Porous (Y 0.25 Ho 0.25 Yb 0.25 Lu 0.25 ) 2 Si 2 O 7 : A novel high‐entropy ceramic with high porosity and excellent thermal stability

• Published in: Journal of the American Ceramic Society 2024-10, Vol.107 (10), p.6921-6929
• Main Authors: Zhou, Jiaxin, Zeng, Dawei, Wu, Zhen, Sun, Luchao, Wang, Jingyang
• Format: Article
• Language: English
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.19955

With the rapid development of hypersonic vehicles, the thermal protection systems face great challenges due to the severe aerodynamic heat. As a result, conventional fiber insulation tiles would experience severe shrinkage at high temperatures (>1500°C), endangering the safety of the aircraft. To solve the problem, a high‐entropy effect was introduced to increase the high‐temperature resistance of thermal insulation materials, and highly porous (Y 0.25 Ho 0.25 Yb 0.25 Lu 0.25 ) 2 Si 2 O 7 was prepared by in situ reaction sintering process in this work. The fabricated porous samples present excellent overall properties, including superhigh porosity (95.09%–93.10%), lightweight (0.29–0.41 g/cm 3 ), and very low thermal conductivity (0.066–0.085 W/(m·K)). More importantly, porous (Y 0.25 Ho 0.25 Yb 0.25 Lu 0.25 ) 2 Si 2 O 7 has outstanding high‐temperature dimensional stability. Although the porosity of the sample is higher than 90%, its linear shrinkage at 1550°C for 2 h is less than 1%. The results demonstrate that porous high‐entropy (Y 0.25 Ho 0.25 Yb 0.25 Lu 0.25 ) 2 Si 2 O 7 is a promising thermal insulation material in extreme high‐temperature environments.