Tailored Macroporous SiCN and SiC Structures for High‐Temperature Fuel Reforming

Abstract

The catalytic reforming of hydrocarbons in a microreformer is an attractive approach to supply hydrogen to fuel cells while avoiding storage and safety issues. High‐surface‐area catalyst supports must be stable above 800 °C to avoid catalyst coking; however, many porous materials lose their high surface areas below 800 °C. This paper describes an approach to fabricate macroporous silicon carbonitride (SiCN) and silicon carbide (SiC) monoliths with geometric surface areas of 105 to 108 m2 per m3 that are stable up to 1200 °C. These structures are fabricated by capillary filling of packed beds of polystyrene or silica spheres with low‐viscosity preceramic polymers. Subsequent curing, pyrolysis, and removal of the spheres yielded SiCN and SiC inverted beaded monoliths with a chemical composition and pore morphology that are stable in air at 1200 °C. Thus, these structures are promising as catalyst supports for high‐temperature fuel reforming.

Facile Synthesis of SiCN Ceramic Foam via Self-Sacrificial Template Method

“…And it was reasonable that the BET surface areas of SiCN foams with 500-nm and 1-µm pores were 184.5 and 71 m 2 /g, respectively. no weight change even up to 1000 °C in air, which was in agreement with the previous report [9]. Such a high thermal stability could not be attained in the macroporous SiCN prepared from SiO 2 sphere template, due to the damage to the SiCN product during HF etching.…”

Composition and Morphology Control in Ordered Mesostructured High‐Temperature Ceramics from Block Copolymer Mesophases

“…In the present study the prevalence of the enhanced oxygen composition in hybrids prepared under ambient atmosphere may be attributed to the employed (thin) film geometry. This is in agreement with those literature reports that do mention the reactivity with water, [13,33] all of which focus on the synthesis of small-scale structures, i.e., structures with large surfaceto-volume ratios.…”

Fabrication of Ceramic Microchannels with Tailored Pores

“…TGA of the pyrolysed SiC and SiCN structures did not exhibited any significant weight changes (~0.07 wt.% loss and ~0.09 wt.% gain for SiC and SiCN porous structures, respectively) when heated to 950°C (temperature limit of TGA apparatus) in air. NMR, XRD, and XPS data were identical to the previous report [4] and it was confirmed that the porous SiC and SiCN structures were physically and chemically stable at temperatures as high as 1200°C in air.…”