| Abstract Scope |
The latest generation UHTCs, based on a boride matrix and sintered in the presence of transition metal (TM) compounds, has demonstrated strengths beyond current benchmark ranges, with peaks of ~1 GPa at 1800°C and strengths above 600 MPa up to 2100°C. Microstructural analyses disclosed a unique multi-scale microstructural arrangement with the TM partially dissolved into the boride matrix, forming core-shell grains during sintering, and wreathed with TM-based nano-particles. This complex hierarchical microstructure, featured by several levels of spatial variations, is thought to be responsible for the elevated temperature strengthening.
Subsequent studies are now considering other transition metals, like Ti, Nb, V and Cr.
Here, we present how the microstructure of ZrB2-based ceramics with addition of various TM evolves from the sintering process, to oxidation at 1500°C and upon arc-jet tests. Emphasis is given to the formation of the nanoinclusions and their role on the mechanical and thermal behavior. |