In this work, low-softening-temperature and low-modulus SiO₂ was introduced as an embedded interface between SiC nanowires (SiCnws) and a Ba_xSr_1−xAl₂Si₂O₈ ceramic matrix to enhance strength and toughness of the ceramic. During the sintering process, molten SiO₂ enhances the flowability of the ceramic powders and modifies the dispersion of SiCnws. The strengthening effect of SiCnws was fully realized, and the flexural strength of the optimized ceramics reached 193±16 MPa, which represents an increase of 52.6%. After the formation of the embedded SiO₂ interface with a low modulus, cracks can deflect along the SiCnws surface, which is consistent with the criterion of He and Hutchinson. This can effectively extend the crack propagation path, and the fracture toughness ( $K_{\mathrm{I}\mathrm{C}}$) is thus improved by 94.0%, reaching 3.1±0.5 MPa·m^1/2.

Oxidation behaviors of carbon fiber reinforced SiC matrix composites (C/SiC) are one of the most noteworthy properties. For C/SiC, the oxidation behavior was controlled by matrix microcracks caused by the mismatch of coefficients of thermal expansion (CTEs) and elastic modulus between carbon fiber and SiC matrix. In order to improve the oxidation resistance, multilayer SiC-Si₃N₄ matrices were fabricated by chemical vapor infiltration (CVI) to alleviate the above two kinds of mismatch and change the local stress distribution. For the oxidation of C/SiC with multilayer matrices, matrix microcracks would be deflected at the transition layer between different layers of multilayer SiC-Si₃N₄ matrix to lengthen the oxygen diffusion channels, thereby improving the oxidation resistance of C/SiC, especially at 800 and 1000 ℃. The strength retention ratio was increased from 61.9% (C/SiC-SiC/SiC) to 75.7% (C/SiC-Si₃N₄/SiC/SiC) and 67.8% (C/SiC-SiC/Si₃N₄/SiC) after oxidation at 800 ℃ for 10 h.

In this work, bulk Zr₃Al₃C₅-based ceramics were synthesized by the infiltration of Al–Si melt into zirconium carbide (ZrC) perform. The phase composition, microstructure, and mechanical properties of as-fabricated ceramics were studied. The results demonstrate that Si is more effective to reduce the twin boundary energy of ZrC than Al, and thus promotes the decrease of formation temperature of Zr₃Al₃C₅. With the infiltration temperatures increasing from 1200 to 1500 ℃, the Zr₃Al₃C₅ content increases from 10 to 49 vol%, which is contributed to the increase of flexural strength from 62±9 to 222±10 MPa, and fracture toughness (K_IC) from 2.8±0.2 to 4.1±0.3 MPa·m^1/2. The decrease of mechanical properties for the samples fabricated at 1600 ℃ is ascribed to the abnormal growth of Zr₃Al₃C₅ grains.

The effect of pyrolytic carbon (PyC) thickness on the tensile property of mini T800 carbon fiber reinforced SiC matrix composites (C/SiC) was studied. PyC interphase was prepared by chemical vapor infiltration (CVI) process using C₃H₆-Ar as gas source, the PyC thickness was adjusted from 0 to 400 nm, and then the SiC matrix was prepared by CVI process using methyltrichlorosilane (MTS)-H₂-Ar as precursor and gas source. The results showed that the tensile strength of mini T800-C/SiC increased first and then decreased with the increase of the PyC thickness. When the thickness of PyC was 100 nm, the average strength reached the maximum value of 393 ± 70 MPa. The Weibull modulus increased from 2.0 to 8.06 with the increase of PyC thickness, and the larger the Weibull modulus, the smaller the dispersion, which indicated that the regulation of PyC thickness was conducive to improve tensile properties.