Purification of Single-Wall carbon nanotubes by heat treatment and supercritical extraction

Abstract

Arc discharge is the most practical method for the synthesis of single wall carbon nanotubes (SWCNT). However, the production of SWCNT by this technique has low selectivity and yield, requiring further purification steps. This work is a study of purification of SWCNT by heat treatment in an inert atmosphere followed by supercritical fluid extraction. The raw arc discharge material was first heat-treated at 1250 °C under argon. The nanotubes were further submitted to an extraction process using supercritical CO 2 as solvent. A surfactant (tributylphosphate, TBP) and a chelating agent (hexafluoroacetylacetone, HFA) were used together to eliminate metallic impurities from the remaining arc discharge catalysts. Analysis of Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) showed an efficient removal of iron and cobalt (>80%). The purified nanotubes were further analyzed by TGA and Raman spectroscopy.

Fracture toughness and toughening mechanisms in a (ZrB2–SiC) composite reinforced with boron nitride nanotubes and boron nitride nanoplatelets

“…Tian et al [11] reported that the fracture toughness of a (ZrB 2 -SiC) composite increases by up to $15% at 2.0 wt.% CNTs. However, it is worth noting that the low starting oxidation temperature of CNTs ($400°C) [13] might degrade the mechanical properties of CNT/(ZrB 2 -SiC) composites at elevated temperatures.…”

Applications of Supercritical Fluids in Latin America: Past, Present and Future Trends

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Spherical indentation with multiple partial unloading for assessing the mechanical properties of ZrB2–SiC composites

“…Among various toughening agents, carbonaceous materials such as carbon nanotubes and graphene exhibit excellent mechanical properties, and they are promising nanofillers in ceramic matrix to improve fracture toughness. However, the low starting oxidation temperature of CNTs and graphene ( $ 400 1C) [10] might degrade the mechanical properties of (ZrB 2 -SiC) composites at elevated temperatures. By contrast with carbonaceous materials, boron nitride nanotubes (BNNTs), a structural analog of CNTs, not only possess excellent mechanical properties comparable to those of CNTs, but also exhibit higher starting oxidation temperature of BNNTs ($ 900 1C) [11], which is believed to guarantee less degradation of high-temperature performances of the BNNT/(ZrB 2 -SiC) composite.…”