Ion Beam Analyses of Carbon Nanotubes

Abstract

The utility of ion beam analysis (IBA) techniques to quantitatively determine impurities in carbon nanotubes (CNTs) over a wide range of atomic numbers is demonstrated. Such techniques have not previously been used to monitor impurities and their effects in this unique material. Despite the difficulty in mounting the samples (which generally are formed into a powdery aggregate rather in a thin film), it is shown that reliable and accurate measurements of impurity concentrations can be achieved. Particle-induced X-ray emission (PIXE) and elastic recoil detection (ERD) analyses were used to characterize both metallic and very light (e.g., hydrogen) impurities in CNTs. This paper reports the first direct measurement of hydrogen in CNTs using an IBA technique. This is significant because CNTs are being actively investigated for hydrogen storage technology for energy applications.

Morphology, Microstructure, and Hydrogen Content of Carbon Nanostructures Obtained by PECVD at Various Temperatures

“…We exemplified the first report of Naab et al [22] of hydrogen content on commercially available single-, double-, and multiwalled nanotubes and carbon nanofibers and the report of Gohier et al [23] which found values between 4 and 8 at.% of hydrogen in multiwall carbon nanotubes by using high energy of 35 MeV Cl 7+ ion beam. The hydrogen content in CNW was reported before by Jain et al [24] in percentage of 3%-5% by SIMS and Nuclear Table 1 show values ranging from 4.5 to 10%, values obtained by integrating upon depth (areal density) the spectra shown in Figure 3.…”

Metal cations inserted in vanadium-oxide nanotubes

“…The experimental setup used has been described elsewhere [6]. For these measurements, the incident angle of the beam on each sample was perpendicular to the sample surface.…”

High Rate of Hydrogen Incorporation in Vertically Aligned Carbon Nanotubes during Initial Stages of Growth Quantified by Elastic Recoil Detection

“…18 Note that the application of the DataFurnace computation code allows us to report the absolute amount of hydrogen, in contrast to many previous publications, where the quantitative analysis was done using a Kapton standard, which by itself is known to be sensitive to ion beam induced damage. 15,17,18,23 In all of our experiments, the amount of hydrogen significantly decreased with increasing growth time and array height. The 60−70 μm arrays showed about 0.7 wt % of hydrogen, which is still considerably higher than previously reported values for MWCNTs.…”

“…For taller arrays (up to 500 μm) the hydrogen signal was almost constant (data not shown) within the accuracy of ERDA measurements, which is about 10%. 18 Previous attempts to characterize VA-MWCNTs, published by Gohier et al, 14 were based upon ERDA studies using highenergy, 35 MeV Cl ++ ion beam and very short, 180−380 nm, CNTs with and without nitrogen doping. The relative concentrations of nitrogen and hydrogen were calculated by means of ECPE (Element Concentration Profiles from ERDA) computer code.…”

“…Hydrogen plays a different but not less important role in the CVD growth of CNTs and carbon nanofibers (CNFs). − Its main role is that of catalyst reduction, or prevention of its oxidation and poisoning during growth, and to remove amorphous carbon. , Most of the CVD-based processes for CNT growth use a hydrogen-rich atmosphere and elevated temperatures, which might lead to hydrogen incorporation into the CNTs. The amount of retained hydrogen in CNTs is the subject of a small number of publications − that describe the direct measurement of residual hydrogen in CNTs. ERDA characterization of oriented multiwall CNTs (MWCNTs) has been reported only for short, submicron arrays .…”