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Polymer‐Derived Silicon Oxycarbide/Hafnia Ceramic Nanocomposites. Part II: Stability Toward Decomposition and Microstructure Evolution at T≫1000°C
Author(s) -
Ionescu Emanuel,
Papendorf Benjamin,
Kleebe HansJoachim,
Riedel Ralf
Publication year - 2010
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2009.03527.x
Subject(s) - materials science , nanocomposite , ceramic , microstructure , hafnia , thermal stability , annealing (glass) , ceramic matrix composite , composite material , chemical engineering , chemical stability , raman spectroscopy , polymer , silicon , cubic zirconia , metallurgy , physics , optics , engineering
This study presents first investigations on the high‐temperature stability and microstructure evolution of SiOC/HfO 2 ceramic nanocomposites. Polymer‐derived SiOC/HfO 2 ceramic nanocomposites have been prepared via chemical modification of a commercially available polysilsesquioxane by hafnium tetra ( n ‐butoxide). The modified polysilsesquioxane‐based materials were cross‐linked and subsequently pyrolyzed at 1100°C in argon atmosphere to obtain SiOC/HfO 2 ceramic nanocomposites. Annealing experiments at temperatures between 1300° and 1600°C were performed and the annealed materials were investigated with respect to chemical composition and microstructure. The ceramic nanocomposites presented here were found to exhibit a remarkably improved thermal stability up to 1600°C in comparison with hafnia‐free silicon oxycarbide. Chemical analysis, X‐ray diffraction, FTIR, and Raman spectroscopy as well as electron microscopy (SEM, TEM) studies revealed that the excellent thermal stability of the SiOC/HfO 2 nanocomposites is a consequence of the in situ formation of hafnon (HfSiO 4 ), which represents a concurrent reaction to the carbothermal decomposition of the SiOC matrix. Thus, by the annealing of SiOC/HfO 2 materials at 1600°C, novel HfSiO 4 /SiC/C ceramic nanocomposites can be generated. The results presented emphasize the potential of these materials for application at high temperatures.