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

Abstract

Freeze‐casting, the templating of porous structures by the solidification of a solvent, have seen a great deal of efforts during the last few years. Of particular interest are the unique structure and properties exhibited by porous freeze‐casted ceramics, which opened new opportunities in the field of cellular ceramics. The objective of this review is to provide a first understanding of the process as of today, with particular attention being paid on the underlying principles of the structure formation mechanisms and the influence of processing parameters on the structure. This analysis highlights the current limits of both the understanding and the control of the process. A few perspectives are given, with regards of the current achievements, interests and identified issues.

Biomimetic superelastic graphene-based cellular monoliths

“…We explored a versatile, readily accessible and inexpensive solutionphase materials shaping technique, namely freeze casting, to explore the possibility of assembling graphene sheets into corklike monoliths. Previous studies have demonstrated that when an aqueous suspension of nanoparticles is frozen, phase separation can result in the rejection of solid nanoparticles from the forming ice, which are then accumulated between the growing ice crystals 28,29 . If the fraction of nanoparticles is higher than the percolation threshold, the entrapped particles can form a continuous 3D network.…”

“…Freeze casting has been successfully adopted to synthesize a variety of porous ceramic, metallic, polymeric and composite materials, including carbon nanotubes or graphene-based polymer composites 18,[30][31][32][33] . Although previous research on freeze casting has been centred on polymers and spherical particles 28,29 , we were particularly interested in studying how 2D graphene sheets interact with anisotropic ice crystal growth without the interference of other polymer or surfactant additives. In this work, GO, which can be readily produced from graphite in large quantities 2 , was chosen as a precursor to synthesize graphene-based monoliths.…”

“…The porous structure resulted from the freeze-casting method is governed by complex and dynamic liquid-particle and particle-particle interactions 28 . We found that the amount of oxygen-containing groups of GO has a significant effect on such interactions.…”

“…1d, upon freezing, the partially reduced GO sheets are rejected from the forming ice and entrapped between neighbouring ice crystals to form a continuous network whose structure is determined by ice crystal template. As the growth rate of ice crystals is highly anisotropic (varied by 2-3 orders of magnitude along different growing directions 28,29 ), the 2D pr-GO sheets are forced to align along the moving solidification front, while they are concentrated and then squeezed at the crystal boundaries, yielding a highly ordered layered assembly. Furthermore, because the p-p attraction between pr-GO sheets is enhanced as a result of partial reduction, the as-formed network was found to be quite stable and could maintain its structural integrity upon thawing.…”

A Study on the Manufacturing of Through-Hole Al2O3 Scaffolds with Ceramic Powders in Different Grain Diameters

“…Besides being as environmentally-friendly as freeze casting, it can be used to any material. For example, the shape and size of porous structure can be controlled precisely with ceramic materials, polymer materials, metal materials and composites [5], [6].…”