Catalytic Growth

The preparation of asymmetric nanosilica differs slightly from that of their symmetric counterparts, the main difference being an involvement of templates or anisotropic catalysts [28]. The addition of these materials initiates an asymmetric growth of nanomaterials, thus producing helical nano materials. In the template nanosiUca, a further treatment of as-made silica-like nanomaterials is required to convert them into real siUca nanomaterials. However, in the catalytic growth of heUcal nanomaterials such as nanocoils, no post-synthesis treatment is required. 

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Flafner J FI, Bronikowski M J, Azamian B R, Nikolaev P, Rinzier A G, Colbert A T, Smith K A and Smalley R E 1998 Catalytic growth of single-wall carbon nanotubes from metal particles Chem. Phys. Lett. 296 195... 

Guo, T., Nicolaev, P., Thess, A., Colbert, D.T., and Smalley, R.E. (1995a) Catalytic growth of single walled nanotubes by laser vaporization. Chem. Phys. Lett. 243, 49-54. 

Jose-Yacaman, M., Miki-Yoshida, M., Rendon, L., and Santiesteban, J.G. (1993) Catalytic growth of carbon microtubules with fullerene structure. Appl. Phys. Lett. 62, 657-659. 

Duan, X. Lieber, C. M. 2000. Laser-assisted catalytic growth of single crystal GaN nanowires. J. Am. Chem. Soc. 122 188-189. 

Tolbin AY, Nashchokin AV, Kepman AV, Dunaev AV, Malakho AP, Morozov VA, et al. Influence of conditions of catalytic growth of carbon nanostructures on mechanical properties of modified carbon fibers. Fiber Chemistry. 2012 Jul 44(2) 95-100. 

We also observed growth of SiNW from Au nanoparticles. In this case, H2 was also necessary. Although Au silicides can form at moderate temperatures and can also be reduced by hydrogen to Au nanoparticles and silane, the growth temperature for SiNW was still above 1000°C. It seems that silane was produced in both Au and Co catalytic growth cases. 

This leaves to only one possibility, namely that Si gets first into the gas phase to enable the catalytic growth of nanowires via Co or Co silicide nanoparticles. For silicon... 

Guo T, Nikolaev P, Thess A et al (1995) Catalytic growth of single-walled manotubes by laser vaporization. Chem Phys Lett 243 49-54... 

Figure 2. CNT formation in the catalytic growth process from the vapor phase (a) equipment used for the synthesis (h) formation of the CNT.

Chemical vapor deposition a monolith is exposed to volatiles, for example (fragments of), hydrocarbons which form a deposit on the surface. The most widely encountered underlying chemistry is free radical chemistry or catalytic growth. 

Si Laser-assisted catalytic growth, laser ablation, catalytic growth, HT synthesis, thermal evaporation SiO, CVD [141,142]... 

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