Thèse (M.Eng.)--Université du Québec à Chicoutimi, 2002. / Document électronique également accessible en format PDF. CaQCU

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-04-26T14:15:43Z No. of bitstreams: 1 jeansoaresmiranda.pdf: 6014272 bytes, checksum: a6aaf905414159a41b45b4d6a499eb38 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-05-02T00:50:50Z (GMT) No. of bitstreams: 1 jeansoaresmiranda.pdf: 6014272 bytes, checksum: a6aaf905414159a41b45b4d6a499eb38 (MD5) / Made available in DSpace on 2016-05-02T00:50:50Z (GMT). No. of bitstreams: 1 jeansoaresmiranda.pdf: 6014272 bytes, checksum: a6aaf905414159a41b45b4d6a499eb38 (MD5) Previous issue date: 2016-01-25 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O objetivo dessa pesquisa foi avaliar a influência do tempo de condicionamento com ácido fluorídrico a 10%, sobre a resistência de união entre uma cerâmica Y-TZP vitrificada e um cimento resinoso. Blocos pré-sinterizados de cerâmica Y-TZP (IPS e.max® ZirCAD - Ivoclar-Vivadent) foram cortados para obtenção de 40 amostras. Previamente à sinterização, os blocos foram regularizados com lixas d’água de granulação #180, #600 e #1200. Eles foram, então, divididos aleatoriamente em quatro grupos (n=10), sendo um o grupo controle no qual foi realizada a silicatização com Rocatec Soft (RS) e três grupos teste vitrificados com glaze spray (VITA Akzent Plus, Vita Zanhfabrik, Bad Sachingen, Alemanha), com diferentes tempos de condicionamento com ácido fluorídrico a 10% (Condac Porcelana, FMG, Brasil) executado na superfície destinado a adesão: por 20s (GS20s), 60s (GS60s) ou 100s (GS100s). Para cimentação foi utilizado um adesivo universal (Single Bond Universal, 3M ESPE) contendo monômero MDP em sua composição e um cimento resinoso dual (RelyX Ultimate, 3M ESPE). Em cada bloco foram obtidas duas colunas de cimento, totalizando 20 amostras por grupo. Após termociclagem, o teste de cisalhamento foi realizado (EMIC,DL 2000), a resistência de união foi registrada e utilizada para cálculo da resistência adesiva. Além disso, a análise de falha também foi realizada em todas as amostras com um estereomicroscópio (Stemi 2000-C). Uma amostra extra de cada grupo teve metade de sua superfície tratada para obtenção de imagens por perfilometria e microscopia eletrônica de varredura (MEV), além de realização de espectrometria por energia dispersiva (EDS). O teste de Kruskal-Wallis apresentou p valor igual a 0,001 e o teste de Dunn demostrou diferença apenas do grupo RS (22,10Mpa) para os grupos GS (GS20s: 8,10Mpa; GS60s: 10,49; GS100s: 7,53), porém não houve nenhuma diferença dentre os diferentes grupos GS. As imagens de perfilometria e MEV revelaram um padrão irregular de disposição do glaze após o condicionamento com HF 10%. Por meio da perfilometria foi possível aferir a espessura da camada do glaze remanescente (GS20s: 5 ± 1μm; GS60s: 4 ± 1μm; GS100s: 3 ± 1μm). Todas as falhas foram adesivas. E foi possível concluir que a resistência de união entre uma cerâmica Y-TZP vitrificada e um cimento resinoso com MDP não é influenciada por diferentes tempos de condicionamento com ácido fluorídrico. / The purpose of this research is to evaluate the influence of conditioning time with hydrofluoric acid on the bond strength of a Y-TZP glazed ceramics and a resin cement. Ceramic pre-sintered Y-TZP blocks (IPS e.max® ZirCAD - Ivoclar Vivadent-) were cut to obtain 40 samples. Prior to sintering the blocks were smoothed with sandpaper water granulation #180, #600 and #1200. They were then randomly divided into four groups (n = 10), one control group was performed silicatization with Rocatec Soft (RS) and three vitrified test groups with different acid conditioning times surface: GS20s, GS60s and GS100s (application hydrofluoric acid for 20, 60 and 100 seconds respectively). For cementation was used a universal adhesive containing the MDP monomer in its composition (Single Bond Universal, 3M ESPE) and a dual resin cement (RelyX Ultimate, 3M ESPE). In each block was obtained two cement columns, totaling 20 samples per group. After thermocycling, the shear test was performed (EMIC, DL 2000), the maximum force to fracture was recorded and used to calculate the bond strength. Furthermore, the failure analysis was also performed with a esteriomicroscópio (Stemi 2000-C). An extra sample of each group had half of its surface treated to obtain images by profilometry and scanning electron microscopy (SEM), as well as conducting energy dispersive spectrometry (EDS). The Kruskal-Wallis test showed ap value of 0.001 and the Dunn test demonstrated differences only the RS group (22,10Mpa) for GS groups (GS20s: 8,10Mpa; GS60s: 10.49; GS100s: 7.53 ), but there was no difference among different GS groups. The profilometry and SEM images revealed an irregular pattern of glaze layout after conditioning with HF 10%. By profilometry it was possible to measure the thickness of the remaining glaze layer (GS20s: 5 ± 1μm; GS60s: 4 ± 1μm; GS100s: 3 ± 1μm). All failures were adhesive. And it concluded that the bond strength between Y-TZP glazed pottery and a resin cement with MDP is not influenced by different conditioning times with hydrofluoric acid.

The present work was to study the role of ladle glaze as apotential supplier of inclusions to the steel melt during theladle refining process. In this study, the total number ofinclusions at the beginning and at the end of the ladletreatment process was found to be increasing with ladle age,which is the number of heats, the ladle being used. Asubstantial increase in inclusion population was noticed aftera certain ladle age. Totally four types of inclusions named as; type-1 (MgO),type-2 (spinel), type-3 (an oxide solution) and type-4 (spinelin the center surrounded by the oxide solution of type-3) wereobserved in the beginning of the ladle refining process.Thermodynamic calculation revealed that the type-3 and type-4inclusions were generated by the reactions between EAF slag andladle glaze. Even a part of inclusions of type-2 (spinel phase)could be formed by these reactions. Three types of inclusionswere found before casting, viz. type-5 (oxide solution with lowcontents of MgO and SiO2), type-6 (small MgO islands embeddedin an oxide solution) and type-7 (spinel in the centersurrounded by the oxide solution of type-5). Inclusions of bothtype-5 and type-7 were the products of the reaction betweeninclusions of type-2 and the liquid metal. On the other hand,the occurrence of pieces of MgO having sharp edges in the oxidesolution suggested that the type-6 inclusions were generated bythe ladle glaze. A preliminary examination on the possibility of inclusionseparation by bubble floatation, experiments using cold modelswere also carried out. De-ionised water and silicon oil wereused as the bulk phase. Charcoal particles of different sizeranges were employed as the dispersed phase. The examination ofcharcoal-water-gas system indicated that the positivefloatation coefficient is not a sufficient condition for theinclusion separation. The experimental results were found to bein contradiction with the prediction of a typical model thatconsiders interfacial energies. The omitting of the drag forcewas believed to be the reason causing the failure of the modelprediction in the charcoal-water-gas system. The failure of themodel prediction suggested a need of a new model taking intoaccount interfacial energies, drag force, buoyancy force andgravity force. <b>Key words:</b>oxide inclusions, ladle metallurgy, ladleglaze, inclusion population, ladle age, interfacial tension,inclusion separation / NR 20140805

Glaze damage to canopy trees, gap size and seedling regeneration was surveyed relating to site topographic features after a major glaze storm at Fishburn Forest in the central Appalachian mountain region. The survey sites were stratified according to aspect and landform, and sample plots were randomly assigned to each topographic category. The canopy trees in the plots were tallied and their damage was visually classified. The results demonstrated that different species had different susceptibilities to glaze damage and susceptibility of species varied as topography changed. Virginia pine was the most susceptible species. In general, trees had the greatest damage on steep slopes and eastern aspects, and least damage on toe-slopes. Some species varied greatly in their susceptibility to glaze damage across the topographic categories, such as red maple, while some species varied little, like blackgum. Basal area was reduced 6% and varied due to species and topography. Where glaze damage was severe, gaps in the forest canopy were created. Gap sizes and the effects of gap size and topography on seedling regeneration within gaps caused by glaze damage were assessed. Seedlings were tallied by species and height in microplots within each sample plot and in the nearest gap, where gap size was measured. Gap size varied from 14,000 m2 to less than 20 m2. Average gap size was 255 m2. Canopy tree damage, forest type and topography were the most important factors affecting gap size. Gaps tended to be larger on steep backslopes. Common seedling species in both gaps and understory were sassafras, serviceberry and red maple. Disturbance affected both seedling height and density, as did topography. However gap size had effect only on seedling height. The future forest in this area is unlikely to change significantly, as species composition of seedlings was largely unaffected by the glaze storm damage. / Master of Science

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18277号 / 工博第3869号 / 新制||工||1593(附属図書館) / 31135 / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 松原 英一郎, 教授 杉村 博之, 教授 邑瀬 邦明 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Silicon nitride (Si₃N₄) has the potential for use in various high-performance applications. However, surface defects such as voids/pits are commonly present on as processed Si₃N₄. When subjected to external forces, fracture originates at such flaws. To reduce or eliminate surface flaws, machining operations are required which constitute a major proportion of production costs. In order to offer an inexpensive alternative to machining and also to enhance the room temperature flexural strength of as fired Si₃N₄, low expansion glaze coatings of lithium aluminosilicate (LAS) and magnesium aluminosilicate (MAS) compositions were developed. Homogeneous and crack-free glaze coatings were successfully formed on as processed Si₃N₄. This ensured formation of compressive surface stresses on the as fired Si₃N₄ which, in turn, led to the reduction of the effects of surface flaws. When compared to the uncoated as fired Si₃N₄, both the glaze coatings helped achieve greater flexural strength. Analyses of the two glazes indicated better strength for the MAS coating compared to the LAS. Wear tests revealed that the MAS glaze exhibited higher wear resistance than the LAS glaze. These differences were attributed to the ability of the magnesium aluminosilicate glaze to achieve greater surface smoothness and better adherence to the substrate than the lithium aluminosilicate. / Master of Science

Dans un turboréacteur civil, le contact aube/disque de la turbine basse pression est soumis à un cyclage thermomécanique dû aux dilatations et déplacements différentiels des pièces pendant les phases de vol. Ce cyclage implique des micro-mouvements alternés relatifs, c’est-à-dire du fretting, à l’interface aube/disque. Le fretting à l’étude ici concerne un contact céramique-métal, en vue de comprendre le comportement tribologique des futures aubes revêtues de céramique en remplacement des pièces métalliques traditionnelles. Dans un premier temps, différents revêtements sont comparés vis-à-vis de leur tenue à l’usure par fretting à la température de fonctionnement des pièces (700°C). L’alliage métallique du contrecorps est celui du clinquant protégeant le disque, à savoir l’alliage base cobalt HS25. Pour le contact HS25/céramique le plus prometteur, le taux d’usure très bas ainsi que le faible frottement observés sont associés à la formation d’une glaze layer. La glaze layer est un troisième corps formé à partir des débris d’usure qui apparaît dans des contacts frottant à haute température. Traditionnellement observée pour des contacts métal/métal, sa formation pour un contact métal/céramique est nouvelle. La glaze layer est alors étudiée en détail. D’un point de vue tribologique, on établit sa cinétique et ses conditions de formation en température et en fonction des paramètres tribologiques, afin de garantir une usure faible en conditions de vol. D’un point de vue morphologique, la glaze layer est caractérisée comme étant un matériau nanostructuré amorphe et cristallin, formé à partir de débris à la fois métalliques et oxydés. Enfin, la glaze layer nanostructurée est associée à un comportement mécanique ductile dans son domaine de stabilité, alors que les débris sont fragiles en conditions d’usure forte. La corrélation des angles d’étude de la glaze layer permet alors de connaître les modalités de sa formation, en vue d’anticiper la protection d’un contact vis-à-vis de l’usure grâce à la création d’une glaze layer. / In a civil turbojet motor, the blade/disk contact in the low pressure turbine undergoes thermomechanical cycling due to relative displacements between parts during the different flight phases. This cycling results in reciprocating micro-movements named “fretting” at the blade/disk interface. This study focuses on a ceramic versus metallic contact under fretting, aimed at describing the tribological behavior of developing ceramic-coated blades to replace phased-out metallic parts. Firstly, different ceramic coatings are compared regarding their wear resistance under fretting at in-flight temperature (700°C). The counterbody is the HS25 (cobalt-based alloy) protecting foil of the disk. The most favorable ceramic/metallic tribocouple evidences a very low wear rate as well as low friction that match the formation of a glaze layer. The glaze layer is a third body formed from wear debris in high temperature rubbed contacts. Such tribofilm has been commonly observed in metallic/metallic interfaces but its occurrence in a ceramic/metallic contact is new. Then the glaze layer is precisely characterized. Tribologically speaking, its kinetics and formation conditions are determined over temperature and tribological parameters, in order to ensure low wear under flight conditions. Morphologically, the glaze layer is a nanostructured amorphous and crystalline sintered from both metallic and oxidized worn debris. Finally, the nanostructured glaze layer is mechanically described as a ductile material in its stability domain, whereas debris from severe wear are brittle. The correlation of morphological, physico-chemical and mechanical studies enlighten the glaze layer formation criteria, with the aim of predicting glaze layer occurrence, hence wear protection for a given contact.

Applications of lead and strontium isotope analysis were made on archaeological materials from three different contexts in both the Old and New Worlds. These materials comprised pre-Hispanic glaze painted ceramics from Arizona, U.S.A., glass beads from late first millennium AD Igbo-Ukwu, Nigeria, and copper-based metals from early first millennium AD Kissi, Burkina Faso. All materials contain lead at major, minor, or trace concentrations, and lead isotope analysis was employed to determine a provenance for that lead. Strontium isotope analysis also was applied to glass beads from Igbo-Ukwu to determine provenance(s) for strontium found in the glass. Furthermore, application of elemental composition analysis was or had been employed on all samples for additional data comparisons within assemblages and with comparable archaeological materials.Results of these analyses determined, in most cases, regional provenance with high degrees of confidence for lead contained in the analyzed samples. Strontium and elemental composition analysis data also proved valuable in confirming the regional provenance of the raw glass used to produce the glass beads. Leads in the glaze paints from Arizona, which demonstrated a range of resources exploitation, were confidently restricted to a few regions for their procurement. Likewise leads in most glass beads from Igbo-Ukwu were confidently restricted to two main source regions, with a third strong contender also being identified. The elemental composition and strontium isotope data determined with confidence the production regions for the primary raw glasses used to make the glass beads. Finally, leads in copper-based metals from Burkina Faso also were restricted to a few regions, although some inconclusiveness in provenance determination was attributed to mixing of metals from difference sources.These results confirm the utility of heavy isotope analysis of archaeological materials for provenance determination. The combination of these data with elemental composition analyses further confirm the interpretive strength of combining independent but related sets of analytical data for exploring questions of archaeological provenance. With improvements in instrument technology and application in the past two decades, very high precision and high accuracy analyses can be made which eliminate some earlier concerns of heavy isotope applications in archaeology.

Lead and strontium isotopes are two powerful tracers that can be used to identify or constrain the provenance of a wide range of archaeological materials, but these two isotopic tracers have been rarely employed to infer the sources of artifacts in the southwestern USA. This dissertation contains four studies that demonstrate how these isotopic systems can address questions about the sources of three types of archaeological materials found in this region: turquoise, lead-based glaze-paints, and metals. The analysis of 116 samples of turquoise from 17 deposits in the southwestern USA reveals that lead and strontium isotopes are robust and sensitive tracers of turquoise at multiple scales. Isotopic variation among turquoise deposits correlates with broad regional differences in the geologic and tectonic setting of the rocks and mineral deposits which host turquoise mineralization. Many turquoise deposits also have unique isotopic signatures that will enable insights into ancient patterns of turquoise acquisition at regional and local levels. To show the utility of these tracers when applied to archaeological turquoise, I use lead and strontium isotopic measurements to establish that the Silver Bell Mountains are the likely source turquoise found at the Redtail site in the Tucson Basin, Arizona, USA. This dissertation also contains new, high-precision isotopic ratios of lead ores (galena and cerrusite) from four mining districts in New Mexico, including the Cerrillos Hills. All districts studied are possible sources of lead used by Pueblo IV communities to produce glaze paints. These new measurements, made by multiple-collector ICP-MS, define the isotopic composition of the ore deposits with greater precision and accuracy than achieved in previous studies, indicating an opportunity to improve interpretations about the provenance of lead in glaze paints. Lead isotopes are also found to be useful tools for identifying lead and copper metal associated with the 1540-1542 Vázquez de Coronado expedition. Lead shot and copper crossbow boltheads from two sites with archaeological evidence for the expedition's presence were determined to share similar or identical lead isotopic ratios. I propose this specific isotopic "fingerprint" can be used to identify other artifacts belonging to the expedition in the Southwest.

Artist Statement I am inspired by living in multiple environments and experiencing many regions of the United States. My imagery varies from references to landscapes to geometric abstractions of quilt patterns. My media consists of acrylics, oils, and pastels on supports including fabric, canvas, or paper. Mixed media allows me to add multiple layers in creating visual textures, depth, and energy to draw in my viewers. The media is glazed, flowed, dripped, sprayed, rolled, scraped, and scrubbed into my interpretations of natural elements and geometric patterns. My landscape paintings are of observations of nature, and I attempt to capture the power, motion, and energy of a moment in time. I paint from memory and purposely filter the images, simplifying and strengthening the focus of the captured moment. Rhythmic patterns in nature and seasonal light on the land are sources of my visual stimulation. My affinity for geometric shapes and patterns is sometimes expressed in abstract paintings of quilt patterns. I form rhythmic compositions and enhance the patterns with delicate brushwork and several glazed layers for added surface interest. These patterns of quilts are also reminiscent of landscapes from a bird’s eye view.