Processing of Ceramic Foams with Hierarchical Cell Structure

Abstract

Silicon carbide‐based cellular ceramics characterized by a hierarchical pore structure were processed. An open‐cellular PU foam template with a mean cell density of 10 pores per inch (ppi), equivalent to a cell diameter of 4 mm and a strut thickness of 250 µm, was coated with a primary SiC slurry. Cross‐linking of a polysiloxane binder at 190 h resulted in a SiC filled reticulated thermoset foam (first generation). Subsequently, this matrix foam was infiltrated with a second slurry of slightly different polysiloxane composition which upon heating to 290 °C caused bubble nucleation and formation of a second generation foam filling the cell space in the matrix foam skeleton. After pyrolysis at 1000 °C a SiC/SiOC reaction bonded composite foam with a hierarchical cell structure and a fractional density of 0.31 was obtained. SEM and X‐ray µ‐CT analyses confirm both generations of matrix as well as infiltrated foam to be open cellular but with a pronounced difference in cell size (matrix foam cell size 2.5 mm versus infiltrated foam cell size 0.29 mm). While the matrix foam skeleton provides control of macroscopic shape as well as density distribution in the component, single‐ or multistep foam infiltration may offer a high potential for improving the mechanical properties of hierarchical cellular materials. Thus, hierarchical structure formation offers a high potential to fabricate low density cellular ceramics which might be of interest for lightweight design of novel engineering materials.

Reticulated Replica Ceramic Foams: Processing, Functionalization, and Characterization

“…[66] Ceron et al and Krishnan et al described in refs. [95,96] the volume fraction F slurry of a slurry a impregnating the polyurethane foam template as…”

Processing and characterization of polymer derived SiOC foam with hierarchical porosity by HF etching

“…Indeed, in the latter case, the foam struts are hollow which make the structure weaker. 19), 20) The linear shrinkage during pyrolysis is ³37%. As expected, PDCF is amorphous in nature up to 1573 K as shown in Fig.…”

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

“…This process predominantly yields open-cell structures with a high pore connectivity. Slurries of preceramic polymers with active or inert fillers are widely used for the impregnation of polymer preforms to form ceramic foams (Adam et al 2014;Krishnan et al 2014;Ceron-Nicolat et al 2010;de Sousa et al 2008). …”

“…In the subsequent foaming process, the cell size of the "filled" foam was retained and a secondary pore system was formed with significant smaller cells of about 0.5-1 mm in diameter (Ceron-Nicolat et al 2010). Those hierarchical structures are of increasing interest for hosting active materials including applications for heat storage or heterogeneous catalysis.…”