Silicon oxycarbonitrides synthesized by ammonia-assisted thermolysis route from polymers: A total X-ray scattering, solid-state NMR, and TEM structural study

Combined pyrolysis-ammonolysis treatment to retain C during nitridation of SiBOCN ceramics

“…Some authors have been reported the synthesis of stable microporous oxycarbonitride ceramics through ammonolysis of a polycarbosilane polymer where the micropores seem to be formed at the intermediate steps of the heat treatment by the creation of more robust units composed by SiNSi and SiCSi bonds rather than siloxane counterparts. 14) In the TAP system, the transient porosity created during pyrolysis may be reinforced in SiN and SiC units and thus be also the responsible of the retention of some mesopores at thermolysis temperatures above 1373 K.…”

“…13) This strategy has been successfully employed to synthesize microporous silicon oxycarbonitride ceramics from polycarbosilanes possessing open porosity in the range of ultramicropores, opening the door of new potential application of these materials in the field of gas separation. 14) Nevertheless, thermolysis of preceramic polymers under a NH 3 atmosphere leads to the elimination of most of the carbon through chemical transformation of SiH, SiCH 3 and SiCH=CH 2 bonds to imidonitride groups at temperatures probably below 750 K. 13), 15) During ammonolysis, the reaction of NH 3 with the carbon functionalities in the low temperature regime of the polymer-toceramic conversion 16) gives as a result a significant decrease of the carbon content in the final ceramic. The formation of BC 3 and BCN environments are less likely to occur.…”

“…Schitco et al 14) assigned the signal appearing at about ¹83 ppm to [SiO 2 N 2 ] units in silicon oxycarbonitrides synthesized from preceramic polymers heat treated in an NH 3 atmosphere whereas the simulation of 29 Si NMR spectra of silicon nanoparticles suggest that this feature might be due to SiH containing moieties, especially [(SiO) 3 Si H].…”

Microporosity and CO2 Capture Properties of Amorphous Silicon Oxynitride Derived from Novel Polyalkoxysilsesquiazanes

“…Micro and mesoporous structure formation through the polymer-derived ceramics (PDCs) [1,2] route has received increasing attention as an attractive ceramic processing route to develop gas separation membranes, gas sorbents and catalysts with thermally and/or chemically stable amorphous systems such as silicon nitride [3], silicon carbide [4,5,6,7,8,9], silicon carbonitride (Si–C–N) [10], silicon oxycarbide (Si–O–C) [11,12,13], silicon oxycarbonitride (Si–O–C–N) [14,15,16] and other quaternary Si–M–C–N (M=B, [17,18], Ni [19]). During the crosslinking and subsequent high-temperature pyrolysis of polymer precursors, by-product gases such as CO 2 , CH 4 , NH 3 and H 2 were detected, and the microporosity in the amorphous PDCs could be assigned to the release of the small gaseous species formed in-situ [14,15,16,20,21,22,23].…”

“…During the crosslinking and subsequent high-temperature pyrolysis of polymer precursors, by-product gases such as CO 2 , CH 4 , NH 3 and H 2 were detected, and the microporosity in the amorphous PDCs could be assigned to the release of the small gaseous species formed in-situ [14,15,16,20,21,22,23]. …”