High surface area SiC(O)‐based ceramic by pyrolysis of poly (ethylene glycol) methacrylate‐modified polycarbosilane

Abstract

In the present work, a high surface area SiC(O)‐based ceramic powder was synthesized upon thermal transformation of a polymer‐derived macromolecular precursor, which was obtained by the chemical modification of a allylhyldrido polycarbosilane with poly(ethylene glycol) methaacrylate under argon environment. The pyrolysis of developed precursor led to the formation of amorphous and high surface area SiC(O)‐based ceramic powder with in situ generated micro/meso‐porosity. The specific surface area of the obtained powders depends on the processing temperature. It decreases from 363 to 122 m2/g as the pyrolysis temperature increases from 600 to 1200°C, respectively. Furthermore the promising samples were fabricated using pressing technique, which led to crack‐free SiC(O) monoliths on subsquent heat treatment. The present study also emphasizes the potential of produced SiC(O) ceramic powder to support NiO catalyst. The impregnation method were used to produce high surface area NiO@SiC(O) ceramic powder (NiO as a catalyst; SiC(O) as a catalyst support) for further catalytic applications. Interestingly, the distribution of the NiO was shown to strongly depend on the oxygen content present in the SiC(O) matrix. Thus, larger oxygen contents induce homogeneously distributed flower‐like NiO catalyst onto SiC(O).

Synthesis of Porous Ni/SiC(O)‐Based Nanocomposites: Effect of Nickel Acetylacetonate and Poly(Ethylene Glycol) Methacrylate Modification on Specific Surface Area and Porosity

“…Furthermore, nickel acetylacetonate helps to increase the cross-linking degree of preceramic precursor and it helps to avoid the collapse of formed porosity up to higher temperature. [24] Therefore, the results obtained clearly show that high SSA Ni/SiC(O)-based nanocomposites can be prepared by chemical modification of polycarbosilane. The decomposition of the modified precursor increases the surface area of formed ceramic nanocomposites with the evolution of gaseous species, whereas a better cross-linking helps to retain it until high temperature.…”

“…The decomposition of organic groups (acetylacetonate and ethylene glycol methacrylate) helps to nucleate porosity in the final ceramic nanocomposites. Furthermore, nickel acetylacetonate helps to increase the cross‐linking degree of preceramic precursor and it helps to avoid the collapse of formed porosity up to higher temperature …”

“…Figure shows the N 2 adsorption–desorption isotherms of produced samples pyrolyzed at different temperatures. The SMP‐10‐based samples without modification and pyrolyzed at 600 °C is a nonporous materials, whereas SMP‐10 modified with PEGM leads to a micro‐mesoporous materials . Furthermore, the Ni‐SMP samples pyrolyzed at 600 °C have a typical type I isotherm for microporous materials.…”

“…Therefore, Ni/SiC(O) ceramics obtained by pyrolysis of 45 Ni‐SMP at 600 °C contain micropores, whereas 45 Ni‐SMP‐PEGM contains micropores as well as mesopores. The reason behind the generation of microporosity is the production of small fragments (H 2 , SiH 4 , CH 3 SiH 3 , CO 2 , C 2 H 4 , and CH 4 ), whereas the evolution of monomeric unit of PEGM is the reason behind mesoporosity in the final ceramic . On further high‐temperature treatment up to 800 °C, microporous structures collapse; however, mesoporosity is still observed.…”

“…Furthermore, nickel acetylacetonate helps to increase the cross‐linking degree of preceramic precursor and it helps to avoid the collapse of formed porosity up to higher temperature. [ 24 ]…”