TY  - JOUR
AU  - Wen, Qingbo
AU  - Xu, Yeping
AU  - Xu, Binbin
AU  - Fasel, Claudia
AU  - Guillon, Olivier
AU  - Buntkowsky, Gerd
AU  - Yu, Zhaoju
AU  - Riedel, Ralf
AU  - Ionescu, Emanuel
TI  - Single-source-precursor synthesis of dense SiC/HfC$_{x}$N$_{1-x}$-based ultrahigh-temperature ceramic nanocomposites
JO  - Nanoscale
VL  - 6
IS  - 22
SN  - 2040-3372
CY  - Cambridge
PB  - RSC Publ.
M1  - FZJ-2015-00693
SP  - 13678 - 13689
PY  - 2014
AB  - 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.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000344836800049
DO  - DOI:10.1039/C4NR03376K
UR  - https://juser.fz-juelich.de/record/186620
ER  -