Obtenção e caracterização de espumas cerâmicas de alumina para uso como queimadores radiantes

AUTOR(ES)

Verónica Moreno Argüello

DATA DE PUBLICAÇÃO

2009

RESUMO

Ceramic foams are cellular porous ceramics that can be produce by different methods, like replica method, sacrificial template method and direct foaming method. Foams are a type of porous ceramic which present many properties making them a very versatile material, used in different applications, like radiant porous burners. Radiant burners consist of ceramic materials which must resist at high temperatures (>1500C) and provide high thermal shock resistance. In this work, the replication method was used to obtain alumina foams. Polyurethane foams were impregnated with aqueous suspensions of 50-70% wt. solid (Al2O3) and additives (binders and dispersants). An experimental design was made to establish the appropriate concentration of each component in the suspension. The viscosity and the thixotropy of the suspension were evaluated and adjusted to an appropriate impregnation of the polymeric foam. The impregnated foams were heat treated for degradation of polyurethane at 400C/1h and subsequently sintered (between 1500C and 1600C/3h) for densification of the struts and cell walls. The alumina foams obtained were characterized by analysis of compression strength, flexural strength at high temperature, permeability, porosity and morphology. Permeability and compressive strength of the foams were correlated to the microstructure and cellular morphology (size and geometry of the cells). Flexural strength at high temperature was used to predict the mechanical behavior of the foams when used in radiant burners. Tests on a pilot radiant burner were also performed. Different airfuel ratios and flame rates were evaluated. The sintering temperature of 1600C promoted higher densification and increase in mechanical strength. It was found that the porosity is directly related to the sintering temperature. The low mechanical strength of the ceramic foams at high temperatures may compromise their performance in radiant burners. With a 5% vol. fuel and 100% excess air mixture reagent, the flame stability at a rate of 30 to 36 cm/s was reached at temperatures higher than 1150oC.

ASSUNTO(S)

engenharia de materiais e metalurgica espuma ciencia dos materiais queimadores de gás engenharia de materiais gas-burners poliuretanas

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