Bi-directional freeze casting of porous alumina ceramics: A study of the effects of different processing parameters on microstructure

Intrinsic microstructural anisotropy in tape cast ceramics by ice templating

“…The significance of the solidification rate needed to match the pull rate is to facilitate the lateral ice growth along a horizontal freezing front. Freeze tape casting is in effect a kinematic bi‐directional freezing process; only instead of the temperature gradient being formed along a substrate material cooling differential, 18 the two temperature gradients are the warm air above the tape and the line where the warm granite block meets the cooled aluminum freeze bed, shown in Figure 3. Therefore, if the slurry at the horizontal solidification front is not pulled at precisely the same velocity as the ice crystal growth, the ice crystals will propagate with differing orientations since the gradient would become vertically unidirectional directly over the cold or warm bed.…”

“…In this manner axial flow behavior of fluids may be unaffected; however, transverse flow and structural ordering of ceramic columns may differ substantially for a single freeze cast domain and are therefore critical in many applications. Attempts to facilitate anisotropy in the solidification behavior of freeze casting and eliminate domain randomization include: the use of sucrose additives to grow lamellar dendrites, 16 bidirectional thermal gradients via graded material substrates, 17,18 slurry freezing under flow to align asymmetric platelet particles within a green body, 19 and the use of electric, magnetic, and acoustic fields to align particles with ice crystal growth during solidification. 20 The work presented in this study establishes the variables in processing required to cast thin ceramic tapes with cross-sections that yield a common pore orientation through the entire freeze cast specimen.…”

Cost-effective fabrication of bio-inspired nacre-like composite materials with high strength and toughness

“…Ultimately, the ceramic layer thickness was limited by the freezing rate and alumina particle size (∼0.5 µm in the present work). It was found that faster freezing rate and lower solid loading may result in thinner ceramic walls [22]. However, it was restricted by the freeze casting setup and achievable sample size.…”

“…% MgO respect to alumina as sintering aid, 4 wt.% PVA as binder, and 0.6 wt.% Dolapix CE64 as dispersant into water. After 24 h ball milling, the suspension was poured into a bi-directional freeze casting mould as previously reported [22].…”

“…Bi-directional freeze casting is a modified technique which can control lamellar orientation of scaffolds by freezing suspension from two different directions and it could be used to create ceramic scaffolds with highly aligned architecture [19,22,23]. With further densification and second phase (e.g.…”