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

摘要

Solid-state nuclear magnetic resonance (NMR) spectroscopy, total X-ray scattering with a pair distribution function (PDF) analysis, and transmission electron microscopy (TEM) were employed to explore the structures of microporous and non-porous ceramics synthesized by an NH3-assisted thermolysis from polymers. Polysiloxane (SPR-212a, Starfire (R) Systems) and polysilazane (HTT-1800, KiON Speciality Polymers) polymers form microporous silicon oxycarbonitride ceramics with accessible and tailored micropores. Si-29 magic-angle-spinning NMR showed that the introduction of nitrogen leads to structures incorporating considerable amounts of SiN4 and SiO2N2 building blocks. The samples derived from a polycarbosilane (SMP-10, Starfire (R) Systems) remained non-porous: for such a C-rich and N-bearing phase, the NMR, TEM, and PDF results suggested a Si network exhibiting domains dominated by either Si-N or Si-C bonds. C-13 NMR revealed primarily "carbidic" CSi4 environments in the C-rich phases, as well as the formation of an amorphous sp(2)-hybridized carbon phase; both are believed to be detrimental for the micropore formation. (C) 2015 Elsevier Ltd. All rights reserved.