Gas-filled microspheres as an expandable sacrificial template for direct casting of complex-shaped macroporous ceramics

Expandable microspheres have been used as a sacrificial template to produce macroporous ceramic materials by a gel-casting process. The temperature range for the gel-casting process has been tuned to allow the gas-filled polymer spheres to expand prior to the setting of the powder body. It is demonstrated that by controlling the amount and size of the expandable microspheres it is possible to tune and tailor the porosity up to 86% and the pore size distribution from 15 up to 150 μm. The expandable microspheres add a relatively low amount of organic material that allows rapid and facile burn-out. The temperature-induced expansion of the microspheres and the associated volume increase of the suspension has been used as a simple zero-pressure near-net shaping method to yield complex-shaped macroporous alumina bodies.