Fabrication, mechanical properties and thermal shock resistance of a ZrB2-graphite ceramic

A ZrB2 ceramic containing 25 vol.% graphite flake (ZrB2-graphite) ceramic was fabricated by hot-pressing at 1950 °C. It was shown that the fracture toughness was significantly improved due to the addition of graphite flake whereas the flexure strength and hardness were slightly reduced. The increase in fracture toughness was attributed to the presence of soft graphite flake and weaker interface bonding. The decrease in the flexural strength was due to the increase in weakening factors such as the weaker bonding within the ZrB2-graphite ceramic and lower load transfer since the lower mechanical property of the graphite flake as well as graphite flakes acted as flaws in the ZrB2-graphite ceramic. The thermal shock resistance was significantly improved and the improvement mechanism in thermal shock resistance was analyzed by Griffith fracture criterion and finite element analysis.

Research highlights
► This paper is to report on the fabrication and an initial investigation on ZrB2-graphite ceramic.
► The fracture toughness of the ZrB2-graphite ceramic is essentially improved.
► Improvement mechanism in thermal shock resistance was analyzed by Griffith criterion and FEA.
► The results pointed to a potential method for improving toughness and thermal shock resistance.