Graded Cellular Ceramics from Continuous Foam Extrusion

Abstract

Cylindrical SiOC foam filaments with a radial gradient in pore cell size were processed by continuous extrusion foaming of a methyl polysilsesquioxane. Upon leaving the extrusion nozzle foaming was initiated by pressure release which caused precipitation of supersaturated carbon dioxide from the polymer filament. Rapid cooling of the thin filaments generates a radial gradient of melt viscosity which gives rise for formation of closed cell morphology of isotropic pore cells in the core (diameter < 200 µm) and non‐isotropic pore cells near the sur‐face (shell; <20 µm). After pyrolysis at temperatures ranging from 800 to 1400 °C the stabilized polymer gradient foams were converted into closed cell SiOC ceramic gradient foams. XRD reveals the SiOC residue to be amorphous up to 1200 °C whereas crystallization of ß‐SiC was observed at 1400 °C. A superior compressive strength of 9 MPa and a Young´s modulus of 7 GPa at a relative density of 0.18 were measured at an optimum pyrolysis temperature of 1000 °C.

Ceramics for Sustainable Energy Technologies with a Focus on Polymer-Derived Ceramics

“…Due to the foaming process (pore forming and release of gas), the formation of a gradient structure is often the case. These gradient structures, if properly controlled, are of interest for filtering applications or for thermal insulation Ceron-Nicolat et al 2012). …”

Closed porosity ceramics and glasses

“…The last PBA technique is the compressed gas injection. For now, it was performed only on the preceramic polymers (PPs) in which the gas solubility and the molecule size (the small molecule diffuses much faster) in the liquid system found to be effective for final pore characteristics . In a basic description, PPs were first saturated by CO 2 , followed by heating and/or rapid pressure drop initiating foaming and finally pyrolysis at high temperature resulting in the microcellular ceramic .…”

“…In a basic description, PPs were first saturated by CO 2 , followed by heating and/or rapid pressure drop initiating foaming and finally pyrolysis at high temperature resulting in the microcellular ceramic . The process was also adapted to a technical scale, that is extrusion coupled with simultaneous foaming by dissolved CO 2 , and obtain diverse‐shaped closed porosity polymer‐derived ceramics (PDCs) …”

3D Printing of Complex‐type SiOC Ceramics Derived From Liquid Photosensitive Resin

“…For instance, Bruno et al . obtained superior mechanical properties of SiOC materials by extrusion . Zhang et al .…”

“…For instance, Bruno et al obtained superior mechanical properties of SiOC materials by extrusion. [9] Zhang et al reported the hierarchically ordered structures of a SiOC monolith by a freeze-casting method, which is favorable in applications such as gas separation and liquid filtration. [10] Tatsuhiro et al reported to prepare SiOC ceramics with excellent oxidation resistance using a direct foaming method.…”