Abstract
The relative stability and melting of cubic boron nitride (c-BN) nanoparticles of varying shapes and sizes are studied using classical molecular dynamics (MD) simulation. Focusing on the melting of octahedral c-BN nanoparticles, which consist solely of the most stable {111} facets, decomposition is observed to occur during melting, along with the formation of phase segregated boron clusters inside the c-BN nanoparticles, concurrent with vaporization of surface nitrogen atoms. To assess this MD prediction, a laser-heating experiment of c-BN powders is conducted, manifesting boron clusters for the post-treated powders. A general analysis of the geometrical and surface dependence of the nanoparticle ground-state energy using a Stillinger-Weber potential determines the relative stability of cube-shaped, octahedral, cuboctahedral, and truncated-octahedral c-BN nanoparticles. This stability is further examined using transient MD simulations of the melting behavior of the differently shaped nanoparticles, providing insights and revealing the key roles played by corner and edge initiated disorder as well as surface reconstruction from {100} to the more stable {111} facets in the melting process. Finally, the size dependence of the melting point of octahedral c-BN nanoparticles is investigated, showing the well-known qualitative trend of depression of melting temperature with decreasing size, albeit with different quantitative behavior from that predicted by existing analytical models.
Original language | English (US) |
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Pages (from-to) | 10563-10572 |
Number of pages | 10 |
Journal | ACS Nano |
Volume | 10 |
Issue number | 11 |
DOIs | |
State | Published - Nov 22 2016 |
All Science Journal Classification (ASJC) codes
- General Materials Science
- General Engineering
- General Physics and Astronomy
Keywords
- cubic boron nitride
- faceting
- geometric stability
- melting
- nanoclusters
- phase segregation
- size effect
- surface reconstruction