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Title: Research Update: Direct conversion of h-BN into pure c-BN at ambient temperatures and pressures in air

We report a direct conversion of hexagonal boron nitride (h-BN) into pure cubic boron nitride (c-BN) by nanosecond laser melting at ambient temperatures and atmospheric pressure in air. According to the phase diagram, the transformation from h-BN into c-BN can occur only at high temperatures and pressures, as the hBN-cBN-Liquid triple point is at 3500 K/9.5 GPa. Using nanosecond laser melting, we have created super undercooled state and shifted this triple point to as low as 2800 K and atmospheric pressure. The rapid quenching from super undercooled state leads to formation of super undercooled BN (Q-BN). The c-BN phase is nucleated from Q-BN depending upon the time allowed for nucleation and growth.
Authors:
;  [1]
  1. Department of Materials Science and Engineering, Centennial Campus, North Carolina State University, Raleigh, North Carolina 27695-7907 (United States)
Publication Date:
OSTI Identifier:
22499247
Resource Type:
Journal Article
Resource Relation:
Journal Name: APL Materials; Journal Volume: 4; Journal Issue: 2; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AMBIENT TEMPERATURE; BORON NITRIDES; LIQUIDS; MELTING; NUCLEATION; PHASE DIAGRAMS; QUENCHING