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. twNEW 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 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￾ity (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 precur￾sors for producing high-performance CFs [1–3]. Heat treat￾ment of PAN fiber under tensile load is beneficial to im￾prove fiber quality [4]. Bahl and coworkers pretreated pre￾cursors 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 im￾prove mechanical properties and electrical conductivity of the resultant CFs more than that by any conventional proc￾ess. In this study, PAN-based CFs were coated with carbon film by CVD of acetylene to modify their surface. The re￾sultant 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 To￾ray 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 con￾stantly driven thermal chemical vapor deposition (CVD) process using acetylene as a precursor [10]. Before the ex￾periment 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