Effect of C۳N۴ content on the densification and mechanical characteristics of spark plasma sintered ZrB۲ ceramics

In this research, ZrB۲ ceramic containing ۲.۵ and ۷.۵ wt% C۳N۴ were manufactured by spark plasma sintering(SPS) at ۱۸۵۰ ºC for ۶ min under ۴۰ MPa. The effect of C۳N۴ content as a sintering aid on microstructuralrefinement and mechanical properties (Vickers hardness, fracture toughness, and bending strength) of SPSedZrB۲ was investigated. Near fully dense sample with relative density of ۹۹.۹ was achieved by addition of ۷.۵wt% C۳N۴. The grain growth of ZrB۲ was restricted by increasing in C۳N۴ content. Vickers hardness andfracture toughness increased from ۱۵.۲ and ۳.۲ to ۱۶.۶ GPa and ۵ MPa.m۱/۲,when C۳N۴ content increasedfrom ۲.۵ to ۷.۵ wt%, respectively, but bending strength decreased from ۴۴۵.۶ to ۴۰۰ MPa. The in-situformation of ZrC and h-BN led to enhancement of fracture toughness through activating various tougheningmechanisms including crack bridging, crack branching, and crack deflection.

Keywords:

ZrB۲ , C۳N۴ , SPS , Sintering aid , Sinterability , Mechanical properties