The changes in the local structure of the fullerenes C60 are studied after high-temperature annealing. Based on the model of atomic configurations obtained by reverse Monte Carlo, the quantitative character-istics of the topological order are founded for the C60 in initial state and after annealing. It is shown that the critical temperature of the beginning of the destruction of the structure of molecular lattice of fuller-enes is 900° C (30 min). At this temperature, a partial breakage of the fullerene molecules occurs. At tem-perature of 1600° C, fully breakage of fullerene molecules and formation of amorphous carbon takes place.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3543

Bilyi, N.M.

Kiryan, I.M.

Ladyanov, V.I.

Merzlyakova, M.A.

Nikonova, R.М.

Rud, A.D.

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 2 No 3, 03NCNN28(4pp) (2013)   2304-1862/2013/2(3) 03NCNN28 (4) 03NCNN28-1  2013 Sumy State University Structure Transformation in Fullerenes C60 at High Temperature Treatment  A.D. Rud1*, I.M. Kiryan1, R.М. Nikonova2†, V.I. Lad’yanov2, N.M. Bilyi3, M.A. Merzlyakova2  1 G.V. Kurdyumov Institute for Metal Physics of NASU, 36 Vernadsky blvd., 03142 Kiev, Ukraine 2 Physical-Technical Institute of the UrB of the RAS, 132 Kirova str., 426000 Izhevsk, Russia 3 Taras Shevchenko National University of Kiev, 60 Volodymyrska str., 01601 Kiev, Ukraine  (Received 15 February 2013; published online 01 September 2013)  The changes in the local structure of the fullerenes C60 are studied after high-temperature annealing. Based on the model of atomic configurations obtained by reverse Monte Carlo, the quantitative character-istics of the topological order are founded for the C60 in initial state and after annealing. It is shown that the critical temperature of the beginning of the destruction of the structure of molecular lattice of fuller-enes is 900° C (30 min). At this temperature, a partial breakage of the fullerene molecules occurs.  At tem-perature of 1600° C, fully breakage of fullerene molecules and formation of amorphous carbon takes place.    Keywords: Structure, Fullerenes, C60, Reverse Monte Carlo, Rings, Bond Angles Distributions.   PACS numbers: 61.48. – c, 81.05.ub, 61.72.Cc                                                           * rud@imp.kiev.ua † RozaMuz@ya.ru 1. INTRODUCTION  Carbon nanomaterials are very promising for prac-tical application. So, a positive effect of fullerene C60 additives to industrial lubricants on wear and tribolog-ical properties of friction units is found in a wide range of pressures and loads [1-3]. Under these conditions carbon nanomaterials undergo to impact of elevated temperatures. Therefore, the investigation of a stability of fullerenes at high temperatures is of great interest. The impact of high temperature annealing in different environments on structure states of fullerenes C60, C70 and their mixes was investigated in a number of works [4-6]. In this paper, we studied the structural changes in local atomic arrangement in the fullerenes C60 occur-ring after high temperature annealing. To investigate the evolution of their structure state experimental (X-ray diffraction, Raman spectroscopy) and modeling (Reverse Monte Carlo) methods were used. Fullerenes C60 were produced in Physico-Technical Institute of Ural Branch of RAS by the traditional arc evaporation of graphite electrodes method with following extraction by toluene in a Soxhlet apparatus. Thermal treatment of fullerite C60 was carried out in covered graphite cru-cibles in CO atmosphere in the Tamman furnace at the different temperatures – 900, 950 and 1600 C during 30 min and at 1600 C during 120 min.  2. TRANSFORMATION OF STRUCTURE OF FULLERENES C60 AT ANNEALING  2.1 Exeperimental results   X-ray study of the structure of fullerenes С60 in the initial state and after high-temperature treatment was conducted in Mo Kα-radiation. Structure factors (SF) of fullerenes C60 after annealing were calculated using X-ray diagrams (Fig. 1) by procedure described in [7, 8]. The structure factor of the initial sample is character-ized by the presence of three strong peaks in positions of s1  0.75 Å-1, s2  1.25 Å-1 and s3  1.44 Å-1 which are typical for the fullerite C60. After high temperature treatment at 900 C, lines s1, s2 and s3 are beginning to expand. At the temperature of 950 C, line s1 complete-ly disappears and the lines s2 and s3 combine into very broad one with the maximum at s'2  1.5 Å-1. The ap-pearance of peak s'2 indicates that a process of break-age of crystal lattice of fullerite C60 is practically com-pleted. Raising the temperature to 1600 ºC leads to the formation of amorphous material with graphite-like type of short-range order.     Fig. 1 – Structure factors (-- experimental, ─ calculated) of fuller-ene C60 in the initial state and after high-temperature treatment  A.D. RUD, I.M. KIRYAN, ET AL. PROC. NAP 2, 03NCNN28 (2013)   03NCNN28-2 Structural changes in fullerenes C60 at the high-temperature annealing were studied by Raman spec-troscopy (Fig. 2). This method reproduces the most es-tablished information about the structural state of the fullerene molecules [9]. After annealing at the temper-ature of 900 C during 30 min Raman spectrum of full-erenes significantly varies from initial one: peaks of fullerenes get broadened and shift from their positions. It indicates a partial breakage of the molecules of full-erenes. Two broad asymmetric peaks on the Raman spectra present with increasing annealing temperature to 950 C, what testifies to complete destruction of in-dividual bucky-balls. At the temperature of 1600° C, two bands with maxima at  1345 cm-1 and 1600 cm-1 which are closed to the positions of the D- and G– bands of disordered graphite, dominate in the spectra (Fig. 2).    Fig. 2 – Raman spectra (   514 nm) of the graphite and fuller-ene C60 in the initial state and after high-temperature treat-ment   2.2 Results of modeling  On the basis of the experimental SF, model configura-tions of atoms corresponding to the real structure of full-erenes С60 in the initial and annealed states were gener-ated using the Reverse Monte Carlo method (RMC) [10]. The cubic simulation box has a half length L  21.39 Å and contains 6696 carbon atoms. Periodic boundary con-ditions are used. To eliminate the imminent overlap of atoms the intersection of the left slope of the first peak of radial distribution function (RDF) curve g(r) with the abscissa was found. So, the minimal approach of carbon atoms in the model was chosen as r(C-C)  1.2 Å. Calculat-ed by RMC procedure model structure factors are plotted at the Fig. 1. Accordance of the calculated structure fac-tors (solid lines) to experimental ones (dashed lines) indi-cates the correspondence of model atomic configuration to real structure of the investigated objects. Model configurations of carbon atoms in initial C60 and annealed at 900 C (30 min) and 1600 C (120 min) ones are shown on Fig. 3. It can be seen that process of destruction of molecules C60 starts at 900 C (Fig. 3, b). At a temperature of 1600 C (Fig. 3, c) molecules of fullerene C60 break down into small fragments of de-formed graphene planes.      Fig. 3 – The configuration of carbon atoms generated for fuller-enes C60: а) initial state; b) 900 C, 30 min; c) 1600 C, 120 min  STRUCTURE TRANSFORMATION IN FULLERENES … PROC. NAP 2, 03NCNN28 (2013)   03NCNN28-3 Bond angles distributions were calculated for ob-tained model atomic configurations of fullerene C60 (Fig. 4). It is characterized by a broad maximum which decomposes into two components with the positions of 110° and 117° (the table values for fullerene C60 are 108  and 120°) for molecules of fullerenes in the initial state. After high temperature treatment at 900 C for 30 minutes, the typical for fullerene C60 peak stays in place, but low intensive broad asymmetric maximum with po-sition of 60° appears. It indicates that displacements of carbon atoms from balanced position take place in the structure of molecules C60 at the annealing process. With increasing temperature to 950 C, peak peculiar to full-erene C60 becomes essentially lower with simultaneous raising the peak at 60 , what suggests the complete de-struction of molecules C60 and formation of amorphous state in the carbon material.    Fig. 4 – The bond angles distribution in carbon atoms config-urations in the fullerene C60 generated by Reverse Monte Car-lo method in the initial state and after high-temperature treatment  Rings distributions (Fig. 5) for the all studied mate-rials were calculated using the criterion of S. King [11]. Rings are formed by connection of atoms within the maximum length of a chemical bond. They define the intermediate range order, which extends not only to the first coordination sphere as it is assumed in defini-tion of short-range order, but to following coordination spheres at a distance of 1-2 nm [12]. Ring size n is de-termined by the number of angles in it. It is clearly seen, that structure of fullerenes C60 in the initial state is characterized by 5- and 6-fold rings which constructed their molecules (Fig. 5). At a tem-perature of 900 C, an essential amount of 3-fold rings appears with simultaneous decrease of the percentage of 5- and 6-fold ones. Enhancing the annealing temper-ature to 950 C results in increasing the percentage of 3- fold rings what indicates the destruction of the full-erene molecules and formation of amorphous structure. At the 1600 C reverse changes start to be realized: the percentage of 3-fold rings decreases with simultaneous rising of 5-and 6-fold ones. The amount of 5- and 6-fold rings is growing with extension of expose at this tem-perature to 120 min, what pointed to partial graphiti-zation process of amorphous material.    Fig. 5 – Rings size distribution n (n - number of edges) in the structure of fullerenes in the initial state and after high-temperature treatment  3. CONCLUSIONS  Structure transition in fullerene C60 from the crys-talline state to amorphous during annealing was recon-structed using Reverse Monte Carlo procedure. Quanti-tative characteristics of topological order in the distri-bution of carbon atoms were established. It was found that in the early stages of heat treatment (T  900 C for 30 min) the partial destruction of C60 molecules and disordering the crystal lattice of fullerite C60 take place. The annealing  at 950 C for 30 min results in the total breakage of the fullerene molecules followed by the formation of amorphous structure of carbon with graphite-like type of short-range order with increasing temperature to 1600 C.  AKNOWLEDGEMENTS  This work was partially supported by the joint project of NAS of Ukraine - SB RAS (#03-09-12) and by the Pro-gram of the Presidium of the UrB RAS (#12-Т-2-1015).     A.D. RUD, I.M. KIRYAN, ET AL. PROC. NAP 2, 03NCNN28 (2013)   03NCNN28-4 REFERENCES  1. D.G. Tochil’nikov, B.M. Ginzburg. Technical Physics. 44, 700 (1999). 2. B.M. Ginzburg, M.V. Baidakova, O.F. Kireenko, et al. Technical Physics. 45, 1595 (2000). 3. A.I. Komarov, V.I. Komarova, A.D. Rud, et al. Surface Engineering and Applied Electrochemistry. 47, 18 (2011). 4. I. Mochida, M. Egashira, H. Koura et al. Carbon. 33, 1186 (1994).  5. V.I. Lad’yanov, R.М. Nikonova, M.A. Merzlyakova et al. Perspectivnye Materialy. 9, 165 (2010), (in Russian). 6. R.M. Nikonova, M.A. Merzlyakova, V.I. Lad´yanov et al. Inorganic materials: Applied Research. 3, No 1, 44 (2012). 7. A.D. Alekseev, G.M. Zelinskay, A. Ilinskii et al. Physics and technology of high pressure. 18, No3, 35 (2008) (in Russian). 8. A.D. Rud, N.I. Kuskova, L.I. Ivaschuk, L.Z. Boguslavskii and A.E. Perekos, Synthesis of Carbon Nanomaterials Us-ing High-Voltage Electric Discharge Techniques. in Nano-materials (Ed. M.M. Rahman) (Rije-ka, Croatia: InTech: 2011)  9. S. Amer. Maher Raman spectroscopy, fullerenes and nano-technology. (USA, Published by the royal society of chem-istry: 2010). 10. R.L. McGreevy, L. Pusztai, Molecular Simulation 1, No6, 359 (1988). 11. S. Le Roux, V. Petkov, J. Appl. Cryst. 43, 181 (2010). 12. C.C. Wang, C.H. Wong. Journal of alloys and compounds. 509, 10222 (2011).  

Structure Transformation in Fullerenes C60 at High Temperature Treatment

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