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Phase evolution of SiOC‐based ceramic nanocomposites derived from a polymethylsiloxane modified by Hf‐ and Ti‐alkoxides

Sun, Jia and Wen, Qingbo and Li, Tao and Wiehl, Leonore and Fasel, Claudia and Feng, Yao and De Carolis, Dario M. and Yu, Zhaoju and Fu, Qian-Gang and Riedel, Ralf (2020):
Phase evolution of SiOC‐based ceramic nanocomposites derived from a polymethylsiloxane modified by Hf‐ and Ti‐alkoxides.
103, In: Journal of the American Ceramic Society, 2019 (2), pp. 1436-1445. Wiley, ISSN 0002-7820, e-ISSN 1551-2916,
DOI: 10.1111/jace.16817,
[Article]

Abstract

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(OnBu)4, tetragonal HfO2 phase was formed after the synthesis at 1100°C in Ar, whereas both, tetragonal and monoclinic HfO2 nanocrystals, were analyzed when replacing Hf(OnBu)4 by Hf(OiPr)4. After oxidation of the synthesized nanocomposites in air at 1500°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(OiPr)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(OnBu)4‐modified SSPs, almost no HfSiO4 is detected after oxidation at 1500°C even though in the case of Ti‐alkoxide‐modified single‐source precursor.

Item Type: Article
Erschienen: 2020
Creators: Sun, Jia and Wen, Qingbo and Li, Tao and Wiehl, Leonore and Fasel, Claudia and Feng, Yao and De Carolis, Dario M. and Yu, Zhaoju and Fu, Qian-Gang and Riedel, Ralf
Title: Phase evolution of SiOC‐based ceramic nanocomposites derived from a polymethylsiloxane modified by Hf‐ and Ti‐alkoxides
Language: English
Abstract:

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(OnBu)4, tetragonal HfO2 phase was formed after the synthesis at 1100°C in Ar, whereas both, tetragonal and monoclinic HfO2 nanocrystals, were analyzed when replacing Hf(OnBu)4 by Hf(OiPr)4. After oxidation of the synthesized nanocomposites in air at 1500°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(OiPr)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(OnBu)4‐modified SSPs, almost no HfSiO4 is detected after oxidation at 1500°C even though in the case of Ti‐alkoxide‐modified single‐source precursor.

Journal or Publication Title: Journal of the American Ceramic Society
Volume: 103
Journal volume: 2019
Number: 2
Publisher: Wiley
Uncontrolled Keywords: Ceramic nanocomposites; hafnon; polymer-derived ceramics; single-source precursors; microstructure evolution; stability
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Dispersive Solids
Date Deposited: 19 Dec 2019 09:00
DOI: 10.1111/jace.16817
Official URL: https://doi.org/10.1111/jace.16817
Projects: Sino‐German (CSC‐DAAD) Postdoc Scholarship Program, 2017. Grant Number: 57343410, National Natural Science Foundation of China. Grant Number: 51872246, State Key Laboratory of Solidification Processing in Northwestern Polytechnical University (NPU). Grant Number: SKLP201819
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