Stability of Ti–B–N solid solutions and the formation of nc-TiN/a-BN nanocomposites studied by combined ab initio and thermodynamic calculations
✍ Scribed by R.F. Zhang; S.H. Sheng; S. Veprek
- Publisher
- Elsevier Science
- Year
- 2008
- Tongue
- English
- Weight
- 725 KB
- Volume
- 56
- Category
- Article
- ISSN
- 1359-6454
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✦ Synopsis
The ab initio density functional theory (DFT) has been used to calculate the properties of binary face-centered cubic (fcc)(NaCl)-and fcc (ZnS)-TiN and BN, hexagonal-close-packed (hcp)-TiB 2 , and ternary Ti 1Àx B x N and TiB x N 1Àx solution phases. In order to study the stability of the ternary fcc(NaCl)-Ti 1Àx B x N and of the nitrogen-deficient fcc(NaCl)-TiB x N 1Àx solution, their mixing energies and the phase stability diagrams were constructed over the entire range of compositions. The results show that the fcc(NaCl)-Ti 1Àx B x N should decompose by spinodal mechanism, whereas the substoichiometric fcc(NaCl)-TiB x N 1Àx should decompose via nucleation and growth. The relatively large lattice mismatch between the fcc(NaCl)-TiN and fcc(NaCl)-BN, and the high lattice instability of the fcc(NaCl)-BN with respect to fcc(ZnS)-BN, suggests that the spinodal decomposition will, in the later stages, be accompanied by transformation of the fcc(NaCl)-BN to a more stable phase.