Mechanisms Limiting Ti₃SiC₂ Formation During Carbothermal Reduction of Liquid Ti-Si-C-O Precursors

The traditional precursor-derived ceramic (PDC) route uses micron-sized titanium sources and silicon carbide precursors to prepare Ti₃SiC₂, which limits its application in fine-scale fields. We propose a fully liquid Ti-Si-C-O precursor, consisting of tetrabutyl titanate (TBT) and liquid polycarbosilane (LPCS), inspired by the carbothermal reduction of solid oxides to prepare Ti₃SiC₂. The fully liquid precursor can offer processing advantages that are not achievable through previous PDC processes. The pyrolysis of the TSO-1 (TBT:LPCS = 3:2) undergoes four stages: dehydration condensation (RT~200 °C), alkoxy removal (200~400 °C), inorganic conversion (400~800 °C), and carbothermal reduction (>800 °C). The products of TSO-1 pyrolyzed to 1400 °C and 1600 °C are Ti₃O₅, SiO₂ and TiC, and Ti₃O₅, Ti₂O₃, SiO₂ and TiC, respectively. Increasing the LPCS content in the system can promote the formation of TiC, but will not produce Ti₃SiC₂. This phenomenon stems from the dual constraints: thermodynamically, titanium oxides outcompete SiO₂ for carbon; kinetically, the gaseous escape of effective carbon and its microscale non-uniform distribution further impair the carbothermal reduction of SiO₂. These combined factors prevent the gas-solid reaction from establishing, rendering Ti₃SiC₂ unattainable.