Investigations of ice‐structuring agents in ice‐templated ceramics

Abstract

The freeze-cast ceramics process involves the use of an aqueous slurry in which ice acts as a fugitive template, providing control of the morphology of the resultant green body, which is then sintered. Here we report the role of various additives and procedures in tailoring the morphology of ice-templated, freeze-cast alumina ceramics. We show that zirconium acetate (ZrAc) in the slurry can change the structure from lamellar to columnar, whereas polyvinyl alcohol can act as both a binder and as a modifier of the ice surface, and can compete with ZrAc to provide cooperative effects and a wide range of porosities. We also show that the ceramic structure can be influenced by epitaxial growth on an oriented layer of ice. K E Y W O R D Sgel casting, pores/porosity, processing

Freeze-casting applied to ceramic materials: a short review of the influence of processing parameters

“…Polyvinyl alcohol (PVA) is an organic binder used to strengthen the green body and also control the final pore size. According to White et al [81], the increase in PVA content decreases pore size and favors the formation of dendritic structures with a higher degree of branching [82]. PVA is believed to favor the formation of dendritic crystals due to its antifreeze properties that lead to disturbances at the water-ice interface and higher supercooling [81].…”

“…According to White et al [81], the increase in PVA content decreases pore size and favors the formation of dendritic structures with a higher degree of branching [82]. PVA is believed to favor the formation of dendritic crystals due to its antifreeze properties that lead to disturbances at the water-ice interface and higher supercooling [81]. Due to the PVA addition to the suspension, there is an increase in the viscosity of the suspension, and a gelling process at relatively high temperatures can occur.…”

“…Water Gelatin Sucrose ice crystals with subsequent formation of homogeneous pore morphology. Published studies [80,81] showed that the addition of zirconium acetate (ZrAc) to the suspension changed the lamellar pore structure to a columnar structure. Besides, the presence of a zirconium acetate complex in the suspension results in a honeycomb-like pore morphology [80].…”

Hierarchical Assembly of Surface Modified Silk Fibroin Biomass into Micro‐, and Milli‐Metric Hybrid Aerogels with Core‐Shell, Janus, and Composite Configurations for Rapid Removal of Water Pollutants

“…[22][23][24] By applying the temperature gradient to the slurries with constituents mentioned above and systematically controlling the ice crystal growth behavior, various structural morphologies such as lamellar, honeycomb, and brick and mortar patterns have been developed after drying and removing the ice template. [25,26] In comparison to the solgel process and other soft or hard templates, directional freeze casting offers cost-effective, simple, and versatile processing opportunities. Furthermore, the ice template can also act as a driving force for the microstructure formation, often called cryo-assembly.…”

Applications of ice‐templated ceramics

“…control the microstructure of the resultant product, which is generally sintered in the final preparation stage. In our recent studies, we have investigated in detail the role of ice‐structuring agents in formation of ice‐templated ceramics, with an emphasis on freeze‐cast alumina . The present work focuses on diverse applications of freeze‐cast ceramics.…”