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LOW-TEMPERATURE FORMATION METHOD OF TUBULES ON ALUMINIUM FOILS
V.I. KODOL.OV, E.SH. SHAYAKHMETOVA, A.A. DIDIK, L.G. MAKAROVA, A.YU. VOLKOV1, E.G. VOLKOVA1
Basic Research-Educational Center Udmurt Scientific Center, Ural Division, Russian Academy of Sciences 222, Gorky St., Izhevsk, 426000, Russia; e-mail: kodol@istu.udm.ru
1 - Institute of metal physics, UrD RAS, Ekaterinburg, Russia
ABSTRACT. The paper is dedicated to the low-temperature synthesis of carbon-metal containing tubules by dehydropolycondensation on the aluminum foils from polyaromatic hydrocarbons (anthracene) in active media with lamellar structure, which are melts of salts. Eutectic melts of aluminum, nickel and sodium chlorides are used as active media. The formation of carbon-metal containing tubules being formed under the reactive medium interaction with the foil surface, the adhesive capability of which increases with the help of electro-chemical preparation of foil surface before synthesis, is determined.
INTRODUCTION
At present carbon micro- and nanostruclures are of great interest among the researchers due to their unique properties connected with their structure and composition. One of the leading trends in modern physico-chemislry is the research of nanomaterials obtained as tubules or nanolubes with characteristic diameters (not more than 100 nm) possessing many uncommon properties, perspective for the development of some technologies [1]. This allows considering carbon tubules as the objects having unique physico-chemical characteristics, which open the wide application range in various fields.
In recent time the method of carbon-metal containing nanotubes obtaining during graphite and metal spraying in electric arc, as well as by the pyrolysis at T>550°C from a gaseous phase is widely used [2,3]. Synthesis of similar products by low-temperature method is actual, one of them is given by the authors of this paper.
EXPERIMENTAL
The process of carbon tubules formation on aluminum foil, on the surface of which the heat-stable oxide AI2O3 is formed, is described in this paper. The foil is given anodic treatment in 20% solution of H2SO4 at 15V and current density ~2 A/dM2.
Aluminum foils thus prepared are hold in synthesis medium consisting of anthracene, AICI3, NaCl and NiCl2 in molar ratio - 1:10:10:2.
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The mixture with foil introduced into it is heated at 150°C till black infusible mass is obtained (approx. 3 hours). Further the foil, and separately the volumetric phase, are treated by water and o-xylene during heating to remove inorganic and organic phases, correspondingly.
The structure of carbon formations obtained is investigated by transmission and scanning electron microscopy. The composition is investigated by X-ray photoelectron spectroscopy on X-ray photoelectron magnetic spectrometer with Al Ka radiation. The spectra decoding is carried out using Bgauss program.
RESULTS AND DISCUSSION
This is the process of low-temperature carbonization (dehydropolycondensation) in the presence of electron-acceptor additive (Lewis acid) decreasing the breaking-off energy of hydrogen atoms, which are AICI3 and NiCb- Sodium chloride performs the function of a substance preventing aluminum chloride sublimation. During the process, especially at the initial stage, the intensive hydrogen chloride evolution is observed.
The possible process mechanism:
coD-op^apm^sccoxoo--
AlClj AlClj
(1) (2) (3) (4) (5)
Nickel chloride is an oxidizer providing the proceeding of stage (3) —►(4) [4]; as a result, nickel particles of small size are formed, which can act as nucleation centers on which carbon formations grow.
Nickel particles being formed near the oxide layer are, likely, localized on its surface (Eb (O2-- Ni) = 1,75 eV, d(Al203-Ni) = 1,87A [5]).
The formation of dark oxide regions, being the oxide layer with carbon formations introduced into it, is observed on washed foil. In separate regions the fragments of volumetric phase, which cannot be removed without sample destroying, are shown up, thus pointing al high adhesion of carbon formations to AI2O3 layer.
The surface structure of the obtained samples is shown in Fig. 1-5. The surface of the initial sample has a porous "cellular" structure, which is analogous to images in Fig.4, 5(1). The pores sizes are 10 - 30 nm. The most part of the carbon structures obtained is disposed parallel or under the angle to the oxide surface (fig. 3(2), fig. 3). Besides, some fraction of tubules, the base of which is fixed on the surface, is observed (fig. 1, 3). The base structure of carbon formation, which is a bundle of carbon nanotubes probably, is shown in Fig. 5(1).
In X-ray electron spectrum of carbon Cls (Fig. 6) the peaks which we refer to graphite
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v.l. KODOLOV. E.SH. SHAYAKHMETOVA. A.A. DIDIK, L.G. MAK.AROVA, A.YU. VOLKOV,
E.G. VOLKOVA
Fig.l. Morphology of base structure, which is shown in Fig.3 (region 1)
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Fig.3. Carbon structure as bundles of nanotu'bes on the base
Fig.4. Carbon structure as a bundle of nanotubes
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V.I. KODOLOV, E.SH. SHAYAKHMETOVA, A.A. DIDIK, L.G. MAKAROVA, A.YU. VOLKOV,
E.G. VOLKOVA
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LLU 'JU¿
Fig.5. Carbon nanotube on oxide layer
E(eV)
Fig. 6. X-ray photoelectron Cls - spectrum or graphite-like products (Eb~284,3 eV), residual bonds of C-H (Eb~285,5 eV), the influxes of low intensity corresponding to C-0 bonds (Eb~288,4 eV) and "carbon-metal" bonds of carbide type (Eb~ 281 eV) are obsei^ed.
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CONCLUSIONS
According to the data obtained it is possible to conclude that carbon nanostructures are formed both in volumetric phase and on the surface of oxide layer as products of low temperature (150°C) dehydropolycondensation of anthracene in the medium A1C13: NaCl: NiCh. Apparently, their growth takes place on nucleation centers, in particular on metal particles (Ni), also localized on AI2O3 layer.
REFERENCES
1. A.V. Eletskii. Carbon nanotubes. In: Uspekhi Fizicheskikh Nauk, 1997, v. 167, N 9, p. 945-972.
2. Ju.E. Lozovik, A.M. Popov. Formation and Growth of Nanostructures - Fullerenes, Nanoparticles, Nanotubes and Cones. In: Uspekhi Fizicheskikh Nauk, 1997, v. 167, N 7, p. 751-774.
3. E.G. Rakov. Methods of Carbon Nanotubes Obtaining. In: Uspekhi Khimii, 2000, v. 69, N 1, p. 41-59.
4. V.I. Kodolov et al. Investigation of aromatic hydrocarbons dehydropoycondensation and carbonization reaction products using X-ray photoelectron spectroscopy and quantum-chemical calculations. In: Analytics and control. 1999. P. 18.
5. A.L. Ivanovsky, G.P. Shveikin. Quantum chemistry in science of materials. Ekaterinburg, UrDRAS. 2000. P. 180.
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