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- Title
Thermodynamic Analysis of the V-Shaped Area of High Pressure and High Temperature in Cubic Boron Nitride Synthesis with Li<sub>3</sub>N as a Catalyst.
- Authors
Bin Xu; Mei-Zhe Lv; Hong-Mei Yang; Zhen-Xing Wen
- Abstract
The possibilities of different phase transitions to cBN with Li3N as catalyst at high temperature and high pressure (1600-2200 K, 4.8-6.0 GPa) are analyzed, in the framework of the second law of thermodynamics. The Gibbs free energy (ΔG) of three reactions which may happen in the Li3N-BN system: hBN + Li3N→Li3BN2, hBN→cBN, and Li3BN2→cBN + Li3N, is calculated, with the influence of high temperature and high pressure on volume included. We show that ΔG of hBN + Li3N→Li3BN2 and hBN→cBN are between -35~-10 KJ·mol-1 and -25~-19 KJ·mol-1, respectively. However, ΔG of Li3BN2→cBN + Li3N can be positive or negative. The area formed by the positive data is a V-shaped area, which covers the most part of the cBN growing V-shaped area. It confirms that Li3BN2 is stable in the P-T area of cBN synthesis, and cBN is probably transformed directly from hBN. Analysis suggests that Li3BN2 promotes the transition from hBN to cBN.
- Subjects
SECOND law of thermodynamics; LITHIUM nitrides; CHARGE exchange; ENTHALPY; ENTROPY; MURNAGHAN equation
- Publication
Entropy, 2014, Vol 16, Issue 2, p912
- ISSN
1099-4300
- Publication type
Article
- DOI
10.3390/e16020912