Table 1.

Reaction parameters for CNT yield optimization using AD method

Metal catalyst	Atmosphere	Pressure (Torr)	Current (A)	Major observation	Ref.
SWCNT
Fe	CH4 Ar	10 and 40	200	• SWCNTs of 1 nm in diameter are obtained	[86]
Co, Fe, Ni	He	100–500	95–105	• Co helped to produce SWCNTs with uniform diameter of 1.2 nm	[87]
Ni, Pd, Pt	He	550	70	• Ni-filled anode stimulates SWCNT growth	[167]
Ni–Co, Co–Y, Ni–Y	He	660	100	• SWCNT bundle filament is secured. It consists of smaller aligned SWCNTs self-organized into bundle-like crystallites with diameters ranging from 5 to 20 nm	[88]
Y–Ni	He	100–700	40–100	• Only 40% of SWCNTs with diameter 1.3 nm are realized	[168]
Fe	H2–Ar	200–520	28–34 V	• Highly crystalline SWCNTs with diameter 10–30 nm are obtained	[169]
Co-Ni	He	500	80–100	• SWCNTs are synthesized with uniform diameter 1.7 nm • SWCNT production rate 7 g/h and the purity 70%	[170]
Ni, Y	Co, He	225	100	• SWCNTs with small diameter 1.66 nm are preferentially etched with the increase of Co concentration	[171]
Fe–Mo	Ar–H2	225	90	• SWCNTs with selected diameter distributions are secured	[172]
Fe, Co, Ni	He	300	–	• SWCNTs are obtained with a number of carbonaceous and embedded catalyst particles on surface	[110]
Fe	N2, He, Ar	300–375	60–80	• High-quality SWCNT, DWCNTs, and TWCNT are synthesized with different diameters • He gas supported SWCNT production • Ar gas responsible for TWCNT formation • N2 gas encouraged DWCNT production	[101]
Fe, W	H2, Ar	200	70–120	• SWCNTs are synthesized with high yield • Fe–W catalysts made SWCNT smaller than those using Fe catalyst alone	[173]
Ni/Y	Ar	12 kPa	90	• SWCNTs of diameter 1.29–1.62 nm are synthesized with higher oxidization temperature	[174]
Fe, Co, Ni, and FeS	H2	240	120	• De-bundled SWCNTs with diameter 3 nm are synthesized	[175]
FWCNT
Ni, Co, F,S	Ar, H2	350	75–80	• DWCNTs with outer diameter (1.9–5.0 nm) and inner tube diameters (1.1–4.2 nm) are obtained	[176]
Y–Ni/Co	Ar	–	40–60	• High-quality DWCNTs with inner and outer diameters 0.8–1.2 and 1.6–2.0 nm, respectively, are realized	[177]
Ni, Co, FeS, NiS, CoS, FeS, Sn	He	600	180	• High-quality DWCNTs with diameter (2–7 nm) super bundles are selectively grown	[178]
FeS KCl	H2	350	70	• DWCNTs with perfect lattice structure are synthesized with high yield	[179]
Ni(HCO2)2·2H2O	H2	240	120–300	• 65% of DWCNT are obtained within 10 min with narrow diameter distribution (outer 1.98–3.47 nm and inner 1.32–2.81 nm)	[180]
Ni/Co/Fe, Ye/La	Ar	760	50	• Highly pure DWCNT (95%) are achieved	[181]
Fe, S	Air	0.75–135	90	• FWCNT are effectively synthesized with diameter 1.6–6 nm	[182]
MWCNT
–	He	500	18	• MWCNT with diameter (5–30 nm) and length of several micrometers are secured	[85]
–	CH4	50	20	• Thick MWCNTs are synthesized	[113]
–	H2	60	50	• Fine and long MWCNTs are realized	[183]
Nd–Fe–B magnets	He, Ar, O2, N2, Air	750	~4.0 × 1011 A/m2	• Obtained MWCNTs are highly pure (>95%) • MWCNT purities are ~97% in (air), ~96% (Ar), ~40% (He), ~33% (N2), and ~26% (O2) gases	[184]
–	Liquid N2	–	80	• 70% of MWCNT with diameter (20–50 nm) and a few μm in length is obtained	[119]
C8H10 C10H10F	–	500	10–70	• Both (SWCNTs and MWCNTs) are obtained	[185]
Co, S, Pt	H2	300	100	• Environmental temperature showed a significant effect on the formation of MWCNTs as well as the diameter of the tubes	[186]
–	He Air	500	150	• Highly graphitic MWCNT (yield 60%) in He atmp. and traces of DWCNT are secured	[144]
Nd-Fe-B magnet, Co metal	Water	–	50	• Purity and quality of obtained MWCNT are both improved markedly • Co helped to get a cylinder-like CNT structure	[187]
Hydrocarbon compounds as precursors	He	300–600	30–90	• Thick MWCNTs are obtained • Aromatic hydrocarbons, including pyrene and xylene, are suggested to not only act as precursors but also enhance the growth rate of MWCNT	[188]
–	Air	60	80	• Fine and long MWCNTs are obtained free from carbon nanoparticle and graphite platelet	[189]