Processing and Characterization of Porous Alumina Ceramics with Wide Porosity Range

Abstract

In recent years, porous ceramics with tailored microstructure has received wide attention in the research communities for its specialized properties. To have a customized microstructure suitable for different applications, several fabrication methods have also been developed during the last decades to manipulate porosity, pore size distribution and pore interconnectivity in the porous ceramics. In the present study, an attempt has been made to develop porous alumina ceramics with wide porosity (10-80%) using three different fabrication methods. The three methods are starch consolidation casting (SCC), polymeric sponge replica technique (SRT) as well as the combination of the two methods (SCC+SRT). A theoretical model has also been developed and validated with the experimental data to predict the porosity of the samples prepared by SCC theoretically. Alumina loading, starch content, starch types are used as the tools to develop different porosity in the samples made by starch consolidation casting. TiO2 has been used as sintering additives to improve high strength in the starch consolidated samples without compromising the porosity. The viscosity of the slurry in the range 0.05-1.19 Pa.s was found to be optimum to fabricate defect free samples by starch consolidation casting. The porosity of the samples could be varied from 20-70% in this technique. TiO2 as sintering aid was able to reduce the sintering temperature of the samples in the tune of 300oC without compromising the strength and porosity of the samples fabricated by this technique. It was observed that 10% porous samples could be developed through this technique. Particle loading of the slurry was found as an important parameter to develop different pore morphology when the samples prepared using sponge replica technique. The porosity of the samples could be varied from 75- 80% of strength 0.31-2.46 MPa by this technique. An attempt has also been made to develop hierarchical porosity in the samples while fabricated by the combination of the above two techniques. The microstructural study revealed the formation of hierarchical porosity in the samples fabricated by the combination technique. Thus, porous ceramics with porosity in the range these techniques could achieve 10-80%.