Production of alumina ceramics with graded porosity using the slip casting technique

Reference	Presenter	Authors (Institution)	Abstract
17-057	Gustavo Antoniácomi de Carvalho	de Carvalho, G.A.(Universidade Estadual de Ponta Grossa); Chinelatto, A.S.(Universidade Estadual de Ponta Grossa);	Porous ceramic materials are getting more attention due to the refractory, thermal insulation, gas permeability, mechanical resistance and chemical inertness. Among porous materials there is also special attention to the study of functionally graded porous materials, in which the porosity and pore morphology changes through the volume of the material. These materials have diverse applications, like fuel cell porous supports, ceramic catalysts and filters. Among the common used methods for the processing of porous ceramics is the slip casting process. This processing method uses volatile precursors to form the pore structure, added to the slip with the material and then volatilized during the sintering process. One of the most studied materials used in porous ceramics is alumina. It is used mainly due to its high mechanical resistance, allowing materials with high porosities to be applied. This work aims the processing and characterization of graded porous ceramics through the slip casting process using sequential castings and aluminum hydroxide as volatile precursor and as an alumina precursor. For the processing of the graded ceramics different slips were used with different proportions of alumina and aluminum hydroxide, aiming for the increase of porosity through the material volume. The proportions of aluminum hydroxide used were 0% to 75%. Each of the slips were also processed isolated from the other layers. After casting, the samples were sintered at 1500oC for 2 hours, using a heating rate of 10oC/min. The pore structure was characterized by mercury porosimetry in pore size and pore size distribution. The pore morphology was observed using scanning electron microscopy and the mechanical resistance was measured using compression test. The results showed that with the increase in aluminum hydroxide in the slip, the apparent porosity also increased from 5% to 39% as expected and the method used was effective in producing samples with graded pore structure.
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