The structures of BN columnar particles which were produced by heat-treating a turbostratic B-C-N compound were investigated by means of analytical transmission electron microscopy. The particles were shown to be helical cones with a well-defined apex, and a helical pitch which was usually equal to 1, or at most 2, layers. The results strongly suggested that the cones nucleated from squarish ring defects. The observations were consistent with the assumption that the creation of non B-N bonds, and hence odd-membered rings, was avoided in this material. This facilitated the understanding of the relative difficulty of BN cone edges with regard to joining via curved sheets.

Co-Produced Carbon and Boron Nitride Helical Cones and the Nucleation of Curved BN Sheets L.Bourgeois, Y.Bando, K.Kurashima, T.Sato: Philosophical Magazine A, 2000, 80[1], 129-42