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Single-source-precursor synthesis of dense SiC/HfCxN1−x-based ultrahigh-temperature ceramic nanocomposites

Wen, Qingbo and Xu, Yeping and Xu, Binbin and Fasel, Claudia and Guillon, Olivier and Buntkowsky, Gerd and Yu, Zhaoju and Riedel, Ralf and Ionescu, Emanuel (2014):
Single-source-precursor synthesis of dense SiC/HfCxN1−x-based ultrahigh-temperature ceramic nanocomposites.
6, In: Nanoscale, (22), Royal Society of Chemistry, pp. 13678-13689, ISSN 2040-3364, DOI: 10.1039/C4NR03376K,
[Online-Edition: https://doi.org/10.1039/C4NR03376K],
[Article]

Abstract

A novel single-source precursor was synthesized by the reaction of an allyl hydrido polycarbosilane (SMP10) and tetrakis(dimethylamido)hafnium(IV) (TDMAH) for the purpose of preparing dense monolithic SiC/HfCxN1−x-based ultrahigh temperature ceramic nanocomposites. The materials obtained at different stages of the synthesis process were characterized via Fourier transform infrared (FT-IR) as well as nuclear magnetic resonance (NMR) spectroscopy. The polymer-to-ceramic transformation was investigated by means of MAS NMR and FT-IR spectroscopy as well as thermogravimetric analysis (TGA) coupled with in situ mass spectrometry. Moreover, the microstructural evolution of the synthesized SiHfCN-based ceramics annealed at different temperatures ranging from 1300 °C to 1800 °C was characterized by elemental analysis, X-ray diffraction, Raman spectroscopy and transmission electron microscopy (TEM). Based on its high temperature behavior, the amorphous SiHfCN-based ceramic powder was used to prepare monolithic SiC/HfCxN1−x-based nanocomposites using the spark plasma sintering (SPS) technique. The results showed that dense monolithic SiC/HfCxN1−x-based nanocomposites with low open porosity (0.74 vol%) can be prepared successfully from single-source precursors. The average grain size of both HfC0.83N0.17 and SiC phases was found to be less than 100 nm after SPS processing owing to a unique microstructure: HfC0.83N0.17 grains were embedded homogeneously in a β-SiC matrix and encapsulated by in situ formed carbon layers which acted as a diffusion barrier to suppress grain growth. The segregated Hf-carbonitride grains significantly influenced the electrical conductivity of the SPS processed monolithic samples. While Hf-free polymer-derived SiC showed an electrical conductivity of ca. 1.8 S cm−1, the electrical conductivity of the Hf-containing material was analyzed to be ca. 136.2 S cm−1.

Item Type: Article
Erschienen: 2014
Creators: Wen, Qingbo and Xu, Yeping and Xu, Binbin and Fasel, Claudia and Guillon, Olivier and Buntkowsky, Gerd and Yu, Zhaoju and Riedel, Ralf and Ionescu, Emanuel
Title: Single-source-precursor synthesis of dense SiC/HfCxN1−x-based ultrahigh-temperature ceramic nanocomposites
Language: English
Abstract:

A novel single-source precursor was synthesized by the reaction of an allyl hydrido polycarbosilane (SMP10) and tetrakis(dimethylamido)hafnium(IV) (TDMAH) for the purpose of preparing dense monolithic SiC/HfCxN1−x-based ultrahigh temperature ceramic nanocomposites. The materials obtained at different stages of the synthesis process were characterized via Fourier transform infrared (FT-IR) as well as nuclear magnetic resonance (NMR) spectroscopy. The polymer-to-ceramic transformation was investigated by means of MAS NMR and FT-IR spectroscopy as well as thermogravimetric analysis (TGA) coupled with in situ mass spectrometry. Moreover, the microstructural evolution of the synthesized SiHfCN-based ceramics annealed at different temperatures ranging from 1300 °C to 1800 °C was characterized by elemental analysis, X-ray diffraction, Raman spectroscopy and transmission electron microscopy (TEM). Based on its high temperature behavior, the amorphous SiHfCN-based ceramic powder was used to prepare monolithic SiC/HfCxN1−x-based nanocomposites using the spark plasma sintering (SPS) technique. The results showed that dense monolithic SiC/HfCxN1−x-based nanocomposites with low open porosity (0.74 vol%) can be prepared successfully from single-source precursors. The average grain size of both HfC0.83N0.17 and SiC phases was found to be less than 100 nm after SPS processing owing to a unique microstructure: HfC0.83N0.17 grains were embedded homogeneously in a β-SiC matrix and encapsulated by in situ formed carbon layers which acted as a diffusion barrier to suppress grain growth. The segregated Hf-carbonitride grains significantly influenced the electrical conductivity of the SPS processed monolithic samples. While Hf-free polymer-derived SiC showed an electrical conductivity of ca. 1.8 S cm−1, the electrical conductivity of the Hf-containing material was analyzed to be ca. 136.2 S cm−1.

Journal or Publication Title: Nanoscale
Volume: 6
Number: 22
Publisher: Royal Society of Chemistry
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
07 Department of Chemistry
07 Department of Chemistry > Fachgebiet Anorganische Chemie
07 Department of Chemistry > Physical Chemistry
Date Deposited: 17 Dec 2018 13:26
DOI: 10.1039/C4NR03376K
Official URL: https://doi.org/10.1039/C4NR03376K
Funders: Zhaoju Yu thanks the National Natural Science Foundation of China (no. 50802079) and the Scientific and Technological Innovation Platform of Fujian Province (2006L2003) for financial support., Qingbo Wen acknowledges the China Scholarship Council (CSC) for financial support (no. 201206130059).
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