NMR study of boron nitride nanotubes

11B nuclear magnetic resonance (NMR) spectra and the spin lattice relaxation times (T1) have been measured in boron nitride nanotubes (BNNTs), grown by chemical vapour deposition(CVD), as a function of temperature and applied magnetic field. From the analysis of the 11B NMR spectra and fitting of the T1 data, two components arising from the hexagonal and rhombohedral phases in the BNNTs were decomposed and identified. The fractions for each phase were also determined. The temperature dependence of 1/T1 reveals that the dominant relaxation mechanism for the rhombohedral phase is a Raman relaxation mechanism driven by lattice vibration.