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Polymer‐Derived Silicon Oxycarbide/Hafnia Ceramic Nanocomposites. Part I: Phase and Microstructure Evolution During the Ceramization Process
Author(s) -
Ionescu Emanuel,
Papendorf Benjamin,
Kleebe HansJoachim,
Poli Fabrizia,
Müller Klaus,
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.1551-2916.2010.03765.x
Subject(s) - hafnia , materials science , amorphous solid , ceramic , chemical engineering , nanocomposite , crystallization , composite material , cubic zirconia , crystallography , chemistry , engineering
Polymer‐derived SiOC/HfO 2 ceramic nanocomposites were prepared via chemical modification of a commercially available polysilsesquioxane by hafnium tetra ( n ‐butoxide). The ceramization process of the starting materials was investigated using thermal analysis and in situ Fourier‐transformed infrared spectroscopy and mass spectrometry. Furthermore, solid‐state NMR, elemental analysis, powder X‐ray diffraction, and electron microscopy investigations were performed on ceramic materials pyrolyzed at different temperatures ranging from 800° to 1300°C, in order to obtain information about the structural changes and phase evolution thereof. The hafnium alkoxide‐modified precursor was shown to convert into an amorphous single‐phase Si x Hf y O z C w ceramic at temperatures up to 800°C. By increasing the temperature to 1000°C, amorphous hafnia begins to precipitate throughout the silicon oxycarbide matrix; thus, monodisperse hafnia particles with a diameter of <5 nm are present in the ceramic, indicating a homogeneous nucleation of HfO 2 . At temperatures ranging from 1100° to 1300°C, crystallization of the hafnia nanoprecipitates as well as phase separation of the SiOC matrix occur. The chemical modification of the preceramic precursor with hafnium alkoxide can be considered as a promising method for the preparation of SiOC/HfO 2 nanocomposites with well‐dispersed hafnia nanoparticles.