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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]

In this study, a Cf/Ta4HfC5‐SiC ultra‐high‐temperature ceramic matrix composite exhibiting a homogeneous phase distribution was successfully fabricated via precursor infiltration and pyrolysis processing. Initially, the pyrolysis and solid solution mechanisms exhibited by the Ta4HfC5 precursor were investigated and characterized through TG‐MS and XRD analysis. The as‐fabricated Cf/Ta4HfC5‐SiC composite exhibited a density and open porosity of 2.84 g/cm3 and 10.62 vol%, respectively. It also exhibited outstanding mechanical properties, with a flexural strength of 339 ± 20 MPa and fracture toughness of 11.56 ± 0.77 MPa·m1/2. The Cf/Ta4HfC5‐SiC composite demonstrated strong ablation resistance under a heat flux of 5 MW/m2 at ~2400℃, with corresponding linear and mass recession rates of 5.33 μm/s and 6.18 mg/s, respectively. The combination of strong mechanical properties and ablation resistance provides a solid basis for the use of the Cf/Ta4HfC5‐SiC composite in a new generation of ultra‐high‐temperature materials. [ABSTRACT FROM AUTHOR]

• C f /(Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C-SiC high-entropy ceramic matrix composites were reported for the first time. • The pyrolysis and the solid-solution mechanisms of (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C precursor were systematically studied. • The as-fabricated C f /(Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C-SiC composites present excellent mechanical and anti-ablation properties. In this work, C f /(Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C-SiC high-entropy ceramic matrix composites were reported for the first time. Based on the systematic study of the pyrolysis and solid-solution mechanisms of (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C precursor by Fourier transform infrared spectroscopy, TG-MS and XRD, C f /(Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C-SiC with uniform phase and element distribution were successfully fabricated by precursor infiltration and pyrolysis. The as-fabricated composites have a density and open porosity of 2.40 g/cm3 and 13.32 vol% respectively, with outstanding bending strength (322 MPa) and fracture toughness (8.24 MPa m1/2). The C f /(Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C-SiC composites also present excellent ablation resistant property at a heat flux density of 5 MW/m2, with linear and mass recession rates of 2.89 μm/s and 2.60 mg/s respectively. The excellent combinations of mechanical and ablation resistant properties make the C f /(Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C-SiC composites a new generation of reliable ultra-high temperature materials. [ABSTRACT FROM AUTHOR]

Abstract: 3D Cf/SiBCN composites were fabricated by an efficient polymer impregnation and pyrolysis (PIP) method using liquid poly(methylvinyl)borosilazanes as precursor. Mechanical properties and microstructure evolution of the prepared 3D Cf/SiBCN composites at elevated temperatures in the range of 1500‐1700°C were investigated. As temperature increased from room temperature (371 ± 31 MPa, 31 ± 2 GPa) to 1500°C (316 ± 29 MPa, 27 ± 3 GPa), strength and elastic modulus of the composite decreased slightly, which degraded seriously as temperature further increased to 1600°C (92 ± 15 MPa, 12 ± 2 GPa) and 1700°C (84 ± 12 MPa, 11 ± 2GPa). To clarify the conversion of failure mechanisms, interfacial shear strength (IFSS) and microstructure evolution of the 3D Cf/SiBCN composites at different temperatures were investigated in detail. It reveals that the declines of the strength and changes of the IFSS of the composites are strongly related to the defects and SiC nano‐crystals formed in the composites at elevated temperatures. [ABSTRACT FROM AUTHOR]

In the present study, a novel liquid polycarbosilane (LPCS) with a ceramic yield as high as 83% was applied to develop 3D needle-punched C f /SiC composites via polymer impregnation and pyrolysis process (PIP). The cross-link and ceramization processes of LPCS were studied in detail by FT-IR and TG-DSC; a compact ceramic was obtained when LPCS was firstly cured at 120 °C before pyrolysis. It was found that the LPCS-C f /SiC composites possessed a higher density (2.13 g/cm 3 ) than that of the PCS-C f /SiC composites even though the PIP cycle for densification was obviously reduced, which means a higher densification efficiency. Logically, the LPCS-C f /SiC composites exhibited superior mechanical properties. The shorter length and rougher surfaces of pulled-out fibers indicated the LPCS-C f /SiC composites to possess a stronger bonding between matrix and PyC interphase compared with the PCS-C f /SiC composites. [ABSTRACT FROM AUTHOR]