Porous Ceramics, Ceramic/Polymer, and Metal‐Doped Ceramic/Polymer Nanocomposites via Freeze Casting of Photo‐Curable Colloidal Fluids

Abstract

A novel and general process for the fabrication of porous ceramics and metal/ceramic/polymer nanocomposites by freeze‐photocuring‐casting (FPC) is presented. The homogenous fluid containing water, curable monomers, and colloidal particles is frozen, and the phase separated microstructure is fixed by photo‐initiated polymerization. At the relatively high resin/particle ratio explored here, the structure is sufficiently strong to withstand the capillary forces during ambient drying; however, it is capable of transforming to macroscopic ceramics such as Al2O3 and SiO2 by conventional debinding and sintering. The use of FPC fluids enables producing porous macroscopic shapes such as microspheres, films, and multilayer coatings having an ordered, interconnected pore network and pore sizes down to the low sub‐micrometer range. The pore structure is found to be dependent on the radius of curvature of the macroscopic structure. Ag–TiO2/polyacrylate porous nanocomposites are produced by co‐shaping of FPC containing sterically stable colloids, soluble metal salts, and monomers. Ag nanoparticles form in situ by reduction of Ag+ ions on the TiO2 surface. This triggers the photo‐polymerization of the resin without the need of a photoinitiator. It is found that if the cured layers in a multilayer stack are frozen before the newly deposited layer, the ice crystal structure formed is linked via epitaxial growth.

Photopolymerization-based additive manufacturing of ceramics: A systematic review

“…4). This suggests that when appropriate amount of PI (particularly < 5%) is used, efficient photopolymerization of ceramicpolymer matrix may be obtained [68,69]. Furthermore, when MP abstracts hydrogen from another MP (i.e., due to excessive PI), benzoylcarbonyloxy group will be formed [63].…”

Freeze casting – A review of processing, microstructure and properties via the open data repository, FreezeCasting.net

“…From the early 2000's to 2017, the number and diversity of potential applications for these materials grew considerably; applications investigated include substrates for supercapacitors [26][27][28][29][30][31][32], photocatalysis [33][34][35][36][37][38][39][40][41][42][43], liquid chromatography [44], sensors (e.g. pressure [45][46][47], biological [48] and gas [49][50][51]), and batteries [52][53][54][55][56][57][58][59][60][61][62]; biomaterials remain the most extensively investigated application. Dense composite materials may also be fabricated by infiltrating freeze-cast skeletons with a secondary phase.…”

“…Dense composite materials may also be fabricated by infiltrating freeze-cast skeletons with a secondary phase. Thus far, ceramic/metal [52,[106][107][108][109][110][111][112][113][114][115][116][117][118][119], ceramic/polymer [120][121][122][123][124][125][126][127][128][129][130][131][132][133][134][135][136][137][138], metal/polymer [139][140][141][142][143], and metal/metal [144,145] composites have been demonstrated.…”

Engineering biological gradients

“…Although different ceramics (i.e. alumina, zirconia, titanium dioxide, hydroxyapatite) [78][79][80] and bioglasses 81,82 are mainly used in freeze-casting, metals (such as ferritic stainless steel 83 ) and composite materials 77,84 can also be selected for this process. Different concentrations of hydroxyapatite and poly(lactic-co-glycolic acid) microparticles within a gelatin solution have been combined into a scaffold with tunable degrading and swelling properties, as well as strong mechanical behavior defined by the hydroxyapatite concentration.…”