High bending strength at 1800 °C exceeding 1 GPa in TiB2-B4C composite

Abstract

High density (99.5%) ceramic composite composed of titanium boride and boron carbide (70/30 vol%) was obtained by spark plasma sintering and was tested by 3-point bending test in Ar atmosphere at 1800 °C. Bending strength was high, around 1.1 GPa. The strength–strain curve presents a peculiar shape composed of three regions where elastic and plastic deformations are active with a different weight. Based on transmission electron microscopy observations we propose a process of mechanical energy absorption driven by shear stress in the boron carbide crystals: stacking faults with (1-11) and (011) stacking planes and twins with (1-11) twinning plane rearrange into nano-twins with (10-1) twinning planes, orthogonal but equivalent to the initial ones. This rearrangement mechanism provides in the first instance a plastic signature, but further contributes strengthening.

Ultralow lattice thermal conductivity in type-I Dirac MBene TiB2

“…Interestingly, κ L values for ML and BL are significantly lower at higher temperatures, comparable to some of the lowest reported values for promising thermoelectric materials [54,55], where the order of κ L for TlSe (0.65 W m −1 K −1 [55]) and SnSe (0.47 W m −1 K −1 [54]) is comparable to both ML and BL in y-direction. However, we have further demonstrated the ultralow lattice thermal conductivity κ L for ML (0.13 W m −1 K −1 ) and BL (0.21 W m −1 K −1 ) in x-direction, where ultralow κ L for TiB 2 MBene at higher temperatures makes it a promising candidate for high-temperature thermal applications while TiB 2 based composites are reported to perform at extreme temperatures approaching 1800 • C [56,57]. As TiB 2 MBene can easily sustain 900 K, our results demonstrating the ultralow lattice thermal conductivity of ML and BL at higher temperature indicates this Dirac MBene as a potential thermoelectric material.…”