Abstract Submitted to the    NANOTUBE'04 Conference:

Double walled carbon nanotubes (DWNTs) exhibit electronic properties as single-walled nanotubes (SWNTs) and structural stability as multi-walled nanotubes (MWNTs). They are promising materials for the long-term stable field emitters with low threshold voltages. Selective synthesis of DWNTs has been achieved by catalytic chemical vapor deposition of alcohol over Fe/Co loaded mesoporous silica. Several mesoporous silica materials with desired pore diameter, pore wall thickness and morphology have been investigated for the DWNT growth. The diameter distribution and yield of the DWNT are found to depend on the reaction temperature, pore size and thermal stability of the support material. When high temperature stable mesoporous silica is used as a catalyst support, about 80% of nanotubes synthesized at 900 ^oC are found to be DWNTs. These DWNTs have been characterized using HRTEM and Raman spectroscopy. The outer diameter of DWNTs is found to be in the range of 1.5–5.4 nm with a ‘d ’ spacing of 0.38(+/-)0.02 nm between inner and outer layers which is much larger than those of MWNTs.