Hexagonal OsB2: Sintering, microstructure and mechanical properties

Zhilin Xie, Mykola Lugovy, Nina Orlovskaya, Thomas Graule, Jakob Kuebler, Martin Mueller, Huili Gao, Miladin Radovic, David A. Cullen

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    20 Scopus citations

    Abstract

    The metastable high pressure ReB2-type hexagonal OsB2 bulk ceramics was produced by spark plasma sintering. The phase composition, microstructure, and mechanical behavior of the sintered OsB2 were studied by X-ray diffraction, optical microscopy, TEM, SEM, EDS, and nanoindentation. The produced ceramics was rather porous and contained a mixture of hexagonal (∼80 wt.%) and orthorhombic (∼20 wt.%) phases as identified by X-ray diffraction and EBSD analysis. Two boron-rich phases, which do not contain Os, were also identified by TEM and SEM/EDS analysis. Nanoindentation measurements yielded a hardness of 31 ± 9 GPa and Young's modulus of 574 ± 112 GPa, indicating that the material is rather hard and very stiff; however, it is very prone to crack formation and propagation, which is indicative of a very brittle nature of this material. Improvements in the sintering regime are required in order to produce dense, homogeneous and single phase hexagonal OsB2 bulk ceramics.

    Original languageEnglish
    Pages (from-to)168-178
    Number of pages11
    JournalJournal of Alloys and Compounds
    Volume634
    DOIs
    StatePublished - Jun 5 2015

    Funding

    This work was supported by NSF project DMR – 0748364 . The bulk of electron microscopy work was performed as part of a user project supported by ORNL’s Center for Nanophase Materials Sciences (CNMS) , which is a DOE Office of Science User Facility. M.M.’s and N.O.’s work at EPFL, which included nanoindentation experiments, was supported by the European Research Council under the European Union’s Seventh Framework Programme (FP/2007–2013)/ERC Advanced Grant Agreement No. 291085 and N.O.’s work at Empa was supported by the Swiss National Science Foundation, International Short Visit , IZK0Z2_154379 . The authors would also like to thank Prof. A. Mortensen, EPFL for his valuable suggestions and revisions of the manuscript.

    Keywords

    • Ceramic
    • Mechanical properties
    • Nanoindentation
    • Osmium diboride

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