Filtern
Dokumenttyp
- Zeitschriftenartikel (5)
- Posterpräsentation (4)
- Beitrag zu einem Tagungsband (3)
- Vortrag (2)
- Forschungsbericht (1)
Schlagworte
- Single-walled carbon nanotubes (2)
- Amorphous carbon (1)
- Arc discharge (1)
- Carbon nanofiber (1)
- Carbon nanofiber synthesis (1)
- Carbon nitride films (1)
- Cathodic arc discharge (1)
- Composite (1)
- Conductivity (1)
- Energy storage (1)
- Expanded Graphite (1)
- Functionalization (1)
- Gas Discharge Plasma (1)
- Graphit (1)
- Hydrogen storeage (1)
- Inductively coupled r.f.plasma (1)
- Latentwärmespeicher (1)
- Materialforschung (1)
- Nanotubes (1)
- Oxidation (1)
- Plasmaverfahren (1)
- Polymer (1)
- Raman spectroscopy (1)
- Segregated network (1)
- Sintering (1)
- Storage capacity (1)
- Surface Chemistry (1)
Eingeladener Vortrag
- nein (2)
In 1996, R. T. K. Baker, and N. M. Rodriguez claimed to have synthesized a new type of carbon nanofiber material capable of storing large amounts of hydrogen at room temperature and pressures above 100 bar, thus making it a powerful candidate for a very efficient energy storage system in mobile applications. Consequently, many scientists all over the world tried to test and verify these findings, however, with partly inconsistent results. We present here for the first time independent hydrogen storage measurements for several types of nanofibers, both synthesized by our group following precisely the specifications given in the literature as well as original samples supplied by Rodriguez and Baker for this study. The hydrogen storage capacities at room temperature and pressures up to 140 bar were quantified independently by gravimetric and volumetric methods, respectively. No significant hydrogen storage capacity has been detected for all carbon nanofibers investigated.
In this work we present the preparation of conductive polyethylene/carbon nanotube composites based on the segregated network concept. Attention has been focused on the effect of decreasing the amount of filler necessary to achieve low resistivity. Using high- and low-grade single-walled carbon nanotube materials we obtained conductive composites with a low percolation threshold of 0.5 wt.% for high-grade nanotubes, about 1 wt% for commercial nanotubes and 1.5 wt% for low-grade material. The higher percolation threshold for low-grade material is related to low effectiveness of other carbon fractions in the network formation. The electrical conductivity was measured as a function of the single-walled carbon nanotubes content in the polymer matrix and as a function of temperature. It was also found that processing parameters significantly influenced the electrical conductivity of the composites. Raman spectroscopy was applied to study single wall nanotubes in the conductive composites.
We have developed a very fast and entirely gas-phase based purification technique for carbon nanotubes (CNT) that allows removing metal and metal oxide impurities with high effectiveness. CNT agglomerates from chemical vapor deposition (CVD) synthesis which contained carbon encapsulated catalysts were injected into an atmospheric plasma torch. Very high heating rates allow for quasi-instantaneous vaporization of catalyst particles. This way, metal vapors are hyposized to break mechanically instable encapsulations and effuse from incomplete ones faster than thermally induced graphitization stabilizes such particle encapsulations. The ash content of multi-walled (MW) CNT samples was reduced to less than 15% of the initial value within a few milliseconds. Also the metal content of single-walled (SW) CNT agglomerates was significantly reduced. Repeated injection of CNT agglomerates into the plasma torch resulted in higher-purity products of improved structural integrity and increased oxidation resistance.