Ruthenium boride explained

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]

Notes and References

1. J.V. Rau et al. "Deposition and characterization of superhard biphasic ruthenium boride films" Acta Materialia 57 (2009) 673
2. Chung. Hsiu-Ying. April 20, 2007. Synthesis of Ultra-Incompressible Superhard Rhenium Diboride at Ambient Pressure. Science. 316. 5823. 436–9. 10.1126/science.1139322. 17446399. 2007Sci...316..436C . 10395879. etal.
3. J. Qin et al. "Is Rhenium Diboride a Superhard Material?" Adv. Mater. 20 (2008) 4780
4. C. P. Kempter and R. J. Fries "Crystallography of the Ru-B and Os-B Systems" J. Chem. Phys. 34, 1994 (1961)
5. 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)