Insight into the evolution mechanism and properties of SiC modified (Ti, Zr, Hf)C multi-phase ceramics synthesized via the sol-gel method

This work delves into the fascinating transformation from organic precursors to dense SiC-modified (Ti, Zr, Hf)C solid solution ceramics. Nanocrystalline powder was crafted through an innovative sol-gel process coupled with carbothermal reduction, followed by spark plasma sintering (SPS) to obtain the multi-phase ceramics. The results indicate that the addition of silicone alkoxide is required for forming a robust multi-phase gel network, which facilitates the formation of oxide intermediates (e.g., ZrSiO₄, HfSiO₄), accelerates phase transformation, and inhibits grain from coarsening by encapsulating Ti/Zr/Hf compounds while reinforcing grain boundaries. After pyrolysis at 1400 °C, the precursors gradually evolved into a highly crystalline, medium-entropy solid solution. The optimal sintered composite achieves a relative density of 97.8 % and an open porosity of 0.4 %. The mechanical properties were improved by induced lattice distortion and effect of fine-grained strengthening with the incorporation of SiC. Nanoindentation tests reveal that the hardness and elastic modulus of the (Ti, Zr, Hf)C-SiC composite reach 22.39 GPa and 342.78 GPa, respectively.