A Comparison of Purification Procedures for Multi-Walled Carbon Nanotubes Produced by Chemical Vapour Deposition

Abstract

A comparison of three different purification procedures for multi-walled carbon nanotubes (MWCNTs) produced by chemical vapour deposition (CVD) has been presented. The methods involved gas-phase oxidation by calcination, liquid-phase oxidation by H2O2, hydrothermal treatment and acid refluxing in HCl. Sample purity was documented with the Raman spectroscopy, Transmission electron microscopy (TEM), Scanning electron microscopy (SEM) and thermo gravimetric analysis (TGA). The Raman spectroscopy, SEM and TEM results showed that the liquid phase oxidation-acid refluxing route successfully eliminated most of the impurities without damaging the nanotube structure. TGA analysis showed in increase in density of MWCNTs with better oxidation resistance after purification and the metal content was reduced from 23.8 wt% to 5.4 wt%.

Nitrogen-doped carbon nanotubes as a metal catalyst support

“…Most methods produce CNTs with by-products such as amorphous carbon that necessitate additional purification steps (Nieto-Márquez et al 2008;Matlhoko et al 2009). The disadvantages of the arc discharge and laser ablation processes are (1) these processes are not very well controlled, nor are they continuous; (2) the removal of impurities with simple, cheap purification methods is difficult;…”

Mild hydrothermal treatment to prepare highly dispersed multi-walled carbon nanotubes

“…5-7 and Nos. [8][9][10][11] with different KPS concentration, KOH concentration and reaction time, respectively).…”

“…The poor chemical compatibility greatly hinders their solution phase manipulation and processability. Extensive researches have thus focused on the MWCNT modification to provide homogeneous dispersion of MWCNTs in various solutions [7][8][9][10][11][12][13], mainly in term of severe oxidation treatments (H 2 SO 4 [10], HNO 3 [11,12] or KMnO 4 [13]) that allow the introduction of carboxyl and hydroxyl groups to MWCNT surface. In general, these approaches unavoidably break carbon nanotubes into short fragments and even change their inherent morphology owing to oxidative conditions.…”

Nanorészecske-szén nanocső nanokompozitok előállítása, jellemzése és katalitikus tulajdonságainak vizsgálata

“…A "melléktermékek" általánosan három csoportra oszthatók; (i) a katalizátor (melyet megtalálunk mind a lézeres elpárologtatás termékében, mind a katalitikusan előállított minta esetében), (ii) az amorf szén (mely mellett más szénformák is fellelhetők, például szénszálak, grafitos részecskék, egyéb szén nanoszerkezetek) mely ugyancsak minden szintézis módszernél keletkezik kisebb vagy nagyobb mennyiségekben, valamint (iii) a katalitikus szintéziseknél a hordozó. Bizonyos tisztítási eljárások egy lépésben próbálják meg a nemkívánatos anyagok eltávolítását, mások első lépésben a katalizátort és a hordozót, majd a második lépésben a nem nanocső jellegű szenet távolítják el 69,70,71,72 .…”