Sugie, Casey ; Navrotsky, Alexandra ; Lauterbach, Stefan ; Kleebe, Hans-Joachim ; Mera, Gabriela (2021)
Structure and Thermodynamics of Silicon Oxycarbide Polymer-Derived Ceramics with and without Mixed-Bonding.
In: Materials, 14 (15)
doi: 10.3390/ma14154075
Artikel, Bibliographie
Kurzbeschreibung (Abstract)
Silicon oxycarbides synthesized through a conventional polymeric route show characteristic nanodomains that consist of sp(2) hybridized carbon, tetrahedrally coordinated SiO4, and tetrahedrally coordinated silicon with carbon substitution for oxygen, called "mixed bonds." Here we synthesize two preceramic polymers possessing both phenyl substituents as unique organic groups. In one precursor, the phenyl group is directly bonded to silicon, resulting in a SiOC polymer-derived ceramic (PDC) with mixed bonding. In the other precursor, the phenyl group is bonded to the silicon through Si-O-C bridges, which results in a SiOC PDC without mixed bonding. Radial breathing-like mode bands in the Raman spectra reveal that SiOC PDCs contain carbon nanoscrolls with spiral-like rolled-up geometry and open edges at the ends of their structure. Calorimetric measurements of the heat of dissolution in a molten salt solvent show that the SiOC PDCs with mixed bonding have negative enthalpies of formation with respect to crystalline components (silicon carbide, cristobalite, and graphite) and are more thermodynamically stable than those without. The heats of formation from crystalline SiO2, SiC, and C of SiOC PDCs without mixed bonding are close to zero and depend on the pyrolysis temperature. Solid state MAS NMR confirms the presence or absence of mixed bonding and further shows that, without mixed bonding, terminal hydroxyls are bound to some of the Si-O tetrahedra. This study indicates that mixed bonding, along with additional factors, such as the presence of terminal hydroxyl groups, contributes to the thermodynamic stability of SiOC PDCs.
| Typ des Eintrags: | Artikel |
|---|---|
| Erschienen: | 2021 |
| Autor(en): | Sugie, Casey ; Navrotsky, Alexandra ; Lauterbach, Stefan ; Kleebe, Hans-Joachim ; Mera, Gabriela |
| Art des Eintrags: | Bibliographie |
| Titel: | Structure and Thermodynamics of Silicon Oxycarbide Polymer-Derived Ceramics with and without Mixed-Bonding |
| Sprache: | Englisch |
| Publikationsjahr: | 22 Juli 2021 |
| Verlag: | MDPI |
| Titel der Zeitschrift, Zeitung oder Schriftenreihe: | Materials |
| Jahrgang/Volume einer Zeitschrift: | 14 |
| (Heft-)Nummer: | 15 |
| DOI: | 10.3390/ma14154075 |
| URL / URN: | https://www.mdpi.com/1996-1944/14/15/4075 |
| Kurzbeschreibung (Abstract): | Silicon oxycarbides synthesized through a conventional polymeric route show characteristic nanodomains that consist of sp(2) hybridized carbon, tetrahedrally coordinated SiO4, and tetrahedrally coordinated silicon with carbon substitution for oxygen, called "mixed bonds." Here we synthesize two preceramic polymers possessing both phenyl substituents as unique organic groups. In one precursor, the phenyl group is directly bonded to silicon, resulting in a SiOC polymer-derived ceramic (PDC) with mixed bonding. In the other precursor, the phenyl group is bonded to the silicon through Si-O-C bridges, which results in a SiOC PDC without mixed bonding. Radial breathing-like mode bands in the Raman spectra reveal that SiOC PDCs contain carbon nanoscrolls with spiral-like rolled-up geometry and open edges at the ends of their structure. Calorimetric measurements of the heat of dissolution in a molten salt solvent show that the SiOC PDCs with mixed bonding have negative enthalpies of formation with respect to crystalline components (silicon carbide, cristobalite, and graphite) and are more thermodynamically stable than those without. The heats of formation from crystalline SiO2, SiC, and C of SiOC PDCs without mixed bonding are close to zero and depend on the pyrolysis temperature. Solid state MAS NMR confirms the presence or absence of mixed bonding and further shows that, without mixed bonding, terminal hydroxyls are bound to some of the Si-O tetrahedra. This study indicates that mixed bonding, along with additional factors, such as the presence of terminal hydroxyl groups, contributes to the thermodynamic stability of SiOC PDCs. |
| Freie Schlagworte: | Silicon oxycarbide, polymer-derived ceramics, nanodomain structure, carbon nanorolls, polysiloxanes, energetics, nuclear-magnetic-resonance, free carbon phase, hydroxyl-groups, SIOC glasses, energetics, SI-29, surface, C-13, spectroscopy, calorimetry |
| Fachbereich(e)/-gebiet(e): | 11 Fachbereich Material- und Geowissenschaften 11 Fachbereich Material- und Geowissenschaften > Geowissenschaften 11 Fachbereich Material- und Geowissenschaften > Geowissenschaften > Fachgebiet Geomaterialwissenschaft 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft > Fachgebiet Disperse Feststoffe |
| TU-Projekte: | DFG|IO83/2-1|Neuartige 0D-Nano |
| Hinterlegungsdatum: | 13 Aug 2021 05:52 |
| Letzte Änderung: | 13 Aug 2021 05:52 |
| PPN: | |
| Projekte: | National Science Foundation (NSF) NSF - Directorate for Biological Sciences (BIO), Grant Number1743701, German Research Foundation (DFG), Grant Number IO 83/2-1, MDPI Materials |
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