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Different carbon nanostructured materials obtained in catalytic chemical vapor deposition
Veríssimo, Carla;Moshkalyo, Stanislav A.;Ramos, Ant?nio C. S.;Gon?alves, José L.;Alves, Oswaldo L.;Swart, Jacobus W.;
Journal of the Brazilian Chemical Society , 2006, DOI: 10.1590/S0103-50532006000600009
Abstract: different carbon nanostructured materials, such as nanotubes, nanofibers, nanosprings and nanooctopus, were grown by changing the metal catalyst and experimental parameters of the thermal chemical vapor deposition process. these experiments were performed using a tubular furnace and methane or acetylene as carbon feedstock gases. thin films of ni or cu were deposited onto a sio2/si substrate and employed as catalysts. the effect of the growth temperature, metal catalyst and carbon gas precursor (methane or acetylene) on the final carbon nanoestructured material was studied by scanning electron microscopy, raman spectroscopy and grazing incidence x-ray diffraction. growth of multiwall carbon nanotubes (mwcnts) was observed using both metal films and carbon precursor gases, whereas partially oxidized ni films promoted formation of nanosprings. experiments with reduced supply of methane resulted in octopus-like carbon nanostructures when a cu film was used as a catalyst.
STRUCTURE AND MORPHOLOGY OF CARBON NANOTUBES GROWN ON ZEOLITE-SUPPORTED CATALYSTS BY CHEMICAL VAPOR DEPOSITION

Sun Lian-feng,Mao Jian-min,Chang Bao-he,Pan Zheng-wei,Wang Gang,Zhou Wei-ya,

中国物理 B , 1999,
Abstract: The zeolite-supported catalysts were prepared in nickel and cobalt nitrate aqueous solutions by ion exchange method. After reducing these substrates by hydrogen, we grew carbon nanotubes on them by chemical vapor deposition under different conditions. The results reveal that nickel/zeolite, cobalt/zeolite and nickel+cobalt/zeolite have different optimal conditions. When nickel+cobalt/zeolite was used as the catalyst, we can get straight carbon nanotubes. The Raman spectrum of the straight nanotubes shows they have fewer defects. We propose a growth mechanism for the growth of these nanotubes.
Suitability of carbon nanotubes grown by chemical vapor deposition for electrical devices  [PDF]
B. Babic,J. Furer,M. Iqbal,C. Schonenberger
Physics , 2004, DOI: 10.1063/1.1812153
Abstract: Using carbon nanotubes (CNTs) produced by chemical vapor deposition, we have explored different strategies for the preparation of carbon nanotube devices suited for electrical and mechanical measurements. Though the target device is a single small diameter CNT, there is compelling evidence for bundling, both for CNTs grown over structured slits and on rigid supports. Whereas the bundling is substantial in the former case, individual single-wall CNTs (SWNTs) can be found in the latter. Our evidence stems from mechanical and electrical measurements on contacted tubes. Furthermore, we report on the fabrication of low-ohmic contacts to SWNTs. We compare Au, Ti and Pd contacts and find that Pd yields the best results.
An Investigation on the Formation of Carbon Nanotubes by Two-Stage Chemical Vapor Deposition
M. S. Shamsudin,M. F. Achoi,M. N. Asiah,L. N. Ismail,A. B. Suriani,S. Abdullah,S. Y. S. Yahya,M. Rusop
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/972126
Abstract: High density of carbon nanotubes (CNTs) has been synthesized from agricultural hydrocarbon: camphor oil using a one-hour synthesis time and a titanium dioxide sol gel catalyst. The pyrolysis temperature is studied in the range of 700–900°C at increments of 50°C. The synthesis process is done using a custom-made two-stage catalytic chemical vapor deposition apparatus. The CNT characteristics are investigated by field emission scanning electron microscopy and micro-Raman spectroscopy. The experimental results showed that structural properties of CNT are highly dependent on pyrolysis temperature changes.
Sandwich Growth of Aligned Carbon Nanotubes Array using Thermal Chemical Vapor Deposition Method
Norani Muti Mohamed,Lai Mun Kou
Journal of Applied Sciences , 2011,
Abstract: Production of highly oriented Carbon Nanotubes (CNTs) array is desirable when enhanced electrical properties are required for better performed nanotubes-based devices. The conventional method produces single array CNTs which does not fulfil the requirement for two terminal devices. The study reports a successful production of double layer structure of aligned carbon nanotubes array as a result of the sandwich growth via thermal Chemical Vapor Deposition (CVD) method. Unlike the reported microwave plasma CVD method which uses a tiny top substrate, the high density aligned multiwalled CNTs grown here are from equal-sized catalyst coated substrates stacked in the sandwich configuration. This proves that thermal CVD method is capable of producing good quality, freestanding CNTs array that are connected to two surfaces for possible application in the two terminals electronic devices.
Microwave Plasma Enhanced Chemical Vapor Deposition of Carbon Nanotubes  [PDF]
Ivaylo Hinkov, Samir Farhat, Cristian P. Lungu, Alix Gicquel, Fran?ois Silva, Amine Mesbahi, Ovidiu Brinza, Cornel Porosnicu, Alexandru Anghel
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2014, DOI: 10.4236/jsemat.2014.44023
Abstract:

Multi-walled carbon nanotubes (MWCNTs) were grown by plasma-enhanced chemical vapor deposition (PECVD) in a bell jar reactor. A mixture of methane and hydrogen (CH4/H2) was decomposed over Ni catalyst previously deposited on Si-wafer by thermionic vacuum arc (TVA) technology. The growth parameters were optimized to obtain dense arrays of nanotubes and were found to be: hydrogen flow rate of 90 sccm; methane flow rate of 10 sccm; oxygen flow rate of 1 sccm; substrate temperature of 1123 K; total pressure of 10 mbar and microwave power of 342 Watt. Results are summarized and significant main factors and their interactions were identified. In addition a computational study of nanotubes growth rate was conducted using a gas phase reaction mechanism and surface nanotube formation model. Simulations were performed to determine the gas phase fields for temperature and species concentration as well as the surface-species coverage and carbon nanotubes growth rate. A kinetic mechanism which consists of 13 gas species, 43 gas reactions and 17 surface reactions has been used in the commercial computational fluid dynamics (CFD) software ANSYS Fluent. A comparison of simulated and experimental growth rate is presented in this paper. Simulation results agreed favorably with experimental data.

On the Growth and Microstructure of Carbon Nanotubes Grown by Thermal Chemical Vapor Deposition  [cached]
Handuja Sangeeta,Srivastava P,Vankar VD
Nanoscale Research Letters , 2010,
Abstract: Carbon nanotubes (CNTs) were deposited on various substrates namely untreated silicon and quartz, Fe-deposited silicon and quartz, HF-treated silicon, silicon nitride-deposited silicon, copper foil, and stainless steel mesh using thermal chemical vapor deposition technique. The optimum parameters for the growth and the microstructure of the synthesized CNTs on these substrates are described. The results show that the growth of CNTs is strongly influenced by the substrate used. Vertically aligned multi-walled CNTs were found on quartz, Fe-deposited silicon and quartz, untreated silicon, and on silicon nitride-deposited silicon substrates. On the other hand, spaghetti-type growth was observed on stainless steel mesh, and no CNT growth was observed on HF-treated silicon and copper. Silicon nitride-deposited silicon substrate proved to be a promising substrate for long vertically aligned CNTs of length 110–130 μm. We present a possible growth mechanism for vertically aligned and spaghetti-type growth of CNTs based on these results.
Catalyst Design Using Nanoporous Iron for the Chemical Vapor Deposition Synthesis of Single-Walled Carbon Nanotubes  [PDF]
Tarek M. Abdel-Fattah,Phillip A. Williams,Russell A. Wincheski,Qamar A. Shams
Journal of Nanomaterials , 2013, DOI: 10.1155/2013/421503
Abstract: Single-walled carbon nanotubes (SWNTs) have been synthesized via a novel chemical vapor deposition (CVD) approach utilizing nanoporous, iron-supported catalysts. Stable aqueous dispersions of the CVD-grown nanotubes using an anionic surfactant were also obtained. The properties of the as-produced SWNTs were characterized through atomic force microscopy and Raman spectroscopy and compared with purified SWNTs produced via the high-pressure CO (HiPCO) method as a reference, and the nanotubes were observed with greater lengths than those of similarly processed HiPCO SWNTs. 1. Introduction Of vital importance to the next generation of aerospace vehicles are structurally resilient, lightweight, and space durable materials and structural health monitoring sensors that can withstand environmental rigors. Carbon nanotubes (CNTs) have shown significant potential in these and a wide variety of other applications on the basis of their remarkable mechanical and electronic properties [1, 2]. CNTs, however, can be produced by several synthesis methods, with some methods better suited for particular applications. Single-walled carbon nanotubes (SWNTs) grown between suspended pillars, for example, have been studied as potential nanoscale power lines [3]. A dominant approach for the synthesis of SWNTs is chemical vapor deposition (CVD), including the high-pressure carbon monoxide (HiPCO) technique [4]. In this paper, we present an alternative CVD method of synthesis of SWNTs for use in composites and aerospace sensor applications. Specifically, we describe the novel incorporation of iron catalysts within a mesoporous material for CNT production. Mesoporous materials (MPMs) are a class of inorganic molecular sieves [5]. Pores in the nanoscale range of 2 to 100?nm make these materials very attractive as shape selective adsorbents or catalysts. Generally, the MPM is prepared in solution by supramolecular assembly of organic molecules as templates with an inorganic precursor. In the original synthesis of MPMs is the formation of rod-like micelles using charged surfactants such as alkyltrimethylammonium surrounded by inorganic species followed by the polymerization of silicates to form the framework of MPMs. The pore size of MPMs can be tuned in the nanosize range based on the number of carbon atoms in the alkyl chain length of surfactants from about 1.6?nm for eight carbon atoms to 3.8?nm for 16 carbon atoms. The pores are separated by silicate walls whose thickness is in the range of 0.8 to 1.6?nm. As-synthesized MPMs have specific crystalline phases that can be controlled
The Influences of H2Plasma Pretreatment on the Growth of Vertically Aligned Carbon Nanotubes by Microwave Plasma Chemical Vapor Deposition  [cached]
Jian Sheng-Rui,Chen Yuan-Tsung,Wang Chih-Feng,Wen Hua-Chiang
Nanoscale Research Letters , 2008,
Abstract: The effects of H2flow rate during plasma pretreatment on synthesizing the multiwalled carbon nanotubes (MWCNTs) by using the microwave plasma chemical vapor deposition are investigated in this study. A H2and CH4gas mixture with a 9:1 ratio was used as a precursor for the synthesis of MWCNT on Ni-coated TaN/Si(100) substrates. The structure and composition of Ni catalyst nanoparticles were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The present findings showed that denser Ni catalyst nanoparticles and more vertically aligned MWCNTs could be effectively achieved at higher flow rates. From Raman results, we found that the intensity ratio of G and D bands (ID/IG) decreases with an increasing flow rate. In addition, TEM results suggest that H2plasma pretreatment can effectively reduce the amorphous carbon and carbonaceous particles. As a result, the pretreatment plays a crucial role in modifying the obtained MWCNTs structures.
A Temperature Window for the Synthesis of Single-Walled Carbon Nanotubes by Catalytic Chemical Vapor Deposition of CH4over Mo2-Fe10/MgO Catalyst  [cached]
Yu Ouyang,Daoyong Li,Weiran Cao,Shaohua Shi
Nanoscale Research Letters , 2009,
Abstract: A temperature window for the synthesis of single-walled carbon nanotubes by catalytic chemical vapor deposition of CH4over Mo2-Fe10/MgO catalyst has been studied by Raman spectroscopy. The results showed that when the temperature is lower than 750 °C, there were few SWCNTs formed, and when the temperature is higher than 950 °C, mass amorphous carbons were formed in the SWCNTs bundles due to the self-decomposition of CH4. The temperature window of SWCNTs efficient growth is between 800 and 950 °C, and the optimum growth temperature is about 900 °C. These results were supported by transmission electron microscope images of samples formed under different temperatures. The temperature window is important for large-scale production of SWCNTs by catalytic chemical vapor deposition method.
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