High-temperature properties of a silicon nitride/boron nitride nanocomposite

Abstract

Hexagonal graphitic BN (h-BN) is interesting as a second phase for high-temperature structural ceramics because it has the same crystal structure as graphite, for which fracture strength and Young’s modulus increase with increased temperature. In this study, high-temperature mechanical properties of Si3N4/BN nanocomposite were evaluated to clarify the effect of fine h-BN particles at elevated temperatures. As a result, we found that high-temperature strength and hardness of the nanocomposite were maintained up to high temperatures; also, its Young’s modulus increased gradually, concomitant with elevated temperatures up to 1400 °C. Finally, these properties were compared with those of monolithic Si3N4 and Si3N4/BN microcomposite.

Fabrication of Alumina Ceramic Reinforced with Boron Nitride Nanotubes with Improved Mechanical Properties

“…Furthermore, a sharp decrease in strength occurs at 700°C, which is slightly higher than the critical temperature of the monolith (~600°C). As indicated in literature, the strength degradation of ceramics at elevated temperature was caused by softening of the glassy phases at grain boundaries, consequent sliding of grain boundary, and cavitations . However, it is difficult for the grain boundary sliding and cavitations to happen at such low temperatures.…”

“…Rapid Communications of the American Ceramic Society consequent sliding of grain boundary, and cavitations. 36 However, it is difficult for the grain boundary sliding and cavitations to happen at such low temperatures. Therefore, the degradation of flexure strength is attributed to the softening of grain boundary glassy phase in the process of heating.…”

Computer Aided Multi-scale Design of SiC-Si3N4 Nanoceramic Composites for High-Temperature Structural Applications

“…Accordingly, the influence of temperature on the flow stress results in this quantity decreasing to around 700 MPa and 400 MPa at 1400 °C and 1600 °C respectively [99,100].…”

Machinable α‐SiAlON/BN Composites

“…M onolithic Si 3 N 4 /SiAlON ceramics have excellent mechanical properties but poor machinability, which increases the fabrication costs. As a remedy, several β‐Si 3 N 4 /BN “nanocomposites” have been reported that combine machinability and excellent mechanical properties 1–4 . To achieve this goal, it is imperative to maintain a highly homogeneous dispersion of fine BN particles.…”

“…This approach was taken by Kusunose et al . and Oku et al ., for example 1–4,10 . In their work, reaction of boric acid and urea in hydrogen gas at 1100°C, followed by annealing in nitrogen gas at 1500°C, was used to prepare tBN.…”