Synthesis of Fine-Grained Polycarbosilane-Derived TiSiC with High-Phase-Fraction and Investigation of their Microwave Absorption Properties.

TiSiC (Titanium Silicon Carbide) represents a MAX phase that uniquely combines the merits of metals and ceramics. However, synthesis of fine-grained TiSiC especially through the polymer-derived ceramic (PDC) route remains a challenge. This study synthesizes fine-grained, high-phase-fraction TiSiC using polycarbosilane (PCS) and nanosized Ti, Al, and Si powders as raw materials. Results reveal that the addition of 15 wt.% Al significantly enhance the formation of TiSiC by promoting mass diffusion and reducing oxide impurities, resulting in a maximum TiSiC content of 73.5 wt.%, compared to 27.7 wt.% from the sole addition of nanosized Ti powders. Further incorporation of 15 wt.% Si facilitates near-complete conversion of residual TiC into TiSiC due to the promotion of TiSi formation and inhibition of excess TiC formation, yielding a high-phase-fraction TiSiC phase (83.4 wt.%) with an average grain size of ≈473 nm. The synthesized TiSiC phase can be reserved up to 1600 °C and superior electromagnetic wave (EMW) absorption performance, with a minimum reflection loss (RL) of -40.21 dB at 17.20 GHz and an effective absorption bandwidth (EAB) of 1.41 GHz for the Ti-15Al-PCS sample. The enhanced polarization loss attributed to interfacial effects, and optimized impedance matching, are responsible for this superior absorption performance.