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TitleNMR and X-ray diffraction studies of amorphous and crystallized pyrolysis residues from pre-ceramic polymers
Publication TypeJournal Article
Year of Publication1997
AuthorsMucalo, M.R., Milestone N.B., and Brown I.W.M.
JournalJournal of Materials Science
Pagination2433 - 2444
Date Published1997
ISSN00222461 (ISSN)
KeywordsAmorphous materials, Ceramic materials, Crystalline materials, Crystallization, Magic angle spinning nuclear magnetic resonance spectroscopy, nuclear magnetic resonance spectroscopy, Polycarbosilanes, Polysilanes, Polysilazanes, Pyrolysis, Silica, Silicon, Silicon carbide, Silicon nitride, X ray crystallography
Abstract29Si MAS NM R and X-ray diffraction studies are presented of black and white pyrolysis residues obtained by initial 1100°C pyrolyses in N2 and NH3 atmospheres followed by 1550°C pyrolyses in Ar, N2 or vacuum atmospheres of a polycarbosilane and four polysilazane precursors to SiC and Si3N4 ceramics. Amorphous white pyrolysis residues crystallized under the various conditions to give not only Si3N4 but also Si2N2O, SiC, SiO2 and Si, while black amorphous pyrolysis residues crystallized to form only Si3N4 or SiC. In general, the crystalline ceramic products observed depended on a variety of factors, i.e. moisture sensitivity of polymer, the initial 1100°C pyrolysis gas (N2/NH3), the dryness of the 1100°C-NH3 pyrolysis gas and the 1550°C pyrolysis atmosphere (N2, Ar, vacuum). An additional factor of interest affecting product distribution was the choice of crucible (alumina/graphite) employed in the 1550°C pyrolysis. The combined studies suggest that the white amorphous pyrolysis residues are complex silicon oxycarbonitrides (SixNyOzCa), while the amorphous black residues are silicon carbonitrides (SixNyCz).

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