Microstructural characterization of boron-rich boron carbide

Kelvin Y. Xie, Vladislav Domnich, Lukasz Farbaniec, Bin Chen, Kanak Kuwelkar, Luoning Ma, James W. McCauley, Richard A. Haber, K. T. Ramesh, Mingwei Chen, Kevin J. Hemker

Research output: Contribution to journalArticlepeer-review

42 Scopus citations

Abstract

Boron carbide has a wide range of solubility, but the effects of stoichiometry on its microstructure and mechanical response are not well understood. In this study, detailed microstructural characterization was carried out on three hot-pressed B-rich boron carbide samples. Lattice parameter measurements from XRD identified the compositions to be B4.2C, B5.6C and B7.6C. Local substitutional disorder was observed by Raman spectroscopy, particularly for more B-rich samples. Electron energy loss spectroscopy observations suggest that excess boron preferentially substitutes for carbon atoms in the B11C icosahedra; after which additional boron modifies the CBC chains. Moreover, the boron content has salient effects on boron carbide densification and microstructure. Improved densification was observed in the more B-rich samples (B5.6C and B7.6C), and there is a transition from few or no intragranular planar defects (B4.2C), to numerous stacking faults (B5.6C), to copious twins (B7.6C). Nanoindentation experiments revealed that the highest value for B4.2C is statistically larger than that for B5.6C or B7.6C, suggesting that the hardness of boron carbide is reduced by boron substitution.

Original languageEnglish (US)
Pages (from-to)202-214
Number of pages13
JournalActa Materialia
Volume136
DOIs
StatePublished - Sep 1 2017

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Metals and Alloys
  • Polymers and Plastics

Keywords

  • Boron carbide
  • Mechanical properties
  • Microstructure
  • Stoichiometry

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