Comparative High Pressure Raman Study of Boron Nitride Nanotubes and   Hexagonal Boron Nitride
  High pressure Raman experiments on Boron Nitride multi-walled nanotubes show that the intensity of the vibrational mode at ~ 1367 cm-1 vanishes at ~ 12 GPa and it does not recover under decompression. In comparison, the high pressure Raman experiments on hexagonal Boron Nitride show a clear signature of a phase transition from hexagonal to wurtzite at ~ 13 GPa which is reversible on decompression. These results are contrasted with the pressure behavior of carbon nanotubes and graphite. 
Surajit Saha, D. V. S. Muthu, D. Golberg, C. Tang, C. Zhi, Y. Bando   and A. K. Sood