Fabrication of Microcellular Ceramics Using Gaseous Carbon Dioxide

Abstract

A microcellular ceramic with cell densities >109 cells/cm3 and cells <10 μm was made with a preceramic mixture of polycarbosilane and polysiloxane. The preceramic compact was saturated with gaseous CO2, a large number of cells were nucleated and grown by using a thermodynamic instability induced by a rapid pressure drop, and the microcellular preceramic was transformed into a microcellular ceramic by pyrolysis.

Processing and properties of polysiloxane-derived porous silicon carbide ceramics using hollow microspheres as templates

“…[1][2][3][4][5][6] Since the open and closed porosity, pore size distribution and pore morphology in porous ceramics is related directly to their ability to perform a desired function in a particular application, there is a need to control these characteristics in order to achieve these superior properties. [7][8][9] All these characteristics are in turn strongly influenced by the processing route and templates used for producing porous ceramics. * Corresponding author.…”

Processing of microcellular silicon carbide ceramics with a duplex pore structure

“…: +82 55 280 3534; fax: +82 55 280 3399. nucleating and growing a large number of bubbles using thermodynamic instability by a rapid pressure drop or heating; and transforming the microcellular preceramics into microcellular ceramics by pyrolysis and optional subsequent sintering. 27,28 The second strategy involves forming certain shapes using a mixture of preceramic polymer and expandable microspheres; foaming and cross-linking the compact by heating; and transforming the foamed preceramics into microcellular ceramics by pyrolysis. 29,30 The third strategy involves simple pressing of a silicone resin powder mixed with polymer microbeads as sacrificial templates.…”

Processing of Open‐Cell Silicon Carbide Foams by Steam Chest Molding and Carbothermal Reduction

“…P receramic polymers have unique polymeric properties that are not found in ceramic powders, such as appreciable plasticity, in situ gas evolution ability, appreciable gas solubility, and good solubility in organic solvents 1–5 . Typical examples of processing strategies for porous ceramics utilizing the above properties are the direct foaming of preceramic poymer/polyurethane solutions, 1,6,7 self‐blowing of a poly(silsesquioxane) melt, 3,8 and direct foaming of preceramic polymers using CO 2 4,9 .…”

“…P receramic polymers have unique polymeric properties that are not found in ceramic powders, such as appreciable plasticity, in situ gas evolution ability, appreciable gas solubility, and good solubility in organic solvents 1–5 . Typical examples of processing strategies for porous ceramics utilizing the above properties are the direct foaming of preceramic poymer/polyurethane solutions, 1,6,7 self‐blowing of a poly(silsesquioxane) melt, 3,8 and direct foaming of preceramic polymers using CO 2 4,9 . Various plastic‐forming technologies can also be applied to preceramic polymers with or without ceramic fillers to produce ceramic foams; for example, compression molding, 10,11 extrusion, 5,12 rapid prototyping, 13 and injection molding 14,15 .…”