Computational predictions and microwave plasma synthesis of superhard boron-carbon materials

Paul A. Baker, Shane A. Catledge, Sumner B. Harris, Kathryn J. Ham, Wei Chih Chen, Cheng Chien Chen, Yogesh K. Vohra

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Superhard boron-carbon materials are of prime interest due to their non-oxidizing properties at high temperatures compared to diamond-based materials and their non-reactivity with ferrous metals under extreme conditions. In this work, evolutionary algorithms combined with density functional theory have been utilized to predict stable structures and properties for the boron-carbon system, including the elusive superhard BC5 compound. We report on the microwave plasma chemical vapor deposition on a silicon substrate of a series of composite materials containing amorphous boron-doped graphitic carbon, boron-doped diamond, and a cubic hard-phase with a boron-content as high as 7.7 at%. The nanoindentation hardness of these composite materials can be tailored from 8 GPa to as high as 62 GPa depending on the growth conditions. These materials have been characterized by electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, and nanoindentation hardness, and the experimental results are compared with theoretical predictions. Our studies show that a significant amount of boron up to 7.7 at% can be accommodated in the cubic phase of diamond and its phonon modes and mechanical properties can be accurately modeled by theory. This cubic hard-phase can be incorporated into amorphous boron-carbon matrices to yield superhard materials with tunable hardness values.

Original languageEnglish
Article number1279
JournalMaterials
Volume11
Issue number8
DOIs
StatePublished - Jul 25 2018
Externally publishedYes

Funding

This material is based upon work supported by the National Science Foundation (NSF) EPSCoR RII-Track-1 Cooperative Agreement OIA-1655280. We also acknowledge support from the NSF Major Research Instrumentation (MRI) Grant No. DMR-1725016. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

Keywords

  • Ab initio calculations
  • Boron-carbon compound
  • Chemical vapor deposition
  • Superhard materials

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