Carbon nanotubes laser ablation

It occurs catalytically on the surface of Fe nanoparticles grown from Fe(CO)5. Also, the conventional synthesis of nanotubes by catalytic CVD from acetylene or methane can be formally considered as redox reaction. Nevertheless, the electrochemical model of carbonization (Sections 4.1.1 and 4.1.2) is hardly applicable for CVD and HiPco, since the nanotubes grow on the catalyst particle by apposition from the gas phase, and not from the barrier film (Figure 4.1). The yield and quality of electrochemically made nanotubes are usually not competitive to those of catalytic processes in carbon arc, laser ablation, CVD and HiPco. However, this methodology demonstrated that nanotubes (and also fullerenes and onions (Section 4.3)) can be prepared by soft chemistry" at room or sub-room temperatures [4,5,101]. Secondly, some electrochemical syntheses of nanotubes do not require a catalyst [4,5,95-98,100,101]. This might be attractive if high-purity, metal-free tubes are required. 

Although currently yields obtained in electrochemical synthesis of fullerenes and nanotubes are not yet competitive compared to those prepared via the usual processes (carbon arc, laser ablation, etc.), such procedures are of considerable interest (Kavan et al., 2004). 

Despite the frequent use of arc-discharge and laser ablation techniques, both of these two methods suffer from some drawbacks. The first is that both methods involve evaporating the carbon source, which makes it difficult to scale up production to the industrial level using these approaches. Second, vaporization methods grow CNTs in highly tangled forms, mixed with unwanted forms of carbon and/or metal species. The CNTs thus produced are difficult to purify, manipulate, and assemble for building nanotube-device architectures in practical applications. 

Ka, I. Le Borgne, V. Ma, D. El Khakani, M. A., Pulsed laser ablation based direct synthesis of single-wall carbon nanotube/Pbs quantum dot nanohybrids exhibiting strong, spectrally wide and fast photoresponse. Adv. Mater. 2012, n/a-n/a. 

Moravsky, A.P., Wexler, E.M. and Loutfy, R.O. (2005) in Growth of Carbon Nanotubes by Arc Discharge and Laser Ablation, Carbon Nanotubes Science and Applications (ed. M. Meyyappan),... 

Carbon nanotubes have been studied extensively since their first observation in 1991 by Ijima [1], Several techniques of preparation have been developed such as laser ablation [2], arc electric procedure [3] or decomposition of hydrocarbides [4], The tremendous interest of scientists towards this new class of carbon materials is due to several reasons. First, the electronic properties are of primary importance on a fundamental point of view, but more importantly, potential applications are proposed every day [5], far beyond the use of nanotubes as electron emitters in flat screen as reported some time ago. 

The past decade has led to the detection of new carbon allotropes such as fullerenes26 and carbon nanotubes,27 28 in which the presence of five-mem-bered rings allows planar polycyclic aromatic hydrocarbons to fold into bent structures. One notes at the same time that these structures are not objects of controlled chemical synthesis but result from unse-lective physical processes such as laser ablation or discharge in a light arc.29 It should be noted, on the other hand, that, e.g., pyrolytic graphitization processes, incomplete combustion of hydrocarbon precursors yielding carbon black, and carbon fibers30 are all related to mechanisms of benzene formation and fusion to polycyclic aromatic hydrocarbons. 

The polyaniline was prepared by emulsion polymerization following the procedure outlined in US patent 5,863,465 with DNNSAused as a dopant [22]. Carbon Nanotubes (CNI) manufactured the nanotubes used in the work either by a high-pressure fabrication method (Hipco SWNT) or via laser ablation (Laser SWNT). We found that excellent dispersions of the nanotubes in PANI could be produced by two different procedures. The nanotubes could either be directly sonicated into the PANI solution or first sonicated into xylene and that dispersion afterwards sonicated into the DNNSA-PANI solution. 

In the case of carbon nanotubes (CNTs), numerous syntheses methods have been developed during the last years, for example, the discharge between two graphite electrodes, laser ablation, hydrocarbon decomposition, and catalytic chemical vapor decomposition (CCVD) however, the most applied methods are arc discharge, laser ablation, and CVD [177-179]. 

Kozlov G.I. (2003) Forming of carbon cobweb at the single walls nanotube synthesis in the stream of laser ablation products widening in an electric field. Pisma v JTF, 18, 88-94. (In Russian). 

The synthesis processes for the nanotubes have been continuously refined in the recent years and today, a number of methods are available to synthesize both single and multiwalled carbon nanotubes. These methods include high temperature evaporation using arc-discharge (28-30), laser ablation (31), chemical vapor deposition etc. (32-34). 

SWCNTs exhibit unique physical and chemical properties that make them very attractive candidates for the production of new materials. Carbon nanotubes are made by wrapping up single sheets of graphite, known as graphene, upon themselves to form hollow, straw-like structures. Traditionally, SWCNTs have been prepared by electric arc-discharge, laser ablation and chemical vapor deposition (CVD) methods these techniques produce significant quantities of impurities, such as amorphous and graphitic forms of carbon and encapsulated catalytic metal nanoparticles. 

Stephan was the first to attempted direct synthesis of the B and N multi walled carbon nanotubes (BCN-MWNTs) in 1994 [15-17]. Since then, considerable progress has been made in the synthesis of BCN-MWNTs by different means of arc-discharge [16-18], laser ablation [18-20], piyolysis methods [18,21], and chemical vapor deposition [18,20-24]. Aligned BNC nanotubes have been sueeessfully fabricated by bias assisted hot filament chemieal vapor deposition [27,28]. Up to now, the only existing BCN-SWNTs synthesis was achieved via an... 

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