The influence of nitrogen sources on nitrogen doped multi-walled carbon nanotubes (original) (raw)
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Structural and morphological control of aligned nitrogen-doped carbon nanotubes
Carbon, 2010
Nitrogen-doped carbon nanotubes (CN x-NTs) were prepared using a floating catalyst chemical vapor deposition method. Melamine precursor was employed to effectively control nitrogen content within the CN x-NTs and modulate their structure. X-ray photoelectron spectroscopy (XPS) analysis of the nitrogen bonding demonstrates the nitrogen-incorporation profile according to the precursor amount, which indicates the correlation between the nitrogen concentration and morphology of nanotubes. With the increase of melamine amount, the growth rate of nanotubes increases significantly, and the inner structure of CN x-NTs displayed a regular morphology transition from straight and smooth walls (0 at.% nitrogen) to cone-stacked shapes or bamboo-like structure (1.5%), then to corrugated structures (3.1% and above). Both XPS and CHN group results indicate that the nitrogen concentration of CN x-NTs remained almost constant even after exposing them to air for 5 months, revealing superior nitrogen stability in CNTs. Raman analysis shows that the intensity ratio of D to G bands (I D /I G) of nanotubes increases with the melamine amount and position of G-band undergoes a down-shift due to increasing nitrogen doping. The aligned CN x-NTs with modulated morphology, controlled nitrogen concentration and superior stability may find potential applications in developing various nanodevices such as fuel cells and nanoenergetic functional components.
Synthesis of Nitrogen doped carbon nanotubes
Nitrogen-doped CNTs (N-CNTs) were synthesized using an injection-vertical chemical vapor deposition (IV-CVD) reactor. This type of reactor is quite useful for the continuous mass production of CNTs. In this work, the optimum deposition conditions for maximizing the incorporation of nitrogen were identified. Ferrocene served as the source of the Fe catalyst and was dissolved in acetonitrile, which served as both the hydrocarbon and nitrogen sources. Different concentrations of ferrocene in acetonitrile were introduced into the top of a vertically aligned reactor at a constant flow rate with hydrogen serving as the carrier. The effects of hydrogen flow rate, growth temperature, and catalyst loading (Fe from the ferrocene) on the microstructure, elemental composition, and yield of N-CNTs were investigated. The N-CNTs possessed a bamboo-like microstructure with a nitrogen doping level as high as 14 at.% when using 2.5 to 5 mg/mL of the ferrocene/acetonitrile mixture at 800 ∘ C under a 1000 sccm flow of hydrogen. A production rate of 100 mg/h was achieved under the optimized synthesis conditions.
Incorporation of nitrogen in carbon nanotubes
Journal of Non-Crystalline Solids, 2002
Nitrogen-doped carbon nanotubes were obtained by the arc-discharge technique in a helium-nitrogen atmosphere and using iron-nickel-cobalt catalysts, The samples were analyzed using spectroscopic techniques (Raman, EELS, Xray photoelectron spectroscopy) and transmission electron microscopy (TEM). Pure helium atmosphere conditions led to bundles of single-wall nanotubes with diameters of $1.5 nm. The presence of nitrogen during tube formation produced irregular and thickly textured tubes. TEM micrographs showed that N suppresses the formation of bundles of single-wall nanotubes, giving rise to nested nanofibers. Quantum-chemical calculations were carried out to study the influence of substitutional N on the tube conformation. The calculations show that the combination of hexagons and pentagons at low N concentration produces kinks that account for the irregular shaped nanotubes. Ó
Role of Atomic and Molecular Nitrogen in Carbon Nanotube Formation
Journal of the Korean Physical Society, 2009
We have investigated the pretreatment effects of nitrogen on the length and the alignment of carbon nanotubes (CNTs) grown on a Ni catalyst by using dc-plasma enhanced chemical vapor deposition system. The surface of the Ni catalyst was pretreated with a mixture of NH 3 and N 2 , instead of pure NH 3
Influence of Ni−Co Catalyst Composition on Nitrogen Content in Carbon Nanotubes
The Journal of Physical Chemistry B, 2004
Nitrogen-containing carbon nanotubes were obtained by pyrolysis of acetonitrile (CH 3 CN) at 850°C over catalytic nanoparticles formed by the thermal decomposition of Co and Ni bimaleates or their mutual solutions. Structure and composition of synthesized samples were studied by electron microscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). It is found that the yield of the nanotubes, the quality of the layer packing, and nitrogen content in the CN x nanotubes depend on the catalyst composition. XPS of the N 1s spectra show that nitrogen atoms are in two different electronic states in the carbon nanotubes. According to quantum chemical calculations these states can be ascribed to nitrogen atoms substituting for carbon atoms in the graphite network and pyridine-like atoms. It was shown that the nanotubes synthesized using catalyst with the ratio Ni/Co 1:1 contain the greatest proportion of pyridine-like nitrogen.
Synthesis and Characterization of Nitrogen-doped Carbon Nanotubes Derived from g-C3N4
Materials
Here, nitrogen-doped carbon nanotubes (CNT-N) were synthesized using exfoliated graphitic carbon nitride functionalized with nickel oxides (ex-g-C3N4-NixOy). CNT-N were produced at 900 °C in two steps: (1) ex-g-C3N4-NixOy reduction with hydrogen and (2) ethylene assisted chemical vapor deposition (CVD). The detailed characterization of the produced materials was performed via atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The possible mechanism of nanotubes formation is also proposed.
Carbon, 2009
We describe the systematic study of multi-walled carbon nanotubes with different nitrogen doping produced by aerosol chemical vapor deposition. Benzylamine:toluene mixtures of 0:100, 5:95, 10:90, 25:75, 50:50, 75:25 and 100:0 were thermally decomposed at 800-900°C under argon at atmospheric pressure, whereby the nitrogen content of the bulk material was varied between 0 and 2.2 at%. We also show how the presence of nitrogen in the precursor changed the nanotube morphology, i.e. nitrogen decreased the number of kinks incorporated into the carbon nanotubes, decreased their length and diameter and increased the proportion of 'bamboo' shaped nanotubes. Furthermore, due to the nitrogen doping, the oxidation resistance of the nanotube material was decreased. With concentrations above 10% benzylamine the increase of the reaction temperature had no significant effect on the quality of the nanotubes, however, at higher temperatures the nitrogen content was decreased. We demonstrate the control over the nanotube geometry, the nitrogen content and oxidation resistance of the nanotubes, and show that these properties are interlinked.
Nitrogen Doped Carbon Nanotubes from Organometallic Compounds: A Review
Materials, 2010
Nitrogen doped carbon nanotubes (N-CNTs) have become a topic of increased importance in the study of carbonaceous materials. This arises from the physical and chemical properties that are created when N is embedded in a CNT. These properties include modified chemical reactivity and modified conductivity and mechanical properties. A range of methodologies have been devised to synthesize N-CNTs. One of the procedures uses a floating catalyst in which an organometallic complex is decomposed in the gas phase in the presence of a nitrogen containing reactant to give N-CNTs. Most studies have been limited to ferrocene, ring substituted ferrocene and Fe(CO) 5. This review covers the synthesis (and properties) of N-CNTs and other shaped carbon nanomaterials (SCNMs) produced using organometallic complexes. It summarizes the effects that physical parameters such as temperature, pressure, gas flow rates, type and concentration of N source etc. have on the N-CNT type, size and yields as well as the nitrogen content incorporated into the tubes that are produced from organometallic complexes. Proposed growth models for N-CNT synthesis are also reported.
The role of nitrogen in carbon nanotube formation
Diamond and Related Materials, 2003
To examine the role of nitrogen, Co-and Ni-coated substrates were pretreated with three different gas compositions to compare the pretreated catalyst surfaces; the Fe, Co and Ni foils were subjected to carbon nanotube (CNT) growth experiments with CH y 4 H and CH yN as source gases; the catalyst pretreatment plus the CNT growth experiments on Co-and Ni-coated Si substrates 2 4 2 were carried out using both microwave plasma chemical vapor deposition and electron cyclotron resonance chemical vapor deposition (ECR-CVD) under different nitrogen-containing gases. The results show that the role of nitrogen may be summarized as follows: by comparing with hydrogen plasma, the bombardment energy of nitrogen plasma is greater. Therefore, the presence of nitrogen during CNT growth can keep the front catalyst surface clean and active to prolong surface passivation to enhance carbon bulk diffusion. The higher temperature due to higher bombardment energy of nitrogen plasma can promote agglomeration effects during catalyst pretreatment and the initial stage of CNT growth to produce larger size nano-particles. The presence of nitrogen is a favorable condition for formation of the bamboo-like CNTs, but not a necessary condition. Another favorable condition for formation of the bamboo-like CNTs is to deposit CNTs by ECR-CVD. ᮊ