Breakthrough in VPP 3D Printing: kyanite-induced enhance thermal stability for silica ceramic cores

Complex hollow turbine blades are the core components of advanced aero-engines, heavily relying on high-precision ceramic cores as internal cooling channel templates. Traditional hot injection molding faces long fabrication cycles and struggles with intricate geometries, making VPP 3D printing a highly promising alternative. However, VPP-fabricated silica-based cores undergo massive volume shrinkage during debinding and sintering, and suffer from severe high-temperature deflection during the casting process, which drastically limits their engineering reliability and yield.

Recently, a team of material scientists led by Anran Guo from Tianjin University reported a breakthrough in fabricating high-performance silica-based ceramic cores with superior dimensional and thermal stability. This work thoroughly elucidates the regulatory mechanism of kyanite-induced expansion compensation and introduces a multi-dimensional evaluation system to optimize the 3D printing and sintering processes.

The team published their work in the Journal of Advanced Ceramics on May 6, 2026.

"To overcome the dimensional instability, we introduced kyanite into the silica-based ceramic slurry for VPP 3D printing," said Anran Guo, corresponding author and researcher at the School of Materials Science and Engineering, Tianjin University. "Instead of directly adding mullite, we utilized the unique thermal properties of kyanite. At high temperatures, kyanite decomposes to generate columnar mullite crystals and silica, accompanied by a significant volume expansion of 16% to 18%. This expansion perfectly counteracts the densification shrinkage of the silica matrix."

To systematically resolve the inevitable trade-offs between shrinkage, porosity, and mechanical strength, the researchers constructed a Ceramic Cores Quality Index (CQI) evaluation model. "Relying on a single metric is insufficient for complex casting environments," noted Guo. "By employing the CQI model, we determined that the holistic optimal performance is achieved with 15 wt.% kyanite and a sintering temperature of 1225°C."

The experimental results validated the clear superiority of this approach. Under the optimized conditions, the decomposition-generated columnar mullite acted as a robust skeleton, strongly inhibiting the liquid-phase viscous flow of the amorphous silica. Consequently, the sintering shrinkage and casting shrinkage plummeted to 3.06% and 0.86%, respectively. Furthermore, the high-temperature deflection was suppressed to a remarkable 0.82 mm, while the high-temperature flexural strength reached 27.05 MPa, ensuring exceptional structural integrity during the extreme casting process.

This kyanite-added VPP 3D printing technology successfully balances high-precision forming with high-temperature stability, holding immense potential for the rapid manufacturing of next-generation turbine blades.

Other contributors to this research include Boran Wang, Zhongyan Wang, Xin Li, Yu Chen, Rui Ge, Yongkang Yang, and Jiachen Liu, representing Tianjin University, the Beijing Institute of Aeronautical Materials, and the Huazhong University of Science and Technology.

About Author

Anran Guo is an associate professor at the School of Materials Science and Engineering, Tianjin University, China. His main research interests focus on the structural design, forming process and engineering application of porous oxide ceramics (including silica, alumina, mullite, zirconia, etc.). He has published more than 30 academic papers, over 30 of which were published in peer-reviewed journals including Journal of Advanced Ceramics, Journal of the American Ceramic Society, and Journal of the European Ceramic Society as the first or corresponding author.

Funding

This work was supported by the National Natural Science Foundation of China (No. 52172072).

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