Syntactic coalescence of WS2 nanotubes

WS2 nanoropes merged from nanotube coalescence present a new case of inorganic fiber composites with several nanotubes grown side by side up to a few millimeters in length. The extremities of external and inner spirally rolled-up molecular layer building the tubes are at the origin of the nanotube nucleation leading to the syntactic growth of nanotubes. The model of undulation of thin crystal flakes based on stacking mismatch is discussed. The nanoropes grow also by self-assembly or by coalescence of single tubes at low angles of incidence. An attractive long-range force leading to the nanotube approach is proposed.