NEW CARBON MATERIALS Availableonlineatwww.sciencedirect.com Volume 24. Issue 1. March 2009 Online English edition of the Chinese language journal Sciencedirect Cite this article as: New Carbon Materials, 2009, 24(1): 83-88 RESEARCH PAPER Preparation and characterization of pitch-based carbon fibers Arshad hussain wazir* Lutfullah Kakakhel National Centre of Excellence in Physical Chemistry, University of Peshawar, Peshawar-25120, Pakistan Abstract: A petroleum pitch was heated at 420 C for 7 h in nitrogen to prepare a carbon fiber precursor with a softening point of 295 C. The precursor was successfully melt-spun into fibers through a circular nozzle of a monofilament spinning apparatus, and these were then stabilized at 320C in air and finally carbonized at 1000"C in nitrogen to produce carbon fibers. SEM, TGA, FT-IR, and XRD were performed to characterize the petroleum pitch, the precursor, the as-spun fibers, the stabilized fibers, and the carbon fibers. It is found that the precursor contains 70.5% mass fraction of mesophase that is aligned upon spinning, and aliphatic side chains that are benefici to spinning. The carbon fibers have a radial core structure with a linear and bent type anisotropic texture. The maximum tensile strength of the carbon fiber is 650 MPa Key Words: Precursor pitch, Carbon fiber, Photomicroscopy, X-ray diffractometry 1 Introduction ing carbon fibers was also used by Fumitaka et al. 2.How- ever, the latter investigations also focused on studying the Carbon fibers are considered to be high strength materi- melt spinning of a synthetic isotropic pitch containing als having great importance in a variety of specialized ap mesophase spheres to produce carbon fibers with high com- cations, such as aerospace, automobile, chemical industry pressive strength general engineering, missile, nuclear field, reinforcement in composite materials, and textile. The importance of these ma The present work deals with the conversion of Pakistani terials in the above mentioned applications is based on their petroleum pitch obtained from Attock Refinery Limited properties, such as high strength, high stiffness, dimensional (ARL), Rawalpindi, Pakistan, into a spinnable pitch by the mal condensation, which is melt-spun to produce carbon fibers stability, low coefficient of thermal expansion, biological The aim of this study is focused on optimizing the operating compatibility, and fatigue resistance!l-21. They can be classified according to their precursors/3-s) into polyacrylonitrile conditions for melt-spinning of the precursor pitch. The de- (PAN)-based carbon fibers, rayon-based carbon fibers, and fibers using FTIR, XRD, and optical microscopy is also pe. tailed analysis of the precursor pitch and melt-spun carbon formed Pitch-based carbon fibers can be further classified into high performance carbon fibers(HPCFs)and general purpose 2 Experimental carbon fibers(GPCFs)according to their mechanical proper ies, which are prepared, respectively, from optically anisot- 2.1 Materlals ropic pitch and isotropic pitch- Petroleum pitch was indigenously provided by Atto Wang et al. reported the preparation of pitch fibers Refinery Limited(ARL), Morgah, Rawalpindi, Pakistan. Or- from petroleum pitch. They carried out an extensive optimiza- ganic solvents, such as benzene and quinoline, used were all tion of the experimental conditions to obtain hollow fibers of analytical grade reagents(Merck Company) from mesophase pitch and found that die-swell was the maj factor affecting the properties of the final product. Similarly, 2.2 Preparation of precursor plt Park et al. used an improved method for the production of A precursor pitch was prepared by thermal condensation carbon fibers. In this case, the precursor pitch was melt-spun of 100 g petroleum pitch at 420oC for 7 h in a stirring reac- by means of pressurized nitrogen through specialized gadgets which was ultimately carbonized into the desired carbon fibers tor under nitrogen flow. The soluble and insoluble fractions of the precursor pitch were separated by soxlet extraction using at the elevated temperatures. The same methodology for mak benzene and quinoline as solvents. The product yield was eceived date: 17 December 2008: Revised date: 3 March 2009 CopyrightC2009, Institute of Coal Chemistry, Chinese Academy of Sciences. Published by Elsevier Limited. All rights reserved. DO:Io.lol61872-5805(0860039-6
NEW CARBON MATERIALS Volume 24, Issue 1, March 2009 Online English edition of the Chinese language journal Cite this article as: New Carbon Materials, 2009, 24(1):83–88. Received date: 17 December 2008; Revised date: 3 March 2009 *Corresponding author. E-mail: arshkhpk@yahoo.com/arshadwaziri@gmail.com Copyright©2009, Institute of Coal Chemistry, Chinese Academy of Sciences. Published by Elsevier Limited. All rights reserved. DOI: 10.1016/S1872-5805(08)60039-6 RESEARCH PAPER Preparation and characterization of pitch-based carbon fibers Arshad Hussain Wazir*, Lutfullah Kakakhel National Centre of Excellence in Physical Chemistry, University of Peshawar, Peshawar-25120, Pakistan Abstract: A petroleum pitch was heated at 420 o C for 7 h in nitrogen to prepare a carbon fiber precursor with a softening point of 295 o C. The precursor was successfully melt-spun into fibers through a circular nozzle of a monofilament spinning apparatus, and these were then stabilized at 320 oC in air and finally carbonized at 1000 oC in nitrogen to produce carbon fibers. SEM, TGA, FT-IR, and XRD were performed to characterize the petroleum pitch, the precursor, the as-spun fibers, the stabilized fibers, and the carbon fibers. It is found that the precursor contains 70.5% mass fraction of mesophase that is aligned upon spinning, and aliphatic side chains that are beneficial to spinning. The carbon fibers have a radial core structure with a linear and bent type anisotropic texture. The maximum tensile strength of the carbon fiber is 650 MPa. Key Words: Precursor pitch, Carbon fiber, Photomicroscopy, X-ray diffractometry 1 Introduction Carbon fibers are considered to be high strength materials having great importance in a variety of specialized applications, such as aerospace, automobile, chemical industry, general engineering, missile, nuclear field, reinforcement in composite materials, and textile. The importance of these materials in the above mentioned applications is based on their properties, such as high strength, high stiffness, dimensional stability, low coefficient of thermal expansion, biological compatibility, and fatigue resistance[1-2]. They can be classified according to their precursors[3-5] into polyacrylonitrile (PAN)-based carbon fibers, rayon-based carbon fibers, and pitch-based carbon fibers. Pitch-based carbon fibers can be further classified into high performance carbon fibers (HPCFs) and general purpose carbon fibers (GPCFs) according to their mechanical properties, which are prepared, respectively, from optically anisotropic pitch and isotropic pitch[6-9]. Wang et al.[10] reported the preparation of pitch fibers from petroleum pitch. They carried out an extensive optimization of the experimental conditions to obtain hollow fibers from mesophase pitch and found that die-swell was the major factor affecting the properties of the final product. Similarly, Park et al.[11] used an improved method for the production of carbon fibers. In this case, the precursor pitch was melt-spun by means of pressurized nitrogen through specialized gadgets, which was ultimately carbonized into the desired carbon fibers at the elevated temperatures. The same methodology for making carbon fibers was also used by Fumitaka et al.[12]. However, the latter investigations also focused on studying the melt spinning of a synthetic isotropic pitch containing mesophase spheres to produce carbon fibers with high compressive strength. The present work deals with the conversion of Pakistani petroleum pitch obtained from Attock Refinery Limited (ARL), Rawalpindi, Pakistan, into a spinnable pitch by thermal condensation, which is melt-spun to produce carbon fibers. The aim of this study is focused on optimizing the operating conditions for melt-spinning of the precursor pitch. The detailed analysis of the precursor pitch and melt-spun carbon fibers using FTIR, XRD, and optical microscopy is also performed. 2 Experimental 2.1 Materials Petroleum pitch was indigenously provided by Attock Refinery Limited (ARL), Morgah, Rawalpindi, Pakistan. Organic solvents, such as benzene and quinoline, used were all of analytical grade reagents (Merck Company). 2.2 Preparation of precursor pitch A precursor pitch was prepared by thermal condensation of 100 g petroleum pitch at 420 o C for 7 h in a stirring reactor under nitrogen flow. The soluble and insoluble fractions of the precursor pitch were separated by soxlet extraction using benzene and quinoline as solvents. The product yield was
Irshad Hussain Wazir et al. /New Carbon Materials, 2009, 24(1): 83-88 and the O content was calculated by subtracting the sum of C, Motor Thermocouple Thermogravimetric analysis(TGA 1640, Stanton Red- Gas outlet gen atmosphere to find an optimum stabilization temperature or to measure the thermal stability of the samples The polished section on glass slide of the precursor pitch and the longitudinal sections of the melt-spun fibers were ob- Controller Furnace served under a polarized-light microscope (Olympus Model-CX2IFSI Philippine, Japan). The melt-spun fibers were also examined by Scanning Electron Microscope Heating (FE-SEM S-4700, Hitachi, Japan) Pressure Infra Red Spectroscopy (FT-IR Spectrometer, model 2-4 MPa Perkin Elmer 16pc) was used to characterize the functional groups of both the petroleum pitch and the precursor pitch and D=0.4 mm Pitch fiber extracted mesophase pitch The precursor pitch and melt spun fiber samples in pow der form were used in the X-ray diffraction(XRD) analysis The XRD patterns of the samples were obtained by a diffrac Winding speed(150-250 m/min) tometer(JEOL X-ray diffractometer, model JDX-73)using Mn-filtered Cu-Ka as radiation Fig. I Schematic diagrams of the reactor and the melt-spinning ap For tensile strength measurements, 2.5 cm sample was paratus loaded and measured by a tester with a 150 g load and at a cross head speed of 2.5 mm/min. An average was taken calculated by applying the equation(1) from the five tests on the bases of JIS R 7601 method Yield (%)=Mass of the precursor/ Mass of the petroleum pitch x100 (1)3 Results and dls The schematic diagrams of the reactor and the 3.1 Preparation of carbon fibers melt-spinning apparatus are shown in Fig 3.1.1 Preparation of precursor pitch 2.3 Preparation of carbon fibers Properties of the precursor pitch are summarized in Table A laboratory scale apparatus was used to melt-spin the he soluble parts are considered to be isotropic in nature, precursor pitch into carbon fibers under pressurized nitrogen whereas the insoluble parts are anisotropic. During heat f2 kg/cm through a mono-hol ole spinneret(D=0. 4 mm)at a treatment of pitch at 400-450C, anisotropic spheres called spinning temperature of 335C. The as-spun fibers were sta- mesophase are developed in the isotropic pitch matrix like bilized at 320 C for 2 h in air with a heating rate of 2 C/min. liquid droplet inside a liquid, as described by Brooks and The stabilized fibers were further carbonized at 1000C for 1 Taylor3. Their optical anisotropy and micrometer scale h under nitrogen flow in a tube furnace at a heating rate of 5 structure can be well observed under a polarized light micro- "C /min. The carbon yield was calculated by applying the scope on the polished sections. These spheres coalesce and equation(2) form a mosaic-like nematic liquid-crystal structure, which is Carbon yield (%)Mass of the carbonized fibers/ still plastic and called bulk mesophase with a prolonged Mass of the stabilized fibersx 100. (2) heat treatment time. With furthermore heat treatment,the mesophase develops into highly graphitizable carbon, and the 2.4 Characterization mobility of the individual molecule is confined because of the Metler FP 90 apparatus(Metler Toledo AG, Switzerland, igidity of the highly ordered solid phasells) ASTMD3140)was used to determine softening point of sam- Table 1 Properties of precursor pitch ples Solubility w/% Benzene soluble(BS), benzene insoluble(BI), benzene Softeningpoint t/C insoluble-quinoline soluble (BI-QS), and quinoline insoluble (QI) fractions of the pitches were measured by the soxlet ex traction BS: benzene soluble, Bl-QS: benzene insoluble-quinoline soluble, QI The contents of C, H, and N in samples were determined quinoline insoluble by an elemental analyzer (EA 1110, CE Instruments, Italia
Arshad Hussain Wazir et al. / New Carbon Materials, 2009, 24(1): 83–88 Fig.1 Schematic diagrams of the reactor and the melt-spinning apparatus calculated by applying the equation (1). Yield (%) = Mass of the precursor/ Mass of the petroleum pitch ×100 . (1) The schematic diagrams of the reactor and the melt-spinning apparatus are shown in Fig.1. 2.3 Preparation of carbon fibers A laboratory scale apparatus was used to melt-spin the precursor pitch into carbon fibers under pressurized nitrogen of 2 kg/cm2 through a mono-hole spinneret (D = 0.4 mm) at a spinning temperature of 335 o C. The as-spun fibers were stabilized at 320 o C for 2 h in air with a heating rate of 2 oC /min. The stabilized fibers were further carbonized at 1000 o C for 1 h under nitrogen flow in a tube furnace at a heating rate of 5 o C /min. The carbon yield was calculated by applying the equation (2). Carbon yield (%)=Mass of the carbonized fibers/ Mass of the stabilized fibers×100. (2) 2.4 Characterization Metler FP 90 apparatus (Metler Toledo AG, Switzerland, ASTMD3140) was used to determine softening point of samples. Benzene soluble (BS), benzene insoluble (BI), benzene insoluble-quinoline soluble (BI-QS), and quinoline insoluble (QI) fractions of the pitches were measured by the soxlet extraction. The contents of C, H, and N in samples were determined by an elemental analyzer (EA 1110, CE Instruments, Italia), and the O content was calculated by subtracting the sum of C, H, and N (%) from 100. Thermogravimetric analysis (TGA 1640, Stanton Redcroft, Canada) of samples was performed under air and nitrogen atmosphere to find an optimum stabilization temperature or to measure the thermal stability of the samples. The polished section on glass slide of the precursor pitch and the longitudinal sections of the melt-spun fibers were observed under a polarized-light microscope (Olympus Model-CX21FS1 Philippine, Japan). The melt-spun fibers were also examined by Scanning Electron Microscope (FE-SEM S-4700, Hitachi, Japan). Infra Red Spectroscopy (FT-IR Spectrometer, model Perkin Elmer 16pc) was used to characterize the functional groups of both the petroleum pitch and the precursor pitch and extracted mesophase pitch. The precursor pitch and melt spun fiber samples in powder form were used in the X-ray diffraction (XRD) analysis. The XRD patterns of the samples were obtained by a diffractometer (JEOL X-ray diffractometer, model JDX-73) using Mn-filtered Cu-KD as radiation. For tensile strength measurements, 2.5 cm sample was loaded and measured by a tensile tester with a 150 g load and at a cross head speed of 2.5 mm/min. An average was taken from the five tests on the bases of JIS R 7601 method. 3 Results and discussion 3.1 Preparation of carbon fibers 3.1.1 Preparation of precursor pitch Properties of the precursor pitch are summarized in Table 1. The soluble parts are considered to be isotropic in nature, whereas the insoluble parts are anisotropic. During heat treatment of pitch at 400-450 o C, anisotropic spheres called mesophase are developed in the isotropic pitch matrix like a liquid droplet inside a liquid, as described by Brooks and Taylor[13]. Their optical anisotropy and micrometer scale structure can be well observed under a polarized light microscope on the polished sections. These spheres coalesce and form a mosaic-like nematic liquid-crystal structure, which is still plastic and called bulk mesophase[14] with a prolonged heat treatment time. With furthermore heat treatment, the mesophase develops into highly graphitizable carbon, and the mobility of the individual molecule is confined because of the rigidity of the highly ordered solid phase[15]. Table 1 Properties of precursor pitch Solubility w/% Softeningpoint t/ oC BS BI-QS QI 295 5.4 20.3 75.2 *BS: benzene soluble, BI-QS: benzene insoluble-quinoline soluble,QI: quinoline insoluble
Irshad Hussain Wazir et al. /New Carbon Materials, 2009, 24(1): 83-88 b 1 Fig 2 Polarized light microphotographs of(a) precursor pitch showing the mesophase sphere formation, (b) the longitudinal surface of spun fiber, and(c)the cross section of spun fiber Fig 3 SEM microphotographs of (a) stabilized fiber, (b) carbonized fiber at 1000C and(c)cross sectional area of carbonized fiber with high magnification The isotropic pitch is composed mainly of polyaromatic and the H/C ratio decrease abruptly and C content increase by hydrocarbons along with many aliphatic side-chains. The dis- carbonization. The existence of relatively high concentration ordered phase of the isotropic pitch become more and more of low molecular weight components of alkyl groups can be ordered because of the removal of low weight volatile com- derived from the fact that a high uptake of oxygen(16.5 %) onents during heat treatment. The texture of the graphitizable was found during stabilization tion into liquid crystalline state. The nucleation, growth, and 3.1.2 Melt spinning texturing of the mesophase pitch are strongly dependent upon High performance pitch fibers are preparation method, rheological properties of the precursors, mesophase pitch having liquid-crystal characteristics. The and heat treatment temperaturell6l liquid crystalline in the pitch can be readily oriented to pro- It is considered that mesophase pitch having high mo- duce highly oriented texture of fibers during melt spinning lecular weight components without any side groups or small The resulting fibers in their as-spun and stabilized state show molecular components is difficult to be melt-spun. Therefore, highly oriented X-ray reflections, which are similar to the a mesophase pitch containing a small amount of low molecu-(002)reflection of graphite crystalls). Fig. 2(b)and(c)shows lar weight side groups that cause disordering texture is easier respectively, the as-spun fiber and its cross section under the to be melt-spun to form fibers!7. polarized light microscope. Fig 3(a)and(b) show, respectively, The polished section on glass slide of precursor pitch the cross sections of the stabilized fiber and carbon fiber. The shows the mesophase sphere formation as shown by the carbon fiber showed a typical radial core structure-12, 19). The larized light microscope in the Fig. 2 (a). The precursor pitch transverse texture of the cross-sectional area of the carbon was found to be composed of 75% mass fraction mesophase, fiber under a high magnification is also shown in Fig 3(c), which was successfully melt-spun into fibers. The elemental indicating a typical radial core structure with linear and bent analysis results of samples in the process of carbon fiber for- type anisotropic texture. This structure is also considered to be mation are listed in Table 2. It can be found that C, H, and the dependent upon the spinning conditions and the properties of H/C ratio decreases, whereas N and O increase gradually with the precursor pitch processing before carbonization. The contents of H, N, and O
Arshad Hussain Wazir et al. / New Carbon Materials, 2009, 24(1): 83–88 Fig.2 Polarized light microphotographs of (a) precursor pitch showing the mesophase sphere formation, (b) the longitudinal surface of spun fiber, and (c) the cross section of spun fiber Fig.3 SEM microphotographs of (a) stabilized fiber, (b) carbonized fiber at 1000 o C and (c) cross sectional area of carbonized fiber with high magnification The isotropic pitch is composed mainly of polyaromatic hydrocarbons along with many aliphatic side-chains. The disordered phase of the isotropic pitch become more and more ordered because of the removal of low weight volatile components during heat treatment. The texture of the graphitizable carbon depends upon the material structure during transformation into liquid crystalline state. The nucleation, growth, and texturing of the mesophase pitch are strongly dependent upon preparation method, rheological properties of the precursors, and heat treatment temperature[16]. It is considered that mesophase pitch having high molecular weight components without any side groups or small molecular components is difficult to be melt-spun. Therefore, a mesophase pitch containing a small amount of low molecular weight side groups that cause disordering texture is easier to be melt-spun to form fibers[17]. The polished section on glass slide of precursor pitch shows the mesophase sphere formation as shown by the polarized light microscope in the Fig.2(a). The precursor pitch was found to be composed of 75% mass fraction mesophase, which was successfully melt-spun into fibers. The elemental analysis results of samples in the process of carbon fiber formation are listed in Table 2. It can be found that C, H, and the H/C ratio decreases, whereas N and O increase gradually with processing before carbonization. The contents of H, N, and O, and the H/C ratio decrease abruptly and C content increase by carbonization. The existence of relatively high concentration of low molecular weight components of alkyl groups can be derived from the fact that a high uptake of oxygen (16.5 %) was found during stabilization. 3.1.2 Melt spinning High performance pitch fibers are prepared from mesophase pitch having liquid-crystal characteristics. The liquid crystalline in the pitch can be readily oriented to produce highly oriented texture of fibers during melt spinning. The resulting fibers in their as-spun and stabilized state show highly oriented X-ray reflections, which are similar to the (002) reflection of graphite crystal[18]. Fig.2(b) and (c) shows, respectively, the as-spun fiber and its cross section under the polarized light microscope. Fig.3(a) and (b) show, respectively, the cross sections of the stabilized fiber and carbon fiber. The carbon fiber showed a typical radial core structure[11-12, 19]. The transverse texture of the cross-sectional area of the carbon fiber under a high magnification is also shown in Fig.3(c), indicating a typical radial core structure with linear and bent type anisotropic texture. This structure is also considered to be dependent upon the spinning conditions and the properties of the precursor pitch[20]
Irshad Hussain Wazir et al. /New Carbon Materials, 2009, 24(1): 83-88 and 1370 cm 121-23 The numerous bands in the wave numbers regions 3031 and 1680-1462 cm"can be assigned to stretch 80000 ng of aromatic C=C bonds. The bands that car wave numbers 2900-2700 cm"and 1370 cm"are assigned to the stretching and bending modes of saturated aliphatic hy drocarbons the band can be seen at wave number 2348 cm"which corresponds to CO2. The bands at wave numbers 930, 855, 810, and 730 cm, can be ascribed to the 8001000 out-of-plane bending of aromatic C band at wave numbers 1088 and 1012 cm can be observed which can be attributable to the aryl group Fig 4 TGA curve of pitch fibers The FT-IR spectrum of the extracted mesophase pitch is given in the Fig. 5(b). The spectrum contains similar peaks Table2 Elemental analyses of the precursor pitch and pitch fibers relative to the precursor pitch. Numerous bands that can be various conditions seen at wave numbers 3042. 1600. 930. 875.815. and 750 Elemental clare assigned to the presence of aromatic C-H stretching Sample (Atom ratio) C and out of plane deformation of aromatic ring. Bands can be Precursor Pitch 0.5492034.360.353.26 seen in wave numbers 2921, 2832, 2720, 1445, and 1370 cm 0.53 90404.250.40495 which can be ascribed to the presence of aliphatic C-H stretching and methylene C-H(probably naphthenic)bend 80.1329104516.51 modes[21-251. The more intense band at wave number Carbonized fiber 1445 cm"indicates that the material has methylene or naphthene rich structure. Comparatively, on the basis of sepa- 3.2 Thermogravimetric analysIs rating soluble contents from the As it is well known that during the oxidation process, of the bands at wave numbers 750-875 cm"are slightly in- oxygen tends to react first with aliphatic side groups. There- creased compared with the precursor pitch, owing to a sig fore, the stabilization behaviors are dependent on the pitch nificant increase in aromatic contents. This qualitative evi- reactivity, and the higher the oxygen uptake, the more the dence of the low molecular weight aliphatics with high con- aliphatic side-groups and the lower the aromaticity of pitch. tents of aromatics is in accordance with the good spinnablity As shown in Fig 4, the oxygen uptake started at 200C until of the mesophase pitch 450C, at which evident combustion occurs. The carbon yield of 70. 5% can be obtained by residue mass above 600 C under 3.4 X-ray diffractometry The XRD patterns of precursor pitch, the as-spun fiber the stabilized fiber, and carbon fiber are shown in Fig. 6, which 3.3 FTIR analysls show a distinct reflection band at 20 of 25.65. 25.75. 25.55 The profile of the FT-iR spectrum of unextracted precur- and 24.6, respectively. This can be accounted sor pitch is provided in Fig. 5(a). The characteristic bands can presence of graphitic structure in these samples. The interlayer be seen in the wave number region corresponding to the aro- spacings(dooz)of precursor pitch, the as-spun fiber, the stabi matic structures at3031,1680,1600,838,855,810,and730 lized fiber and carbon fiber are shown in the Fig. 7. It can be cm and aliphatic structures at 2915, 2840, 2718, 1595, 1462, found that the dooz-spacings is decreased by orienting the (b)Mesophase pitch 45004000350030002500200015001000500 45004000350030002500200015001000500 Fig5 FT-IR profiles of (a) precursor pitch and(b) extracted mesophase pitch
Arshad Hussain Wazir et al. / New Carbon Materials, 2009, 24(1): 83–88 Fig.4 TGA curve of pitch fibers Table 2 Elemental analyses of the precursor pitch and pitch fibers at various conditions Elemental w/% Sample H/C (Atom ratio ) C HNO Precursor Pitch 0.54 92.03 4.36 0.35 3.26 As-spun fiber 0.53 90.40 4.25 0.40 4.95 Stabilized fiber 0.41 80.13 2.91 0.45 16.51 Carbonized fiber 0.02 95.90 0.16 00 3.92 3.2 Thermogravimetric analysis As it is well known that during the oxidation process, oxygen tends to react first with aliphatic side groups. Therefore, the stabilization behaviors are dependent on the pitch reactivity, and the higher the oxygen uptake, the more the aliphatic side-groups and the lower the aromaticity of pitch. As shown in Fig.4, the oxygen uptake started at 200 o C until 450 o C, at which evident combustion occurs. The carbon yield of 70.5% can be obtained by residue mass above 600 o C under nitrogen. 3.3 FT-IR analysis The profile of the FT-IR spectrum of unextracted precursor pitch is provided in Fig. 5(a). The characteristic bands can be seen in the wave number region corresponding to the aromatic structures at 3031, 1680, 1600, 838, 855, 810, and 730 cm-1 and aliphatic structures at 2915, 2840, 2718, 1595, 1462, and 1370 cm-1[21-23]. The numerous bands in the wave numbers regions 3031 and 1680-1462 cm-1 can be assigned to stretching of aromatic C=C bonds. The bands that can be seen at wave numbers 2900-2700 cm-1 and 1370 cm-1 are assigned to the stretching and bending modes of saturated aliphatic hydrocarbons. The band can be seen at wave number 2348 cm-1, which corresponds to CO2. The bands at wave numbers 930, 855, 810, and 730 cm-1, can be ascribed to the out-of-plane bending of aromatic C–H groups[24-25]. A weak band at wave numbers 1088 and 1012 cm-1 can be observed, which can be attributable to the aryl group. The FT-IR spectrum of the extracted mesophase pitch is given in the Fig.5(b). The spectrum contains similar peaks relative to the precursor pitch. Numerous bands that can be seen at wave numbers 3042, 1600, 930, 875, 815, and 750 cm-1 are assigned to the presence of aromatic C–H stretching and out of plane deformation of aromatic ring. Bands can be seen in wave numbers 2921, 2832, 2720, 1445, and 1370 cm-1, which can be ascribed to the presence of aliphatic C–H stretching and methylene C–H (probably naphthenic) bending modes[21-25]. The more intense band at wave number 1445 cm-1 indicates that the material has methylene or naphthene rich structure. Comparatively, on the basis of separating soluble contents from the precursor pitch, the intensity of the bands at wave numbers 750-875 cm-1 are slightly increased compared with the precursor pitch, owing to a significant increase in aromatic contents. This qualitative evidence of the low molecular weight aliphatics with high contents of aromatics is in accordance with the good spinnablity of the mesophase pitch. 3.4 X-ray diffractometry The XRD patterns of precursor pitch, the as-spun fiber, the stabilized fiber, and carbon fiber are shown in Fig.6, which show a distinct reflection band at 2ș of 25.65o , 25.75o , 25.55o, and 24.6o , respectively. This can be accounted for by the presence of graphitic structure in these samples. The interlayer spacings (d002) of precursor pitch, the as-spun fiber, the stabilized fiber and carbon fiber are shown in the Fig.7. It can be found that the d002-spacings is decreased by orienting the Fig.5 FT-IR profiles of (a) precursor pitch and (b) extracted mesophase pitch
Irshad Hussain Wazir et al. /New Carbon Materials, 2009, 24(1): 83-88 fibers shows the highest tensile strength of approximately 650 among all kinds of fibers teste 4 Concluslons Pitch fiber by condensation at 420C for 7 h, which was composed of Precursor pitch 75% mass fraction mesophase and had a carbon yield of ap- proximately 70.5% with a softening point of 295 C. The pre- 102030405060 250 m/min. The precursor pitch contains mesophase spheres 2e/(°) A typical radial core structure was formed in carbon fibers by carbonization at 1000C, which had a tensile strength of 650 Fig 6 XRD profiles of precursor pitch containing mesophase pitch, MPa. The petroleum-based precursor pitch is suitable for the as-spun carbon fiber, stabilized carbon fiber and carbonized carbon The present work is supported by Higher Education 0360 Commission of Pakistan for the promotion of Science [The Grant-in-Aid for Scientific Research Project No. 20-377/R 0355 D/05/1057 0.350 References 0.345 [1] Rebouillate S, Peng J C, Donnet J B, et al. Carbon fibers appli cations[c] Donne J B, Wang T K, Rebouillat S, et al. eds Precursor pitch As-spun Stab. Carb. at 1000'C Carbon Fibers. New York: Marcel Dekker. 1998: 463-540 Temperature frc [2]Deborah D L C Carbon Fiber Composites[M]. Boston: Butter worth-Heinemann. 1994:116 3 Peebles L H. Carbon Fibers Formation, Structure and Proper Fig 7 dooz values of precursor pitch, as-spun, stabilized and carbon- ties[M]. New York: CRC Press, 1998: 3-42 Ized fibers [4] Dyer J, Daul G C Rayon Fibers[Cy/Lewin M, Pearce E M, eds Handbook of Fiber Chemistry. New York: Marcel Dekker 1998:725-801 [5] Oberlin A, Bonnamy S, Lafdi K Structure and textu bers(C)/Bonnet J B, Wang T K, Rebouillat S, et al, eds Carbon Fibers. New York: Marcel Dekker. 1998: 85-159 [6]Otani S, Okuda K, Matsuda H S. Carbon Fiber[M]. Tokyo Kindai Henshu. 1983: 231 [7 Maeda T, Zeng S M, Tokumitsue K, et al. Preparation of iso- tropic pitch precursors for general purpose carbon fibers(GPCF by air blowing- l. Preparation of spinnable isotropic pitch pre- carb.at1000°c cursor from coal tar by air blowing [J]. Carbon, 1993, 31(3) Temperature t/C 407-412 18 Mdada T, Zeng S M, Tokumitsue K. Preparation of isotropic Fig 8 Tensile strength of as-spun stabilized and carbonized carbon pitch precursors for general purpose carbon fibers(GPCF) by air fibers as a function of temperature blowing-lL. Air blowing of coal tar, hydrogenated coal tar, and petroleum pitches). Carbon, 1993, 31(3): 413-419 esophase spheres in spinning, which increased sharply by [9] Mdada T, Zeng S M, Tokumitsue K. Preparation of isotropic the involvement of oxygen during stabilization and increased pitch precursors for general purpose carbon fibers( GPCF) by sharply by carbonization, agreeing well with the previous air blowing-IlI. Air blowing of isotropic naphthalene and hy publications[1-12,261 drogenated coal tar pitches with addition of 3.5 Tensile strength 1, &-dinitronaphthalene[J). Carbon, 1993, 31(3): 421-426 10 WangCY, Li M W, Wu Y L, et al. Preparation and microstruc- The tensile strengths of the as-spun fibers, stabilized fi- ure of hollow mesophase pitch-based carbon fibers J]. Carbon bers. and the carbon fibers are in Fig 8. The carbon 1998,36(12):1749-175
Arshad Hussain Wazir et al. / New Carbon Materials, 2009, 24(1): 83–88 Fig.6 XRD profiles of precursor pitch containing mesophase pitch, as-spun carbon fiber, stabilized carbon fiber and carbonized carbon fiber at 1000 o C Fig.7 d002 values of precursor pitch, as-spun, stabilized and carbonized fibers. Fig.8 Tensile strength of as-spun stabilized and carbonized carbon fibers as a function of temperature. mesophase spheres in spinning, which increased sharply by the involvement of oxygen during stabilization and increased sharply by carbonization, agreeing well with the previous publications[11-12, 26]. 3.5 Tensile strength The tensile strengths of the as-spun fibers, stabilized fibers, and the carbon fibers are shown in Fig.8. The carbon fibers shows the highest tensile strength of approximately 650 MPa among all kinds of fibers tested. 4 Conclusions The precursor pitch was prepared from petroleum pitch by condensation at 420 o C for 7 h, which was composed of 75% mass fraction mesophase and had a carbon yield of approximately 70.5% with a softening point of 295 o C. The precursor pitch showed good spinnability with a wind up speed of 250 m/min. The precursor pitch contains mesophase spheres. A typical radial core structure was formed in carbon fibers by carbonization at 1000 oC, which had a tensile strength of 650 MPa. The petroleum-based precursor pitch is suitable for the preparation of carbon fibers. Acknowledgment The present work is supported by Higher Education Commission of Pakistan for the promotion of Science [The Grant-in-Aid for Scientific Research Project No. 20-377/R & D/05/1057]. References [1] Rebouillate S, Peng J C, Donnet J B, et al. Carbon fibers applications[C]// Donnet J B, Wang T K, Rebouillat S, et al. eds. Carbon Fibers. New York: Marcel Dekker, 1998: 463-540. [2] Deborah D L C. Carbon Fiber Composites[M]. Boston: Butterworth-Heinemann, 1994: 116. [3] Peebles L H. Carbon Fibers Formation, Structure and Properties[M]. New York: CRC Press, 1998: 3-42. [4] Dyer J, Daul G C. Rayon Fibers[C]//Lewin M, Pearce E M, eds. Handbook of Fiber Chemistry. New York: Marcel Dekker, 1998: 725-801. [5] Oberlin A, Bonnamy S, Lafdi K. Structure and texture of carbon fibers[C]//Donnet J B, Wang T K, Rebouillat S, et al, eds. Carbon Fibers. New York: Marcel Dekker, 1998: 85-159. [6] Otani S, Okuda K, Matsuda H S. Carbon Fiber[M]. Tokyo: Kindai Henshu, 1983: 231. [7] Maeda T, Zeng S M, Tokumitsue K, et al. Preparation of isotropic pitch precursors for general purpose carbon fibers (GPCF) by air blowing-I. Preparation of spinnable isotropic pitch precursor from coal tar by air blowing [J]. Carbon, 1993, 31(3): 407-412. [8] Mdada T, Zeng S M, Tokumitsue K. Preparation of isotropic pitch precursors for general purpose carbon fibers (GPCF) by air blowing-II. Air blowing of coal tar, hydrogenated coal tar, and petroleum pitches[J]. Carbon, 1993, 31(3): 413-419. [9] Mdada T, Zeng S M, Tokumitsue K. Preparation of isotropic pitch precursors for general purpose carbon fibers (GPCF) by air blowing-III. Air blowing of isotropic naphthalene and hydrogenated coal tar pitches with addition of 1,8-dinitronaphthalene[J]. Carbon, 1993, 31(3): 421-426. [10] Wang C Y, Li M W, Wu Y L, et al. Preparation and microstructure of hollow mesophase pitch-based carbon fibers[J]. Carbon, 1998, 36(12): 1749-1754
Arshad Hussain Wazir et al. /Ne Carbon Materials, 2009, 24(1): 83-88 [1 Park S H, Yang K S, Soon Y S, et al. Preparation of partial fibers from precursor pitches synthesized with coal tar or petro- mesophase pitch-based carbon fiber from FCC-DO[J). Carbon leum residue oil[J]. Fibers and Polymers, 2000, 1(2): 97-102 20) Mochida I, Yoon S H. Tak [12 Fumitaka W, Sumihito L, Korai Y, et al. Pitch-based carbon fiber mesophase pitch-based carbon fiber and its control[J]. Carbon, of high compressive strength prepared from synthetic isotropic 1996,34(8):941-956 pitch containing mesophase spheres[J]. Carbon, 1999, 37(6): [21 Guillen M D, Iglesias M J, Domingues A, et al. Fourier trans- 961-967 form infrared study of coal tar pitches[J]. Fuel, 1995, 74(11) [13] Brooks J D, Taylor G H. The formation of some graphitizing carbons[C]/ Walker P L eds Chemistry and Physics of Carbon, 22 Liedtke V, Huttinger K. Mesophase pitches as matrix precursor London Edward Arnold LTD. 1968. 4: 243-286 of carbon fiber reinforced carbon: I. Mesophase pitch prepara- [14] Nazem F F. Flow of molten mesophase pitch[]. Carbon, 1982 on and characterization]. Carbon, 1996, 34(9): 1057-1066 0(4):345-354 [23 Akrami H A, Yardim M F, Akar A, et al. FT-IR characterization [15 Pasuk 1, Banciu C, Bondar A M. Influence of some carbo of pitches derived from Avgamasya asphaltite and Ra- nanostructures on the mesophase pitch development-a structural man-Dincer heavy crude[]. Fuel, 1997, 76(14/15): 1389-1394. study). Romanian Reports in Physics, 2004, 56(3): 320-323 24] Apak A, Yardim M F, Ekinci E. Preparation of carbon fiber [16] Edie DD, Dunham M G Melt spinning pitch-based carbon fi- precursors from the pyrolysis and copyrolysis of Avgamasya bers. Carbon198927(5):647-655 asphaltite and Goynuk oil shale: vacuum distillation and hexane [7 Edie DD, Diefendorf R J. Carbon fiber manufactur- extraction[J]. Carbon, 2002, 40(8): 1331-1337 ing[C)/Buckley J D, Edie DD. eds. Carbon-Carbon Materials [25 Arshad H W, Lutfullah K, Imtiaz A, et al. Preparation of and Composites. New Jersey: Noyes Publications Park Rid mesophase from coal tar pitch[J]. New Carbon Materials, 2003, USA,1993:19 18(4):281-285 [18] Matsumoto T. Mesophase pitch and its carbon fibers[J]. Pure [26 Takaku A, Shioya M. X-ray measurements and the structure of Appl Chem,1975,57(1):1553-1557 polyacrylonitrile- and pitch-based carbon fibers[J]. J Mater Sci, [19 Yang K S, Young O C, Kim Y M, et al. Preparations of carbon 1990,25(l1):4873-4879
Arshad Hussain Wazir et al. / New Carbon Materials, 2009, 24(1): 83–88 [11] Park S H, Yang K S, Soon Y S, et al. Preparation of partial mesophase pitch-based carbon fiber from FCC-DO[J]. Carbon Science, 2001, 2(2): 99-104. [12] Fumitaka W, Sumihito I, Korai Y, et al. Pitch-based carbon fiber of high compressive strength prepared from synthetic isotropic pitch containing mesophase spheres[J]. Carbon, 1999, 37(6): 961-967. [13] Brooks J D, Taylor G H. The formation of some graphitizing carbons[C]// Walker P L. eds. Chemistry and Physics of Carbon, London: Edward Arnold LTD, 1968, 4: 243-286. [14] Nazem F F. Flow of molten mesophase pitch[J]. Carbon, 1982, 20(4): 345-354. [15] Pasuk I, Banciu C, Bondar A M. Influence of some carbon nanostructures on the mesophase pitch development-a structural study[J]. Romanian Reports in Physics, 2004, 56(3): 320-323. [16] Edie D D, Dunham M G. Melt spinning pitch-based carbon fibers[J]. Carbon, 1989, 27(5): 647-655. [17] Edie D D, Diefendorf R J. Carbon fiber manufacturing[C]//Buckley J D, Edie D D. eds. Carbon-Carbon Materials and Composites. New Jersey: Noyes Publications Park Ridge, USA, 1993: 19. [18] Matsumoto T. Mesophase pitch and its carbon fibers[J]. Pure Appl Chem, 1975, 57(11): 1553-1557. [19] Yang K S, Young O C, Kim Y M, et al. Preparations of carbon fibers from precursor pitches synthesized with coal tar or petroleum residue oil[J]. Fibers and Polymers, 2000, 1(2): 97-102. [20] Mochida I, Yoon S H. Takano N, et al. Microstructure of mesophase pitch-based carbon fiber and its control[J]. Carbon, 1996, 34(8): 941-956. [21] Guillen M D, Iglesias M J, Domingues A, et al. Fourier transform infrared study of coal tar pitches[J]. Fuel, 1995, 74 (11): 1595-1598. [22] Liedtke V, Huttinger K J. Mesophase pitches as matrix precursor of carbon fiber reinforced carbon: I. Mesophase pitch preparation and characterization[J]. Carbon, 1996, 34(9): 1057-1066. [23] Akrami H A, Yardim M F, Akar A, et al. FT-IR characterization of pitches derived from Avgamasya asphaltite and Raman-Dinçer heavy crude[J]. Fuel, 1997, 76(14/15): 1389-1394. [24] Apak A, Yardim M F, Ekinci E. Preparation of carbon fiber precursors from the pyrolysis and copyrolysis of Avgamasya asphaltite and Göynük oil shale: vacuum distillation and hexane extraction[J]. Carbon, 2002, 40(8): 1331-1337. [25] Arshad H W, Lutfullah K, Imtiaz A, et al. Preparation of mesophase from coal tar pitch[J]. New Carbon Materials, 2003, 18(4): 281-285. [26] Takaku A, Shioya M. X-ray measurements and the structure of polyacrylonitrile- and pitch-based carbon fibers[J]. J Mater Sci, 1990, 25(11): 4873-4879
