Preparation of dense SiHf(B)CN-based ceramic nanocomposites via rapid spark plasma sintering

Dense SiHf(B)CN-based ceramic nanocomposites were prepared by spark plasma sintering (SPS) using high heating rates (similar to 450 degrees C/min.) and high pressures (>= 100 MPa). The obtained nanocomposites were investigated by X-ray diffraction, Raman spectroscopy and electron microscopy concerning their phase evolution and microstructure. The hardness and the elastic modulus of dense SiHfCN were found to be 26.8 and 367 GPa, respectively. Whereas the SiHfBCN samples exhibited a hardness of 24.6 GPa and an elastic modulus of 284 GPa. The investigation of the oxidation of the prepared dense ceramic nanocomposites at high temperature revealed that the parabolic oxidation rates of SiHfCN were comparable to those of ultra-high temperature ceramics (UHTCs, e.g. HfC-20 vol% SiC); whereas the parabolic oxidation rates of SiHfBCN were several orders of magnitude lower than those. The results obtained within this study indicate the feasibility of SPS for rapid preparation of dense though nano-scaled Hf-containing ceramic nanocomposites that are promising candidates for high-temperature applications in harsh environments. (C) 2017 Elsevier Ltd. All rights reserved.