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, 2021, 14 (15)
doi: 10.26083/tuprints-00019459
Artikel, Zweitveröffentlichung, Verlagsversion
Kurzbeschreibung (Abstract)
Silicon oxycarbides synthesized through a conventional polymeric route show characteristic nanodomains that consist of sp² 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: | Zweitveröffentlichung |
| Titel: | Structure and Thermodynamics of Silicon Oxycarbide Polymer-Derived Ceramics with and without Mixed-Bonding |
| Sprache: | Englisch |
| Publikationsjahr: | 2021 |
| Publikationsdatum der Erstveröffentlichung: | 2021 |
| Verlag: | MDPI |
| Titel der Zeitschrift, Zeitung oder Schriftenreihe: | Materials |
| Jahrgang/Volume einer Zeitschrift: | 14 |
| (Heft-)Nummer: | 15 |
| Kollation: | 23 Seiten |
| DOI: | 10.26083/tuprints-00019459 |
| URL / URN: | https://tuprints.ulb.tu-darmstadt.de/19459 |
| Zugehörige Links: | |
| Herkunft: | Zweitveröffentlichung aus gefördertem Golden Open Access |
| Kurzbeschreibung (Abstract): | Silicon oxycarbides synthesized through a conventional polymeric route show characteristic nanodomains that consist of sp² 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. |
| Status: | Verlagsversion |
| URN: | urn:nbn:de:tuda-tuprints-194593 |
| Zusätzliche Informationen: | Keywords: silicon oxycarbide; polymer-derived ceramics; nanodomain structure; carbon nanorolls; polysiloxanes; energetics |
| Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 500 Naturwissenschaften und Mathematik > 540 Chemie 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften 600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften und Maschinenbau |
| Fachbereich(e)/-gebiet(e): | 11 Fachbereich Material- und Geowissenschaften 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft > Fachgebiet Disperse Feststoffe |
| Hinterlegungsdatum: | 06 Sep 2021 12:19 |
| Letzte Änderung: | 13 Sep 2021 06:40 |
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