Sintering and Mechanical Properties of ZrB2-TaSi2 and HfB2-TaSi2 Ceramic Composites

• Published in: Journal of the American Ceramic Society Vol. 91; no. 10; pp. 3285 - 3291
• Main Authors: Sciti, Diletta, Silvestroni, Laura, Celotti, Giancarlo, Melandri, Cesare, Guicciardi, Stefano
• Format: Journal Article
• Language: English
• Published: Malden, USA Blackwell Publishing Inc 01.10.2008
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/j.1551-2916.2008.02593.x

Fully dense fine‐grained ZrB2‐ and HfB2‐based composites contaning 15 vol% TaSi2 were produced by hot pressing at 1850°–1900°C. Gas formation and mass loss, which occurred during sintering in both systems, were in agreement with thermodynamic predictions. In both composites, the presence of a solid solution formed by the diffusion of tantalum into the boride matrix was observed. The HfB2‐based composite was harder (22 GPa), stiffer (528 GPa), and tougher (4.1M Pa·m1/2) than the ZrB2‐based composite. Although the room‐temperature flexural strength of the ZrB2‐based composite (830 MPa) was higher than that of the HfB2‐based composite (700 MPa), the opposite was true at 1200° and 1500°C. Contrary to the significant strength decrease observed for the ZrB2‐based materials at elevated temperature, the HfB2 composite retained ∼86% of its room temperature strength up to 1500°C (∼600 MPa).