“…1,2 Among them, diborides such as ZrB 2 and HfB 2 have a unique combination of mechanical and physical properties: high melting points (>3000 • C); high thermal and electrical conductivity; chemical inertness against molten metals; great thermal shock resistance. [1][2][3] Thus, although carbides typically have the highest melting points (>3500 • C), the diborides ZrB 2 and HfB 2 are more attractive candidates for high-temperature thermomechanical structural applications at temperatures ≥3000 • C. 1,2 Potential applications include thermal protective structures for leading-edge parts on hypersonic re-entry space vehicles, 1,4 propulsion systems, 1,4 furnace elements, 5 refractory crucibles, 5 and plasma-arc electrodes. 5,6 In particular, ZrB 2 has the lowest theoretical density among the ultra-high temperature ceramics, which makes it an attractive material for aerospace applications.…”