Fig. 4: Solution-spun fibers of BNNTs.

a Photograph of typical segment of fiber made from highly purified BNNTs taped to a benchtop under tension. b Scanning electron microscopy (SEM) showing a 27 μm diameter fiber with wrinkled and smooth areas of the fiber skin. c SEM showing mild alignment of BNNTs along the wrinkle contours. d SEM of a smooth area of the fiber surface showing strong BNNT alignment along the fiber axis. e Wide-angle X-ray scattering of BNNT fiber (black dots) plotted against azimuthal angle shows two peaks from the fiber fit with a Gaussian curve (blue line) with full-width at half maximum (FWHM) of 42°. f Raman spectra of BNNT fiber with V0°, V30°, V60°, V90°, V120°, V150°, and V180° polarizer/analyzer modes. Laser excitation was given by a 785 nm laser. A sharp peak at ∼1370 cm⁻¹ is characteristic of BNNTs.