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1
Lohner, Kevin Andrew 1974. "Microfabricated refractory ceramic structures for micro turbomachinery". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9479.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1999.Includes bibliographical references (p. 103-109).
The MIT Microengine Project was initiated in 1995 as a joint effort between the Gas Turbine Laboratory (GTL) and Microsystems Technology Laboratory (MTL) to develop a MEMS-based micro-gas turbine engine. The thermodynamic requirements of power-generating turbomachinery drive the design towards high rotational speeds and high temperatures. To achieve the specified performance requires materials with high specific strength and creep resistance at elevated temperatures. The thermal and mechanical properties of silicon carbide make it an attractive candidate for such an application. Silicon carbide as well as silicon-silicon carbide hybrid structures are being designed and fabricated utilizing chemical vapor deposition of relatively thick silicon carbide layers (10-100 [mu]m) over time multiplexed deep etched silicon molds. The silicon can be selectively dissolved away to yield high aspect ratio silicon carbide structures with features that are hundreds of microns tall. Positive mold, negative mold, and hybrid Si/SiC processing techniques appear to be feasible microfabrication routes with potential for increasing microengine performance. Research has been performed to characterize the capabilities of these processes. Specimens fabricated in the course of this research show very good conformality and step coverage with a fine (~0.1 [mu]m diameter) columnar microstructure. Surface roughness (Rq) of the films is on the order of 100 nm, becoming rougher with thicker deposition. Residual stress limits the achievable thickness, as the strain energy contained within the compressive film increases its susceptibility to cracking. Room temperature biaxial mechanical testing of CVD silicon carbide exhibits a reference strength of 724 MPa with a Weibull modulus, m =16.0. This thesis documents the design trades that led to the selection of CVD SiC as the primary candidate refractory material for the microengine, and the initial experiments performed to assess its suitability and guide future material and process development.
by Kevin Andrew Lohner.
S.M.
2
Martin, Rachel (Rachel M. ). "Mechanical testing of rapid-prototyping refractory ceramic print media". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/86278.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, February 2013.Page 30 blank. Cataloged from PDF version of thesis.
Includes bibliographical references.
Additively manufactured (3D-printed) refractory alumina-silica ceramics were mechanically tested to ascertain their ultimate tensile strengths and observed to determine their dimensional consistency over the printing and post-printing process. The equipment used to perform tensile testing was designed and built for use with custom-designed tensile test samples. Two ceramic powders, V18 (electronic-grade alumina, colloidal silica, and organic content) and 403C (200-mesh mullite, organic content, and magnesium oxide), were printed into test samples on ZCorporation ZPrinter® 310 and 510 machines, before being infiltrated with tetraethylorthosilicate (TEaS), and in some cases infiltrated again with a 40% by weight suspension of silica in water (Ludox). Ludox-infiltrated V18 proved to be the strongest medium, with a UTS of 4.539 ± 1.008 MPa; non-Ludox-infiltrated V18 had a UTS of 2.071 ± 0.443 MPA; Ludox-infiltrated 403C was weakest with a UTS of 1.378 ± 0.526 MPa. Within V18, greater silica content lead to greater tensile strength, but this did not hold true for 403C. 403C displayed volumetric shrinkage of about 1.5%, while V18's volumetric shrinkage ranged from 7% to 14%.
by Rachel Martin.
S.B.
3
Esanu, Florin. "Self-flowing refractory castables, study of the hydraulic bond and ceramic matrix formation". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq61086.pdf.
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Carlsson, Mats. "Preparation and characterisation of refractory whiskers and selected alumina composites". Doctoral thesis, Stockholm : Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, Univ, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-113.
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Rydén, Gabriel. "Ab initio lattice dynamics and Anharmonic effects in refractory Rock-salt structure TaN ceramic". Thesis, Linköpings universitet, Teoretisk Fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-174208.
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Transition Metal Nitrides (TMN) are of considerable importance for the industry and have gathered a great deal of interest in the scientific community, mostly due to their unique physical and mechanical properties. To increase the understanding of what enables them to have such extraordinary properties requires the study of lattice dynamics and their phonon dispersion. In this thesis, the transition metal nitride, TaN, is studied extensively along with preliminary results for NbN. The primary tool for this investigation is simulations. Computational methods, such as ab initio Molecular Dynamics (AIMD) and the Temperature Dependent Effective Potential (TDEP) method are used to generate phonon spectra and to compute the lattice thermal conductivity. The results indicate that TaN crystal structure stabilizes dynamically at much lower temperatures than previously established with other methods. The average linear thermal expansion coefficient of TaN is a = 9.0 * 10-6 K-1, which is consistent with other TMN. The phonon-phonon lattice thermal conductivity of TaN follows a similar behaviour as for other TMN. Preliminary result for NbN suggests a behaviour at lower temperatures that are similar to that observed for TaN. However, further investigations are required to pinpoint TaN and NbN transition temperatures more exactly and include effects, such as electron-phonon scattering and isotope effects for a better estimation of the lattice thermal conductivity.
6
Aramide, FO, KK Alaneme, PA Olubambi e 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.
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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.
7
Hilbert, Timothy J. "Factors associated with Reader Disagreement in a 20-year Radiology Study". University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1242835896.
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Hýbal, Ondřej. "Vývoj keramické skořepinové formy pro výrobu rozměrných Al odlitků". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-382053.
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This diploma thesis deals with the choice of the most suitable composition of a ceramic shell mold for aluminum castings made by investment casting technology. The most suitable composition of the ceramic shells is chosen based on the results of the tests and from economic point of view. This thesis also deals with evaluation of the current conditions of the production of ceramic shells in Alucast, s.r.o and recommendations for stabilizing the process of manufacturing ceramic shell molds.
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Heckman, Elizabeth Pierce. "Functionalizing Ceramic Matrix Composites by the Integration of a Metallic Substructure with Comparable Feature Size". Wright State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=wright1621451032485832.
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Kubů, Marek. "Návrh zefektivnění technologie obrábění komínové vložky". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-241905.
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Diploma thesis contains introduction of a company P-D Refractories CZ a. s., where the manufacture of ceramic chimney liners is. Followed by a description and analysis of the product in the entire production cycle, material and product spectrum. Based on the results of current production is created proposal to streamline the machining technology with a view to increase productivity and reduce defective products, which means determine the material of a tool and the method of machining. The work is finished by technical-economic assessment, where the summary and recommendation of the proposed solution are.
11
Soukupová, Lucie. "Optimalizace technologie výroby odlitků ze slitin Al metodou vytavitelného modelu". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230978.
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Diploma thesis is focused to the optimization of the ceramic shell for pouring thin walled aluminium castings by investment casting technology. The main objective is firstly to find the optimal binding system (ceramic slurry) and stucco materials for the shell and secondly its optimal structure and heat treatment (drying of each coat and final shell firing) before metal pouring.
12
Sobrosa, Fabiano Zanini. "Desenvolvimento de materiais cerâmicos refratários com adição da sílica residual proveniente da queima da casca de arroz". Universidade Federal do Pampa, 2014. http://dspace.unipampa.edu.br:8080/xmlui/handle/riu/767.
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Com a intenção de agregar valor à cinza da casca de arroz, subproduto da indústria orizícola, e colaborar para um desenvolvimento sustentável do país, esta pesquisa buscou desenvolver materiais cerâmicos refratários com a substituição parcial da argila pela sílica de casca de arroz (SCA) produzida a partir da geração de energia elétrica. Atualmente, na região da fronteira oeste do Estado do Rio Grande do Sul, existem várias usinas termoelétricas de biomassa para geração de energia elétrica através da queima da casca de arroz. Essa tecnologia vem ao encontro da necessidade de diversificação da matriz energética no país. A indústria orizícola produz no Brasil aproximadamente 12 milhões de toneladas por ano de arroz, e aproximadamente 2,5 milhões de toneladas por ano são convertidos em casca. Caso toda esta casca fosse queimada, gerar-se-iam aproximadamente 500 mil toneladas de cinza, a qual é rica em sílica. Portanto, viabilizar seu aproveitamento tende a reduzir o passivo ambiental, além dos benefícios econômicos. No presente trabalho foi analisado o efeito da substituição parcial da argila refratária por sílica da casca de arroz (SCA) nas propriedades mecânicas e termomecânicas dos materiais cerâmicos refratários produzidos, em percentuais de 5, 10 e 20%. Foram analisadas as propriedades mecânicas desses materiais através de ensaios de resistência à compressão, tração direta, flexão em três pontos e dureza superficial Vickers. Analisaram-se também a retração linear, absorção de água, porosidade aparente e resistência ao choque térmico. Conforme se aumentou a substituição parcial de argila refratária por SCA, foi obtido um melhor empacotamento da mistura granular e, consequentemente, ocorreu uma melhora nas propriedades mecânicas das amostras. Por outro lado, o material apresentou-se mais frágil, com menor resistência ao choque térmico. Não foi encontrada variação na retração linear após a queima, já a absorção de água e porosidade aparente diminuíram conforme se aumentou a substituição da argila pela SCA. A microestrutura do material foi analisada através de análise por microscopia eletrônica de varredura (MEV) e difração de raios-x, onde se identificaram as fases cristalinas na mineralogia do material resultante. Na análise da mineralogia do material observou-se um aumento de pico de cristobalita conforme se aumentou o teor de SCA na mistura, em função da cristalização da sílica livre. Um menor volume de porosidade foi encontrado conforme se aumentou o teor de substituição de argila pela SCA.
With the intention of adding value to rice husk ash, a byproduct of paddy industry, and contribute to sustainable development of the country, this research sought to develop refractory ceramic materials with refractory partial replacement of clay by silica from rice husk (SCA) produced from electricity generation. Currently on the western border of the State of Rio Grande do Sul, there are several biomass power plants for generating electricity by burning rice husk. This technology comes against the need for diversification of energy sources in the country. The paddy industry in Brazil produces approximately 12 million tons of rice per year, of which approximately 2.5 million tons per year are converted into shell. If all this bark was burned, it would generate approximately 500 tons of ash, which is rich in silica. Thus enabling its use tends to reduce the environmental liability beyond economic benefits. In the present work, the effect of partial replacement of silica refractory clay for rice husk (SCA) on the mechanical and thermomechanical properties of refractory ceramic materials was analyzed for percentages of 5, 10 and 20%. The mechanical properties of these materials were analyzed by testing compressive strength, direct-drive, three point bending and superficial hardness. We also analyzed the linear shrinkage, water absorption, apparent porosity and resistance to thermal shock. As increased the partial replacement of refractory clay for SCA in the mixture was obtained a better packing of the granular mixture and, consequently, better results in mechanical properties were found. On the other hand, the material appeared more brittle, with a lower thermal shock resistance. Was not found in the linear shrinkage after firing, the water absorption and apparent porosity decreased as the clay was increased by replacement SCA. The microstructure of the material was analyzed by scanning electron microscopy (MEV) and x-ray diffraction where the crystalline phases identified in the mineralogy of the resulting material. The analysis of the mineralogy of the material was observed an increase of cristobalite peak was increased as the content of SCA, depending on the crystallization of the free silica. A smaller volume of porosity is found according to the increased content of clay replacement SCA.
13
Dalaut-Chen, Huichun. "Étude de l'agglomération de pâtes céramiques : application au prototypage rapide". Vandoeuvre-les-Nancy, INPL, 1994. http://www.theses.fr/1994INPL056N.
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La fabrication directe de moules en matériaux réfractaires est une opération difficile, délicate et couteuse. C’est pourquoi nous avons cherché à développer un procédé de fabrication assistée par ordinateur (FAO) d'objets en trois dimensions. Ce procédé de prototypage rapide comprend deux étapes: la première est la fabrication de l'objet en agglomérant couche par couche une pâte céramique avec un laser CO2; la deuxième consiste en un frittage à température élevée afin de compléter cette opération et d'améliorer les propriétés mécaniques. Nous avons étudié des matériaux adaptés à ce procédé. La pâte céramique retenue se compose d'une poudre d'alumine et d'un liant qui est du silicate de sodium aqueux. Le mécanisme de la solidification de cette pâte pendant le balayage par le faisceau laser et celui du frittage ont été étudiés. La pièce finale est un composé d'alumine et de néphéline. Nous avons également étudié la résistance mécanique et la rugosité de surface des objets obtenus. Ceci permet d'optimiser les paramètres du procédé à savoir la puissance du faisceau laser, la vitesse de balayage, l'épaisseur d'une couche et l'intervalle entre deux passages du faisceau. Il n'y a cependant pas de corrélation simple entre les propriétés mécaniques et les paramètres du procédé. La résistance à la flexion des objets est supérieure à 10 MPa et cette valeur est comparable à celle des autres procédés de prototypage rapide des céramiques
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Akpan, Edem T. Gogot︠s︡i I︠U︡ G. "Viscoelastic toughening of refractory ceramics /". Philadelphia, Pa. : Drexel University, 2004. http://dspace.library.drexel.edu/handle/1860/284.
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Ding, Yang. "Analyse morphologique de la microstructure 3D de réfractaires électrofondus à très haute teneur en zircone : relations avec les propriétés mécaniques, chimiques et le comportement pendant la transformation quadratique-monoclinique". Phd thesis, Ecole Nationale Supérieure des Mines de Paris, 2012. http://pastel.archives-ouvertes.fr/pastel-00743511.
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Les THTZ (réfractaires électrofondus à Très Haute Teneur en Zircone) sont des matériaux utilisés pour la construction de fours verriers. Ils sont composés d'un squelette dendritique de zircone imprégné de phase vitreuse. Cette étude, qui fait partie du programme national de recherche NOREV (Nouveaux REfractaires Verriers), financé par l'ANR (Agence Nationale pour la Recherche), vise à étudier les influences de la morphologie tridimensionnelle de la microstructure et des propriétés des phases sur le comportement mécanique du THTZ, en particulier pendant la transformation quadratique-monoclinique qui intervient lors du refroidissement post-coulée. Les microstructures 3D de différents matériaux ont été investiguées par tomographie X à l'ESRF (synchrotron de Grenoble). Les images 3D segmentées ont donné lieu à des analyses d'images permettant de caractériser la topologie microstructurale des matériaux, à travers de mesures de covariance, de tortuosité et de percolation. Une relation entre la vitesse d'attaque par l'acide fluorhydrique (HF) et la densité de surface du squelette de zircone a été identifiée. En segmentant le squelette de zircone par la méthode des bassins versants (watershed), nous avons pu comparer le niveau de connectivité du réseau de zircone des différents matériaux. Les résultats sont corrélés avec les calculs numériques de la rigidité microstructurale du squelette des matériaux. Après attaque acide et à haute température, un phénomène de flexibilité a été observé sur des éprouvettes minces et a pu être mis en relation avec la connectivité des matériaux. Les mesures de dilatation lors de cycles thermiques ont mis en évidence les effets induits par l'ajout d'yttrine. La phase vitreuse joue un rôle important pendant la transformation de quadratique à monoclinique, en limitant l'endommagement microstructural des matériaux. Le THTZ dopé par l'ajout de 7% d'yttrine présente des propriétés très différentes des autres matériaux : il est plus rigide et ne subit plus la transformation martensitique. Des calculs par éléments finis tridimensionnels, réalisées à partir de volumes élémentaires de la microstructure réelle, ont permis d'estimer l'influence des propriétés des phases constituantes, de leur morphologie et des conditions aux limites sur la contrainte interne responsable de l'endommagement microstructural.
16
Dodd, Simon Peter. "An ultrasonic study of refractory hard ceramics". Thesis, University of Bath, 2002. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760795.
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Tamer, Fouad G. "Compressive behavior of refractory ceramics at elevated temperatures". Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/50281.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1989.Title as it appears in M.I.T. Graduate List, Feb. 1989: Compressive behavior of refractory ceramics at high temperatures.
Includes bibliographical references.
by Fouad George Tamer.
Ph.D.
18
Nartowski, Artur Marek. "Solid state metathesis preparation of hard refractory ceramics". Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394445.
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Palin, Francis Terence. "Engineering data of refractory materials and their significance in real structures". Thesis, Staffordshire University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254393.
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Bigeard, Amélie. "Consolidation et comportement thermomécanique d'un réfractaire mis en forme par coulage d'alumine-mullite-zircone pendant des traitements haute température". Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALI062.
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Les céramiques réfractaires mis en forme par coulage sont utilisées dans les fours verriers pour leur résistance à des conditions extrêmes, comme les hautes températures, les chocs thermiques et la corrosion. L’objectif de ce travail est d’étudier le comportement d’un réfractaire industriel pendant sa production et son utilisation. Le matériau étudié est un réfractaire d’alumine-mullite-zircone. Des formulations alternatives ont été développées pour approfondir la compréhension du matériau.Tout d’abord, les évolutions structurelles (DRX), thermiques (dilatométrie) et thermomécaniques (module d’élasticité dynamique à chaud, contrainte à rupture à chaud) des matériaux pendant des traitements thermiques successifs ont été étudiées. Ces caractérisations ont ensuite été couplées avec des observations microstructurales. Un dispositif a été développé à l’ESRF pour réaliser de la tomographie aux rayons X in-situ, avec une taille de voxel de 0.35 µm, et du MEB in-situ a été utilisé pour suivre les évolutions microstructurales à une échelle plus fine, pendant des cycles thermiques successifs. Deux phénomènes principaux ont été identifiés :- Frittage avec phase liquide pendant la première chauffe, avec des inhomogénéités (agrégats / matrice) induisant du frittage contraint dans la matrice ;- Endommagement thermique par microfissuration, provenant de la différence de coefficient d’expansion thermique entre les agrégats de mullite-zircone et la matrice, pendant le refroidissement, et fermeture / guérison des microfissures pendant la chauffe suivante.Ensuite, la résistance aux chocs thermiques de ce matériau a été étudiée en termes de propriétés mécaniques post-choc thermique et de changements microstructuraux. Un essai de choc thermique in-situ a été spécifiquement développé pour suivre le module élastique dynamique pendant un choc thermique.Enfin, un modèle phénoménologique de frittage et d’endommagement a été proposé. Le modèle est basé sur le module élastique dynamique à chaud, utilisé comme un paramètre accessible permettant de quantifier le frittage et l’endommagement. Il a ensuite été implémenté dans un code éléments finis, appliqué à un test de gradient thermique et comparé à des données expérimentales.Ces résultats proposent une description complète du comportement de cette céramique réfractaire industrielle et ouvrent la voie au développement de solutions plus innovantes pour l’industrie verrièreCastable refractory ceramics are used in glass furnaces for their resistance to extreme conditions, such as high temperatures, thermal shocks and corrosion. The objective of this work is to investigate the behavior of an industrial refractory during its production and use. The studied material is an alumina-mullite-zirconia refractory. Alternative formulations were developed to deepen the understanding of the material.First, the structural (XRD), thermal (dilatometry) and thermomechanical (dynamic hot modulus of elasticity (HMOE), hot strength) evolutions of the materials during successive thermal treatments were studied. These characterizations were then coupled with microstructural observations. A setup was developed at ESRF to perform in-situ X-Ray tomography, with a voxel size of 0.35 µm, and in-situ SEM was used to follow the microstructure evolution at a finer scale, during successive thermal cycles. Two main phenomena were identified:- Liquid phase sintering during the first heating, with material heterogeneity (aggregates vs matrix) resulting in constrained sintering of the matrix.- Thermal damage by microcracking, originating from the thermal expansion mismatch between the mullite zirconia aggregates and the matrix, during cooling, and microcrack healing/closing during subsequent heating.Then, the thermal shock resistance of this material was studied, in terms of both post thermal shock mechanical properties and microstructure changes. An in-situ thermal shock test was specifically developed to monitor the dynamic HMOE throughout a thermal shock.Finally, a phenomenological model of sintering and damage was proposed. The model is based on the dynamic HMOE as an accessible metric to quantify sintering and damage. It was then implemented in a FEM code, applied to a thermal gradient test and compared to experimental data.These results propose a comprehensive description of the behavior of this industrial refractory ceramic and pave the way for the development of innovating solutions for the glass industry
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Corradetti, Stefano. "Study and development of high release refractory materials for the SPES project". Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3422608.
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Throughout the last century, theoretical and experimental research made by the international nuclear physicists community has led to important advancement in the knowledge of the mechanisms that govern the behavior and stability of the nuclei. The technological improvements necessary to support this research has often opened the way to new applications in other field of science and industry which directly reflects in our common life experience.
Nowadays, Europe is becoming more and more a leader in both theoretical and experimental nuclear physics, as testified by the presence on its territory of several institutes and laboratories dedicated to this field of research, like CERN (Organisation Européenne pour la Recherche Nucléaire), the world’s largest particle physics laboratory. Italy, represented mainly by INFN (Istituto Nazionale di Fisica Nucleare), is one of the main members of this community.
One of the most important projects supported by INFN is SPES (Selective Production of Exotic Species), which aim is to develop a facility for the production of radioactive ion beams (RIBs) in one of the four national laboratories of INFN, LNL (Laboratori Nazionali di Legnaro).
The facility is designed to produce and deliver to users both proton-rich and neutron-rich nuclei (range of mass 80-160 amu) to be used for nuclear physics research, as well as other applications in different fields of science. The generation of the aforementioned isotopes will occur inside a properly designed target, which represents the core of the whole project. The choice of the proper material for the target, both in terms of composition and properties, is of vital importance in determining the quantity and type of the produced isotopes.
In this work, the synthesis and characterization of different types of target materials are presented. The results of experimental tests performed on some of the produced materials, in configurations very similar to those intended for the final SPES facility are also reported.
Chapter 1 gives a general overview of the SPES project and its context whereas chapter 2 introduces the main topics related to the on-line behavior of the SPES target, relative to both its layout and to the properties of the material constituting it. Chapter 3 is focused on uranium carbide, which will be used at SPES to produce neutron-rich isotopes; after a description of its main physicochemical properties, the results of two on-line tests performed on target prototypes made of this material is reported and discussed into detail. In chapter 4 the synthesis methods and release-related properties of two potential materials to be used as SPES targets for the production of proton-rich isotopes, boron and lanthanum carbides, are presentedNel corso dell’ultimo secolo, la ricerca teorica e sperimentale condotta dalla comunità internazionale in fisica nucleare ha portato ad importanti passi avanti nella comprensione dei meccanismi che governano il comportamento dei nuclei e della loro stabilità. In molti casi, le innovazioni tecnologiche che si sono rese necessarie per supportare tali ricerche hanno aperto la strada verso nuove applicazioni scientifiche ed industriali con ripercussioni dirette nella vita di tutti i giorni. Attualmente, l’Europa è sempre più leader nel campo della fisica nucleare, teorica e sperimentale, come testimoniato dalla presenza nel suo territorio di svariati istituti e laboratori dedicati a questa specifica area di ricerca, come ad esempio il CERN (Organisation Européenne pour la Recherche Nucléaire), il più grande laboratorio al mondo per la fisica delle particelle. L’Italia, principalmente rappresentata dall’INFN (Istituto Nazionale di Fisica Nucleare), è uno dei principali membri di questa comunità. Uno dei progetti più importanti finanziato dall’INFN è SPES (Selective Production of Exotic Species), la cui finalità è la costruzione di una facility per la produzione di fasci di ioni radioattivi, in uno dei quattro laboratori nazionali dell’INFN, LNL (Laboratori Nazionali di Legnaro). La facility è progettata per produrre e fornire agli utenti isotopi proton-rich e neutron-rich (massa compresa fra 80 e 160 amu) utilizzabili per esperimenti di fisica nucleare, ma anche per altre applicazioni in diversi settori scientifici. La formazione di tali isotopi avverrà all’interno di uno specifico bersaglio (target), che rappresenta il cuore dell’intero progetto. La scelta dell’opportuno materiale per il target, sia in termini di composizione che di proprietà è di vitale importanza nel determinare la quantità e tipo di isotopi prodotti. In questo lavoro, vengono descritte nel dettaglio la sintesi e caratterizzazione di diversi tipi di materiali proposti come target, ed inoltre vengono riportati i risultati di test sperimentali condotti su alcuni di essi, ottenuti in modalità molto simili a quelle a cui saranno sottoposti nella facility SPES. Il capitolo 1 fornisce una presentazione generale del progetto SPES e del contesto scientifico ad esso legato, mentre nel capitolo 2 viene descritto nel dettaglio il comportamento operativo del target SPES, con particolare riferimento alla sua geometria e alle proprietà del materiale che lo costituirà. Nel capitolo 3 vengono presentate le proprietà del materiale scelto come bersaglio per produrre isotopi neutron-rich, ovvero il carburo di uranio; vengono inoltre presentati i risultati di un test sperimentale di produzione di isotopi da parte di un prototipo di target SPES costituito di tale materiale. Il capitolo 4 descrive la sintesi e caratterizzazione di carburi di boro e lantanio, con particolare riferimento alle proprietà riconducibili alla capacità di rilascio di isotopi; tali materiali rappresentano dei potenziali target SPES per la produzione di isotopi proton-rich
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Супрун, О. В. "Перспективи використання матеріалів на основі MAX-фаз". Thesis, Сумський державний університет, 2016. http://essuir.sumdu.edu.ua/handle/123456789/47982.
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В останні кілька років зростає інтерес учених до матеріалів на основі безкисневої кераміки – тернарних сполук, або так званих МАХ-фаз.
Матеріали на основі шаруватих МАХ фаз або наноламінатна кераміка – новий вид легкооброблюваної конструкційної кераміки, яка потенційно може використовуватися в багатьох галузях техніки, і особливо перспективна при роботі в екстремальних умовах. Вважається, що дана кераміка може знайти широке застосування для виготовлення деталей складної форми, що зазнають термічних, хімічних і механічних впливів [1].
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SANTOS, WILSON N. dos. "Contribuicao ao estudo da condutividade termica do material ceramico concreto refratario utilizando a tecnica de fio quente com ajustes por regressao nao linear". reponame:Repositório Institucional do IPEN, 1988. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9901.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Kirabira, John Baptist. "Properties of Ugandan minerals and fireclay refractories". Doctoral thesis, KTH, Materials Science and Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-225.
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Development of products which can be produced from a country’s natural resources is very important as far as the industrialization of a nation and saving foreign exchange is concerned. Presently, industries in Uganda and the other states in the Lake Victoria region import all refractory-related-consumables, as the demand cannot be met locally. Based on the abundance of ceramic raw materials for high temperature applications in the region and the demand for refractories by industries it is pertinent to develop and manufacture firebricks by exploiting the locally available raw materials.
This thesis thus, concerns the characterisation of ceramic raw mineral powders from the Lake Victoria region, more particularly, Uganda, with the aim of developing firebrick refractories from the minerals. Two main deposits of kaolin and a ball clay deposit were investigated to assess their potential in the manufacture of refractory bricks. Raw- and processed sample powders were investigated by means of X-ray diffraction (XRD), thermal analysis (DTA-TG) and Scanning Electron Microscopy (SEM). In addition, the chemical composition, particle size distribution, density, and surface area of the powders were determined.
A comprehensive study on beneficiation of Mutaka kaolin was carried out using mechanical segregation of particles. The aim of the study was to explore other potential applications like in paper filling and coating. The beneficiation process improves the chemical composition of kaolin to almost pure, the major impurity being iron oxide.
A general production process scheme for manufacturing fireclay bricks starting with raw powder minerals (Mutaka kaolin and Mukono ball clay) was used to make six groups of sample fireclay brick. Experimental results from the characterization of formulated sample bricks indeed revealed the viability of manufacturing fireclay bricks from the raw minerals. Based on these results, industrial samples were formulated and manufactured at Höganäs Bjuf AB, Sweden. Kaolin from the Mutaka deposit was used as the main source of alumina while ball clay from Mukono was the main plasticizer and binder material. The formulated green body was consolidated by wet pressing and fired at 1350°C in a tunnel kiln. Characterization of the sintered articles was done by X-ray diffraction, scanning electron microscopy, and chemical composition (ICP-AES). In addition, technological properties related to thermal conductivity, thermal shock, alkali resistance, water absorption, porosity, shrinkage, permanent linear change (PLC), linear thermal expansion, refractoriness under load (RUL), and cold crushing strength were determined. The properties of the articles manufactured from the selected naturally occurring raw minerals reveal that the produced articles compare favourably with those of parallel types. Thus, the raw materials can be exploited for industrial production.
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Kawamura, Mirian Akiko. "Evolução microestrutural de cerâmicas porosas moldáveis à base de alumina e ligadas com cimento de aluminato de cálcio (CAC) e alumina hidratável (AH) durante aquecimento inicial até 1500°C". Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-12032018-103724/.
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Cerâmicas porosas encontram um vasto campo de aplicações tecnológicas, tais como isolantes térmicos em equipamentos siderúrgicos, filtros de fluidos em altas temperaturas e biomateriais. A obtenção dessas estruturas por meio de moldagem direta de suspensões aquosas é uma interessante técnica de conformação, pois, peças com geometrias complexas e de grandes volumes podem ser produzidas. Neste caso, a consolidação ocorre, geralmente, pela ação de um ligante hidráulico, cuja função é garantir níveis mínimos de resistência mecânica à verde. Em sistemas refratários, os ligantes mais utilizados são o cimento de aluminato de cálcio (CAC) e alumina hidratável (AH), devido à alta refratariedade e custos competitivos destes materiais. Nas estruturas porosas à base de alumina, particularmente, eles podem proporcionar valores distintos de porosidade e diferentes tipos de microestruturas. Este trabalho teve como objetivo entender como o CAC e a AH interagem com a alumina. Foram avaliados a evolução microestrutural e os efeitos do teor (10 até 40% em volume de ligante hidráulico) e do tamanho das partículas da matriz (alumina fina e grossa) nas amostras à verde e durante o aquecimento inicial até 1500°C. De modo geral, maiores volumes de ligantes permitiram a obtenção de estruturas à verde mais rígidas e resistentes, porém menos porosas. Além da porosidade total (PT), as microestruturas decorrentes das transformações de fases cristalinas ou amorfas também influenciaram os resultados mecânicos. No caso do CAC, as fases formadas durante as reações in situ ajudaram a melhorar as propriedades mecânicas das amostras, mesmo que acompanhado por um acréscimo em porosidade. Em proporções estequiométricas, os cristais de hexaluminato de cálcio (CA6) formados após tratamento a 1500°C inibiram a densificação, ajudando na manutenção da PT (36,7-46,5%), ainda com boa resistência (acima de 20 MPa em compressão diametral). Nos sistemas ligados com AH, observou-se grandes perdas em propriedades mecânicas antes da sinterização, as quais foram relacionadas ao aumento de densidade real dos precipitados do ligante e à perda de conexão entre as partículas da matriz. Em altas temperaturas, os precipitados de AH auxiliaram a sinterização e garantiram a obtenção de peças porosas quando se utilizou alumina grossa (PT: 44,3-47,7%).Porous ceramics have a wide range of technological applications, such as thermal insulation in steelmaking furnaces, filter for high temperature fluids and as biomaterials. Obtaining these structures through the direct casting of aqueous suspensions is an interesting conformation method since pieces with complex geometries and large volumes can be produced. In this case, the consolidation usually occurs by the action of a hydraulic binder, which provides the minimum levels of mechanical strength in green samples. In refractory systems, the most used binders are calcium aluminate cement (CAC) and hydratable alumina (HA), due to the high refractoriness and competitive costs of these materials. Particularly, in porous alumina-based structures, they can provide distinct values of porosity and different types of microstructures. The purpose of the present work is to understand how CAC and HA interact with alumina. The effects of the binder content (from 10 up to 40% in volume) and the particle size of the matrix (fine and coarse) during initial heating up to 1500°C were studied. In general, larger volumes of binders provided green samples with less porosity but higher mechanical strength. Besides total porosity (TP), the microstructures generated from the transformations of crystalline or amorphous phases also influenced the mechanical results. In the case of CAC, the phases formed by in situ reactions improved the mechanical properties of the samples, despite the increase in porosity. In stoichiometric proportions, the crystals of calcium hexaluminate (CA6) formed after treatment at 1500°C inhibited the densification, favoring to maintain total porosity (36.7-46.5%), even with acceptable mechanical properties (above 20 MPa under diametric compression). In HA-bonded systems, before the sintering begins, a decrease in mechanical properties was noted and related to the increase in density of the precipitates and loss of connection between the matrix particles. At high temperature, the precipitates from HA aided the sintering and guaranteed porous samples in coarse alumina composition (TP: 44.3- 47.7%).
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Frade, Sander Bicalho. "Estudo de massas refratárias de vibração a seco para indutores de fornos de indução". Universidade do Estado de Santa Catarina, 2015. http://tede.udesc.br/handle/handle/1679.
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Previous issue date: 2015-02-27Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Vibration refractory masses are dry granulated materials obtained by combination of several refractory oxides, such as: silica, alumina, magnesia; magnesia-chromite and chrome-alumina. These materials are usually applied by dry vibration process and / or accommodation using special forks. In the process of performance evaluation of dry vibration masses there is a need for proper compaction of the material so that the technological characteristics are retained after sintering and firing, and that the specimens prepared in the laboratory have similar characteristics to those found in practice. With the objective of developing a methodology to study in laboratory of the behavior of refractories for induction furnaces, two magnesia and alumina refractories were selected, with the formation of spinels. These materials were compacted considering as varying the type and amount of additive and the number of impacts on manual compression. The results allowed the construction of densification curves to determine the processing conditions that maximized the densification. Specimens obtained by this process were thermally treated for evaluating of the mechanical strength after curing. The results showed that this developed methodology allows the development of appropriate specimens for the development of studies of dimensional variation and resistance to slag attack.
Massas refratárias de vibração são materiais granulados secos obtidos através da combinação de diversos óxidos refratários, tais como: sílica, alumina, magnésia; magnésia-cromita e alumina-cromo. Esses materiais são normalmente aplicados pelo processo de vibração a seco e/ou por acomodação utilizando garfos especiais. No processo de avaliação do desempenho de massas de vibração a seco existe a necessidade de um adensamento adequado do material para que as propriedades tecnológicas sejam mantidas após a sinterização e queima, e que os corpos de prova preparados em laboratório tenham características semelhantes às encontradas na prática. Com o objetivo de desenvolver uma metodologia para estudo em laboratório do comportamento de refratários para fornos de indução foram selecionados dois refratários de magnésia e alumina, com formação de espinélios. Estes materiais foram adensados considerando como variáveis o tipo e quantidade de aditivo e número de impactos na compactação manual. Os resultados permitiram a construção de curvas de adensamento para determinar as condições de processamento que maximizaram a densificação. Corpos de prova obtidos por este processo foram tratados termicamente para avaliação da resistência mecânica após cura. Os resultados mostraram que a metodologia desenvolvida permite a elaboração de corpos de prova adequados para o desenvolvimento de estudos de variação dimensional e resistência de ataque por escória.
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Santos, Paula Roberta dos. "Investigação das propriedades mecânicas e termomecânicas de materiais cerâmicos refratários produzidos com sílica residual da casca de arroz e fibra de aço". Universidade Federal do Pampa, 2017. http://dspace.unipampa.edu.br:8080/jspui/handle/riu/1956.
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Devido ao elevado teor de sílica presente na cinza da casca de arroz, a mesma pode ser empregada como matéria-prima para a fabricação de cerâmicos refratários. O Estado do Rio Grande do Sul é o maior produtor nacional de arroz. O beneficiamento do arroz gera subprodutos, dentre eles a casca, utilizada como fonte de energia para a secagem do cereal. A queima da casca gera um novo resíduo, a cinza da casca do arroz, que normalmente é descartada em solos ou aterros. Em trabalhos prévios observou-se que materiais cerâmicos refratários produzidos com percentuais de 20% de sílica resultam em um aumento da resistência à compressão e flexão, mas possuem menor resistência ao choque térmico em relação à cerâmica convencional. Desta forma, no presente trabalho utilizaram-se fibras metálicas com o intuito de aumentar a resistência ao choque térmico e a ductilidade dos materiais cerâmicos refratários. Os corpos de prova foram fabricados com adição de sílica de casca de arroz em porcentagens de 15% e 20 % e substituição de 1% e 2% de fibra de aço refratário. Após a queima em 1300º C, foram determinadas as propriedades físicas, mecânicas e termomecânicas do material através de ensaios de absorção de água, densidade de massa, porosidade aparente, resistência à compressão, flexão em três pontos, choque térmico, condutividade térmica e análise de microestrutura do material. A substituição da argila pela sílica resultou em maior resistência mecânica e maior tenacidade, possivelmente devido à diminuição da porosidade e pelo aumento do nível de vitrificação. A cerâmica com 2% de fibra apresentou a maior ductilidade e maior resistência ao choque térmico.
Due to the high content of silica present in rice husk ash, it can be used as raw material for the manufacture of refractory ceramics. The State of Rio Grande do Sul is the largest national producer of rice. The processing of the rice generates by-products, among them the husk, the source of energy for the drying of the cereal. The burning of the husk creates a new residue, the ash of the rice husk, which is usually discarded in soils or landfills. In previous work observed that refractory ceramic materials produced with 20% of silica resulted in an increase in compressive and flexural strength, but showed lower thermal shock resistance than conventional ceramics. Thus, in the present work, metallic fibers were used in order to increase the resistance to thermal shock and the ductility of the refractory ceramic materials. The specimens were fabricated with addition of 15% or 20% of rice husk silica, and substitution of 1% or 2% of refractory steel fiber. After a firing at 1300 °C, physical, mechanical and thermomechanical properties of material were determined by water absorption, bulk density, apparent porosity, compressive strength, three-point bending, thermal shock, thermal conductivity and microstructure analysis of material. The substitution of silica clay resulted in higher mechanical strength and higher toughness, possibly due to decreased porosity and increased level of vitrification. The ceramic with 2% of fiber presented a greater ductility and a greater resistance to the thermal shock.
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COSTA, FRANCINE A. da. "Sintese e sinterizacao de pos compositos do sistema W-Cu". reponame:Repositório Institucional do IPEN, 2004. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11176.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
FAPESP:00/00255-9
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Švec, Jiří. "Fosfátová pojiva v žáruvzdorné aplikaci". Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2015. http://www.nusl.cz/ntk/nusl-234573.
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The doctoral thesis is focused on the study, research and development of refractories with phosphate bonding. Primary motivation is preparation of phosphate-based binders that can be applied for non-shaped insulating material fabricated by “in situ” foaming. The phosphate binders based on Al2O3-H3PO4 system are one of the most common in refractory technology. The amphoteric nature of the aluminium and its oxides require the setting of Al2O3-H3PO4 binders under the higher temperatures. Application of higher temperatures is necessary to obtain the minimal manipulation strength of as-prepared green bodies. The main goal of the work is preparation of ytrium phosphate-based binders via different preparation techniques. Yttrium based binders would allow phosphate refractory preparation by standard way, i.e via reaction between binder and reactive aggregate, without structural disintegration of foamed material even before getting manipulation strength or the final firing procedure. Yttrium is more basic than aluminium and therefore more reactive in Y2O3-H3PO4 system.. Yttrium oxide is highly refractory material and sintered yttrium monophosphate has excellent properties from the thermal and corrosive stability point of view. This fact should compensate higher price of this material. Experimental part of this work studies the possibilities of binders preparation in Y2O3-H3PO4 system. The mixtures were designed to prepare binding phase Y(H2PO4)3. Products of these reactions were characterized in phase and chemical point of view. In order to study and describe setting and hardening processes of phosphate binders, the products were “in situ” analyzed by the thermal analyses and high-temperature diffraction analysis up to the 1300 °C. High temperature products were then characterized by means of phase and chemical composition and morphology.
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Friček, Jakub. "Sledování vlivu keramické vazby na vlastnosti izolačních žáromateriálů". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-225890.
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Thermal insulating refractories are an integral part of each thermal unit since they reduce its energy consumption. The current phenomenon of saving in both environmental and financial aspects reflects in searching for such possibilities to produce at lower manufacturing and material costs. One of the possible ways is to valorise waste materials. The theoretical part then deals with the division of refractory materials, classification of thermal insulation refractory materials and manufacturing technologies. The experiment is focused on the production of insulating refractory materials made from plastic dough with a possibility of using sawdust and materials made by pressing mixture moist, with a focus on coal bottom ash. Both of these technologies will be tested for the possibility of modification by using mixed clays and of increasing the strength by using clays with lower sintering temperature.
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Brodu, Etienne. "Thermal radiative properties and behavior of refractory metals, highly textured metallic coatings and pyrolytic boron nitride on C/C composite for the Solar Probe Plus mission". Thesis, Perpignan, 2014. http://www.theses.fr/2014PERP1203.
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Les travaux menés durant cette thèse s’inscrivent dans le cadre du développement de la mission spatiale Solar Probe Plus (NASA). Cette sonde d’exploration, dont la vocation est l’étude du Soleil, pénétrera la couronne solaire pour y faire des mesures in-situ. Ce travail de thèse a consisté à mener l’étude expérimentale des matériaux constitutifs de la sonde: métaux réfractaires (W, Re, Ta, Mo, Nb, Ti), composite C/C, un revêtement de nitrure de bore pyrolytique (pBN) ainsi que des dépôts métalliques texturés à forte émissivité. L’environnement à l’approche du soleil fut reproduit expérimentalement au sol au laboratoire PROMES-CNRS en associant le four solaire d’1 MW à Odeillo au moyen d’essai MEDIASE (Moyen d’Essai et de Diagnostic en Ambiance Spatiale Extrême). Grâce à ces moyens expérimentaux, ces matériaux candidats ont pu être testés sous formes d’échantillons, à très haute température (1100-2500 K), sous vide (10-4 Pa), ainsi que sous bombardement de protons (1-4 keV, jusqu'à 1018 ions m-2 s-1, pour la simulation du vent solaire). La propriété matériau sur laquelle cette étude expérimentale s’est concentrée est l’émissivité, dans la mesure où celle-ci va conditionner la température des surfaces de la sonde faisant face au Soleil. Celle-ci a été mesurée in-situ dans MEDIASE pendant les différents traitements. Dans le cadre de l’étude des métaux réfractaires, il a s’agit de comprendre la relation entre état de surface et émissivité, ainsi que d’étudier les modifications induites par les traitements. En ce qui concerne les dépôts métalliques texturés ainsi que le dépôt de pBN, leur étude a consisté à évaluer leurs performances radiatives et leurs comportements à haute températureSolar Probe Plus (NASA) will be a historic mission of space exploration as it will consist in the first spacecraft to enter the solar corona. The spacecraft will face harsh environmental conditions that no other spacecraft has ever encountered in the past. One of the most critical technology developments for this mission is thus material science related: the materials constituting all the surfaces directly facing the Sun must be studied and tested in a relevant environment. The study of the candidate materials has been carried out at PROMES-CNRS: refractory metals for the instruments (W, Re, Ta, Mo, Nb, Ti, and their alloys), and refractory ceramics for the thermal protection shield (C/C composite and pyrolytic boron nitride - pBN). Samples of these materials were tested experimentally in a simulated near-Sun environment. This environment was simulated on ground thanks to the association of the 1 MW solar furnace in Odeillo, to the MEDIASE facility. This way materials were tested at very high temperature (1100-2500 K) in high vacuum (10-4 Pa), with the solar wind being reproduced via a proton bombardment (1-4 keV, up to 1018 ions m-2 s-1). The material properties that we have studied the most are the thermal radiative properties as they fully determine the temperature of a free-standing surface exposed to an intense radiative flux in vacuum. For refractory metals, it mainly consisted in studying the relationship between surface state and radiative properties, as well as the effect of the treatments. As for the textured metallic coatings and pBN, it consisted mainly in determining their efficiencies and understanding their behaviors
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Sibil, Arnaud. "Comportement thermomécanique et endommagement de nouveaux réfractaires verriers à très haute teneur en zircone : investigation des mécanismes de fissuration par EBSD et émission acoustique". Phd thesis, INSA de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00701526.
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Cette thèse s'inscrit dans une démarche d'investigation des mécanismes d'endommagement de réfractaires électrofondus à très haute teneur en zircone. L'accent est en particulier mis sur la compréhension du phénomène de microfissuration, mécanisme de dégradation le plus dommageable pour ces matériaux. S'opérant au refroidissement, il conduit à la fracture des blocs électrofondus. Réalisés dans le cadre du programme NOREV (NOouveau REfractaires Verriers) soutenu par l'ANR, les travaux présentés sont le fruit d'une collaboration avec Saint Gobain CREE, le Centre des Matériaux P.M. FOURT de l'Ecole des Mines de Paris, le laboratoire GEMH de l'ENSCI de Limoges, ICAR et Euro Physical Acoustics. Ils font suite aux travaux réalisés lors du programme PROMETHEREF (2002-2005). Des expériences préliminaires ont permis de définir et d'affiner les orientations de l'étude. Prenant en considération l'anisotropie de dilatation de la zircone monoclinique et quadratique décrite dans la littérature, l'imagerie des électrons rétrodiffusés a notamment permis de révéler un lien entre l'arrangement de domaines cristallographiques et la fissuration observée. D'autres expérimentations conduites dans le domaine de l'émission acoustique ont mis en lumière son applicabilité et ses apports pour notre problématique ainsi que la nécessité de développer un algorithme de traitement adapté. Ainsi, trois axes de recherche ont été développés. Ils visent, par leur complémentarité, à permettre une analyse à plusieurs échelles de l'endommagement des matériaux de l'étude tout en s'appuyant sur leur comparaison. Ils permettent respectivement d'évaluer l'endommagement de manière indirecte, d'en examiner les origines à l'échelle microscopique et d'en déterminer l'occurrence en température à l'échelle globale de l'échantillon. Le premier volet consiste en une évaluation des propriétés mécaniques en températures soulignant les incidences de la fissuration. La mise en évidence de la fissuration sous-critique, l'évolution des propriétés élastiques ainsi que la détermination des propriétés à la rupture apportent autant d'éléments qui permettent ensuite d'enrichir l'étude fractographique. Le deuxième volet s'attache, après une interrogation quant à la présence simultanée de zircone monoclinique et quadratique, à déterminer les paramètres de maille et les coefficients de dilatation de ces deux structures pour les différents matériaux. La modélisation des mailles correspondantes se révèle alors d'un grand intérêt pour l'analyse de cartographies EBSD. Enfin, la validation et l'application d'un process de traitement novateur des données d'émission acoustique, intégrant un algorithme génétique, permet de quantifier l'endommagement et d'apporter des précisions quant à son action en température. Ces constatations sont confortées par des suivis par acousto-ultrasons.
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Ourak, Mohamed. "Génération d'ondes élastiques de surface focalisées et applications au contrôle non destructif des céramiques". Valenciennes, 1985. https://ged.uphf.fr/nuxeo/site/esupversions/08205281-2eb2-4571-a6c1-9b61b8e5992e.
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On passe en revue les diverses méthodes de contrôle non destructif et on présente en particulier les techniques de générations et détection des ondes de surface sur matériaux non piézoélectriques. On discute des problèmes de conversion d'une onde plane de volume en une onde de surface. On présente la réalisation de la sonde à ondes de surface focalisées et les performances attendues à partir de modèles théoriques simples. On décrit les montages expérimentaux ayant permis la caractérisation de la sonde et on confronte les résultats obtenus à la théorie précédemment exposée. On présente l'application des ondes de surface focalisées au cas de deux matériaux non piézoélectriques: l'alumine et le carbure de silicium, dans lesquels on relève le profil de défauts non apparents.
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Masson, Isabelle. "Détermination des propriétés mécaniques en fluage a haute température et étude des microstructures de déformation de céramiques a base de nitrure d'aluminium". Vandoeuvre-les-Nancy, INPL, 1993. http://www.theses.fr/1993INPL136N.
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En vue d'applications en sidérurgie dans les nouveaux procédés de coulée continue de bandes minces, plusieurs céramiques à base de nitrure d'aluminium (AlN fritte (SAlN), AlN presse a chaud (HPAlN) et composites al#2o#3-AlN) ont été déformées en compression uniaxiale soit sous contrainte constante (150-250 MPa) soit à vitesse de déformation imposée (5. 10##6s##1) à des températures variant de 1200 à 1650c puis caractérisées en microscopie électronique à balayage, en microscopie électronique à transmission et par analyse EDX. En fluage a charge constante, la vitesse de déformation est proportionnelle à la contrainte appliquée à la puissance 1,5 et varie exponentiellement avec la temperature, l'énergie d'activation apparente ayant une valeur moyenne de 650 kj. Mol##1 (la valeur maximale de la vitesse de déformation atteinte pour HPAlN déformé à 1650c sous 250 MPa étant de 4. 10##6s##1). A vitesse imposée, les courbes contrainte-déformation passent par une contrainte maximale qui croit quand la température diminue (la valeur maximale obtenue pour HPAlN déformé à 1550c étant de 670 MPa) puis décroissent. Après essai, la présence de nombreuses cavités aux joints de grains et aux points triples montre que la déformation est surtout intergranulaire. Les grains se déforment aussi plastiquement par mouvement de dislocations situées majoritairement dans le plan de base et de vecteur de burgers 1/3<1120>. Nous avons également observé plusieurs preuves de la montée de ces dislocations et de glissement dévié dans des plans prismatiques ou pyramidaux favorisée par l'absence de dissociation
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Fontaine, Florian. "Composites à matrice carbone-oxyde et carbone-nitrure : thermodynamique de l'élaboration et son impact sur les propriétés physico-chimiques, thermiques et mécaniques des composites". Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14217/document.
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Les composites carbone/carbone présentent de propriétés thermomécaniques à hautes températures qui les rendent particulièrement adaptés à l’ablation ou à la friction. Leur sensibilité à l’oxydation dès 400°C a conduit à envisager leur dopage en éléments réfractaires inoxydables ou à température d’oxydation élevée. Le procédé sol-gel a permis d’introduire environ 1 % volumique d’oxyde ou de nitrure de titane ou d’aluminium dans leur matrice. Les nitrures sont obtenus par nitruration carbothermique des films d’oxydes. Deux types de sols ont été utilisés : des sols « standard » et des sols enrichis en saccharose. Le saccharose est ajouté pour prévenir la consommation du pyrocarbone lors de la nitruration. Il a par ailleurs une influence sur l’avancement de la nitruration. Les composites chargés sont ensuite densifiés par voie gazeuse, ce qui induit des transformations de phases prévues par la thermodynamique : les films de nitrure de titane sont partiellement carburés (formation de carbonitrure), et les films d’oxyde de titane sont réduits (formation d’oxycarbure). Les dépôts à base d’aluminium sont plus stables et ne subissent aucune transformation. La diffusivité thermique des composites réalisés est faiblement impactée par les charges introduites, alors que les résistances en traction/compression sont sensiblement augmentées. Par ailleurs, une rigidification des composites est observée. Leur cinétique d’oxydation est ralentie. Les composites enrichis en alumine et nitrure d’aluminium présentent des vitesses de perte de masse divisées par 2 par rapport à la référence C/C. Toutes ces propriétés sont liées directement ou non à la composition des sols, et plus particulièrement à sa teneur en saccharose. Il a en effet été montré que les sols qui en contiennent ont tendance à gélifier en surface du composite, ce qui gêne la diffusion des gaz précurseurs au cœur du composite lors de la densification. La porosité finale s’en trouve modifiée. Cette dernière a une influence non négligeable sur le comportement en compression, la diffusivité thermique et la cinétique d’oxydation des composites élaborésCarbon/carbon composites exhibit excellent mechanical and thermal properties at high temperature that make them espe-cially suitable for ablation or friction pieces. Their sensitivity toward oxidation above 400°C has lead to the will of doping them with refractory ceramics that are nonoxidizable or with a high oxidation temperature. The sol-gel process allowed to introduce 1 % in volume of titanium or aluminum oxide or nitride in the matrix. Nitrides are obtained by carbothermal nitridation of the oxide films. Two types of sols were used: the “standard” ones and those with extra sucrose. Sucrose is added to prevent pyrocarbon consumption during the nitridation. Furthermore, it was shown that it has an impact on the nitridation rate. Charged composites are then densified by Chemical Vapor Infiltration, which induces phases transforma-tions that were predicted by thermodynamics: titanium nitride films are partially carburized (formation of titanium carbonitride) and titanium dioxide films are reduced (formation of titanium oxycarbide). Aluminum-based films are more stable and don’t undergo any transformation. Thermal diffusivity of the as-synthesized composites is not much modified by the addition of these ceramics while the tensile and compressive strength are slightly increased. By the way, composites are hardened. Their oxidation kinetics is slowed down. Aluminum-rich composites exhibit a weight loss divided by two compared to the C/C reference. All those properties are directly, or not, linked to the composition of the sols, in particular to their sucrose content. Indeed, it was shown that sucrose-containing sols rather jellify on the surface of the composite, thus preventing the diffusion of precursor gases to the heart of the pieces. The final porosity is then modified. The porosity has an important impact on the compressive strength, thermal diffusivity and oxidation kinetics of the synthesized composites
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Fotso, Gueutue Eric Stéphane. "Spectroscopie Raman résolue en temps pour les hautes températures". Thesis, Orléans, 2018. http://www.theses.fr/2018ORLE2023/document.
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Ce travail présente l’optimisation d’un système de spectroscopie Raman résolue en temps dédiée aux très hautes températures. Ce dispositif répond au besoin sans cesse croissant d’étudier en temps réels les transformations de phases et des cinétiques de réactions dans des environnements extrêmes. Ce dispositif a été validé dans des conditions d’usages sur des oxydes (Gd₂O3, Y₂O3, ZrO₂ , ZrSiO4 et CeO₂) et des nitrures (h-BN). Le potentiel du système a permis de lever les principaux verrous technologiques et instrumentaux qui limitent l’utilisation de la spectroscopie Raman à haute température. Les trois principaux faits marquants qui illustrent le caractère innovant de ce travail sont les suivants : Le premier correspond au nouveau record mondial d’analyse Raman à haute température à travers l’acquisition du mode E₂g de h-BN jusqu’à 2700°C. La comparaison des performances des deux voies Pockels et ICCD montrent que la voie Pockels est plus performante que l’ICCD, mais plus délicate de mise en oeuvre. Le second fait marquant concerne les autres applications du Raman résolu en temps, comme pour séparer la contribution de la diffusion Raman et de la luminescence. La dernière application quant à elle présente l’étude de la dépendance temporelle comparée des diffusions Raman résonnante et non résonante. Le Raman résonnant se déclenche systématiquement avant le non résonnant. Plus généralement, l’intérêt des méthodes Raman résolues en temps ouvre de nouveaux champs d’application dans la caractérisation de matériaux en condition extrêmes, éventuellement in situ : aéronautique, réfractaire ; sidérurgie, nucléaire, etc…This work presents the optimization of a time-resolved Raman spectroscopy device dedicated to very high temperatures. This device meets the ever-increasing need to study in real time phase transformations and reaction kinetics in extreme environments. This device has been validated under working conditions on oxides (Gd₂O3, Y₂O3, ZrO₂ , ZrSiO4 et CeO₂) and nitrides (h-BN). The potentialities of the device have enabled the main technological and instrumental locks that limit the use of high temperature Raman spectroscopy to be removed. The three main highlights illustrating the innovative nature of this work are as follows. The first corresponds to the new world record for high temperature Raman analysis through the acquisition of the E₂g mode of h-BN up to 2700°C.A comparison of the performance of the two Pockels and ICCD channels shows that the Pockels channel is more efficient than the ICCD, but more difficult to implement. The second important fact concerns the other applications of time-resolved Raman, as to separate the contribution of Raman scattering and luminescence. The last application presents the study of the comparative time dependence of resonant and non-resonant Raman scattering. The resonant Raman is triggered systematically before the non-resonant. More generally, the interest of time-resolved Raman methods opens new fields of application in the characterization of materials in extreme conditions, possibly in situ: aeronautics, refractories, steel industry, nuclear, etc
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Ye, Guotian. "Reactive processing of ceramic binding systems for refractory castables". Thesis, 2005. http://hdl.handle.net/2429/17188.
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The general applied objective of this project is to develop hydratable alumina-bonded
castables of properties comparable to the high-temperature fired basic bricks. This work is
focused on improving the sintering of the ceramic binding systems at relatively low
temperatures (~1300°C) through incorporation of ultrafine powders.
Ultrafine magnesium aluminate spinel powders were synthesized using already
known and original methods. Combustible ingredients were incorporated to prevent the
direct contacts of the precursor particles during drying and the combustibles leave a
continuous pore network, when they burn off during calcination at 700-800°C. Mechanical
activation of the spinel precursor prepared using a heterogeneous sol-gel process decreased
the activation energy for spinel formation from 688 kJ/mol to 468 kJ/mol, and lowered the
incipient temperature of spinel formation from 900°C to 800°C, and the temperature of
complete spinellization from >1280°C to 900°C. A new method for preparing
homogeneous spinel precursor was presented and completely crystallized spinel with
specific surface area of 105 m² /g, and crystallite size of 13 nm was formed from the
precursor after calcination at 900°C.
This work established the influence of ultrafine-sized powders on the sintering and
strength development of multi-sized systems rich in large particles at relatively low
temperatures, with emphasis on the temperatures around 1280°C. It was found that the
relationship between the strength and linear shrinkage for the powder compacts consisting
of uniform particle size distribution does not apply to the binding systems with wide
particle size distributions (90 nm - 90 μm). The addition of the ultrafine powders (≤0.5 μm
median) up to 10% had no significant influence on strength in two-component binding systems after firing at 1280°C and 1450°C. However, the ultrafine powders increased the
strength of three-component binding systems presumably because the addition of ultrafine
powders increased effective contacts for sintering.
The particle size of the ultrafine power plays an important role in enhancing the
strength of the castables after heat treatment at 816°C and 1280°C. Aggregate types have
substantial influence on the strength of the castables after firing at 1280°C, eventually due
to the cracks generated by in-situ spinel formation and mismatch in thermal expansion
coefficients between the aggregate and the matrix. Spinel-based castables with high
bending strength (>15 MPa) were obtained with addition of 2% ultrafine spinel (0.2 μm
median) after firing at 1280°C.
This research work also contributes to the reaction mechanisms of hydratable alumina
with various forms of MgO. After hydration at 20°C for 48 h, a hydrotalcite hydrate was
formed in the mixture of hydratable alumina and reactive magnesia, while such a hydrate
was not observed in the mixtures of hydratable alumina and deadburnt or fused magnesite
under the same hydration conditions. After hydration at room temperature for 48 h at 20°C
and then for 12 h at 110°C, hydrotalcite compounds were formed in all three mixtures. The
presence of deadburnt/fused magnesia in hydratable alumina-bonded castables improved
the strength of the castables after drying at 110°C because of the hydrogen bonding of
hydrotalcite and Mg(OH)₂ on magnesia particles. The polycondensation accompanying
dehydroxylation of hydrotalcite and Mg(OH)₂ up to 816°C contributed to the higher
strength of hydratable alumina-bonded castables containing magnesia.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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Esanu, Florin. "Self flowing refractory castables : study of the hydraulic bond and ceramic matrix formation". Thesis, 2000. http://hdl.handle.net/2429/12950.
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Refractories are enabling materials in that their primary function is to facilitate the production of other materials such as metals, glasses, petrochemicals, and cements. They have enabled the utilization of heat to make materials since the Bronze Age. Although, in recent years, a number of studies concerning the many complex variables that determine the rheologic, hydraulic and ceramic properties of Advanced Refractory Castables (ARC) have been performed, the fundamentals of free-flow and of transition from a hydraulic to a ceramic matrix are still only poorly understood. The aim of this study is to provide a scientific base for understanding the flow behavior of A R C and its influence on the formation of ceramic. For this purpose the flow behavior of a series of low, ultra-low and no cement ARC compositions was analyzed. A method for measuring the viscosity of the binding system of ARC was developed. This method allowed for the first time the study of a direct correlation between the rheology of the matrix and the flow of a castable, and therefore a precise and scientific base for determining the influence of different dispersant additives. The rheological parameters of ARC compositions for different amounts of water, silica fume purity, content and type of refractory aggregate were correlated with mechanical strength at high temperatures. Based on the experimental and theoretical work carried out in this study a thorough characterization of the rheology of self-flowing castable refractories was performed. The rheological conditions that allow the early formation of the hydraulic matrix were identified. A new concept of interaction (Flash Flocculation) between the binding system and the spray gunning admixtures was developed. This concept was materialized in a novel type of spray gunning admixture. Laboratory studies as well as a pilot scale experiment confirmed the superiority of the flash flocculating admixture over the setting accelerators, which are currently used as spray gunning admixtures.
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Sharma, Antareep. "A comparative study between Direct Spinel Addition and In-Situ Spinelisation in a Low Cement High Alumina based Refractory Castable". Thesis, 2014. http://ethesis.nitrkl.ac.in/5506/1/110CR0615-4.pdf.
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Spinel containing castables are becoming widely popular due to their high slag resistance, spalling resistance, drying behavior and hot strength. Most of the steel plants today use Magnesia-Alumina spinel system (MgAl2O4). Spinel containing castables can be prepared by two methods: direct spinel addition and in-situ spinel formation. The latter option is cheaper but has a drawback of volume expansion during spinel formation, which may lead to cracking. On the other hand, the pre reacted spinel system is expected to show a better hot strength and mechanical behavior. This project is an attempt to study the properties of both such types and present a contrast between them. Also, the effect of two different types of cement, having different alumina composition, was observed.
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Juan, Chung-Chih, e 阮中奇. "The Study on the Effects of Refractory Filler on Sintering Shrinkage of Glass Ceramic". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/81360423692776573887.
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碩士國立臺北科技大學
材料及資源工程系碩士班
91
Four refractory materials (kaolinite, kyanite, alumina, and mullite) were used in the present study. The glass-ceramic was selected in Nd2O5-TiO2-SiO2 (NTS) and MgO-CaO-SiO2 (MCS) systems which are commercial powder used in the electronic ceramic applications. The results show that the mullite fillers exhibit high relative density (>95%) and limit the shrinkage effects (>10%) in the mullite glass-ceramic composites. Processing parameters such as particle size, addition fractions were also investigated in this study. The mullite-MCS glass-ceramic can achieve high relative density (>98%) by decreasing the mullite particle size to 0.6μm. However, large shrinkage (above 10%) in x-y and z directions were occurred in order to achieve high sintering density. The extent of the additive affects the densification of the mullite glass-ceramic composites. The results show the bulk density declined (from 4.35 g/cm3 to 3.30 g/cm3 in NTS glass-ceramic, from 3.18 g/cm3 to 2.87 g/cm3 in MCS glass ceramic) with increasing of weight concentration of mullite particles. The composite tapes were also made used doctor blade method to investigate the possibility that applied in the electronic ceramic industries. The mullite glass-ceramic composite tapes also show the low shrinkage in x, y and z direction. Conversely, the relative density of sintered composite tapes is lower than that of sintered pellets. The possible explanation is the solid content is less in the mullite glass-ceramic green tape, which generate more pore and lower the relative density.
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Al-Shorman, Ahmed Hassan [Verfasser]. "Refractory ceramic through the ages: an archaeometric study on finds from Fenan, Jordan and other sites / vorgelegt von Ahmed Hassan Al-Shorman". 2009. http://d-nb.info/1000553531/34.
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