Abstract
SiC-based fibers, eleven in total, derived from polycarbosilane pyrolysis and belonging to the three different generations, were fully converted into microporous carbon after selective etching of silicon atoms under pure chlorine flow at intermediate temperatures (550–850 °C). In this work, relationship between as-received fibers and their subsequent carbide-derived carbon (CDC) properties, pore structure oxidation resistance and mechanical properties, was investigated. The resulting carbon is microporous or micro-mesoporous with equivalent specific surface area exceeding 1000 m2 g−1 and pore size distribution (PSD) related to the substrate chemical composition and microstructure of former fibers. Oxidation kinetics were found to depend on this PSD. The former sp2 carbon free network of fibers remained unaffected by the chlorination. Its amount and percolation were respectively correlated to Young modulus and tensile strength of CDC. This carbon thus displays a nano-composite-like behavior with a former etched carbide matrix (transformed SiC and SiCO) and carbon free reinforcement. The results demonstrate CDC allows the control over pore size and mechanical properties by selecting an appropriate multiphasic substrate, combining etched and non-etched compounds.
Highlights
Introduction sentenceThe paper reports a comparative study between various SiC-based fibers (11 in total) and their corresponding derived carbon, obtained by chlorination treatment at intermediate temperatures
The results demonstrate carbidederived carbon (CDC) allows the control over pore size and mechanical properties by selecting an appropriate multiphasic substrate, combining etched and non-etched compounds
The pore size was found to be correlated to the oxygen content of as-received fibers: second and third generation fibers gave carbon revealing ultramicroporosity whereas carbon derived from first-generation fibers showed pore enlargement, up to mesopores
Summary
The paper reports a comparative study between various SiC-based fibers (11 in total) and their corresponding derived carbon, obtained by chlorination treatment at intermediate temperatures. Carbon derived from silicon carbide-based fibers is micro-mesoporous with size distribution related to the substrate chemical composition and composite-like mechanical properties: amorphous SiC/SiCO-derived carbon reinforced with sp carbon-free network. In the last two decades, carbide-derived carbon (CDC) has gained much attention for many applications like gas storage, adsorbent, catalyst support, electrode or supercapacitor. They are produced by extraction, layer by layer, of metallic atoms from carbide leaving a carbon skeleton. Process is associated with the following equation: SiC(s) + 2Cl2(g) → SiCl4(g) + C(s)
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