Nanotube products

Rosseter is producing raw deposits of two main nanotube products,

Ros1 - short Multi Wall Nano Tubes (sh‑MWNTs) and
Ros2 - “split” MWNTs, sp‑MWNTs

In TEM pictures the nanotube deposits appear as mixtures of the sh‑MWNTs and carbon polyhedral nanoparticles, with admixtures of different graphitic carbons and short Single Wall Nano Tubes (sh‑SWNTs).

The rest of Rosseter's products (Ros3-Ros5) are by‑products of the two main processes. The by‑products contain few nanotubes and are mostly composed of different forms of disordered graphite (DOG) and Graphite Nano Fibers (GNFs).

Ros1, as produced

Ros1 is produced in our main process with no use of catalysts.
Most part of sh‑MWNTs in Ros1 seem to be nested (Russian doll‑like structure) MWNTs having semi‑spherical and conical-like (or faceted) caps [see HR-TEM in Fig.3,a,b].
Ros1 contains (see typical TEM images in Fig.4 and Fig.5) 50-80wt% of MWNTs and 15-35% of carbon polyhedral nanoparticles, and the rest are different forms of disordered graphite including single graphite sheets, graphite platelets, “light soot”, nanoscales, traces of SWNTs (Fig.3c), etc.
Inorganic impurities are not higher than 0.5wt% and can be easily removed by successful washing in inorganic acids (HCl, HNO₃, H₂SO₄).
Typical X-Ray Diffraction patterns and Micro-Raman spectra are shown in Fig.6. XRD reveals two main interlayer distances in the sh‑MWNTs, 0.341 and 0.345 nm (Fig.6). HR-TEM reveals essentially increased interlayer distances (up to 0.375 nm), especially, for thinner sh‑MWNTs (Fig.7,d).
MWNTs’ length and diameter distributions are characterized by three-modal distributions with maximums at ~200, 300 and 500 nm for lengths, ~6.5, 12 and 20 nm for outer diameters and 2.6, 4.0 and 6.7 nm for inner diameters (the distributions are presented in Fig.7,d)

Ros1 - Field Electron Emission

The MWNTs’ diameter distribution provides excellent Field Electron Emission (FEE) properties. Rough powders of Ros1 start Field Electron Emission (EE) at a threshold of 2‑2.5V/micron, demonstrating intensity currents of 0.5-1 mA/cm² at electric fields of 3‑3.5 V/micron.
Typical FEE I-V-curves are shown in Fig.8 (under the test a powdered Ros1 sample is pressed into a hollow with a cross section of 1mm²).
The FEE parameters strongly depend on admixtures of the graphitic forms (see Fig.9). Separation of the graphitic forms allows improving FEE further

Ros1 - Composites

The MWNTs’ length distribution provides a very good dispersivity (see TEM in Fig.5), solubilization and functionalization of the MWNTs that facilitates producing Composites possessing improved mechanical characteristics even at very low loads of raw Ros1.
Loads of just ~1% of raw Ros1 in PVA improve Young modulus, strength tensile, toughness and electric conductivity in 1.5, 1.75, 2 and 10⁴ times, respectively, in comparison with the blank PVA film (Fig.10,a,b)(Fig.10,c).

Metal composites prepared by electro-codeposition of metals and our sh‑MWNTs (Ros1) exhibit a remarkable improvement of hardness and a decrease of the wear volume in comparison with the blank metal matrix.

Ros1 - BET Surface Area

BET surface area is 6.5-10 m²/g (rough powders). Pore area is about 90-95% of the BET (see graphs in Fig.11).
Hydrogen storage in 10g-powder-samples at room temperature and pressure of ~100 atm  is low, ~ 0.1-0.2wt%. Better storage is expected for oxidized nanotubes.
The tubes are well graphitised and can sustain long oxidation in air and acids (H₂SO₄, HNO₃, HCl, HF/HNO₃, etc). In air perceptible losses of weight (≥2-3rel.%) are achieved for time less than 10-15 min at temperatures higher than 600^oC. Typical TGA are shown in Fig.12.
The MWNTs usually have one semispherical and one conical cap. Under a proper oxidation (for instant, in air at ~600^oC for ~ 45-60 min) the semispherical caps are opened in first turn leaving the conical ones almost intact (HR-TEM in Fig.13).
Further characteristics of Ros1 are coming soon

Ros1-p, purified (under development)

This is a product mainly containing the MWNTs and polyhedral nanoparticles.
A new technique of quantitative separation of the MWNTs from the graphitic carbons is under development.
The technique allows separating large quantities of raw Ros1 powders into 2 fractions, the MWNTs & nanoparticles (see TEM in Fig.14) and the graphitic carbons (see TEM in Fig.15). As a result, FEE from Ros1‑p is highly improved (Fig.9).

Ros2, as produced (under development)

Ros2 is produced in a modified process with use of Co/Ni catalysts.
Ros2 (as produced) contains ~50 wt% of short MWNTs, ~ 20% of carbon polyhedral nanoparticles and the rest are different graphitic forms (highly-disordered graphite, single graphite sheets, graphite platelets, “light soot”, graphitic scales, traces of SWNTs, etc (see typical TEM images in Fig.16, Fig.17,Fig.18).
In HR‑TEM pictures (Fig.19, Fig.20) the most part of Ros‑2 MWNTs exhibit asymmetrical wall-thickness and the extra thickness is concentrated in some isolated singular fringe spacings, which are concentrated in one wall of the MWNTs. This effect can be explained by assuming that the sp‑MWNTs partially consist of scrolls instead of nested cylindrical tubules. The scrolls introduce extra‑space between the layers, the space is usually double of the normal value, i.e. it is ~0.7 nm, but sometimes the spaces of ~1.05 nm and even ~1.4 nm are seen in HR‑TEM pictures of the sp‑MWNTs.
In comparison with Ros1 sh‑MWNTs Ros2 MWNTs are essentially elongated and thickened (see length and diameter distributions in Fig.7).
Upon opening the entries by a careful oxidation, the extra‑space provides additional channels for Gas & Energy storage

Ros3

Ros4

Ros5

Ros6