrothermal ageing dynamics for the three composite structure types and their behaviour when impacted once or several times ; impact damage is measured and analysed using ultrasonic method. The extent and general morphology of the damage through the material thickness is correlated with mechanical properties and lay-up sequence specific to each material. Secondly the influence of simultaneous load combinations is examined. These include different durations of hygrothermal ageing associated with single or double impacts.The resulting damage incurred is analysed with respect to overall ageing time and time during the ageing cycle when the impact was applied. Thirdly the effect of tensile loading during impact on damage within the material was studied. This was achieved using a specially designed test apparatus that allows loading and impacting conditions to be independently modified. By associating a high-speed digital camera to film specimen impacts it is possible to evaluate a relationship between overall composite specimen stiffness and the impact damage. Finally, in order to identify the most unfavourable situation with regard to impact damage resistance an association between hygrothermal ageing and an applied tensile load is examined
Todt, Andreas. "Beitrag zur Entwicklung neuartiger hybrider Werkstoffverbunde auf Polymer/Keramik-Basis". Doctoral thesis, Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-228698.
Fibre-reinforced ceramic matrix composite materials are characterized by excellent thermal, mechanical and chemical properties. Their high tolerance regarding damaging is a result of the intrinsic fibre structure and porosity. Due to this fact, they offer outstanding dampening characteristics, as is the case for polymeric materials. The production of complex structures is very time consuming and expensive. The integration of simple geometric ceramic composite materials in complex polymeric structures is regarded as a new approach for the production of these materials. These easy-to-produce hybrid ceramic/polymer compound materials combine the advantages of ceramics and polymers in one material system. However, one main disadvantage of these materials is the mutual adhesion of the two components. This article deals with the challenge of the manipulation of the mechanical properties of the C/C composites depending on the intrinsic porosity. This is realized by altering the physical and chemical wetting/coating conditions of the matrix precursor. In addition, the inherent porosity is supposed to increase the effective outer surface and specifically improve the adhesion. For this purpose, a novel carbon precursor with an adjustable open porosity is developed and investigated further. During this different versions of the CFRP and various C/C materials of different production steps are produced and examined. The variation of the precursors is supposed to take place in the polymeric state. The different C/C composites are subsequently thermally bonded with selected polymers and defined consolidation parameters. The mutual joining and connection behaviour is investigated further
YANG, WENSHU. "Preparation, microstructure, mechanical and thermophysical properties of short carbon fibre/SiC multilayer composites by tape casting and pressureless sintering". Doctoral thesis, Politecnico di Torino, 2013. http://hdl.handle.net/11583/2506207.
Charron, Morgan. "Modélisation basée images du comportement thermomécanique de composite C/C". Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0670/document.
C/C composites are used in very high temperature applications, especially in space activities. The ability to design these materials is essential in order to enhance their performances and lower their production costs. This work introduces an images-based multiscale modeling of the thermomechanical behavior of a C/C needled composites. Standard methods cannot describe this very complex architecture.The CEPI model (Computing Effective Properties using Images) is based on one hand on the components properties, some of them having been characterized in the laboratory, and on the other hand on the architecture of the material which is directly obtained using tomography images. The components properties were used on a microscopic model of an idealistic yarn, while the macroscopic model was based on the CT scan data itself. The influence of the internal parameters of the method was studied and discussed, and allowed validating some hypotheses. Finally, the comparison between the numerical and experimental results validates the CEPI model on the linear mechanical behavior and stressed the key axes of improvement for the thermal expansion behavior of these composites
Silva, Márcio Marques da. "Protótipo de uma plataforma para software de cálculos para otimização da trajetória de fibras em revestimento de materiais compósitos". Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/18/18146/tde-30032006-114212/.
In the search of new materials, which have good mechanic strength, low weight and easy manufacturing, appear the composites and reinforced composites leading to an ample area of applications and studies in development. The composites materials have a vast field of application, however when subjected to a bigger effort, they do not show a great strength and a good development when compared to metallic materials. The composites materials when reinforced with fibers multiply their strength considerably, becoming an excellent substitute of materials, which have mechanic strength like metals, which in a strong material to corrosion. In many cases, the reinforced composites substitute the metals with a higher development, for example, like applications of reinforced materials with carbon fiber. This production has to objective, to create a platform to development of a software to a calculation optimization of course the fibers in a composite material, using fibers that come to reinforce it and are able to used by the community in many areas like mechanic, medicine, electric and among others.
Martin, Nicolas. "Composite C/C à matrice nanochargée en alumine et en nitrure d'aluminium". Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0237/document.
A hydrothermal-like process to introduce nano-structured alumina and aluminum nitride in carbon/carbon (C/C) composites is developped. Starting from dissolved reactants in an aqueous media,nanoparticules with various morphology are synthesised. The understanding and control of the processis completed in two steps. In the former the study on simplewafer type substrat allows to identifythe key parameters of the process. During the latter a scaling up of the process is done to allow thesynthesis in situ of C/C composites. The microstructural and some mechanical characterization ofthe four ranges of material produced is achieved.In addition several carbon|alumina and carbon|aluminumnitride are simulated using an ab initiomolecular dynamic approach. The methdology to generate the models consists in sumulating theliquid quench of a high temperature amorphous carbon inbetween fixed ceramic surface, then torelease the constrains. Depending on the system, different organisations of the nano-carbons withinthe surfaces are identified : when the graphene sheets are pependicular to the surface, the modelshows an important number of strong bonds and the simulation traction behavior is good, whereaswhen they are parallel to the surface it leads to weak interface and mechanical behavior.Finally HRMET charasterization of some of the materials produced allows to identify experimentalinterfaces alike to those obtained during themolecular dynamic simulations
Singh, Sherjang. "SiC-C Composite Microelectrode for Biomedical Applications". University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1170556512.
Tesfamhret, Yonas. "Sb/C composite anode for sodium-ionbatteries". Thesis, Uppsala universitet, Strukturkemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-325794.
Battiston, Simone. "PREPARAZIONE E CARATTERIZZAZIONE DI COMPOSITI C/TiO2 PER LO SVILUPPO DI MATERIALI FOTOATTIVI NANOSTRUTTURATI". Doctoral thesis, Università degli studi di Padova, 2010. http://hdl.handle.net/11577/3426920.
L'ossido di titanio è considerato un eccellente materiale fotocatalizzatore grazie alla sua elevata efficienza, alla stabilità fotochimica, all’atossicità e al basso costo. Grazie a queste proprietà, i materiali nanostrutturati di ossido di titanio sono largamente studiati e impiegati in diversi settori tecnologici quali quelli della fotocatalisi, della degradazione fotocalitica di composti organici ed inorganici, della sensoristica e della conversione dell’energia solare in elettricità (O'Regan and Grätzel 1991; Linsebigler, Lu et al. 1995; Mills and Le Hunte 1997; Grätzel 2001; Carp, Huisman et al. 2004; Mor, Varghese et al. 2006; Aprile, Corma et al. 2008; Varghese, Paulose et al. 2009). Il lavoro svolto nell’arco dei tre anni di attività di ricerca effettuata, nell’ambito della Scuola di Dottorato in Scienze Molecolari, presso i laboratori dell’Istituto per l’Energetica e le Interfasi (IENI) del CNR di Padova (sotto supervisione della Dott.ssa Monica Fabrizio), è stato focalizzato sullo studio e ottimizzazione di tecniche di deposizione da fase vapore, physical vapor deposition (PVD) e chemical vapor deposition (CVD), e caratterizzazione chimico-fisica, morfologica e funzionale di materiali nanostrutturati a base di ossido di titanio per applicazioni fotocatalitiche. La strumentazione PVD magnetron sputtering, presente presso i laboratori IENI, è stata adattata per la deposizione di film di natura ceramica, intervenendo sulla configurazione geometrica e meccanica dell’apparato. In seguito, è stato possibile individuare le condizioni ottimali di sintesi per la deposizione di film sottili di ossido di titanio efficienti dal punto di vista fotocatalitico, studiando ed agendo sui principali parametri di processo: modalità DC o RF, tempo di deposizione, movimentazione e riscaldamento del substrato, distanza target-substrato, pressione totale, pressioni parziali dei gas introdotti in camera e potenza trasferita al plasma. Al fine di incrementare l’efficienza fotocatalitica dei film sottili, sono stati condotti diversi tentativi di sintesi introducendo azoto come drogante dell’ossido di titanio. Tale drogaggio è riportato in letteratura (Asahi, Morikawa et al. 2001; Kitano, Funatsu et al. 2006; Asahi and Morikawa 2007) come il metodo più idoneo per ridurre l’energy gap efficace del materiale, permettendo contemporaneamente l’assorbimento di una frazione più ampia dello spettro solare ed il mantenimento della stabilità fotochimica. Parte consistente del lavoro sperimentale è stata impiegata, inoltre, per intraprendere lo sviluppo e l’allestimento di un sistema per la misura della corrente fotoindotta, in seguito ad irraggiamento di luce UV-VIS, dell’ossido di titanio. Lo studio del processo di deposizione su vari tipi di substrati piani (vetro, ITO, silice pura), l’identificazione dei parametri di processo ottimali e la conoscenza acquisita del comportamento di tali sistemi ha permesso, infine, lo sviluppo e la progettazione di nuovi materiali più efficienti dal punto di vista fotocatalitico. In particolare, sono stati progettati e realizzati nanocompositi ibridi, impiegando Single Wall Carbon Nanohorn (SWCNH) come substrati per le deposizioni di ossido di titanio. Negli ultimi anni, infatti, sono stati pubblicati numerosi articoli sulla sintesi di materiali nanocompositi ibridi che impiegano materiali mesoporosi a base di carbonio, con lo scopo di incrementare le proprietà fotocatalitiche dell’ossido di titanio (Orlanducci, Sessa et al. 2006; Liu and Zeng 2008; Wang, Ji et al. 2008; Yu, Quan et al. 2008). Con questo scopo, i SWCNH rappresentano un buon candidato grazie alle loro proprietà elettroniche, caratteristiche morfologiche e all’alta resa di produzione (Kasuya, Yudasaka et al. 2002; Gattia, Vittori Antisari et al. 2007). Essi sono costituiti da aggregati, a simmetria sferica e delle dimensioni dell’ordine del centinaio di nanometri, di coni irregolari di grafene a parete singola di qualche nanometro di diametro e qualche decina di nanometri di lunghezza (Iijima, Yudasaka et al. 1999; Murata, Kaneko et al. 2000; Yudasaka, Iijima et al. 2008). L’incremento dell’efficienza fotocatalitica dell’ossido di titanio nel materiale ibrido SWCNH/TiO2 è giustificato dalla morfologia mesoporosa ad elevata area superficiale di questi aggregati (superiore a 300 m2 g-1) e dalla formazione dell’eterogiunzione con l’ossido, che può ridurre sensibilmente la ricombinazione elettrone-lacuna e incrementare, perciò, l’efficienza globale del processo fotocatalitico (Cioffi, Campidelli et al. 2007; Petsalakis, Pagona et al. 2007). Un importante risultato conseguito nello svolgimento dell’attività di dottorato riguarda l’ottenimento, grazie all’impiego del magnetron sputtering, di una nuova singolare morfologia nanostrutturata dell’ossido di titanio, chiamata “strelitzia-like titanium oxide”, indotta proprio dalla particolare morfologia dei SWCNH impiegati come substrati (Battiston, Bolzan et al. 2009). La successiva attività sperimentale è stata, quindi, indirizzata alla comprensione e all’ottimizzazione dei meccanismi di nucleazione e crescita di queste innovative strutture nanocomposite ibride SWCNH/TiO2. A questo proposito, in collaborazione con l’Istituto di Chimica Inorganica e delle Superfici (ICIS) del CNR di Padova, è stato eseguito un approfondito studio sull’influenza del metodo di deposizione utilizzato su nucleazione e crescita dell’ossido di titanio sui SWCNH, impiegando anche la tecnica metal-organic chemical vapor deposition (MOCVD) (Battiston, Bolzan et al. 2009), che ha permesso di ottenere morfologie del rivestimento molto differenti da quelle ottenute tramite magnetron sputtering. Lo studio e la caratterizzazione del nuovo materiale nanocomposito, ottenuto via MOCVD, ne ha suggerito l’impiego come substrato per la deposizione via magnetron sputtering permettendo, infine, di giungere all’ottimizzazione della nucleazione delle strelitzie di ossido di titanio, sfruttando ogni singolo aggregato di SWCNH. Tale risultato ha permesso, inoltre, di eseguire una approfondita caratterizzazione di tipo strutturale e funzionale della nuova morfologia dell’ossido di titanio che, infine, ha dimostrato possedere proprietà fotocatalitiche superiori rispetto a tutti i materiali a base di ossido di titanio con cui è stata comparata. Le caratterizzazioni dei film sottili e dei nanocompositi ibridi sono state eseguite in stretta collaborazione con diversi gruppi di ricerca appartenenti, oltre che all’Università di Padova e al CNR IENI, anche al CNR-ICIS, al CNR-ITC (Istituto per le Tecnologie delle Costruzioni), l’Università di Torino e Piezotech Japan Ltd, spinoff del Research Institute for Nanoscience con sede a Kyoto (Giappone), presso cui è stato svolto uno stage della durata di tre mesi nell’ambito della convenzione Italia-Giappone a cui prende parte il Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM). Le analisi effettuate sono state di tipo strutturale (XRD e Spettroscopia Raman), composizionale (ICP-MS, SIMS, XPS, Catodoluminescenza), morfologico (SEM, TEM, AFM e profilometro meccanico) e funzionale (misure di fotocorrente e degradazione fotocatalitica di composti organici).
Gough, Neil. "Smectic C materials for ferroelectric applications". Thesis, University of Hull, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419091.
Podgorski, Michael. "Rôle des interfaces dans les propriétés macroscopiques de composites C/C". Thesis, Bordeaux 1, 2009. http://www.theses.fr/2010BOR13852.
C/C composites are widely used as structural parts in oxiding environment. Yet, they become very sensitive to air oxidation for temperature higher than 400°C. This work proposed two methods to improve their oxidation resistance :(i) the fiber/matrix bond is increased by modifying the properties of the carbon fiber surface, and (ii) a fraction of the carbon matrix is substitued by an oxide phase.Introduction of new constituants leads to the creation of new material interfaces. Thus, the influence of the interfaces on the macroscopic properties of the composite is evaluated by physico-chemical and macroscopic characterizations
Reich, Blair Jesse Ellyn. "Cyanide-catalyzed C-C bond formation: synthesis of novel compounds, materials and ligands for homogeneous catalysis". Texas A&M University, 2005. http://hdl.handle.net/1969.1/4987.
Karaveli, Keriman. "Tribological Properties Of Atightly Woven Carbon-carbon Composite". Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606132/index.pdf.
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rk June 2005, 77 pages Tribological properties of a tightly woven Carbon/Carbon (C/C) composite were assessed experimentally in accord with the ASTM pin on disk technique. The C/C composite used in this study was a commercial material (K-Karb) obtained in a panel form. The composite consists of graphite fiber reinforced graphite matrix developed for aerospace applications. The fiber reinforcement was in a plain weave woven fabric form. The tests were conducted by sliding zirconia ball against the C/C composite. The friction coefficient and wear rate were determined as functions of applied load, sliding speed, sliding distance and lubrication in ambient laboratory conditions. Mean friction coefficient of the composite was 0.135 µ
when tested at ambient atmosphere and 0.113 µ
in lubricated environment at a load of 5 N, sliding speed of 0.5 cm/s, and sliding distance of 100 m. The wear volumes determined from surface profile traces obtained on the wear tracks after completion of the tests were used for calculations of the specific wear rates. The specific wear rates of the composite were 0.754 x 10-4 mm3/N.m at ambient atmosphere and 0.437 x 10-4 mm3/N.m in lubricated environment at the load of 5 N, sliding speed of 0.5 cm/s, and sliding distance of 100 m. The specific wear rate of the composite decreased with increasing sliding distance, sliding speed, applied load and also, decreased in lubricated environment. Keywords: C/C composite, tribology, friction, wear, lubricant.
Hope-Ross, Kyle Andrew. "Synthesis and characterization of C₂ symmetric liquid crystalline materials". Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/4088.
Haslam, Gareth Eric. "Ni-C and WC materials as fuel cell electrocatalysts". Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610113.
Wu, Sheng-Chung, e 吳憲昌. "Synthesis of Si/C composite materials". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/37260337925407874376.
國立臺灣大學
化學工程學研究所
94
The major goal of this research is to synthesize Si/C composite materials using chemical vapor deposition method.The material serves as an anode material in the fabrication of Lithium-ion battery. Silicon possesses a large amount of capacity according to the literature,but it also exhibits the problem of dramatic volume expansion and shrinkage during charging and discharging. In order to slove the problem of volume expansion and shrinkage,three approaches are adopted to synthesize Si/C composite materials as follow: 1. Growing up the carbon nanotubes on the silicon surface。 2. Synthesizing nanosilicon of particle size in the range of 30~60nm。 3. Covering the nanosilicons with the carbon nanotubes。 We are used to improve the volume expansion problem and raise the capacity. The new Si/C composite materials produced with the above approaches. Keyword: Si/C composite materials , carbon nanotubes , capacity
Peng, Hao-Ting, e 彭皓廷. "Li4Ti5O12/C composite anode materials for lithium-ion batteries". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/86917230457830517630.
大同大學
化學工程學系(所)
105
In this study, Li4Ti5O12/C composites were successfully synthesized via one step (LTO/C-O) and two step (LTO/C-3T) route, in which citric acid was used as carbon source. The structure, surface morphology and composition were characterized by X-ray diffraction, scanning electronic microscopy, Raman scattering spectroscopy, and transmission electron microscopy. The electrochemical properties of the samples were examined by using the charge/discharge tests, and electrochemical impedance spectroscopy. It was found that one step method (LTO/C-O) can reduced the particle size and uniformly coated carbon layer compared with two step method (LTO/C-T). The discharge capacity retention of LTO/C-3O sample at 1, 5, 10 and 20 C compared to the 0.1C delivered 95.9 %、90.9 %、87.9 % and 80.9 %,In contrast, LTO/C-3T sample only delivered 94.7 %、79.9 %、68.2 % and 50.1 %. However, the excess amount of carbon did not effectively improve the electronic conductivity, ascribing the presence of Ti4+/Ti3+ mixed valence decreased within LTO/C-O and LTO/C-T samples. The discharge capacity retention of LTO/C-7O sample at 1, 5, 10 and 20 C compared to the 0.1C only delivered 94 %、82.5 %、72.2 % and 52.6 %, which is lower than that of LTO/C-3O sample.
Zhang, Yan-Ming, e 張晏銘. "Preparation of Sn/C composite anode materials for lithium ion batteries". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/08296424377416518004.
大同大學
材料工程學系(所)
96
Sn/C composites were prepared via a NaBH4 reduction method with carbon-coated natural graphite and SnCl4 in aqueous solution. Effects of acid washing on the disorder ness and the surface function groups on the surface of carbon-coated natural graphite surface were studied with XRD and Raman spectroscopy. The physical properties of the prepared Sn/C composites were investigated with XRD, TGA and SEM. The electrochemical properties of the prepared samples before and after Sn deposition were estimated with capacity retention study. The results demonstrated that nano-Sn particle deposited on carbon-coated natural graphite can be prepared successfully by having Sn4+ react with hydroxy group on the surface of carbon-coated natural graphite before adding 1,10-phenanthroline. The amount of Sn deposition increases with increasing ratio of Sn4+/NaBH4 addition. The sample prepared with Sn4+/NaBH4 molar ratio of 1/32 shows the most promising cycling performance among the prepared samples.
Chien-Sheng, Liu, e 劉建聖. "Ultrasonic Drilling of C/SiC Composite Material". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/55179002711517828904.
國立清華大學
動力機械工程學系
87
Fiber reinforced ceramic matrix composites have been known for its high strength, low density and high toughness. Ceramic composites provide tailored properties by changing the fiber reinforcing manner and designing proper matrix microstructure. During the past decade, numbers of articles have been reported on the investigation of mechanical properties, fabrications, modeling and applications. The C/SiC composite material possesses superior mechanical properties and high oxidation resistance leading to an important role in high temperatureapplications,for example, high-temperature oven, space plane, etc. Drilling is among the most frequently used machining methods needed for parts production in industrial applications. Since C/SiC composite material is hard and brittle, ultrasonic drilling is considered suitable for the material. In ultrasonic drilling, the material is removed primarily by the association of fracture induced from the hammering of hard abrasive grains. The abrasive particles are excited by the tool vibrating at ultrasonic frequency, e.g. 20KHz, and amplitude of tens of micrometers. A continuous flow of the abrasive slurry flushes away the chips removed in the process. Ultrasonic drilling effectively reduces the concerns often encountered in drilling of composite materials, such as delamination, fiber pullout, microcracking and burrs. Besides, it induces no thermal, chemical, electrical or metallurgical threat to the workpiece. In this paper, the processing and ultrasonic drilling of C/SiC composite material are discussed. The mechanical properties and microstructure of the obtained C/SiC composite material are evaluated. The machining quality varying with the machining parameters is investigated.
Kung, Shu-Hsien, e 龔書賢. "Preparation of Li3V2(PO4)3/C Cathode Composite Materials and Electrochemical Studies". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/d4vsve.
明志科技大學
化學工程系碩士班
102
The work reports the preparation of the Li3V2(PO4)3/C (named as LVP/C) composite material by the hydrothermal method and the post-sintering treatment. By using polystyrene (PS) polymer and polystyrene sphere (PS sphere) the carbon additives as the carbon sources and extra carbon sphere (CS) and graphene used as additives; the hydrothermal process and post-thermal treatment were used in sequence to prepare LVP/C composite material. It was found that the poor electron conductivity problem of the LVP/C materials can be solved by adding those composite carbon sources. In addition, by the micro-Raman spectroscopy analysis result, we found the R value (R = ID / IG) of the residual carbon is 1.01, which illustrates that the graphite-like degree of residual carbon material is quite high. It was also found that the composite carbon precursors of polystyrene sphere (PS sphere, PSS), graphene (Graphene nanosheet, GNS) showed good carbon coverage. From SEM morphology analysis results revealed LVP/C materials with 1D needle-like structure when PS sphere carbon precusor was added. LVP/C with 1D morphology can greatly help to improve the electron transport rate. TEM analysis results displayed that the surface of the LVP/C cathode material has a uniform carbon layer of ca. 5nm; it will help to improve the electrochemical properties. The particle size analysis results revealed that the average secondary particle size is about 3.85μm, and the smaller particles also helps to improve electrochemical performance. Furthermore, adding the graphene in LVP/C can significantly improve the high-rate discharge performance and long-term charge/discharge stability. The experimental results showed that when 2wt.% graphene (GNS) and 5wt.% polystyrene spheres (PSS) as the composite carbon precursor were added into LVP/C, the as-prepared Li3V2(PO4)3/C cathode material showed the best electrochemical performance among the various carbon precusors. When only 5wt.% PSS carbon source was added into LVP/C material, the discharge capacities were 180~185 mAh g-1 and 20~25 mAh g-1 at 0.1C and 10C rates, respectively. While 5wt.% PSS +2wt.% CS composite carbon source were added, the discharge capacities were 195 mAh g-1 and 70~75 mAh g-1 at 0.1C and 10C rates, respectively. Furthermore, when 5wt.% PSS +2wt.% graphene composite carbon source were added, the discharge capacities were greatly enhanced to 190 mAh g-1 and 90~ 95 mAh g-1 at 0.1C and 10C rates, respectively. In condusion, it was found that a suitable amount of 2wt.% grapheme or nano carbon sphere (CS) can markedly improve long-term cycle/high rate discharge performance. The hydrothermal preparation method demonstrated that the as-prepared LVP/C cathode materials had the uniform particle size and chemical compositions. The hydrothermal preparation method is simple and easy to carry out process at a low temperature (<200℃).