Shaping of porous alumina bodies by freeze casting

Porous ceramic materials have been thoroughly developed due to the wide number of applications in different areas, such as filters for environmental clean-up and reuse, bioreactors, gas or chemical sensors and support materials for catalysts or absorbents. One of the forming methods that can be selected for these applications is the freeze drying of suspensions. This method has received increased attention for manufacturing near net shaped parts with directional porosity. This work deals with the manufacture of porous alumina bodies by a freeze casting route. The different parameters of the process, such as the solids content of the suspension, the addition of cryoprotector (glycerol) and the freezing conditions (temperature and device) have been studied to determine their influence on the microstructure, density and porosity of the green and sintered pieces. Materials with different degrees of porosity and distribution of pores (aligned in the freezing direction or homogeneously distributed) have been obtained.