Nitrogen Carbon Nanotubes Research Articles

Tailoring the diameter of decorated C–N nanotubes by temperature variations using HF-CVD

Patterned films of decorated nitrogenated carbon (C–N) nanotubes were catalytically synthesised by hot filament chemical vapour deposition (HF-CVD) in a nitrogen–methane–ammonia environment. The systematic study of a transition between different kinds of C–N nanostructures as a function of the local substrate temperature ranging from 700 up to 820°C is presented. The morphology, the diameter as well as the properties of the generated tubular structures showed strong dependence on this parameter. By means of electron microscopy a new type of decoration covering all tubular structures was observed. Buckled lattice fringes revealed the disordered graphitic-like character of the hollow C–N nanotubes. Raman spectroscopy confirmed a transition in the microscopic order as a function of temperature. Furthermore field emission in vacuum was studied and showed a spectacular correlation to the deposition temperature and therefore the diameter of the C–N tubes. For arrays of tubes thinner than 50 nm an onset field below 4 V/μm was observed.

Influence of the deposition conditions on the field emission properties of patterned nitrogenated carbon nanotube films

The electron field emission of patterned films of nitrogenated carbon nanotubes is shown to be decisively influenced by the deposition conditions. The growth was carried out by decomposing methane in a nitrogen/ammonia atmosphere using hot filament chemical vapor deposition (CVD). The diameter of the produced tubes depended critically on the distance between substrate and filament, and the field emission properties (applied fields needed for electron emission, field amplification factor) could be directly correlated to the film morphology. This demonstrates the possibility of tuning the field emission properties of such film emitters. For arrays of nanotubes thinner than 50 nm, the onset of field emission was observed at ∼4 V/μm, and a current density of 10 mA/cm 2 was obtained for an applied field of 7.2 V/μm.

Influence of Nitrogen on the Growth Mechanism of Decorated C:N Nanotubes

Nanotubes like feather boas were synthesised by the decomposition of methane in a nitrogen atmosphere using a bias-enhanced hot-filament chemical vapour deposition technique. This new type of slightly nitrogenated carbon (C:N) nanotubes exhibits a vermicular shape. Graphitic thin foils growing perpendicular to the tube axis typically cover the surface of each C:N tube. High-resolution transmission electron microscopy reveals the graphitic structure to be characterised by strong disorder at different length scales. The role of small amounts of nitrogen, which affects the structural formation of the growing C:N tubes, is discussed.

Synthesis and characterization of well-aligned carbon nitrogen nanotubes by microwave plasma chemical vapor deposition

Well-aligned carbon nitrogen nanotube films have been synthesized successfully on mesoporous silica substrates by microwave plasma chemical vapor deposition (MWPCVD) method. Studies on their morphology, structure, and composition by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX), respectively, indicate that these nanotubes consist of linearly polymerized carbon nitrogen nanobells, and the nitrogen atoms have been doped into carbon netweork to form a new structure C1−x N x (x=0.16±0.01). X-ray photoelectron spectroscopy (XPS) results of the samples further demonstrate that carbon bonds covalently with nitrogen in all the carbon nitrogen nanotube films.

Production of bundles of aligned carbon and carbon–nitrogen nanotubes by the pyrolysis of precursors on silica-supported iron and cobalt catalysts

Pyrolysis of acetylene over iron or cobalt nanoparticles well dispersed on silica substrates gives copious yields of aligned carbon nanotube bundles. By carrying out the pyrolysis of pyridine over these catalyst surfaces, good quantities of aligned carbon–nitrogen nanotube bundles have been produced. The composition of the carbon–nitrogen nanotubes varies between C 10N and C 33N, depending on the catalyst.

The role of catalysts and temperature on morphology and field emission properties of decorated C:N nano-tubular structures

AbstractA hot filament chemical vapour deposition (HF-CVD) process was used to synthesise nitrogenated carbon (C:N) nanotubes characterised by feather-like decoration of the tube surface. As a function of deposition temperature the diameter of the produced tubular structures could be adjusted in a controlled way ranging from 1 µm to 50 nm. The influence of catalysts was demonstrated comparing the morphology of catalytically grown tubes with tubes grown onto pure Si wafers. High resolution TEM reveals that the nanotubes are hollow with a wall structure consisting of inner ordered walls and an outer more disordered surface. A possible growth mechanism will be discussed. Furthermore, field emission in vacuum was studied and showed a spectacular correlation to the deposition temperature and therefore the diameter of the C:N tubes.

A New Development in Covalently Bonded Carbon Nitride and Related Materials

The large scale carbon-nitrogen nanotubes C1-xNx (where x = 0.15 to 0.17) shown in the Figure are just one of the many covalently bonded carbon nitride materials surveyed in this article. The fabrication as well as physical and chemical properties of these technologically important materials is discussed, as are methods for their physical analysis and the usefulness of theoretical predictions.

Simultaneous Synthesis of Carbon Nanotubes and Nitrogen-Doped Fullerenes in Nitrogen Atmosphere

By arcing a graphite rod in a pure nitrogen atmosphere, both carbon nanotubes and nitrogen-doped fullerenes have been synthesized simultaneously for the first time. Carbon nanotubes are prepared in nitrogen in much greater yield than when an inert gas is employed. Unusual structural features of the nanotubes have been observed by TEM imaging. In addition, nitrogen-doped fullerenes were characterized through laser desorption mass spectrometry and X-ray photoelectron spectroscopy. 12 refs., 4 figs.