Effect of polyethylene glycol on the microstructure of freeze-cast alumina

Abstract

Freeze casting has been used to process a range of ceramics with oriented pore structures, and soluble polymers are often used to improve the strength of the material before sintering. This study examined the effect of polyethylene glycol (PEG) on the three distinct microstructural scales, which include the colony size, the pore size, and the secondary dendrite spacing. The results showed that the trends in pore size and secondary dendrite spacing were consistent with the effect of constitutional supercooling on the growth of ice crystals. In contrast, the effect of PEG on colony size appeared to be more pronounced and may reflect preferential adsorption on the prism faces of the growing ice crystals. For both alumina and PEG content, the observed effects were very much dependent on the temperature of the chill surface used in casting. © 2008 The American Ceramic Society.