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Title: Hexagonal OsB2: Sintering, microstructure and mechanical properties

In this study, 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; but, 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.
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [4] ;  [5] ;  [6] ;  [6] ;  [7]
  1. Univ. of Central Florida, Orlando, FL (United States)
  2. Univ. of Central Florida, Orlando, FL (United States); Institute for Problems of Materials Science, Kyiv (Ukraine)
  3. Laboratory for High Performance Ceramics, Dubendorf (Switzerland)
  4. Laboratory for High Performance Ceramics, Dubendorf (Switzerland)
  5. Laboratory of Mechanical Metallurgy, EPFL, Lausanne (Switzerland)
  6. Texas A & M Univ., College Station, TX (United States)
  7. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
OSTI Identifier:
1265283
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Journal of Alloys and Compounds
Additional Journal Information:
Journal Volume: 634; Journal ID: ISSN 0925-8388
Publisher:
Elsevier
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE Osmium diboride; Mechanical properties; Nanoindentation; Ceramic