Effect of adding diamond particles on the fracture toughness of apatite ceramics

Composite ceramics dispersed through diamond particles with hydroxyapatite as a matrix were prepared by firing at 1250 degrees C under reduced pressure or normal atmosphere. The fracture toughness and physical properties of sintered composite ceramics were examined to determine methods of strengthening hydroxyapatite ceramics. The diamond crystal in composite ceramics was transformed to graphite by firing and the fracture toughness of hydroxyapatite ceramics increased with diamond addition. At 10 wt% diamond, the maximum value for fracture toughness was obtained, and the further addition of diamond particles over 10 wt% caused fracture toughness to decrease. Such increases in fracture toughness were considered the result of microcracking which occurred during the transformation from diamond to graphite.