NEW CARBON MATERIALS Availableonlineatwww.sciencedirect.com Volume 21. Issue 4, December 2006 Online English edition of the Chinese language journal Science Direct ite this article as: New Carbon Materials, 2006, 21(4): 297-301 RESEARCH PAPER The effect of a chemical vapor deposited carbon film from acetylene on the properties of graphitized PAN-based carbon fibers Ko Tse-Hao*, Lin Jui-Shiang Department of Materials Science and Engineering, Feng Chia University, Taichung, China Abstract: Polyacrylonitrile(PAN)-based carbon fibers(CFs) were coated with carbon film by chemical vapor deposition using acety lene as precursor. The morphologies of the as-received and modified CFs were observed using SEM and AFM, and their mechanical properties, crystalline parameters, and electrical conductivity were measured after graphitization. It was found that the graphitized CFs that were prepared showed excellent mechanical properties(2 GPa for strength and 270 GPa for modulus)and good electrical conductiv- Key Words: carbon fiber; CVD; graphitization 1 Introduction sultant CFs were graphitized to prepare high-performance CFs with excellent mechanical property and good electrical Carbon fibers(CFs)exhibit a very wide range of thermal conductivity. The microstructures and properties of the electrical, and mechanical properties and are widely used in many important fields. Various techniques are needed to graphite CFs were analyzed by X-ray diffraction(XRD), Raman spectra analysis, scanning electron microscopy develop CFs with high tensile strength and high modulus (SEM), and atomic force microscopy (AFM) acrylonitrile(PAN) fibers are the most suitable precur- sors for producing high-performance CFs [1-3]. Heat treat- 2 Experimental ment of pan fiber under tensile load is beneficial to im- prove fiber quality [4]. Bahl and coworkers pretreated pre 2.1 Raw material cursors with CucI to produce high-performance CFs [5,6] Raskovic and Morinkovic investigated stabilization of PAN In this study, PAN-based CFs(T700SC, supplied by To fibers by oxidation with SO2, oxygen, or air and observed ray Ltd, Japan) were used. A single tow contains 12,000 hat sulfur was incorporated into the chemical structure of monofilaments the fiber, which improved the mechanical properties of CFs [7]. Ko et al. modified PAn precursors with cobalt chloride 2.2 Carbon film coating on the surface of CFs increase mechanical properties of CFs and carbon films T700SC bundles were coated with hydrocarbon in a con stantly driven thermal chemical vapor deposition(CVD) In the present study, the effect of modification of CF by process using acetylene as a precursor [10]. Before the ex- chemical vapor deposition( CVD)of acetylene on properties periment was started, the as-received CFs were unsized with and microstructure of the resultant graphitized CFs was organic solvent to remove sizing agents. the resultant CFs discussed. Before this study was carried out, the authors of was mounted on a sample holder and inserted into a furnace, this study assumed that the modification of CFs could im- which was subsequently heated to synthesis temperature and prove mechanical properties and electrical conductivity of then purged with N2 for 5 min. Precursor gas acetylene was the resultant CFs more than that by any conventional proc blown to the furnace at a rate of 50 cm /min to modify CFs ess. In this study, PAN-based CFs were coated with carbon by CVD, and the furnace was maintained in an isothermal film by Cvd of acetylene to modify their surface. The re- state at 950C for 10, 15, 20, 25, and 40 min to yield sam- Received date: 2006-10-12: Revised date: 2006-10-27 Corresponding author. E-mail: thko @fcu.edu. tw
NEW CARBON MATERIALS Volume 21, Issue 4, December 2006 Online English edition of the Chinese language journal Cite this article as: New Carbon Materials, 2006, 21(4): 297–301. Received date: 2006-10-12; Revised date: 2006-10-27 RESEARCH PAPER The effect of a chemical vapor deposited carbon film from acetylene on the properties of graphitized PAN-based carbon fibers Ko Tse-Hao*, Lin Jui-Shiang Department of Materials Science and Engineering, Feng Chia University, Taichung, China Abstract: Polyacrylonitrile (PAN)-based carbon fibers (CFs) were coated with carbon film by chemical vapor deposition using acetylene as precursor. The morphologies of the as-received and modified CFs were observed using SEM and AFM, and their mechanical properties, crystalline parameters, and electrical conductivity were measured after graphitization. It was found that the graphitized CFs that were prepared showed excellent mechanical properties (2 GPa for strength and 270 GPa for modulus) and good electrical conductivity (5×10−4 Ωcm) compared with the unmodified ones. Key Words: carbon fiber; CVD; graphitization 1 Introduction Carbon fibers (CFs) exhibit a very wide range of thermal, electrical, and mechanical properties and are widely used in many important fields. Various techniques are needed to develop CFs with high tensile strength and high modulus. Polyacrylonitrile (PAN) fibers are the most suitable precursors for producing high-performance CFs [1–3]. Heat treatment of PAN fiber under tensile load is beneficial to improve fiber quality [4]. Bahl and coworkers pretreated precursors with CuCl to produce high-performance CFs [5,6]. Raskovic and Morinkovic investigated stabilization of PAN fibers by oxidation with SO2, oxygen, or air and observed that sulfur was incorporated into the chemical structure of the fiber, which improved the mechanical properties of CFs [7]. Ko et al. modified PAN precursors with cobalt chloride to increase mechanical properties of CFs and carbon films [8,9]. In the present study, the effect of modification of CF by chemical vapor deposition (CVD) of acetylene on properties and microstructure of the resultant graphitized CFs was discussed. Before this study was carried out, the authors of this study assumed that the modification of CFs could improve mechanical properties and electrical conductivity of the resultant CFs more than that by any conventional process. In this study, PAN-based CFs were coated with carbon film by CVD of acetylene to modify their surface. The resultant CFs were graphitized to prepare high-performance CFs with excellent mechanical property and good electrical conductivity. The microstructures and properties of the graphite CFs were analyzed by X-ray diffraction (XRD), Raman spectra analysis, scanning electron microscopy (SEM), and atomic force microscopy (AFM). 2 Experimental 2.1 Raw material In this study, PAN-based CFs (T700SC, supplied by Toray Ltd., Japan) were used. A single tow contains 12,000 monofilaments. 2.2 Carbon film coating on the surface of CFs T700SC bundles were coated with hydrocarbon in a constantly driven thermal chemical vapor deposition (CVD) process using acetylene as a precursor [10]. Before the experiment was started, the as-received CFs were unsized with organic solvent to remove sizing agents. The resultant CFs was mounted on a sample holder and inserted into a furnace, which was subsequently heated to synthesis temperature and then purged with N2 for 5 min. Precursor gas acetylene was blown to the furnace at a rate of 50 cm3 /min to modify CFs by CVD, and the furnace was maintained in an isothermal state at 950℃ for 10, 15, 20, 25, and 40 min to yield sam- *Corresponding author. E-mail: thko@fcu.edu.tw
Ko Tse-Hao et al / New Carbon Materials, 2006, 21(4): 297-301 ples, which were labeled as A, B, C, D, and E, respectively 25 mm were used. The electrical conductivity of carbon After this stage, the modified CFs were heat treated up to fibers was measured using a table electric instrument with a 2700C for graphitization. test spacing of 10 mm 2.3 Observation of morphology of CFs 3 Results and discussion The surface morphologies of the modified PAN carbon 3.1 Analysis of surface structure fibers were observed using SEM(S300, Hitachi, Japan) and AFM(Thermo Microscopes Auto Probe Research). With The surface of the as-received carbon fibers is quite respect to AFM observation, a noncontact mode was em- smooth as shown in Fig. 1 (a). The surfaces of modified ployed with a scanning frequency of 2 Hz and a scanning set bon fibers vary according to the CVD times. At the first point of-0 41 to-0.5 um stage of 10 min, there is only little deposition of carbon film on the surface of carbon fibers as shown in Fig. 1(b), with 2.4 Crystalline parameters of CFs irregular shape and small size of 0.01-4um". With CVD times of 15 and 20 min, there is remarkable deposition of Crystalline parameters of carbon fibers were measured us- carbon film on the surface of carbon fibers(Fig. I(c)and(d) ing XRD(MXP-3, MAC Science Ltd, Japan) with Cu Ka The deposition exhibits spherical shape, and there is more radiation. The degree of graphitization of CFs was analyzed accumulation on the surface of carbon fibers. Excess depo- using Raman spectrometer(Renishaw instrument with a Ra- sition appears when the CVd time is 25 min, which leads man imaging microscope system 2000) with an argon ion to cohesion of some carbon fibers, as shown in Fig. 1(e). In laser of 514 5nm line as the incident radiation the stage, it was assumed that carbon spheres on the surface of carbon fibers are overgrown and destroyed, thereby 2.5 Testing of mechanical and electrical properties causing cohesion of carbon fibers. Fig. 1(f shows smooth surface appears on carbon fibers when the deposition time is Mechanical properties of CFs were tested by a single 40 min filament force testing machine(CY-6040A8, CY Ltd, Tai- wan ), in which load cell of 1000 g and cartridge spacing of (b)Mo (c)Modifi d) Modified carbon fiber c (e)Modified carbon fiber D Modified carbon fiber E Fig. I SEM images of(a)as-received carbon fibers and(b-f) their modified forms produced using CVd process with different retention times
Ko Tse-Hao et al. / New Carbon Materials, 2006, 21(4): 297–301 ples, which were labeled as A, B, C, D, and E, respectively. After this stage, the modified CFs were heat treated up to 2700℃ for graphitization. 2.3 Observation of morphology of CFs The surface morphologies of the modified PAN carbon fibers were observed using SEM (S300, Hitachi, Japan) and AFM (Thermo Microscopes Auto Probe Research). With respect to AFM observation, a noncontact mode was employed with a scanning frequency of 2 Hz and a scanning set point of –0.41 to –0.5 µm. 2.4 Crystalline parameters of CFs Crystalline parameters of carbon fibers were measured using XRD (MXP-3, MAC Science Ltd., Japan) with Cu Kα radiation. The degree of graphitization of CFs was analyzed using Raman spectrometer (Renishaw instrument with a Raman imaging microscope system 2000) with an argon ion laser of 514.5nm line as the incident radiation. 2.5 Testing of mechanical and electrical properties Mechanical properties of CFs were tested by a single filament force testing machine (CY-6040A8, CY Ltd., Taiwan), in which load cell of 1000 g and cartridge spacing of 25 mm were used. The electrical conductivity of carbon fibers was measured using a table electric instrument with a test spacing of 10 mm. 3 Results and discussion 3.1 Analysis of surface structure The surface of the as-received carbon fibers is quite smooth as shown in Fig.1(a). The surfaces of modified carbon fibers vary according to the CVD times. At the first stage of 10 min, there is only little deposition of carbon film on the surface of carbon fibers as shown in Fig.1(b), with irregular shape and small size of 0.01–4µm2 . With CVD times of 15 and 20 min, there is remarkable deposition of carbon film on the surface of carbon fibers (Fig.1(c) and (d)). The deposition exhibits spherical shape, and there is more accumulation on the surface of carbon fibers. Excess deposition appears when the CVD time is 25 min, which leads to cohesion of some carbon fibers, as shown in Fig.1(e). In the stage, it was assumed that carbon spheres on the surface of carbon fibers are overgrown and destroyed, thereby causing cohesion of carbon fibers. Fig.1(f) shows smooth surface appears on carbon fibers when the deposition time is 40 min. Fig.1 SEM images of (a) as-received carbon fibers and (b–f) their modified forms produced using CVD process with different retention times
Ko Tse-Hao er al / New Carbon Materials, 2006, 21(4): 297-301 Atomic force microscopy(AFM)was used to further ob- time was 40 min, as shown in Fig. 2(b) and(c). The modified serve the microsurface structure, which indicated the depo- carbon fibers that were produced when the CVd time was tion of a different kind of carbon film on carbon fibers 40 min exhibit rough and densely distributed even islands Fig 2 shows AFM images of the surfaces of the as-received with pellets of approximately 0. 1 um XO.1 um dimensions carbon fibers and the modified ones. Surface morphologies It is proved that the original surfaces of carbon fibers are of as-received fibers are smooth and filled with several strip completely and evenly covered by deposited carbon film, grooves in the direction of the fiber axis in Fig. 2(a). The which, with the increase of deposition time, forms agglom modified carbon fibers that were produced when the Cvd erate on the surface of carbon fibers time was 20 min show nonuniform surface and larger pellets than the unmodified ones that were produced when the CVD Fig2 AFM images of the surfaces of as received carbon fiber and their modified forms (a)as-received carbon fiber, (b)modified carbon fiber C, (c)modified carbon fiber E 3.2 Stacking size and Raman spectra analysis tization. Carbon layer planes are packed side by side to form a basic structure unit(BSU)of graphite fiber 12], and Table 1 summarizes the crystalline parameters of the such structure augments fiber density. In contrast, anothe as-received carbon fibers and their modified forms after factor decreases the density because of the formation of being graphitized at 2700C defects and voids during graphitization Tuinsta and Koenig [13] proposed the first-order Raman Table 1 Crystalline parameters of as-received carbon fibers and spectrum of a graphite single crystal. This spectrum exhib- their modified forms after being graphitize ited a single characteristic line at 1575 cm- that was desig doone Lc /nm La/mR/·l1 nated as G(graphite)band. A second band at 1360 cm was As-received 0.3509 designated as D(defect) band, which becomes equivalent or 0.3449 .76 22.44 even more intense than g band for more disordered solid 0.3480 0.205 The degree of structural order or degree of graphitization(R) with respect to graphite structure is evaluated according to 0.3489 13.26 20.00 0.220 the ratio of integrated intensities of d to G bands (14yThe 0.3511 21.61 0.205 degree of structural order(R)drops, and this drop indicates the pattern of increase of graphitization in carbon materials Microstructural parameters of carbon fibers during heat The degree of structural order of a fiber declines as the eatment were studied by X-ray diffraction and Raman temperature of heat treatment rises[15, 16] spectrum. Scherrer equation was used to calculate the It is now generally accepted that R value shows depend stacking height of graphite planes(Lc, value stacking size) ence on microcrystalline planar size(stack width, La)ac from the 002 diffraction microstructural changes arise from cording to La= 44/R. The stacking width of fiber rapidly microfibril crystallites, showing elongated ribbons at a increases with graphitization temperature, as summarized in graphitization temperature range of 1500-2800C [11. The Table l size of sharp-edged voids among the complex During heat treatment at 2700C, noncrystalline layers three-dimensional interlinked layer planes also increases gradually stack onto a crystalline region. Compared with the with graphitization temperature. The above two factors af- as-received carbon fibers(Lc: 8 nm, La: 23 nm, and R: 0.53) fect the changes in density of graphite fibers during graph their modified forms provide a larger crystalline structure
Ko Tse-Hao et al. / New Carbon Materials, 2006, 21(4): 297–301 Atomic force microscopy (AFM) was used to further observe the microsurface structure, which indicated the deposition of a different kind of carbon film on carbon fibers. Fig.2 shows AFM images of the surfaces of the as-received carbon fibers and the modified ones. Surface morphologies of as-received fibers are smooth and filled with several strip grooves in the direction of the fiber axis in Fig.2(a). The modified carbon fibers that were produced when the CVD time was 20 min show nonuniform surface and larger pellets than the unmodified ones that were produced when the CVD time was 40 min, as shown in Fig.2(b) and (c). The modified carbon fibers that were produced when the CVD time was 40 min exhibit rough and densely distributed even islands with pellets of approximately 0.1 µm×0.1 µm dimensions. It is proved that the original surfaces of carbon fibers are completely and evenly covered by deposited carbon film, which, with the increase of deposition time, forms agglomerate on the surface of carbon fibers. Fig.2 AFM images of the surfaces of as-received carbon fiber and their modified forms (a) as-received carbon fiber, (b) modified carbon fiber C, (c) modified carbon fiber E 3.2 Stacking size and Raman spectra analysis Table 1 summarizes the crystalline parameters of the as-received carbon fibers and their modified forms after being graphitized at 2700℃. Table 1 Crystalline parameters of as-received carbon fibers and their modified forms after being graphitized. No. d002/ nm Lc /nm La /nm R /ID·IG –1 As-received 0.3509 8.07 8.10 0.538 A 0.3449 12.76 22.44 0.190 B 0.3480 12.18 21.66 0.205 C 0.3479 13.57 21.80 0.205 D 0.3489 13.26 20.00 0.220 E 0.3511 12.64 21.61 0.205 Microstructural parameters of carbon fibers during heat treatment were studied by X-ray diffraction and Raman spectrum. Scherrer equation was used to calculate the stacking height of graphite planes (Lc, value stacking size) from the 002 diffraction. Microstructural changes arise from microfibril crystallites, showing elongated ribbons at a graphitization temperature range of 1500–2800℃ [11]. The size of sharp-edged voids among the complex three-dimensional interlinked layer planes also increases with graphitization temperature. The above two factors affect the changes in density of graphite fibers during graphitization. Carbon layer planes are packed side by side to form a basic structure unit (BSU) of graphite fiber [12], and such structure augments fiber density. In contrast, another factor decreases the density because of the formation of defects and voids during graphitization. Tuinsta and Koenig [13] proposed the first-order Raman spectrum of a graphite single crystal. This spectrum exhibited a single characteristic line at 1575 cm–1 that was designated as G (graphite) band. A second band at 1360 cm–1 was designated as D (defect) band, which becomes equivalent or even more intense than G band for more disordered solid. The degree of structural order or degree of graphitization (R) with respect to graphite structure is evaluated according to the ratio of integrated intensities of D to G bands [14]. The degree of structural order (R) drops, and this drop indicates the pattern of increase of graphitization in carbon materials. The degree of structural order of a fiber declines as the temperature of heat treatment rises [15,16]. It is now generally accepted that R value shows dependence on microcrystalline planar size (stack width, La) according to La = 44/R. The stacking width of fiber rapidly increases with graphitization temperature, as summarized in Table 1. During heat treatment at 2700℃, noncrystalline layers gradually stack onto a crystalline region. Compared with the as-received carbon fibers (Lc: 8 nm, La: 23 nm, and R: 0.53), their modified forms provide a larger crystalline structure
Ko Tse-Hao et al / New Carbon Materials, 2006, 21(4): 297-301 unit(Lc: 13 nm, La: 35-39 nm) and a higher degree of even islands and complete interlinking among lattices graphitization(R: 0.20)after heat treatment at 2700C. So, which causes an increase in tensile strength by 20-30% the deposited film on the surface of carbon fibers may A good correlation exists between preferred orientation duce high graphitization of PAN-based carbon fibers be and modulus in carbon fibers: more highly oriented layer ause of its good graphitizability, thereby improving the planes mean higher tensile modulus [18]. All batch fibers degree of graphitization of the resultant carbon fibers af exhibit similar tensile modulus as shown in Fig 4. Therefore heat treatment at 2700C it could be deduced that the deposited carbon film may too thin to control elongation of carbon fibers regardless of 3.3 Mechanical and electrical properties of carbon whether it is uniformly distributed Mechanical properties are the most important properties that determine the performance of carbon fibers. Mechanical properties of the fibers strongly depend not only on the pre cursor but also on heat-treatment conditions, mainly on creases with heat treatment, but decreases beyond 18000 in. temperature. The strength of PAN-based carbon fibers in- Fig 3 shows tensile strength of the as-received carbon fi- bers and their modified forms after 2700C heat treatment Fibers d and e of the modified forms after 2700C exhibit higher tensile strength than those of the as-received carbon fibers and the other modified carbon fibers(a, b and C) after being graphitized, which are attributed to two factors Batches N First, CVD modification with retention of more than 25 min causes carbon film to spread on fibers and fills the surface Fig 4 Tensile of as-received carbon fibers and their modified canals of carbon fibers. It reduces stress and defects. Second forms(A-E)after heat treatment at 2700C e structural unit (such as La and Lc)of carbon fibers is enlarged after the fibers are modified. Before a crack can Fig5 shows resistivity of the as-received carbon fibers propagate through a fiber to cause failure, certain conditions and their modified forms after heat treatment at 2700C must be fulfilled. Crystallite size along one direction of Modified fibers possess lower electrical conductivity than crack propagation must exceed a critical flaw value for fail- the as-received ones after being graphitized. Improvement ure under tension[17]. As shown in Fig. I and Fig. 2, carbon of the degree of graphitization of carbon fibers through film deposited on D and E fibers is more evenly distributed CVD modification results in good electrical conductivity of han A, B, and C fibers, which means that the deposition on graphite carbon fibers the surfaces of A, B, and C fibers cannot completely attain higher lattice thickness and diameter. In contrast, deposition f呈且 2.6 42086420 100 A-2700° C-2700E B-2700°c D-2700° Batches No Batches No Fig5 Resistivity of as-received carbon fibers and their modified orms(A-E)after heat treatment at 2700C Fig 3 Tensile strength of as-received carbon fibers and thei modified forms(A-E)after heat treatment at 2700C
Ko Tse-Hao et al. / New Carbon Materials, 2006, 21(4): 297–301 unit (Lc: 13 nm, La: 35–39 nm) and a higher degree of graphitization (R: 0.20) after heat treatment at 2700℃. So, the deposited film on the surface of carbon fibers may induce high graphitization of PAN-based carbon fibers because of its good graphitizability, thereby improving the degree of graphitization of the resultant carbon fibers after heat treatment at 2700℃. 3.3 Mechanical and electrical properties of carbon fibers Mechanical properties are the most important properties that determine the performance of carbon fibers. Mechanical properties of the fibers strongly depend not only on the precursor but also on heat-treatment conditions, mainly on temperature. The strength of PAN-based carbon fibers increases with heat treatment, but decreases beyond 1800℃. Fig.3 shows tensile strength of the as-received carbon fibers and their modified forms after 2700℃ heat treatment. Fibers D and E of the modified forms after 2700℃ exhibit higher tensile strength than those of the as-received carbon fibers and the other modified carbon fibers (A, B and C) after being graphitized, which are attributed to two factors. First, CVD modification with retention of more than 25 min causes carbon film to spread on fibers and fills the surface canals of carbon fibers. It reduces stress and defects. Second, the structural unit (such as La and Lc) of carbon fibers is enlarged after the fibers are modified. Before a crack can propagate through a fiber to cause failure, certain conditions must be fulfilled. Crystallite size along one direction of crack propagation must exceed a critical flaw value for failure under tension [17]. As shown in Fig.1 and Fig.2, carbon film deposited on D and E fibers is more evenly distributed than A, B, and C fibers, which means that the deposition on the surfaces of A, B, and C fibers cannot completely attain higher lattice thickness and diameter. In contrast, deposition Fig.3 Tensile strength of as-received carbon fibers and their modified forms (A–E) after heat treatment at 2700℃ even islands and complete interlinking among lattices, which causes an increase in tensile strength by 20–30%. A good correlation exists between preferred orientation and modulus in carbon fibers: more highly oriented layer planes mean higher tensile modulus [18]. All batch fibers exhibit similar tensile modulus as shown in Fig.4. Therefore, it could be deduced that the deposited carbon film may be too thin to control elongation of carbon fibers, regardless of whether it is uniformly distributed. Fig. 4 Tensile of as-received carbon fibers and their modified forms (A–E) after heat treatment at 2700℃ Fig.5 shows resistivity of the as-received carbon fibers and their modified forms after heat treatment at 2700℃. Modified fibers possess lower electrical conductivity than the as-received ones after being graphitized. Improvement of the degree of graphitization of carbon fibers through CVD modification results in good electrical conductivity of graphite carbon fibers. Fig.5 Resistivity of as-received carbon fibers and their modified forms (A–E) after heat treatment at 2700℃
Ko Tse-Hao er al / New Carbon Materials, 2006, 21(4): 297-301 4 Conclusions fibers from PAn fibers modified with cobaltous chloride. Mater Sci,1992,27:2429-2436 PAN-based carbon fibers can be modified through depo- 9 Ko T H, Chen C Y. Improvement in the properties of sition of carbon film on their surface using CVd method The modification improves the graphitizability and electri- PAN-based carbon films by modification with cobaltous chlo- de. J Appl Polym Sci, 1999, 74: 1745-1751 cal conductivity of PAN-based carbon fibers. The method is [10 Zheng R T, Cheng G A, Zhao Y, et al. Preparation and charac- beneficial to prepare carbon fibers with excellent mechani- terization of carbon nanoribbons produced by the catalytic cal property and good electrical conductivity hemical vapor deposition of acetylene. New Carbon Materi- References ls,2005,20(4):355-3 [11] Watt W, Perov B V Strong fibers. New York: Elsevier Science, [I] Fizer E PAN-based carbon fibers-present state and trend of the technology from the viewpoint of possibilities and limits [12] Guigon M, Oberlin A, Desarmot G Microtexture and structure to influence and to control the fiber properties by the process of some high-modulus. PAN-based carbon fibres. Fiber sci parameters. Carbon, 1989, 27(5): 621-645 Technol,1984,20(3):177-198 2] Edie DD [13 Tuinstra F, Koenig J L Raman spectrum of graphite. J Chem erties of carbon fibers. Carbon, 1998, 35(4): 345-347 Phys,1970,53:1126-1130 [3] Wang M Z PAN-based carbon fiber. New Carbon Materials, [14] Lespade P, Marchand A, Couzi M, et al. Caracterisation de 1998,13(4):79-79 materiaux carbone par microspectrometrie Raman. Carbon [4 Watt w, Philips L N, Johnson W. High-strength high-modulus carbon fibers. The Engineers, 1966, 221: 815-816 [15 Ko T H. Raman spectrum of modified PAN-based carbon 5] Mathur R B. Infrared spectral studies of preoxidized PAN fi- fibers during graphitization. J App/ Polym Sci, 1996, 59 bres incorporated with cuprous chloride additive. Fiber Sci Technol,1984,20:227-234 [16] Ko T H, Kuo W S, Chang Y H Microstructural changes of (6 Bahl O P, Mathur R B, Dhami T L Modification of polyacry phenolic resin during pyrolysis. J Appl Polym Sci, 2001, 81: 1084-1089 performance carbon fibres. Mater Sci Eng, 1985, 73 [17 Marsh H. Introduction to Carbon Science. Hartnoll Ltd, Corn- [7] Raskovic V, Marinkovic S. Processes in sulfur dioxide treat- [18 Fourduex A, Perret R, Ruland W. Proc. Int. Conf on Carbon ment of PAN fibers. Carbon, 1978, 16(5): 351-357. Fibers, Their Composites and Applications. Plastics Institute, London,1971.57-62
Ko Tse-Hao et al. / New Carbon Materials, 2006, 21(4): 297–301 4 Conclusions PAN-based carbon fibers can be modified through deposition of carbon film on their surface using CVD method. The modification improves the graphitizability and electrical conductivity of PAN-based carbon fibers. The method is beneficial to prepare carbon fibers with excellent mechanical property and good electrical conductivity. References [1] Fizer E. PAN-based carbon fibers-present state and trend of the technology from the viewpoint of possibilities and limits to influence and to control the fiber properties by the process parameters. Carbon, 1989, 27(5): 621–645. [2] Edie D D. The effect of processing on the structure and properties of carbon fibers. Carbon, 1998, 35(4): 345–347. [3] Wang M Z. PAN-based carbon fiber. New Carbon Materials, 1998, 13(4): 79–79. [4] Watt W, Philips L N, Johnson W. High-strength high-modulus carbon fibers. The Engineers, 1966, 221: 815–816. [5] Mathur R B. Infrared spectral studies of preoxidized PAN fibres incorporated with cuprous chloride additive. Fiber Sci Technol, 1984, 20: 227–234. [6] Bahl O P, Mathur R B, Dhami T L. Modification of polyacrylonitrile fibres to make them suitable for conversion into high performance carbon fibres. Mater Sci Eng, 1985, 73: 105–112. [7] Raskovic V, Marinkovic S. Processes in sulfur dioxide treatment of PAN fibers. Carbon, 1978, 16(5): 351–357. [8] Ko T H, Huang L C. Preparation of high-performance carbon fibers from PAN fibers modified with cobaltous chloride. J Mater Sci, 1992, 27: 2429–2436. [9] Ko T H, Chen C Y. Improvement in the properties of PAN-based carbon films by modification with cobaltous chloride. J Appl Polym Sci, 1999, 74: 1745–1751. [10] Zheng R T, Cheng G A, Zhao Y, et al. Preparation and characterization of carbon nanoribbons produced by the catalytic chemical vapor deposition of acetylene. New Carbon Materials, 2005, 20(4): 355–359. [11] Watt W, Perov B V. Strong fibers. New York: Elsevier Science, 1985. [12] Guigon M, Oberlin A, Desarmot G. Microtexture and structure of some high-modulus, PAN-based carbon fibres. Fiber Sci Technol, 1984, 20(3): 177–198. [13] Tuinstra F, Koenig J L. Raman spectrum of graphite. J Chem Phys, 1970, 53: 1126–1130. [14] Lespade P, Marchand A, Couzi M, et al. Caractérisation de matériaux carbonés par microspectrometrie Raman. Carbon, 1984, 22: 375–385. [15] Ko T H. Raman spectrum of modified PAN-based carbon fibers during graphitization. J Appl Polym Sci, 1996, 59: 577–580. [16] Ko T H, Kuo W S, Chang Y H. Microstructural changes of phenolic resin during pyrolysis. J Appl Polym Sci, 2001, 81: 1084–1089. [17] Marsh H. Introduction to Carbon Science. Hartnoll Ltd, Cornwall, 1989. 218. [18] Fourduex A, Perret R, Ruland W. Proc. Int. Conf. on Carbon Fibers, Their Composites and Applications. Plastics Institute, London, 1971. 57–62
