Novel SiC/C Aerogels Through Pyrolysis of Polycarbosilane Precursors

Abstract

A new approach for forming aerogels with various silicon-based compositions and hybrids between ceramics and carbon has been developed by combining efficient hydrosilylation as the hybridizationcrosslinking approach associated with gelation in the presence of solvent and followed by supercritical drying techniques. Highly porous carbon-enriched SiC/C aerogels with adequate mechanical durability have been synthesized, pyrolyzed, and characterized. The "wet" gels were obtained by crosslinking a commercial polycarbosilane with divinylbenzene via Pt-catalyzed hydrosilylation reaction in highly diluted condition (90 vol% of solvent). A supercritical drying was performed after exchanging the solvent (cyclohexane) with liquid CO 2 forming undamaged aerogels. A subsequent pyrolysis and heat treatment (up to 1500°C) in argon flow converted the polymeric aerogel into a SiC/C-based material with bulk density of 166 kg m À3 , SSA of 444 m 2 g À1 , a micro-meso pore volume of 0.79 cm 3 g À1 , total porosity above 90 vol% and ultimate compressive strength of 1.6 MPa. The final product was compared to its cured gel and intermediates obtained during the pyrolysis process.

Polymer‐derived ceramic aerogels as sorbent materials for the removal of organic dyes from aqueous solutions

“…The SiC aerogels were prepared from a liquid allylhydridopolycarbosilane (SMP‐10, Starfire Systems, Schenectady, USA), while for the SiOC aerogel a linear poly(methylhydridosiloxane) (PMHS, MW~1900, CAS: 63148‐57‐2, Alfa Aesar, Ward Hill, MA, USA) was used. Details of the synthesis of the preceramic aerogels can be found in the literature . The preceramic samples were converted in the corresponding PDCs by a pyrolysis process in controlled atmosphere (Ar, 100 cm 3 /min).…”

“…Consequently, PDCs fibers, films, ceramic matrix composites, MEMS, and a variety of macro‐, meso‐, and micro‐porous ceramics (even with lotus‐type porosity) have been obtained via the PDC route and several comprehensive reviews are available on this topic . Concerning the processing of porous materials, the synthesis of PDC aerogels has been recently proposed by some of us and SiC, SiOC, and SiCN aerogels have been obtained and characterized …”

“…In our laboratory, porous PDCs aerogels showing hierarchical porosity ranging from some microns to few nanometers and with high SSA in the range 100‐700 m 2 /g have been recently synthesized . Moreover, their structure contains different types of chemical bonds (Si–O, Si–N, Si–C, C=C, C=O) and functional groups (OH, NH, COOH) depending on the composition and pyrolysis atmosphere . This unique combination of hierarchical porosity, high SSA and broad range of surface chemical functionalities makes the PDC aerogels ideal candidates as sorbent materials for water purification.…”

“…[19][20][21] Concerning the processing of porous materials, the synthesis of PDC aerogels has been recently proposed by some of us 22 and SiC, SiOC, and SiCN aerogels have been obtained and characterized. [23][24][25] The treatment of industrial wastewater deriving from textile sector is an important issue for the quality of wastewater generated. In fact, about 30% of the dye used in the textile process is deactivated, thus causing the discharge of dyes in wastewater at amounts of tens of mg/L.…”

“…42 Moreover, their structure contains different types of chemical bonds (Si-O, Si-N, Si-C, C=C, C=O) and functional groups (OH, NH, COOH) depending on the composition and pyrolysis atmosphere. 23,24,43 This unique combination of hierarchical porosity, high SSA and broad range of surface chemical functionalities makes the PDC aerogels ideal candidates as sorbent materials for water purification. In this work, we proposed to use SiC, SiOC aerogels, and a PDC SiC foam as adsorbents for organic dyes to purify contaminated water and we compared their behavior with a commercial mesoporous silica.…”