Transmission Electron Microscopy Investigation of Hot-pressed ZrB₂-SiC with B₄C Additive

Abstract

This paper reports the microstructure of hot-pressed ZrB 2 -SiC ceramics with added B 4 C as characterized by transmission electron microscopy. ZrB 2 has a melting point of 3245 o C, a relatively low density of 6.1 g/cm 3 , and specific mechanical properties at an elevated temperature, making it a candidate for application to environments with ultra-high temperatures which exceed 2000 o C. Due to the non-sinterability of ZrB 2 -based ceramics, research on sintering aids such as B 4 C or MoSi 2 has become prominent recently. From TEM investigations, an amorphous layer with contaminant oxide is observed in the vicinity of B 4 C grains remaining in hot-pressed ZrB 2 -SiC ceramics with B 4 C as an additive. The effect of a B 4 C addition on the microstructure of this system is also discussed.

A TEM study of nanostructures and interfaces in the hot-press sintered ZrB2–SiC–Si3N4 composites

“…Based on their significant combination of characteristics such as high strength, high hardness, acceptable thermal shock resistance, high melting point, and machinability, these ceramics attracted a considerable amount of attention in applications like aerospace vehicles, propulsion systems, and in general, high-temperature industries [1][2][3][4][5]. Among the UHTCs, ZrB 2 -based ceramics are in priority and are the best candidates for applications like thermal protection systems (TPS) or refractory crucibles [6]. Despite favorable features of ZrB 2 -based materials, some deficiencies, such as low sinterability because of covalent strong bonds, relatively low fracture toughness, and poor oxidation resistance, restrict the ZrB 2 -based ceramics utilization in many industries [7].…”