Spark plasma sintering of TiN–TiB2–hBN composites and their properties

Abstract

TiN–TiB2–hBN composites (where hBN denotes hexagonal boron nitride) were prepared by spark plasma sintering at 1973K for 300s under 100MPa. The hBN content was varied from 0 to 30% of the total volume of the composite, while maintaining a TiN:TiB2 ratio of 30:70vol%. The effects of hBN content on the densification, microstructure, mechanical properties and thermal conductivities of the composites were investigated. Regardless of hBN content, TiN–TiB2–hBN composites showed high relative densities (96–97%). At the optimal hBN content (15vol%), the composites also showed high hardness and fracture toughness (20.1GPa and 4.3MPam1/2, respectively), and their thermal conductivity increased from 58.1 to 63.4Wm−1K−1 as the temperature was increased from 293 to 973K. In contrast, the thermal conductivity of most ceramics decreases with increasing temperature.