doiSerbia

Effect of cooling rate on the microstructure and porosity of alumina produced by freeze casting

Rodríguez-Parra Jesús M. (Institute of Ceramics and Glass, CSIC, Madrid, Spain)
Moreno Rodrigo (Institute of Ceramics and Glass, CSIC, Madrid, Spain)
Nieto Isabel María (Institute of Ceramics and Glass, CSIC, Madrid, Spain)

Freeze casting is a well-known shaping technique to produce materials with directional porosity. One of the major problems is the difficulty to control the cooling rate thus leading to gradients in pore size and homogeneity. This work deals with the manufacture of alumina ceramics with directional porosity by freeze casting of aqueous suspensions. An experimental set-up was prepared in order to apply different cooling rates. Freeze casting tests were done with an aqueous alumina suspension after optimization of its rheological behavior. The porosity and microstructural features of sintered bodies produced under different experimental conditions were studied and analyzed. It is concluded that the cooling rate influences the microstructure while final temperature has a much lower influence. Also, the microstructural analysis shows that there is a gradient in the directionality of pores, being lower at the bottom and the top and higher in the central region of the specimens.

Keywords: suspensions, shaping, ceramics, porous materials, alumina, micro-structures