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 degrees 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. (C) 2011 Elsevier Ltd. All rights reserved.