POLYMER-DERIVED SILICON OXYCARBIDE/HAFNIA CERAMIC NANOCOMPOSITES. PT.1. PHASE AND MICROSTRUCTURE EVOLUTION DURING THE CERAMISATION PROCESS

Polymer-derived SiOC/HfO2 nanocomposites were prepared via a chemical modification of a commercially available polysilsesquioxane by hafnium tetra (n-butoxide). The ceramisation process of the starting materials was investigated using thermal analysis, in-situ FTIR and mass spectrometry. Furthermore...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 2010-01, Vol.93 (6), p.1774-1782
Main Authors: Ionescu, E, Papendorf, B, Kleebe, H-J, Poli, F, Muller, K, Riedel, R
Format: Article
Language:English
Subjects:
Ceramics
Crystallization
Evolution
Hafnia
Hafnium
Hafnium oxide
Nanocomposites
Nanostructure
Silicon dioxide
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Summary:Polymer-derived SiOC/HfO2 nanocomposites were prepared via a chemical modification of a commercially available polysilsesquioxane by hafnium tetra (n-butoxide). The ceramisation process of the starting materials was investigated using thermal analysis, in-situ FTIR and mass spectrometry. Furthermore, solid-state NMR, elemental analysis, powder XRD, and electron microscopy investigations were performed on ceramic materials pyrolysed at different temperatures ranging from 800 to 1300 C, to obtain information about the structural changes and phase evolution. The hafnium alkoxide-modified precursor converted into an amorphous single-phase SixHfyOzCw ceramic at temperatures up to 800 C. By increasing the temperature to 1000 C, amorphous hafnia began to precipitate throughout the silicon oxycarbide matrix; thus, monodisperse hafnia particles with a diameter of < 5 nm were present in the ceramic, indicating a homogeneous nucleation of HfO2. At temperatures ranging from 1100 to 1300 C, crystallisation of the hafnia nanoprecipitates and phase separation of the SiOC matrix occurred. The chemical modification of the preceramic precursor with hafnium alkoxide can be considered as a promising method for the preparation of SiOC/HfO2 nanocomposites with well-dispersed hafnia nanoparticles.
ISSN:0002-7820