Beneficial effect of low BN additive on densification and mechanical properties of hot-pressed ZrB۲–SiC composites

The incorporation of ۱ wt% hexagonal BN (hBN) into ZrB۲–۳۰ vol% SiC could noticeably better the fracture toughness, hardness, and consolidation behavior of this composite. This research intended to scrutinize the effects of various amounts of hBN (۰–۵ wt%) on different characteristics of ZrB۲–SiC materials. The hot-pressing method under ۱۰ MPa at ۱۹۰۰ °C for ۱۲۰ min was employed to sinter all designed specimens. Afterward, the as-sintered samples were characterized using X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and Vickers technique. The hBN addition up to ۱ wt% improved relative density, leading to a near fully dense sample; however, the incorporation of ۵ wt% of such an additive led to a composite containing more than ۵% remaining porosity. The highest Vickers hardness of ۲۳.۸ GPa and fracture toughness of ۵.۷ MPa.m۱/۲ were secured for the sample introduced by only ۱ wt% hBN. Ultimately, breaking large SiC grains, crack bridging, crack deflection, crack branching, and crack arresting were introduced as the chief toughening mechanisms in the ZrB۲–SiC–hBN system.© ۲۰۲۱ The Authors. Published by Synsint Research Group.

کلیدواژه ها:

Ultrahigh temperature ceramics ، Hot-pressing ، Microstructure ، Mechanical properties