The mm-tall sub-2-nm diameter SWCNT forests showed good quality (Raman G/D ratio of ∼40) and exceptionally high as-grown purity (outer specific surface area of 1215 m2/g; ideal: 1315 m2/g), which can be directly used without additional post-growth purification process to avoid any potential damage to the CNTs.
Multi-walled carbon nanotubes were purchased from Cheap Tubes Inc. (purity ~90%, outer diameter 10 30 nm, length 10 30 μm).
The yield of the nanotubes synthesis relative to the initial weight of the catalyst is in the order of 1200%, with 70% of the resulting material consisting of thin carbon nanotubes with less than 6 nm of outer diameter and carbon purity of greater than 90%.
Furthermore, these experiments showed a direct proportionality between the outer-SSA and absolute purity which led to a simple analytical model to use outer-SSA as a gauge for absolute purity analysis.
The outer-SSA and absolute purity for diverse forms of CNT forests to increased levels of carbonaceous impurities showed similar behavior and revealed a method to distinguish between CNTs and carbonaceous impurities.
The main materials used in this study are N-MWNTs (> 97% purity) with an outer mean diameter around 40 nm and a length over 10 μm.
SCNT of 95% purity with an outer diameter of 1 to 2 nm and lengths of 1 to 3 μm were purchased from Chengdu Organic Chemicals Co. Ltd., Chinese Academy of Sciences, (Chengdu, Sichuan, China).
Table 6 Multi-walled carbon nanotube features Specimen 1 Specimen 2 Specimen 3 Purity >95% >95%>95%% Outer diameter 10 to 20 nm 30 to 50 nm >50 nm Special surface area 200 m2/g 60 m2/g 40 m2/g Preparation method Chemical vapor deposition Chemical vapor deposition Chemical vapor deposition.
MWCNTs with outer diameter of 8 nm and purity above 95% were supplied by Chengdu Organic Chemicals Co., ltd China.
The CNTs synthesized at the corresponding conditions exhibited high quality with relatively small and mean outer diameter, less defect, and high purity.
