Effects of Coarse Particles on the Gelcasting of Ceramic Foams

In order to study the effects of coarse particles on the gelcasting of ceramic foams, a coarse powder with a similar sintering ability as that of fine powder was designed. It was prepared by grinding the presintered foams manufactured using fine powder and by sieving with 200‐mesh sieves. The resultant coarse powder was mixed with the fine powder to manufacture ceramic foams by direct foaming and the gelcasting method. The viscosities of suspensions with different fractions of coarse powder were close to each other at high shear rates. The flexural strength of the foams obtained by the mixed powders was about 10 MPa, which was about 25% lower than that obtained by the fine powder, while the permeability of the foams by mixed powders was about 30% higher than that without coarse powder. On the other hand, both the flexural strength and the permeability of the foams by the mixed powders had no clear relation with the fraction of coarse powder when it varied in the range of 5%–40%.