A Formation Mechanism for Catalytically Grown Helix-Shaped Graphite Nanotubes

Abstract

The concept of a spatial-velocity hodograph is introduced to describe quantitatively the extrusion of a carbon tubule from a catalytic particle. The conditions under which a continuous tubular surface can be generated are discussed in terms of this hodograph, the shape of which determines the geometry of the initial nanotube. The model is consistent with all observed tubular shapes and explains why the formation process induces stresses that may lead to "spontaneous" plastic deformation of the tubule. This result is due to the violation of the continuity condition, that is, to the mismatch between the extrusion velocity by the catalytic particle, required to generate a continuous tubular surface, and the rate of carbon deposition.

Morphological Evolution of (NH4)0.5V2O5·mH2O Fibers into Belts, Triangles, and Rings

“…12À17 Recently, nanorings/springs/helical structures for a number of inorganic materials such as CuO, 18 SnO 2 , 19 InGaN, 20 R-Ga 2 O 3 , 21 InP nanosprings, 22 PbSe, 23 BN, 24 AlN, 25 ZnO, 26À29 gold, 30 Zn 2 SnO 4 , 31 amorphous SiO 2 , 32 SiC nanosprings, 33 and carbon nanotube coils 34 have been reported. To the best of our knowledge, (NH 4 ) 0.5 V 2 O 5 3 mH 2 O ring/triangle and oval forms have not been reported so far.…”

The Electronic Structure of Nonpolyhex Carbon Nanotubes

“…The r number of atoms in the unit cell are 8,16,24,32, and 60 in order for the structures in Figures 2a, 3a, 4a, and 5a. For the structures in Figures 2 and 3 Figures 2c, 2d, 3c, and 3d the energy levels are presented only in the range (E LUMOmin , E HOMOmax ), and the white color corresponds to values out of this range.…”

“…1,2 The case of the nonpolyhex nanotubes is much more complicated. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] There is not yet an available general formula for the geometric and electronic structures of the nonpolyhex nanotubes when they contain pentagons and heptagons as well. 18,19 In ref 20 we presented a method for describing the geometrical structures of nonhexagonal nanotubes, nanocoils, and nanotori.…”

Growth of ZnSe Nanospirals with Bending Mediated by Lomer−Cottrell Sessile Dislocations through Varying Pressure

“…In the literature, coiled and zigzag structures have been extensively reported for several materials; [23][24][25][26][27][28][29][30][31][32][33][34] several mechanisms have also been proposed to interpret the formations. [24][25][26][27][29][30][31][32][33][34] Among the materials, ZnO has been most commonly studied.…”

“…[24][25][26][27][29][30][31][32][33][34] Among the materials, ZnO has been most commonly studied. Various coiled nanostructures induced by spontaneous polarization have been successfully obtained and explained by Wang's group.…”