R. R. Menezes

Estudo de argilas usadas em cerâmica vermelha

The aim of this work was to characterize clays industrially used for the production of ceramic bricks. The clays were characterized by particle size distribution, Atterberg limits and chemical composition determination, X-ray diffraction and differential thermal and gravimetric analyses. Test specimens were prepared by extrusion and fired at 800, 900 and 1000 oC. Fired test specimens were characterized in terms of water absorption and mechanical strength. Commercially produced ceramic bricks were also characterized in terms of water absorption and mechanical strength. The results showed that clays had plasticity limits in the range indicated for brick clay industry and are composed by kaolinite, quartz, mica and feldspars, with some samples presenting goethite and silicon-aluminous hydroxide. The suitability to produce ceramic bricks using the studied samples could be determined by the characterization process.

Statistical design for recycling kaolin processing waste in the manufacturing of mullite-based ceramics

Mineral extraction and processing industries have been cited as sources of environmental contamination and pollution. However, waste recycling represents an alternative recovery option, which is interesting from an environmental and economic standpoint. In this work, recycling of kaolin processing waste in the manufacture of mullite-based ceramics was investigated based on the statistical design of mixture experiments methodology. Ten formulations using kaolin processing waste, alumina and ball clay were used in the experiment design. Test specimens were fired and characterized to determine their water absorption and modulus of rupture. Regression models were calculated, relating the properties with the composition. The significance and validity of the models were confirmed through statistical analysis and verification experiments. The regression models were used to analyze the influence of waste content on the properties of the fired bodies. The results indicated that the statistical design of mixture experiments methodology can be successfully used to optimize formulations containing large amount of wastes.

Argilas bentoníticas de Cubati, Paraíba, Brasil: Caracterização física-mineralógica

O Estado da Paraiba possui jazidas de bentonitas utilizadas comercialmente em uma vasta gama de setores tecnologicos. No entanto, esses jazimentos estao se exaurindo apos dezenas de anos de exploracao. Assim, este trabalho tem por objetivo a caracterizacao fisico-mineralogica de bentonitas recentemente descobertas no municipio de Cubati, PB. As amostras estudadas foram secas a 60 oC e caracterizadas por meio de fluorescencia de raios X, picnometria de He, determinacao da distribuicao de tamanho de particulas, difracao de raios X, analise termica diferencial e gravimetrica e microscopia eletronica de varredura. Os resultados evidenciaram que as amostras sao bentonitas policationicas, apresentando teores de MgO, CaO e K2O semelhantes aos de outras bentonitas sul-americanas e que sao constituidas por argilomineral esmectitico e por quartzo e caulinita. As amostras apresentaram fracoes de particulas abaixo a 2 μm variando entre 31 e 41%, estando, no entanto, em elevado estado de aglomeracao.

Sinterização de cerâmicas em microondas. Parte I: aspectos fundamentais

Processing of materials based on heating by microwave energy has gained increasing importance in many industrial applications due to its potential advantages over conventional heating methods. In the sintering of ceramic materials, the use of microwave energy decreases the processing time, saves energy and improves the microstructural homogeneity of ceramic bodies. These advantages have motivated various research groups around the world to study microwave sintering. However, the benefits deriving from the use of microwaves depend on the control and scientific understanding of the parameters and aspects of the process. This paper offers a review of the fundamental scientific aspects of microwave sintering of ceramics, focusing on the interaction between materials and microwaves and highlighting particular points of the hybrid sintering process and methodology.

Análise da influência do tratamento de purificação no comportamento de inchamento de argilas organofílicas em meios não aquosos

As argilas bentonitas possuem importantes funcoes em fluidos de perfuracao nao aquosos. No entanto, impurezas presentes na argila e a escolha inadequada do sal quaternario utilizado no seu processo de organofilizacao podem comprometer a compatibilidade do sistema argila-fluido. Assim, este trabalho tem por objetivo analisar a influencia do tratamento de purificacao e dos sais quaternarios de amonio no comportamento de inchamento de argilas organofilicas em meios nao aquosos. A argila bentonita foi purificada atraves de procedimento de sedimentacao e as argilas organofilicas foram preparadas utilizando-se cloreto de alquil benzil amonio (Dodigen), cloreto de diestearil dimetil amonio (Praepagen), cloreto de cetil trimetil amonio (Genamim) e brometo de cetil trimetil amonio (Cetremide). As argilas organofilizadas foram caracterizadas por difracao de raios X e determinacao da distribuicao do tamanho de particulas e, em seguida, submetidas ao ensaio de inchamento de Foster em ester, parafina e oleo diesel. Os resultados mostram que o processo de purificacao foi eficiente na reducao de impurezas presentes na bentonita e que a argila organofilica purificada tratada com Praepagen e Genamim apresenta valores de inchamento de Foster em ester, oleo diesel e parafina superiores aos obtidos com argilas organofilicas sem purificacao (natural) e comercial.

Comportamento de expansão de argilas bentoníticas organofílicas do estado da Paraíba

Organoclays are used in a wide range of industrial applications, from the petroleum to the pharmaceutical and cosmetic industry, reaching the waste adsorption applications and production of polymer-clay nanocomposites. This work has as aim study the influence of the amount of quaternary ammonium salts in the organophilization of bentonite clays. The used clays were characterized by chemical composition, particle size distribution and cation exchange capacity determination. The organoclays were prepared using two quaternary ammonium salts: alkyl dimethyl benzyl ammonium chloride (Dodigen) and cetyl trimethyl ammonium bromide (Cetremide). The organoclays were characterized by X-ray diffraction and IR spectroscopy. The results showed that the interlayer spacing increase with the rise in the amount of salt used for the organophilization, and that this behavior varied according to the salt and clay used, the interlayer spacing increasing behavior is linear when the Dodigen salt was used and varied according to the bentonite clay when the Cetremide salt was used.

Obtenção de mulita porosa a partir da sílica da casca de arroz e do acetato de alumínio (Porous mullite obtained using silica from rice husk and aluminum acetate)

O grande volume de producao de arroz no mundo gera uma enorme quantidade de rejeito na forma de cascas e de cinzas oriundas da queima da casca. Esses residuos sao fontes de poluicao e contaminacao, podendo agredir diretamente a saude da populacao. Assim, esse trabalho tem por objetivo a obtencao de mulita porosa a partir da silica da casca de arroz e do acetato de aluminio. O residuo foi fisica e quimicamente caracterizado e em seguida misturado com acetato de aluminio para a producao do precursor da mulita. O material precursor foi caracterizado termicamente e com base nos resultados foi calcinado a 850 oC e 1200 oC. Os corpos de prova foram queimados a 1500 oC e 1600 oC e caracterizados pela determinacao de sua porosidade aparente, absorcao de agua e densidade aparente e por difracao de raios X e microscopia eletronica de varredura. Os resultados indicaram que a silica e constituida por material amorfo e aglomerados micrometricos de particulas submicrometricas e nanometricas. Com base nos resultados conclui-se que a silica obtida da casca de arroz e o acetato de aluminio podem ser utilizados com sucesso para a producao de corpos muliticos porosos com porosidades superiores a 48%.

Sinterização de cerâmicas em microondas. Parte III: Sinterização de zircônia, mulita e alumina

Thermal processing by microwaves offers several advantages over conventional heating methods, such as shorter processing times, energy savings and improved microstructural homogeneity of ceramic bodies. Thus, this work focused on the fast hybrid microwave sintering of ceramic materials that require high sintering temperatures for densification. The materials studied here were zirconia, which displays abrupt and severe increases in dielectric loss with rising temperature, and alumina and mullite, which show low dielectric losses at ambient temperature and are difficult to microwave at low temperatures. A susceptor was used as an auxiliary heating agent. The results indicate that the sintering system developed here can be used efficiently for the rapid, homogeneous sintering of all the ceramics in question. Zirconia was sintered in 20 min, mullite in 16 min and alumina in 40 min heating cycles.

Studies of new occurrences of bentonite clays in the State of Paraíba for use in water based drilling fluids

New bentonite clay deposits have recently been discovered in the state of Paraiba, mainly in the municipalities of Cubati and Pedra Lavrada, creating great expectations in view of the possibility of expanding industrial production using these new reserves. The aim of this study was to study the new occurrences of bentonite clay in Paraiba, particularly in the municipality of Pedra Lavrada, for use in water based drilling fluids. The mineralogical properties of the clays were characterized by particle size analysis using laser diffraction, and thermogravimetric and differential thermal analysis, and its chemical composition was analyzed by X-ray fluorescence, X-ray diffraction, cation exchange capacity and specific surface area. The bentonite clays were treated with sodium carbonate at concentrations of 75, 100, 125, 150 and 175mEq/100g of dry clay, to transform them from polycationic to sodium form. For the technological characterization, drilling fluids were prepared according to the standards of Petrobras. The results indicated that the mineralogical composition of the samples consisted of montmorillonite, kaolinite and quartz. As for their rheological properties, the samples were found to partially meet the rheological requirements of the Petrobras standard.

Planejamento experimental no estudo da maximização do teor de resíduos em blocos e revestimentos cerâmicos

The use of experimental design to the study of mixtures has found a wide range of applications, even in laboratory scale or in industrial development works. Thus, this work has as aim apply the experimental design used in the study of mixtures to evaluate the suitability of use kaolin processing waste and granite sawing waste together for the production of ceramic bricks and tiles. Based on the raw materials, specific formulations were developed using the experimental design. The raw materials were mixed and sample bodies were produced using extrusion and uniaxial pressing. The sample bodies were fired and characterized in terms of water absorption and mechanical strength. Regression models were adjusted relating the water absorption and mechanical strength with the amount of raw materials. The results showed that the methodology of experimental design maximize the content of wastes incorporated in ceramic bricks and tiles formulations. Formulations containing up to 50% waste can be used for the production of ceramic bricks, and formulations, which contained up to 40% of waste can be used for the production of ceramic tiles.