Ruthenium boride

High hardness element compounds of ruthenium and boron

Ruthenium borides are compounds of ruthenium and boron. Their most remarkable property is potentially high hardness. Vickers hardness H_V = 50 GPa was reported for thin films composed of RuB₂ and Ru₂B₃ phases.^[1] This value is significantly higher than those of bulk RuB₂ or Ru₂B₃, but it has to be confirmed independently, as measurements on superhard materials are intrinsically difficult. For example, note that the initial report on extreme hardness of related material rhenium diboride^[2] was probably too optimistic.^[3]

Structure

Ruthenium diboride was first thought to have a hexagonal structure,^[4] as in rhenium diboride, but it was later tentatively determined to possess an orthorhombic structure.^[5]

References

^ J.V. Rau et al. "Deposition and characterization of superhard biphasic ruthenium boride films" Acta Materialia 57 (2009) 673
^ Chung, Hsiu-Ying; et al. (April 20, 2007). "Synthesis of Ultra-Incompressible Superhard Rhenium Diboride at Ambient Pressure". Science. 316 (5823): 436–9. Bibcode:2007Sci...316..436C. doi:10.1126/science.1139322. PMID 17446399. S2CID 10395879.
^ J. Qin et al. "Is Rhenium Diboride a Superhard Material?" Adv. Mater. 20 (2008) 4780
^ C. P. Kempter and R. J. Fries "Crystallography of the Ru-B and Os-B Systems" J. Chem. Phys. 34, 1994 (1961)^{[permanent dead link]}
^ R. B. Roof, Jr. and C. P. Kempter "New Orthorhombic Phase in the Ru-B and Os-B Systems" J. Chem. Phys. 37, 1473 (1962)^{[permanent dead link]}