Microstructure and mechanical properties of multiwalled carbon nanotube toughened spark plasma sintered ZrB₂ composites

Abstract

ZrB₂ based composites containing 10 vol.-% carbon nanotubes (CNTs) are synthesised by spark plasma sintering at temperatures ranging from 1600 to 18008C and at an applied pressure of 25 MPa. The effects of sintering temperature on densification behaviour, microstructural evolutions and mechanical properties are presented. Results indicate that ZrB₂-CNT composites fabricated at 16508C have the optimal combination of dense microstructure and properties. The fracture toughness is sensitive to the temperature change and reaches 7.2 MPa m^1/2 for the CNT toughened ZrB₂ ceramics, which is higher than the measured result for monolithic ZrB₂ (3.3 MPa m^1/2). The crack deflection and CNT pullout are the dominant toughening mechanisms.

Keywords:

• Ultrahigh temperature ceramics
• Spark plasma sintering
• Mechanical properties
• Structural applications

Acknowledgements

This work was supported by the Science Foundation of Xiamen University of Technology (grant nos. YKJ13009R and XYK201408), Science and Technology Project of Xiamen City (grant no. 3502Z20143036), NSFC (grant no. 51402248) and A-Project for the Education Department of Fujian Province (grant no. JA14236).