Determination of Carbon Nanotube Density by Gradient Sedimentation

Abstract

Density gradient centrifugation is a high-resolution technique for the separation and characterization of large molecules and stable complexes. We have analyzed various nanotube structures by preparative centrifugation in sodium metatungstate-water solutions. Bundled, isolated and acid-treated single-walled nanotubes (SWNTs) and multiwall nanotubes (MWNTs) formed sharp bands at well-defined densities. The structure of the material in each band was confirmed by transmission electron microscopy and Raman spectroscopy. Our data suggest respective densities of 1.87, 2.13, 1.74, and 2.1 g/cm(3) for bundled, isolated, and acid-treated SWNTs and MWNTs. These measured results compare well with their calculated densities.

Single‐Walled Carbon Nanotube Networks: The Influence of Individual Tube–Tube Contacts on the Large‐Scale Conductivity of Polymer Composites

“…[23] The density of the 2 μm thick films was determined by weighing a total of six samples with the dimensions: 1 cm × 1 cm × 2 μm. The calculated film density of 1.1 ± 0.1* g cm −3 (*standard deviation of the population) is somewhat lower than the measured densities of SWCNT bundles of 1.2-1.8 g cm −3 , [25,26] and approximately three times lower than the calculated densities of individual SWCNTs of 3.1-3.5 g cm −3 . [26,27] Using a density of 1.1 g cm −3 , the SWCNTs occupy 61% of the film volume.…”

Charge transfer and storage in nanostructures

“…The rationale is the presence of abundant equivalent porosity and low packing density (e.g., typically <1 cm 3 /g, for activated carbon [110]), in the nanostructure arrangement, which may lead to overestimates of the energy density. The consequence is a conversion factor/ratio between the mass based energy density and the volumetric energy density of less than 1, e.g., considering the placement of 10 nm diameter multiwalled CNTs (with intrinsic density [111] of $2.1 g/ cm 3 ) and 0.1 mm in height with a spacing of $20 nm on a 1 cm  1 cm substrates results in a packing density of $0.7 g/cm 3 -then an energy density of 10 Wh/kg would translate to a volumetric energy density of 7 Wh/l. Smaller CNT spacings would be needed, say, <15 nm as related to the above example to achieve a conversion factor of $1.…”

In-plane mechanical properties of carbon nanotube films fabricated by floating catalyst chemical vapor decomposition

“…3f. To determine the density of individual CNT (q CNT ), the weight was calculated by assuming the MWCNT to be a hollow cylinder with an 11 nm outer diameter, a 5 nm inner diameter, and a wall density of 2.1 g cm -3 , which equals to the density of graphite [26]. The inset picture in Fig.…”