effect of c3n4 content on the densification and mechanical characteristics of spark plasma sintered zrb2 ceramics

In this research, zrb2 ceramic containing 2.5 and 7.5 wt% c3n4 were manufactured by spark plasma sintering (sps) at 1850 ºc for 6 min under 40 mpa. the effect of c3n4 content as a sintering aid on microstructural refinement and mechanical properties (vickers hardness, fracture toughness, and bending strength) of spsed zrb2 was investigated. near fully dense sample with relative density of 99.9 was achieved by addition of 7.5 wt% c3n4. the grain growth of zrb2 was restricted by increasing in c3n4 content. vickers hardness and fracture toughness increased from 15.2 and 3.2 to 16.6 gpa and 5 mpa.m1/2,when c3n4 content increased from 2.5 to 7.5 wt%, respectively, but bending strength decreased from 445.6 to 400 mpa. the in-situ formation of zrc and h-bn led to enhancement of fracture toughness through activating various toughening mechanisms including crack bridging, crack branching, and crack deflection.