Theoretical predictions of stability, electronic properties, elastic anisotropy, thermodynamics, and optical properties of MB2 (M = V, Nb, Zr)

Low temperature controllable synthesis of transition metal and rare earth borides mediated by molten salt

“…The only difference was in the particle size of the final product. The particle size of TiB 2 (30-100 nm) generated from Reaction (14) overall was slightly smaller than that (40-200 nm) from Reaction (15).…”

“…Typical properties of some transition metal diborides. [9][10][11][12][13][14][15][16][17][18] Boride Density/ g cm −3 feasible alternatives is the so-called 'molten salt synthesis (MSS)' technique. Over the past 10-15 years, a range of transition metal and rear earth borides have been synthesised successfully via this approach.…”

“…There exist a multitude of metal borides among which transition metal diborides (TMDBs) and rare earth hexaborides (REHBs) have been subjected to the most extensive investigations owing to their unique structures, superior properties, and great potential for diverse applications. 1–46 The former possesses a simple AlB 2 -type crystal structure with a space group of P6/mmm in which the hexagonal close-packed metal layers alternate with the boron (B) layers (Figure 1(a)), 20 and the latter possesses a CsCl-type structure with a space group of Pm-3m in which the rare earth metal atoms and the B atoms occupy respectively the Cs sites and the octahedral sites, and one B 6 octahedron is surrounded by eight rare earth metal atoms (Figure 1(b)). 22 Among the 17 existing rare-earth metal elements, however, only 13 form stable corresponding hexaborides, that is RB 6 (R = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Yb) 22 (LuB 6 and TmB 6 can be formed as metastable phases).…”

“…The unique crystal structures of these two classes of borides along with their strong bonding systems confer on them a variety of excellent properties. TMDBs exhibit both metal- and ceramic-like properties (many of which are highly anisotropic), including ultra-high melting point, high mechanical strength, hardness, and elastic modulus, good fracture toughness, excellent wear and chemical resistances, as well as relatively high electrical and thermal conductivities 1–21 (Table 1), 9–18 making them suitable for a number of demanding applications in, for example thermal protection system of hypersonic vehicle, rocket propulsion system, concentrated solar absorber, wear-resistant component or cutting tool, amour, thermal barrier coating, refractories, nuclear fuel cladding Ohmic contact, neutron shield in nuclear engineering and high-temperature electrode. 1–21 REHBs also possess numerous outstanding mechanical, thermal and chemical properties such as high melting point, high mechanical strength, low volatility at high temperature, good thermal conductivity and excellent chemical resistance, though they are often considered for their superior functional properties, especially their electrical and magnetic properties such as low work function, high e...…”