Novel high pressure hexagonal OsB2 by mechanochemistry

    Authors

    Z. L. Xie; M. Graule; N. Orlovskaya; E. A. Payzant; D. A. Cullen;R. G. Blair

    Comments

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    Abbreviated Journal Title

    J. Solid State Chem.

    Keywords

    Osmium; Boron; Mechanochemistry; Ceramic; OSMIUM DIBORIDE; SUPERHARD MATERIAL; CRYSTAL STRUCTURE; RHENIUM; DIBORIDE; HARD MATERIAL; BORIDES; PHASE; RUB2; TRANSITION; IRIDIUM; Chemistry, Inorganic & Nuclear; Chemistry, Physical

    Abstract

    Hexagonal OsB2, a theoretically predicted high-pressure phase, has been synthesized for the first time by a mechanochemical method, i.e., high energy ball milling. X-ray diffraction indicated that formation of hexagonal OsB2 begins after 2.5 h of milling, and the reaction reaches equilibrium after 18 h of milling. Rietveld refinement of the powder data indicated that hexagonal OsB2 crystallizes in the P63/mmc space group (No. 194) with lattice parameters of a=2.916 angstrom and c=7.376 angstrom. Transmission electron microscopy confirmed the appearance of the hexagonal OsB2 phase after high energy ball milling, in situ X-ray diffraction experiments showed that the phase is stable from 225 degrees C to 1050 degrees C. The hexagonal OsB2 powder was annealed at 1050 degrees C for 6 days in vacua to improve crystallinity and remove strain induced during the mechanochemical synthesis. The structure partially converted to the orthorhombic phase (20 wt%) after fast current assisted sintering of hexagonal OsB2 at 1500 degrees C for 5 min. Mechanochemical approaches to the synthesis of hard boride materials allow new phases to be produced that cannot be prepared using conventional methods. (C) 2014 Elsevier Inc. All rights reserved.

    Journal Title

    Journal of Solid State Chemistry

    Volume

    215

    Publication Date

    1-1-2014

    Document Type

    Article

    Language

    English

    First Page

    16

    Last Page

    21

    WOS Identifier

    WOS:000336891300003

    ISSN

    0022-4596

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