Development of high strength large open porosity alumina ceramics using the sacrificial phase route: The role of the sacrificial phase fineness

Abstract

The aim of this work is to prepare porous aluminum oxide ceramics using sunflower seed husk powder mixed with polyvinyl alcohol as the pore-forming agent, uniaxial pressing for green product forming, to characterize porosity, microstructure and mechanical properties of the prepared porous alumina, and to investigate the potential effect of the particles size of sunflower seed shells powder on the physical and mechanical properties of the prepared porous alumina. The effect of pore-forming agent content within the green ceramics, in addition to its fineness, on the linear, volumetric shrinkage and the total and open porosity of the porous alumina is studied. The effect of the achieved porosity on the mechanical properties is evaluated by measuring the flexural strength. Porous microstructure and pores morphology were characterized by scanning electron microscopy to investigate the effect of pore-forming agent fineness on the size of the obtained pores. By changing the ratio of the pore-forming agent from 0 to 51 wt% in the green alumina, with fineness <90 μm, the porosity of the prepared ceramics attained values in the range 22–50 vol%, with flexural strength between 47 MPa and 186 MPa. A porosity in the range 22–74 vol% was also achieved, with flexural strength between 4 MPa and 186 MPa, by changing the proportion of the pore-forming agent from 0 to 51 wt% in the green alumina, with a fineness in the range 250–355 μm. The mechanical reliability of the prepared alumina was discussed by analyzing the flexural strength data using Weibull statistics.