Electric arc method

Figure 4-2. Example of a production plant for nitric acid from the nitrogen and oxygen of atmospheric air (electric-arc method).

MWCNT was first discovered by arc-discharge method of pure carbon and successive discovery of SWCNT was also based on the same method in which carbon is co-evaporated with metallic element. Optimisation of such metallic catalyst has recently been performed. Although these electric arc methods can produce gram quantity of MWCNT and SWCNT, the raw product requires rather tedious purification process. 

If the sample is a conductor, it is possible to use it as the cathode of a spectral lamp whose principle of operation is identical to that described for hollow cathode lamps (cf. section 14.5 and Fig. 15.3). The device must be sealed before it can be used, which represents a technical constraint. The advantage of this process, which is commonly used for surface analysis, is that it produces spectra with narrow emission lines because atomisation is made at a lower temperature than with the electrical arc method. 

Carbon black containing 15-20% SWNTs was synthesized by the electric arc method in helium atmosphere at a pressure of 0.86 atm using a metallic Co/Ni = 3/1 catalyst (Loutfy et al. 1999). To remove impurities from SWNTs, carbon black... 

Mass-spectrometer date of the hydrogenated carbon nanotubes we have published in (Shulga et al. 2004). These nanotubes for the gas mass-spectrometry were synthesized by the electric-arc method using a nickel-yttrium catalyst. To remove amorphous carbon and the metal catalyst, the primary products containing 10-15 wt% of carbon SWNTs were purified by repeated oxidation in air at temperatures... 

Oxides. Details of an electric arc method for the preparation of pure NbO from Nb2Os and Nb have been reported.517 Reduction of Nb2Os with ammonia in the temperature range 600—1300°C gives the 5-oxynitride at 800 °C, Nb02 between 800 and 820 °C and hexagonal NbN above 820 ° C.518... 

Gold nanorods were prepared by the photochemical procedure of Kim et al. [6]. Gold nanocrystals with an average diameter of 2.5 nm were obtained by the reduction of chlo-roaurate ion (0.55 ml of 25 mM aqueous solution) by partially hydrolyzed tetrakis (hydroxymethyl) phosphonium chloride (THPC) [7], CdSe nanocrystals were prepared by the solvothermal procedure starting with cadmium stearate, selenium and tetralin in toluene [8]. SWNTs prepared by the electric arc method with a Y2O3 + Ni catalyst, were purified by acid and hydrogen treatments [9]. 

Du, F., et al. (2006), The synthesis of single-walled carbon nanotubes with controlled length and bundle size using the electric arc method, Carbon, 44(7), 1327-1330. 

The fullerenes used were synthesized according to the electric arc method, giving a mixture of Qo and C o in the ratio —85 15. Thin films of the fullerene-doped polymer are prepared by spin-coating fullerene and PVK (molecular weight —5x10 ) from solution in toluene (typically 40 mg of fullerene and 1.5 g of PVK in 12 ml of toluene) onto aluminium substrates. The samples are dried in an oven at 100 °C for several hours before use. The film thickness can be varied from 1 to 30 xm, by changing the concentration of PVK and the spin speed. The films are optically clear and air-stable for at least several months. 

The courtship between Haber and the BASF was an intermittently rocky affair, as was the ensuing marriage. The BASF wanted Haber to work only on its electric arc method for combining nitrogen with oxygen Haber demanded that the company also support his efforts to create ammonia. The company eventually agreed, but only out of personal consideration for my wishes, and not out of confidence in the matter itself, as Haber put it later. 

Small electrically heated tungsten coils have also been used experimentally for the formation of acetylene by cracking methaue.80 At 3000° C. and with a time of contact of 0.0004 second a conversion of 86 per cent has been reported as obtainable from coke-oven gas containing 25.5 per cent methane. The results of this experimental work indicate that higher yidds are possible by the electric arc method. 

The electric arc method, which was once used only for small batches of specialty steels, is being utilized more and more in the steel industry. In this process an electric arc between carbon electrodes is used to melt the charge. This means that no fuel-borne impurities are added to the steel, since no fuel is needed. Also, higher temperatures are possible than in the open hearth or basic oxygen processes, and this leads to more effective... 

Some of these have semiconducting properties. The electric-arc method of producing Ceo also loads to a smaller number of fullerenes such as Cjo, which have less symmetrical molecular structures. It is also possible to produce forms of carbon in which the atoms are linked in a cylindrical, rather than spherical, framework with a diameter of a few nanometres. They ate known as buckytubes (or nanotubes). 

In the Birkeland-Eyde process, combination of N2 and O2 was achieved by an electric arc whereby the necessary high temperatures (>3000 K) could be reached. Only small yields of NO were obtained and the waste of electric energy was enormous. Nevertheless, in 1905, the first industrial plant started operation in Norway where electric energy was cheap. Soon BASF also initiated the development of an electric arc method the project was, however, shortly abandoned with the realization of the Haber-Bosch process. 

At the same time, the metal orientation proceeds in interface regions and nanopores of pol5mieric phase which conditions further direction of the process to the formation of metal/carbon nanocomposite. In other words, the birth and growth of nanosize stmctures occur during the process in the same way as known from the macromolecule physics [6], in which Avrami equations are successfully used. The application of Avrami equations to the processes of nanostructure formation was previously discussed in the papers dedicated to the formation of ordered shapes of macromolecules [6], formation of carbon nanostructures by electric arc method [7], obtaining of fiber materials [8]. 

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