Ceramic Bodies with Complex Geometries and Ceramic Shells by Freeze Casting Using Ice as Mold Material

Abstract

Ceramic bodies with a complex shape and closed ceramic shells encapsulating other components like steel parts were fabricated by the freeze‐casting technique using ice as a mold and as core material. The ice molds and cores were simultaneously removed with the frozen suspension liquid of the ceramic slip by subsequent freeze drying. In this way, cores can be eliminated from a closed shell by sublimation through the porosity of the shell. Moreover, the ice cores allowed to transfect other components into porous ceramic bodies. Complex dental parts such as steel rods encapsulated in porous zirconia shells achieved by this ice mold freeze casting are represented in this article.

Recent trends in shape forming from colloidal processing: A review

“…The second type of porosity, over 40¯m, corresponds to the aligned channels of the ice formed during solidification and particle rejection and depends on the suspension concentration and the freezing rate. Similar microstructures were reported by Moritz et al 69) who prepared hollow pieces of alumina using ice templating, with densities around 8389% of the theoretical value and open porosity of 812%, separated in the same type of pore size found by Fukasawa et al: 80 nm pores, depending on the particle packing and size, and 110¯m pores, that since they are due to the ice crystal formation, disappeared with the addition of glycerol, leading to a more homogeneous microstructure. The problem that could appear is the occasional delamination of the piece as a consequence of the subsequent steps of covering, in which of those the ice crystallize in a different way.…”

“…But the freezing device can be modified to produce more complex structures, as it has been reported in the tape freeze casting 59) to produce thin substrates with acicular pores perpendicularly aligned to the blade since the refrigeration takes place under the tape. Another example is ice templating to prepare hollow ceramic pieces or with encapsulated compounds 69) or to prepare negative molds of the desired shape. 66) This requires the preparation of ice cylinders from distilled water in molds, although if a compound has to be encapsulated, it would be immersed alternatively in liquid nitrogen and water until growing the desired thickness of the ice layer.…”

Freeze‐Casting of Porous Ceramics: A Review of Current Achievements and Issues

“…1 for references). No interconnected porosity was found in the studies of Sofie [12] (addition of glycerol) and Moritz [69,70] …”

Potential Bone Replacement Materials Prepared by Two Methods

“…water), is directionally frozen in a mold, then sublimated to remove the frozen liquid phase and sintered to densify the porous ceramics [16]. Several research groups have developed varying techniques for freeze-casting biocompatible ceramics, such as HA, for potential tissue engineering applications [17][18][19][20][21][22][23][24][25][26][27][28][29].…”