Peculiarities of the Synthesis of High-Temperature TaSi2–SiC Ceramics Reinforced in situ by Discrete Silicon Carbide Nanofibers

Resumo

The possibility of increasing the mechanical properties of the ceramic material of the TaSi₂–SiC system by reinforcing it with silicon carbide nanofibers forming in situ in the combustion wave of the SHS system is investigated. To fabricate nanofibers, as well as to increase the exothermicity of reaction mixtures, an energetic polytetrafluoroethylene (PTFE) additive C₂F₄ was applied. The 70%TaSi₂ + 30%SiC ceramic, in which silicon carbide is situated in two types of morphology—in the form of rounded grains and discrete nanofibers—was fabricated with the help of self-propagating high-temperature synthesis when using the mechanical activation of initial reaction mixtures. Reinforced ceramic samples sintered using hot pressing have a relative density up to 98%, hardness of 19.0–19.2 GPa, and crack resistance of 7.5–7.8 MPa m^1/2 (which noticeably exceeds the crack resistance of the ceramics of the close composition formed without the PTFE additive).