Hot Pressed HfB2 and HfB2-20 vol%SiC Ceramics Based on HfB2 Powder Synthesized by Borothermal Reduction of HfO2

• Published in: International journal of applied ceramic technology Vol. 7; no. 6; pp. 830 - 836
• Main Authors: Ni, De-Wei, Zhang, Guo-Jun, Kan, Yan-Mei, Wang, Pei-Ling
• Format: Journal Article
• Language: English
• Published: Malden, USA Blackwell Publishing Inc 01.11.2010
• Subjects: Ceramics; Density; Fracture mechanics; Grain size; Hafnium; Hafnium oxide; Reduction; Silicon carbide
• ISSN: 1546-542X; 1744-7402
• DOI: 10.1111/j.1744-7402.2009.02404.x

Phase pure hafnium diboride (HfB2) powder was synthesized by borothermal reduction of hafnium dioxide using amorphous boron at relatively low temperature (1600°C) in vacuum. The synthesized HfB2 powder had an average particle size of 1.37 μm with an equiaxed shape, and a low oxygen content of 0.79 wt%. Using the as‐synthesized HfB2 powder and a commercial SiC, HfB2 monolithic, and HfB2–20 vol%SiC composite were hot pressed at 2000°C to relative densities of 95.7% and 99.2%, respectively. With the addition of SiC, the grain size decreased and the fracture behavior changed from intergranular to a mixed mode, which resulted in a high flexural strength of 993±90 MPa for the composite. Fracture toughness of the composite was 6.29±0.65 MPa m1/2, which was significantly higher than that of the HfB2 monolithic and the reported values in literature.