%0 Journal Article
%A Wen, Qingbo
%A Xu, Yeping
%A Xu, Binbin
%A Fasel, Claudia
%A Guillon, Olivier
%A Buntkowsky, Gerd
%A Yu, Zhaoju
%A Riedel, Ralf
%A Ionescu, Emanuel
%T Single-source-precursor synthesis of dense SiC/HfC$_{x}$N$_{1-x}$-based ultrahigh-temperature ceramic nanocomposites
%J Nanoscale
%V 6
%N 22
%@ 2040-3372
%C Cambridge
%I RSC Publ.
%M FZJ-2015-00693
%P 13678 - 13689
%D 2014
%X 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.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000344836800049
%R 10.1039/C4NR03376K
%U https://juser.fz-juelich.de/record/186620