12355-99-6Relevant academic research and scientific papers
Confined-plume chemical deposition: Rapid synthesis of crystalline coatings of known hard or superhard materials on inorganic or organic supports by resonant IR decomposition of molecular precursors
Ivanov, Borislav L.,Wellons, Matthew S.,Lukehart, Charles M.
, p. 11744 - 11750 (2009)
A one-step process for preparing microcrystalline coatings of known superhard, very hard, or ultraincompressible ceramic compositions on either inorganic or organic supports is reported. Midinfrared pulsed-laser irradiation of preceramic chemical precurso
Preparation and properties of metallic, superhard rhenium diboride crystals
Levine, Jonathan B.,Nguyen, Sandy L.,Rasool, Haider I.,Wright, Jeffrey A.,Brown, Stuart E.,Kaner, Richard B.
, p. 16953 - 16958 (2008)
Single crystals of ReB2 have been prepared from an aluminum flux under inert gas flow. The crystals are typically 1-3 mm in diameter and 500 μm thick, growing along the [002] direction with a distinct hexagonal morphology. Vickers microhardness and nanoindentation testing indicate that the (002) plane possesses the highest hardness with measured values of 40.5 and 36.4 GPa, respectively. The elastic anisotropy was examined and the indentation moduli of the basal plane and an (MO) plane of unknown indices are 675 and 510 GPa, respectively. Four-probe electrical resistivity measurements demonstrate that ReB2 is the hardest material known to exhibit metallic behavior. Thermogravimetric analysis indicates that the crystals are stable in air up to 1000°C due to the formation of a protective boron oxide coating.
Correlation between hardness and elastic moduli of the ultraincompressible transition metal diborides RuB#!2, OsB2, and ReB2
Chung, Hsiu-Ying,Weinberger, Michelle B.,Yang, Jenn-Ming,Tolbert, Sarah H.,Kaner, Richard B.
, (2008)
The ultraincompressible transition metal diborides RuB#!2, OsB2, and ReB2 were synthesized by arc melting the elemental metals and boron under an argon atmosphere at ambient pressure. The hardness and Young's modulus were measured using nanoindentation with a Berkovich diamond indenter. The bulk modulus and shear modulus were derived based on an isotropic model and then plotted as a function of hardness. A strong correlation is observed between the hardness and shear modulus for these transition metal diborides.
High-temperature hardness of ReB2 single crystals
Otani,Korsukova,Aizawa
, p. L28-L29 (2009)
Vickers micro-hardness was measured on the (0 0 0 1) and (1 0 - 1 0) planes of ReB2 single crystals. By increasing the temperature from 20 to 1000 °C, the hardness decreased from 30.8 to 19.8 GPa and from 35.8 to 14.3 GPa, respectively. ReBsub
Crystal structures of the metal diborides ReB2, RuB2, and OsB2 from neutron powder diffraction
Frotscher, Michael,Hoelzel, Markus,Albert, Barbara
, p. 1783 - 1786 (2010)
Because of the very small scattering power of the light element, the crystal structures of metal borides that contain heavy metal atoms are difficult to determine unambiguously from X-ray diffraction data only. Using neutron diffraction methods and applying them to isotopically enriched 11B boride powders, the crystal structures of ReB2, RuB2, and OsB2 were re-determined and analysed with respect to the boron atom arrangement. In accordance with the findings from X-ray diffraction experiments, the structures exhibit corrugated boron atom layers of conjugated six-rings, either seat-like (ReB2) or boatlike (RuB2, OsB 2). ReB2 crystallises in the hexagonal crystal system, space group P63/mmc (no. 194, a = 290.05(1) pm, c = 747.72(1) pm); OsB2 and RuB2 are isostructural and crystallise orthorhombically, space group Pmmn (no. 59, a = 464.479(5) pm, b = 286.515(3) pm, c = 404.560(6) pm (RuB2); a = 468.408(5) pm, b = 287.255(3) pm, c = 407.693(6) pm (OsB2)). Boron-boron distances vary between 181.7 and 189.9 pm. For RuB2 and OsB2, shortest metal-boron distances range from 217.2 to 217.3 pm, indicating a covalent interaction between metal and boron, compared to 222.7 pm for ReB2. Metal- metal distances are between 286.5 pm and 302.2 pm. All three compounds have been described as very hard or incompressible materials.
KINETICS OF FORMATION OF MOLYBDENUM, TUNGSTEN AND RHENIUM BORIDES FROM BORON-NITRIDE- POWDER METAL MIXTURES,
BAEHREN TH FD,THUEMMLER F,VOLLATH D
, p. 295 - 303 (1969)
Karlsruhe, West Germany
THERMAL EXPANSION STUDIES ON THE GROUP IV-VII TRANSITION METAL DIBORIDES.
Loennberg
, p. 145 - 156 (2008/10/08)
The thermal expansions of the group IV-VII transition metal diborides were studied with the aid of X-ray powder diffraction. The diborides were studied over the temperature range 298 - 1500 K. All the diborides except for CrB//2 display larger thermal expansion coefficients in the c direction than in the a direction. The expansion coefficients in the c direction decrease with increasing radius of the metal atom, a fact which can be correlated to an increase in metal-boron bond strength. The thermal expansion coefficient in the a direction changes very little with the size of the metal radius, owing to the fact that the bonding strength in the basal plane is determined by the strong B-B bonds within the boron layer.
