Made available in DSpace on 2014-06-11T19:35:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-04-26Bitstream added on 2014-06-13T20:46:55Z : No. of bitstreams: 1 felix_aa_dr_bauru.pdf: 2060011 bytes, checksum: 4a5c68d1fc6a532384cd2520a68edde4 (MD5) / Neste trabalho pastilhas cerâmicas de CaCu3Ti4O12 (CCTO) foram produzidas pelo método de reação por estado sólido onde estudos por difração de raios-X mostraram que as amostras policristalinas são monofásicas dependendo da pressão parcial de oxigênio. Estudos por microscopia eletrônica de varredura e fotoluminiscência indicam que o processo de crescimento de grão e densificação das amostras e a formação de vacâncias de oxigênio estão diretamente relacionados a concentração de oxigênio durante o processo de sinterização. As amostras foram caracterizadas por medidas elétricas dc em função da temperatura, que associada a teoria de semicondutores, provaram que as barreiras de potencial no CCTO são mais influenciadas pela temperatura do que pelo campo elétrico, ou seja, são barreiras do tipo Schottky. Um modelo de barreira e os mecanismos de formação foram propostos para descrever a formação da barreira de potencial no CCTO. Medidas de corrente-tensão cíclicas mostraram que o efeito de comutação resistiva no CCTO está diretamente relacionado a efeitos de contorno de grão e efeito Joule. As propriedades de transporte elétrico em filmes finos de CCTO foram investigadas para os efeitos de comutação resistiva, retificação elétrica e aplicação em sensores de gás. Filmes monofásicos foram produzidos pelo Método dos Precursores Poliméricos (MPP) em diferentes tipos de substratos. Filmes produzidos em substratos de LNO/Si apresentam curvas de corrente-tensão simétricas, indicando contatos ôhmicos, enquanto os filmes depositados sobre substratos de Pt/Si têm um comportamento altamente assimétrico nestas curvas, o qual está relacionada com a formação de um junção metal-semicondutor na interface CCTO/Pt. Os resultados indicam que a formação deste tipo de contato reforça o efeito de comutação resistiva neste material... / CaCu3Ti4O12 (CCTO) pellets were produced by solid state reaction method and X-ray diffractograms showed that single phase polycrystalline samples were obtained. Studies by scanning electron microscopy and photoluminescence indicate that the process of growth and densification of the samples and formation of oxygen vacancies, respectively, are directly related to oxygen concentration during sinterization process. The samples were electrically characterized by dc measurements a function of temperature, which associated to semiconductor theory, showed that CCTO barriers are more influenced by temperature than by electric filed, i.e., Schottky barriers. A model and the mechanism for barrier formation have been proposed to describe the CCTO potential barrier. Electric transport properties of CaCu3Ti4O12 (CCTO) thin films were investigated for resistive switching, rectifying and gas sensor applications. Single phase CCTO thin films were produced by Polymeric Precursor Method (PPM) on different substrates. Cyclic current-voltage measurements showed that resistive switching effects in CCTO is directly related to the grain boundary and Joule effects. Films produced on LNO/Si substrates have symmetrical non-ohmic current voltage characteristics, forming ohmic contact, while films deposited on Pt/Si substrates have a highly asymmetrical non-ohmic behavior which is related to a metal-semiconductor (MS) junction formed at the CCTO/Pt interface. Results confirm that CCTO has a resistive switching response which is enhanced by Schottky contacts. Sensor response tests revealed that CCTO films are sensitive to oxygen gas and exhibit n-type conductivity. These results demonstrate the versatility of CCTO thin film prepared by the PPM method for gas atmosphere or bias dependent resistance applications depending n filme configuration

The mid 2nd millennium BC in Mesopotamia is defined by the ebb and flow of power politics, with the Old Babylonian state, the Kassite state, and the kings of the Sealand, vying for power over the southern alluvial plains. Although widespread sociopolitical instability is acknowledged during this period, the scarcity of archaeological and textual evidence has often seen it labelled as a “Dark Age” in Mesopotamian history. Recent excavation at the site of Tell Khaiber (2013-2017), southern Iraq, provides the first material to be reliably associated with this Dark Age, and more specifically to the period of Sealand control. This thesis attends to the pottery assemblage from Tell Khaiber as a means of assessing the everyday lives of a community adapting to this upheaval. This research examines the pottery assemblage on multiple analytical levels, synthesising a vast body of textual, archaeological, scientific, and material data. Firstly, a comprehensive Sealand period typology is subjected to stylistic comparison on both a local and (inter)regional level, in order to assess the shifting networks of interaction at play during this period. The thesis then turns to a detailed analysis of pottery production, focusing particularly on production techniques, the standardisation of the product, and the scale of the industry. Finally, various pottery use-contexts are established, and the distribution of these activities are mapped onto Tell Khaiber’s public building. Since these multi-faceted pottery engagements articulated with the (re)production of Sealand society and economy, this research provides unparalleled insights into the everyday workings of this poorly understood state system.

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.

Uma das etapas mais críticas no processo de conformação de uma peça cerâmica é a etapa de secagem. Nela podem aparecer defeitos como trincas e empenamentos na peça. Uma forma de minimizar esses defeitos é diminuir a quantidade de água utilizada na formação do corpo cerâmico. No entanto esta ação interfere diretamente na etapa de conformação. Este trabalho tem como objetivo avaliar o comportamento mecânico de peças cerâmicas à verde, para que se possa entender a interação de misturas argila-ar-água, e como o corpo cerâmico úmido se comporta mediante a adição de pó de rocha e surfactante. Para isso foram realizados tanto ensaios de compressão uniaxial quanto de fluência e relaxação. Através das curvas tensão vs. deformação geradas no ensaio de compressão foi possível avaliar a variação do comportamento plástico da argila mediante a variação do teor de umidade e da introdução de pó de rocha. Foram produzidas curvas de trabalhabilidade através do produto das tensões limites de escoamento e das deformações máximas. Os ensaios mostraram que o pó de rocha foi capaz de reduzir a umidade de trabalhabilidade máxima de 18,0% para 13,7%. A variação das densidades de empacotamento do corpo verde em função da umidade de conformação se correlaciona diretamente com o comportamento à compressão, especificamente com a tensão limite de escoamento. Isso tornou possível quantificar a coesão dos corpos cerâmicos produzidos. A adição de pó de rocha na argila diminuiu a coesão do corpo cerâmico verde. Foi possível identificar a existência de diferentes estados de hidratação/saturação do corpo verde: o estado pendular, funicular com porosidade aberta, funicular com porosidade fechada e capilar. Os ensaios de fluência e relaxação mostraram que a argila apresenta um comportamento viscoelástico, independentemente do teor de água do corpo verde. Também foi mostrado que o uso de 1, 5% em massa de surfactante em relação a massa de argila pode reduzir o consumo de água de processamento sem afetar seu comportamento mecânico, pois é capaz de fazer com que uma argila com 18,3% de umidade flua da mesma forma que uma argila com aproximadamente 24,5% de umidade. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2016-08-29T13:36:45Z No. of bitstreams: 1 Dissertacao Licia da Silva Alves Schiavo.pdf: 4296423 bytes, checksum: 240b028f046bdd959b5e54aaeee6ae63 (MD5) / Made available in DSpace on 2016-08-29T13:36:45Z (GMT). No. of bitstreams: 1 Dissertacao Licia da Silva Alves Schiavo.pdf: 4296423 bytes, checksum: 240b028f046bdd959b5e54aaeee6ae63 (MD5) Previous issue date: 2016-08-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES. / Drying is one of the most critical forming steps in the ceramic tile production. Usually defects such as cracks and surface distortion are produced in this processing step. One way to minimize these defects is to reduce the amount of water used to shape the ceramic body. However this water reduction directly interferes in the forming process. This work aims to evaluate the mechanical behavior of ceramic green bodies in order to understand the interactions of clay-air-water mixtures, and how it behaves when rock powder and surfactant are added. For that, uniaxial compression and creep and relaxation tests were performed. They allowed, through the stress-strain curve, to assess the clay plastic response to the variation of moisture contents and rock powder addition. Workability curves were produced by the product of the yield stress and maximum deformation. The tests showed that the rock powder was able to reduce moisture of maximum workability of 18.0% to 13.7%. The green body packing density variation as a function of the forming moisture directly correlates with its compressive behavior, specifically with the yield stress. It turns possible to quantify the cohesion of the produced ceramic bodies. The addition of rock powder to the clay decreased the cohesion of the ceramic green body. The existence of different green body hydration/saturation states were identified namely the pendulous, funicular with open porosity, funicular with closed porosity and capillary states. Creep and relaxation tests were performed which showed that the clay body has a viscoelastic behavior, i.e. deformation is a function of time, independently of the green body water content. It was also shown that the use of surfactant can reduces the processing water consumption without affecting its mechanical behavior, because it can cause a clay with 18.3% moisture to flow in the same way that a clay with about 24.5% moisture.

Orientador: José Arana Varela / Banca: Miguel Angel Ramirez Gil / Banca: Paulo Noronha Lisboa Filho / Banca: Paulo Roberto Bueno / Banca: Sidnei Antonio Pianaro / 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: Neste trabalho pastilhas cerâmicas de CaCu3Ti4O12 (CCTO) foram produzidas pelo método de reação por estado sólido onde estudos por difração de raios-X mostraram que as amostras policristalinas são monofásicas dependendo da pressão parcial de oxigênio. Estudos por microscopia eletrônica de varredura e fotoluminiscência indicam que o processo de crescimento de grão e densificação das amostras e a formação de vacâncias de oxigênio estão diretamente relacionados a concentração de oxigênio durante o processo de sinterização. As amostras foram caracterizadas por medidas elétricas dc em função da temperatura, que associada a teoria de semicondutores, provaram que as barreiras de potencial no CCTO são mais influenciadas pela temperatura do que pelo campo elétrico, ou seja, são barreiras do tipo Schottky. Um modelo de barreira e os mecanismos de formação foram propostos para descrever a formação da barreira de potencial no CCTO. Medidas de corrente-tensão cíclicas mostraram que o efeito de comutação resistiva no CCTO está diretamente relacionado a efeitos de contorno de grão e efeito Joule. As propriedades de transporte elétrico em filmes finos de CCTO foram investigadas para os efeitos de comutação resistiva, retificação elétrica e aplicação em sensores de gás. Filmes monofásicos foram produzidos pelo Método dos Precursores Poliméricos (MPP) em diferentes tipos de substratos. Filmes produzidos em substratos de LNO/Si apresentam curvas de corrente-tensão simétricas, indicando contatos ôhmicos, enquanto os filmes depositados sobre substratos de Pt/Si têm um comportamento altamente assimétrico nestas curvas, o qual está relacionada com a formação de um junção metal-semicondutor na interface CCTO/Pt. Os resultados indicam que a formação deste tipo de contato reforça o efeito de comutação resistiva neste material... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: CaCu3Ti4O12 (CCTO) pellets were produced by solid state reaction method and X-ray diffractograms showed that single phase polycrystalline samples were obtained. Studies by scanning electron microscopy and photoluminescence indicate that the process of growth and densification of the samples and formation of oxygen vacancies, respectively, are directly related to oxygen concentration during sinterization process. The samples were electrically characterized by dc measurements a function of temperature, which associated to semiconductor theory, showed that CCTO barriers are more influenced by temperature than by electric filed, i.e., Schottky barriers. A model and the mechanism for barrier formation have been proposed to describe the CCTO potential barrier. Electric transport properties of CaCu3Ti4O12 (CCTO) thin films were investigated for resistive switching, rectifying and gas sensor applications. Single phase CCTO thin films were produced by Polymeric Precursor Method (PPM) on different substrates. Cyclic current-voltage measurements showed that resistive switching effects in CCTO is directly related to the grain boundary and Joule effects. Films produced on LNO/Si substrates have symmetrical non-ohmic current voltage characteristics, forming ohmic contact, while films deposited on Pt/Si substrates have a highly asymmetrical non-ohmic behavior which is related to a metal-semiconductor (MS) junction formed at the CCTO/Pt interface. Results confirm that CCTO has a resistive switching response which is enhanced by Schottky contacts. Sensor response tests revealed that CCTO films are sensitive to oxygen gas and exhibit n-type conductivity. These results demonstrate the versatility of CCTO thin film prepared by the PPM method for gas atmosphere or bias dependent resistance applications depending n filme configuration / Doutor

Uma das etapas mais críticas no processo de conformação de uma peça cerâmica é a etapa de secagem. Nela podem aparecer defeitos como trincas e empenamentos na peça. Uma forma de minimizar esses defeitos é diminuir a quantidade de água utilizada na formação do corpo cerâmico. No entanto esta ação interfere diretamente na etapa de conformação. Este trabalho tem como objetivo avaliar o comportamento mecânico de peças cerâmicas à verde, para que se possa entender a interação de misturas argila-ar-água, e como o corpo cerâmico úmido se comporta mediante a adição de pó de rocha e surfactante. Para isso foram realizados tanto ensaios de compressão uniaxial quanto de fluência e relaxação. Através das curvas tensão vs. deformação geradas no ensaio de compressão foi possível avaliar a variação do comportamento plástico da argila mediante a variação do teor de umidade e da introdução de pó de rocha. Foram produzidas curvas de trabalhabilidade através do produto das tensões limites de escoamento e das deformações máximas. Os ensaios mostraram que o pó de rocha foi capaz de reduzir a umidade de trabalhabilidade máxima de 18,0% para 13,7%. A variação das densidades de empacotamento do corpo verde em função da umidade de conformação se correlaciona diretamente com o comportamento à compressão, especificamente com a tensão limite de escoamento. Isso tornou possível quantificar a coesão dos corpos cerâmicos produzidos. A adição de pó de rocha na argila diminuiu a coesão do corpo cerâmico verde. Foi possível identificar a existência de diferentes estados de hidratação/saturação do corpo verde: o estado pendular, funicular com porosidade aberta, funicular com porosidade fechada e capilar. Os ensaios de fluência e relaxação mostraram que a argila apresenta um comportamento viscoelástico, independentemente do teor de água do corpo verde. Também foi mostrado que o uso de 1, 5% em massa de surfactante em relação a massa de argila pode reduzir o consumo de água de processamento sem afetar seu comportamento mecânico, pois é capaz de fazer com que uma argila com 18,3% de umidade flua da mesma forma que uma argila com aproximadamente 24,5% de umidade. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES. / Drying is one of the most critical forming steps in the ceramic tile production. Usually defects such as cracks and surface distortion are produced in this processing step. One way to minimize these defects is to reduce the amount of water used to shape the ceramic body. However this water reduction directly interferes in the forming process. This work aims to evaluate the mechanical behavior of ceramic green bodies in order to understand the interactions of clay-air-water mixtures, and how it behaves when rock powder and surfactant are added. For that, uniaxial compression and creep and relaxation tests were performed. They allowed, through the stress-strain curve, to assess the clay plastic response to the variation of moisture contents and rock powder addition. Workability curves were produced by the product of the yield stress and maximum deformation. The tests showed that the rock powder was able to reduce moisture of maximum workability of 18.0% to 13.7%. The green body packing density variation as a function of the forming moisture directly correlates with its compressive behavior, specifically with the yield stress. It turns possible to quantify the cohesion of the produced ceramic bodies. The addition of rock powder to the clay decreased the cohesion of the ceramic green body. The existence of different green body hydration/saturation states were identified namely the pendulous, funicular with open porosity, funicular with closed porosity and capillary states. Creep and relaxation tests were performed which showed that the clay body has a viscoelastic behavior, i.e. deformation is a function of time, independently of the green body water content. It was also shown that the use of surfactant can reduces the processing water consumption without affecting its mechanical behavior, because it can cause a clay with 18.3% moisture to flow in the same way that a clay with about 24.5% moisture.

No description available.

This study examines the emergence of status differentiation during the Early and Middle Preclassic periods (1200/1100-300 BC) in the Maya lowlands through the examination of pottery and its status as a valued object. Through macroscopic, contextual, and compositional analyses of previously excavated pottery from four sites in the Petén lakes region of Guatemala—Nixtun-Ch’ich', Tayasal, Ixlú, Zacpetén—this project focuses on the ways value was encoded into vessels. Unlike later polychrome wares, Middle Preclassic pottery displayed little status-marking decoration, suggesting that the "object-value" of pottery was based on function and use ("use-value") rather than attributes related to production (“production-value”). By integrating production attributes with contexts of recovery, this project explores the ways early pottery was produced, used, and deposited at a time when societal differentiation became identifiable archaeologically through the appearance of substantial architectural endeavors and access to exotic goods. This connects to the larger anthropological question of how emerging status differentiation in communities impacts the notion of value in material culture and the process through which prestige goods developed in complex societies.Data generated from this study of 27,870 sherds provide multiple lines of evidence for ways that value was encoded on early Maya pottery. To examine factors relating to production-value, macroscopic (type-variety analysis and modal analysis) and compositional (petrographic analysis of thin sections, INAA, and LA-ICP-MS) analytical methods are used to assess the presence of production-value markers. Attributes ranging from paste composition to surface decoration reveal the diversity in valuation at the beginning of vessel use-life. Use-value is examined through a contextual analysis of pottery and its deposition, with primary focus on the extensive excavations at Mound ZZ1 at Nixtun-Ch'ich'. On the basis of the findings, I conclude that the construction of value and prestige was carried out in many ways by emerging elites in the western Petén lakes area, but it appears that pottery’s role in this was not prescriptive, but supportive.Beyond investigating how early Maya pottery was valued, this study demonstrates the importance of an integrated methodological approach to artifact analysis that considers both contextual and physical attributes. This provides a way to operationalize a concept like object value, which can be difficult to access through the archaeological record. The complementary data presented here reflect the myriad ways in which object-value is affected by both production choices and social behaviors.

The strategic orientation of Portuguese firms in the porcelain industry is examined empirically. In the process, the effective use of traditional generic strategies as opposed to emerging strategies is compared. Special attention is devoted to the utility of classical Porter's generic strategies in comparison to time-based differentiation strategy. The study concludes that different variations of the classical differentiation strategy, which includes time-based differentiation, appear to be more effective than cost leadership or mixed generic strategies.

No description available.