Thermal protection materials are critical components in thermal protection systems (TPS) of high-speed vehicles and scramjet engines. Recently, polymer-derived ceramics (PDCs) have attracted great attention for lightweight thermal protection due to their molecular-level designability and low-temperature processability. Among the various options available, HfO 2 -SiBOC ceramics have emerged as promising candidates for TPS due to their inherent characteristics such as low density, excellent high-temperature stability, and superior ablation resistance.
Generally, carbide- and boride-based ultra-high temperature ceramics (UHTCs) have been fabricated using various methods such as powder metallurgy, reactive sintering, and spark plasma sintering. To synthesize these ceramics, metal carbides or oxides are commonly used as starting materials by solid-state methods. This requires extensive milling to disperse the various components and extremely high processing temperatures to accelerate the diffusion of atoms. However, this approach is energy-intensive and introduces impurities during the ball milling process, which compromises the phase purity and affects high-temperature performance. Additionally, the high density of these UHTCs (e.g., HfC at 12.7 g/cm 3 , ZrB 2 at 6.09 g/cm 3 ) severely limits their widespread applications in the aerospace industry. Moreover, the oxidation-induced volume change and catastrophic oxidation of borides and carbides in oxygen-containing atmospheres remain unresolved challenges.
Recently, a young material scientists Yang Lyu from Suzhou Laboratory, China reported the design, synthesis, microstructure, and ablation resistance of a novel HfO 2 -SiBOC ceramic. This work not only explains the formation mechanism of the self-protective multilayer structure and superior ablation resistance of the HfO 2 -SiBOC ceramic, but also provides a thermodynamically guided strategy to produce lightweight polymer-derived ceramics for ultra-high temperature applications.
The team published their work in Journal of Advanced Ceramics on May 20 , 202 6.
"In this report, we designed a novel HfO 2 -SiBOC ceramic guided by the fundamental thermodynamic oxidation sequence (Hf→Si→B→C) revealed by the Ellingham diagram. This design enables preferential Hf oxidation to form a stable HfO 2 barrier, while Si and B subsequently generate viscous oxides to heal defects, constructing a self-protective multilayer structure. We synthesized an amber liquid SiHfBOC precursor via a sol-gel and solvothermal method using methyltriethoxysilane and hafnium tetrachloride as raw materials. The precursor features Si-O-Si, Si-O-B main chains and Si-O-Hf side chains, achieving molecular-level incorporation of hafnium into the polymer network," said Yang Lyu, assistant researcher at Suzhou Laboratory (China), an expert whose research interests focus on the field of ultra-high temperature ceramics and polymer-derived ceramics.
"The HfO₂-SiBOC ceramic is constructed by an amorphous SiBOC matrix with nano-sized HfO₂ uniformly dispersed as the reinforcement phase. The bulk ceramic has a density of only 2.49 g/cm 3 , significantly lower than traditional UHTCs and even conventional lightweight ceramics such as SiC and Si 3 N 4 ," said Lyu.
"Due to its unique self-protective multilayer structure, the prepared HfO 2 -SiBOC ceramic has outstanding ablation resistance under 2000°C oxyacetylene flame for 300 s. The mass ablation rate is merely 4.14×10 -6 g/mm 2 ·s and the linear ablation rate is only 6.02×10 -4 mm/s, demonstrating near-nonablative behavior. This makes it a promising lightweight thermal protection material for ultra-high temperature applications," said Lyu.
However, more delicate research works are still needed to explore the long-term service stability of the HfO 2 -SiBOC ceramic as a new thermal protection material. In this regard, Lyu also put forward two major works including the high-temperature mechanical properties and the thermal shock resistance under rapid heating and cooling conditions.
Other contributors include research team members from Suzhou Laboratory.
About Author
Yang L yu is the first/corresponding author. He is an assistant researcher (postdoctoral fellow) at Suzhou Laboratory, specializing in the development and performance investigation of ultra-high temperature ceramic precursors and their composites. He currently leads the National Natural Science Foundation of China (NSFC) Youth Program (Category C) and the Jiangsu Province Youth Science Fund, and was awarded the Jiangsu Province Outstanding Postdoctoral Fellowship (Category A). He has published over 10 SCI papers in top-tier materials journals, including J. Adv. Ceram, J. Mater. Sci. Tech, and Compos. Part B .
Funding
This work is supported by the National Natural Science Foundation of China (No. 52502073, 52502072, 52502060, 52472091, 52541021, No. 52293372), Basic Research Program of Jiangsu (No. BK20250526, BK20250534), China Postdoctoral Science Foundation (No. 2025M780132), and the Funda-mental Research Funds for the Central Universities (No. HIT-XTCX-2).
DOI Link: https://doi.org/10.26599/JAC.2026.9221324
About Journal of Advanced Ceramics
Journal of Advanced Ceramics (JAC) is an international academic journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press, and exclusively available via SciOpen . JAC’s 2024 IF is 16.6, ranking in Top 1 (1/34, Q1) among all journals in “Materials Science, Ceramics” category, and its 2024 CiteScore is 25.9 (5/130) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508
Journal of Advanced Ceramics
A novel lightweight near-non-ablation HfO2–SiBOC ceramic: From SiHfBOC precursor synthesis to oxyacetylene flame testing at 2000 °C
20-May-2026