Mechanism of Formation of Filaments, Nanotubes, and whiskers solution(x/xo), and with increasing work of adhesion(Wad). Note that this criterion gives us a minimal value for the radius of the carbon nucleus Nuclei with smaller radii are not stable, but nuclei with larger sizes can continue to row. The comparison of calculated data of the size of carbon nucleus critical radii with the smallest size of observed carbon nanotubes and carbon filaments demonstrate reasonable coincidence of calculated and experimental data (1, 11). It was shown that the increase of reaction temperature leads to the formation of smaller nuclei, and finally to the formation of SWNTs. The usage of metals characterized by a higher metal-carbon energy bond leads to nanotubes with smaller diameters. SWNT growth is likely to proceed on liquid metal particles. Elements that decrease the melting point of the catalyst carbon mixture and do not form stable compounds with carbon at the reaction temperature also promote the formation of SWNTs. The values of rert (30-40 A)calculated for SiC nucleus according to Eq (3) are also very close to the smallest size of experimentally observed whiskers'tips. So Fig. 3 demonstrates the tip of Sic whisker, which was produced with iron catalyst at 1470K, with the smallest flat part close to 65a 65 2,51 风 Figure 3. HR TEM image of the tip of SiC whisker(see insert) produced on Fe catalysts at 1470 K using SiO2 and carbon soot as precursors in hydrogen atmosphere. One can see 3C polytype of SiC on end of the tip following numerous stacking fault dislocation.solution (x/x0)i, and with increasing work of adhesion (Wad). Note that this criterion gives us a minimal value for the radius of the carbon nucleus. Nuclei with smaller radii are not stable, but nuclei with larger sizes can continue to grow. The comparison of calculated data of the size of carbon nucleus critical radii with the smallest size of observed carbon nanotubes and carbon filaments demonstrate reasonable coincidence of calculated and experimental data (1, 11). It was shown that the increase of reaction temperature leads to the formation of smaller nuclei, and finally to the formation of SWNTs. The usage of metals characterized by a higher metal–carbon energy bond leads to nanotubes with smaller diameters. SWNT growth is likely to proceed on liquid metal particles. Elements that decrease the melting point of the catalyst– carbon mixture and do not form stable compounds with carbon at the reaction temperature also promote the formation of SWNTs. The values of rcrit (30 – 40 A˚ ) calculated for SiC nucleus according to Eq. (3) are also very close to the smallest size of experimentally observed whiskers’ tips. So Fig. 3 demonstrates the tip of SiC whisker, which was produced with iron catalyst at 1470 K, with the smallest flat part close to 65 A˚ . Figure 3. HR TEM image of the tip of SiC whisker (see insert) produced on Fe catalysts at 1470 K using SiO2 and carbon soot as precursors in hydrogen atmosphere. One can see 3C polytype of SiC on end of the tip following numerous stacking fault dislocation. Mechanism of Formation of Filaments, Nanotubes, and Whiskers 127