A film composites based on modified multiwalled carbon tubes and polymer (95/5 wt. %) Respectively on paper, without the paper by directional spinning from the liquid phase and graphite. The temperature dependence of the resistivity () in the range T 77-410 K and the corresponding current-voltage charac-teristics. Detected irreversible transitions from semiconducting to metallic conductivity in carbon nono-trubkah and a maximum at T 340 K.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3516

Babaev, A.A.

Filippov, A.K.

Filippov, R.A.

Freidin, A.B.

Khokhlachev, P.P.

Manabaev, N.K.

Nikolaev, Yu.A.

Terukov, E.I.

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 2 No 3, 03NCNN01(3pp) (2013)   2304-1862/2013/2(3)03NCNN01(3) 03NCNN01-1  2013 Sumy State University Temperature Dependence of Resistivity and Current-Voltage Characteristics of the Films of Composites Based on Modified Carbon Multiwalled Nanotubes and Graphite  A.A. Babaev1,*, P.P. Khokhlachev1, Yu.A. Nikolaev2, E.I. Terukov2, A.B. Freidin3, R.A. Filippov3, A.K. Filippov4, N.K. Manabaev5  1 Amirkhanov Institute of Physics, Dagestan Scientific Center, Russian Academy of Sciences, 94, Yaragskogo Str., Makhachkala, 367003 Dagestan, Russian Federation  2 Ioffe Physicotechnical Institute, Russian Academy of Sciences, 26, Politekhnicheskaya Str.,  194027 St.-Petersburg, Russian Federation 3 Institute of Problems of Mechanical Engineering, Russian Academy of Sciences, Vasil'evskii Ostrov, 61, Bol'shoi Pr., 199178 St.-Petersburg, Russian Federation 4 OOO «Plazmas», 1, Akademika Konstantinova Str., 195427 St.-Petersburg, Russian Federation 5 Al-Farabi Kazakh National University,96, Tolebi Str., 050012 Almaty, Kazakhstan   (Received 19 December 2012; published online 29 August 2013)  A film composites based on modified multiwalled carbon tubes and polymer (95/5 wt. %) Respectively on paper, without the paper by directional spinning from the liquid phase and graphite. The temperature dependence of the resistivity ( ) in the range T  77-410 K and the corresponding current-voltage charac-teristics. Detected irreversible transitions from semiconducting to metallic conductivity in carbon nono-trubkah and a maximum  at T  340 K.  Keywords: Current-voltage characteristics, Composites, Carbon multiwalled nanotubes, Graphite.   PACS numbers: 65.80. – g, 81.40. – z, 81.05.uf                                                             * babaev-arif@mail.ru 1. INTRODUCTION  The unique ability of carbon atoms joined together to form a strong and long chains and cycles have led to a huge number of different compounds of carbon. Car-bon multiwalled nanotubes (MCNT) in structure in-termediate between graphene and fullerenes, but many properties do not have anything to do with graphene or fullerenes. This can be considered as independent of the nanotube material with unique mechanical, electri-cal, optical and magnetic properties [1]. Note that many methods of producing nanotubes [2, 3]. The de-crease is accompanied by an increase in the diameter of the nanotube energy steric strain, which should pre-vent the formation of isolated small-diameter nano-tubes [4]. Receive different forms of CNTs is achieved by adjusting the special geometry of the cathode of do-ping elements-catalysts. There is some interest in ha-ving thin nanotubes: they can show unexpected physi-cal properties due to the strong hybridization - and - states. One of the amazing facts is the possibility of significant changes in the properties of nanocomposites (such as changing electrical conductivity) with the in-troduction of the matrix nanoinclusions, which can’t be explained on the basis of the classical theory of compo-site materials. To suggest a possible link the effect of volume fraction of nanoparticles with the formation of transition layers that arise around nanoparticles due to structural changes in the matrix material. Surrounding a nanoparticle modified material increases the effective volume of the particle. Nanoparticles in this case are not only reinforcing additive as stress concentrators, which trigger structural changes in the matrix [5]. Electrical and mechanical properties of the material are determined with a volume fraction and properties of composite inclusions. The volume fraction of the composite nanoinclusions becomes controllable parame-ter that depends on the thermo-mechanical effects on the process step of manufacturing the composite. To separate single-walled tubes that are net conductors from tubes – semiconductors can pass current at high voltages across the array of tubes with different proper-ties. Tube – conductors with heat and burn, and semi-conductors, in which the resistance is higher still. Such an approach is applicable to multi-layer nanotubes, in which the electrons are in contact only with the outer shell. Despite the large number of experimental and theoretical research results, there is currently no clear ideas about the mechanism of the growth of carbon nanotubes are not clearly defined characteristics such as the density of charge carriers, their effective mass, etc. This is primarily due to the weak elaboration of microscopic models of charge transfer. The aim is to study and identify features of the temperature depend-ence of the resistivity (r)-based composites modified MCNT (MCNT / polymer 95/5 wt. %, respectively) ob-tained by directional spinning on paper, without paper and carbon / polymer in the range of T  77 K-410 K and the current-voltage characteristics.  2. PREPARATION OF NANOCOMPOSITES AND EXPERIMENTAL METHOD  For making nanocomposite in PTFE matrix varnish (resin) used MCNT received plasma arc method in the special operating conditions with the average the most common lengths of 100-200 nm and outer diameters of 10-20 nm and the inner diameter of 1.2-3.5 nm. The  A.A. BABAEV, P.P. KHOKHLACHEV, YU.A. NIKOLAEV, ET AL. PROC. NAP 2, 03NCNN01 (2013)   03NCNN01-2 main difference of this method from the usual classical arc plasma technology MCNT growth in the gas phase – the use of a liquid hydrocarbon phase (toluene) at a constant dynamic supply of inert gas argon plasma arc zone, significantly reducing growth temperature MCNT and cheap technical graphite. The advantage of this method – increasing the output of the nanotubes. It turns out the deposit of about 100 g/h at the anode in the conversion of graphite to MCNT to 100 %. Produc-tion and modification UMSNT described in [6, 7]. After modifying MCNT injected into the liquid polymer ma-trix ratio MCNT / polymer 95/5 mas. %, respectively, and stirred for 10 minutes. The resulting stable sus-pension (suspension MCNT in the polymer solution) was used to form the nanocomposite to the substrate by directional (oriented) spinning of the liquid phase. The polymer is selected so that the melting point more 430 K, the decomposition temperature of 630 K, opera-ting temperature up to 410 K, the specific volumetric electrical resistance 109 Om m, electric strength 11-17 kV/mm. The substrate can be any organic or inor-ganic materials, such as paper, on which the film thickness MCNT / polymer corresponds to 30 microns. The films were fixed spring contacts on a mica sub-strate. R The study was carried out in the dynamic mode at a speed of 30-40 K/h temperature range of 77 K-410 K research. Currents and voltages were cho-sen so that there is no heating of the composite. Com-posites with outdoor heated furnace in air.  3. EXPERIMENTAL  The results of the study r composite films based on nanotubes on paper (Fig. 1). Without paper (Fig. 2). And graphite (Fig. 3) And, accordingly, the current-voltage characteristics, which are linear. At the first heating in the range T  77-300 K Fig. 1. There is a slight decrease in the smooth .       Fig. 1 – The temperature dependence of the  of the film thickness of 30 microns based composite MCNT (on paper) and CVC at different temperatures and orientations (x, y) In this temperature cyclic cooling and heating does not change the value of . At T  300 K  increases, reaching a maximum at T  340 K with a subsequent decrease to T  410 K. Cooling from 410 K (A) to 340 K,  composite decreases, there is a metallic conductivity and cooling from 340 K to 77 K  increases slightly. Further temperature cycling in the range of 77 K-410 K  varies in the lower curve (Fig. 1).      Fig. 2 – The temperature dependence of the  of the film based composite MCNT (no paper) and CVC at different tem-peratures and orientations (x, y)  Annealing of the composite at a constant tempera-ture in the range T  300-340 K leads to slow growth , and in the range T  340-410 K decrease r with time. The value of  decreases at different annealing tempe-ratures (Fig. 2)     Fig. 3 – The temperature dependence of the  of a high-resistance film composite graphite / polymer thickness of 40 microns, and CVC  TEMPERATURE DEPENDENCE OF RESISTIVITY… PROC. NAP 2, 03NCNN01 (2013)   03NCNN01-3 (DC and DA) for 40 minutes, depending on tempera-ture. In the intermediate temperature range between the increase and decrease  annealing there is a tem-perature at which  should not change with time dur-ing annealing. These processes are observed for compo-sites on paper and without paper. Note that, like many carbon materials, multi-walled carbon nanotubes are non-ideal structure. They have to be defective, the con-centration of which is different and depends on the method of producing nanotubes. Defects directly affect the concentration of charge carriers, and thus the con-ductivity of the material Note feature of behavior  composite based on graphite (Fig. 3). In the reverse cycle heating - cooling of the film in the range of T  410 K-77 K  varies less than that of the composites based on MCNT. Judging from the temperature dependence of , MCNT fall into two groups. One group r when heating is reduced, which is specific to the semiconductor, the other – r increases, they may be considered as substances with a zero band gap (semimetals) or metals. The carbon atoms in nanotubes are threefold coor-dination, and therefore nanotubes - coupled systems, in which three of the four valence electrons of each atom of carbon form sp2-hybrid orbitals localized and - the C-C, and the fourth part in the formation of a delocal-ized -system as in graphite. These -electrons are weakly bound to their atoms, so they probably are in-volved in the charge transport in the system. In carbon nanotubes there is a relationship between the structure and resistance. In multilayer nanotubes electrons only come into contact with the outer shell. Different shells have different electrical properties due to differences in the electronic structure and charge transfer mechanism in the layers. In semiconducting nanotubes, the band gap is inversely proportional to the diameter of the nanotube. [8-10]. Quantum-chemical prediction was confirmed experimentally [11-14]. Important parameter single-walled carbon nanotubes – chirality, which is determined by the orientation of the graphite plane angle to the axis of the tube. No learned to synthesize nanotubes with desired chiral indices because, if suc-cessful, may be able to produce the elements of elec-tronic circuits with any characteristics. Today chirality hardly detectable using the anti-reflection electron  microscopy. As for quasi graphite, the density of state for MCNT near touching the valence band and the conduction band is well approximated by a linear dependence in a wide energy range. This suggests that multi-walled carbon nanotubes will have physical properties similar to the properties of quasi-graphite. Observed maximum  at 340 K can be explained as follows. When the envi-ronment is cold, the composite material is compressed, creating a lot of gangs of carbon. When heated compo-site parts are expanding, deforming carbon, reducing the number of gangs, increasing resistance. Simulta-neously heating leads to a decrease in the surface den-sity of the nanotubes by the oxidation of the material, the important role played by the iron particles are used as the catalyst. A further reduction of resistance from 340 K to 410 K is accompanied by a transition from semiconducting to metallic conductivity.  4. CONCLUSION  1. The values of  does not change under cyclic  heating and cooling based composites MCNT and graphite in the temperature range 77 K-300 K. 2. In nanocomposites based MCNT detected irre-versible transition from the transition from the semi-conducting to metallic conductivity. 3. Found the maximum value of at 340 K, which is observed during the first heating of the test materials. 4. Cyclic heating and cooling of relatively low re-sistance of the composite graphite-based weakly chan-ges  to 400 K. 5. Value of r can be controlled by annealing based composites MCNT at temperatures T  300 K.   REFERENCES  1. S. Iijima, Nature 354, 56 (1991). 2. P.N. Dyachkov, Carbon nanotubes: structure, properties, and applications. M. binomial (Series: Nanotechnology: 2006). 3. H.W. Zhu, Science, 296, 884 (2002). 4. L.C. Qin, X. Zhao, K. Hirahara, Y. Miyamoto, Y. Ando, S. Iijima, Nature 408, 50 (2000). 5. R.A. Filippov, A.K. Filippov, A.B. Freidin, Saint-Petersburg International Workshop on NanoBiotechnolo-gies, 74 (27-20 November: 2006). 6. A.K. 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Temperature Dependence of Resistivity and Current-Voltage Characteristics of the Films of Composites Based on Modified Carbon Multiwalled Nanotubes and Graphite

Temperature Dependence of Resistivity and Current-Voltage Characteristics of the Films of Composites Based on Modified Carbon Multiwalled Nanotubes and Graphite

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