共查询到20条相似文献,搜索用时 15 毫秒
1.
C.J. Unrau R.L. Axelbaum P. Biswas P. Fraundorf 《Proceedings of the Combustion Institute》2007,31(2):1865-1872
A novel technique for synthesis of single-walled carbon nanotubes (SWNTs) in diffusion flames is presented, as is a diagnostic tool that can provide online information about nanotube size, number density, and purity. An inverse diffusion flame with a high stoichiometric mixture fraction (Zst) is used to produce SWNTs with an average length of 1 μm. The high Zst flame allows nanotubes to be produced in a fuel-rich region that is void of soot and polycyclic aromatic hydrocarbons (PAH). In addition, by operating as an inverse diffusion flame the carbon nanotubes (CNTs) are not exposed to oxygen and thus, can be collected downstream. Consequently, this flame provides a potential approach to large-scale synthesis of pure SWNTs. In addition, a differential mobility analyzer (DMA) is employed as an online diagnostic tool. The DMA can distinguish between excess catalyst particles and CNTs due to the differences in their electrical mobilities. Thus, the presence of CNTs as well as their size, number density, and purity relative to excess catalyst particles can be identified from the size distribution of the aerosol sampled downstream of the flame. This tool allows for rapid identification of the effect of changing process variables on nanotube growth and thus, the production process can be quickly optimized. 相似文献
2.
Albert G. Nasibulin Anna Moisala Hua Jiang Esko I. Kauppinen 《Journal of nanoparticle research》2006,8(3-4):465-475
Single- and multiwalled carbon nanotubes (CNTs) were synthesised by a novel aerosol method using alcohols, namely ethanol and octanol, as carbon precursors. Preformed iron and nickel aerosol nanoparticles, produced by evaporation from resistively heated metal wire, were used as catalysts. Multiwalled CNTs were initiated by 10 nm sized catalyst particles and produced in the presence of ethanol vapour with the partial pressure of 7072 Pa, while combination of 2.4 nm particles and decreased alcohol vapour pressure (123 Pa) resulted in the formation of mainly single-walled and a small fraction of double-walled CNTs. The effect of a promoter (thiophene) in the system was found to be very important for the synthesis of multiwalled CNTs, while only a 30% number concentration increase was found for the single-walled CNT production. 相似文献
3.
Growth of aligned single-walled carbon nanotubes under ac electric fields through floating catalyst chemical vapour deposition 下载免费PDF全文
Through floating catalyst chemical vapour deposition(CVD) method,well-aligned isolated single-walled carbon nanotubes (SWCNTs) and their bundles were deposited on the metal electrodes patterned on the SiO2/Si surface under ac electric fields at relatively low temperature(280℃). It was indicated that SWCNTs were effectively aligned under ac electric fields after they had just grown in the furnace.The time for a SWCNT to be aligned in the electric field and the effect of gas flow were estimated. Polarized Raman scattering was performed to characterize the aligned structure of SWCNTs. This method would be very useful for the controlled fabrication and preparation of SWCNTs in practical applications. 相似文献
4.
Fe K-edge X-ray absorption fine structure (XAFS) measurements were performed in order to elucidate the formation mechanism of single-walled carbon nanotubes (SWCNTs) grown on natural magnesite by pyrolyzing methane gas. It was clearly shown by XAFS analyses that iron metal fine particles, which were reduced from iron oxides by methane gas, worked as a catalyst for SWCNT growth. Structural characteristics of the initial iron state in the natural magnesite were also discussed. 相似文献
5.
P. N. Gevko A. V. Okotrub L. G. Bulusheva I. V. Yushina U. Dettlaff-Weglikowska 《Physics of the Solid State》2006,48(5):1007-1011
The thermal stability of initial and purified samples of single-walled carbon nanotubes prepared through gas-phase disproportionation of carbon monoxide CO in the presence of iron particles under high pressure (the HiPCO method) is investigated using optical absorption spectroscopy and thermogravimetry. An analysis of the optical absorption spectra demonstrates that thermal oxidation of the initial material proceeds rather rapidly and uniformly owing to the catalytic effect caused by the presence of iron particles in the sample. The destruction of the carbon nanotubes contained in the as-prepared and purified samples begins at temperatures of ~250 and ~300°C, respectively. It is shown that single-walled metallic nanotubes undergo faster oxidation as compared to the single-walled semiconducting nanotubes. 相似文献
6.
Farbod Alimohammadi Mazeyar Parvinzadeh Gashti Ali Shamei Amir Kiumarsi 《Superlattices and Microstructures》2012
Silver was stabilized on multi-walled carbon nanotubes (MWCNTs) by chemical-reduction technique using N,N-dimethylformamide (DMF) as a reducing agent. The influence of silver on the performance of carbon nanotubes (CNTs) was investigated by employing Fourier-transform infrared spectra (FTIR), Raman spectroscopy (RAS), thermal gravimetric analysis (TGA), zeta potential measurement, scanning electron microscope (SEM), electron dispersive X-ray spectrometer (EDX), transmission electron microscopy (TEM), and reflectance spectroscopy (RS). FTIR as well as RS methods evidenced the synthesis procedure using chemical reduction method was successful. Performing TGA of the samples under oxygen atmosphere demonstrated that the silver nanoparticles (Ag NPs) generated on MWCNTs surface can decrease the thermal stability of the particles by the catalytic oxidation of CNTs. In contrary, the thermal stability of the MWCNTs has improved under nitrogen atmosphere. EDX results showed the presence of Ag, Au and Co on the surface of deposited sample. The synthesised silver multi-walled carbon nanotubes (Ag–MWCNTs) were found to have higher UV reflection activity compared with untreated particles. The Ag–CNTs can be used in producing anti-UV composites. 相似文献
7.
In this work, we have synthesized large diameter multi-walled carbon nanotubes (MWNTs), by simple catalyst chemical vapor
deposition (CCVD). Fe powder was spread on quartz substrate as a catalyst by a simple method and then heated under Ar atmosphere.
Carbon’s products can be synthesized by the decomposition of ethylene gas and deposition of carbon atoms on the Fe catalyst
particles in Ar atmosphere at 930°C. XRD pattern, SEM and TEM images were used to investigate the characteristics, morphology
and structure of carbon’s products. 相似文献
8.
In this work we performed the filling of single-walled carbon nanotube channels with metallic silver and copper by means of two-step synthesis including imbuing with metal nitrate aqueous solution and further annealing. It has been shown that metal insertion into the nanotube cavities results in the Fermi level upshift and the charge transfer from metal to carbon atoms, thus donor doping of single-walled carbon nanotubes takes place. At the same time, encapsulated silver has a larger donor effect on the carbon nanotubes that has been proved by Raman spectroscopy and X-ray photoelectron spectroscopy. 相似文献
9.
In this paper, we report that ruthenium is an active and efficient catalyst for growth of single-walled carbon nanotubes (SWNTs) by a chemical vapor deposition (CVD) process for the first time. High density random and horizontally superlong well-oriented SWNTs on substrate can be fabricated via CH4 or EtOH as carbon source under suitable conditions. Scanning and transition electron microscopy investigations, Raman spectroscopy and atomic force microscopy measurements show the tubular structure, the high crystallinity, and the properties of the grown nanotubes. The results show that the SWNTs from ruthenium have better structural uniformity with less defects and provides an alternative catalyst for SWNTs growth. The successful growth of SWNTs by Ru catalyst provides new experimental information for understanding the growth mechanism of SWNTs, which may be helpful for their controllable synthesis. 相似文献
10.
11.
N. I. Alekseev 《Physics of the Solid State》2006,48(8):1616-1623
A computational model is proposed for the growth of nanotubes on a nanoporous substrate with metal catalyst particles on the pore bottom. It is demonstrated that the simulated morphology of nanotubes formed over a wide range of conditions is in complete agreement with the experimental data. Both the top and root growth can be observed for multiwalled nanotubes, whereas single-walled nanotubes are characterized only by the root growth and the growing end of the nanotube is always free of the catalyst. 相似文献
12.
Shandakov S. D. Rybakov M. S. Chirkova I. M. Russakov D. M. Vershinina A. I. Lomakin M. V. Kosobutsky A. V. Popov Yu. S. 《Russian Physics Journal》2019,62(5):800-804
Russian Physics Journal - Properties of single-walled carbon nanotubes (SWCNTs) obtained by the floating catalyst CVD method using ethyl alcohol and coal (anthracite and semi-anthracite) particles... 相似文献
13.
Measuring particle size-dependent physicochemical structure in airborne
single walled carbon nanotube agglomerates 总被引:1,自引:1,他引:1
Andrew D. Maynard Bon Ki Ku Mark Emery Mark Stolzenburg Peter H. McMurry 《Journal of nanoparticle research》2007,9(1):85-92
As-produced single-walled carbon nanotube (SWCNT) material is a complex matrix of carbon nanotubes, bundles of nanotubes (nanoropes),
non-tubular carbon and metal catalyst nanoparticles. The pulmonary toxicity of material released during manufacture and handling
will depend on the partitioning and arrangement of these components within airborne particles. To probe the physicochemical
structure of airborne SWCNT aggregates, a new technique was developed and applied to aerosolized as-produced material. Differential
Mobility Analysis-classified aggregates were analyzed using an Aerosol Particle Mass Monitor, and a structural parameter Γ
(proportional to the square of particle mobility diameter, divided by APM voltage) derived. Using information on the constituent
components of the SWCNT, modal values of Γ were estimated for specific particle compositions and structures, and compared
against measured values. Measured modal values of Γ for 150 nm mobility diameter aggregates suggested they were primarily
composed of non-tubular carbon from one batch of material, and thin nanoropes from a second batch of material – these findings
were confirmed using Transmission Electron Microscopy. Measured modal values of Γ for 31 nm mobility diameter aggregates indicated
that they were comprised predominantly of thin carbon nanoropes with associated nanometer-diameter metal catalyst particles;
there was no indication that either catalyst particles or non-tubular carbon particles were being preferentially released
into the air. These results indicate that the physicochemistry of aerosol particles released while handling as-produced SWCNT
may vary significantly by particle size and production batch, and that evaluations of potential health hazards need to account
for this.
Disclaimer: The mention of any company or product does not constitute an endorsement by the Centers for Disease Control and
Prevention. The findings and conclusions in this paper are those of the authors and do not necessarily represent the views
of the National Institute for Occupational Safety and Health. 相似文献
14.
Superconductivity in the single-walled carbon nanotubes is investigated. First, effect of diameter increasing on the clean systems critical temperature, Tc, is calculated. Then effect of impurity doping on the reduction of critical temperature Tc, of single-walled carbon nanotubes, is discussed. Our calculations illustrate that metallic zigzag single-walled carbon nanotubes have higher Tc than armchair single-walled carbon nanotubes with approximately same diameters and Tc decreases by increasing diameter. This can explain why superconductivity could be found in the small diameter single-walled carbon nanotubes. We found for the impurity doped systems, impurity in the strong scattering regime can decrease Tc significantly while in the weak scattering regime Tc is not affected by impurity doping. 相似文献
15.
The synthesis of multi-walled carbon nanotubes (MWNTs) by catalytic pyrolysis of the phenol-formaldehyde resins 总被引:1,自引:0,他引:1
Ioan Stamatin Adina Morozan Anca Dumitru V. Ciupina G. Prodan J. Niewolski H. Figiel 《Physica E: Low-dimensional Systems and Nanostructures》2007,37(1-2):44
A series of carbon nanomaterials, particularly multi-walled carbon nanotubes (MWNT), are obtained as products from catalytic pyrolysis of the cross-linked phenol-formaldehyde resins with different ferrocene under inert atmosphere. The morphology and structure of the samples were evaluated by TEM and XRD techniques. CNTs morphology is dependent on the iron nanoparticles and their forms (Fe, Fe3C) resulted from ferrocene decomposition. The amount of nanotubes increases with iron content released from ferrocene catalyst during the pyrolysis process. Fe3C nanoparticles drive the nucleation and the growth of carbon nanotubes during the pyrolysis process. Long (up to microns) well-defined MWNTs with small defects, ropes and disordered carbon are representatives in the pyrolyzed resins composition. 相似文献
16.
In continuation of our research on carbon nanotube/P(VDF-TrFE) nano-composites [1], total x-ray fluorescence (TXRF) is engaged
in a novel characterization of these materials regarding their compositions, purities, and structural analysis. Samples such
as single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), P(VDF-TrFE) copolymer, SWCNT/P(VDF-TrFE),
and MWCNT/P(VDF-TrFE) were analyzed by TXRF. The synthetic quartz used as a substrate was analyzed as reference material for
the TXRF measurements. The ethanol and the dimethylformamide (DMF) used as solvents for carbon nanotubes and copolymers respectively
were also analyzed by TXRF to determine whether they have an influence or not on the TXRF of the previous material. The preliminary
results showed that single-walled and multi-walled carbon nanotubes prepared by the arc-discharge method contain catalytic
particles such as Fe, Co, and Ni used to obtain SWCNT while there were no metal or impurities in MWCNT. The TXRF spectrum
of CNT/P(VDFTrFE) showed the same results as we found previously with background due to the P(VDF-TrFE) copolymer scattered
signal.
__________
Published in Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 5, pp. 700–702, September–October, 2005. 相似文献
17.
Yaser ShiraziMaryam Ahmadzadeh Tofighy Toraj Mohammadi Afshin Pak 《Applied Surface Science》2011,257(16):7359-7367
Cyclohexanol and xylene were used as carbon precursors, for synthesis of multiwall carbon nanotubes (MWCNTs) arrays in a CVD system at temperature of 750 °C, using nitrogen as carrier gas and ferrocene as catalyst. Different characterization methods were employed to compare the MWCNTs structure synthesized by these two precursors. All scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA) and Raman spectroscopy results illustrated that using cyclohexanol could significantly reduce formation of amorphous carbon and catalyst particles in the as-grown CNTs. The less amorphous carbon can be attributed to in situ oxidation in presence of oxygen atom of cyclohexanol. Characterizations showed that MWCNTs with high purity could be obtained using cyclohexanol as carbon precursor. The as-grown MWCNTs were purified by oxidation and acid treatment. Characterization of the purified MWCNTs using HNO3/H2SO4 (1/3 or 1/1), 8 M HCl or 8 M HNO3 was carried out. The results showed that 8 M HNO3 could be considered as the best chemical to obtain more pure MWCNTs, less amorphous and metal particles and less damaged MWCNTs. The Raman spectroscopy results demonstrated that HNO3/H2SO4 (1/3) treatment could more disorder the MWCNTs structure and this was attributed to the bigger destroying effect of this acid treatment. Furthermore, the TEM analysis of MWCNTs before and after acid treatment revealed that acid treatment could remove encapsulated catalyst particles. The FTIR analysis illustrated that purification of the MWCNTs with nitric acid could connect the functional groups onto the outer surface of MWCNTs and this resulted in more dispersion of the MWCNTs in water. 相似文献
18.
T. Somanathan 《Applied Surface Science》2008,254(17):5643-5647
Iron, cobalt and a mixture of iron and cobalt incorporated mesoporous MCM-41 molecular sieves were synthesised by hydrothermal method and used to investigate the rules governing their nanotube producing activity. The catalysts were characterised by XRD and N2 sorption studies. The effect of the catalysts has been investigated for the production of carbon nanotubes at an optimised temperature 750 °C with flow rate of N2 and C2H2 is 140 and 60 ml/min, respectively for a reaction time 10 min. Fe-Co-MCM-41 catalyst was selective for carbon nanotubes with low amount of amorphous carbon with increase in single-walled carbon nanotubes (SWNTs) yield at 750 °C. Formation of nanotubes was studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Transmission electron microscope and Raman spectrum was used to follow the quality and nature of carbon nanotubes formed and the graphitic layers and disordered band, which shows the clear evidence for the formation of SWNTs, respectively. The result propose that the diameter of the nanotubes in the range of 0.78-1.35 nm. Using our optimised conditions for this system, Fe-Co-MCM-41 showed the best results for selective SWNTs with high yield when compared with Fe-MCM-41 and Co-MCM-41. 相似文献
19.
The formation mechanism of the coaxial carbon-metal nanowires in a chemical vapor deposition process
In the synthesis of carbon nanotubes from ethylene decomposition by a Fe/Mo/Al2O3 catalyst at 823 K, the long and continuous coaxial carbon-metal nanowires up to 540 nm is observed. And for the first time, it is observed that the coaxial carbon-metal nanowires can grow in tip and base growth mode simultaneously. A detailed formation mechanism is proposed, where the aggregation of metal particles, lift-up of nanotubes obeying different growth modes and the deformation of metal particles by nanotubes are considered as the necessary steps for the formation of the nanowires. 相似文献
20.
X.Y. Dou Z.P. Zhou P.H. Tan L. Song L.F. Liu X.W. Zhao S.D. Luo X.Q. Yan D.F. Liu J.X. Wang Y. Gao Z.X. Zhang H.J. Yuan W.Y. Zhou S.S. Xie 《Physica E: Low-dimensional Systems and Nanostructures》2005,27(4):469-473
In this paper, we developed a new kind of substrate, the silver-coated anodic aluminum oxide (AAO), to investigate the characters of surface-enhanced resonant Raman scattering (SERRS) of the dilute single-walled carbon nanotubes. Homogeneous Ag-coated AAO substrate was obtained by decomposing the AgNO3 on the surface of AAO. single-walled carbon nanotubes (SWNTs) were directly grown onto this substrate through floating catalyst chemical vapor deposition method (CVD). SERRS of SWNTs was carried out using several different wavelength lasers. The bands coming from metallic SWNTs were significantly enhanced. The two SERRS mechanisms, the “electromagnetic” and “chemical” mechanism, were mainly responsible for the experiment results. 相似文献