Synthesis and High Thermal Stability of Double-Walled Carbon Nanotubes Using Nickel Formate Dihydrate as Catalyst Precursor

Abstract

Nickel formate dihydrate is demonstrated to be an effective catalyst precursor for selectively synthesizing double-walled carbon nanotubes (DWNTs) with high thermal stability by using a hydrogen arc discharge technique. High-resolution transmission electron microscopy (HRTEM) observations show that the as-synthesized DWNTs are of high quality with good structural integrity and narrow diameter distribution (1.98−3.47 nm and 1.32−2.81 nm, respectively, for the outer and inner diameter). Thermogravimetric analysis (TGA) in air indicates that the DWNTs have excellent oxidation resistance up to ∼800 °C, approaching to that of graphitized multiwalled carbon nanotubes and higher than that of DWNTs prepared by other routes or methods. Moreover, Raman analysis and HRTEM observations reveal that these DWNTs can keep good structural stability and other carbon species are removed after oxidation at 650 °C in air flow. The formation of DWNTs with high thermal stability is attributed to the cleaning effect of active radicals such as hydrogen and oxygen originated from the decomposition of nickel formate dihydrate and the in situ defect-healing effect induced by high arc current in the arc growth process. This approach opens various application possibilities for DWNTs with high thermal stability to be used in high-temperature composites, nanoelectronic devices, and electron filed emitters operating at high currents, etc.