# A Review of Double-Walled and Triple-Walled Carbon Nanotube Synthesis and Applications
## 2 Synthesis and Characterization of DWNTs
### The Catalytic Chemical Vapor Deposition Method
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Catalyst/Precourse/Promoter** & **Carbon Source/Cartier/Atmosphere** & **Inner Tube / \& **t, (nm)** & **Outer Tube / \& **d\({}_{2}\) (nm)** & **S Selectivity** & **Method** \\ \hline Fe-Co/MgO [88] & CH\({}_{4}\)/N\({}_{2}\) & 0.6–1.2 & 13-2.0 & - & Supporting (powder) \\ Fe-Co/MgO [88] & CH\({}_{4}\)/He/Ar & - & 17-3.0 & - & Supporting (powder) \\ Fe-Co/MgO [88] & CH\({}_{4}\)/He/N\({}_{5}\) & - & 20-4.0 & - & Supporting (powder) \\ Fe-Co/MgO [88] & CH\({}_{4}\)/He & - & - & - & Supporting (powder) \\ Mg-Fe/MgO [88] & CH\({}_{4}\)/He & - & - & Supporting (powder) \\ Mn-Fe/Co [89] & CH\({}_{4}\)/He & 22 & - & 41\% & Supporting (powder) \\ Mn-Fe/MgO [90] & CH\({}_{4}\)/He & - & 3 & 48\% & Supporting (powder) \\ Fe-Co/Agreements Slide [91] & CH\({}_{4}\)/He & - & 43 & 50\% & Supporting (powder) \\ Mn-Fe/Co [92] & CH\({}_{4}\)/He & 1.7 & 27 & 51\% & Supporting (powder) \\ Fe/Au/MgO [93] & CH\({}_{4}\) & - & 10-4.0 & 58\% & Supporting (powder) \\ Co/Mo/MgO [94] & EtOH & 0.6–1.3 & 13-2.0 & 70\% & Supporting (powder) \\ Fe/Au/MgO [95] & CH\({}_{4}\)/He & - & 20-30.0 & 370\% & Supporting (powder) \\ Fe-Co/Agreements Slide [97] & EtOH/Ar & - & -2.0 & 70\%-80\% & Supporting (powder) \\ Fe-Co/Agreements Slide [98] & CH\({}_{4}\)/Ar & - & 20-6.0 & 80\% & Supporting (powder) \\ Fe-Co/Agreements Slide [99] & EtOH/Ar & - & 15-5.4 & 80\% & Supporting (powder) \\ Fe-Co/Agreements Slide [99] & EtOH/Ar & 0.91 & 168 & 82\% & Supporting (powder) \\ Fe (100)/MgO [90] & CH\({}_{4}\)/Ar & 1.42 & 219 & 88\% & Supporting (powder) \\ Fe-Co/MgO [90] & CH\({}_{4}\)/Ar & - & 20.5 & 87\% & Supporting (powder) \\ Fe-Co/MgO [91] & CH\({}_{4}\)/Fe/Ag & - & 20.5 & 87\% & Supporting (powder) \\ Fe-Co/MgO [91] & CH\({}_{4}\)/Fe/Ag & - & 0.75–1.8 & 15-2.6 & 50\% & Supporting (powder) \\ Mn-Fe/MgO [92] & CH\({}_{4}\)/Ar & 0.9 & 16 & 95\% & Supporting (powder) \\ Fe-Mo/MgO [93] & CH\({}_{4}\)/Fe/Ag & - & 20 & 95\% & Supporting (powder) \\ Fe-Co/MgO [94] & HC\({}_{4}\)/He/Ar & 0.6–1.5 & 13-2.2 & 100\% & Supporting (powder) \\ Fe (1 mm/Al)/O [90] & NO\({}_{3}\)/Si [90] & CH\({}_{4}\)/He & 10-2.0 & 20-3.0 & - & Supporting (bustable) \\ Fe-Co/MgO [95] & CH\({}_{4}\)/He/Ar & - & 30-50.0 & 70\% & Supporting (bustable) \\ Fe (1 mm/Al)/O [93] & CH\({}_{4}\)/He/Ar & - & 37 & 79\% & Supporting (bustable) \\ Fe (1 mm/Al)/O [93] & CH\({}_{4}\)/He/Ar & - & 4.5 & 80\% & Supporting (bustable) \\ Fe (1 mm/Al)/O [93] & CH\({}_{4}\)/He/Ar & - & 3.75 & 81\% & Supporting (bustable) \\ Fe (1 mm/Al)/O [93]/Si [93] & CH\({}_{4}\)/He & 3.6 & 81\% & Supporting (bustable) \\ Fe (1 mm/Al)/O [93]/Si/Si [93] & CH\({}_{4}\)/He & 3.6 & 84\% & Supporting (bustable) \\ Fe (1 mm/Al)/O [93]/Si/Si [93] & CH\({}_{4}\)/He & - & 3.75 & 85\% & Supporting (bustable) \\ Fe (100)/AlO/O [93]/Si/Si [93] & CH\({}_{4}\)/He & - & 3.75 & 87\% & Supporting (bustable) \\ Fe-Co/MgO [94] & CH\({}_{4}\)/He & 0.40–2.19 & 10-28.9 & - & Routing \\ Fe-Co/MgO [94] & CH\({}_{4}\)/Ar & - & 2.0 & - & Routing \\ Fe-Co/MgO [95] & Kylene/He/Ar & 2.0 & - & 80\% & Routing \\ Fe-Co/MgO [96] & EtOH/Fe/Ge/H & - & - & - & Routing \\ Fe-Co/MgO [97] & EtOH/Fe/Ge/H & - & - & - & Routing \\ Fe-Co/MgO [98] & EtOH/Fe & - & - & - & Routing \\ Fe-Co/MgO [99] & EtOH/H & - & - & - & Routing \\ Fe-Co/MgO [99] & Actone/Ar & 2.1 & 2.8 & 90\% & Routing \\ Fe-Co/MgO [99] & CH\({}_{4}\)/He & 10-13.3 & 17-2.0 & >90\% & Routing \\ \hline \end{tabular}
\end{table} 
Table 1: Synthesis methods for the selective growth of double-walled carbon nanotubes (DWNTs).