Submitted by Viviane Lima da Cunha (viviane@biblioteca.ufpb.br) on 2016-07-28T13:17:58Z No. of bitstreams: 1 arquivototal.pdf: 2098256 bytes, checksum: ecc2e6022cdb0ed0a21b9127d6c65e3c (MD5) / Made available in DSpace on 2016-07-28T13:17:58Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2098256 bytes, checksum: ecc2e6022cdb0ed0a21b9127d6c65e3c (MD5) Previous issue date: 2016-04-22 / Refractory ceramics are ceramic materials which have among its main features the ability to withstand high temperatures without melting or decomposed and to remain non-reactive and inert when exposed to harsh environments. These characteristics define the purposes for which these materials are proposed, which can be highlighted applications linings, heat treatment and refining of metals, manufacture of glass and power generation. With the constant evolution of the refractory industry, increasingly necessary it becomes the search for technological means to bring improvements to the cost / benefit ratio of the materials produced. The use of natural raw materials is a point of extreme importance in the refractory industry, since these raw materials are found in deposits scattered in the earth's crust. The mullite (3Al2O3.2SiO2) is an alumino-silicate that due to its special properties has been described as one of the most important refractory ceramic of today. The kaolin waste obtained in the second step of the primary kaolin processing can be used as a source for synthesizing mullite. In this context, this study aimed to use the mixture design (kaolin, kaolin waste and alumina) to obtain mullite based refractory ceramics. The samples were pressed and sintered between 1300 and 1550 °C and then subjected to the determination of physical and mechanical properties, characterization of crystalline phases by XRD and microstructural analysis by SEM. The results indicated obtaining mullite from 1300 °C. It was observed that the mullitization process was affected by the concentration of the raw materials and the sintering temperature. In compositions rich in kaolin waste the sintering mechanism by liquid phase favors the densification process. A specific formulation, containing 50 wt.% of kaolin and 50 wt.% of kaolin waste (mica-rich) had twice the mechanical strength of pure kaolin after sintering at 1300 °C. This study demonstrated the possibility of obtaining mullite with up to 94% of relative density through reactive sintering of kaolin/residue kaolin/alumina mixtures at temperatures as low as 1300 °C. / Cerâmicas refratárias são materiais cerâmicos que possuem entre suas principais características a capacidade de resistir a temperaturas elevadas sem fundir-se ou decompor-se e de permanecerem não reativos e inertes quando expostos a ambientes severos. Tais características definem os fins aos quais estes materiais se propõem, podendo-se destacar aplicações em revestimentos de fornos, tratamentos térmicos e refino de metais, fabricação de vidros e na geração de energia. Com a constante evolução da indústria refratária, torna-se cada vez mais necessária a busca de meios tecnológicos que tragam melhorias à relação custo/benefício dos materiais produzidos. O uso de matérias-primas naturais é um ponto de extrema importância na indústria de refratários, já que essas matérias-primas são encontradas em depósitos espalhados na crosta terrestre. A mulita (3Al2O3.2SiO2) é um alumino-silicato que em virtude de suas propriedades especiais tem se qualificado como uma das mais importantes cerâmicas refratárias da atualidade. O resíduo de caulim, obtido na segunda etapa do beneficiamento de caulins primários, pode ser utilizado na síntese de mulita. Neste contexto, este trabalho teve como objetivo utilizar o delineamento de misturas (caulim, resíduo de caulim e alumina) para a obtenção de cerâmicas refratárias à base de mulita. Corpos de prova obtidos por prensagem uniaxial foram sinterizados entre 1300 e 1550 °C e, em seguida, submetidos à determinação das propriedades físico-mecânicas, caracterização de fases cristalinas por DRX e análise microestrutural por MEV. Os resultados indicaram a obtenção de mulita a partir de 1300 °C. Observou-se que o processo de mulitização foi afetado pela concentração das matérias-primas e pela temperatura de sinterização. Nas formulações ricas em resíduo de caulim o mecanismo de sinterização por fase líquida favoreceu o processo de densificação. Uma formulação específica, contendo 50 % de caulim e 50 % de resíduo de caulim (rico em mica), apresentou o dobro da resistência mecânica do caulim puro após sinterização a 1300 °C. Este estudo demonstrou a possibilidade de obter mulita com até 94% de densidade relativa via sinterização reativa de misturas caulim/resíduo de caulim/alumina a temperaturas tão baixas quanto 1300 °C.

Made available in DSpace on 2015-04-01T12:17:41Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 5407282 bytes, checksum: a419b6ea58a65ebab5c93d611083a99e (MD5) Previous issue date: 2014-02-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Currently in Brazilian deposits of bentonite clays there are clays with a high percentage of coarse fractions, which have a negative influence on the rheological properties of dispersions prepared with these clays, precluding its use in aqueous drilling fluids of oil wells. The use of a blending with available samples has been industrially used successfully. Therefore, the present study aimed, and using the methodology of modeling blends with simplex centroid network planning with subsequent purification by hydrocycloning and drying in kiln and by spray dryer, optimize the rheological properties of dispersions prepared from mixtures of little noble bentonite clays, from the city of Boa Vista PB, in order to obtain drilling fluids that answer the requirements of the standard EP-1EP-00011-A Petrobras. Through the mixture design was observed that the presence of clay called Verde-Lodo increased values of apparent and plastic viscosities. This fact contributed to this clay was present in all mixtures purified by hydrocycloning. The presence of clay Bofe decreased values of volume of filtrate. Through the intersection of the response surfaces of the mixtures design were obtained eight compositions in which the rheological properties were closer to that specified by the standard and that, therefore, they were more likely to adapt the requirements after the process of purification by hydrocycloning, which showed efficient in promote size separation, with consequent elimination of the coarse fractions of contaminants, especially quartz. Still, it was observed that the purified dried in kiln, which was ground in the mill disks, showed average diameters lower than the purified dried by spray dryer. However, showed a lower rheological behavior to the purified dried by spray dryer, which showed, generally, values of apparent and plastic viscosities above the regulatory requirements. Therefore, it was possible to optimize the rheological properties of a fluid obtained from little noble bentonite clays, enabling the use those low quality clays in drilling fluids for oil wells. / Atualmente, nos depósitos brasileiros de argilas bentoníticas, encontram-se argilas com elevado percentual de frações grosseiras, as quais influem negativamente nas propriedades reológicas das dispersões preparadas com essas argilas, impossibilitando seu uso em fluidos aquosos de perfuração de poços de petróleo. A utilização de um blending com as amostras disponíveis tem sido utilizada industrialmente com sucesso. Assim, o presente trabalho teve por objetivo, e utilizando a metodologia de modelagem de misturas com planejamento em rede simplex centróide com posterior purificação por hidrociclonagem e secagem em estufa e por spray dryer, otimizar as propriedades reológicas de dispersões preparadas a partir de misturas de argilas bentoníticas pouco nobres, provenientes do município de Boa Vista PB, de modo a obter-se fluidos de perfuração que atendam as exigências da norma EP-1EP-00011-A da Petrobras. Através do delineamento de misturas observou-se que a presença da argila denominada de Verde-Lodo elevou os valores de viscosidades aparente e plástica. Tal fato contribuiu para que esta argila estivesse presente em todas as misturas purificadas por hidrociclonagem. A presença da argila Bofe diminuiu os valores de volume de filtrado. Através da intersecção das superfícies de resposta do delineamento de misturas obtiveram-se oito composições nas quais as propriedades reológicas estavam mais próximas do especificado pela norma e que, portanto, tinham mais chances de se adequarem às exigências após o processo de purificação por hidrociclonagem, o qual se mostrou eficiente em promover separação granulométrica, com consequente eliminação das frações grosseiras de elementos contaminantes, especialmente quartzo. Ainda, observou-se que os purificados secos em estufa, os quais foram moídos em moinho de discos, apresentaram diâmetros médios menores que os purificados secos por spray dryer. No entanto, apresentaram um comportamento reológico inferior aos purificados secos por spray dryer, os quais apresentaram, de forma geral, valores de viscosidades aparente e plástica acima das exigências normativas. Portanto, foi possível a otimização das propriedades reológicas de um fluido obtido a partir de argilas bentoníticas pouco nobres, possibilitando a utilização dessas argilas de baixa qualidade em fluidos de perfuração de poços de petróleo.

Volumetric properties have been the cornerstone of asphalt mixture design and control dating back to the early 20th century. However, social and economic drivers have caused the asphalt industry to make changes in materials and processes used to produce mixtures that have stretched the limits of volumetric centric methodologies. The primary objectives of this dissertation were to present an extensive case on how volumetrics is limited in their ability to characterize asphalt mixtures and to advance the body of knowledge of a viable alternative. State agency specifications were examined and found that Departments of Transportation (DOTs) were using asphalt volumetric properties inconsistently across the southeast U.S. A series of data driven computations were conducted to determine if correlations existed between volumetric properties and measured mixture properties utilizing a statewide asphalt mixture design database and a multiyear compilation of quality control data for a single mixture. The second focus employed Cantabro Mass Loss (CML) testing in a multifaceted study to index CML against other mechanical property tests, conduct and assess CML alongside daily volumetric testing, improve CML laboratory conditioning procedures, and begin establishing CML single and multilaboratory variability standards. Data analysis was unable to determine any strong relationships between volumetrics and any other measured properties, which strengthens the case against sole reliance on volumetrics for asphalt mixture characterization. CML was shown to potentially be a more robust test compared to the other mechanical property tests because of its ability to react in an expected manner to field aging and increasing air voids. A modest trend was established between CML, and other mixture properties indicated that changes in volumetric properties individually do not raise concern but in combination they could negatively impact quality. Time-optimized conditioning protocols resulted in favorable field aging simulated years based on the available data, but more testing is recommended for some situations. Round robin testing was able to establish acceptable differences for a single test containing three replicates, however a useable allowable difference between two laboratories was not determined, and a second study is recommended using the single test differences to improve accuracy.