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3D-carbon fiber felts reinforced ceramic-based composites are considered as valuable structural materials due to their excellent high-temperature mechanical performance, low density and low thermal conductivity. In order to enhance the mechanical properties of the carbon fiber reinforced silicon oxycarbide (SiOC) ceramics, in-situ growth of SiCnws on the surface of carbon fiber via a simple precursor impregnation and pyrolysis method was proposed. As a result, nanoscale SiC nanowires and microscale carbon fiber felts reinforced SiOC ceramics were successfully fabricated. The results showed that the compressive strength of the composite increased by 369% and 173% after two PIP process in x/y and z directions, respectively. The enhanced compressive strength could be ascribed to the brittle fracture of SiCnws and CFs, and crack deflection. [ABSTRACT FROM AUTHOR]

Novel hybrid thermal protection material (TPM), consisting of TaSi 2 -based coating on carbon-bonded fiber (CBCF) composites and mullite fiber insulation tiles, is investigated using a plasma wind tunnel. Mullite fiber insulation tile is ceramically bonded to coated-CBCF composites. Results show that surface temperatures range from 400 °C°C to 1200 °C°C at low heat flux and dynamic pressure. However, at high heat flux and dynamic pressure, the surface temperature rapidly reaches 1400 °C°C, and the damage to the TaSi 2 -based coating is also observed. The cold-wall temperature of the hybrid structure remains at room temperature during ablation. In addition, TPM is invalid because of the consumption of the TaSi 2 -based coating. [ABSTRACT FROM AUTHOR]

This paper presents a double-layered coating system consisting of MoSi 2 ceramic reinforced with SiC whiskers and a MoSi 2 -TaSi 2 ceramic coating reinforced with SiC whiskers. This system improves oxidation resistance of carbon-bonded carbon fiber (CBCF) composites. Double-layer coating was about 160 µm in thickness and no interfaces or cracks between the layer and matrix were observed. Isothermal oxidation tests revealed that as-prepared coating presented excellent oxidation resistance, which could protect CBCF composites at 1500 °C for 160 min with 0.02% weight loss, whereas weight loss of single MoSi 2 ceramic coating reinforced with SiC whiskers reached 0.08%. High-temperature resistance barrier of the glassy phase and Ta 2 O 5 had a positive effect on improving the oxidation resistance of double-layer coating. [ABSTRACT FROM AUTHOR]

Herein, the SiC nanowires were successfully fabricated via chemical vapor infiltration (CVI) into carbon fiber felts (CFs) and then the SiOC/SiCnws/CFs composites were synthesized by precursor infiltration and pyrolysis (PIP) processes. Results indicated that the lightweight composites possessed enhanced mechanical performance, low thermal conductivity, and excellent electromagnetic wave absorption properties. Detailedly, the compressive strength reached to 22.0 MPa and 9.6 MPa after two PIP processes cycles in z and x/y directions, respectively. Meanwhile, the composites exhibited tailored electromagnetic wave absorption performance with the effective absorption bandwidth of 3.06 GHz, and the minimum reflection loss (RL min) was -48.2 dB with a thickness of 3.6 mm. The present work has a guidance to prepare and design multifunction properties for application in harsh environment. [ABSTRACT FROM AUTHOR]