Novel high pressure hexagonal OsB2 by mechanochemistry

Xie, Zhilin; Graule, Moritz A.; Orlovskaya, Nina; Payzant, E. Andrew; Cullen, David A.; Blair, Richard G.

doi:10.1016/j.jssc.2014.03.020

Cited by 34 publications

(43 citation statements)

References 28 publications

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“…Therefore a transition oP6-OsB 2 to hP6-OsB 2 could be expected at high pressure. This was theoretically predicted by Ren et al [65], and recently confirmed experimentally [66]. Finally one observes that the molar volume of the hP3 structure is always smaller than the one of the hR6, hP12 structures.…”

Section: Resultssupporting

confidence: 73%

Enthalpies of Formation of Transition Metal Diborides: A First Principles Study

Colinet

Tedenac

2015

Crystals

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Abstract:The enthalpies of formation of transition metals diborides in various structures have been obtained from density functional theory (DFT) calculations in order to determine the ground state at T = 0 K and p = 0. The evolution of the enthalpies of formation along the 3D, 4D, and 5D series has been correlated to the considered crystal structures. In the whole, the calculated values of the enthalpies of formation of the diborides in their ground state are in good agreement with the experimental ones when available. The calculated values of the lattice parameters at T = 0 K of the ground state agree well with the experimental values. The total and partial electronic densities of states have been computed. Special features of the transition metal electronic partial density of states have been evidenced and correlated to the local environment of the atoms.

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Section: Resultssupporting

confidence: 73%

Enthalpies of Formation of Transition Metal Diborides: A First Principles Study

Colinet

Tedenac

2015

Crystals

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“…3. Similarly to the results upon heating of OsB 2 in Ar with traces of oxygen, 19 the lattice expansion both in a and c direction along with volumetric expansion occurred upon heating from room temperature to about 300uC; however, upon reaching 325uC, the shrinkage of a lattice parameter began with a significant decrease from 325uC, where a was equal to 2?915 Å , to 425uC, where a became equal to 2?912 Å . Then, upon further temperature increase from 425uC, the a lattice parameter of OsB 2 started increasing again until 625uC where the OsB 2 phase could still be identified by XRD.…”

Section: Resultssupporting

confidence: 66%

Hexagonal OsB₂reduction upon heating in H₂containing environment

Xie

Blair

Orlovskaya

et al. 2014

Advances in Applied Ceramics

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The stability of hexagonal ReB 2 type OsB 2 powder upon heating under reforming gas was investigated. Pure Os metal particles were detected by powder X-ray diffraction starting at 375uC and complete transformation of OsB 2 to metallic Os was observed at 725uC. The mechanisms of precipitation of metallic Os is proposed and changes in the lattice parameters of OsB 2 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 (z3) and (23) valences in the alternating boron/osmium sheet structure of hexagonal (P63/mmc, No. 194) OsB 2 ; 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.

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“…Theoretical study suggested that OsB 2 could have three crystal structures: RuB 2 ‐type orthorhombic, ReB 2 ‐type hexagonal, and AlB 2 ‐type hexagonal structures . ReB 2 ‐type hexagonal OsB 2 was reported to be synthesized successfully for the first time by Xie et al at 2014 . Previously all experimentally synthesized OsB 2 were orthorhombic phase.…”

Section: Introductionmentioning

confidence: 99%

Effects of Re addition on phase stability and mechanical properties of hexagonal OsB₂

et al. 2017

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ReB 2 -type hexagonal Osmium diboride (OsB 2 ) has been predicted to exhibit higher hardness than its orthorhombic phase, but hexagonal-orthorhombic phase transformation occurs at temperature higher than 600°C, resulting in the decrease in its hardness. Therefore, ReB 2 -type hexagonal OsB 2 samples with Re addition were produced by a combination of mechanochemical method and pressureless sintering technique, and the effects of Rhenium (Re) addition on phase composition, thermal stability and mechanical properties of OsB 2 were investigated in this study. X-ray diffraction (XRD) analysis of the as-synthesized powders by high-energy ball milling indicates the formation of hexagonal Os 1-x Re x B 2 solid solution with Re concentration of 5 and 10 at.% without forming a second phase. After being sintered at 1700°C, part of the hexagonal phase in OsB 2 transformed to orthorhombic structure, while Os 0.95 Re 0.05 B 2 and Os 0.9 Re 0.1 B 2 maintained their hexagonal structure. This suggests that the thermal stability of the hexagonal OsB 2 was significantly improved with the addition of Re. Scanning electron microscopy (SEM) photographs show that all of the as-sintered samples exhibit a homogeneous microstructure with some pores and cracks formed throughout the samples with the relative density >90%. The measurements of micro-hardness, nano-hardness, and Young's modulus of the OsB 2 increased with Re addition, and these properties of the sample with 5 at.% addition of Re is higher than that with 10 at.% Re. K E Y W O R D Shardness, Os 1-x Re x B 2 , phase composition, thermal stability | INTRODUCTIONSuper-hard materials, due to their high hardness, high bulk modulus and high wear resistance, are widely used in machining, construction, aerospace, processing of new materials, automobile, and other fields.1 Conventional super-hard materials, e.g., diamond and c-BN, have been considered as the best option for fulfilling industrial machining requirements. 2-4 However, diamond cannot effectively machine steel or other ferrous metals due to the tendency to form iron carbide at elevated temperatures. c-BN would cut these ferrous materials, but it must be synthesized under high-pressure and high-temperature conditions, which makes it very expensive. To overcoming these shortcomings, it is highly desirable to develop new class of super-hard materials. 5During the past decade, efforts have been devoted to design and synthesis new super-hard materials for both scientific and practical application purposes. Recent searches on new super-hard materials mainly focus on two classes

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Novel high pressure hexagonal OsB2 by mechanochemistry

Cited by 34 publications

References 28 publications

Enthalpies of Formation of Transition Metal Diborides: A First Principles Study

Enthalpies of Formation of Transition Metal Diborides: A First Principles Study

Hexagonal OsB₂reduction upon heating in H₂containing environment

Effects of Re addition on phase stability and mechanical properties of hexagonal OsB₂

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Novel high pressure hexagonal OsB2 by mechanochemistry

Cited by 34 publications

References 28 publications

Enthalpies of Formation of Transition Metal Diborides: A First Principles Study

Enthalpies of Formation of Transition Metal Diborides: A First Principles Study

Hexagonal OsB2reduction upon heating in H2containing environment

Effects of Re addition on phase stability and mechanical properties of hexagonal OsB2

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Hexagonal OsB₂reduction upon heating in H₂containing environment

Effects of Re addition on phase stability and mechanical properties of hexagonal OsB₂