Asgar, M A

Hossain, T

Rashid, M A

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Indian J. Phys. 70A (5), 575-580 (1996)I J P  A— an international journalTo study the effect of catalyst on graphitization of anthracene and phenanthrene by X-ray diffractionM A Rashid, M A Asgar and T HossainDepartment of Physics, Bangladesh University of Engineering Sc Technology, Dhaka-1000, BangladeshReceived 26 September 1995, accepted 12 February 1996Abstract : Some partially pyrolyzed aromatic organic composite samples have been studied by X-ray diffraction method. Interlayer spacing, Miller indices, ralative intensity and integral widths of the diffraction lines have been calculated. The interlayer spacing is found to decrease as the amount of catalyst is increased The result is explained as an indication of increasing degree of graphitizability with the addition of A1C1 3 as catalyst.Keywords : Catalyst, graphitization, interlayer spacing PACS No. : 61 50 Ks1. IntroductionThe history of X-ray studies on carbon and graphite is closely linked with the development of theories and experiments in the field of X-ray diffraction. Graphite is one of the first substances investigated by X-ray diffraction. Ewald et al [1] demonstrated the hexagonal symmetry of a graphite single crystal by means of a Laue photograph and concluded Irom a qualitative interpretation that the number of nearest neighbours should be different from that in diamond. Bragg et al [2] measured the first interlayer spacing. Debye and Scherrer [3,4] and Hull [5] made the first attempt to determine the crystal structure from powder diagrams. However, Debye and Scherrer found the correct structure of the graphitic layers but gave a wrong sequence for the layer stacking, whereas Hull found the right sequence for the layer stacking but with a wrong structure for the layers. The correct structure of the hexagonal form was first published by Hassel and Mark [6], followed shortly by Bernal [7]; the structure of the rhombohedral form was determined rather late by Upson and Stokes [8].The main structural difference between amorphous carbon and graphite is due to their different sizes of ordered domains and not in the arrangement of atoms within these© 1996IACS576 M A Rashid, M A Asgar and T Hossaindomains. The concept of the crystallite size as the main cause of the line broadening in amorphous carbons has been predominant in most of the early works.The gradual transition from the random layer structure to the graphite lattice was ~ first interpreted quantitatively by Franklin [9] and in a somewhat different way by Houska and Warren [10].Many workers, such as Hofmann and Wilm [11] and Bacon [12,13] have published information on the variation with crystalline size of the interlayer spacing of graphite. Franklin [9], in her studies of both non-graphitic and graphitic carbons, concludes that the measured interlayer spacing are really only mean values. She suggests that to a first approximation, the groups of oriented and disoriented layers in a graphitic carbon retain respectively the spacings of 3.354 A and 3.44 A, which are characteristics of highly crystalline graphite and non-graphitic carbon.In the present investigation an attempt has been made to study inter layer spacing, Miller indices, relative intensity and integral widths of the diffraction lines by X-ray diffractometer of simple aromatic compounds with AICI3 as additives. By these parameters, we can as.sess the degree of graphitization.2. Experimental2.1. Sample preparation :Contrary to the normal technique of preparing pure carbons by heating organic materials close to the graphitization temperature, this is done at relatively low temperature from the organic aromatic samples anthracene and phenanthrene, both without and with AICI3 as catalyst in different mole ratios. These substances are carbonized partially by heating to 400°C and 420°C respectively for 4 hours by scaled tube technique using solenoidal tubular furnace. The resulting carbons are studied by X-ray diffraction.The samples were crushed into fine powder by using pestle and mortar. The sample on a glass slide was then placed into the diffractometer (Model No JDX-8P, JEOL Co. Ltd., Tokyo, Japan). Different diffraction patterns are obtained by using an automatic recorder. The parameters [14] used for the identification of the composite samples are :(i) The spacing between the phases of atoms in the crystals 'd \(ii) The intensities of the X-ray reflections from the corresponding phases 7 \(iii) The Miller indices (hkl) values and(iv) The integral width of the diffraction lines *W\3. Results $nd discussionIn the graphitic carbon, the extent of ordering associated with increasing order of graphitization can be estimated from X-ray diffraction pattern. Whatever be the degree of graphitization, diffuse bands can be identified. These diffused bands have angular positions that correspond roughly to the respective diffractive lines of the gtaphi'c (001, 002, etc) [Figures 1 and 2].577The intermediate stage, between disordered state of non-graphitic carbon and the ordered state of graphite, can be thought of as small layers of graphite-like structures which are stacked in parallel groups but not mutually oriented. From the shape of the diffused bands that correspond to the spectral lines of indices (/>*/) of ordered graphite we can estimate the extent of ordering [9],In an attempt to produce an alternating structure, the variation of the apparent interlayer spacing with the degree of graphitization in the graphitizing carbons and itsTo study the effect of catalyst on graphitization etcFigure I. Intensity patterns of XRD of carbonised composite samples and A1C13 in different proportions-comprising of anthracene70A(5)-5578constancy in both the non-graphitic carbons and in graphite, the different shapes of (001), (002), (003) and (004) lines and the apparent interlayer spacings, are to be taken into account.The effect of catalytic agent (AICI3) on the graphitizing tendency is investigated from the shape of the bands [15,16]. It is observed that with increasing amount of A1C13, the sharpness of the diffraction lines (hkt) increases, the areas under the peaks representing theA# A  R a s h id , M  A  A s g a r  a n d  T  H o ss a in» » 1 » 1 « * - I * . ,F ?  k? is5 5 9 2?  so5 i ?  3 9 3 92 • --------Figure 2. Intensity patterns of XRD of carbonised composite samples comprising of pheoanthrene and A1C13 in different proportions.T o  s tu d y  th e  e f fe c t o f  c a ta ly s t  o n  g ra p h itiz a tio n  e tc 579number of atoms contributing to the scattering of X-rays and the widths of the -peaks representing the radii of the spheres within which the atoms are distributed.Since the magnitudes of widths of different peaks are different, the estimation of the widths of the peaks are made by taking the ratios of the area under each peak by the corresponding height. Representative data of crystallographic parameters of composite samples from anthracene are shown in the following table (Table 1).Tabic 1. Crystallographic parameters of composite samples from anthracene.Sample No. of obs. Angle (2 0) in degreedin  A Relativeintensityhkl width (W) in mm1 9.65 9.1544 100 001 4.142 18.15 4.8818 2 002 0.673 19.30 4 5934 16 10632:00 4 21.25 41761 4 1.115 25.02 3.5547 10 1546 25.90 3.4359 16 003 1.977 29.21 3.0537 4 1.238 36.65 24490 1 004 1.331 9.72 90886 100 001 2.332 18.20 4.8685 5 002 1.093 19.41 4 5677 25 0.8832:1 4 21.35 4 1568 70.895 25.30 3.5160 16 1.146 25.95 3 4294 8 003 0.787 29.35 3 0394 7 1.008 36.75 2 4426 2 004 1.001 9.75 9.0607 100 001 1.342 18.30 4.8422 3 002 0.643 19.40 4.5700 26 0.7832:2 4 21.4041472 7 0705 25.40 3.5024 19 0.546 26.00 3.4229 6 003 0.717 29.42 3.0324 9 0.888 36.90 2.4330 1 001 060The (hkl) lines become sharper as the degree of graphitization increases which is associated with the increase in the number of oriented layers. Sharpening of the bonds corresponds to the reduction of the radii of the spheres within which the atoms are distributed. The diffraction data, therefore, indicates a trend towards graphitization with increasing amount of the catalytic agent. This is in agreement with the observations made using DTA and TGA [17] and IR spectroscopy.580 M A Rashid, M A Asgar and T Hossain4. ConclusionWhile the interlayer spacing is constant at 3.44 A in the non graphitic carbons and at 3.354 A in graphite, the apparent inter-layer spacing in the graphitic carbons decreases with increasing graphitization. This apparent interlayer spacing is in reality a mean value. In all graphitic carbons, whatever be the degree of graphitization, the small groups of orientated and disorientated layers within the parallel layer packets retain certain structural characteristic of crystalline graphite and of the non-graphitic carbons respectively. Among the orientated layers, the interlayer spacing is constant and is always equal to that in graphite, which is 3.354 A,The structure of the graphitic carbons is the simplest which is found to be consistent with all the experimental results. We can see that the interlayer spacing decreases with the increasing amount of catalyst. This indicates an increase in magnitude of graphitizability. Measurements of the width of different diffraction lines show that there is a mixture of at least two interlayer spacing in the graphitic carbons. We are, therefore, led to the conclusion that the graphitic carbons contain a mixture of oriented and disoriented layers, the spacing of the latter being greater than that of the former.References[ 11 P P Ewald, Sitz-Bar Math-Naturw and K1 Bayer Akad Wiss Muenchen 325 (1914)[21 W  H  B r a g g  and W  L  B r a g g  eds X-ray and Crystal Structure 3rd edn (London Bell & Sons) p 174(1918)PI P Debye and P Sherrer Z Physik. 17 277 (1916)tfl P Debye and P Sherrer Z Physik. 18 291 (1917)[5J A W Hull Phys. Rev. 10 661 (1917)[6) O Hassel and H Marie Z Physik 25 317 (1924)P] J D Bernal Proc. Roy. Soc. (London) A106 749 (1924)[8] H Lipson and A R Stokes Proc. Roy. Soc. (London) A181 93 (1942)[9] RE Franklin Acta Cryst. 4 253 (1951)[10] C R Houska and B E Warren J. Appl. Phys. 25 1503 ( 1954)[11] U Hofmann and D Z Wilm Elektrochem. 42 504 (1936)[12] G E Bacon Acta Cryst. 3 137, 320 (1950)[13] GEBacon Acta Cryst. 4 558, 561 (1951)[14] Jahangimagar Review Part A 16,41(1992)[15] A Tomita and H Yamashita Fuel 72 699 (1993)[IQ N Zotov, H Boysen, F Frey, T Metzger and E Bom J. Phys. Chem. Solids 55 145 (1994)[17] M A Rashid, T Hossain and M A Asgar Thcrmochim. Acta 259 263 (1995)

To Study the Effect of Catalyst on Graphitization of Anthracene and Phenanthrene by X-Ray Diffraction

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To Study the Effect of Catalyst on Graphitization of Anthracene and Phenanthrene by X-Ray Diffraction

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