Single-source-precursor synthesis and phase evolution of SiC–TaC–C ceramic nanocomposites containing core–shell structured TaC@C nanoparticles

A novel single-source-precursor for SiC–TaC–C nanocomposites was successfully synthesized by the chemical reaction between a polycarbosilane(allylhydridopolycarbosilane, AHPCS) and tantalum(V) chloride(Ta Cl5), which was confirmed by Fourier transform infrared spectra(FTIR) measurement. After pyrolysis of the resultant single-source-precursors at 900 ℃, amorphous ceramic powders were obtained. The 900 ℃ ceramics were annealed at different temperatures in the range of 1200–1600 ℃ to gain SiC–TaC–C nanocomposites. The phase evolution of ceramic nanocomposites was investigated by X-ray diffraction(XRD) and transmission electron microscopy(TEM). The results indicate that the TaC starts to crystallize at lower temperature than the β-SiC. It is particularly worth pointing out that the unique core–shell structured TaC@C nanoparticles were in-situ formed and homogeneously distributed in the ceramic matrix after annealing at 1400 ℃. Even at a high temperature of 1600 ℃, the grain sizes of β-SiC and Ta C are smaller than 30 nm, fulfilling the definition of nanocomposites. The present study related to SiC–TaC–C nanocomposites paves a new road for enriching ultra-high temperature ceramic family suitable for structural/functional applications in harsh environment.