Incorporation of SCBA in Red Ceramics and Sintering in Microwave Oven

The present study investigated the incorporation of sugarcane bagasse ash (SCBA) in red ceramics, sintered in conventional oven and microwave oven, aiming to provide an alternative product, and a sintering process with higher energy efficiency in the production of red ceramics. The raw materials were characterized by XRF, XRD, thermogravimetry, particle size distribution and specific mass analyses. The specimens were shaped by extrusion in two different compositions, red clay and red clay with addition of 20 % SCBA and sintered at temperatures from 700 to 1100 ºC. The conventional sintering occurred for 60 min with heating rate of 10 ºC/min. In the microwave oven the sintering occurred in a hybrid way, with heating rate of 50 ºC/min for 5, 10 and 15 mins. After sintering the tests of linear shrinkage, compressive strength, water absorption, apparent porosity and apparent specific mass were performed. The addition of SCBA causes an increase in the values of water absorption and decreases the compressive strength and specific mass of the red ceramic. This occurs due to the creation of pores inside the material from the volatilization of organic matter present in the ashes. The sintering in microwave oven, when compared to conventional sintering, promotes an increase in the values of compressive strength and specific mass and reduction of water absorption values of ceramics, probably due to the refinement of the microstructure and the higher densification. Thus the incorporation of ashes can be partially compensated by a more efficient sintering. The use of SCBA and the sintering in microwave oven, showed to be viable alternatives in the development of a more sustainable and light material, promoting the management of waste, reduction in the consumption of raw materials and energy saving

Effects of curing treatment on some real properties of Boa Vista smectic clays, aiming at their application as thixotropic fluids for drilling oil wells.

Visando o estudo dos efeitos de tratamento de cura em algumas propriedades reolõgicas de argilas esmectíticas para uso como fluídos tixotrõpicos na perfuração de poços de petróleo, duas amostras de cores verde-clara e vermelha da localidade de Bravo, Distrito de Boa Vista Município de Campina Grande, Paraíba foram submetidas a ensaios de caracterização e a ensaios tecnológicos. Foram utilizados quatro processos de tratamento de cura com o auxílio de uma câmara climatizada controlável, variando-se a umidade relativa, a temperatura, o tempo e a concentração de carbonato de sódio. Com dois processos verificou-se também o efeito da diálise antes e depois do tratamento de cura. Foram também determinados, para as amostras submetidas a cura â 90%UR e A0°C e a 90%UR e 90°C, os teores de carbonatos e bicarbonatos existentes na suspensão a 6% de sólidos. Com estes valores foram calculados as correlações com as propriedades reolõgicas estuda das que foram a viscosidade aparente, viscosidade plástica e volume do filtrado. Os estudos mostraram que as argilas de cor verde-clara apresentam excelentes propriedades reolõgicas após tratamento de cura conveniente, possibilitando assim o uso dessa argila que a pesar de ser abundante e considerada imprópria. O trabalho também mostra que as argilas de cor vermelha também apresentam propriedades reolõgicas dentro das especificações quando convenientemente tratadas. Verifica-se também que ambas as amostras apresentam comportamentos reológicos diferentes quando submetidas ao mesmo tratamento de cura, apesar dos ensaios de caracterização mostrarem que são constituídos pelos mesmos argilominerais . Estabeleceu-se também os teores mínimos e máximos de carbonatos e bicarbonatos necessários para obter propriedades reológicas dentro das especificações.A study of the effects of cure-treatment on some rheological propert ies of esmectite clays, which may be used as thixotropric fluid in petroleum drilling, was made on two samples of lightgreen and red colour smectite clays obtaind from the Bravo loca lity of Boa Vista district of Campina Grande, Paraiba. They were submited to characterization analysis and techno 1ogica 1 tests.Four processes of cure treatment were used in a chamber of controlable climate where the relative humidity, the temperature, the time and the sodium carbonate concentration could be varied. The range of the relative humidity studiet was 50% until 30%, and the range of the temperature varied from kO°C to 90°C. With two of the processes the effect of dialysis before and after the cure treatment was also verified. The amounts of carbonate and bicarbonate were also determined for the clay sample suspensions of 6% solid content and submited to the cure treatment of 90% re lative humidity at hO°C temperature and 90% relative humidity at 90°C temperature. On the basis of these data the correlations of the rheological properties like apparent viscosity, plastic vis cosity and filtered volume were found out. The study showed that the light-green clay becomes ex^ cellent in rheological properties after the adequate cure treatment. Thus this clay found abundantly can be utilised althoug it is considered improper to be used. It was found out that the red clay when treated proprtly also presented rhelogical properties with in the limits of specifications. It was verified that the two clay samples behaved rheologicaly differently when submited to the similar cure treatment, inspite of the fact that both the clays are basically of same mineral. The minimum and maximum contents of carbonate and bicar bonate necessary to obtain the specific rheological properties of the clays were also established in the present work

Microwave fast sintering of submicrometer alumina

Commercially available alumina powder with high-purity submicrometer particle size and narrow particle size distribution was fully densified by a microwave hybrid fast firing technique. The alumina compacts were surrounded by susceptor material, which helped the heating of the samples, and sintered in a microwave oven at a frequency of 2.45 GHz and a power level of 1.8 kW. The sintered samples reached densities of 99% in sintering cycles of 30 to 40 minutes, a much shorter time than conventional sintering processes. The sintered samples showed uniform microstructures with powder particle size/average grain size rations higher than 1:2

INVESTIGAÇÃO DA INFLUÊNCIA DA DOPAGEM DE CONDUTORES PROTÔNICOS DE CERATO DE BÁRIO

Com a crescente demanda para sistemas de energia eficientes e ambientalmente amigáveis, a conversão direta de combustíveis gasosos em eletricidade por células combustíveis recebeu tremenda atenção nas últimas décadas. Sendo assim, o estudo da síntese e sinterização do cerato de bário, um dos materiais mais promissores entre as células combustíveis, é de suma importância para aperfeiçoá-lo ao se obter novos pós e microestruturas diferenciadas, tornando essas células economicamente viáveis.  A síntese pelo método de precursores poliméricos foi utilizada para o estudo da influência da dopagem do BaCeO3 com Y3+ como substituição parcial ao íon Ce4+. Os pós sintetizados foram caracterizados por análise térmica diferencial, difratometria de raios X, microscopia eletrônica de varredura,  e por BET. Os resultados mostraram que foi possível obter BaCeO3 dopadas com Y3+ , que o método de síntese favoreceu na formação da fase a 900 °C/2h e que o efeito da dopagem com o Y3+ no cerato de bário (BaCeO3) favoreceu na redução do tamanho médio das partículas  de 182 nm (sem dopante) para 94 nm (com o 20% Y3+ )