Ceramization of coordinated Zr4+ and Hf4+ in polysiloxane conferring silicone/phenolic hybrid resin with excellent thermal protection.

Silicon/phenolic hybrid resins are one of the most commonly used materials for thermal protection. However, the weak ability of SiO 2 generated by silicone during ablation to resist the impact of high-speed hot gas flow hinders further improvement of the performance. Therefore, in this work, the ultrahigh-temperature ceramic elements Zr4+ and Hf4+ were integrated into hyperbranched polysiloxanes in the form of coordination bond and then introduced into phenolic resin (PR), obtaining hybrid resin with excellent ablative resistance. During ablation, Zr4+ and Hf4+ will first undergo ceramization, producing ZrO 2 and HfO 2. Subsequently, they will undergo a solid solution sintering reaction to produce complex-phase ceramic particles (Zr x Hf 1-x)O 2 , which are embedded in the SiO 2 liquid film and provide excellent pinning effect. This gives the hybrid resin excellent ablation resistance, whose linear ablation rate can be as low as 0.038 mm/s, a 58 % decrease compared to pure PR. This work not only provides a new pathway for ceramization through metal ion coordination bonding, but also provides a new way to prepare high-performance TPS materials. [Display omitted] • Zr4+ and Hf4+ were successfully introduced into hyperbranched organosilica through the lone electron pair provided by C=O. • Silicon/phenolic hybrid resin with a unique nano-bicontinuous phase structure was produced. • The coordinated Zr4+ and Hf4+ can undergo in-situ ceramization and solid solution sintering reaction to produce (Zr x Hf 1-x)O 2. • (Zr x Hf 1-x)O 2 can perform an excellent pinning effect and confer excellent ablation resistance to the hybrid resin. [ABSTRACT FROM AUTHOR]