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Temperature above 2000°C and additional pressure is generally required to achieve the full densification of TaxHf1−xC‐based ceramics. This work proposed a novel method to fabricate dense Ta0.2Hf0.8C ceramics at relatively low temperature. Using a small amount of Si as a sintering aid, Ta0.2Hf0.8C was densified at 1700°C by reactive hot‐pressing (RHP), with SiC formed in situ. Microstructure evolution mechanisms of the ceramics during RHP were investigated. The effect of silicon content on the densification and mechanical properties of the ceramics was revealed. It is indicated that the apparent porosity of the Ta0.2Hf0.8C–SiC ceramics was as low as 0.5%, whereas bending strength and fracture toughness of the ceramics were as high as ∼637 MPa and 6.7 MPa m1/2, respectively, when the silicon content was 8 wt.%. This work provides a new idea for the low‐temperature densification of TaxHf1−xC and other ultrahigh temperature ceramics with high performance. [ABSTRACT FROM AUTHOR]

Abstract: Short carbon fiber reinforced SiC matrix composites were fabricated by spark plasma sintering. Density and mechanical properties of the composites increased continuously at increasing sintering temperature and constant pressure. Cracks in the composite matrix resulted from high thermal residual stresses generated during the cooling process from the sintering temperature due to the thermal expansion coefficient mismatch between fiber and matrix. The properties of the composites were lower than those of monolithic SiC ceramics obtained with the same processing technique as the composites. Fibers provided noncatastrophic fracture behavior of the composites as evidenced by the stress-displacement curves and fracture surface of the composites. [Copyright &y& Elsevier]

In this work, an efficient processing route was developed to fabricate C f /(Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C-SiC composites via slurry infiltration lamination (SIL) combined with precursor infiltration and pyrolysis (PIP). The (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C powder was initially synthesized at 1900 °C. Then the 2D C f /(Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C-SiC composites were obtained via SIL and PIP at temperatures no higher than 1100 °C. The as-fabricated composites show a density of 2.52 g/cm3 and an open porosity of 15.2 vol%, with a bending strength of 255 ± 15 MPa. The 2D C f /(Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C-SiC composites also present excellent ablation resistance, with the linear and mass recession rates of 0.33 µm/s and 0.60 mg/s after ablation at 2000 °C/300 s. This work provides a route for the efficient fabrication of C f /(Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C-SiC composites, and also inspires new strategies to develop high-entropy ceramic matrix composites with high performance. [ABSTRACT FROM AUTHOR]

A unique method is adopted to fabricate high strength aligned SiC nanowire (SiCNWs) reinforced SiC porous ceramics. SiCNWs skeleton was printed through direct ink printing and SiC matrix was synthesized through chemical vapor infiltration. Unidirectional orientation of SiCNWs was realized due to shear flow through small nozzle. The skeleton structure and micron level pores in struts ensured effective SiC infiltration. Well-aligned SiCNWs were homogeneously distributed in SiC matrix without damage. The unidirectional oriented SiCNWs benefits load transfer from matrix to SiCNWs and load-bearing of SiCNWs. Therefore compressive strength reached 390 MPa with ~41.3% porosity while ~400 μm pore size. [ABSTRACT FROM AUTHOR]