Filtern
Dokumenttyp
Schlagworte
- Arc discharge (1)
- Carbon nitride films (1)
- Expanded Graphite (1)
- Functionalization (1)
- Gas Discharge Plasma (1)
- Graphit (1)
- Inductively coupled r.f.plasma (1)
- Latentwärmespeicher (1)
- Materialforschung (1)
- Plasmaverfahren (1)
Single-walled carbon nanotubes (SWNT) and carbon nitride films are synthesized by a direct current (dc) arc discharge at slightly reduced pressure and by an inductively coupled r.f. plasma (ICP) at atmospheric pressure, respectively. By treatment with nitric acid SWNT are purified from by-products and characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. ICP allows the deposition of carbon nitride films on steel substrate. The deposition of the films creates a relatively strong radial symmetric profile. The structure of the films are rather independent of the distance between substrate and plasma. Raman, Fourier transform infrared (FTIR), and energy dispersive X-ray (EDX) spectroscopy are used for analyzing the carbon nitride materials.
Effects of Heat Treatment on the Structure of Thermal Plasma Synthesized SiCN Composite Nanopowders
(2003)
SiCN composite nanopowders with different chemical composition and characteristics were synthesized by the RF induction plasma at atmospheric pressure. Frequently the as-produced powders exhibit a high degree of chemical disorder or structural defects. Because the composition and the microstructure of starting powders have a great influence on the properties of composite ceramics, the changes of chemical composition, crystallization, and morphology of the as-produced powders during heat treatment up to 1500 °C were investigated in detail.
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.