Ceramics-Silikáty 59, (2) 90 - 95 (2015)

Open-cell alumina foams were prepared using the appropriate alumina slurry and polyurethane sponge with linear pore density of approximately 14 pores per inch (ppi) as a template by the replica method. The rheological studies showed that the optimum solid content for the slurries without deflocculants was 60 wt.%. In order to increase the slurry solid content, Tiron (1,2-dihydroxy-3,5-benzene disulfonic acid disodium salt) was used as dispersant. To determine the optimum concentration of dispersant, the viscosity curves of alumina slurries containing different values of Tiron from 0 to 1.2 wt.% (based on dry material weight) were studied. The optimum concentration of Tiron obtained for lowest viscosity was 0.8 wt.%. Thus, the solid content in the slurry could be increased from 60 to 66 wt.%. The effect of increase in the slurry solid content and the way it affects the foam structure and the mechanical strength were investigated. Microstructural observations of the foams show a significant reduction in macroscopic and microscopic defects in the foam struts when the slurry solid content is increased. Total porosity of the produced alumina foams prepared using slurries containing 60 and 66 wt.% solid are 83.3 and 80.4 %, respectively, while the compressive strength of the foams has increased from 1.33 to 3.24 MPa.