High-quality thin-multiwalled carbon nanotubes synthesized by Fe-Mo/MgO catalyst based on a sol-gel technique: Synthesis, characterization, and field emission

We synthesized thin-multiwalled carbon nanotubes (t-MWCNTs) using Fe-Mo/MgO catalyst by citrate precursor method based on a simple sol-gel technique. Synthesis of high-quality t-MWCNTs with uniform diameters was achieved in large-scale by catalytic decomposition of methane over Fe-Mo/MgO catalyst prepared under Ar-atmosphere. The produced t-MWCNTs had the outer diameters in the range of 4-8 nm, with a Gaussian average diameter of 6.6 ±0.1 nm and wall numbers in the range of of 4-7 graphenes. The product yield of the as-synthesized t-MWCNTs was over 450% relative to the used Fe-Mo/MgO catalyst, and TGA showed purity about 85%. The t-MWCNTs showed the low turn-on field about 1.24 V/μm, corresponding to the current density of 0.1 /μA/cm ², and the high emission current density of 10 mA/cm ² at the applied electric field of 2.6 V/μm. The t-MWCNTs indicate good emission stability without any fluctuation of emission current through a lifetime measurement for 20 h. It was confirmed that the field emission performance of t-MWCNTs was similar to DWCNTs and the field emission stability of t-MWCNTs was similar to MWCNTs.