Control of pore structures and sizes in freeze cast ceramics

Abstract

Freeze casting of aqueous ceramic suspension was investigated as a method for preparing porous ceramic with interconnected, aligned lamellar pores. The manipulation of the pore structures and sizes by adjusting the processing parameters was studied. Al₂O₃ suspensions with different viscosities were prepared by controlling the solid loadings and particle sizes. Larger lamellar pore width and thinner lamellar ceramic wall without any defect were achieved by the utilisation of microsized Al₂O₃ powder. Lamellar pore width, ceramic wall thickness and porosity can be tailored ranging from 12 to 49 μm, 4–26 μm and 37·4–56·2% respectively by changing the cooling rates. The incorporation of organic additives can modify not only the pore size but also the pore morphology. Double templates resulted in the coexistence of lamellar pores and large pores. The ability to produce an oriented long range ordered architecture and its manipulation flexibility indicated the potential of this method for different needs in application.

Keywords:

• Porous structures
• Biomimetic ceramics
• Orientation
• Aligned structures

The authors are grateful to the PhD Programs Foundation of the Ministry of Education of China (grant nos. 20110162130003 and 20110162110044), the National Natural Science Foundation of China (grant nos. 51172288 and 51072235) and Hunan Provincial Innovation Foundation for Postgraduate (grant no. CX2011B113) for the financial support.