Dissertations / Theses: 'Materials'

1

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.

Full text

Abstract:

Submitted by Cátia Araújo (catia.araujo@unipampa.edu.br) on 2017-01-25T12:34:29Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Desenvolvimento de materiais cerâmicos refratários com adição da sílica residual proveniente da queima da casca de arroz.pdf: 10705111 bytes, checksum: f3dc853aa0f1b672236697852c098384 (MD5)
Approved for entry into archive by Cátia Araújo (catia.araujo@unipampa.edu.br) on 2017-01-25T12:37:45Z (GMT) No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Desenvolvimento de materiais cerâmicos refratários com adição da sílica residual proveniente da queima da casca de arroz.pdf: 10705111 bytes, checksum: f3dc853aa0f1b672236697852c098384 (MD5)
Made available in DSpace on 2017-01-25T12:37:45Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Desenvolvimento de materiais cerâmicos refratários com adição da sílica residual proveniente da queima da casca de arroz.pdf: 10705111 bytes, checksum: f3dc853aa0f1b672236697852c098384 (MD5) Previous issue date: 2014-03-20
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.

APA, Harvard, Vancouver, ISO, and other styles

2

Braconnier, Daniel J. "Materials Informatics Approach to Material Extrusion Additive Manufacturing." Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-theses/204.

Full text

Abstract:

Process-structure-property relationships in material extrusion additive manufacturing (MEAM) are complex, non-linear, and poorly understood. Without proper characterization of the effects of each processing parameter, products produced through fused filament fabrication (FFF) and other MEAM processes may not successfully reach the material properties required of the usage environment. The two aims of this thesis were to first use an informatics approach to design a workflow that would ensure the collection of high pedigree data from each stage of the printing process; second, to apply the workflow, in conjunction with a design of experiments (DOE), to investigate FFF processing parameters. Environmental, material, and print conditions that may impact performance were monitored to ensure that relevant data was collected in a consistent manner. Acrylonitrile butadiene styrene (ABS) filament was used to print ASTM D638 Type V tensile bars. MakerBot Replicator 2X, Ultimaker 3, and Zortrax M200 were used to fabricate the tensile bars. Data was analyzed using multivariate statistical techniques, including principal component analysis (PCA). The magnitude of effect of layer thickness, extrusion temperature, print speed, and print bed temperature on the tensile properties of the final print were determined. Other characterization techniques used in this thesis included: differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The results demonstrated that printer selection is incredibly important and changes the effects of print parameters; moreover, further investigation is needed to determine the sources of these differences.

APA, Harvard, Vancouver, ISO, and other styles

3

Skerry, Nathaniel S. (Nathaniel Standish) 1971. "Transformed materials : a material research center in Milan, Italy." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/70358.

Full text

Abstract:

Thesis (M. Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 2002.
Includes bibliographical references (p. 74-75).
[Transformed Materials] is an exploration into today's design methodologies of architecture production. The emergence of architectural form is questioned in relation to the temporal state of design intent and the physical material construct. At a time when there is an increased awareness of the current state of technology, material innovation and methods of fabrication, there are new speculations of what materiality is and can be. This thesis will propose an architecture that emerges through an exploration of the material concept that directly informs and expresses the fundamental ideas of the project. Building methods have changed widely over time, and are co-responsible for creating a dialog between functional requirements, technological invention, and material implication that reflects the current cultural state. Today's architectural products have in a sense reverted back to thin surfaces. Current cultural issues such as socioeconomic, environmental impact, transportability, efficiency, lightness, storability, technology, and mass production, have over time created a state of "thinness ". This project tries to offset the current trend of building by accepting the norms of architectural products, and reinventing their role within a contemporary language that explores more deeply the material qualities and properties associates with it. This thesis will use steel as the primary building material. Steel is a material that has become standardized in how it is shaped and formed, thus its ability to produce an architecture has been reduced purely to a dogmatiC approach of engineered solutions or preconceived results. Steel, is artificial by nature; if we suspend our preconceptions of steel, could the material be designed such that its role is critical in defining space, structure and program in a tectonic system? The area of research and examination will be focused on the design of a Material Research Center (mRC). located in Milan, Italy.
by Nathaniel S. Skerry.
M.Arch.

APA, Harvard, Vancouver, ISO, and other styles

4

Martin, Luke Andrew. "A Novel Material Modulus Function for Modeling Viscoelastic Materials." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/26891.

Full text

Abstract:

Accurately modeling damping in engineering structures has plagued scientist and engineers for decades. The integration of viscoelastic materials into engineering structures can reduce undesired vibrations and serve as an effective passive control mechanism. Various techniques have been developed to model viscoelastic materials. The growing popularity of finite element analysis in the 1980s and 1990s spawned new techniques for modeling damping in complex structures. The technique defined in this dissertation can be incorporated into finite element models. In metals, the modulus of elasticity can be modeled as a constant. That is, the modulus of elasticity is not treated as a function of frequency in dynamic models. For viscoelastic materials, the modulus of elasticity can be assumed to be constant for static forces and sinusoidal forcing functions. However, when viscoelastic materials undergo excitations from a random or transient forcing function the constant modulus of elasticity assumption may not be valid. This is because the second order equation of motion has non-constant coefficients or coefficients that vary as a function of frequency. The Golla-Hughes-McTavish (GHM) method is a technique used to incorporate the frequency dependency of viscoelastic materials into finite element models. The GHM method is used as a way to alleviate working with second order differential equations with non-constant coefficients. This dissertation presents the theory for a new material modulus function suitable for application within the framework of the GHM method. However, the new material modulus function uses different assumptions and is referred to as the Modified GHM method or MGHM method. The MGHM method is shown to improve the curve fit and damping characteristics of the GHM method. Additionally, the MGHM method is shown to reduce to the GHM method when the original GHM assumptions are imposed.
Ph. D.

APA, Harvard, Vancouver, ISO, and other styles

5

Samsonow, Emily L. "Material Celebration: Exploring the Architectural Potential of Waste Materials." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1306501078.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Freitas, Ricardo Luiz Barros de [UNESP]. "Fabricação, caracterização e aplicações do compósito PZT/PVDF." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/100281.

Full text

Abstract:

Made available in DSpace on 2014-06-11T19:30:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-08-31Bitstream added on 2014-06-13T20:21:16Z : No. of bitstreams: 1 freitas_rlb_dr_ilha.pdf: 3147438 bytes, checksum: 01acb2a6a67b2e11009fd170fd595861 (MD5)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Um material compósito é constituído pela combinação de dois ou mais materiais, onde se procura sintetizar um novo material multifásico, e que abrigue as melhores características individuais de cada um de seus constituintes. Compósitos de polímeros (matriz) e ferroelétricos (inclusões) podem manifestar piezoeletricidade, ou seja, a produção de uma resposta elétrica devido a uma excitação mecânica, e vice-versa. Nesta tese o material polimérico usado para preparar os filmes ou lâminas de nanocompósitos é o PVDF, e, o material cerâmico é formado por nanopartículas de PZT. Ambos os materiais são dielétricos, porém, com características muito distintas (por exemplo, o PVDF tem aproximadamente 1/4 da densidade e 1/250 da constante dielétrica do PZT). O PZT é muito utilizado em transdutores, principalmente devido aos seus elevados coeficientes piezoelétricos, contudo, é quebradiço e sofre desgaste quando empregado na forma de filmes ou lâminas. Por outro lado, o PVDF é um polímero piezoelétrico que apresenta grande flexibilidade e excelentes resistências mecânica e química, porém, seus coeficientes piezoelétricos são apenas moderados. A fim de se aumentar a flexibilidade do PZT, mistura-se o pó cerâmico, na forma de nanopartículas, com o PVDF, também pulverizado. Na tese, evidencia-se que o compósito constituído por esta combinação cerâmica-polímero proporciona uma nova classe de materiais funcionais com grande potencial de aplicação, por terem combinadas a resistência e rigidez das cerâmicas, e, a elasticidade, flexibilidade, baixa densidade e elevada resistência a ruptura mecânica dos polímeros. O novo material tem grande resistência a choques mecânicos, flexibilidade, maleabilidade, e, principalmente, coeficientes piezoelétricos relativamente elevados. Amostras do compósito...
A composite material is constituted by the combination of two or more materials, which synthesizes a new multiphase material, and has the best individual characteristics of each of its constituents. Polymer composites (matrix) and ferroelectric (inclusions) can express piezoelectricity, i.e. the production of an electrical response due to a mechanical excitation, and vice versa. In this thesis the polymeric material used to prepare the films or slides of nanocomposites is the PVDF, and, ceramic material is formed by PZT nanoparticles. Both materials are dielectrics, however, with very different characteristics (for example, the PVDF is approximately 1/4 density and 1/250 relative permittivity from PZT). The PZT is widely used in transducers, mainly due to their high piezoelectric coefficients, however, is brittle and suffers wear and tear when employed in the form of films or slides. On the other hand, the PVDF is a piezoelectric polymer that offers great flexibility and excellent mechanical and chemical resistances, however, its piezoelectric coefficients are only moderate. In order to increase the flexibility of PZT, ceramic powder is mix, in the form of nanoparticles, with PVDF, also sprayed. In theory, it becomes evident that composite consisting of this ceramic- polymer combination delivers a new class of functional materials with great potential for application, because they combine the strength and rigidity of ceramics, and elasticity, flexibility, low density and high resistance to mechanical disruption of polymers. The new material has great resistance to mechanical shock, flexibility, suppleness, and, primarily, relatively high piezoelectric coefficients. PZT/PVDF composite samples were fabricated and characterized aiming to applications such as: piezoelectric actuators, acoustic emission detectors, and energy... (Complete abstract click electronic access below)

APA, Harvard, Vancouver, ISO, and other styles

7

Freitas, Ricardo Luiz Barros de. "Fabricação, caracterização e aplicações do compósito PZT/PVDF /." Ilha Solteira, [s.n.], 2012. http://hdl.handle.net/11449/100281.

Full text

Abstract:

Orientador: Aparecido Augusto de Carvalho
Coorientador: Antônio de Pádua Lima Filho
Banca: Cláudio Kitano
Banca: João Antonio Pereira
Banca: Adriano Rogério Bruno Tech
Resumo: Um material compósito é constituído pela combinação de dois ou mais materiais, onde se procura sintetizar um novo material multifásico, e que abrigue as melhores características individuais de cada um de seus constituintes. Compósitos de polímeros (matriz) e ferroelétricos (inclusões) podem manifestar piezoeletricidade, ou seja, a produção de uma resposta elétrica devido a uma excitação mecânica, e vice-versa. Nesta tese o material polimérico usado para preparar os filmes ou lâminas de nanocompósitos é o PVDF, e, o material cerâmico é formado por nanopartículas de PZT. Ambos os materiais são dielétricos, porém, com características muito distintas (por exemplo, o PVDF tem aproximadamente 1/4 da densidade e 1/250 da constante dielétrica do PZT). O PZT é muito utilizado em transdutores, principalmente devido aos seus elevados coeficientes piezoelétricos, contudo, é quebradiço e sofre desgaste quando empregado na forma de filmes ou lâminas. Por outro lado, o PVDF é um polímero piezoelétrico que apresenta grande flexibilidade e excelentes resistências mecânica e química, porém, seus coeficientes piezoelétricos são apenas moderados. A fim de se aumentar a flexibilidade do PZT, mistura-se o pó cerâmico, na forma de nanopartículas, com o PVDF, também pulverizado. Na tese, evidencia-se que o compósito constituído por esta combinação cerâmica-polímero proporciona uma nova classe de materiais funcionais com grande potencial de aplicação, por terem combinadas a resistência e rigidez das cerâmicas, e, a elasticidade, flexibilidade, baixa densidade e elevada resistência a ruptura mecânica dos polímeros. O novo material tem grande resistência a choques mecânicos, flexibilidade, maleabilidade, e, principalmente, coeficientes piezoelétricos relativamente elevados. Amostras do compósito... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: A composite material is constituted by the combination of two or more materials, which synthesizes a new multiphase material, and has the best individual characteristics of each of its constituents. Polymer composites (matrix) and ferroelectric (inclusions) can express piezoelectricity, i.e. the production of an electrical response due to a mechanical excitation, and vice versa. In this thesis the polymeric material used to prepare the films or slides of nanocomposites is the PVDF, and, ceramic material is formed by PZT nanoparticles. Both materials are dielectrics, however, with very different characteristics (for example, the PVDF is approximately 1/4 density and 1/250 relative permittivity from PZT). The PZT is widely used in transducers, mainly due to their high piezoelectric coefficients, however, is brittle and suffers wear and tear when employed in the form of films or slides. On the other hand, the PVDF is a piezoelectric polymer that offers great flexibility and excellent mechanical and chemical resistances, however, its piezoelectric coefficients are only moderate. In order to increase the flexibility of PZT, ceramic powder is mix, in the form of nanoparticles, with PVDF, also sprayed. In theory, it becomes evident that composite consisting of this ceramic- polymer combination delivers a new class of functional materials with great potential for application, because they combine the strength and rigidity of ceramics, and elasticity, flexibility, low density and high resistance to mechanical disruption of polymers. The new material has great resistance to mechanical shock, flexibility, suppleness, and, primarily, relatively high piezoelectric coefficients. PZT/PVDF composite samples were fabricated and characterized aiming to applications such as: piezoelectric actuators, acoustic emission detectors, and energy... (Complete abstract click electronic access below)
Doutor

APA, Harvard, Vancouver, ISO, and other styles

8

Freitas, Jefferson Arlen. "Sintese e caracterização de biossorventes a partir da imobilização da biomassa Sargassum sp em matrizes ceramicas pelo processo sol-gel." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266214.

Full text

Abstract:

Orientador: Elias Basile Tambourgi
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
Made available in DSpace on 2018-08-11T04:08:18Z (GMT). No. of bitstreams: 1 Freitas_JeffersonArlen_D.pdf: 3985383 bytes, checksum: 8a45be364ed2c151ea51fbb373ede3d6 (MD5) Previous issue date: 2007
Resumo: Este trabalho tratou da pesquisa e desenvolvimento de um adsorvente alternativo, aplicável no tratamento de rejeitos líquidos industriais, contendo baixas concentrações dos metais pesados Cd, Cu e Zn. Ele teve como objetivo geral produzir esferas adsorventes de zeólita 4A - Sargassum sp. com custo de produção competitivo e com elevada capacidade de captura dos metais pesados Cd, Cu e Zn, nas quais o processo de adsorção ocorra com elevada eficiência e com cinética favorável. A produção das esferas envolveu uma abordagem inovadora do Processo Sol - Gel, a qual permitiu produzir sete tipos de esferas, partindo da combinação e imobilização de adsorventes tradicionais pesquisados: biomassa Sargassum sp., caulim, alumina e zeólita. Este processo de imobilização das partículas dos adsorventes tradicionais causa uma obstrução dos poros e canais existentes nestas partículas e, com isto, reduz a capacidade de captura dos metais pesados nas esferas resultantes. Felizmente, a combinação de adsorventes realizada viabilizou a obtenção de esferas adsorventes com elevada capacidade de captura de metais pesados e com cinética favorável. É o caso das esferas de zeólita 4A, com capacidade máxima de captura de Cd+Cu+Zn de 746 µmol/g, com uma velocidade de captura aproximada de 18 µmol/g.h e com uma eficiência de captura de 82% e das esferas de zeólita 4A - 50% em peso de Sargassum sp., com capacidade máxima de captura de Cd+Cu+Zn de 709 µmol/g, com uma velocidade de captura aproximada de 20 µmol/g.h e com uma eficiência de captura de 83%. O comportamento de adsorção destas esferas se ajustou ao modelo de equilíbrio de Freundlich. Elas possuem uma cinética de adsorção compatível com o modelo cinético de pseudo-segunda ordem. Ao tratarem um efluente industrial real, estas esferas apresentam uma eficiência de captura de Cd+Cu+Zn =90% enquanto que numa resina quelante comercial esta eficiência é de 99,5%. Tem-se, pois, esferas adsorventes com elevada eficiência e baixo custo de produção, tornando-as um bom adsorvente para aplicação no tratamento de efluentes líquidos industriais com baixa concentração de Cd, Cu e Zn
Abstract: In this work had been made a research and the development of an alternative adsorbent which may be applied in the treatment of industrial liquid effluents containing low concentration of heavy metals, Cd, Cu and Zn. The main objective was to produce 4A type zeolite-Sargassum sp. adsorbents spheres with the following characteristics: competitive fabrication cost; high uptake capacity of the heavy metals, Cd, Cu and Zn; high affinity by the referred heavy metals; and appropriated adsorption kinetic. The marking of the adsorbents spheres had involve the innovative use of the Sol-gel Process. That had permitted to obtain seven types of adsorbents spheres for combination and immobilization of the particles of traditional adsorbents Sargassum sp., kaolin, alumina and 4A type zeolite. This immobilization process causes an obstruction of the pores and the channels present in these particles that reduced the uptake capacity of the produced adsorbents spheres. Fortunately, the combination of traditional adsorbents particles produced adsorbent spheres with high uptake capacity, high uptake efficiency, and appropriate adsorption kinetic. As, two types of adsorbent spheres, 4A type zeolite and 4A type zeolite-50% Sargassum sp. adsorbed 746 µmol/g and 709 µmol/g with an adsorption velocity of 18 µmol/g.h and 20 µmol/g.h, and a uptake efficiency of 82% and 83%, respectively. The adsorption behavior of these adsorbent spheres had been fitting to the Freundlich model. They have an adsorption kinetic compatible with the pseudo-second order model. When it treated an industrial liquid effluent with these adsorbent spheres, they showed a uptake efficiency higher than 90% and while an uptake efficiency of 99,5% is shown for the commercial chelant resin
Doutorado
Sistemas de Processos Quimicos e Informatica
Doutor em Engenharia Química

APA, Harvard, Vancouver, ISO, and other styles

9

Karlsson, Johan. "Composite material in car hood : Investigation of possible sandwich materials." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-45633.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Wretborn, Joel. "Modelling cracks in solid materials using the Material Point Method." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-136797.

Full text

Abstract:

This thesis investigates a novel way to simulate cracks as an extension of the Mate- rial Point Method (MPM). Previous methods, like CRAMP (CRAcks with Material Points), often use an explicit crack representation to define the material crack. We use an implicit crack representation defined as the intersection between pieces of the original specimen created by a pre-fracture process. Material chunks are there- after forced together using massless particle constraints. The method has proven successful in tearing scenarios, and the main benefits are: (1) minor computational overhead compared to the initial MPM algorithm; (2) simple to implement and scales well in 3 dimensions; (3) gives easy and controllable setup phase for desired material failure mode. The development of the crack extension has required a fully general MPM solver that can handle arbitrarily many distinct bodies connected in the same simulation. Current collision schemes for MPM exists, however these are often focused on two-body collisions and does not scale well for additional objects due to inaccuracies in contact normal calculations. We present a method that uses an iterative pair-wise comparison scheme to resolve grid collisions that extends to any number of collision objects.

APA, Harvard, Vancouver, ISO, and other styles

11

Counts, William Arthur. "Mechanical behavior of bolted composite joints at elevated temperature." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17315.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Stochero, Naiane Paiva. "Desenvolvimento de cerâmica refratária com fibra de aço e sílica residual proveniente da queima da casca de arroz." Universidade Federal do Pampa, 2015. http://dspace.unipampa.edu.br:8080/xmlui/handle/riu/782.

Full text

Abstract:

Submitted by Cátia Araújo (catia.araujo@unipampa.edu.br) on 2017-01-26T11:18:24Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Desenvolvimento de cerâmica refratária com fibra de aço e sílica residual proveniente da queima da casca de arroz.pdf: 5761236 bytes, checksum: a142f60a2f92e30742027abc659f21f3 (MD5)
Approved for entry into archive by Cátia Araújo (catia.araujo@unipampa.edu.br) on 2017-01-26T11:18:41Z (GMT) No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Desenvolvimento de cerâmica refratária com fibra de aço e sílica residual proveniente da queima da casca de arroz.pdf: 5761236 bytes, checksum: a142f60a2f92e30742027abc659f21f3 (MD5)
Made available in DSpace on 2017-01-26T11:18:41Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Desenvolvimento de cerâmica refratária com fibra de aço e sílica residual proveniente da queima da casca de arroz.pdf: 5761236 bytes, checksum: a142f60a2f92e30742027abc659f21f3 (MD5) Previous issue date: 2015-02-05
O Estado do Rio Grande do Sul apresenta um dos maiores índices de produção de arroz do país, e Alegrete é um dos municípios que lidera esta estatística. A casca de arroz é um dos subprodutos originados do beneficiamento do arroz, e é muito utilizada como fonte de energia térmica para a geração de energia elétrica. Após a queima é gerada a cinza da casca do arroz, rica em sílica. Sendo assim, o objetivo deste trabalho é diversificar o aproveitamento deste resíduo como matéria-prima alternativa para materiais cerâmicos refratários e agregar valor a este subproduto. Outro objetivo é aumentar as propriedades mecânicas de matrizes frágeis, que possuem uma tendência a falhar por fadiga e choque térmico, limitando a sua aplicabilidade. Foram fabricados materiais cerâmicos refratários com 80% de argila caulim, 20% de sílica da casca de arroz e fibras de aço em teores volumétricos de 3%, 6% e 9%. Realizaram-se ensaios de absorção de água, densidade aparente, porosidade aparente, resistência à compressão, tração direta, flexão em três pontos, ensaio de choque térmico e análise de microestrutura do material. Com a substituição de argila pela sílica, foram obtidas maior resistência mecânica, e maior tenacidade, possivelmente devido à diminuição da porosidade e pelo aumento do nível de vitrificação. A cerâmica com 9% de fibra obteve o melhor desempenho em relação à ductilidade, em razão do maior grau de deformação do material até o momento de ruptura. As cerâmicas com 3% de fibra e 6% de fibra apresentaram os melhores desempenhos frente ao choque térmico. Na análise da mineralogia do material após a sinterização, observou-se a formação de picos de mulita. Com a substituição da argila pela sílica foram identificados picos de cristobalita.
The State of Rio Grande do Sul presents one of the highest indices of rice production in the Country, and Alegrete is one of the towns that leads this statistics. Rice husk, is one of the byproducts originated from processing of rice, and is very used as thermal energy source to generate electricity. After firing generated rice husk ash, rich in silica. Thus, the aim of this work is to diversify the use of this waste as an alternative raw material for refractory ceramic materials and add value to this byproduct. Another objectiveis to increase the mechanical properties of brittle matrices that have tendency to fail by fatigue and thermal shock, limiting its applicability. Were manufactured refractory ceramic materials with 80% of kaolin clay, 20% rice husk silica, and steel fibers in volumetric concentrations of 3%, 6% and 9%. Tests about water absorption were done, apparent density, apparent porosity, compressive strength, direct traction, three points flexion, thermal shock test and analysis of the microstructure of the material. Replacing the clay by silica, was obtained greater strength, and greater toughness, possibly due to the decrease of the porosity and increasing the level of vitrifying. The ceramic with 9% fiber obtained the better performance relative for ductility, due to the higher degree of deformation of the material until the moment of rupture. The ceramic with 3% fiber and 6% fiber showed better performance front thermal shock. In mineralogical analysis of the material showed the formation of mullite peaks. With substituting the clay by silica cristobalite peak was identified.

APA, Harvard, Vancouver, ISO, and other styles

13

Gehlen, Aline. "Avaliação da influência do tipo de argila MMT incorporada em blenda EVA/PVC através do processamento em extrusora dupla-rosca." reponame:Repositório Institucional da UCS, 2010. https://repositorio.ucs.br/handle/11338/570.

Full text

Abstract:

Submitted by Marcelo Teixeira (mvteixeira@ucs.br) on 2014-06-03T20:37:16Z No. of bitstreams: 1 Dissertacao Aline Gehlen .pdf: 3582943 bytes, checksum: 4de504b4d7925f71eeeecc0879487a8c (MD5)
Made available in DSpace on 2014-06-03T20:37:16Z (GMT). No. of bitstreams: 1 Dissertacao Aline Gehlen .pdf: 3582943 bytes, checksum: 4de504b4d7925f71eeeecc0879487a8c (MD5)

APA, Harvard, Vancouver, ISO, and other styles

14

Lima, Leandro Soares de. "A influência das variáveis de processamento e de diferentes tipos de nanocargas nas propriedades dos compósitos de polipropileno." reponame:Repositório Institucional da UCS, 2015. https://repositorio.ucs.br/handle/11338/980.

Full text

Abstract:

Neste trabalho foi realizado uma avaliação das propriedades térmicas e mecânicas dos compósitos de PP/PP-g-AM com 5% e 10% m/m das nanocargas MMT-Na+, MMT-15A, MMT-30B, CaCO3 e CaCO3-AE, preparados em extrusora de dupla rosca co-rotante com configuração de L/D 32 para elencar três nanocargas com melhor desempenho nestas propriedades. Posteriormente foram processados compósitos de PP/PP-g-AM com 10% m/m das nanocargas MMT-Na+, MMT-15A e CaCO3 com a configuração de L/D 46 processadas uma e três vezes para avaliar a influência do processamento nas propriedades mecânicas, térmicas, morfológicas, reológicas e termomecânicas. Nos compósitos de PP com nanocargas preparados com L/D 32, os resultados demonstraram que a adição do agente compatibilizante PP-g-AM provoca alterações nas propriedades mecânicas, indicando que os compósitos de PP compatibilizados apresentaram resultados superiores nestas propriedades em relação aos compósitos de PP não compatibilizados. Nos compósitos de PP com as nanocargas MMT-Na+, MMT-15A e o CaCO3 preparados na configuração L/D 32 apresentaram os resultados mais significativos nas análises das propriedades mecânicas e térmicas quando incorporadas em 10% m/m ao PP/PP-g-AM, sendo utilizadas para análise da variação das condições de processamento. Posteriormente foi realizado o estudo do efeito do tipo de configuração da rosca (L/D 46) e de nanocarga nos compósitos de PP/PP-g-AM. Estes compósitos foram caracterizados pelas suas propriedades mecânicas, propriedades térmicas, morfologia, reologicas e termomecânicas. A análise das propriedades mecânicas dos compósitos processados com a configuração L/D 46 uma e três vezes apresentou uma redução nas propriedades mecânicas em comparação com os compósitos processados com configuração L/D 32, ficando com valores próximos ao do PP puro. Este resultado indicou que a variação da configuração L/D no processamento proporcionou a degradação da matriz polimérica, evidenciada nos ensaios de reologia, onde houve um aumento da fluidez dos compósitos e uma redução na viscosidade complexa. As análises de MET mostraram que a argila MMT-15A incorporada de 10% m/m ao PP/PP-g-AM apresentou formação de tactóides intercalados e fase esfoliada no processamento com L/D 32. A análise das propriedades discutidas neste trabalho indicou que a argila MMT-15A apresenta a melhor adesão e dispersão na matriz de polipropileno.
Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2015-08-12T17:55:06Z No. of bitstreams: 1 Dissertacao Leandro Soares de Lima.pdf: 3194982 bytes, checksum: 3979198068c0c31fd2c896803cf04888 (MD5)
Made available in DSpace on 2015-08-12T17:55:06Z (GMT). No. of bitstreams: 1 Dissertacao Leandro Soares de Lima.pdf: 3194982 bytes, checksum: 3979198068c0c31fd2c896803cf04888 (MD5)
In this work an evaluation of the thermal and mechanical properties of PP/PP-g-MA composites with 5 and 10 wt% of MMT-Na+, MMT-15A, MMT-30B, CaCO3 and CaCO3-AE nanofillers was performed. Composites were prepared in a co-rotating, double-screw extruder configured at L/D ratio 32 to specify three nanofillers of best performance. Thereafter PP/PP-g-MA composites with 10 wt% of MMT-Na +, MMT-15A and CaCO3 nanofillers at L/D ratio 46 were processed one and three times in order to evaluate the influence of processing on the mechanical, thermal, morphological, rheological and thermo- mechanical properties. For PP nanocomposites with nanofillers prepared at L/D ratio 32, results demonstrate that the addition of the compatibilizing agent PP-g-MA changes the mechanical properties, indicating that for these properties, the results obtained for the compatibilized PP composites are improved in relation to those obtained for the non-compatibilized samples. PP composites with MMT-Na+, MMT-15A and CaCO3 nanofillers prepared at L/D ratio 32 configuration had the most relevant results obtained for mechanical and thermal properties when these nanofillers were incorporated in the amount of 10% m/m to PP/PP-g-MA, so they were used in the analysis of the variation of the processing conditions. The effect of the screw configuration L/D ratio 46 and of nanofiller in PP/PP-g-MA composites was also studied. These composites were characterized by their mechanical, thermal, morphological, rheological and thermo-mechanical properties. Analysis of the mechanical properties of the composites processed at L/D 46 ratio one and three times showed to reduced values when compared to the composites processed at the configuration L/D 32 the figures being close to those of neat PP. These data reveals that by varying the L/D ratio configuration during processing the polymer matrix is degraded, as evidenced by rheology tests, a flow increase and reduction in complex viscosity being observed in the composites. TEM analyses have shown that 10 wt% MMT-15A clay incorporated to PP/PP-g-MA formed intercalated tactoids and exfoliated phase during processing at L/D ratio 32. Analysis of the properties discussed in this work indicated that MMT-15A clay has the best adhesion and dispersion in the polypropylene matrix.

APA, Harvard, Vancouver, ISO, and other styles

15

Gokay, Kemal. "Contact Mechanics Of Graded Materials With Two Dimensional Material Property Variations." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606527/index.pdf.

Full text

Abstract:

ABSTRACT CONTACT MECHANICS OF GRADED MATERIALS WITH TWODIMENSIONAL MATERIAL PROPERTY VARIATIONS Gö
kay, Kemal M.S., Department of Mechanical Engineering Supervisor: Asst. Prof. Dr. Serkan Dag September 2005, 62 pages Ceramic layers used as protective coatings in tribological applications are known to be prone to cracking and debonding due to their brittle nature. Recent experiments with functionally graded ceramics however show that these material systems are particularly useful in enhancing the resistance of a surface to tribological damage. This improved behavior is attributed to the influence of the material property gradation on the stress distribution that develops at the contacting surfaces. The main interest in the present study is in the contact mechanics of a functionally graded surface with a two &ndash
dimensional spatial variation in the modulus of elasticity. Poisson&rsquo
s ratio is assumed to be constant due to its insignificant effect on the contact stress distribution [30]. In the formulation of the problem it is assumed that the functionally graded surface is in frictional sliding contact with a rigid flat stamp. Using elasticity theory and semi-infinite plane approximation for the graded medium, the problem is reduced to a singular integral equation of the second kind. Integral equation is solved numerically by expanding the unknown contact stress distribution into a series of Jacobi polynomials and using suitable collocation points. The developed method is validated by providing comparisons to a closed form solution derived for homogeneous materials. Main numerical results consist of the effects of the material nonhomogeneity parameters, coefficient of friction and stamp size and location on the contact stress distribution.

APA, Harvard, Vancouver, ISO, and other styles

16

Magnusson, Simon. "Environmental Perspectives on Urban Material Stocks used in Construction : Granular Materials." Licentiate thesis, Luleå tekniska universitet, Geoteknologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-60305.

Full text

Abstract:

The peoples demand of functions and services in cities is the driver for energy and material flows. Most people in the world are now living in urban areas. In order to achieve a sustainable development of cities, both resource use and environmental impact have to be reduced. For construction activities, an important aspect is to increase the reuse of construction materials. From a resource perspective, the urban demand for construction of buildings, infrastructure and other facilities results in materials accumulated in constructions but also in other applications and in landfills. The materials can be described as the urban material stock where some materials are used and others are not used, i.e. wasted. There are many cases where material stocks are used for construction purposes. For example, used concrete and bricks, excavated soil and rock from construction projects and other wasted materials such as rubber from tires can be crushed, shredded and sorted to granules and used in many different construction applications. Different perspectives can be applied when assessing the environmental impacts of using stocked material in construction. The overall aim of this thesis is to study the environmental impacts of using granular soil, rock and rubber in construction. For soil and rock, the aim is to study the environmental impact of material management in urban areas. For granular rubber, the aim is to study the environmental impact of artificial turf from a life cycle perspective and from different infill materials of recycled and new rubber and plastics. The literature of excavated soil and rock was reviewed in order to identify and quantify the material flows and greenhouse gas (GHG) emissions from the management of soil and rock materials. For artificial turf and the different infill materials, a life cycle approach was used to quantify the energy use and GHG emissions. A chemical analysis of potential chemical leaching from the different infill materials to water was conducted in order to compare potential local emissions to water. Based on the results, it was concluded that the knowledge about the urban flows of excavated soil and rock is lacking in terms of patterns, quantities, qualities and its environmental performance. A resource perspective is missing in the literature. However, the recycling of soil and rock can reduce resource use and GHG emissions. It was suggested that models are developed that take into account future material demand and availability to soils and rock. From such information it would be able to assess sustainable management practices and the possibilities of sharing materials between urban construction projects in order to reduce resource use and environmental impact. It was concluded that for the life cycle of artificial turf, the production of construction materials contributes largely to energy use and GHG emissions. Differences in terms of energy use and GHG emissions for the production of infill materials are large. The production of new material required more energy and resulted in more GHG emissions than using recycled rubber. The potential release of substances from infill materials to water were shown to be possible for all infill materials analyzed. Previous assessments of local environmental impacts of using infills generally concludes that the impacts are small. These assessments are primarily focused on infill of recycled tires. It is therefore concluded that environmental assessments of local impact should include all infill types. Environmental assessments of using stocked materials in construction should take into consideration the material applications´ significance for the environmental impacts at a higher system level. Broader system boundaries in environmental assessments will reduce the risk for sub-optimizations when taking decisions on how materials should be used in construction.

APA, Harvard, Vancouver, ISO, and other styles

17

Thomas, Katie Lloyd. "Building materials : conceptualising materials via the architectural specification." Thesis, Middlesex University, 2010. http://eprints.mdx.ac.uk/6284/.

Full text

Abstract:

The last few decades have seen unprecedented levels of change both in the production of building materials and in the ways they are deployed in building. Despite rigorous debates about materials in architecture from very different areas of theory and practice – ranging from the new materialists' critique of the concept of matter to ecological concerns with embodied energy and life cycle analysis of building materials – the extent to which these developments might demand more adequate conceptualisations of materials remains unexplored. The position this research takes is that building materials cannot be assumed to be nothing more than particular instances of matter in general – whether matter is understood in its classical philosophical hylomorphic relation to form, or as the physical substances of science. Here, the architectural specification – a document usually considered to be merely 'technical' and therefore outside theoretical enquiry – provides descriptions of building materials drawn from inside architectural practice. It yields a number of types of description – from 'naming' to the 'recipe' to performance – and the differences between these 'forms of clause' and the degree to which each is contained by or exceeds the notion of hylomorphic matter are shown to involve radically different conceptualisations of materials. Moreover, the specification makes visible the changing historical and industrial contexts that constitute its format and content. Part I sets out this variation and constructs a typology of forms of clause, and Part II studies two of them in detail. The key philosophical move derives from Gilbert Simondon's work on individuation in so far as materials are considered not as substances or as matter (as already individuated individuals) but in terms of the dynamic processes through which they are constituted (individuation). First, process-based clauses provide found descriptions of form taking in terms of such operations, and expand Simondon's account of the preparations which set up the possibility of individuation in a technical object to include statutory, social and other operations in addition to the physical ones he describes. Second, the performance clause requires us to understand how specific use (excluded by Simondon in his accounts of technical systems) might itself become preparatory in the new industrial conditions of performance-engineered materials. Part III takes up Simondon's 'complete system' of individuation and understands the variety of forms of clause as evidence of a variety of 'systems of material' which necessarily include the full range of the preparations which make possible the specific deployment of any given material in building. Furthermore, what is constituted in any individuating system is not so much an individual as the possibility of a transductive mediation between hitherto disparate realities. It is, in particular, the possibilities of new mediations that are produced in industry – between a terrorist threat and a piece of glass – in addition to more familiar ones – between a notion of form and a lump of clay for example, that demand attention and new conceptualisations. For Simondon, transduction is also a process of thought which derives problems and resolutions from within a domain rather than seeking a principle from elsewhere. If we are to understand how concepts emerge from applied practices and their productions, and not just from philosophy and science, then the transductive method has applications well beyond the question of building materials that is put into motion via the architectural specification in the process of this research.

APA, Harvard, Vancouver, ISO, and other styles

18

Lau, Chee Keong. "Investigation on alkali activated materials: Materials to structures." Thesis, Curtin University, 2021. http://hdl.handle.net/20.500.11937/84508.

Full text

Abstract:

The material and structural characteristics of alkali activated materials were investigated. A mix design framework was proposed to consider the reactive composition of raw materials, with the mixes obtained optimised by the statistical method and curing regime. Subsequently, alkali activated concrete was examined in torsion and fatigue. Alkali activated concrete in torsion correlates well with the existing model for conventional concrete. A new testing methodology was proposed for the testing of concrete pavements in fatigue.

APA, Harvard, Vancouver, ISO, and other styles

19

Michal, Potran. "Ispitivanje biokompatibilnosti i mehaničkih karakteristika polimera za bazu zubne proteze." Phd thesis, Univerzitet u Novom Sadu, Medicinski fakultet u Novom Sadu, 2015. http://www.cris.uns.ac.rs/record.jsf?recordId=94886&source=NDLTD&language=en.

Full text

Abstract:

U uvodnom delu doktorske disertacije opisuje se kompleksnost problematike korišćenja polimera za bazu zubne proteze, sa osvrtom na njihove opšte osobine, stepen biokompatibilnosti i njihove mehaničke karakteristike. Detaljno je opisana problematika ispitivanja stomatoloških materijala i napravljeno je poređenje i korelacija između in vitro i in vivo načina ispitivanja biokompatibilnosti. Drugi deo obuhvata ispitivanje čvrstoće polimera za bazu zubne proteze i analizu uticaja osobina materijala u odnosu na biološku sredinu u kojoj obavljaju svoju funkciju, i u odnosu na sile kojima su tokom funkcije materijali izloženi. Cilj doktorske disertacije je utvrđivanje stepena biokompatibilnosti i mehaničkih karakteristika toplopolimerizujućih, hladnopolimerizujućih i termoplastičnih akrilata za bazu zubne proteze. Istraživanje je obuhvatilo 3 komercijalna materijala iz grupe akrilata, koji se razlikuju po hemijskom sastavu i načinu polimerizacije. Ispitivanje biokompatibilnosti rađeno je u in vitro i in vivo uslovima. Ispitivanje na ćelijskim kulturama obuhvatalo je dve ćelisjke linije (MRC 5 i L929) sa dva načina kontakta između ćelija i materijala (direktan, indirektan) i dva načina određivanja biološkog ishoda (MTT test, Agar difuzioni test). Istraživanje urađeno in vivo obuhvatalo je test subkutane implantacije, na animalnom modelu pacova, i test iritacije oralne sluzokože na animalnom modelu hrčka. Oba testa rađena su u skladu sa standardom ISO 10993. Cilj in vivo istraživanja bio je ispitivanje reakcije tkiva na implantirani materijal, računajući i završnu integraciju ili dezintegraciju implantiranog materijala. Prednost in vivo istraživanja nalazi seu analizi uticaja materijala na sterilno živo tkivo, uz praćenje imunološke reakcije, kao dopuna prethodnom istraživanju na ćelijskim kulturama. Dopunski deo in vivo ispitivanja biokompatibilnosti određen je prema kliničkoj upotrebi ispitivanih materijala, zbog čega je odabran test oralne iritacije sluzokože. Sluzokoža bukalne kesice sirijskog hrčka sastoji se od pločasto slojvitog epitela sa orožavanjem, što je predstavljao dobar model za ispitivanje polimera za bazu zubne proteze, pošto zubna proteza naleže na sluzokožu nepca i rezidualnog alveolarnog grebena koja takođe orožava. Drugi deo disertacije obuhvatao je ispitivanje mehaničkih karakteristika, pri čemu su urađeni test zatezne čvrstoće, test savojne čvrstoće, test čvrstoće loma i mikrotvrdoće, uz dopunsku analizu pratećih parametara. Rezultati ispitivanja biokompatibilnosti pokazali su da su testovi biokompatibilnosti osetljivi na upražnjeni metodološki postupak. Ispitivanjem na ćelijskim kulturama nisu utvrđene značajne razlike u citotoksičnosti između toplopolimerizujućih, hladnopolimerizujućih i termoplastičnih akrilata. Takođe, rezultati su se razlikovali u odnosu na tip ćelijske kulture i način provere biološkog ishoda, što se slaže sa prethodnim navodima o kompleksnoj problematici njihovog međusobnog poređenja. Ispitivanjem biokompatibilnosti subkutanom implantacijom praćen je inflamatorni odgovor tkiva u vremenskom intervalu od 90 dana. Reakcija organizma na implantirani materijal posmatrana je kroz ćelijske i tkivne parametre, u skladu sa ISO 10993. Dodatno je urađena i analiza hrapavosti implantiranih materijala. Histološkom analizom utvrđena je razlika u inflamatornom odgovoru u odnosu na korišćeni materijal, kao i prema vremenskom intervalu implantacije. Test oralne iritacije sluzokože nije se pokazao kao dovoljno senzitivan za ispitivanje ovih vrsta materijala. Ispitivanjem mehaničkih karakteristika utvrđene su razlike između toplopolimerizujućih, hladnopolimerizujućih i termoplastičnih akrilata. Najveći stepen čvrstoće utvrđen je kod toplopolimerizujućih akrilata dok je najveća konzistentnost rezultata bila u grupi termoplastičnih akrilata. Prezentovano istraživanje predstavlja prvu detaljnu analizu biokompatibilnosti i mehaničkih karaktestistika polimera za bazu zubne proteze.
The introduction describes the complexity of use of denture base materials, with regard to their general characteristics, biocompatibility and mechanical properties. Issues related to the testing of dental materials is described in detail and comparison is made between in vitro and in vivo methods of biocompatibility testing. The second part further covers the determination of strength of previously used materials, in relation to biological environment in which their function is conducted and in relation to the influence of masticatory forces which can contribute to their mechanical failure. The aim of the presented research was to assess the degree of biocompatibility and mechanical properties of cold curing, hot curing and thermoformed denture base materials. The research included three denture base materials, which differed according to their chemical composition and polymerization protocols. The biocompatibility testing was carried out in in vitro and in vivo conditions. The in vitro experiments covered two different cell lines (MRC 5 human lung fibroblasts and L929 mouse fibroblasts) with two types of contact (direct, indirect) and two different types of quantification of biological outcome (MTT assay and Agar overley test). The in vivo assessment of biocompatibility covered the subcutaneous implantation test, on the animal model of Wistar rat, and oral mucosa irritation test, on the animal model of sirian hamster. Both tests were conducted according to the ISO 10993. The aim of the in vivo investigation was to evaluate tissue reactions to the implanted materials, including the final integration or disintegration of the tested materials. The advantage of in vivo investigation included the possibility of monitoring the materials influence on living tissues, with the analysis of imunological response as an addition to the previously conductedresearchon cell cultures. The supplemental part of in vivo investigation was chosen according to the clinical use of the tested materials, which included the oral mucosa irritation test.The mucosa of hamster buccal pouch consists of stratified squamos epithelium, which is considered to be an adequate replacement for the human denture supporting tissues, which also consist of the same type of epithelium. The second part of thesis includes the determination of mechanical properties of denture base materials. It consists of four types of tests: tensile strength test, bending strength test, fracture toughness test and microhardness tests, followed by the analysis of corresponding parameters. The results of the biocompatibility tests showed that the biological outcome of the applied method is highly depended on the methodological procedure. The investigation conducted in vitro, on two different cell lines, did not show significant difference in cytotoxicity between hot curing, cold curing and thermoformed denture base materials. Also, the results were influenced by the type of cell culture and the evaluation method of biological outcome, which agrees with the previous allegations about the complexicity of their mutual comparison. The subcutaneous implantation test covered the inflammatory response in the time period of 90 days. The organism reaction to the implanted material was determined through the cell and tissue parameters of organism response, evaluation of which was conducted according to the ISO 10993. Additionally, the surface roughness of the implanted specimens of materials was also measured. The inflammatory response of the ogranism was influenced by the type of the implanted material and the time interval of implantation. The oral mucosa irritation test has proven not to be sufficiently sensitive for testing of this type of materials. Testing of the mechanical properties od denture base materials, revealed the difference between the cold curing, hot curing and thermofomed denture base materials. The highest strength was observed in hot curing materials, while the highest consistency of the results was observed in thermoformed resins. The presented investigation presents the first detail analysis of the biocompatibility and mechanical properties of the denture base materials, and as such presents a novelty in the field of dental materials characterization.

APA, Harvard, Vancouver, ISO, and other styles

20

Gonçalves, Rogéria Rocha [UNESP]. "Preparação e caracterização de filmes óxidos contendo componentes opticamente ativos." Universidade Estadual Paulista (UNESP), 2001. http://hdl.handle.net/11449/105805.

Full text

Abstract:

Made available in DSpace on 2014-06-11T19:35:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2001Bitstream added on 2014-06-13T21:07:17Z : No. of bitstreams: 1 goncalves_rr_dr_araiq.pdf: 4816799 bytes, checksum: 0ead4e8520f4bac562bdbb2a9a71bc5c (MD5)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
A preparação dos sistemas dopados com ions lantanídeos (Eu e Er): SnO2, HfO2, HfO2 disperso em matriz híbrida, SiO2-HfO2, Ta2O5, Ta2O5 disperso em matriz híbrida, através da metodologia sol gel, foi objetivo desta tese . São apresentados resultados para suspensões coloidais, sólidos (géis, xerogéis e pós) e filmes preparados por spin coating. Suspensões coloidais de SnO2 dopados com até 2% em mol de íons Eu e Er foram preparadas a partir da redispersão, em meio aquoso básico, de nanoparticulas com a superfície modificada. Diâmetro médio de 4 e 6 nm foram observados para os compostos dopados e puros respectivamente, através de espalhamento de luz e microscopia eletrônica de transmissão. Os compostos apresentam nanocristalitos, estrutura cassiterita. O íon Eu3+ ocupa dois diferentes sítios de simetria na matriz SnO2. Um referente ao ion Eu3+ na rede cristalina de SnO2, substituindo átomos de Sn4+, sítio de alta simetria (D2h, C2h) apresentando um tempo de vida de emissão do 5D0 de 6ms; e o segundo referente ao Eu3+ adsorvido na superfície da partícula apresentando um tempo de vida de emissão do 5D0 de 0,3 ms. A proteção da superfície da partícula com moléculas orgânicas, beta dicetonas, originou suspensões coloidais altamente luminescentes em meio aquoso, formando um complexo com o ion Eu3+ presente na superfície da partícula, apresentando tempo de vida de 0,6 ms. Filmes finos homogêneos e transparentes foram depositados a partir das suspensões coloidais usando spin coating. Monocamadas de até 200 nm foram depositadas, observando-se o aumento linear da espessura com a concentração de material e número de depósitos. Filmes tratados a 500oC apresentam nanocristalitos de 10nm, estrutura cassiterita. Os filmes apresentam alto índice de refração e uma porosidade de 26% foi calculada. Guias...
The preparation of the systems doped with lanthanide ions (Eu3+ and Er3+): SnO2, HfO2, organic-inorganic hybrid system containing HfO2, SiO2- HfO2, Ta2O5 and organic-inorganic hybrid system containing Ta2O5, by using the sol gel process, have been the aim of this work. The Results of the colloidal suspension, solids (gel, xerogel and powder) and films are presented. Luminescent SnO2 colloidal suspension, with Eu3+ and Er3+ up to 2 mol%, have been prepared by redispersion of the powder (nanoparticles with modified surface) in a basic aqueous solution. Average diameter of 4 and 6nm were observed to the compounds doped and pure respectivelly, by dynamic light scattering and high resolution transmission electron microscopy. Cassiterite structure is attributed to the crystalline phase of the nanoparticles. Eu3+ ions occupied two different symmetry site. One of them corresponds to the ion in the cassiterite structure, substituting the Sn4+ ions , high symmetry site (D2h or C2h), with a 5D0 lifetime of 6ms; and the second one corresponds to the adsorbed ions on the surface, with a 5D0 lifetime of 0,3 ms. The presence of Eu3+ ions at the surface of the particles hinder their growing and also has allowed the preparation of new materials consisting of water redispersable powders coated with Eu3+-beta diketonate complex. Enhanced UV excited photoluminescence was observed in water. Homogeneous and transparent films were deposited by using the colloidal suspension by spin coating technique. Monolayers up to 200nm were prepared and a linear increase of the thickness value were observed with the concentration of the material and also the number of the layers. Films heat treated at 5000C show nanocrystals of 10nm, cassiterite structure. High ...(Complete abstract, click electronic access below)

APA, Harvard, Vancouver, ISO, and other styles

21

Robotti, Marco. "Functional surfaces obtained by thermal spray techniques." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/400558.

Full text

Abstract:

The main subject of this PhD Thesis is the manufacturing of titanium dioxide multifunctional coatings by means of two spraying technologies: Cold Gas Spray (CGS) and Atmospheric Plasma Spray (APS). The characteristics of each spraying technique are a key factor to be able to understand the behaviour of the deposited material. Moreover, the process conditions strongly affect the functional response and activity of the metal oxide layers in different application sectors. The starting scope of the PhD thesis consisted in developing nanostructured TiO2 anatase coatings by LP-CGS technique. Using this method, no melting of material feedstock is needed for being deposited and this fact is fundamental because it is possible to preserve this metastable active anatase phase at room temperature. The large specific surface of this nanometric feedstock is useful for applying it in the field of heterogeneous photocatalysis and degradation of contaminants. In order to avoid clogging phenomena of the nanometric powder and not suitable deposition of only ceramic particles, mechanical blends were prepared with ductile materials which flow properly in the pipelines. The presence of anatase phase on the top surface of the final coatings determines their photocatalytic behaviour. Samples successfully degraded NOx gases in less than half an hour (FEAM Grupo de Fotocatálisis y Espectroscopia Aplicada al Medioambiente, Universidad de Las Palmas de Gran Canaria). A second research topic regarded different TiO2 materials with the objective to test them in photoelectrocatalysis. Three commercial powders (TiO2 rutile, TiO2 anatase and TiO2-x) onto Inconel alloy and carbon steel substrates were studied. The influence of APS thermally-activating technique is explained towards the non-stoichiometric secondary phases that are formed. The performance of the coatings as photoanodes in the solar photoelectrocatalysis (SPEC) treatment of a model azo dye was explored (Group LEMMA Laboratori d’Electroquímica de Materials i del Medi Ambient, Universitat de Barcelona). The functional role of these materials has an important added value in the environmental field because of the possibility to achieve cleaner waters in the smart cities of the future. The third purpose of this research was to deposit metal oxides based on titanium dioxide by APS for being applied as electrodes in real batteries. Hydrogen contained in the plasma jet of APS is able to reduce TiO2 metal oxide feedstock, create oxygen vacancies and non stoichiometric compounds such as titanium sub-oxides (TiO2-x) or Magnéli phases (TinO2n-1) during the in-flight interaction of the particles with the jet stream. This lack of oxygen in the crystal structure of TiO2 powder leads to a donor level to the conduction band; therefore a corrosion-resistance ceramic material with an enhanced conductivity was obtained. Coatings were manufactured onto stainless steel, aluminium films, carbon-polymer composite and nickel foam. Four TiO2-x plates onto aluminium substrates were applied as electrodes in a laboratory scale battery. Cyclic voltammograms curves and charge/discharge cycle of the lead acid battery were carried out and gave excellent results (Faculty of Engineering and the Environment, University of Southampton). The fourth objective of this doctorate consisted in developing new functional gas sensors by means of APS technology. It was determined to build-up the sensing layer on a thin ceramic substrate. This fact permits to increase the working temperature respect to polymeric or metallic substrates. Spraying conditions were accurately selected to reach good deposition and not to damage the brittle substrate. The APS process offered also the advantage to increase the quantity of oxygen vacancies in titanium dioxide powder in order to enhance its conductivity and sensing function. Satisfactory performances were obtained testing the response of the device in front of various target gases and sensing efficiency was deeply studied (Group MIND Micro-nanotecnologías y nanoscopias para dispositivos electrónicos y fotónicos, Universitat de Barcelona).
El tema principal de esta tesis doctoral es la fabricación de recubrimientos multifuncionales de dióxido de titanio mediante técnica de proyección fría (CGS) y proyección por plasma atmosférico (APS). Cada producto en forma de recubrimiento funcional encontró su sector de aplicación: i) fotocatálisis en fase gaseosa, ii) fotoelectrocatálisis en fase liquida, iii) electrodos para baterías y iv) sensores de gas. El primer objetivo de esta tesis doctoral consistió en el desarrollo de recubrimientos nano-estructurados de TiO2 anatasa mediante técnica de proyección fría CGS. La grande superficie específica de este material nanométrico es útil para su aplicación en el campo de la fotocatálisis heterogénea. Fueron preparadas unas mezclas mecánicas entre materiales nano-cerámicos y poliméricos con adecuada fluidez para el sistema de alimentación CGS. Las muestras obtenidas degradaron los gases NOx en breve tiempo y con elevadas eficiencias tanto con luz UV como con luz visible (FEAM Grupo de fotocatálisis y Espectroscòpia Aplicada al Medioambiente, Universidad de Las Palmas de Gran Canaria). El segundo propósito de esta investigación consistió en proyectar tres diferentes tipos de TiO2 (100% anatasa, 100% rutilo y sub-óxidos) por tecnología APS y evaluar las actividades fotocatalíticas en fase liquida. El rendimiento de los recubrimientos aplicados como fotoánodos fue analizado con el proceso SPEC Solar Photoelectrocatalysis. El estudio llevó a la conclusión que los recubrimientos con mayor parte de fases cristalinas (anatasa y rutilo), mayor rugosidad 3D de superficie y adecuado espesor presentan mejor desempeño fotoelectrocatalítico. (Grupo LEMMA Laboratori d’Electroquímica de Materials i del Medi Ambient, Universitat de Barcelona). La tercera finalidad de este trabajo fue depositar óxidos metálicos por APS para ser aplicados como electrodos en baterías reales. El hidrógeno contenido en el flujo de plasma de APS es capaz de reducir el óxido metálico TiO2 de partida, crear vacantes de oxígeno y compuestos no estequiométricos como sub-óxidos de titanio (TiO2-x) o fases de Magnéli (TinO2n-1). Esta falta de oxígeno aumenta la conductividad del material que además resiste bien contra la corrosión. Fueron fabricados recubrimientos sobre acero inoxidable, láminas de aluminio, material compuesto de polímero reforzado con carbono y espuma de níquel. Cuatro placas de TiO2-x sobre sustratos de aluminio se aplicaron como electrodos en una batería de escala de laboratorio. Se realizaron las curvas de voltametría cíclica y los ciclos de carga/descarga de la batería de plomo y los resultados fueron excelentes (Facultad de Ingeniería y Medio Ambiente, Universidad de Southampton). El último objetivo de este doctorado consistió en el desarrollo de nuevos sensores de gas funcionales a través de la tecnología de APS. Se estableció hacer crecer la capa sensorica sobre un sustrato cerámico delgado para poder aumentar la temperatura de trabajo. Las condiciones de proyección fueron seleccionadas para alcanzar una buena deposición, no dañar el sustrato y aumentar la cantidad de vacantes de oxígeno. La detección fue analizada a diferentes temperaturas de trabajos y los rendimientos fueron satisfactorios (Grupo MIND Micronanotecnologies I Nanoscòpies per Dispositius electrònics i fotònics, Facultad de Física, Universitat de Barcelona).

APA, Harvard, Vancouver, ISO, and other styles

22

Lo, Shih-Chun. "Electroactive materials." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343284.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Tan, Yu-May. "Mesoporous materials." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370067.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Bokun, I. "Simplifying Materials." Thesis, Gorlovka State Pedagogical Institute of Foreign Languages, 2004. http://essuir.sumdu.edu.ua/handle/123456789/63536.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Broderick, Jane Tingle. "Exploring Materials." Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/etsu-works/4225.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Zadorosny, Lincon [UNESP]. "Produção e caracterização de micro e nanofibras de Poli(fluoreto de vinilideno) - PVDF obtidos pela técnica de fiação por sopro em solução." Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/91972.

Full text

Abstract:

Made available in DSpace on 2014-06-11T19:25:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-03-04Bitstream added on 2014-06-13T19:12:23Z : No. of bitstreams: 1 zadorosny_l_me_ilha.pdf: 3393568 bytes, checksum: b39b59b685225b543349760ff3d66599 (MD5)
Nanofibras poliméricas de poli(fluoreto de vinilideno) – PVDF – foram produzidas pela técnica de fiação por sopro em solução (FSS) a partir de soluções de PVDF/N,N, Dimetilformamida – DMF. Foram estudadas as influências da variação da concentração polimérica (15, 20, 25 e 30%, m/v), distância de trabalho (15, 18, 21 e 24 cm), taxa de alimentação (19, 38 e 76 μL/min), e pressão do gás (100, 140 e 180 kPa), sobre a morfologia e diâmetro das nanoestruturas. O diâmetro médio das nanofibras obtidas variou entre 91 e 245 nm. Imagens de MEV apontam que, dentre os parâmetros estudados, o que promoveu maior alteração morfológica das nanofibras foi a concentração polimérica, fator diretamente relacionado à viscosidade da solução. A variação dos demais parâmetros promoveu menores alterações tanto estruturais quanto morfológicas nos filmes nanofibrosos. Análises termogravimétricas (TGA) revelaram que os filmes são termicamente estáveis até uma temperatura de 420 °C. Difratometria de raios X (DRX) indicaram a presença das fases cristalinas α e β, sendo a fase β mais evidenciada para as nanofibras e PVDF casting. O filme obtido por FSS apresentou maior ângulo de contato, demostrando ser mais hidrofóbico. Ensaios de tensão deformação mostraram que os filmes nanofibrosos apresentaram uma deformação até a ruptura de 72%, cerca de 1,7 e 3,1 vezes maior que os obtidos por casting e prensagem a quente, respectivamente. Verificou-se também um decréscimo no módulo de elasticidade e do limite de resistência à tração das nanofibras, comparativamente aos outros filmes
Poly(vinylidene fluoride) – PVDF Nanofibers were produced by solution blow spinning technique (SBS) from solutions PVDF/N,N, Dimethylformamide – DMF. It was investigated the influence of the polymeric concentration (15, 20, 25 e 30% w/v), work distance (15, 18, 21 and 24 cm), feed rate (19, 38 e 76 μL/min), and gas pressure (100, 140 e 180 kPa), on the morphology of the nanostructure and diameter of the nanofibers. The average diameter of the obtained nanostructure was on the range 91 - 245 nm. SEM images show that, among the studied parameters, the concentration of the solution promoted the grater changes in the morphology of the polymer nanofibers. Such factor is directly related to the viscosity of the solution. Variation of the other parameters promoted both structural and morphological changes in the nanofiber films. Termograviometric analyses showed that the films are thermally stable up to 420°C. X-ray diffraction (XRD) indicated the presence of the crystalline phases α and β. However, the β phase is more evident in the nanofibers and in the PVDF casting. The films obtained by SBS showed higher contact angle, which means that they are more hydrophobic. Stress-strain tests showed that nanofiber films had a break deformation of 72%, approximately 1.7 and 3.1 times higher than those obtained by casting and hot pressing, respectively. There was also a decrease in the elastic modulus and in the tensile strength of the PVDF nanofibers when compared with the other films

APA, Harvard, Vancouver, ISO, and other styles

27

Zadorosny, Lincon. "Produção e caracterização de micro e nanofibras de Poli(fluoreto de vinilideno) - PVDF obtidos pela técnica de fiação por sopro em solução /." Ilha Solteira, 2013. http://hdl.handle.net/11449/91972.

Full text

Abstract:

Orientador: Luiz Francisco Malmonge
Banca: Walter Katsumi Sakamoto
Banca: Antonio Riul Júnior
Resumo: Nanofibras poliméricas de poli(fluoreto de vinilideno) - PVDF - foram produzidas pela técnica de fiação por sopro em solução (FSS) a partir de soluções de PVDF/N,N, Dimetilformamida - DMF. Foram estudadas as influências da variação da concentração polimérica (15, 20, 25 e 30%, m/v), distância de trabalho (15, 18, 21 e 24 cm), taxa de alimentação (19, 38 e 76 μL/min), e pressão do gás (100, 140 e 180 kPa), sobre a morfologia e diâmetro das nanoestruturas. O diâmetro médio das nanofibras obtidas variou entre 91 e 245 nm. Imagens de MEV apontam que, dentre os parâmetros estudados, o que promoveu maior alteração morfológica das nanofibras foi a concentração polimérica, fator diretamente relacionado à viscosidade da solução. A variação dos demais parâmetros promoveu menores alterações tanto estruturais quanto morfológicas nos filmes nanofibrosos. Análises termogravimétricas (TGA) revelaram que os filmes são termicamente estáveis até uma temperatura de 420 °C. Difratometria de raios X (DRX) indicaram a presença das fases cristalinas α e β, sendo a fase β mais evidenciada para as nanofibras e PVDF casting. O filme obtido por FSS apresentou maior ângulo de contato, demostrando ser mais hidrofóbico. Ensaios de tensão deformação mostraram que os filmes nanofibrosos apresentaram uma deformação até a ruptura de 72%, cerca de 1,7 e 3,1 vezes maior que os obtidos por casting e prensagem a quente, respectivamente. Verificou-se também um decréscimo no módulo de elasticidade e do limite de resistência à tração das nanofibras, comparativamente aos outros filmes
Abstract: Poly(vinylidene fluoride) - PVDF Nanofibers were produced by solution blow spinning technique (SBS) from solutions PVDF/N,N, Dimethylformamide - DMF. It was investigated the influence of the polymeric concentration (15, 20, 25 e 30% w/v), work distance (15, 18, 21 and 24 cm), feed rate (19, 38 e 76 μL/min), and gas pressure (100, 140 e 180 kPa), on the morphology of the nanostructure and diameter of the nanofibers. The average diameter of the obtained nanostructure was on the range 91 - 245 nm. SEM images show that, among the studied parameters, the concentration of the solution promoted the grater changes in the morphology of the polymer nanofibers. Such factor is directly related to the viscosity of the solution. Variation of the other parameters promoted both structural and morphological changes in the nanofiber films. Termograviometric analyses showed that the films are thermally stable up to 420°C. X-ray diffraction (XRD) indicated the presence of the crystalline phases α and β. However, the β phase is more evident in the nanofibers and in the PVDF casting. The films obtained by SBS showed higher contact angle, which means that they are more hydrophobic. Stress-strain tests showed that nanofiber films had a break deformation of 72%, approximately 1.7 and 3.1 times higher than those obtained by casting and hot pressing, respectively. There was also a decrease in the elastic modulus and in the tensile strength of the PVDF nanofibers when compared with the other films
Mestre

APA, Harvard, Vancouver, ISO, and other styles

28

Andrade, Marco Aurélio Brizzotti. "Análise de materiais piezelétricos compósitos para aplicações em transdutores de ultra-som." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-08052006-154724/.

Full text

Abstract:

O objetivo deste trabalho é analisar materiais piezelétricos compósitos com conectividade 1-3 e 2-2 para aplicações em transdutores de ultra-som na faixa de MHz utilizando modelos matemáticos e verificações experimentais. O estudo de um material piezelétrico compósito pode ser feito através de seus três principais tipos de modos de vibração: modo planar, modo de espessura e modo lateral. Neste trabalho, é utilizado o método dos elementos finitos para modelar os modos planares, de espessura e laterais de um compósito, e modelos analíticos para modelar o modo de espessura e o modo lateral. A modelagem do modo de espessura de um transdutor de ultra-som é feita a partir de um modelo analítico unidimensional. A modelagem unidimensional de um transdutor de ultra-som é feita através do cálculo das propriedades efetivas do material piezelétrico compósito. Essas propriedades são utilizadas no modelo da matriz distribuída para prever a impedância elétrica de um compósito e a resposta impulsiva de um transdutor de ultra-som. Com o objetivo de validar os modelos, foram construídos um material piezelétrico compósito com conectividade 1-3 e outro com conectividade 2-2 através da técnica dice-and-fill, utilizando cerâmica de PZT-5A e resina epóxi. O compósito com conectividade 1-3 foi utilizado na construção de um transdutor de ultra-som. Os resultados teóricos da impedância elétrica e da resposta impulsiva são comparados com os obtidos experimentalmente. A impedância elétrica experimental é obtida através de um analisador de impedâncias, enquanto que a resposta impulsiva experimental do eco do transdutor é medida acoplando o protótipo do transdutor a um tarugo de acrílico. Devido à periodicidade do compósito foi feito um estudo teórico da propagação de ondas mecânicas em meios periódicos, mostrando que existem determinadas faixas de freqüências que não se propagam no material. Foi verificado que esta periodicidade é responsável pela diminuição das amplitudes dos modos radiais de um material piezelétrico compósito quando comparados com os modos radiais de um disco de cerâmica piezelétrica. Também foram feitos ensaios em tanque de imersão para determinar as propriedades mecânicas de amostras de epóxi e amostras de tungstênio e epóxi em função da fração de volume de tungstênio na amostra.
The objective of this work is to analyze piezoelectric composite materials with 1-3 and 2-2 connectivity for applications in ultrasonic transducers in the megahertz frequency range. The analysis is done through mathematical models and experimental validation. The analysis of piezoelectric composite materials can be done through the study of its three main vibrational modes: planar mode, thickness mode, and the lateral mode. In this work, it is used the Finite Element Method to model the planar, thickness and the lateral modes of the composite, and it is used analytical models to model the thickness and the lateral modes. The modeling of the thickness mode of an ultrasonic transducer is obtained through an unidimensional analytical model. The unidimensional modeling of the transducer is done by calculating the effective properties of the piezoelectric composite material. The effective properties are used in a distributed matrix model to calculate the electrical impedance of the composite and the impulse response of an ultrasonic transducer. To validate the models, a 1-3 and a 2-2 piezoelectric composite were built using the dice-and-fill technique. These composite were constructed using a piezoelectric ceramic of PZT-5A and epoxy. The piezoelectric composite with 1-3 connectivity was used in the fabrication of an ultrasonic transducer. The theoretical results of the electrical impedance and the impulse response are compared with the experimental results. The experimental electrical impedance is measured by using an impedance analyzer, and the experimental impulse response is measured by coupling the ultrasonic transducer prototype to an acrylic block. Due to the periodicity of the composite, it was analyzed the behaviour of mechanical waves in periodic media, showing that there are frequency ranges that the waves cannot propagate. It was verified that the periodicity is responsible for the suppression of the radial modes in a piezoelectric composite when compared with the radial modes of a disk of piezoelectric ceramic. It is also conducted measurements in a water filled tank to determine the mechanical properties of samples of epoxy, and Tungsten/epoxy composites as a function of the volume fraction of Tungsten.

APA, Harvard, Vancouver, ISO, and other styles

29

Sakahara, Rogério Massanori. "Estudo da formação da fase cristalina beta nos compósitos de polipropileno contendo anidrido maléico e carbono de cálcio." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-04072013-153850/.

Full text

Abstract:

Este trabalho estuda a influência do carbonato de cálcio (CaCO3) nas propriedades mecânicas e na formação da fase cristalina beta do polipropileno (PP). Com o intuito de produzir amostras para o estudo, foi feita uma análise preliminar sobre o enxerto do anidrido maléico no polipropileno, porque este material graftizado (PP-g-MA) contribui significativamente em blendas e compósitos ao melhorar a adesão superficial entre o PP e o CaCO3. Foram estudados dois métodos de obtenção deste produto (PP-g-MA) utilizando-se peróxido orgânico e os produtos obtidos foram caracterizados e comparados. Apesar dos resultados das análises feitas por calorimetria diferencial exploratória (DSC), análise termogravimétrica (TGA), microscopia eletrônica de varredura (MEV) e espectroscopia de energia dispersiva (EDS) indicarem importantes diferenças entre os dois métodos, a análise por espectroscopia no infravermelho (FTIR) trouxe conclusões sobre a eficácia dos métodos de graftização. Duas séries de compósitos a base de PP contendo CaCO3 foram produzidos por mistura intensiva em fusão (misturador Drais), uma contendo PP-g-MA e a outra sem. Quatro tipos de CaCO3 foram utilizados, diâmetros de 0,9 µm, 2,5 µm e 3 µm, sendo que o CaCO3 0,9 µm apresentou-se com superfície tratada e não-tratada. A concentração de CaCO3 foi mantida em 5% e a de PP-g-MA em 5% quando presente. Os compósitos foram submetidos a testes de resistência à tração, módulo na flexão e resistência ao impacto em duas temperaturas. As amostras contendo menores tamanhos de partículas de CaCO3 e PP-g-MA apresentaram melhora sinérgica na resistência mecânica, em que aumentos da resistência a impacto e da resistência a flexão foram observados. A análise da fase cristalina beta nestas amostras foi feita utilizando-se DSC e difratometria de raios-x. Também foi analisada a influência da adesão superficial entre a carga e a matriz de PP, quanto maior a adesão superficial e menor o tamanho de partícula do CaCO3, maior a formação da fase cristalina beta, o que contribuiu para a sinergia entre todas as propriedades mecânicas avaliadas neste trabalho.
This study aimed at improving the comprehension of the influence of calcium carbonate (CaCO3) in the formation of the beta crystalline phase of polypropylene (PP), as well as the changes in the mechanical properties of this polymer. A preliminary analysis of the grafting of the maleic anhydride in the polypropylene was carried out in order to produce specimens for the study, owing to the fact that this grafted polypropylene (PP-g-MA) contributes substantially to change the polarity of the polymer and therefore, enhance the superficial adhesion between PP and CaCO3. Two grafting methods using organic peroxide were studied. The grafted copolymers were analyzed by DSC, TGA, SEM, EDS, and FTIR. Two series of PP composites containing CaCO3 were produced by intensive melt mixing (Drais mixer), one of them having MA-g-PP. Four types of CaCO3 were used, which diameters were 0.9 µm, 2.5 µm and 3 µm, though the CaCO3 0.9 µm was surface-treated and non-treated. The concentration of CaCO3 was maintained at 5% and PP-g-MA at 5 % also, when present. The composites were tested for tensile strength, flexural modulus and impact strength (at two temperatures). Samples containing smaller particle sized CaCO3 and PP-g-MA showed synergistic improvement in the mechanical strength, and increases in the impact resistance and flexural strength were observed. Analysis of the beta crystal phase in these samples was performed using DSC and x-ray diffractometry. The influence of superficial adhesion between CaCO3 and PP was also analyzed, higher concentration of the beta crystalline phase was observed for better surface adhesion and smaller CaCO3 particle size, which contributed to the synergy between all the mechanical properties evaluated in this work.

APA, Harvard, Vancouver, ISO, and other styles

30

Prazzo, Carlos Eduardo [UNESP]. "Análise modal de uma estrutura do tipo viga utilizando materiais piezelétricos (PVDF) como sensores." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/94521.

Full text

Abstract:

Made available in DSpace on 2014-06-11T19:27:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-09-26Bitstream added on 2014-06-13T20:35:23Z : No. of bitstreams: 1 prazzo_ce_me_ilha.pdf: 1585012 bytes, checksum: 3ddb6b2bb4fddee99d49636888c24ded (MD5)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Esse trabalho discute o uso dos materiais piezelétricos, mais especificamente, o Polyvinylidene Fluoride (PVDF) e o Lead Zirconate Titatane (PZT) na análise modal experimental (AME) de estruturas mecânicas. Materiais piezelétricos, também chamados de materiais inteligentes, têm se consolidado como uma nova tecnologia que mostra um grande potencial de aplicação em diferentes áreas da engenharia. Esse tipo de material exibe um acoplamento entre multi-domínios físicos, como por exemplo o acoplamento eletro-mecânico, o térmo-magnético, etc. O acoplamento eletro-mecânico produz um deslocamento elétrico quando o material é sujeito a uma tensão mecânica (efeito direto) e um deformação mecânica quando esse material é submetido a um campo elétrico (efeito inverso). Assim, principalmente por conta desses efeitos, seu uso no campo da análise modal experimental torna-se uma interessante questão a ser investigada. A incorporação de novas tecnologias nos testes estruturais pode agregar novos conhecimentos e avanços tanto na análise modal baseada na relação entrada-saída da estrutura, quanto na mais recente técnica, a análise modal baseada apenas na resposta das mesmas. Os conceitos teóricos para o desenvolvimento são apresentados e discutidos neste trabalho, onde é mostrada a análise modal de uma viga utilizando tanto sensores e atuadores convencionais quanto os produzidos com materiais inteligentes. Os testes de análise modal da viga foram feitos utilizando diferentes combinações de sensores e atuadores e isso pode mostrar as diferenças da estimativa de modos utilizando materiais piezelétricos. Também é apresentada a formulação da relação entre os modos em deslocamento e os modos com diferença de inclinação obtidos com materiais piezelétricos e, finalmente, uma comparação dos resultados obtidos pelas diferentes técnicas. Os testes apresentados mostram...
This work discusses the use of piezoelectric materials, more specifically, Polyvinylidene Fluoride (PVDF) and Lead Zirconate Titanate (PZT) for experimental modal analysis (EMA) of mechanical structures. Piezoelectric materials also called smart materials have becoming a consolidated new technology that shows a large potential of application for different engineering areas. These materials exhibit a multi physics domain field coupling like mechanical and electrical coupling domains, thermal and magnetic coupling and etc. The electro-mechanical coupling domains of the material produces an electric displacement when the material is subject to a mechanical stress (direct-effect) and a mechanical strain when the material is submitted to an electric field (inverse effect). So, mainly due to these effects, the use in the experimental modal analysis field appears to be an interesting issue to be investigated. The incorporation of this new technology in the structural tests might aggregate new acknowledgments and advances in the well consolidated input-output based modal analysis techniques as well as in the more recent output only-based modal analysis. This work aims to present some contribution in this area by using piezoelectric sensors, instead of the conventional ones like accelerometers for modal analysis of mechanical structures. The theoretical concepts and background for the developing of the work are presented and discussed, it is also presented the modal analysis of a beam like structure using conventional sensors/actuators and piezoelectric materials. The modal analysis tests of the beam are conducted using different kinds of sensors/actuator and they give some insight of the difference of the estimated modes shapes by using piezoelectric materials. It is also presented a formulation that shows the relation between... (Complete abstract click electronic access below)

APA, Harvard, Vancouver, ISO, and other styles

31

Ogwuda, Olisanwendu Ikechukwuka. "Materials science appraisal of recycled construction materials for roadways." Thesis, Abertay University, 2007. https://rke.abertay.ac.uk/en/studentTheses/70d295b3-60d9-427e-a012-c9cc05ac83e1.

Full text

Abstract:

This thesis reports on a materials science appraisal for recycled construction materials in roadways, that supports engineering decision-making. Inconsistent performance criteria for roadway materials and the variable nature of material source have prompted the need for this research. The aim of the study is to investigate the application of a materials science appraisal to recycled construction materials for use in roadways. The investigation is undertaken through a literature review of roadways, conceptual development of the materials science appraisal methodology, and demonstration of the application of the materials science appraisal to recycled construction materials; and how this supports engineering decision-making. The literature review revealed that there are numerous and proven uses of recycled and secondary materials in roadway applications but there was a lack of necessary integration of materials into categories by material-type, which can better describe behaviour in an engineering situation. Three novel fundamental material types (ceramic, metallic, and polymeric) have been described. The conceptual development of the innovative and novel materials science appraisal, based on material-type, has defined how materials science through a systematic step-by-step procedure can be used to achieve engineering sustainability in roadways and provide support in engineering decision-making. The application of the novel concept of the materials science appraisal to recycled construction materials is shown through the essence of laboratory testing. The results from the materials science appraisal, together with sensitivity analysis, give an informed engineering decision on product choice. The appraisal is novel in that it is proposing a new theory on materials science and developed a paradigm shift in the evaluation of recycled construction materials. The appraisal overcomes the absence of materials science thinking in the field of roadway engineering. The materials science appraisal is of benefit to various stakeholders (client, consultant, supplier and contractor) as it provides a method for addressing material uncertainties. A system now exists for introducing into designs and any contract the principles of the materials science appraisal that will be of great benefit to industry.

APA, Harvard, Vancouver, ISO, and other styles

32

Sato, Fernando Luís. "Uso de ensaios de microesclerometria instrumentada no estudo das propriedades da austenita expandida." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-25032015-120024/.

Full text

Abstract:

A excelente resistência à corrosão dos aços inoxidáveis austeníticos é a principal característica de sua ampla gama de aplicações nas mais diversas indústrias. Entretanto, as limitadas propriedades mecânicas da austenita, restringem o uso dessas ligas em sistemas que requeiram melhor desempenho tribológico sem prejuízo de sua resistência à corrosão. Métodos de endurecimento superficial convencionais tendem a formar precipitados que reduzem a disponibilidade dos elementos responsáveis pela passivação da liga, favorecendo a ação de agentes corrosivos. A descoberta de uma fase supersaturada em intersticiais denominada austenita expandida, ou Fase-S, tem lançado novas perspectivas sobre as opções de endurecimento superficial dos aços inoxidáveis austeníticos. Produzida por modernas técnicas baseadas no emprego do plasma, a austenita expandida apresenta elevadíssima dureza, da ordem de 14 GPa, sem prejuízo de sua resistência à corrosão, uma vez que não ocorre precipitação observável por microscopia ótica ou de varredura. Caracterizações mecânicas das camadas de austenita expandida por ensaios que simulem situações mais próximas da real condição de trabalho do material fornecem um conjunto de dados empíricos relevantes para a compreensão e modelagem de fenômenos tribológicos atuantes em um dado sistema mecânico. Nesse sentido, a microesclerometria instrumentada aparece com excelente opção de ferramenta para os estudos direcionados à Engenharia de Superfície. O presente trabalho apresenta os resultados de uma série de ensaios de microesclerometria instrumentada realizados em amostras de aço AISI 316 nitretadas a plasma por 20 h em forno de corrente contínua, utilizando a tecnologia de tela ativa, temperatura de 400 ºC e atmosfera formada por três partes de nitrogênio para cada parte de hidrogênio (3N2:1H2), resultando na formação de austenita expandida na superfície. Também são discutidos a caracterização das amostras, o baixo coeficiente de atrito (< 0,1) verificado experimentalmente e a ausência de falha adesiva da camada durante o ensaio.
One of the main reasons for the common utilization of austenitic stainless steels by various industries remains on their great corrosion resistance. On the other hand, the poor mechanical properties of austenite restrict the use of these alloys in systems which require better tribological performance without decreasing their corrosion resistance. Conventional case hardening techniques promote precipitate formation, reducing availability of passivation elements in metallic matrix, what can ease the action of corrosive external agents. The discovery of a carbon and/or nitrogen supersaturated phase, called expanded austenite or S-phase, brought new perspectives over case hardening options for austenitic stainless steels. Obtained by recent techniques based on plasma, expanded austenite has very high hardness, around 14 GPa, without reducing corrosion resistance, since no precipitate is noticeable by optical or scanning electronic microscopy. Using testing apparatus that simulates real work conditions, mechanical characterization of expanded austenite layers gives an important set of empirical data. These data are useful for comprehension and modeling of tribological phenomena occurring in a given mechanical system. In this way, instrumented microscratch test appears as an interesting option to be used in studies oriented to the Surface Engineering field. This work presents results from a series of instrumented microscratch tests performed over AISI 316 stainless steel samples with an expanded austenite layer. Plasma nitriding surface treatment was carried out during 20 h, in an active screen DC reactor under 400 ºC and atmosphere compounded by three parts of nitrogen for each part of hydrogen (3N2:1H2). The tribological behavior of the expanded austenite layer was characterized in a series of linear scratch tests. The results show that in the beginning of the scratch test the coefficient of friction was kept smaller than 0,1. When the first cracks appear the apparent coefficient of friction steadily increases, indicating that cracking of the nitrided layer lead to an increase of the coefficient of friction. Although the expanded austenite layer cracks, no adhesive failure was observed, the hardened layer being preserved during the whole scratch test.

APA, Harvard, Vancouver, ISO, and other styles

33

Sie, Jason. "An evaluation of manual materials handling of drywall materials using drywall carts at Tamarack Materials, Inc." Menomonie, WI : University of Wisconsin--Stout, 2006. http://www.uwstout.edu/lib/thesis/2006/2006siej.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Kuhn, William B. "Design of Integrated, Low Power, Radio Receivers in BiCMOS Technologies." Diss., Blacksburg, VA : Scholarly Communications Project, 1995. http://scholar.lib.vt.edu/theses/materials/kuhn.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Wiedenman, Nathan Scott. "Towards programmable materials : tunable material properties through feedback control of conducting polymers." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45889.

Full text

Abstract:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.
Includes bibliographical references (p. 159-168).
Mammalian skeletal muscle is an amazing actuation technology that can controllably modify its force and position outputs as well as its material properties such as stiffness. Unlike muscle, current engineering materials are limited by their intrinsic properties, dictated at the molecular level.This work is focused on developing an integrated device, called a programmable material, which mirrors the capabilities of natural co-fabricated controlled actuation systems such as muscle. While such a device may have the external appearance of a homogeneous material, it can possess unique properties not existing in any currently manufactured material. When actuation, sensing, and control capabilities are integrated within a closed-loop system, the mechanical properties of the system such as stiffness, viscosity, and inertia will arise from the dynamics of the feedback loop rather than from any inherent mechanical properties of the materials from which the device was fabricated. Moreover, these properties may be 'tuned' by altering the feedback parameters embedded in the material system. With this approach properties such as negative stiffness may be generated which do not exist in bulk materials.The most promising of the existing artificial muscle technologies is actuation with conducting polymer. Additionally, conducting polymer has been used to fabricate the position sensor and control electronics. Creating these components from a single type of material has made it possible to co-fabricate the system into an integrated device. This is the first research to attempt to create a co-fabricated, fully integrated conducting polymer feedback device. This work establishes the feasibility of building the device and answers many of the questions of fabrication and design.
by Nathan Scott Wiedenman.
Ph.D.

APA, Harvard, Vancouver, ISO, and other styles

36

Andrade, Gracielle Ferreira. "Funcionalização de sílica mesoporosa para aplicação em sistemas de liberação controlada de fármacos." CNEN - Centro de Desenvolvimento da Tecnologia Nuclear, Belo Horizonte, 2011. http://www.bdtd.cdtn.br//tde_busca/arquivo.php?codArquivo=145.

Full text

Abstract:

Nenhuma
Materiais mesoporosos ordenados tipo SBA-16 possuem uma rede de canais e poros de tamanho bem definido na escala nanométrica, com estrutura cúbica, elevada área superficial (400 1000 m2.g-1) e tamanho de poros usualmente em torno de 2 a 30 nm. Essa estrutura de poros torna esses materiais apropriados para incorporar e liberar uma grande variedade de moléculas na sua matriz. Dentre os diversos tipos de materiais SBA, o SBA-16 é considerado uma mesoestrutura muito interessante devido ao fato de possuir um ordenamento de mesoporos cúbico tridimensional correspondente ao grupo especial Im3m, podendo ser um material promissor para várias aplicações. Os materiais mesoporosos podem sofrer diversas modificações na sua superfície, devido à presença dos grupos silanóis, podendo produzir um material com uma funcionalidade direcionada. Neste trabalho, estudou-se a síntese e caracterização do material SBA-16 puro e após o processo de funcionalização para avaliar sua aplicação como sistema de liberação controlada de um fármaco modelo. O processo de modificação da superfície foi realizado pelo método pós-síntese, ou seja, após o obter o material SBA-16, esse passou por um segundo processo para se obter as amostras funcionalizadas. A caracterização do SBA-16 puro e funcionalizado foi feita por análise elementar (CHN), Espectroscopia na Região do Infravermelho com Transformada de Fourier (FTIR), Análise Termogravimétrica (TG), Adsorção de Nitrogênio, Microscopia Eletrônica de Varredura (MEV), Microscopia Eletrônica de Transmissão (MET), Espalhamento de Raios X a Baixos Ângulos (SAXS), e Ressonância Magnética Nuclear (RMN). Por meio da técnica de espectroscopia de absorção na região do infravermelho, foi possível observar, a partir dos espectros das amostras funcionalizadas, bandas características das vibrações da rede de sílica, bem como bandas referentes às vibrações dos grupos alquilas ancorados na estrutura da sílica. A presença do fármaco atenolol no material mesoporoso e nas amostras funcionalizadas também pode ser confirmada por meio das medidas de FTIR. A estabilidade térmica e as degradações que ocorrem nos componentes puros, bem como nas amostras modificadas na superfície, foram investigadas e estabelecidas pela análise termogravimétrica. Por meio da TG foi possível quantificar a presença dos grupos orgânicos ancorados nesse material. A presença dos grupos orgânicos conduziu a alterações na estrutura do material final, com a diminuição da área superficial e volume de poros. Porém, a distribuição de poros se mostrou semelhante em todas as amostras. Os resultados de MEV, MET e SAXS do SBA-16 e das amostras funcionalizadas revelaram uma estrutura bem ordenada de mesoporos, característica intrínseca desses materiais. Por meio das medidas de ressonância magnética nuclear de 29Si e 13C de estado sólido (RMN-MAS) nas amostras funcionalizadas, foi possível caracterizar e avaliar a forma de ligação desses grupos orgânicos na matriz de sílica. Através do ensaio de liberação, foi possível avaliar a quantidade de atenolol incorporado e verificar o comportamento da liberação desse nas amostras sintetizadas. Com os resultados de citotoxicidade foi possível determinar a viabilidade celular, obtendo-se resultados satisfatórios para uma futura aplicação clínica desse material.
Type ordered mesoporous materials SBA-16 have a network of channels and well defined pore size in nanometer scale. Cubic structure has a high surface area (400 - 1000m2.g-1) and pore size is usually around 20 to 30 nm. This porous structure makes these materials appropriate to incorporate and release a large variety of molecules in the matrix. Among these SBA-type silica materials, SBA-16 is considered a very interesting mesostructure due to the its 3D cubic arrangement of mesopores corresponding to the Im3m space group, a promising material for a large range of applications. The mesoporous materials may undergo several changes in its surface due to the presence of silanol groups, which can produce a material with a targeted feature. The materials were characterized by elemental analysis (CHN), Fourier Transform Infrared Spectroscopy (FTIR), Nitrogen Adsorption, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Small Angle X Ray Scattering (SAXS), Nuclear Magnetic Resonance (RMN), and Thermal Analysis. Through the FTIR analysis technique, it was possible to observe characteristic bands of the silica vibrations, as well as vibrations bands due the presence of alkyl groups anchored into the silica structure. The presence of the atenolol in the mesoporous material and functionalised samples was also confirmed by FTIR. The thermal stability and the degradation of the surface modified samples were determined by thermogravimetry. The incorporation of the organic groups into the mesoporous silica led to a significant change in the structural properties of the system, with the decrease of the specific surface area and pore volume, but the pore size distribuition was similar in all samples. The results obtained by SEM, TEM and SAXS for the samples reveal a well-defined cubic arrangement of uniform mesoporous structure, intrinsic characteristic of these materials. By measuring nuclear magnetic resonance of 29Si and 13C solid state (MAS-NMR) in the functionalized samples, it was possible to characterize and measure the extent of binding of organic groups in the silica matrix. Through the release assay was possible to evaluate the amount of embedded atenolol and verify the behavior of the drug release from the synthesized samples. Considering the results of cytotoxicity, it was possible to determine cell viability by obtaining satisfactory results for future clinical application of this material.

APA, Harvard, Vancouver, ISO, and other styles

37

Rovani, Suzimara. "Modificação da superfície de poliestireno por imersão em plasma para inibição da staphylococcus epidermidis." reponame:Repositório Institucional da UCS, 2011. https://repositorio.ucs.br/handle/11338/624.

Full text

Abstract:

Materiais poliméricos, como o poliestireno, são largamente usados como biomateriais, tanto na área biomédica como na indústria farmacêutica. Com a especialização do uso destes biomateriais, relata-se um aumento significativo de doenças relacionadas à presença de biofilmes bacterianos na superfície destes materiais. Neste trabalho, placas de microtitulação de poliestireno foram tratadas por imersão em plasma-RF, na mistura padrão N2/H2, a fim de avaliar as modificações superficiais geradas, e a eficiência deste processo na adesão e crescimento de biofilme, produzido pela Staphylococcus epidermidis. A identificação de espécies atômicas e grupos funcionais incorporados à superfície do polímero pelo processo de imersão em plasma, foi realizada pelas técnicas de espectroscopia de fotoelétrons excitados por raios X (XPS) e espectroscopia no infravermelho por refletância total atenuada (ATR-IR). Modificações na morfologia e rugosidade da superfície de PS foram avaliadas por microscopia eletrônica de varredura (SEM) e microscopia de força atômica (AFM). A hidrofílicidade da superfície foi analisada por medida de ângulo de contato com água (WCA). Para avaliar a eficiência do tratamento em plasma no crescimento/aderência de biofilme formado pela S. epidermidis foram realizados ensaios de antibiofilme bacteriano. Modificações físico-químicas foram observadas na superfície das amostras por XPS, onde foi constatado o aumento da porcentagem atômica relativa de N e a presença de novas ligações químicas com o aumento do tempo de tratamento. Pela técnica de ATR-IR foi possível identificar a presença de grupos amina e amida. As medidas de microscopia revelaram uma mudança na morfologia e uma redução da rugosidade superficial com o aumento do tempo, e também verificado um aumento do caráter hidrofílico na superfície por WCA. Além disso, a partir de 60 min de tratamento foi alcançada uma alta supressão de adesão de biofilme à superfície do polímero.
Submitted by Marcelo Teixeira (mvteixeira@ucs.br) on 2014-06-05T18:11:48Z No. of bitstreams: 1 Dissertacao Suzimara Rovani.pdf: 2304362 bytes, checksum: bd3491b4311506e651f251ccd00326df (MD5)
Made available in DSpace on 2014-06-05T18:11:48Z (GMT). No. of bitstreams: 1 Dissertacao Suzimara Rovani.pdf: 2304362 bytes, checksum: bd3491b4311506e651f251ccd00326df (MD5)
Polymeric materials, such as polystyrene, are widely used as biomaterials, both in the pharmaceutical industry and biomedical areas. With the use of more specialized biomaterials, it is reported a significant increase of diseases related to the presence of bacterial biofilms formation on the surface of these materials. In this work, polystyrene microtiter plates were treated by RF plasma immersion, in a N2/H2 standard gas mixture, in order to evaluate the surface modifications and its effects on the adherence and growth of bacterial biofilms produced by Staphylococcus epidermidis. The identification of atomic species and functional groups incorporated into the polymer surface by plasma immersion process was carried out by the techniques of X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance infrared spectroscopy (ATR-IR). The changes in morphology and surface roughness of PS were evaluated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The hydrophilicity of the surface was analyzed by measuring the water contact angle (WCA). Bacterial antibiofilm assays were carried out in order to evaluate the efficiency of plasma treatment on the growth/adherence of the biofilm formed by S. epidermidis. Physical-chemical modifications in the samples surface were found by XPS technique, where an increase in amount of relative atomic percentage of N and the presence of new chemical bonds was observed as a function of the treatment time. Through the ATR-IR spectroscopy was possible to identify the presence of amine and amide groups. The SEM and AFM measurements revealed changes in morphology and a reduction of the surface roughness with increasing time. It is also observed a reduction in the WCA after plasma treatment, indicating that PS surface becomes more hydrophilic. Antibacterial assays, shows that after 60 min of treatment time was achieved a high suppression of biofilm adhesion in the polymer surface.

APA, Harvard, Vancouver, ISO, and other styles

38

Murakami, Regina Keiko. ""Novos materiais magnéticos para imãs de alta performance"." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-14022006-182556/.

Full text

Abstract:

O objetivo do presente trabalho foi desenvolver novos materiais magnéticos para ímãs de alta performance. Duas classes de materiais foram estudadas: materiais a base de (Nd,Sm)5(Fe,MT)17, onde MT é um metal de transição, e materiais nanocristalinos a base de (Nd,Pr)FeB com adições de TiC. As ligas (Nd,Sm)5(Fe,MT)17 foram preparadas por fusão em forno de arco e posteriormente foram tratadas termicamente por longos períodos (no mínimo 30 dias). Tentamos melhorar as propriedades magnéticas por meio de substituições químicas (Ti, Co, Mn, etc.) e/ou por introdução intersticial de deutério ou nitrogênio. As amostras foram caracterizadas via análise termomagnética (TMA), magnetometria de baixas temperaturas, difração de raios X e de nêutrons, e espectroscopia Mössbauer. Os principais resultados foram: a) aumento de Tc de até 70 º C; b) localização dos átomos de deutério na redecristalina. Ligas de (Nd,Pr) com adição de TiC foram preparadas por fusão de arco, sendo processadas via "melt spinning" e passando por tratamentos térmicos variados. Os promissores resultados na literatura para Nd2Fe14B+TiC foram obtidos também para Pr2Fe14B + TiC, mas não para os sistemas compostos pela fase φ e Fe3B com TiC. Porém, bons resultados foram obtidos em sistemas compostos pelas fases φ e αFe, com aumento de até 30% nos valores de campo coercivo Hc e aumentos de até 15% de (BH)max.
The aim of the present work was to develop new improved magnetic materials suitable for permanent magnets. Two kinds of materials were studied: (Nd,Sm)5(Fe,MT)17 based materials, were MT is a transition metal and, (Nd,Pr)FeB nanocrystalline materials (exchange spring magnets) with TiC additions. The 5:17 alloys were melted in an arc melting furnace followed by a long annealing (at least 30 days). We tried to improve the magnetic properties by means of chemical substitutions (Ti, Co, Mn, etc.) and/or by addition of interstitial atoms of deuterium or nitrogen. The samples were characterized by means of thermomagnetic analysis (TMA), low temperature magnetometry, X ray and neutron diffraction, and Mössbauer spectroscopy. The main results were: a) increase of Tc temperature (up to 70 ºC) and; b) determination of interstitial sites for deuterium. (Nd,Pr)FeB alloys with TiC additions were melted in an arc melting furnace, being processed in a melt spinner system. After the samples were heat treated at different temperatures. The promissing literature results for Nd2Fe14B+TiC were also obtained for Pr2Fe14B + TiC, but not for systems composed by Pr2Fe14B and Fe3B phases with TiC additions. However, good results were obtained in systems composed by Pr2Fe14B and α-Fe with TiC additions, with 30% increase on coercive field values Hc, and 15% increase on (BH)max.

APA, Harvard, Vancouver, ISO, and other styles

39

Nicolodelli, Gustavo. "Investigação de ablação a laser no regime de femtossegundo em materiais homogêneos e estruturados." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-25052011-162657/.

Full text

Abstract:

Embora a ablação a laser venha sendo bastante utilizada em materiais em geral, pouco é entendido sobre o comportamento deste processo perto de uma interface separando dois materiais distintos. Neste contexto, o principal objetivo deste trabalho foi realizar um estudo macroscópico e microscópico dos processos que envolvem a ablação a laser em regime de femtossegundos em materiais homogêneos e estruturados. No caso de materiais estruturados, o estudo focou-se em uma situação de interface, na qual ocorrem mudanças nas propriedades de ablação. Baseado nos resultados, nós pretendemos obter subsídios científicos para entender as aplicações da ablação em regime de pulsos ultracurtos para estruturas estratificadas, tais como de dentes, ossos, interface resina-dente, dente-metal, e outras. Diferentes técnicas experimentais foram idealizadas para determinar a progressão da ablação dentro do material e obter dados extraídos da superfície. Utilizando luz espalhada de uma fonte externa, o processo de ablação foi temporalmente monitorado, permitindo determinar a velocidade de ablação em materiais transparentes, assim como perfis típicos de ablação nestes materiais. Em um segundo experimento, nosso estudo permitiu quantificar a variação da geometria de ablação perto de uma interface separando dois materiais distintos. Nossos dados foram suficientes para prever a ocorrência de uma descontinuidade no perfil da ablação entre dois meios: resina A e resina B, mostrando uma repentina descontinuidade do diâmetro da cavidade ablacionada. Adicionalmente, foi realizada uma análise dos aspectos morfológicos de diferentes tecidos biológicos irradiados e nosso estudo mostrou a eficiência da ablação utilizando laser de femtossegundos no processamento de tecidos duros e a possibilidade de utilizar esses sistemas sem causar danos térmicos e mecânicos nos tecidos remanescentes. Finalmente nós aplicamos a microperfuração a laser para produzir micro-poros na superfície de tecidos biológicos (fígados), melhorando a penetração do medicamento ALA e a aumentando a profundidade de tratamento.
Although laser ablation has been long used in general materials, little is known regarding the behavior of theses process near an interface separating two distinct materials. In this context, the main aim of this work was to perform a microscopic and macroscopic study of the processes that include femtosecond laser ablation in homogeneous and/or structured materials. In the case of structured materials, the study focused on an interface situation, in which sudden changes occurred in the properties. Based on the results, we aimed to obtain scientific subsidies to understand the application of ultrashort pulses to stratified structures, such as teeth, bones, resin-teeth or metal-teeth interface, and others. Distinct experimental techniques were used to determinate the ablation progression into the materials and to obtain data extracted from their surface. By using the scattered light from an external source, the ablation process was monitored temporally, allowing to determine the velocity of ablation in transparent materials, besides determining the typical profiles of ablated cavities in these materials. In a second experiment, our study allowed quantifying the overall variation in the ablation geometry that takes place on the interface of two different materials. Our data were sufficient to predict the occurrence of a discontinuity in the ablation profile on the interface between two media: resin A and resin B, showing a sudden discontinuity of the ablated cavity diameter. In addition, an analysis of the morphological aspects of different biological tissues irradiated by femtosecond laser pulses was performed and a comparative study showed the ablation efficiency of the femtosecond lasers in hard tissues processing and the possibility of using these systems with no thermal and mechanic damage. Finally, we applied a laser micromachining producing micro-pores on the tissue surface, improving the ALA penetration and increasing the treatment depth.

APA, Harvard, Vancouver, ISO, and other styles

40

Petrillo, Lucido. "La cascarilla cerámica como material escultórico." Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/104110.

Full text

Abstract:

La cascarilla cerámica es un material que se emplea principalmente para la realización de moldes en fundición. Esta investigación demuestra que la cascarilla cerámica puede ser empleada para la realización de escultura con una definición excepcional en su acabado. La investigación ha permitido identificar una serie de ventajas que presenta el material para afrontar las dificultades de un artista durante la realización de una escultura. La investigación se ha desarrollado en cinco etapas: En la primera etapa se recogió información sobre la cascarilla como material de proceso. Este fue el punto de partida para la investigación. En la segunda etapa se estableció la composición adecuada de la papilla, tanto en porcentajes como en tipo de aglutinante, y la curva de cocción. Para ello, se valoró sus características para la aplicación, el espesor, el secado, la resistencia mecánica, el coeficiente de reducción y la porosidad. En la tercera etapa se verificó que la cascarilla se adapta a todo tipo de materiales que ejercen de soporte. Se comprobó también que la papilla puede ser empleada con distintos procedimientos escultóricos: modelado, moldeado mediante molde de silicona o escayola, encofrado, con armazón metálico interno, etc. Además se establecieron métodos para reparar y modificar la cascarilla mediante herramientas manuales y eléctricas. En la cuarta etapa hemos comprobado distintas maneras de modificar la superficie de la cascarilla mediante otro tipo de minerales que no afectan la estructura: introducción de limadura de cobre, bronce y hierro en la papilla cerámica, distintos procedimiento de coloración en frío o caliente, mediante esmalte, engobe, etc. En la quinta etapa se realizaron esculturas empleando los métodos que se establecieron en las etapas anteriores, para verificar dicha hipótesis.
The ceramic shell is a material mainly used for making foundry molds. This research demonstrates that ceramic shell can be used for making sculptures with exceptional definition in its finish. The research has identified a number of advantages of the material to meet the challenges of an artist during the making of a sculpture. The research has been developed in five stages: In the first stage data were collected from the chaff as the process material. This was the starting point for research. In the second stage, we have set the appropriate composition of the slurry, both in percentage and type of binder, and firing curve. To this end, we evaluated the application characteristics, thickness, drying, mechanical strength, the reduction coefficient and porosity. In the third stage it was observed that the husk is suitable for all types of materials acting as support. It was also found that the slurry can be used with various sculptural processes: modeling, molding using silicone or plaster mold, shuttering, with internal metal frame, and so on. In addition, we have established methods to repair and modify the husk by hand and power tools. In the fourth stage we have found ways to modify the surface of the husk with other minerals that affect the structure: introduction of filing of copper, bronze and iron in the slurry ceramics, different staining procedure in hot or cold, by enamel slip, and so on. In the fifth stage sculptures were made using the methods established in the previous stages, to verify this hypothesis.

APA, Harvard, Vancouver, ISO, and other styles

41

Milisic, Edina. "Modelling of energy storage using phase-change materials (PCM materials)." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23506.

Full text

Abstract:

Unfortunately the global conventional fuels in reserves are running out while the world energy consumption is increasing very fast. All scientists agreed that Renewable energies is one of the best solutions for energy supply in many parts of the world. Renewable energies are solar energy, wind energy, bio energy, geothermal energy, tidal energy, and hydropower. Approximately all these forms of energy are hampered by their high costs. Moreover, solar energy, wind energy and tidal energy are characterized by their intermittent nature, as they are not available all the time. This intermittent problem can be solved by energy storage.Energy storage components improve the energy efficiency of systems by reducing the mismatch between supply and demand. For this purpose, phase-change materials are particularly attractive since they provide a high-energy storage density at a constant temperature which corresponds to the phase transition temperature of the material. The aim of this thesis is to Is to describe the state of the art progress in applying PCM materials for energy storage (essentially in tanks), and opportunities of their future applications, describe physical properties of typically used PCM materials, present a mathematical model of the energy balance during the energy storage (charge) and energy discharge from the PCM material. Mathematical model is based on one-dimensional (1D) analysis. The mathematical model consist of charging process and discharging process. During charging process the heat transfer fluid passes through the storage tank in order to transfer its thermal energy to the phase change material tube. During the discharging process, the cold water passes through the storage tank to acquire the thermal energy stored by the phase change material tube. Different solutions utilizing PCM was assessed. It was presented different Phase Change Materials for energy storage. This assessment indicated that salt hydrates are the most energy intensive of the PCM possibilities. When we use the Paraffin for energy storage we had less energy stored then with salt hydrates used like medium for energy storage. This assessment indicated that when we use PCM as a medium for energy storage we accumulate significantly more energy than in the case when we use water as a medium for energy storage.There are some weaknesses in the PCM model. It was assumed that the temperature in the tank was uniform. This will not apply for the real case where the heat transfer fluid temperature will increase while transferring through the tank. For a realistic case, the temperature of the first elements will decrease rapidly because of large temperature difference between the heat transfer fluid and the PCMs in the tank.

APA, Harvard, Vancouver, ISO, and other styles

42

Rogetzer, Patricia, Lena Silbermayr, and Werner Jammernegg. "Sustainable sourcing of strategic raw materials by integrating recycled materials." Springer Nature, 2018. http://dx.doi.org/10.1007/s10696-017-9288-4.

Full text

Abstract:

In this paper we investigate a manufacturer's sustainable sourcing strategy that includes recycled materials. To produce a short life-cycle electronic good, strategic raw materials can be bought from virgin material suppliers in advance of the season and via emergency shipments, as well as from a recycler. Hence, we take into account virgin and recycled materials from different sources simultaneously. Recycling makes it possible to integrate raw materials out of steadily increasing waste streams back into production processes. Considering stochastic prices for recycled materials, stochastic supply quantities from the recycler and stochastic demand as well as their potential dependencies, we develop a single-period inventory model to derive the order quantities for virgin and recycled raw materials to determine the related costs and to evaluate the effectiveness of the sourcing strategy. We provide managerial insights into the benefits of such a green sourcing approach with recycling and compare this strategy to standard sourcing without recycling. We conduct a full factorial design and a detailed numerical sensitivity analysis on the key input parameters to evaluate the cost savings potential. Furthermore, we consider the effects of correlations between the stochastic parameters. Green sourcing is especially beneficial in terms of cost savings for high demand variability, high prices of virgin raw material and low expected recycling prices as well as for increasing standard deviation of the recycling price. Besides these advantages it also contributes to environmental sustainability as, compared to sourcing without recycling, it reduces the total quantity ordered and, hence, emissions are reduced.

APA, Harvard, Vancouver, ISO, and other styles

43

Черкас, Софія Сергіївна. "Suture materials. Requirements for materials. The specifics of the application." Thesis, Київський національний університет технологій та дизайну, 2017. https://er.knutd.edu.ua/handle/123456789/7341.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Livshits, Maksim Y. "Fundamental Investigation of PhotoActive Materials From Small Molecules to Materials." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1490713190973503.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Gerlach, Ingmar. "Preparation of unique nanostructured materials using mesoporous materials as nanoreactors." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136274.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

LAVAGNA, LUCA. "Carbon materials and their role as reinforcement in composite materials." Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2729657.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Brocks, Thatiane [UNESP]. "Compósito estrutural carbono/epóxi via RTM para aplicação aeronáutica: processamento e caracterização." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/94458.

Full text

Abstract:

Made available in DSpace on 2014-06-11T19:27:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-07-08Bitstream added on 2014-06-13T19:47:37Z : No. of bitstreams: 1 brocks_t_me_guara.pdf: 1127902 bytes, checksum: d3d7631f1ee3c081efb6530997375ebd (MD5)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
A indústria aeronáutica nacional tem intensificado sua busca por materiais alternativos, com características e propriedades que permitam a substituição segura do material metálico. Com o objetivo de ganhar competitividade no mercado internacional e contribuir para o desenvolvimento tecnológico no país, o presente trabalho apresenta a técnica de processamento de moldagem por transferência de resina (RTM), utilizada na fabricação de materiais compósitos estruturais e ainda pouco estudada no Brasil. Os compósitos processados por essa técnica apresentam maior fração volumétrica de fibras, melhor acabamento superficial e pouca ou nenhuma necessidade de acabamento do componente produzido. Este trabalho compreende o processamento e a caracterização de compósitos produzidos com resina epóxi monocomponente Cycom 890 e dois tipos de tecidos, plain weave e twill 2x2, ambos de fibra de carbono. Para a determinação dos parâmetros de processamento, a resina foi caracterizada quanto aos seus comportamentos térmico e viscoso. Com base nos resultados e testes preliminares foi determinada a temperatura mais adequada de injeção em 100°C, a pressão de injeção entre 0,2 e 0,4 MPa e de vácuo em 250 mPa.s. Os compósitos produzidos foram analisados pela técnica de ultrassom C-Scan e os resultados mostraram que os laminados processados estão homogêneos quanto à impregnação. Testes de tração mostram que os laminados com tecido tipo Twill apresentam maior média de resistência à tração, enquanto que a diferença de trama não influencia significativamente às propriedades de flexão e cisalhamento, que se mostraram superiores as propriedades de compósitos produzidos em autoclave com maiores porcentagens de reforço. Em fadiga, ambos os laminados apresentaram um curto intervalo, com tensões próximas à de tração, no entanto, o laminado PW/Cycom apresentou maior...
The national aeronautical industry has intensified your search for alternative materials, with characteristics and properties that allow the safety replacement of metallic material. The goal is to gain competitiveness on international market and contribute with technological development in the country. This work presents a processing technique of resin transfer molding (RTM), used on manufacture of structural composites and understudied in Brazil. Composites processed by this method have a higher fibers volume fraction, better surface finish and little or no finishing require of produced component. This work includes the processing and characterization of composites made with monocomponent epoxy resin Cycon 890 and two types of carbon fiber fabrics, plain weave and twill 2x2. To determine processing parameters, the resin was characterized regarding thermal behavior and viscosity. Based on this results and preliminary tests, it was determined the most appropiate injection temperature at 100°C, the injection pressure between 0.2 and 0.4 MPa and vacuum pressure in 250 mPa.s. Composites produced were analyzed by C-scan ultrasound technique showing a homogeneous impregnation of processed panels. Tensile and flexural tests characterized mechanically composites, allowing seeing that Twill fabric has higher medium tensile performance, while the difference of weft does not influence significantly the flexural and shear properties, that are superior than properties of composites made by autoclaving with higher reinforced volume. In fatigue, both composites showed short interval, close to ultimate tensile strength (uts), however, the PW/Cycom laminated showed higher fatigue resistance, with an interval between 85-92% of uts. About the thermal behavior, it was observed an improvement in properties with the addition of carbon... (Complete abstract click electronic access below)

APA, Harvard, Vancouver, ISO, and other styles

48

Guiraldo, Ricardo Danil. "Variações termicas ocorridas na camara pulpar em função de tecnicas de inserção e tipos de fotoativação de composito." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/290118.

Full text

Abstract:

Orientador: Simonides Consani
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
Made available in DSpace on 2018-08-04T03:44:51Z (GMT). No. of bitstreams: 1 Guiraldo_RicardoDanil_M.pdf: 364199 bytes, checksum: 276b6a4ebf54255a1b8a3ee68f8b30de (MD5) Previous issue date: 2005
Resumo: O estudo avaliou o efeito dos tipos de incremento, de fotoativação e as fases restauradoras nas variações térmicas ocorridas na câmara pulpar, durante a fotoativação do compósito Filtek Z250. Foram utilizados 90 incisivos bovinos, nos quais foram feitos preparos cavitários (3x3x2,5mm) padronizados. Os dentes foram separados aleatoriamente em 3 grupos, de acordo com o tipo de fotoativação por luz halógena: 1- contínua (700 mW/cm2 por 20 s); 2- dupla intensidade (inicial de 100 mW/cm2 por 5 s, seguido de 700mW/cm2 por 15 s); 3- intermitente (2 s de ativação com 700mW/cm2, seguido do mesmo tempo pela ausência de luz, total de 40 s). Os grupos foram separados em 3 subgrupos segundo o tipo de incremento: 1- único; 2) oblíquos (três incrementos, um colocado nas paredes cervical e axial, outro nas paredes incisal e axial e o último unindo os dois); 3) horizontal/verticais (o horizontal foi colocado na parede axial, um vertical na parede cervical e o outro na parede incisal), totalizando 9 grupos (n=10). As cavidades foram condicionadas com ácido fosfórico por 20 s, o sistema de união Single Bond e o compósito Filtek Z250 aplicados segundo os protocolos de fotoativação e incremento. As restaurações foram realizadas em ambiente controlado (37ºC e 50±10% UR) e as temperaturas registradas com termômetro digital acoplado ao termopar tipo-K introduzido no canal radicular, de maneira que ficasse em contato com a dentina da câmara pulpar, correspondente à parede axial do preparo. Os dados obtidos foram submetidos à análise de variância e as médias ao teste de Tukey em níveis de 5% e 1%. A média de temperatura do incremento único (37,14ºC) foi significantemente menor que dos incrementos oblíquos (37,44ºC) e horizontal/verticais (37,43ºC). A luz contínua promoveu valor de temperatura (37,53ºC) estatisticamente superior aos demais tipos de luz, os quais não deferiram (37,27ºC e 37,21ºC). A fotoativação do adesivo foi estatisticamente maior (37,54ºC) que na aplicação do adesivo (36,82ºC) e na ativação do compósito (37,20ºC). Na interação tipo de incremento-tipo de fotoativação, na luz contínua o maior calor foi promovido pelo incremento horizontal/verticais, estatisticamente diferente dos demais. Na dupla intensidade, a maior temperatura foi no incremento oblíquo, diferente dos demais, enquanto na pulsátil não houve diferença. Para o incremento único não houve diferença quanto à fotoativação, enquanto no oblíquo a luz pulsátil promoveu valor significantemente menor. No incremento horizontal/verticais, a luz contínua foi estatisticamente superior. Na interação tipo de incremento-fase restauradora, o calor do incremento único foi estatisticamente superior na fotoativação do adesivo, seguido pela fotoativação do compósito e aplicação do adesivo. Para os incrementos oblíquo e horizontal/verticais, a fase aplicação do adesivo foi significantemente menor. Para as fases restauradoras não houve diferença estatística entre aplicação e fotoativação do adesivo, entretanto na fotoativação do compósito, o incremento único foi significantemente menor. Na interação tipo de fotoativação-fase restauradora, em todas as fotoativações não houve diferença estatística no calor das fotoativações dos adesivo e compósito, diferindo estatisticamente da fase aplicação do adesivo. Para as fotoativações do adesivo e do compósito, o calor produzido pela luz contínua foi significantemente maior, enquanto na aplicação do adesivo não houve diferença estatística. Houve influência das variáveis sobre o calor que atingiu a câmara pulpar
Abstract: This study evaluated the effect of the increment insertion and light-curing methods on thermal variations in the pulp chamber during Filtek Z250 composite resin light-curing. Standard cavities (3x3x2.5mm) were prepared in 90 bovine incisors. The teeth were randomly assigned into 3 groups, according to each light-curing method: 1- continue halogen light (700 mW/cm2 per 20s); 2- halogen light with a soft-start mode (initial intensity of 100 mW/cm2 per 5s obtained with a spacer and 700mW/cm2 per 15s, totalizing 20s); 3- intermittent halogen light (2s of activation with 700mW/cm2, followed by the same time of light absence, totalizing 40s). All groups were divided into 3 subgroups according to each type of increment: 1- bulk; 2- oblique (three increments, one in the cervical and axial walls, one in the incisal and axial walls, and finally one joining the the other two); 3- horizontal/vertical (the horizontal in the axial wall, one vertical in the cervical wall and another vertical in the incisal wall), totalizing 9 groups (n=10). All cavities were etched with phosphoric acid for 20s; the adhesive system Single Bond and the resin composite Filtek Z250 were applied according to the types of light-curing and increment. All experiments were carried out in controlled environment (37 Celsius degree and 50±10% relative humidity). The temperature variations (Celsius degree) were obtained using a digital thermometer attached to a type-K thermocouple which was inserted into the root canal as to be in contact with the pulp chamber dentine, correspondent to the axial wall of the cavity. Data were submitted to ANOVA and mean values compared by the Tukey¿s test with significance levels of 5% and 1%. The mean temperature (37.14) of the bulk increment was significantly lower than that oblique (37.44) and horizontal/verticals (37.43) increments. The continue light-curing revealed temperature mean values (37.53) statistically higher than those observed for the other types of light (37.27 and 37.21), which did not differ from each other. The adhesive light-curing showed statistically higher temperatures (37.54) than those observed during the adhesive application (36.82) and resin composite light-curing (37.20). In relation to the interaction between the light-curing method and type of increment, the horizontal/vertical increment under continue halogen light showed the highest temperature values, statistically different from the others. As for the soft-start light-curing method, the highest temperature was observed for the oblique increment, statistically different from others; no difference was observed for the intermittent halogen light. For the bulk increment, no statistically significant differences were observed among groups concerning the light-curing methods; however, in the oblique increment, the intermittent light revealed lower temperature values. For the horizontal/vertical increment, the continue light-curing temperature was statistically higher. For the interaction between type of increment and the restorative phase, the bulk increment heat was statistically higher in the adhesive light-curing phase, followed by the resin composite light-curing and adhesive application. The horizontal/vertical and oblique increments revealed significantly lower temperature values during adhesive application. In the restorative phases, no difference was observed between adhesive application and adhesive light-curing. However, in the resin composite light-curing, the bulk increment showed significantly lower temperature values. For the interaction between type of light-curing and restorative phase, no statistical difference was observed for all light-curing methods concerning adhesive and resin composite light-curing, differing only in the adhesive application phase. For the adhesive and resin composite light-curing phases, the heat produced by continue light was significantly higher. No statistically significant difference was verified for adhesive application. There was influence of the variables on the heat that reached the pulpar chamber
Mestrado
Materiais Dentarios
Mestre em Materiais Dentários

APA, Harvard, Vancouver, ISO, and other styles

49

Fernandes, Daniela Rodrigues. "Influencia da refusão de uma liga de niquel-cromo na adaptação cervical e interna de coroas totais com diferentes configurações marginais." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/290119.

Full text

Abstract:

Orientador: Simonides Consani
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
Made available in DSpace on 2018-08-04T20:49:18Z (GMT). No. of bitstreams: 1 Fernandes_DanielaRodrigues_D.pdf: 2902457 bytes, checksum: 3296ab64fe21504cb62f4540283146c3 (MD5) Previous issue date: 2005
Resumo: O objetivo deste trabalho foi verificar a influência da fonte de calor na fusibilidade e dureza de uma liga comercial à base de Ni-Cr (VERA BOND 11) nova, refundida (100%) e nova acrescida de sobras (50%). Para análise da fusibilidade foram confeccionadas 10 amostras para cada condição de liga, com uma tela para peneira de poliéster, com 11 X 11 filamentos de 0,22 mm de espessura, perfazendo uma malha de 100 espaços quadrados fixada bilateralmente por toda a extensão em fios de cera de 2,5 mm, contendo um pino formador do canal de alimentação no vértice. Para análise da dureza foram confeccionadas pastilhas em cera azul regular, com 8,0 mm de diâmetro por 2,0 mm de espessura, unidas a um pino formador do canal de alimentação. Após a obtenção dos padrões, estes foram fixados à base formadora do cadinho, de forma que a distância da base à câmara de reserva fosse 0,5 cm. Uma solução redutora da tensão de superfície foi aplicada sobre o padrão e após a secagem, este foi incluído em revestimento fosfatado - Termocast (Polidental, São Paulo Brasil) manipulado a vácuo, seguindo as instruções do fabricante quanto a proporção e tempo de manipulação. Os anéis foram aquecidos em forno elétrico (EDG) até atingirem a temperatura de 900°C, quando foram preenchidos por aproximadamente 15 gramas de liga fundida pela fonte de calor maçarico de fusibilidade, com o auxílio de um microscópio comparador com aumento de 16 X, considerando o número de espaços preenchidos no molde pela liga. Para análise da dureza superficial Rockwell 30T, os corpos-de-prova foram incluídos em resina acrílica quimicamente ativada, polidos e levados ao aparelho de dureza Testor HTI Super-Panambra, onde foram realizadas as medidas e obtidas as médias. Os resultados foram submetidos à análise de variância e as médias comparadas pelo teste de Tukey, em nível de significância de 5%. Quando foram comparadas as fontes de calor com os diferentes tipos de liga houve diferença estatística significativa entre as fontes de calor, na qual o aquecimento por indução demonstrou melhores resultados para fusibilidade. Não houve diferença estatística significativa nos valores médios de dureza quando foi utilizada a fonte de calor maçarico e aquecimento por indução para as ligas virgem e mista, porém o aquecimento por indução demonstrou melhores resultados que o maçarico, diferindo estatisticamente os valores de dureza, quando da utilização da liga refundida
Abstract: The aim of the present study was to verify the influence of the heat source on the castability and hardness of a Ni-Cr-based commercial alloy ¿ VERA BONO II - in three different conditions: new (first use), recast, and new mixed with scraps. In order to evaluate castability, 10 specimens were made for each alloy condition, using a polyester sieve with 11x11 filaments, 0.22mm thick, resulting in a screen with 100 square spaces. This screen was fixed to 0.25mm threads along the extension of two sides, and a post was fixed to its vertex. In order to perform hardness analysis, circular specimens made of regular blue wax measuring 8.0 mm in diameter and 2.0 mm thick were connected to the post, forming the sprue. The patterns were then fixed to the casting chamber, so that the distance from the base to the reservoir was 0.5 cm. A surface tension-reducing solution was abundantly applied to the patterns and after drying, the patterns were embedded into a phosphate-bonded investment - Termocast (Polidental, São Paulo, Brazil) manipulated under vacuum pressure, following manufacturer's instructions regarding proportions and manipulation times. Casting rings were placed in an electric oven (Bravac) until the temperature of 900°C was reached, and were then filled with approximately 15 grams of alloy, molten either by an oxigen/acethylen gas torch or by induction as heat sources. Following this procedure, castability evaluate hardness Rockwell 30T, specimens were embedded in chemically activated acrylic resin and then placed on a Testor HTI Super-Panambra hardness teste r. Hardness values for each specimen were obtained, and the average hardness was calculated. Results were submitted to analysis of variance and averages were compared by Tukey's test at 5% probability. There were statistically significant differences between the heat sources applied to the different types of alloy, with induction presenting the best castability results. There were no statistically significant differences in the average hardness values between torch or induction as the heating source for new and mixed alloys, although induction showed the best results, leading to statistically significant differences in hardness, when recast alloy was used.
Doutorado
Doutor em Materiais Dentários

APA, Harvard, Vancouver, ISO, and other styles

50

Dall'Magro, Eduardo. "Avaliação da dureza Knoop e da resistencia de união de restaurações em composito apos diferentes protocolos de fotoativação." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/288124.

Full text

Abstract:

Orientador: Mario Alexandre Coelho Sinhoreti
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
Made available in DSpace on 2018-08-06T22:45:08Z (GMT). No. of bitstreams: 1 Dall'Magro_Eduardo_D.pdf: 295929 bytes, checksum: fff79306c903b7754412f722f45d554b (MD5) Previous issue date: 2006
Resumo: Este estudo apresenta três experimentos na mesma linha de pesquisa. No primeiro estudo, foi avaliada a resistência de união através do método push out e a dureza Knoop do compósito dental Z250 (3MIESPE) fotoativado utilizando o aparelho de lâmpada halógena XL2500 (3M/ESPE) sob diferentes protocolos de fotoativação: modo contínuo (CH) (700 mW/cm2) por 20 segundos; modo contínuo de baixa intensidade (CL) (150 mW/cm2) por 20 segundos; e, pulse-delay com ativação na intensidade de 150 mW/cm2 por 2s(P2), 3s(P3), 5s(P5), 1 Os(P1 O) ou 15 segundos (P15), seguindo-se 1 minuto de espera, e complementado por 700 mW/cm2 por mais 20 segundos. Para o teste de push out, após a fotoativação, os corpos-de-prova foram armazenados a 37°C :I: 1 por 24h :t 1 até serem desgastados e polidos, e, os valores de resistência à união foram observados numa máquina de ensaio universal (Instron) com célula de carga de 500 N e velocidade de 0,5 mm/min. Para o ensaio de dureza, a fotoativação seguiu o mesmo protocolo. Após a confecção, as amostras foram embutidas em resina de poliestireno e submetidas ao acabamento e polimento com lixas d'água, a fim de obter as medidas de dureza, na superfície, a 1 mm, 2, 3, 4, e 5 mm de profundidade, num durometro (HMV 2, Shimadzu), utilizando carga de 50g, por 15 segundos. Os dados foram submetidos à Análise de Variância e as médias ao teste de Tukey (5%). Os resultados de resistência à união mostraram que o grupo P5, apresentou valor de resistência de união significantemente maior que os demais grupos. O grupo CL apresentou resistência de união menor que o grupo anteriormente citado, mas superior aos demais grupos. Não houve diferença estatística significativa entre os grupos P2, P3, P10, P15 e CH. A dureza Knoop mostrou que os grupos CH e P15 apresentaram as maiores médias de dureza na superfície e até 4 mm de profundidade. Os corpos-de-prova do grupo CL apresentaram as menores médias de dureza. Na profundidade de 3 mm , a dureza Knoop de todos os grupos foi estatisticamente inferior a da superfície. O segundo experimento avaliou a resistência de união através do método de push out e a dureza Knoop do compósito odontológico Z250 (3M/ESPE), fotoativado com o aparelho de lâmpada halógena XL2500 (3MIESPE), utilizando diferentes protocolos de fotoativação: modo contínuo (700 mW/cm2 por 20s) (CO); soft-staft (50 mW/crn2 por 5s, seguido por 700 mW/crn2 for 15s) (551); soft-start (100 mW/crn2 por 5s, seguido por 700 mW/cm2 por 15s) (552); soft-start (150 mW/crn2 por 5s, seguido por 700 mW/crn2 por 15s) (553); soft-start (200 mW/crn2 por 5s, seguido por 700 mW/cm2 por 15s) (554); soft-start (250 mW/cm2 por 5s, seguido por 700 mW/cm2 por 15s) (555); soft-start (300 mW/crn2 por 5s, seguido por 700 mW/crn2 por 15s) (556). Os testes de push out e de dureza Knoop foram realizados como no primeiro experimento. Os dados foram submetidos à Análise de Variância e as médias ao teste de Tukey (5%). Os resultados mostraram que o grupo 553, obteve a maior resistência de união quando comparado ao grupos. Não houve diferença estatística entre os outros modos soft-start em relação aos demais grupos. Os outros resultados de dureza, não apresentaram diferença estatística entre os grupos na região de superfície e até 4 mm de profundidade. Também foi observado que para cada grupo, não houve diferença estatística entre a região de superfície até a profundidade de 2 mm. O terceiro experimento avaliou a resistência de união através do método de push out do compósito odontológico Z250 (3M/E5PE), fotoativado com o aparelho de lâmpada halógena XL2500 (3MIE5PE), utilizando diferentes protocolos de fotoativação: soft-start (ativação na intensidade de 150 mW/crn2 por 2s(552), 3s(553), 5s(555), 10s(5510) ou 15 segundos (5515), e complementado por 700 mW/cm2 por mais 15 segundos); pulse-delay (ativação na intensidade de 150 mW/cm2 por 2s(P2), 3s(P3), 5s(P5), 1 Os(P1 O) ou 15 segundos (P15), seguindo-se 1 minuto de espera, e complementado por 700 mW/crn2 por mais 15 segundos). Os testes de push out foram realizados como no primeiro experimento. Os dados foram submetidos à Análise de Variância e as médias ao teste de Tukey (5%). Os resultados mostraram que não houve diferença estatística entre os modos soft-start. Para o modo pulse-delay, o grupo P5 apresentou resistência de união estatisticamente superior aos demais grupos. Os grupos fotoativados pelo modo pulse-delay apresentaram resistência de união superior comparados aos grupos fotoativados pelo modo soft-start
Abstract: This study showed three experiments in the same research line. The first study has assessed the bond resistance through the push out method and the Knoop hardness of the dental composite Z250 (3M/ESPE). photoactivated with the equipment of halogen light XL2500 (3M/ESPE), using different protocols of photoactivation: the continuous mode of high intensity (CH) (700mW/cm2) for 20 seconds; the continuos mode of low intensity (CL) (150mW/cm2) for 20 seconds; and the pulse-cJe/ay with 150mW/cm2 for 2s(P2), 3s(P3), 5s(P5), 10s(P10) or 15 seconds (P15), with a 1-minute delay, followed by 700mW/cm2 for 20 seconds. For the push out test, the test specimens were stored at 31> C :I: 1 for 24h :I: 1 until they were ground and polished, and, the bond strength values were observed through a universal test machine (Instron) with a charge cell of 500N and the speed of 0.5 mm/min. For the Knoop hardness, the specimens were made by using the same photoactivation protocols. After, the specimens were embedded in polyestiren resin and sanded and polished in order to obtain the hardness measures on top, 1 mm, 2, 3, 4, and 5 mm deep in a hardness measure machine (HMV 2, Shimadzu), using a charge of 50g, for 15 seconds. The data were submitted to ANOVA and Tukey's test (5%). The results of bond strength showed that the P5 group presented significantly higher resistance values than the other groups.The CL group presented a lower bond resistance than the group previously mentioned, though higher than the other groups. There was no statistic difference between the groups P2, P3, P10, P15 and CH. The results of Knoop hardness showed that the groups CH and P15 presented higher values of Knoop hardness in surfaces up to 4 mm deep. The specimens of the CL group presented the lowest averages of hardness. At 3 mm deep, the Knoop hardness of ali groups was statistically inferior to the surface hardness. The second study evaluated the bond strength through the push out method and the Knoop hardness of the dental composite Z250 (3MIESPE), photoactivated with halogen lamp unit XL2500 (3MIESPE), using different protocols of photoactivation: continuous mode (700mW/cm2 for 20s) (CO); soft-start (50 mW/cm2 for 5s, followed by 700 mW/cm2 for 15s) (551); soft-s/art (100 mW/cm2 for 5s, followed by 700 mW/cm2 for 15s) (552); soft-start (150 mW/cm2 for 5s, followed by 700 mW/cm2 for 15s) (553); softstart (200 mW/cm2 for 5s, followed by 700 mW/cm2 for 15s) (554); soft-s/art (250 mW/cm2 for 5s, followed by 700 mW/cm2 for 15s) (555); soft-start (300 mW/cm2 for 5s, followed by 700 mW/cm2 for 15s) (556). For the push ou! test and Knoop hardness test the specimens were made how the first experiment. The data were submitted to ANOVA and Tukey test (5%). The results showed that the 553 group obtained the higher bond strength when compared to the CO group. There were no differences among the other modes of soft-s/art in relation to the other groups. The other results in hardness, showed no statistic differences among the groups in the surface region and up to 4 mm depth. It was also observed that within each group there were no statistic differences between the surface region up to the 2 mm depth. The third study evaluated the bond strength through the push out method of the dental composite Z250 (3M/E5PE), photo activated with halogen lamp unit XL2500 (3MIE5PE), using different protocols of photo activation: soft-s/art (150 mW/cm2 for 2s(552), 3s(553), 5$(555), 10$(5510) or 15 seconds (5515), followed by 700 mW/cm2 for 15 seconds); pulse-de/ay (150 mW/cm2 for 2s(P2), 3s(P3), 5s(P5), 10s(P10) or 15 seconds (P15), with a 1-minute delay, followed by 700 mW/cm2 for 15 seconds). For the push out test the specimens were made how the first experiment. The data were submitted to ANOVA and Tukey test (5%). The results showed there were no statistic differences among groups photo activated using soft-s/art mode. For pulse delay mode P5 obtained the highest bond strength, statistically higher than other groups. The groups photoactivated with pulse-de/ay mode showed bond strength statistically higher than soft-s/art mode
Doutorado
Doutor em Materiais Dentários

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Materials'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles