The adhesion and subsequent failure of a commercially available photocured resin applied to various ceramic substrates, used for electronics applications, has been investigated. The adhesive system was studied under both ambient and hostile, (water immersion at 50°C) conditions. The environmental stability of the system was investigated using two different mechanical tests, (simple butt-joints and a modified Boeing wedge test). In each case, the precise locus of failure was determined by a combination of surface analytical (XPS and ToF-SIMS) and microscopy techniques, (SEM). On the basis of these results, adhesion and failure mechanisms are proposed for the system. The presence of defects within the adhesive was found to initiate failure under ambient, (dry) conditions. Prolonged immersion in water, (for at least 2 weeks), was found to result in near-interfacial failure with a thin, (of the order of nanometres), overlayer of polymer remaining on the surface of the adherend. Subtle differences between this polymer overlayer and the bulk resin were observed. A model is proposed in which one of the minor resin components aggregates at the inorganic surface, creating a localised region which is extremely hydrophillic in nature. This makes the system particularly vulnerable to attack by water. In order to test this model, a reformulated batch of resin underwent the same environmental tests. The modified resin displayed a modest improvement in its ability to withstand hostile conditions, (prolonged immersion in water at 50°C) and the polymer residue remaining on the inorganic substrate was identical to that of the bulk polymer. This project has provided a unique opportunity to study the adhesion of a specific class of adhesives to bulk ceramic oxides, rather than to oxides of metals. One of the major benefits of which, was therefore the absence of any effects due to corrosion of the substrate. The project was also unusual in that it effectively went "full-circle", with the resin undergoing reformulation on the basis of the results obtained from the standard resin. The reformulated product was found to have superior wet adhesion, but poor mechanical properties.

The response of samples of unidirectional and cross-ply Nicalon fibre-reinforced calcium aluminosilicate (CAS) to a variety of thermal regimes has been examined using microscopy techniques and retained mechanical property measurements. The degree of matrix damage has been investigated by observation and measurement of cracking features and the results used in simple models in order to relate the occurrence of matrix cracking to stress distributions in the laminates. Thermal shock induced matrix crack damage was first seen to appear on the end faces of the unidirectional [0]16 laminate at a temperature differential of 400 °C and in the transverse plies, parallel to the longitudinal fibre direction, in the [0/90]3s cross-ply composite at a temperature differential of 350 °C. At more severe thermal shocks the next damage in both laminates was cracking in the matrix perpendicular to the fibre direction. The density of matrix cracking was seen to increase, initially, with increasing severity of thermal shock, but then to be less extensive at the highest temperature differentials (800 °C) used in this study. Crack density data for the unidirectional material at increasingly severe thermal shocks were compared with literature data for cracking under quasi-static loading using a simple thermal shock analysis incorporating a stress reduction factor. The effect of matrix cracking on retained mechanical properties has been examined by means of three-point flexure testing and values for Young's modulus, onset of non-linear behaviour and retained strength of the composites have been determined. Multiple thermal shock tests indicated that thermal treatment of previously cracked samples accelerated the rate of deterioration in the retained properties of the composite. It was proposed that the response of the samples to changes in the duration and severity of thermal treatments was consistent with interfacial modifications that have been reported to occur in this composite system at elevated temperatures. The suitability of applying a modified ACK model to predict critical temperature differentials for matrix cracking in the unidirectional laminate and longitudinal plies in the cross-ply composite has been tested. This approach combined applied thermal stresses, calculated using the simple thermal shock formula, with residual stresses, obtained from the model proposed by Powell et at. (1993). This method was found to be valid for the unidirectional material providing that some of the key parameters were determined independently. The use of a tunnelling crack model to predict thermal shock induced matrix cracking in the transverse plies of the cross-ply composite was less successful. This was partially attributed to the observed cracking patterns generated in the cross-ply material by flexure tests not conforming to those expected from stress calculations or reported from tensile tests.

This work is concerned with the processing and properties of chromiuni reinforced alumina ceramics with the Cr particles in both the micro- and nano-scale ranges. The influence of processing and microstructure on the mechanical properties has been studied. Al2O3-20vol%Cr micro-composites have been fabricated using both sintering and hot pressing techniques. Sintering environment has a crucial influence on the microstructural development of the pressureless sintered Al2O3-Cr composites. It was found that too little or too much oxygen is detrimental to Al2O3/Cr interfacial bonding. Attempts have been made to improve the Al2O3/Cr interfacial bonding by sintering in a graphite powder bed in order to control the oxygen partial pressure. The fracture toughness of the composite with strengthened interfaces was the highest of all the sintered samples. However, the improvement is limited by the brittle fracture of Cr. This may be caused by the high carbon content associated with Cr particles in the composite. The ductility of Cr was higher in the hot-pressed Al2O3-Cr samples. The possibility of further toughening Al2O3 by Cr80Ni20 and Cr20Ni80 alloys with higher ductility was explored. It was shown that 20 wt% of Ni present in the alloying phase did not change the ductility, but when the Ni content increased to 80 wt% the crystal structure changed to fc.c., giving a inherently ductile metal. However, the large thermal mismatch between Al2O3 and Ni/Cr alloys led to a high density of microcracks at the interfaces. The composites with different metallic phases had similar' fracture toughness values as measured by double cantilever beam testing. Among the Al2O3-CrxNi1-x composites, the highest fracture toughness, 5.8 MPa m1/2, was achieved by the hot pressed Al2O3-Cr composite. This value is comparable to values measured for other alumina-metal systems. The poor bonding at the alumina/metal interface is the main limitation to toughening in these composites. Thus, it may not be possible to have a strongly bonded and ductile reinforcement. The pressureless sintered Al2O3-Cr composites with different particle sizes showed different thermal shock behaviour. The composite with fine Cr particles exhibited a thermal shock behaviour which is typical of engineering ceramics, but with an improved critical temperature difference compared to sintered Al2O3. The specimen with a larger Cr particle size showed gradual strength degradation with increasing temperature difference. The increased fracture toughness, low initial strength and low Young's modulus of the composite are the primary reasons for the greater strength retention following quenching. Although Al2O3 was toughened by Cr and Cr/Ni alloys, the strength of the micro-composites was not improved as the metal particles acted as large flaws. In order to reduce the flaw size nano-composites were investigated. Al2O3-5vol% Cr nanocomposites were fabricated using a chemical method. Optimisation of the processing procedure led to a desirable microstructure and significantly increased strength. Among the nanocomposites, the highest strength, 736+/-29 MPa, was achieved by hot pressing at 1450°C. The improved strength of the nanocomposites is the consequence of the microstructure refinement by homogeneously distributed nano-sized Cr particles. The nanocomposites are slightly tougher than the parent Al2O3, although the values of the fracture toughness are lower than those for the 20vol% micro-scale particle toughened Al2O3. Thus, a small degree of toughening and significant strengthening have been achieved by Al2O3-Cr nanocomposites.

Submitted by Gabriela Freitas Ramos (gabrieladsfreitas@gmail.com) on 2018-08-08T01:12:25Z No. of bitstreams: 1 Gabriela F R.pdf: 2402001 bytes, checksum: 25f255b66f5d6d03803d8caedbfb8205 (MD5) / Approved for entry into archive by Silvana Alvarez null (silvana@ict.unesp.br) on 2018-08-16T15:30:22Z (GMT) No. of bitstreams: 1 Gabriela F R.pdf: 2402001 bytes, checksum: 25f255b66f5d6d03803d8caedbfb8205 (MD5) / Made available in DSpace on 2018-08-16T15:30:22Z (GMT). No. of bitstreams: 1 Gabriela F R.pdf: 2402001 bytes, checksum: 25f255b66f5d6d03803d8caedbfb8205 (MD5) Previous issue date: 2018-06-08 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O objetivo foi avaliar a probabilidade de falha de coroas de zircônia-porcelana com e sem infiltração de sílica (gradação) da zircônia, em disposição tradicional, graduada e bioinspirada, através da análise de Weibull e de elementos finitos pelo critério de Tensão Máxima Principal. Foram utilizados cem preparos anatômicos de primeiro molar superior (26) confeccionados em resina epóxi- Nema G10, que foram divididos em quatro grupos: Tradicional: infraestrutura em zircônia (Zircônia Convencional-Incoris ZI, Sirona, Brasil) e cobertura de porcelana (Cerâmica Feldspática-Cerec Blocs); Graduada: infraestrutura em zircônia infiltrada por sílica e cobertura de porcelana; Bioinspirada: infraestrutura em porcelana e cobertura com zircônia (Zircônia translúcida-Incoris TZI, Sirona, Brasil); e Bioinspirada Graduada: infraestrutura em porcelana e cobertura com zircônia infiltrada por sílica. A porção mais externa de todas as coroas foi revestida com uma camada glaze. A carga para fadiga deslizante foi de 100 N. Então os espécimes foram ciclados mecanicamente em um simulador de ciclos mastigatórios no qual uma ponta aplicadora fez 2.106 ciclos a uma frequência de 4 Hz. A cada 500.000 ciclos as coroas foram avaliadas quanto à presença de falhas (trincas, lascamentos ou descolamento entre porcelana e zircônia, fraturas catastróficas), em estereomicroscópio. Os tipos de falhas predominantes para as coroas Tradicional e Graduada foram delaminação e trincas, respectivamente. Os parâmetros de Weibull (beta e eta), com intervalo de confiança bilateral de 95% foram respectivamente: Tradicional - 1,29 e 0,23 E+07 ciclos; Graduada - 1,95 e 0,23 E+07 ciclos; Bioinspirada - 1,00 e 1,67 E+07 ciclos e Bioinspirada graduada - 1,00 1,67 E+07 ciclos. As coroas Tradicionais e Graduadas apresentaram maior susceptibilidade à falha por fadiga e as Bioinspiradas e Bioinspiradas graduadas não demonstraram susceptibilidade à fadiga. Ainda, através da Análise de elementos finitos, pôde-se verificar que as coroas bioinspiradas e bioinspiradas graduadas apresentaram a melhor distribuição de tensões tanto sobre a coroa quanto para a estrutura dentária. As diferentes configurações de restauração apresentaram diferentes probabilidades de falha após o ensaio de fadiga deslizante, sendo que as coroas Bioinspirada e Bioinspirada Graduada apresentam a menor probabilidade de falha e melhor distribuição de tensões, podendo ser consideradas restaurações mais duradouras em longo prazo. / The objective was to evaluate the failure probability of zirconia-porcelain crowns with and without silica infiltration (graded material) of the zirconia, using traditional, graded and bio-inspired design, through Weibull and finite element analysis by maximum principal stress. One hundred anatomical preparations of first upper molar were made of epoxy resin Nema G10 and divided into four groups: Traditional- zirconia (Conventional zirconia -Incoris ZI, Sirona, Brazil) and porcelain cover (Feldsphatic ceramic-Cerec Blocks); Graded- infrastructure in zirconia silica infiltrated and porcelain cover; Bioinspired- porcelain infrastructure and zirconia cover (Trasnlucent zirconia-Incoris TZI, Sirona, Brazil); and Graded Bioinspired- porcelain infrastructure and zirconia infiltrated by silica cover. The outermost portion of all crowns was coated with a glaze layer. The load for sliding fatigue was 100 N. Then the specimens were mechanically cycled in a masticatory cycle simulator for 2 x 106 cycles at 4 Hz of frequency. Every 500k cycles the crowns were evaluated in stereomicroscope for failures presence (cracks, chipping or detachment between porcelain and zirconia, or catastrophic fractures). The predominant failure types for the Traditional and Graded crowns were delamination and cracking, respectively. The Weibull parameters (beta and eta) with 95% bilateral confidence interval were respectively: Traditional - 1.29 and 0.23 E + 07 cycles; Graded - 1.95 and 0.23 E + 07 cycles; Bioinspired - 1,00 and 1,67 E + 07 cycles and Graded Bioinspired - 1,00 1,67 E + 07 cycles. The Traditional and Graded crowns presented greater susceptibility to failure due to fatigue and the Bioinspired and Graded Bioinspired crowns showed no susceptibility to fatigue. Also, through the finite elements analysis, it was verified that the Bioinspired and Graded Bioinspired crowns presented the best stress distribution on both crown and dental structure. The different restoration configurations presented different failure probabilities after the sliding fatigue test. Bioinspired and Graded Bioinspired crowns had the lowest failure probability and better stress distribution, which may be considered lasting restorations in the long term. / 2015/110013

Orientador: Eudes Borges de Araújo / Banca: Newton Luiz Dias Filho / Banca: Marcelo Rubens Barsi Andreeta / Banca: Fábio Simões de Vicente / Banca: Emerson Marcelo Girotto / O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp / Resumo: Materiais ferroelétricos do sistema Pb('Mg IND. 1/3'Nb IND.2/3')'O IND. 3'-xPbTi'O IND. 3'(PMN-xPT), possuem potencial efetivo para aplicações em dispositivos eletromecânicos, tais como, transdutores e sensores. Porém, a obtenção de cerâmica de PMN-xPT livre de fase pirocloro (paraelétrica) exige rigoroso controle durante a síntese. Neste trabalho, as condições destinadas a supressão de fase pirocloro em cerâmicas de PMN e PMN-xPT (para x = 0,33, 0,35 e 0,37), foram estudadas a partir de uma nova rota de preparação em função do excesso de MgO e PbO. Paralelamente, cerâmicas de PMN e PMN-PT obtidas pela rota convencional de mistura de óxidos, foram preparadas e os resultados comparados. Os resultados obtidos revelaram valores mais elevados de permissividade para as cerâmicas preparadas pela nova rota. Os valores da polarização remanescente das cerâmicas de PMN-xPT mostraram-se comparáveis com monocristais. Medidas dielétricas realizadas nas cerâmicas de PMN-xPT apontam um significante aumento nos valores de permissividade dielétrica em função do aumento do campo elétrico AC. Condutividade AC e impedância nas cerâmicas de PMN-xT foram estudadaas na região de frequência de 100Hz-1MHz e temperatura 325 - 50ºC. Uma anomalia no espectro de condutividade foi observada para todas as composições, próximo ao ponto de transição de fase ferroelétrica-paraelétrica. / Abstract: Ferroelectric materials of Pb('Mg IND. 1/3'Nb IND.2/3')'O IND. 3'-xPbTi'O IND. 3'(PMN-xPT) system have effective potential for applications in electromechanical devices such as transducers and sensors. However, to obtain free pyrochlore phase (paraelectric) ceramics of PMN-xPT requires control during the synthesis. In this work, the conditions for the removal of pyrochlore phase of PMN and PMN-xPT (for x = 0.33, 0,35 and 0.37) ceramics, were studied using a new route of preparation with the excess MgO and PbO. The obtained results were compared with the ceramics of PMN and PMN-xPT prepared by the conventional route of mixed oxides. The results showed higher values of permittivity for the ceramics prepared by the new route. The remnant polarization values of PMN-xPT ceramics shown to be comparable with single crystal. Dielectric of PMN-xPT ceramics showed a significant increase in the values of dielectric permittivity due to the increase of the AC electric field. Conductivity AC and impedance of PMN-xPT ceramics were studied in the frequency range of 100Hz - 1MHz and temperature 325 - 50ºC. An anomaly was observed in the spectrum of conductivity for all the compositions, which is close to the point of ferroelectric-paraelectric phase transition. / Doutor

This work is all about things. It is about the role that those things play in the human experience, and what they offer to us as archaeologists, whose job is to provide a glimpse into the lives of past peoples. I discuss the things of the past from the theoretical stance of materiality, which assures us that the past is accessible despite the fragmentary nature of its physical remains. This is so because the physical world - objects, landscapes, and space - are imbued with meaning through our interactions with and experiences of them, be they overt and intentional or subconscious and in the background of our active lives. Repeated engagement with the physical world creates habits, memories, and histories and inscribes the social processes that created them upon the tangible world in ways that allow us to interpret the lives of the people with whom we have no direct interaction or accounts. I use this theory to explore the southern Illinois site of Kincaid Mounds during the latter portion of its Mississippian period occupation, with a focus on how community was constructed and maintained within and through time. I do so using evidence from the non-discursive aspects of ceramic and architectural manufacture under the assumption that the methods of producing these items are habituated and thus reveal communities of learning. I consider contextual evidence to determine what other factors may have been at play in the production of these goods. With statistical analyses, I explore the variation in the way things were made between several spatially discrete neighborhoods at Kincaid Mounds, and discuss those results in terms of the making and manipulation or maintenance of community at this pre-Columbian center, followed by a narrative history of the Middle and Late Kincaid phases. I contrast these finds with those of communities within two other Middle Mississippian regions, Greater Cahokia and the Central Illinois River Valley, in order to discuss the variable processes that led diverse and unique communities to participate in a much broader, imagined Mississippian community.

Collective memories and how they are enacted through sensual experience of the material world play a key role in maintaining group identities. Material creations like art or social activities such as sports incorporate the social ideals of both the past as well as present; these creations can transform feelings of personhood into socialized objects. This thesis examines some of the creative expressions found within Oklahoma Choctaw revitalization practices to better understand how people maintain cultural sensory embodiments after they have experienced extreme social dislocation. Through the examination of the senses from an ethnographic approach a researcher can possibly identify those areas of culture that become embodied over time. I will be examining previously written research, oral histories pertaining to the Choctaw origin, and key material expressions of Choctaw identity alongside the contemporary practices associated with the current Choctaw revitalization efforts in Oklahoma.

This research aims to understand whether and how ritual manifests in ceramic objects dating to the Late Mississippian Period (ca. late 1200s A.D. to A.D. 1500) in southern Illinois. The study focuses on ritual phenomena that occurred at two village sites: Millstone Bluff (11Pp3) and Dillow’s Ridge (11U635). Millstone Bluff has been interpreted as a site of public ritual and unusual symbolic importance evidenced by its general location and topography, spatial organization, and distinctive rock art. Though Dillow’s Ridge was the locale for an inordinate level of lithic tool production, in other ways the site is understood to be typical of Mississippian villages for this region and time and unlikely to have accommodated large-scale public ritual activity. Through the analysis and comparison of ceramics from each site, this research seeks to identify the ceramic correlates of public ritual activity for this region and time. Statistical results suggest very little differentiation between the ceramic assemblages, suggesting the ritual activities that took place at either site may not have been substantially different from one another. Alternatively, the lack of differentiation may indicate ceramics do not play an active role in large-scale public ritual activity in this context.

The societies of Mahan and Baekje occupied Korea’s southwestern region from approximately first through seventh centuries CE, but their origins, geographical extent, and internal cultural variations have been poorly understood from archaeological and historical data. Baekje is considered the first state to develop in the region, but Mahan has proven more difficult to categorize. This dissertation explores the social structures related to craft production in both societies through geochemical analysis of pottery remains from Mahan and Baekje sites. First, an overview of existing research on Mahan and Baekje is provided, followed by a discussion of the state concept in archaeology and more recent theories regarding heterarchy in complex societies. The methodologies deployed in this study include stylistic analysis, Instrumental Neutron Activation Analysis (INAA), and thin-section petrography on pottery fragments from Mahan and Baekje sites. The eight sites included in this study cover a wide range of the Mahan/Baekje region, including settlements in modern Seoul, Incheon, Wonju, Jincheon County, and Gwangju. Geochemical data from INAA which are subjected to multiple statistical analyses to detect patterns of chemistry related to clay sources and processing methods, revealing information on pottery manufacture and exchange. This dissertation finds that the production and consumption patterns of pottery in the Baekje kingdom bear a strong resemblance to those in Mahan, differing primarily in scale. Although Baekje is often studied in terms of its relationship with China, the findings presented here suggest a deep cultural relationship between Mahan and Baekje. Mahan’s role in the history of this region is currently undergoing reassessment, making this work part of mounting evidence of Mahan’s contribution to later Korean civilizations. Looking at Baekje as a complex society with the expectation of both hierarchical and heterarchical organization reveals a political economy with multiple nodes of power and control, resulting from local people making decisions in a locally situated cultural context. / 10000-01-01

Orientador: Denise Pedrini / Coorientador: Alberto Carlos Botazzo Delbem / Banca: Douglas Roberto Monteiro / Banca: Andréa de Castro Bastos / Resumo: O objetivo deste estudo foi analisar as características de superfície da cerâmica vítrea de dissilicato de lítio com diferentes acabamentos de superfície (glaze e polimento manual mecânico) submetidas a soluções ácidas (ácido cítrico e ácido fosfórico) e armazenadas em água ou saliva humana. As superfícies foram analisadas utilizando a energia livre de superfície, rugosidade, dureza e microscopia eletrônica de varredura. Foram utilizadas pastilhas de cerâmica vítrea de dissilicato de lítio, do sistema prensado, dos quais foram obtidas amostras com 6 mm x 4 mm x 2mm (n=120). Os grupos experimentais foram divididos de acordo com o acabamento das cerâmicas (polida ou glaze), desafio (água, ácido cítrico e ácido fosfórico) e meio de armazenamento (água deionizada ou saliva humana). Foram realizados ciclos de 21 dias onde as cerâmicas permaneciam 4 horas na solução de desafio e 20 horas no meio de armazenamento, sendo renovados diariamente. Os dados foram submetidos a ANOVA a 3 critérios seguidos pelo teste de Student-Newman-Keuls. Houve rugosidade maior com o acabamento glaze (p<0,001) e o desafio com ácido fosfórico levou a menor rugosidade (p<0,003). A dureza foi maior para as cerâmicas com glaze e menor quando submetida ao ácido cítrico (p=0,536). A superfície da cerâmica glazeada apresentou maior valor de energia livre (p<0,007), porém nos desafios ácidos armazenados em saliva, o componente doador de elétrons em ambos os desafios, apresentaram menores valores (p=0,148). Concl... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Abstrac : The objective of this study was to analyze the surface characteristics of vitreous ceramics of lithium disilicate with different surface finishes (glaze and mechanical manual polishing) submitted to acid solutions (citric acid and phosphoric acid) and stor ed in human water or saliva. The surfaces were analyzed using surface free energy, roughness, hardness and scanning electron microscopy. Lithium disilicate vitreous ceramic tablets were used, from which the samples were obtained with 6 mm x 4 mm x 2 mm (n= 120). The experimental groups were divided according to the finishing of the ceramics (polished or glaze), challenge (water, citric acid and phosphoric acid) and storage medium ( deionized water or human saliva). Twenty - one day cycles were performed where t he ceramics remained 4 hours in the challenge solution and 20 hours in the storage medium, being renewed daily. Data were submitted to ANOVA at 3 criteria followed by the Student - Newman - Keuls test. T here was greater rou ghness with the glaze finish (p <0.001 ) and the challenge with phosphoric acid led to the least roughness (p <0.00 3 ). Hardness was higher for ceramics with glaze and lower wh en submitted to citric acid (p = 0.536). Th e glaze ceramic surface presen ted higher free energy value (p <0.007), but in the acidic challenges stored in saliva, the electron donor component in both challeng es presented lower values (p = 0.148). It was con cluded that the glazed ceramics presented higher rough... (Complete abstract click electronic access below) / Mestre