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Computational Predictions and Microwave Plasma Synthesis of Superhard Boron-Carbon Materials

Department of Physics, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA
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Materials 2018, 11(8), 1279; https://doi.org/10.3390/ma11081279
Received: 22 June 2018 / Revised: 18 July 2018 / Accepted: 23 July 2018 / Published: 25 July 2018
(This article belongs to the Section Thin Films)
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. View Full-Text
Keywords: boron-carbon compound; superhard materials; ab initio calculations; chemical vapor deposition boron-carbon compound; superhard materials; ab initio calculations; chemical vapor deposition
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Baker, P.A.; Catledge, S.A.; Harris, S.B.; Ham, K.J.; Chen, W.-C.; Chen, C.-C.; Vohra, Y.K. Computational Predictions and Microwave Plasma Synthesis of Superhard Boron-Carbon Materials. Materials 2018, 11, 1279.

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