New phases of sp2-bonded boron nitride: the 12R and 24R polytypes

sp2-Bonded polytypes of graphite-like boron nitride are evidenced in the approximately twin-related bicrystal-like BN nanofibres synthesized by a high-temperature substitution reaction between carbon nanofibres and boron oxides in N2 atmosphere; the material shows a main 12R phase of A'ABC/C'CAB/B'BCA packing and a minor 24R phase with an A'ABC/BB'C'A'/C'CAB/ ... packing sequence.