Дисертації з теми "In situ ceramic composite"
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1
Mariappan, L. "In-Situ Synthesis Of A12O3_ZrO2_SiCw Ceramic Matrix Composites By Carbothermal Reduction Of Natural Silicates." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/215.
Повний текст джерелаАнотація:
This thesis outlines the work done on in-situ synthesis of Al2O3-ZrO2-SiCw ceramic composites and their property evaluation. The introductory chapter deals with the literature survey on ceramic matrix composites, properties desirable for structural applications and toughening mechanisms associated with these composites. The role of whisker toughening in ceramic matrix composites, the growth mechanisms involved in whisker growth and the conditions that favour or hamper the whisker growth are also discussed. The advantages and disadvantages of in-situ synthesis of composites as compared to physical mixing are also dealt with. The objective and scope of the work undertaken are outlined at the end.
The second chapter describes the experimental techniques associated with carbothermal synthesis and characterisation of reaction products as well as properties of hot pressed bulk composites. The equipments used for this work are described here.
The third chapter focuses on the results obtained by the carbothermal reduction of mixtures of kaolin, sillimanite and zircon taken in various proportions. The formation of the product phases with respect to variations in temperature, variations in composition and effect of catalyst is analysed with the help of XRD while their morphology is analysed using SEM. The conditions favouring the formation of tetragonal zirconia without the addition of stabilizers is also enumerated here.
The fourth chapter deals with the compaction of these composite powders and the evaluation of some physical, thermal and mechanical properties. Density and porosity, coefficient of thermal expansion, modulus of rupture and fracture toughness of the composite specimens are evaluated and compared with binary and ternary composites made by other methods.
Finally the thesis concludes by summarizing the work done and briefly projecting the areas for future work.
2
Aramide, FO, KK Alaneme, PA Olubambi, and JO Borode. "In-Situ Synthesis of Mullite Fibers Reinforced Zircon-Zirconia Refractory Ceramic Composite from Clay Based Materials." International Journal of Materials and Chemistry, 2015. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001844.
Повний текст джерелаАнотація:
Abstract
Understanding the phase transformations/developments that result due to varying the production parameter of
engineering materials is vital to development of new materials. The effects of yttria and niobium oxide on the phase changes
and mechanical properties of mullite fiber reinforced zircon-zirconia ceramic composites produced by in-situ sintering of raw
materials was investigated. Varied amounts of powder zirconia, yttria and niobium oxide were mixed in a turbula mixer with
a fixed composition of clay (70% volume) of known mineralogical composition and mechanically milled in a planetary ball
mill. The blended powders/clay were compacted into standard sample dimensions, and finally fired at 1400°C and held at
varied time of one, two and three hours. The fired samples were characterized using ultra-high resolution field emission
scanning electron microscope (UHR-FEGSEM) equipped with energy dispersive spectroscopy (EDX), and X-ray
diffractometry (XRD). Various mechanical properties of the sintered samples were also investigated. It was observed that the
investigated mechanical properties (with the exception of shrinkages) improved with the amount of raw zirconia initially used
in the samples. It was also observed that addition of niobium oxide favours the formation polymignite phase, while the
presence of both yttria and niobium oxide in the raw materials resulted in the formation of fergusonite phase in the samples.
Both additives favour the phase transformation of zirconia from monoclinic to tetragonal and cubic phases even at
temperature as low as 1400°C. It was concluded that the improved mechanical properties of the samples was due to
strengthening by both mullite fibers reinforcement and phase transformation strengthening.
3
Rabih, Ali. "Élaboration et caractérisation de nanocomposites alumine - zircone à partir de poudres cosynthetisées par voie hydrothermale." Valenciennes, 1997. https://ged.uphf.fr/nuxeo/site/esupversions/337cf2fd-5f79-4072-932a-6fe51f860b1a.
Повний текст джерелаАнотація:
La synthèse hydrothermale a permis de synthétiser des poudres nanométriques de zircone stabilisée à l'oxyde d'yttrium, d'alumine (boehmite) et d'alumine-zircone. La caractérisation physique (diffraction des rayons x, densité, surface spécifique, analyse thermique différentielle, microscopie électronique. . . ) de ces poudres obtenues pour plusieurs températures de traitement hydrothermal a été réalisée. Les paramètres de cogélification des précurseurs de nitrates de zirconyle et d'aluminium par de la potasse ont été optimisés pour obtenir des poudres composites homogènes a l'échelle micronique. La taille de la poudre de zircone varie entre 13 et 25 nanomètres. La boehmite et l'alumine gamma présentent la même répartition granulométrique comprise entre 30 et 70 nanomètres. Le frittage naturel de ces poudres composites est devenu possible grâce à l'ensemencement du gel par de l'alumine alpha fine. Le comportement au frittage sous charge, la caractérisation des propriétés mécaniques (résistance à la flexion, facteur critique d'intensité de contrainte et dureté) et des microstructures ont été étudiés. Les microstructures obtenues sont nanométriques et présentent une répartition homogène entre les deux phases. La zircone présente est sous forme quadratique non transformable les nanocomposites étudiés à 5 et 50 % en volume de zircone présentent des valeurs de facteur critique d'intensité de contrainte améliorées par rapport à l'alumine pure. La résistance à la flexion pour la composition à 5 % de zircone est comparable par rapport à une alumine fine. Par contre nous observons une diminution de cette résistance à la flexion pour le nanocomposite à 50 % de zircone en raison d'un ensemencement insuffisant. Un essai de thermocompression a permis de réaliser des jonctions parfaites sans aucune aspérité et avec une excellente continuité au niveau des interfaces de nos nanocomposites alumine-zircone, ce qui laisse a priori suggérer un bon comportement superplastique.
4
Guel, Nicolas. "Comportement mécanique de composites oxydes : Relations procédé-microstructure-propriétés." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI104/document.
Повний текст джерелаАнотація:
Cette thèse a pour objectif la compréhension fine du rôle de la microstructure sur les propriétés mécaniques de composites à matrice céramique oxydes, en vue de l’introduction de ce type de matériau dans les futurs moteurs d’aviation civile. L’influence des hétérogénéités induites par la mise en forme de ce matériau est particulièrement investiguée. Ces hétérogénéités semblent favoriser l’apparition et la propagation de mécanismes d’endommagement conduisant à la ruine du matériau. L’étude est réalisée sur trois nuances de composites oxydes à tissage bidimensionnel générées à partir de trois procédés de fabrication différents. Ces procédés conduisent à la mise en place de trois types de microstructures. Des caractérisations morphologiques par porosimétrie et par μ-tomographie sont réalisées afin d’estimer la répartition des hétérogénéités et ainsi d’établir les microstructures représentatives de chaque nuance. En se basant sur ces analyses, une étude du comportement mécanique des nuances d’étude est réalisée à plusieurs échelles. Dans un premier temps, une étude des propriétés mécaniques à l’échelle macroscopique, représentative du matériau est effectuée à l’aide d’essais de traction dans le plan de tissage. En parallèle, des essais in-situ sont mis en place afin d’observer l’évolution de l’endommagement des microstructures. Ces observations permettent d’améliorer la compréhension du rôle des hétérogénéités sur l’activation des mécanismes d’endommagement. Le suivi de l’EA (Emission Acoustique) des essais est utilisé pour analyser la cinétique d’endommagement des nuances de composites oxydes. En plus de l’analyse globale de l’activité acoustique, des classifications des signaux d’EA sont réalisées. Ces classifications se basent sur la détection de signaux d’EA à l’aide de deux types de capteurs présentant des caractéristiques différentes. Une labellisation des classes est proposée en confrontant les activités de ces classes aux mécanismes d’endommagement observés lors des essais in-situ. Le couplage de l’ensemble de ces informations permet de constituer le scénario d’endommagement de chaque nuance. Il est ainsi possible d’établir le rôle de chaque type d’hétérogénéités sur le comportement mécanique des composites oxydesThe aim of this thesis is the fine understanding on the influence of the microstructure on oxide-based ceramic matrix composites mechanical properties. These materials are good candidate for new generation of civil aircraft engines. The aim of this work is to establish a relationship between the microstructural defects generated by the manufacturing process and the mechanical behavior of the composite. These heterogeneities seem to influence the appearance and the propagation of damage mechanisms. This study is realized on three kinds of bi-dimensional oxide composites generated from three different manufacturing processes. These processes create three kinds of microstructure. Porosimetric and μ-tomographic analyses allow estimating the distribution of microstructural defects and establish typical microstructure of each oxide composite. Based on these preliminary analyses, mechanical behavior of each kind of oxide composites is studied through several representative scales. On the one hand, mechanical tensile tests are carried out in order to estimate the mechanical properties of the studied materials in the weaving plane. On the other hand, the implementation of in-situ mechanical tests allows the visualization of damage mechanisms appearance and propagation. These observations improve the understanding of the role of microstructural defects on the activation of damage mechanisms. Damage kinetics of each mechanical test are inspected through AE (Acoustic emission) analysis. This monitoring helps to link mechanical behavior with microstructural damage. In parallel with global AE analysis, AE clustering is achieved. These classifications are based on two kinds of AE sensor with different properties. Data fusion from the two sensors is accomplished. This technique allows more robust AE clustering. Cluster labelling is proposed thanks to damage mechanisms observed during in-situ mechanical tests. Damage scenarios are set up owing to macroscopic mechanical test, in-situ analysis and AE labelling. Thus, it is possible to establish the influence of each kind of microstructural defect on oxide-based CMCs mechanical behavior
5
Liu, JingJing. "Carbon nanotubes developed on ceramic constituents through chemical vapour deposition." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/9967.
Повний текст джерелаАнотація:
Carbon nanotubes (CNTs) were successfully grown on the surface of carbon fibre reinforcements in carbon fibre architecture through in-situ catalytic chemical vapour deposition (CCVD). Success was also implemented on powders of oxides and non-oxides, including Y-TZP powder, ball milled alumina powder, alumina grits, silicon carbide powder. Preliminary results have been achieved to demonstrate the feasibility of making ceramic composites consisting of CNTs reinforcements.
6
O'Sullivan, David. "Élaboration et caractérisation mécanique des nanocomposites alumine-carbure de silicium." Valenciennes, 1998. https://ged.uphf.fr/nuxeo/site/esupversions/fa8074c9-3bc2-47e1-a75e-41fa9c276467.
Повний текст джерелаАнотація:
L'objectif de cette étude était de développer un protocole de fabrication de nanocomposites à matrice d'alumine renforcée par des particules nanométriques (< 200 nm) de carbure de silicium utilisant des poudres commerciales et l'eau comme milieu de dispersion, ceci dans un but de faisabilité industrielle. Après la détermination des meilleures conditions de dispersion des poudres d'alumine et de carbure de silicium choisies, les mélanges ont été densifies par pressage à chaud afin d'obtenir des matériaux complètement denses. Malgré la température de frittage plus élevée utilisée pour les nanocomposites (1550°C au lieu de 1400°C), la taille moyenne des grains d'alumine se situant entre 0. 6 et 1. 5 µm est équivalente ou inférieure à celle des grains du matériau monolithique. L'étude des propriétés mécaniques a température ambiante de nanocomposites contenant entre 2. 5 et 25% en volume de SiC a permis de déterminer l'influence de la teneur en dispersoïdes à savoir une augmentation de la résistance en flexion (une valeur de 1 GPA a été obtenue pour le nanocomposite contentant 7. 5% en volume de SiC), une amélioration assez modeste de la ténacité, une légère diminution du module de Young ainsi qu'une faible augmentation de la dureté. L’étude comparative de la résistance au fluage de l'alumine et d'un nanocomposite contenant 5% en volume de SiC a montré que la vitesse de déformation du nanocomposite est 100 fois plus faible que celle de l'alumine pure. Un modèle de blocage du glissement aux joints de grains par les particules de SiC est proposé.
7
Poorteman, Marc. "Fabrication et caractérisation de composites céramiques renforcés par des plaquettes." Valenciennes, 1997. https://ged.uphf.fr/nuxeo/site/esupversions/078152fe-6c38-4759-a136-3513bbe27089.
Повний текст джерелаАнотація:
Dans le cadre de ce travail, nous avons fabriqué des composites céramiques renforcés par des plaquettes céramiques par des techniques classiques de dispersion et de mise en forme et par frittage sous pression. Ces techniques ont permis d'obtenir des matériaux denses avec une dispersion homogène des plaquettes et une microstructure des grains constituant la matrice comparable dans le cas du matériau monolithique et du composite. Un choix judicieux des couples matrice-plaquettes a permis d'étudier l'influence des contraintes générées lors de la descente en température du frittage suite à la différence de coefficient de dilatation entre la matrice et les plaquettes et de la nature de l'interface sur les propriétés mécaniques du composite. Pour chacun des systèmes étudiés, les mécanismes de renforcement à température ambiante se sont avérés multiples. La contribution de chacun de ces mécanismes au renforcement est fonction des contraintes résiduelles et de la nature de l'interface. Cependant dans tous les cas les plaquettes constituent le défaut critique. L'évolution des mécanismes de renforcement avec la température peut être déterminée par les contraintes présentes à haute température (cas du système ZrO2-SiC), mais également par la présence d'une phase liquide à haute température (cas des systèmes Si3N4-SiC et ZrO2-Al2O3). Nous avons également démontré dans le cas du système Si3N4-SiC que le composite présente une meilleure résistance à la propagation sous-critique à haute température par rapport au matériau monolithique et, dans le cas du système ZrO2-Al2O3, que le composite, comme le matériau monolithique, est superplastique
8
Sapardanis, Hélène. "Fissuration à l’interface d’un revêtement plasma céramique et d’un substrat métallique sous sollicitations dynamique et quasi-statique multiaxiales." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEM033/document.
Повний текст джерелаАнотація:
Les travaux présentés dans ce manuscrit visent à étudier la propagation d'un défaut interfacial de géométrie connue soumis à un cisaillement macroscopique à partir d'une méthodologie expérimentale développée durant la thèse qui consiste à i) élaborer un système revêtu céramique/métal dont la morphologie d'interface est contrôlée, ii) introduire un défaut d'interface par la technique de choc laser, iii) soumettre le système revêtu pré-fissuré à un cisaillement macroscopique grâce à une machine de fatigue biaxiale coplanaire et iv) mesurer in situ l'évolution de ce défaut. Le système revêtu subit donc une sollicitation dynamique par la technique de choc laser et quasi-statique par les essais biaxiaux. La morphologie d'interface, paramètre influant sur la fissuration, est également étudiée. Un dépôt d'alumine pure est directement projeté par plasma sur un substrat métallique, un superalliage base cobalt Haynes 188 et un acier inoxydable 304L, sans sous-couche.Un premier travail d'analyse du défaut introduit par choc laser en fonction des paramètres laser et de la morphologie d'interface a tout d'abord été réalisé. Le défaut d'interface résultant se caractérise par une zone délaminée circulaire de quelques millimètres de diamètre et d'une cloque formée par la couche de céramique de quelques dizaines de micromètres de hauteur. Ces dimensions caractéristiques ont été mesurées à partir de techniques d'observation non destructives : profilométrie 3D, observation optique et thermographie infrarouge. La fissuration par choc laser a été étudiée par éléments finis grâce à un modèle de type contact cohésif pour l'interface.La propagation du défaut soumis à un cisaillement macroscopique a été caractérisée expérimentalement grâce aux observations optiques et à la technique de stéréo-corrélation d'images. L'analyse par élément finis du problème a permis d'accéder aux modes de sollicitation le long du front de fissure et de donner une première explication quant aux formes délaminées obtenues expérimentalement. Cette analyse s'appuie sur un modèle de zone cohésive dont les conditions aux limites imposées sont déterminées à l'aide des mesures de déplacement obtenues par corrélation d'images. En particulier, il a été mis en évidence que l’ouverture du front de fissure (mode I), induit par le flambage de la couche et par le chargement macroscopique, favorise la propagation du délaminage qui reste pilotée essentiellement par le cisaillement local (mode II et III). L'influence du cisaillement macroscopique dans le plan de la couche déposée sur la propagation du délaminage interfacial a ensuite été étudiée à partir de trois cas de chargement. Une analyse par éléments finis basée sur la mécanique linéaire de la rupture dans un matériau homogène a permis de déterminer l'influence du cisaillement macroscopique sur le chargement local le long du front de fissureThe work presented in this manuscript aims to investigate the growth of an interfacial flaw, whose geometry is known, under macroscopic shear loading. An experimental methodology is thus developed in which i) a ceramic/metal coated system with controlled interface roughness is processed, ii) an interfacial flaw is introduced using the laser shock technique, iii) a macroscopic shear loading is applied on the coated system using a biaxial in-plane testing device and iv) interfacial crack growth and buckling are measured in situ. Hence, both dynamic and quasi-static loadings are applied on the coated system by respectively the laser shock technique and biaxial testing. The interface roughness, which affects the crack growth, is also considered in the study. A pure alumina coating is deposited by air plasma spraying on a metallic substrate, polycrystalline cobalt base superalloy Haynes 188 and stainless steel 304L substrates, with no bond coat.First, the flaw resulting from the propagation of a laser shock wave has been analyzed according to the laser parameters and the interface roughness. An interfacial flaw is characterized by a circular delamination with a diameter of a few millimeters and a circular blister with a height of a few tens of micrometers. These characteristic dimensions have been measured thanks to non destructive techniques: 3D profilometry and image analysis based on optical observations and infrared thermography. A finite element analysis has been carried out to investigate the crack behavior under laser shock wave propagation using a cohesive contact to account for the interface behavior.The interfacial flaw growth under macroscopic shear loading has been characterized with optical observations and the digital image stereo-correlation technique. The related finite element analysis enabled to identify the local loading along the crack front and gave a first explanation about the shapes of the delaminated area observed experimentally. This analysis relies on a cohesive zone model whose applied boundary conditions are established from the displacements measured by digital image correlation technique. By this way, the delamination growth was revealed to be mostly driven by local shear (mode II and III) and the crack opening (mode I), induced by the buckling of the deposited layer and the macroscopic shear, makes the delamination growth easier. Finally, the influence of the macroscopic shear loading on the interfacial delamination has been studied from three different macroscopic shear loadings. The finite element analysis based on linear elastic fracture mechanics in a homogenous material has allowed to study the influence of the macroscopic shear loading on the local loading along the crack front
9
Hassanin, Hany Salama Sayed Ali. "Fabrication of ceramic and ceramic composite microcomponents using soft lithography." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/1538/.
Повний текст джерелаАнотація:
This PhD project is set out to develop a high precision ceramic fabrication approach suitable for mass production, and to meet the needs of microengine application. A group of new processes have been developed and the results are characterized for fabrication of high precision ceramic oxides and composite microcomponents using soft lithography and colloidal powder processing. The materials chosen in the research are alumina, yttria stabilised zirconia and their composite for their excellent properties at high temperature.
10
McDermott, A. "In-situ coagulation moulding of ceramic suspensions." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287181.
Повний текст джерела
11
Ben, Ramdane Camélia. "Etude et modélisation du comportement mécanique de CMC oxyde/oxyde." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0077/document.
Повний текст джерелаАнотація:
Les CMC oxyde/oxyde sont de bons candidats pour des applications thermostructurales. Le comportement mécanique et les mécanismes d’endommagement de deux composites alumine/alumine à renforts tissés bi- et tridimensionnels ont été étudiés et comparés. La microstructure de ces CMC à matrice faible a été caractérisée à partir de porosimétrie et de CND, tel que thermographie IR, scan ultrasonore et tomographie X, ce qui a permis de mettre en évidence la présence de défauts initiaux. Le comportement mécanique en traction, ainsi qu’en compression dansle cas du CMC à renfort bidimensionnel, dans la direction des fibres ainsi que dans la direction ±45°, aété étudié à température ambiante. Afin d’exploiter pleinement ces essais, nous avons eu recours à plusieurs méthodes d’extensométrie et de suivi d’endommagement, telles que la thermographie IR et l’émission acoustique. Les propriétés mécaniques à rupture ainsi que le module de Young du CMC à renfort bidimensionnel développé à l’Onera se sont avérées supérieures à celles disponibles dans la littérature. Les mécanismes d’endommagement des matériaux ont été déterminés à partir d’observations post mortem au MEB et d’essais in situ dans un MEB, ce qui a permis d’évaluer la nocivité des défauts initiaux. Enfin, l’étude du comportement mécanique de ces composites a permisde proposer un modèle d’endommagement tridimensionnel qui permettra de poursuivre le développement de ces matériaux grâce à du calcul de structure. A l’issue de cette thèse, des pistes d’amélioration des procédés d’élaboration et de choix d’instrumentation à utiliser pour les futures études, notamment en ce qui concerne le suivi d’endommagement, ont également été proposéesOxide/oxide CMCs are good candidates for thermostructural applications. Themechanical behaviour and damage mechanisms of two alumina/alumina composites with two andthree dimensional woven reinforcements were studied and compared. The microstructure of theseweak matrix CMCs was characterized by porosimetry and NDT methods, such as IR thermography,ultrasound scanning and X-ray tomography, which highlighted initial defects. The mechanicalbehaviour was studied through tensile tests, as well as compression tests in the case of the twodimensionalreinforced CMC. These tests were conducted at room temperature, in the fibres directionsand in the ±45° direction. In order to fully exploit these tests, several extensometry and damagemonitoring methods, such as IR thermography and acoustic emission, were used. Young’s moduli andmaximum stresses and strains of the two-dimensional reinforced CMC developed at Onera appearedto be higher than those available in the literature. The damage mechanisms of the materials weredetermined by post mortem SEM observations and in situ testing in a SEM, which made it possible toassess the nocivity of initial defects. Studying the mechanical behaviour of these composites finallyenabled the development of a three-dimensional damage model that will facilitate the furtherdevelopment of such materials, through finite element analysis. Finally, some improvements regardingthe manufacturing processes and the instrumentation for damage monitoring were suggested forfuture studies
12
Hudec, Karel. "Bytový dům ve svahu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-227151.
Повний текст джерелаАнотація:
Subject of master´s thesis is an apartment building in Uhersky Brod. Subject is designed on a sloped site in central urban area of the city. Apartments are placed on three floors above the ground level, in underground floor is situated a garage. Vertical load-bearing structures in lower floors are made of monolithic reinforced concrete, upper floors are made of ceramic blocks HELUZ. Whole building is insulated with external thermal insulation composite system. Horizontal structures are made of monolithic reinforced concrete. Roof is partly mono-pitched, partly double-pitched truss roof.
13
Dunyak, Thomas John. "Properties and performance of a ceramic composite component." Diss., This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-07282008-134634/.
Повний текст джерела
14
Cullinan, Jack Francis. "In-situ repair of composite structures." Thesis, University of Bristol, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.738199.
Повний текст джерела
15
Kim, Hyung Sun. "Development of a fibre-reinforced glass-ceramic composite." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47512.
Повний текст джерела
16
Grosskopf, Paul P. "Mechanical behavior of a ceramic matrix composite material." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/42214.
Повний текст джерелаАнотація:
Monolithic ceramic materials have been used in industry for hundreds of years. These materials have proven their usefulness in many applications, yet, their potential for critical structural applications is limited. The existence of an imperfection in a monolithic ceramic on the order of several microns in size may be critical, resulting in catastrophic failure. To overcome this extreme sensitivity to sman material imperfections, reinforced ceramic materials have been developed. A ceramic matrix which has been reinforced with continuous fibers is not only less sensitive to microscopic flaws, but is also able to sustain significant damage without suffering catastrophic failure.
A borosilicate glass reinforced with several layers of plain weave silicon carbide cloth (Nicalon) has been studied. The mechanical testing which was performed included both flexural and tensile loading configurations. This testing was done not only to determine the material properties, but also to initiate a controlled amount of damage within each specimen.
Several nondestructive testing techniques, including acousto-ultrasonics (AU), were performed on the specimens periodically during testing. The AU signals were monitored through the use of an IBM compatible personal computer with a high speed data acquisition board. Software has been written which manipulates the AU signals in both the time and frequency domains, resulting in quantitative measures of the mechanical response of the material.
This paper will compare the measured AU parameters to both the mechanical test results and data from other nondestructive methods including ultrasonic C-scans and penetrant enhanced X-ray radiography.
Master of Science
17
Stephanie, Yvonne Yee. "A Novel Polymer-Ceramic Composite for Cardiac Repair." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/22908.
Повний текст джерелаАнотація:
Heart failure is one of the most debilitating diseases today, and is responsible for one third of all deaths in the world. Current treatments for heart failure either do not cure the disease, or if they do, are associated with high risk and a range of complications. As such, tissue engineering has emerged as a potential alternative for treating heart failure. Currently, the gold standard for a tissue engineered solution is the cardiac patch, an epicardially attached biomaterial that is designed to support the production of new cardiac tissue. However, the primary challenge is the development of a patch that can provide mechanical support, yet be biologically active enough to promote the development of new cardiac tissue. One material that has the potential to provide both these aspects is poly(glycerol sebacate). This synthetic elastomer can be fabricated to possess similar mechanical properties to the native cardiac tissue, and can withstand the cyclic stresses and strains in the heart. However, there are still difficulties in the attachment of PGS patches to the heart, and its overall bioactivity. This can potentially be addressed by reinforcing PGS with sub-micron platelets of beta-tricalcium phosphate, which is capable of providing mechanical reinforcement to the PGS polymer and improve its ability to facilitate cell attachment and proliferation. As such, this thesis aims to develop and characterise a novel PGS-beta-tricalcium phosphate composite for cardiac regeneration.
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Davies, C. M. A. "Failure mechanisms in glass-ceramic matrix composite laminates." Thesis, University of Bath, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387305.
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Guimaraes, de Sa Rafael. "In-situ and ex-situ incorporation of carbon nanostructures into ceramic-carbon-metal nanocomposites." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526358.
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Marriner-Edwards, Cassian. "The development of fibre-reinforced ceramic matrix composites of oxide ceramic electrolyte." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:3af11d08-c0d8-429b-8eab-d2befc83ea74.
Повний текст джерелаАнотація:
Flammable solvents contained in liquid electrolytes pose a serious safety risk when used in lithium batteries. Oxide ceramic electrolytes are a safer alternative, but suffer from inadequate mechanical properties and ionic conductivity. Thin electrolyte layers resolve the issue of conductance, but accentuate the detrimental mechanical properties of oxide ceramics. The presented work has investigated oxide ceramic electrolyte reinforcement in composite electrolytes for all-solid-state batteries. Fabricating oxide ceramic electrolytes with engineered microstructure enabled development of a reinforced composite. This approach is based on the formation of 3D- porous ceramics via stereolithography printing of polymer templates from designed cubic, gyroid, diamond and bijel architectures. The microstructural parameters of templates were analysed and modified using computational techniques. Infiltration of the prepared 3D-porous electrolyte with polymeric-fibre reinforcement created the reinforced composite electrolyte. The prepared ceramic composite showed excellent reproduction of the template microstructure, good retention of ionic conductivity and enhanced mechanical properties. The final composite was composed of NASICON-type Li1.6Al0.6Ge1.4(PO4)3 oxide ceramic electrolyte and epoxy and aramid fibre reinforcement. The gyroid architecture was computationally determined as having the optimal stress transfer efficiency between two phases. The printed gyroid polymer template gave excellent pore microstructure reproduction in ceramic that had 3D-interconnected porosity, high relative density and the most uniform thickness distribution. The ceramic matrix porosity allowed for complete infiltration of reinforcement by aramid and epoxy forming the fibre-reinforced ceramic matrix composite. The interpenetrating composite microstructure with ceramic and epoxy gave a flexural strength increase of 45.65 MPa compared to the ceramic. Unfortunately, the infiltration procedure of aramid-epoxy reinforcement did not realise the full tensile strength potential of aramid fibres.
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Lyons, Jed S. "Micromechanical studies of crack growth in ceramic matrix composite." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/16086.
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Petla, Harita. "Computational design of ultra-high temperature ceramic composite materials." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Lombardi, John Lang 1968. "Injection solid freeforming of polymer and ceramic composite materials." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282251.
Повний текст джерелаАнотація:
Solid freeform fabrication processes (SFF) have been the subject of much research and discussion within recent years. Unlike other near net shape manufacturing processes (i.e. conventional injection molding, casting, or bulk machining), SFF techniques fabricate parts "from the ground up" by the sequential deposition and curing of raw material slurry layers upon each other until the final part results. Precise spatial control of deposited layers is achieved through CAD software and hardware interfaced with the SFF apparatus. The development of suitable SFF compatible raw material formulations and appropriate processing parameters are discussed in this dissertation. In particular, a wide range of materials have been fabricated and characterized at AML and ACR using this technique including alumina., crosslinked acrylate, and high molecular weight Nylon 6 thermoplastics. Comparisons are made between the mechanical properties of the SFF and corresponding commercial conventionally processed materials. Finally, the heat transfer and polymerization kinetics associated with three model SFF resin formulations are discussed and compared to corresponding empirical SFF process observations.
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Winn, Elizabeth Jennifer. "The fabrication and properties of an in-situ reinforced ceramic." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627351.
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Issa, Inas. "In situ TEM nanocompression and mechanical analysis of ceramic nanoparticles." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI008/document.
Повний текст джерелаАнотація:
Dans cette étude, nous proposons d’utiliser la compression in situ dans le MET afin de caractériser les propriétés mécaniques de nanoparticules céramiques dont la taille caractéristique est de l’ordre de quelques dizaines de nanomètres. Nous appliquerons cette méthode à des nanocubes monocristallins de MgO, une céramique modèle dont la plasticité est bien connue dans le matériau massif. Les essais de nanocompression montrent que les nanocubes de MgO se déforment de façon homogène jusqu’à de grandes déformations (>50%) sans fissure apparente. L’analyse des résultats est assistée par des méthodes de corrélation d’images numériques et simulations de type dynamique moléculaire. Le mécanisme de déformation et l'effet de taille sur la limite élastique sont identifiés. Dans une deuxième partie de la thèse, nous présentons une étude sur des nanoparticules d’alumine de transition compactée en CED (Cellule à Enclumes en Diamant) à température ambiante, sous plusieurs pressions (5 GPa, 15 GPa et 20 GPa). Des lames minces préparées par FIB ont été étudiées en MET. Des images HRTEM montrent une texture cristallographique qui devient plus importante à des pressions plus élevées. Une orientation cristallographique préférentielle est observée, avec les plans {220} de la phase gamma de l’alumine la plupart du temps parallèles à la surface de contact avec une particule voisine. Ce comportement mécanique est cohérent avec un système de glissement, connu pour les structures spinelles. Une corrélation de ce comportement avec les tests in situ MET réalisés sur des nanoparticules similaires, par Emilie Calvié lors de sa thèse, est présentée. Enfin, des clichés de diffraction de type Debye Scherrer sont réalisés sur ces lames minces de nanoparticules d’alumine de transition compactées en CED à différentes pressions. L’analyse quantitative de ces clichés montre une transformation de phase de ces nanoparticules d’alumine de phase gamma en phase delta, de manière croissante avec la pressionIn this study, we propose an innovative mechanical observation protocol of ceramics nanoparticles in the 100nm size range. This Protocol consists of in situ TEM nanocompression tests of isolated nanoparticles. Load–real displacements curves, obtained by Digital Image Correlation, are analyzed and these analyses are correlated with Molecular Dynamics simulations. By this protocol a constitutive law with its mechanical parameters (Young modulus, Yield stress...) of the studied material at the nano-scale can be obtained. In situ TEM nano-compression tests on magnesium oxide nanocubes are performed. Magnesium oxide is a model material and its plasticity is very well known at bulk. The MgO nanocubes show large plastic deformation, more than 50% of plastic strain without any fracture. The TEM results are correlated to MD simulations and the deformation mechanism can be identified.The size effect and the electron beam effect on the yield strength are investigated. In a second part of the dissertation, we present a study on transition alumina nanoparticles compacted in a Diamond Anvil Cell at different uniaxial pressures. Thin Foils of these compacted nanoparticles are prepared by FIB for HRTEM Observations. Their analysis reveals the plastic deformation of the nanoparticles. The crystallographic texture observed inthese compacted nanoparticles in DAC shows a preferred orientation of the {110} lattice planes, orientated perpendicular to the compression direction. This is compatible with the slip system. This argument was reinforced with a preferred orientation of slip bands observed during in situ TEM nano-compression tests. Moreover, electron diffraction patterns (Debye Scherrer) analysis on these compacted transition alumina nanoparticles reveals the decrease of the presence of gamma-alumina and the increase of delta-alumina with increasing pressure. This reveals the phase transformation with increasing pressure from gamma to delta* alumina
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Lee, Kok Loong. "Deformation behaviour of Cu-Cr in-situ composite." Thesis, University of Leicester, 2004. http://hdl.handle.net/2381/11077.
Повний текст джерелаАнотація:
With the increasing requirements for higher strength materials with high electrical conductivity, a lot of interest has been paid to develop Cu-based composites in the last 25 years. These composites have superior tensile strength, combined with good electrical conductivity, to that exhibited by pure Cu and conventional Cu alloys. To date, much of the research carried out on this composite has focused on the mechanical and electrical properties of the as processed material. However, there is a basic lack of understanding of the way in which the properties may change or degrade during service. Without this knowledge, these composites cannot be fully and safely exploited. Thus the objective of this study was to investigate the thermo-mechanical behaviour of a Cu-Cr composite, and the nature and extent of any damage mechanisms occurring within the composite over a wide range of experimental conditions. Neutron diffraction was used to investigate the deformation behaviour of the individual phases in the composite and their interaction through elastic and plastic loading at room temperature. For the composite, a fairly good agreement was observed in the phase strains predicted by the Eshelby theory and measured by neutron diffraction. In-situ tensile tests in the SEM were also performed to study the damage mechanism of the composite. Tensile and creep tests were carried out in air and in vacuum over a wide range of temperatures. To provide data for comparison with the composite material, pure Cu specimens were tested whenever possible. Creep resistance increases significantly with the introduction of Cr fibres into Cu. The higher creep rate of the composite in air than in vacuum is due to the gradual decrease of the cross-sectional area of the matrix due to increasing thickness of the oxide layer. Damage characteristics and distributions were found to be similar during tensile and creep testing.
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Wenger, Matthew Paul. "Ferroelectric ceramic/polymer composite sensors for insitu acoustic emission detection." Thesis, Bangor University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362129.
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Ma, Le. "Wear Behaviour of Biolox delta ceramic Composite for Joint Replacements." Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.522486.
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Miersch, Sören, Ralph Schubert, Thomas Schuhmann, Uwe Schuffenhauer, Markus Buddenbohm, Markus Beyreuther, Jeannette Kuhn, Mathias Lindner, Bernd Cebulski, and Jakob Jung. "Ceramic-like Composite Systems for Winding Insulation of Electrical Machines." IEEE, 2020. https://htw-dresden.qucosa.de/id/qucosa%3A74384.
Повний текст джерелаАнотація:
Insulating sheets, impregnants and encapsulation materials commonly used for winding insulation offer low thermal conductivities. This leads to an increased heating of the winding of electrical machines and to the existence of hotspots. The electromagnetical utilization of the machine has to be reduced with respect to the allowed maximum winding temperature. In this paper, the development and experimental investigation of novel polysiloxane composites with ceramic fillers are presented. The materials are tested by means of impregnated and encapsulated samples of a round-wire winding as well as the main insulation of electrical steel sheets and laminated cores. Numerical models are implemented for determining the equivalent thermal conductivity of the winding compound comprising the enameled wire and the impregnant. Based on the example of a permanent-magnet synchronous machine with outer-rotor in modular construction, the potential for increasing the electromagnetical utilization is shown.
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Bischoff, Matthew Lee. "CHARACTERIZATION OF CERAMIC MATRIX COMPOSITE MATERIALS USING MILLIMETER-WAVE TECHNIQUES." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1362655198.
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Otieno, Geoffrey. "Processing and properties of aligned carbon nanotube/glass ceramic composite." Thesis, University of Oxford, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.560925.
Повний текст джерелаАнотація:
Previous attempts to produce carbon nanotube (CNT) ceramic composites have resulted in poorly dispersed, unaligned and non-continuous CNTs in the composites with modest improvements in properties. The research presented in this thesis pertains to the production of dense aluminoborosilicate (ABS) glass matrix composites containing aligned and continuous multi- walled carbon nanotubes (MWCNT) of millimetre lengths. This was achieved by infiltrating CVD grown MWCNT preforms using a precursor sol and sintering which achieved 80 ± 2% dense composites. Focused ion beam milling together with image analysis showed that the composites contained 20 ± 2 vol.% MWCNTs, which are aligned and continuous within the glass matrix. Indentation studies showed greater damage tolerance in the composite compared to unreinforced ABS glass. Under compression, there is no significant change in the compressive strength between the composite and the unreinforced glass. The bend strength of microcantilever beams were 1.4 to 1.3 GPa for the composite and glass respectively. Elastic modulus of 84 GPa and fracture toughness (Kic of up to 2.4 MPa √m were obtained for the composite. The elastic modulus and fracture toughness results are an improvement of 30 % and 240 % over that of unreinforced ABS glass. Fracture surfaces showed apparent MWCNT pullout lengths of up to ~ 1 urn. Analysis indicates that crack bridging by intact MWCNTs provides the majority of the improvement in fracture toughness. Interlayer sliding of the MWCNTs and "sword in' sheath" failure mechanism of the MWCNTs prevented the maximum potential performance, with respect to elastic modulus and fracture toughness, from being achieved. Electrical conductivity in the alignment direction of the CNTs showed improvements by a factor of 106 compared to unreinforced ABS glass. Furthermore, improvement of a factor of ~ 10 in the thermal conductivity was obtained for the composite over that of ABS glass.
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Trandel, Barbara Dawn. "Nondestructive evaluation of a high temperature ceramic matrix composite material." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-01312009-063125/.
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Erdem, İlker Çiftçioğlu Muhsin. "Preparation of ultrafiltration/ microfiltration ceramic composite membranes for biotechnology applications/." [s.l.]: [s.n.], 2002. http://library.iyte.edu.tr/tezler/master/biyoteknoloji/T000299.pdf.
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Parham, Hamed. "Ceramic-carbon nanotube composites and their potential applications." Thesis, University of Exeter, 2012. http://hdl.handle.net/10871/8141.
Повний текст джерелаАнотація:
Carbon nanotubes (CNTs) have been the subject of intensive research for nearly two decades, and this is due to their exceptional lightness, large aspect ratio, extraordinary mechanical, electrical, thermal properties and additional multi-functional characteristics. Ceramics have high stiffness and good thermal stability with a relatively low density, and they are an important constituent in the fabrication of advanced composites where high thermal and chemical stability are important. However, brittleness has limited their application in many structural applications. The combination of ceramic (alumina in particular) and CNTs, endeavouring to develop functional composites, offers a very attractive system for research and development. The fabrication of such alumina-CNT composites at bulk scale is therefore highly desirable for industrial applications. However, the synthesis of such composites possesses many technical challenges which need to be addressed. Poor synergy between the matrix and CNTs, potential damage to CNTs, obtaining a uniform and agglomeration-free distribution of CNTs within the matrix, and high cost of CNTs and processes involved in their composite fabrication have proved to be the significant challenges. In this thesis, the focuses are laid on addressing these issues and on the fabrication of specially engineered composites for particular applications such as filter and composites with improved mechanical properties. In this regard, it has been tried to directly fabricate CNTs in different ceramic matrices based on the application requirements. After that, the critical issues and challenges in the fabrication of these functional materials have been clearly investigated and by introducing novel methods and approaches, it has been tried to solve these problems. Also, a new polymer-ceramic-CNT composite has been fabricated by using two different thermoset (epoxy resin) and thermoplastic (polyamide 12) matrices. In this regard, good interfacial bonding between the composite elements along with good wettability of ceramic and CNTs with polymer had to be addressed as critical issues and challenges in the fabrication process. If the adherence at the interface is not strong enough, the material will tear and fail easier. In contrary, a tailored functionalization of CNTs can lead to an improved wettability and as the results, strong interfacial adhesion and bonding between the composite elements. These dominating factors will improve the degree of filling which results in existence of fewer voids inside the composite. These voids will act later as stress points and reduce the composite strength. At the end, the mechanical properties of the fabricated samples have been assessed. The CNT filters have been tested in the removal of bioorganic (yeast cells) and inorganic (heavy metal ions) contaminants from water, and of particulates from air, and they all showed very promising results. More than 99.6% of the air particles (size ranges from 0.3 to 10 µm) were filtered using 300 mm long CNT filter. A complete removal of heavy metal ions from water was reported particularly for single ion. 98% of the yeast cells were filtered. Different factors involved in the filtration efficiency such as ceramic pore size, length of filters, CNT loading and injection rates have also been discussed. Furthermore, the mechanical properties (compression test, hardness and impact test) of the composite materials (including ceramic-CNT, epoxy resin-ceramic-CNT and polyamide-ceramic-CNT composites) have been assessed. During impact test, the epoxy resin-ceramic-CNT composite absorbed 117.2% and 32.7% more energy compared to the pure epoxy resin and epoxy resin-ceramic composite, respectively. The epoxy resin-ceramic-CNT composite sustained 40% more elastic deformation before breakage compared to the epoxy resin-ceramic composite as a result of the CNT reinforcement. The addition of CNTs to the polyamide12-ceramic composite increased its yield stress by 41%. All of these results represent a big leap towards practical applications for the composite reported in the thesis, which may open up new opportunities for CNT engineering at industrial scales, due to the easy fabrication methods introduced and the promising performance they have exhibited.
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Koh, Yeow Leung 1976. "In-situ structural health monitoring of composite repair patches." Monash University, Dept. of Mechanical Engineering, 2002. http://arrow.monash.edu.au/hdl/1959.1/7698.
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Stewart, Samantha B. "Fabrication and characterisation of anisotropic ceramic/polymer composite for orthodontic brackets." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.681745.
Повний текст джерелаАнотація:
Objective: To develop and then test a novel hybrid ceramic/ resin material for use as a possible aesthetic Orthodontic bracket material. Design: A laboratory investigation into the production of a hybrid ceramic/ resin material using the technique of freeze casting, followed by characterisation using mechanical testing methods. Setting: Dental biomaterials laboratory, School of Oral and Dental Science, Bristol Materials and Methods: The technique of freeze casting was used to create porous ceramic frameworks, which were then infiltrated with epoxy resin. In this way bespoke gradated hybrid materials, ranging from 10% to 40% ceramic at one surface and near 100% epoxy resin at the other were created. Samples were characterised using compressive strength and abrasion test methods and compared with samples of pure ceramic and pure epoxy resin. Results: There was no significant difference in compressive strength between pure ceramic and the 40% by volume ceramic samples. Compressive strength was significantly lower for samples with 10%, 20%, 30% ceramic and for samples of 100% epoxy resin. Following abrasion testing the mean difference in surface roughness over 2 years of simulated tooth brushing was less than 1.5 microns for any of the specimens. Conclusions: Novel hybrid ceramic/ resins can be created using freeze casting, with 40% ceramic by volume showing the greatest promise as a potential aesthetic orthodontic bracket material. It behaved similarly to 100% ceramic at what would be its oral surface and should likewise perform similarly to a polymeric bracket at the enamel surface.
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West, Grant. "Microstructure and mechanical performance of SiC/BMAS glass-ceramic matrix composite." Thesis, University of Warwick, 1997. http://wrap.warwick.ac.uk/66932/.
Повний текст джерелаАнотація:
A diverse range of microscopy techniques and mechanical testing methods have been used to characterize glass and glass-ceramic composites. The focus of the work has been a commercially available Barium Magnesium Aluminosilicate matrix reinforced by Tyranno SiC based yam type fibres. The mechanical behaviour has been related to the microstructure through use of models from the literature. The temperature range of study has been from room temperature to 1300°C in air. The microstructure of the BMAS(fyranno was a diphasic mixture of celsian and indialite/cordierite although the manufacturers intention was a monophasic bariumosumilite. The carbon rich interface was found to be thin (l0-15nm) but the composite displayed impressive strength when compared to similar glass-ceramic composites reported in the literature. The matrix could be converted to the equilibrium bariumosumilite phase by heating in an inert atmosphere at 1370°C (or possibly lower) but matrix elemental diffusion into the fibres is likely to impair fibre strength. Tensile failure was by conventional matrix microcracking with load transfer to the in line fibres. However the composite strength was found to be dependent upon the strain rate as was the microcracking threshold associated with cracking of the 0° plies. Failure of the UD BMAS(fyranno was by longitudinal splitting before the expected ultimate strength (from the 0,90° results) was reached. This was due to an apparent notch sensitivity in this fibre architecture, a trait not observed in the 2-D composite. Direct measurement methods were used to establish the interfacial shear strength and these were compared to various models. These were based on matrix cracking thresholds, matrix crack spacing and a relatively new method where an 'inelastic strain index' was found from loading and unloading curves or hysteresis loop widths. Greatest fidelity with the direct methods was found with the last of these models. As with all composites with carbon enriched interfaces oxidation of the interface and fibres was found to impair strength when tested in air at temperatures as low as 600°C and possibly below this when testing at lower strain rates. At high strain rates, near room-temperature-strengths were achieved, even at 1l00°C, as the degrading effects of the oxidizing environment had less time to act. Long term exposure at high temperatures (1200°C) was responsible for formation of an embrittled surface layer up to 70J.lm thick. Within this layer the fibres were severely degraded and strong bonding prevailed at the interface. At temperatures in excess of the expected fibre pyrolysis temperature, (l100°C), the composite was seen to shrink along the length of the fibre axis and dilate normal to it which was attributed to fibre instability. Stabilising the fibres by heat treatments at 1200°C for 24 hours was seen to improve the creep performance in terms of the total strain accumulated within the 100 hours of the creep tests. The creep was comparable to other commercial glass ceramics (CAS/Nicalon and BMAS/BN/SiC/Nicalon) indicating the dominance of fibre creep properties on those of the composite. Cycling of the creep load seemed to result in a greater embrittled depth from the surface but failure at 100MPa and 1200°C was not observed within 240 hours of testing. Other systems were investigated such as the CAS/Nicalon, MAS/Nicalon and AS/Nicalon. Of these the AS/Nicalon was used for modelling the creep behaviour since it represented a simple system where matrix creep was accompanied by elastic deformation of the fibres. A model from the literature was used to explain an apparent increase in the elastic modulus during load cycling at high temperature and also the lower strain accumulation seen during load cycling compared to conventional creep tests.
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Oberg, Erika Karin. "Energy-based mechanics of ballistic impact on ceramic/composite protective plates." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648617.
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Goff, Adam Carter. "Modeling and Synthesis of a Piezoelectric Ceramic-Reinforced Metal Matrix Composite." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/10143.
Повний текст джерелаАнотація:
A mathematical model has been created based on J.D. Eshelby's equivalent inclusion method that can predict the elastic modulus and damping capability in the form of Joule heat for any piezoelectric ceramic-reinforced metal matrix composite system. Specifically, barium titanate (BaTiO₃), lead titanate (PbTiO₃), and zinc oxide (ZnO) piezoelectric ceramics have been modeled as dispersed particles shaped as spheres, prolate spheroids, and discs within a host of common structural metallic matrices including 304 stainless steel, mild steel, aluminum, brass, copper, lead, magnesium, nickel, Ni-20wt%Cr, tin, titanium, Ti-6Al-4V(at%), and tungsten. Composite systems that were predicted to exhibit the greatest level of damping capacity include copper, aluminum, and magnesium matrices reinforced with PbTiO₃, BaTiO₃, and ZnO, in descending order of damping magnitude. In general, higher-conducting, lower-stiffness metallic matrices coupled with more-piezoelectric, higher-stiffness ceramic reinforcement resulted in the greatest level of predicted damping capability and enhanced composite elastic modulus. Additionally, a Ni-20wt%Cr-30v%BaTiO₃ composite has been created using mechanical alloying processing. Specifically, pure constituent powders were combined stoichiometrically in a SPEX milling vial utilizing a charge ratio of 4:1 and subsequently milled for 24 hours. Separate composite powder samples were then annealed in a hydrogen tube furnace at 400°C,
500°C, and 600°C for one and five hours at each temperature. X-ray diffraction was performed on the as-milled and the annealed powders revealing that each was composed of the starting constituents in the appropriate proportions. Representative powders were mounted and polished using common metallographic procedures and microstructures were examined by optical microscopy, scanning electron microscopy, and transmission electron microscopy. All of the powders exhibited a good dispersion of BaTiO₃ particles ranging in diameter from 1μm to about 25nm with no noticeable difference between the as-milled and the annealed powders.Master of Science
40
Owens, Lindsay. "Characterization of Ceramic Composite Materials Using Terahertz Non-Destructive Evaluation Techniques." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1342668277.
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Dev, Bodhayan. "Characterization of Ceramic/Glass Composite Seals for Solid Oxide Fuel Cells." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1400847202.
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Schlegl, Harald. "Microstructure and electrochemical performance of fully ceramic composite anodes for SOFCs." Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/6361.
Повний текст джерелаАнотація:
Solid Oxide Fuel Cells could play a key role in energy systems of the future because they can directly convert the chemical energy of fuels into electrical energy in a reliable and energy efficient way. The choice of materials for the components of fuel cells is crucial for the achievement of the high performance and the low price necessary to establish fuel cell technology in the energy market. Current state of the art anodes consisting of nickel and yttria stabilised zirconia (Ni/YSZ) offer good electrochemical performance but suffer from limitations like carbon deposition, redox instability and sulphur poisoning. This thesis explores the properties of composite fully ceramic anodes consisting of a skeleton of yttria stabilised zirconia (YSZ) or cerium gadolinium oxide (CGO) and a perovskite phase based on B-site doped lanthanum strontium titanate. The perovskite phase was fabricated in situ inside the pores of the skeleton material by the infiltration of an aqueous precursor and subsequent firing (impregnation method). Material characterisation of the composite anodes was carried out by X-ray diffraction and the microstructure investigated by electron microscope techniques. The electrochemical performance was tested by IV-curves and impedance spectroscopy. Particularly the investigation of the connection between the microstructure of the impregnated anodes and their electrochemical performance is a main objective of this work. The electrochemical performance of cells with a CGO skeleton and an impregnated lanthanum strontium titanate phase was found to be inferior compared to cells with a YSZ skeleton, even if the ionic conductivity of CGO is known to be higher than the ionic conductivity of YSZ. The difference was assigned to mass transport problems tightly connected to the different microstructure of the composite anodes. A significant improvement of the performance could be achieved by the utilisation of A-site deficient perovskites as impregnated phase in a YSZ skeleton. Cells with composite anodes of YSZ and La₀.₄Sr₀.₄Ti₀.₉₄Mn₀.₀₆O[sub](3-δ) show power densities of 156.2 mW/cm² at a measuring temperature of 750 °C compared to 58.5 mW/cm² measured in a similar cell with A-site stoichiometric LSTM, both cells having an electrolyte thickness of around 60 μm. The superiority of the performance of anodes with A-site deficient perovskites is mainly due to a lower ohmic resistance of only 0.5 Ω*cm², indicating better conductivity of the composite with A-site deficient perovskites. The investigation of the microstructure of composite anodes with A-site deficient perovskites showed the decoration of the surface with nanoparticles after reduction. These nanoparticles originate from exsolution of ions from the B-site of the perovskite and can't be found in A-site stoichiometric perovskites. The influence of fabrication parameters like firing temperature of the skeleton, firing temperature after impregnation or vacuum impregnation on the microstructure and electrochemical performance of the composite anodes was studied. Particularly the increase of the firing temperature of the skeleton from 1400 °C to 1500 °C resulted in an impressive improvement of total cell resistance and maximal power density.
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Khan, Yusuf M. Laurencin Cato T. "Development of a polymer/ceramic composite scaffold for bone tissue engineering /." Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/470.
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Boden, Keith McMurray. "The development of an YBaâ†2Cuâ†3Oâ†7â†-â†#delta# composite superconductor." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306992.
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Polley, Neal John. "Development of Al-Mgâ‚‚Si in situ composites." Thesis, Brunel University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274812.
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Aldridge, Matthew. "Aspects of the processing, mechanical properties and thermal shock behaviour of a ductile particle toughened alumina." Thesis, University of Surrey, 1996. http://epubs.surrey.ac.uk/605/.
Повний текст джерела
47
Tang, Chao. "Modelling of Thermo-Mechanical Behaviour of Ceramic Matrix Composite Tows and Laminates." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509397.
Повний текст джерела
48
Pryce, A. W. "Matrix cracking and stress/strain behaviour of continuous fibre ceramic composite laminates." Thesis, University of Surrey, 1991. http://epubs.surrey.ac.uk/843150/.
Повний текст джерелаАнотація:
Matrix damage and its effects on mechanical properties have been examined for SiC (Nicalon1) fibre reinforced glass and glass ceramic matrix composites under quasi-static and fatigue loading conditions. Nicalon/Pyrex laminates of different lay-ups have been tested under quasi-static tension. The elastic moduli have been measured and matrix damage monitored as a function of applied strain. The mechanical properties are strongly influenced by the presence of crystalline regions in the matrix which promote microcracking. Laminated plate theory is used to provide bounds to the moduli of the laminates. For unidirectional and simple crossply Nicalon/CAS2 laminates the quasi-static stress/strain behaviour and associated matrix damage accumulation have been examined in detail. The damage development with applied stress was quantified by counts of crack density (in both longitudinal and transverse plies), stiffness loss and cumulative residual strain. The quasi static stress/strain behaviour during continuous tests (accumulating damage) and discontinuous tests (constant damage) have been modelled using a stress analysis based on Aveston, Cooper and Kelly (ACK) theory. The continuous stress/strain behaviour of (0/90) crossply laminates has been modelled using a shear-lag analysis developed previously to describe the transverse ply cracking behaviour of polymer matrix composites. The analysis is modified to account for longitudinal ply cracking. Matrix damage development in unidirectional and (0/90) crossply laminates under quasistatic cycling and high frequency fatigue loading have been studied. For unidirectional laminates stable stress/strain hysteresis loops were obtained during quasi-static cycling, corresponding to stable matrix damage states. These and similar loops obtained after high frequency fatigue are modelled using, the discontinuous stress/strain analysis. It is suggested that the effect of high frequency fatigue is to decrease the interfacial shear strength.
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McClorey, Catherine. "Compositional and mechanical properties of polymer/ceramic composite materials for medical applications." Thesis, University of Ulster, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369954.
Повний текст джерела
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Asif, Imran Mohammed. "Characterisation and biological impact of wear particles from composite ceramic hip replacements." Thesis, University of Leeds, 2018. http://etheses.whiterose.ac.uk/20563/.
Повний текст джерелаАнотація:
The high prevalence of osteolysis and aseptic loosening associated with the wear particles of conventional metal-on-UHMWPE (MoP) total hip replacements (THRs), and concerns over the release of metal wear particles and metal ions around the body from metal-on-metal (MoM) THRs, led to the development of alternative ceramic-on-ceramic (CoC) THRs. CoC bearings are of great interest due to their superior wear properties, compared to MoP and MoM bearings. Historically, ceramic THRs had a reputation for fracture, and recent issues have centred around surgical positioning and squeaking. The development of improved manufacturing methods allowed major improvements of ceramics which led to the introduction of composite ceramics for example, zirconia-toughened, platelet reinforced alumina or ZTA, otherwise commercially known as BIOLOX® Delta. The wear performance of composite CoC THRs such as those using BIOLOX® Delta has been extensively investigated, however no studies have reported the combined characteristics and biocompatibility of the wear debris generated from these bearings. Understanding wear particle characteristics and their biological activity is an essential step in the pre-clinical testing of joint replacements. However, currently for composite ZTA CoC bearings there is a lack of relevant studies, due to difficulties in generating high volumes of clinically-relevant ceramic wear debris in vitro, in addition current particle isolation methods are not sensitive enough to reliably isolate wear particles from hip simulator lubricants, due to the inherent low wear rates of the composite ZTA ceramics. Hence, the particles have not been systematically characterised and therefore little is known about their size, morphology and biological responses. Therefore, the aim of this study was to investigate the characteristics and biological activity of wear particles generated from composite BIOLOX® Delta ZTA CoC THRs. This study developed a two-step particle isolation method and subsequently applied it to hip simulator lubricants for the isolation of composite ceramic wear particles generated from BIOLOX® Delta CoC bearings tested under edge loading conditions. The high sensitivity of this new particle isolation method coupled with its effective removal of protein, allowed the successful recovery and characterisation of very low volumes of both micro and nano-scale wear particles, generated from composite ZTA CoC hip replacements for the first time. The recovered wear particles demonstrated a bimodal size range, which has been previously reported for wear particles generated from alumina ceramic hip replacements. A comprehensive evaluation of the biological impact of commercially-obtained composite BIOLOX® Delta ZTA ceramic model particles and clinically-relevant composite BIOLOX® Delta ZTA ceramic wear particles was investigated in terms of cytotoxicity, inflammation, genotoxicity and oxidative stress. The clinically-relevant composite ZTA ceramic wear particles were generated in water lubricant using a hip simulator under severe edge loading conditions. The biological impact of the ceramic particles was assessed using L929 fibroblast cells and peripheral blood mononuclear cells (PBMNCs) isolated from healthy human donors. Both the model and clinically-relevant BIOLOX® Delta ceramic wear particles demonstrated significant reduction in the viability of L929 fibroblast cells at very high doses (500μm3 of particles per cell), however no cytotoxic effects were observed at the lower clinically-relevant doses (0.5-0.05μm3 per cell). The BIOLOX® Delta ZTA ceramic model particles failed to stimulate an inflammatory response in terms of TNF-α release and did not cause any significant DNA damage or production of reactive oxygen species (oxidative stress) in PBMNCs from all donors. However, high doses (50μm3 per cell) of clinically-relevant BIOLOX® Delta ZTA ceramic wear particles caused significantly elevated levels of TNF-α release from PBMNCs. But, there were no significant effects in terms of DNA damage and oxidative stress in PBMNCs from all donors. This study demonstrated that there was a threshold volume of clinically-relevant ceramic wear particles required to stimulate significant TNF-α release from PBMNCs. However, these doses were not clinically-relevant and highly unlikely to occur in vivo due to the extremely low wear rates of CoC bearings. This comprehensive study indicated that composite ZTA Delta ceramic hip replacements had a low biological impact, which may enhance long-term clinical performance. The results from this study are only relevant for BIOLOX® Delta ZTA ceramics and not other manufacturers ceramics.