Figure 3.

a A bright-field TEM image showing a segment of cylindrical BNNT. b SAED pattern taken from catalyst-containing knob on the tip of a cylindrical BNNT. c High magnification TEM image of the tubular part of a cylindrical BNNT. d EDX spectrum collected from a catalyst-containing knob on the tip of a cylindrical BNNT. e HRTEM image taken from the tube wall of a cylindrical BNNT, inset: the fast Fourier transform pattern of the corresponding HRTEM image. f EELS spectrum of tubular part of a cylindrical BNNT.