The stability of hexagonal ReB2 type OsB2 powder upon heating under reforming gas was investigated. Pure Os metal particles were detected by powder X-ray diffraction starting at 375°C and complete transformation of OsB2 to metallic Os was observed at 725°C. The mechanisms of precipitation of metallic Os is proposed and changes in the lattice parameters of OsB2 upon heating are analysed in terms of the presence of oxygen or water vapour in the heating chamber. Previous studies suggested that Os atoms possess (0) valence, while B atoms possess both (+3) and (−3) valences in the alternating boron/osmium sheet structure of hexagonal (P63/mmc, No. 194) OsB2; if controllable method for Os removal from the lattice could be found, the opportunity would arise to form two-dimensional (2D) layers consisting of pure B atoms.
JayaseelanDD, WangY, HilmasGE, FahrenholtzW, BrownP and LeeWE: ‘TEM investigation of hot pressed −10 vol.%SiC–ZrB2 composite’, Adv. Appl. Ceram., 2011, 110, 1–7.
2.
KhanraAK and GodkhindiMM: ‘Effect of Ni additives on pressureless sintering of SHS ZrB2’, Adv. Appl. Ceram., 2005, 104, 273–276.
3.
DobedoeRS, WestGD and LewisMH: ‘Spark plasma sintering of ceramics: understanding temperature distribution enables more realistic comparison with conventional processing’, Adv. Appl. Ceram., 2005, 104, 110–116.
4.
OrlovskayaN, StadelmannR, LugovyM, SubbotinV, SubhashG, NeubertM, AnezirisCG, GrauleT and KueblerJ: ‘Mechanical properties of ZrB2–SiC ceramic composites: room temperature instantaneous behaviour’, Adv. Appl. Ceram., 2013, 112, 9–16.
5.
PadovanoE, BadiniC, BiaminoS, PaveseM, YangWS and FinoP: ‘Pressureless sintering of ZrB2–SiC composite laminates using boron and carbon as sintering aids’, Adv. Appl. Ceram., 2013, 112, 478–486.
6.
GanemB and OsbyJO: ‘Synthetically useful reactions with metal boride and aluminide catalysts’, Chem. Rev., 1986, 86, 763–780.
7.
MoriT: ‘Chapter 238 – higher borides’, in ‘Handbook on the physics and chemistry of rare earths’, Vol. 38, (ed. J.-C. G. B. Karl et al.), 105–173; 2008, Amsterdam, Elsevier.
8.
SonberJK and SuriAK: ‘Synthesis and consolidation of zirconium diboride: review,’ Adv. Appl. Ceram., 2011, 110, 321–334.
9.
KhanraAK, PathakLC and GodkhindiMM: ‘Carbothermal synthesis of zirconium diboride (ZrB2) whiskers’, Adv. Appl. Ceram., 2007, 106, 155–160.
10.
JalalyM, BafghiMSh, TamizifarM and GotorFJ: ‘Mechanosynthesis of nanocrystalline ZrB2-based powders by mechanically induced self-sustaining reaction method’, Adv. Appl. Ceram., 2013, 112, 383–388.
11.
KhanraAK, PathakLC, MishraSK and GodkhindiMM: ‘Sintering of ultrafine zirconium diboride powder prepared by modified SHS technique,’ Adv. Appl. Ceram., 2005, 104, 282–284.
12.
WuH, XieC, ZhangW and ZhangJ: ‘Fabrication and properties of 2D C/C–ZrB2–ZrC–SiC composites by hybrid precursor infiltration and pyrolysis’, Adv. Appl. Ceram., 2013, 112, 366–373.
13.
ChungH.-Y, WeinbergerMB, LevineJB, KavnerA, YangJ.-M, TolbertSH and KanerRB: ‘Synthesis of ultra-incompressible superhard rhenium diboride at ambient pressure’, Science, 2007, 316, 436–439.
14.
LevineJB, NguyenSL, RasoolHI, WrightJA, BrownSE and KanerRB: ‘Preparation and properties of metallic, superhard rhenium diboride crystals’, J. Am. Chem. Soc., 2008, 130, 16953–16958.
15.
CumberlandRW, WeinbergerMB, GilmanJJ, ClarkSM, TolbertSH and KanerRB: ‘Osmium diboride, an ultra-incompressible, hard material’, J. Am. Chem. Soc., 2005, 127, 7264–7265.
16.
OrlovskayaN, XieZ, KlimovM, HeinrichH, RestrepoD, BlairR and SuryanarayanaC: ‘Mechanochemical synthesis of ReB2 powder’, J. Mater. Res., 2011, 26, 2772–2779.
17.
HebbacheM, StuparevićL and ŽivkovićD: ‘A new superhard material: Osmium diboride OsB2’, Solid State Commun., 2006, 139, 227–231.
18.
ChungH.-Y, YangJM, TolbertSH and KanerRB: ‘Anisotropic mechanical properties of ultra-incompressible, hard osmium diboride’, J. Mater. Res., 2008, 23, 1797–1801.
19.
XieZ, GrauleM, OrlovskayaN, Andrew PayzantE, CullenDA and BlairRG: ‘Novel high pressure hexagonal OsB2 by mechanochemistry’, J. Solid State Chem., 2014, 215, 16–21.
20.
OrlovskayaN, XieZ and BlairR: ‘Mechanochemical synthesis of hexagonal OsB2’, US Patent 20,140,199,226, 2014.
21.
CarencoS, PortehaultD, BoissièreC, MézaillesN and SanchezC: ‘Nanoscaled metal borides and phosphides: recent developments and perspectives’, Chem. Rev., 2013, 113, 7981–8065.
22.
XieZ, BlairRG, OrlovskayaN, CullenDA and Andrew PayzantE: ‘Thermal stability of hexagonal OsB2: negative thermal expansion’, J. Solid State Chem., 2014, 219, 210–219.
23.
DeanJA and LangeNA: ‘Lange's handbook of chemistry’; 1992, New York, McGraw-Hill.
24.
ChenX.-Q, FuCL, KrčmarM and PainterGS: ‘Electronic and structural origin of ultraincompressibility of 5d transition-metal diborides MB2 (M = W, Re, Os)’, Phys. Rev. Lett., 2008, 100, 196403.
25.
GurvichLV: ‘Reference books and data banks on the thermodynamic properties of individual substances’, Pure Appl. Chem., 1989, 61, 1027–1031.
26.
GlassmanI and YetterRA: ‘Chapter 9 – Combustion of nonvolatile fuels’, in ‘Combustion’, 4th edn, (ed. I. Glassman and R. A. Yetter), 495–550; 2008, Burlington, Academic Press.
27.
AkulovaLT, VlasovaMV, VoropaevaIV and HorpyakovOT: ‘Behaviour of molybdenum diboride in resistive thick film’, J. Mater. Sci., 1992, 27, 3293–3296.
