MOcHIDA et al Table 1. Some al properties of mesophase and isotropic pitches prepared using H SPa Ac Solubility X-ray properties Code Raw materialC vol% BS Bl-Ps PI(QI) H/C fa d002(A) Lc(002)(nm) mNP Methylnaphthalene20510052193329)0690.863.524 mNP/NPI(7/3)d) mNP( +197100 0690.823.550 NP(30 wt%o NPI 168 0 51 9 40(26) 0.71 0.79 Indistinct Indistinct 237 948(31)0.620.803.574 (a)Softening point. (b) Anisotropic contents. (c) Carbon aromaticity. (d) Pitch thermally blended at 300 C in the nitrogen atmosphere nozzle(Diameter =0.3 mm, Length over Gakushin(JSPS)[15], using an X-ray diffractometer (L/D)=3). Spinning Rigaku Geigerflex: CuKa. 0.15406 nm, 40 k v, 30 Spinning conditions of the present study are A commercial STM Nanoscope II in table 2 cnts Inc )was applied at ambient conditions, The As-spun fibers were oxidatively stabilized in air at scanning areas of 200 x 200 and 2000 x 2000 nm were 270C for 20 minutes at a heating rate of 5C/min used for the observation of the sample surface. The scanning head, tip, and mechanical actuator were Stabilized fibers were carbonized in an argon atmo- mounted on an anti-vibration isolation platform. The sphere at 1000 C for 10 minutes at a heating rate of constant tunnel current mode was employed, and the 20 C/min, and successively graphitized at 2500C for surface relief was expressed by different shades of I minute at a heating rate of 100C/min grey. The parameters applied were current 1.02-1.03 nA; bias voltage 500 m V 2.2 Characterization of graphitized fibers Tensile strength, Youngs modulus The transverse and longitudinal sections of graphi- break were measured at room temperature using ced fibers,(fibers with the typical radial open wedge mono-filaments according to the procedure defined ransverse texture, F-A; fibers with the radial skin in Japanese Industrial Standard(JIS R-7601), using and random core texture, F-B; fibers with the typical an Instron type tensile testing machine (Instron 4200 random texture, F-C; fibers with quasi onion texture, series)at a head speed of 0.5 mm/min a gauge length F-D), were observed by OM, SEM, HR-SEM, and of 25 mm was employed to obtain the tensile proper TEM. STM was also used for observing the longitudi- ties. Tensile strength and Youngs modulus were nal sections of a graphitized fiber the results of 16 tests [161. All fiber samples were observed under a polarized their values distributing within 15%. Compressive light optical microscope(Olympus B061) Fibers were strength was measured according to the composite mounted and polished by conventional procedures. method(Vr(fiber volume)=60%)mono-filament To examine the transverse alignments of graphi- test [17]. The results of 5 tests were averaged tized fibers under sEM (Jeol JSM 5400)and HR- SEM (Jeol JSM 6403F), all fiber samples were cut in liquid nitrogen to approximately 0.5 cm length 3. RESULTS and attached to a copper grid with graphite paste. 3. 1 Transverse alignments of the mesophase The transverse section exposed by the cutting was pitch-based carbon fibe open wedge For the TEM observation, ultra-thin sections, transverse texture Figure 1(a) shows the OM 40-60 nm thickness, perpendicular and parallel to SEM, HR-SEM images of the transverse section thc fibcr axis were prepared by ultramicrotomy (Leica the naphthalene derived mesophase pitch Ultracut S), using a diamond knife, and observed by based graphitized fiber with the typical radial open TEM (Jeol JEM100CX), using bright field(BF), 002 wedge texture(F-A) dark field(DF) and 002 lattice The fibers showed PAC-man cross-sectional shape Lc(002)and La(110)of graphitized fibers were with typical radial open wedge transverse alignment measured according to the method defined by Three isochromatic color regions, blue, red, and Table 2. Conditions of spinning Spinning rate Amounts of extrudate Diameter of pitch Code fibers(m 60⊥10 50+5 mNP/NPI (7/3) 120(±1.0) 123(+0.5942 I. MOCHIDA etal. Table 1. Some analytical properties of mesophase and isotropic pitches prepared using HF/BF, SPa AC? Solubilities(wt%) X-ray properties Code Raw material “C ~01% BS BI-PS PI(QI) H/C fa” d002(A) Lc(OOZ)(nm) mNP Methylnaphthalene 205 100 52 19 33(29) 0.69 0.86 3.524 7.5 mNP/NPI(7/3)d) mNP(70 wt%) + 197 100 0.69 0.82 3.550 5.0 NPI NPM NP(30 wt%) Naphthalene Naphthalene 168 0 51 9 40(2 6) 0.71 0.79 Indistinct Indistinct 237 100 33 19 48(31) 0.62 0.80 3.574 3.2 (a) Softening point. (b) Anisotropic contents. (c) Carbon aromaticity. (d) Pitch thermally blended at 300°C in the nitrogen atmosphere. nozzle (Diameter = 0.3 mm, Length over diameter (L/D) = 3). Spinning was carried out using a labora￾tory scale mono-filament spinning apparatus [ 131. Spinning conditions of the present study are detailed in Table 2. As-spun fibers were oxidatively stabilized in air at 270°C for 20 minutes at a heating rate of S”C/min c141. Stabilized fibers were carbonized in an argon atmo￾sphere at 1000°C for 10 minutes at a heating rate of 20”C/min, and successively graphitized at 2500°C for 1 minute at a heating rate of lOO”C/min. 2.2 Characterization of graphitized$bers The transverse and longitudinal sections of graphi￾tized fibers, (fibers with the typical radial open wedge transverse texture, F-A; fibers with the radial skin and random core texture, F-B; fibers with the typical random texture, F-C; fibers with quasi onion texture, F-D), were observed by OM, SEM, HR-SEM, and TEM. STM was also used for observing the longitudi￾nal sections of a graphitized fiber. All fiber samples were observed under a polarized light optical microscope (Olympus B061). Fibers were mounted and polished by conventional procedures. To examine the transverse alignments of graphi￾tized fibers under SEM (Jeol JSM 5400) and HR-SEM (Jeol JSM 6403F), all fiber samples were cut in liquid nitrogen to approximately 0.5 cm length, and attached to a copper grid with graphite paste. The transverse section exposed by the cutting was observed without any coating. For the TEM observation, ultra-thin sections, 40-60 nm thickness, perpendicular and parallel to the fiber axis were prepared by ultramicrotomy (Leica Ultracut S), using a diamond knife, and observed by TEM (Jeol JEMlOOCX), using bright field (BF), 002 dark field (DF) and 002 lattice fringe mode. Lc (002) and La (110) of graphitized fibers were measured according to the method defined by Gakushin (JSPS) [ 151, using an X-ray diffractometer (Rigaku Geigerflex; CuKa, 0.15406 nm, 40 kV, 30 mA). A commercial STM Nanoscope II (Digital instru￾ments Inc.) was applied at ambient conditions. The scanning areas of 200 x 200 and 2000 x 2000 nm were used for the observation of the sample surface. The scanning head, tip, and mechanical actuator were mounted on an anti-vibration isolation platform. The constant tunnel current mode was employed, and the surface relief was expressed by different shades of grey. The parameters applied were current 1.02-1.03 nA; bias voltage 500 mV. Tensile strength, Young’s modulus and strain-to￾break were measured at room temperature using mono-filaments according to the procedure defined in Japanese Industrial Standard (JIS R-7601), using an Instron type tensile testing machine (Instron 4200 series) at a head speed of 0.5 mm/min. A gauge length of 25 mm was employed to obtain the tensile proper￾ties. Tensile strength and Young’s modulus were evaluated by averaging the results of 16 tests [ 161, their values distributing within 15%. Compressive strength was measured according to the composite method (V, (fiber volume) = 60%) mono-filament test [ 171. The results of 5 tests were averaged. 3. RESULTS 3.1 Transverse alignments of the mesophase pitch-based carbon fiber 3.1.1 Fiber with typical radial open wedge transverse texture Figure l(a) shows the OM, SEM, HR-SEM images of the transverse section in the methylnaphthalene derived mesophase pitch￾based graphitized fiber with the typical radial open wedge texture (F-A). The fibers showed PAC-man cross-sectional shape with typical radial open wedge transverse alignment. Three isochromatic color regions, blue, red, and Table 2. Conditions of spinning Code F-A F-B F-C F-D Material mNP NPM mNP/NPI (7/3) mNP Spinning Spinning rate temperature (“C) (mjmin) 285 400 310 400 280 300 290 400 Amounts of extrudate (mgimin) 60 + 10 50 * 5 55 k 6 60 k 10 Diameter of pitch fibers (mm) 12.5 (& 0.5) 9.0 (k 1.0) 12.0 (+_ 1.0) 12.3 (k 0.5)