The role of multiple polytypes in determining the catastrophic failure of boron carbide at high shock velocities

Giovanni Fanchini, James W. McCauley, Dale E. Niesz, Manish Chhowalla

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)

Abstract

The absence of a plastic phase in boron carbide and its failure at shock impact velocities just above the Hugoniot elastic limit (HEL) has been a puzzle for a long time. In the present work, using self-consistent field density functional simulations we are able to account for many experimental observations by noticing that several boron carbide polytypes [(B 11C)C2B, (B12)C3, etc ...] coexist without significant lattice distortions. Our analysis also indicates that above a threshold pressure all the candidate microstructures are less stable than a phase involving segregated boron (B12) and amorphous carbon (a-C) but the energetic barrier between boron carbide and B12 + 3C, is by far lower for the B12(CCC) microstructure, requiring the lowest atomic displacement for a transformation B4C→3B+a-C, occurring at pressures of 6 GPa ≈ P(HEL). For such a configuration, segregation of free carbon occurs in layers orthogonal to the (113) lattice directions, in excellent agreement with recent transmission electron microscopy (TEM) analysis.

Original languageEnglish
Title of host publicationMechanisms of Mechanical Deformation in Brittle Materials
Pages37-42
Number of pages6
Publication statusPublished - Dec 1 2005
Event2005 MRS Fall Meeting - Boston, MA, United States
Duration: Nov 28 2005Dec 2 2005

Publication series

NameMaterials Research Society Symposium Proceedings
Volume904
ISSN (Print)0272-9172

Other

Other2005 MRS Fall Meeting
CountryUnited States
CityBoston, MA
Period11/28/0512/2/05

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ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

Fanchini, G., McCauley, J. W., Niesz, D. E., & Chhowalla, M. (2005). The role of multiple polytypes in determining the catastrophic failure of boron carbide at high shock velocities. In Mechanisms of Mechanical Deformation in Brittle Materials (pp. 37-42). (Materials Research Society Symposium Proceedings; Vol. 904).