Li, Ya-Li ; Fan, Hua ; Su, Dong ; Fasel, Claudia ; Riedel, Ralf (2009)
Synthesis, Structures, and Properties of Bulk Si(O)C Ceramics from Polycarbosilane.
In: Journal of the American Ceramic Society, 92 (10)
doi: 10.1111/j.1551-2916.2009.03184.x
Artikel, Bibliographie
Kurzbeschreibung (Abstract)
Bulk Si(O)C ceramics are fabricated from polycarbosilane (PCS) by bulk pyrolysis along the route of cross linking, warm-pressing, and pyrolysis. The PCS was thermally oxidized for cross linking at various temperatures as a critical step toward the bulk transformation of PCS into bulk Si(O)C ceramics. The degree of cross linking of PSC affects the densities and bonding qualities of the warm-pressed powder compacts and, hence, the resultant ceramics. Under optimized processing conditions, crack-free bulk Si(O)C ceramics are obtained with a bulk density attaining 2.2 g/cm3. Despite the existence of a considerable amount of oxygen in the ceramics (16.08 wt%), resulting from the thermal oxidation processing, the ceramics show the characteristics of structures and properties of SiC-based ceramics. 29Si-solid state nuclear magnetic resonance spectra (NMR) reveal that the as-pyrolyzed X-ray amorphous Si(O)C phase consists mainly of SiC4 coordination units in the ceramic network, with the remainder being silicon-coordinated carbon and oxygen. Microhardness tests show that the as-pyrolyzed amorphous Si(O)C ceramics have a high hardness, attaining 24.91 GPa at a load of 2 N, and 19.82 GPa at a load of 10 N. Upon annealing at 1300°C in argon, the amorphous ceramics crystallized into nanophase β-SiC ceramics, and the ceramics kept the bulk nature of the amorphous ceramics with an increased density. The 29Si-solid state NMR spectrum indicates that the nanophase β-SiC ceramics consist of SiC4 units together with some mixed coordination units, namely SiO2C2 and SiOC3. The hardness of the crystallized nanophase Si(O)C ceramics attains 23.20 GPa at a load of 10 N. The present study demonstrates the possibility of fabricating bulk Si(O)C ceramics via the polymer-processing route, resulting in ceramics with promising structural and mechanical properties.
| Typ des Eintrags: | Artikel |
|---|---|
| Erschienen: | 2009 |
| Autor(en): | Li, Ya-Li ; Fan, Hua ; Su, Dong ; Fasel, Claudia ; Riedel, Ralf |
| Art des Eintrags: | Bibliographie |
| Titel: | Synthesis, Structures, and Properties of Bulk Si(O)C Ceramics from Polycarbosilane |
| Sprache: | Englisch |
| Publikationsjahr: | Oktober 2009 |
| Verlag: | Wiley |
| Titel der Zeitschrift, Zeitung oder Schriftenreihe: | Journal of the American Ceramic Society |
| Jahrgang/Volume einer Zeitschrift: | 92 |
| (Heft-)Nummer: | 10 |
| DOI: | 10.1111/j.1551-2916.2009.03184.x |
| Kurzbeschreibung (Abstract): | Bulk Si(O)C ceramics are fabricated from polycarbosilane (PCS) by bulk pyrolysis along the route of cross linking, warm-pressing, and pyrolysis. The PCS was thermally oxidized for cross linking at various temperatures as a critical step toward the bulk transformation of PCS into bulk Si(O)C ceramics. The degree of cross linking of PSC affects the densities and bonding qualities of the warm-pressed powder compacts and, hence, the resultant ceramics. Under optimized processing conditions, crack-free bulk Si(O)C ceramics are obtained with a bulk density attaining 2.2 g/cm3. Despite the existence of a considerable amount of oxygen in the ceramics (16.08 wt%), resulting from the thermal oxidation processing, the ceramics show the characteristics of structures and properties of SiC-based ceramics. 29Si-solid state nuclear magnetic resonance spectra (NMR) reveal that the as-pyrolyzed X-ray amorphous Si(O)C phase consists mainly of SiC4 coordination units in the ceramic network, with the remainder being silicon-coordinated carbon and oxygen. Microhardness tests show that the as-pyrolyzed amorphous Si(O)C ceramics have a high hardness, attaining 24.91 GPa at a load of 2 N, and 19.82 GPa at a load of 10 N. Upon annealing at 1300°C in argon, the amorphous ceramics crystallized into nanophase β-SiC ceramics, and the ceramics kept the bulk nature of the amorphous ceramics with an increased density. The 29Si-solid state NMR spectrum indicates that the nanophase β-SiC ceramics consist of SiC4 units together with some mixed coordination units, namely SiO2C2 and SiOC3. The hardness of the crystallized nanophase Si(O)C ceramics attains 23.20 GPa at a load of 10 N. The present study demonstrates the possibility of fabricating bulk Si(O)C ceramics via the polymer-processing route, resulting in ceramics with promising structural and mechanical properties. |
| Fachbereich(e)/-gebiet(e): | 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft > Fachgebiet Disperse Feststoffe 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft 11 Fachbereich Material- und Geowissenschaften |
| Hinterlegungsdatum: | 13 Apr 2012 08:54 |
| Letzte Änderung: | 05 Mär 2013 10:00 |
| PPN: | |
| Sponsoren: | Y. Li thanks the Alexander von Humboldt Foundation (AvH) for providing research fellowships., S. D. thanks Visiting Scholarship from Defense University of Science and Technology, China. |
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