Journal
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
Volume 103, Issue 2, Pages 1436-1445Publisher
WILEY
DOI: 10.1111/jace.16817
Keywords
ceramic nanocomposites; hafnon; polymer-derived ceramics; single-source precursors
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Funding
- Sino-German (CSC-DAAD) Postdoc Scholarship Program [57343410]
- National Natural Science Foundation of China [51872246]
- State Key Laboratory of Solidification Processing in Northwestern Polytechnical University (NPU) [SKLP201819]
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SiOC/HfO2-based ceramic nanocomposites with in situ formed HfO2 nanoparticles were prepared via a single-source precursor (SSP) approach starting from a polymethylsilsesquioxane (PMS) modified by Hf- and Ti-alkoxides. By varying the alkyl-group of the employed Hf-alkoxides, SiOC/HfO2-based ceramic nanocomposites with different HfO2 polymorphs formed via thermal decomposition of the SSP under the same heat-treatment conditions. Using PMS chemically modified by Hf((OBu)-Bu-n)(4), tetragonal HfO2 phase was formed after the synthesis at 1100 degrees C in Ar, whereas both, tetragonal and monoclinic HfO2 nanocrystals, were analyzed when replacing Hf((OBu)-Bu-n)(4) by Hf((OPr)-Pr-i)(4). After oxidation of the synthesized nanocomposites in air at 1500 degrees C, a facile formation of oxidation-resistant HfSiO4 (hafnon) phase occurred by the reaction of HfO2 nanocrystals with silica present in the SiOC nanocomposite matrix derived from Hf((OPr)-Pr-i)(4)-modified SSPs. Moreover the amount of hafnon is dramatically increased by the additional modification of the polysiloxane with Ti-alkoxides. In contrast, ceramic nanocomposites derived from Hf((OBu)-Bu-n)(4)-modified SSPs, almost no HfSiO4 is detected after oxidation at 1500 degrees C even though in the case of Ti-alkoxide-modified single-source precursor.
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