UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2007 Meeting


Section: Solid State Physics and Materials Science


Title:
SANS study of structural change of the coal tar pitch additivated with nanotubes under heat treatment.


Authors:
I. Iona, Y. Kovalev, C. M. Mitud


Affiliation:
1-Carbon Materials Laboratory , National Institute for Research and Development in Electrical Engineering, Romania

2-Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980Dubna, Russia

3-Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia

4-Institute of Space Sciences, Romania


E-mail
ionioanamitu@yahoo.com ionrausioana@icpe-ca.ro


Keywords:
carbon materials, nanotubes, SANS


Abstract:
In the present work SANS, EM, OM and XRD are used to reveal the structural changes of coal tar pitch (CTP) during the first carbonization under the addition of different types of additives: 1,5 % (wt.) single (SWNT), multiwalled carbon nanotubes (MWNT) and carbon nanofibres (CNF). The addition of nanotubes fluidized the system during the pyrolysing process and increased the temperature of mesophase formation. In contrast, the CNF impeded the mesophase formation at this temperature (Fig. 1c).The sizes of crystalline isochromatic areas were strongly influenced by the size of the additive (Fig. 1a, 1b). The result of SANS measurements is interpreted by the Unified Approximation Method. The proposed model consists in two structural levels: BSU (basic structural units) and clusters which present surface fractal properties. The surfaces roughness depends on the type of the additive; and it’s rougher with increasing of the additives size. The clusters diameters were strongly influenced by the type (size) of the additive, the nanotubes decreased the diameters of clusters from 475 Å for CTP to 428 Å for SWNT and 447 Å for MWNT, since the CNF had opposites effect increased it to 648 Å. The additive effect was negligible at small length scales and became visible at large lengths scales, increasing the crystalline content in volume and quality, improve in this way the electric conductive properties of materials. Fig. 1. OM for the CTP with SWNT (a), MWNT (b) CNF (c), 300 X magnification. d. Proposed model for carbonized CTP. References: 1. Beaucage G. J. Appl. Cryst.1995, 28:717-729 2. Pasuk I., Banciu C., Rimbu G.A., Ion I.. Romanian Reports in Physics, 2004, 56(3):320-327. 3. Ion I., Yu. Kovalev, C. Banciu, I. Pasuk. Journal of Optoelectronics and Advanced Materials 2006; 8(2):624-630. 4. Ion I., Y. Kovalev, A. Kuklin, I. Pasuk. Poverhnost.. 2006; 6:84-88.