Multi-walled boron nitride nanotubes composed of diverse cross-section and helix type shells

High-resolution transmission electron microscopy (HRTEM) and electron diffraction analysis were performed on pure multi-walled novel type boron nitride nanotubes (BNNTs) by using a field-emission high-resolution 300 kV transmission electron microscope JEM-3100FEF (Omega filter). In contrast to commonly observed monochiral multi-walled BNNTs, the present tubular shells within every individual BNNT (up to ～50 shells) revealed the whole range of helixes, i.e., from zig-zag to arm-chair. This being paired with the wide variations in cross-sectional tubular shapes, i.e., from a faceted polygon to a cylinder, results in complex overall tubular structures. The BN atomic lattice fringe separations, down to 1.25 Å, on most symmetrical arm-chair (d_10-10=1.25 Å) and zig-zag (d_11-20=2.15 Å) tubular wall fragments within the same multi-walled BN nanotubes were ultimately achieved during HRTEM.