Neste trabalho, filtros com estrutura fibrosa foram produzidos utilizando-se matéria-prima de baixo custo, disponível comercialmente e caracterizados para aplicações em filtração de aerossóis. Mantas refratárias sílico-aluminosas comerciais foram prensadas uniaxialmente, utilizando-se 10% em massa de acetato de polivinila como ligante. Nesta etapa, as amostras foram submetidas à compactação com diferentes pressões para obtenção de diferentes porosidades. Após a prensagem, as amostras foram submetidas a um tratamento térmico a 500 ºC durante 1 h para a degradação do polímero. Subseqüentemente, as amostras foram sinterizadas a 1200 ºC durante 1 h, resultando em uma estrutura fibrilar porosa, composta por mulita (3SiO2.2Al2O3), com porosidade na faixa de 50 a 75%. A morfologia dos filtros fibrosos foi caracterizada através de microscopia eletrônica de varredura, que revelou uma estrutura tridimensional porosa de fibras interconectadas. A resistência mecânica foi avaliada através de ensaios de compressão e de flexão em quatro pontos. Ensaios de permeabilidade e eficiência de coleta de partículas com diferentes diâmetros foram efetuados e os resultados comparados a filtros comerciais. Os valores obtidos para a permeabilidade e eficiência de coleta estão na ordem de grandeza esperada para filtros de gases, apresentando assim grande potencial para aplicações industriais.

Filters with fibrous structure were produced from low cost, commercially available raw materials and characterized for aerosol filtration. Refractory aluminosilicate fibers were uniaxially pressed with polyvinyl acetate as binder. Different pressures were applied, which yielded samples with different porosities. After pressing, the samples were heat treated at 500 ºC during 1 h in air for debinding with subsequent sintering at 1200 ºC for 1 h, which resulted in porous fibrous structures composed mainly by mullite (3SiO2.2Al2O3) with porosity in the range of 50%-75%. The microstructure of the fibrous filters was evaluated by scanning electron microscopy, which revealed a porous morphology comprised by three-dimensional interconnected fibers. Mechanical strength was measured by compressive and 4-point bending tests. Permeability and particle collection efficiency were evaluated and compared with commercially available filters. The permeability and collection efficiency values are in the order of magnitude of cellular supports for aerosol filters and, therefore, suitable for several technological applications.

Ceramic foams are a new structural material, characterized by a high porosity and a large surface area and made of megapores interconnected by filaments. This results in a structure with low resistance to fluid flow, making them appropriate for use as a filter. This work studies the influence of several structural parameters, such as porosity, tortuosity, surface area and pore diameter, in predicting the permeability of ceramic foams. Foams with different pore densities were used as porous media. Permeability was measured utilizing water as the flowing fluid. The results show that the predicted permeability scatters widely with the parameters under study. Pore diameter was the structural parameter that best represented the media. An Ergun-type correlation was fitted to the data and represented very well the permeability of the media in all foams under the experimental conditions studied.