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Volume 2008 (2008)
- Issue 235 Pages 263-
- Issue 234 Pages 215-
- Issue 233 Pages 115-
- Issue 232 Pages 61-
- Issue 231 Pages 2-
Volume 2008, Issue 233
Displaying 1-15 of 15 articles from this issue
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Yoshiaki Matsuo, Yumiko Matsumoto, Tomokazu Fukutsuka, Yosohiro Sugie2008 Volume 2008 Issue 233 Pages 115-118
Published: June 16, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSGraphite oxide was silylated by dimethyloctylchlorosilane under various conditions. Silylated graphite oxide was successfully obtained and the maximum silicon content reached 0.17 mol/graphite oxide unit when the butylamine/dimethy-loctylchlorosilane/ graphite oxide unit ratio was about 19/16/1. The above maximum silicon content was much smaller than that obtained for graphite oxide silylated by octyltrichlorosilane, probably because of the steric hindrance of methyl groups against oxygen containing groups on the surface of graphite oxide. At the same time, the smaller amount of butylamine was needed to scavenge the HC1 molecules formed as a byproduct, reflecting the smaller number of chlorine atom in the dimethy-loctylchlorosilane molecule.View full abstractDownload PDF (729K) -
Noboru Akuzawa, Hayato Nambu, Manabu Hagiwara, Mono Chiwata, Tatsuya O ...2008 Volume 2008 Issue 233 Pages 119-123
Published: June 16, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThe resistivity of graphite cathode in alumina molten salt was determined along with electrolysis at 945°C. The resistivity decreased monotonically with the progress of the electrolysis and finally reached to a steady value. For HTT-2000 cathode graphite, the steady value was about 70% of that of the original one before electrolysis. The resistivity turned to increase from the steady value just after interruption of the electrolysis current. A characteristic 2-step curve was observed in the resistivity vs. time plot. It increased fairly steeply at first and then became almost constant at a value corresponding to 87-88 % of that of the original value. The resistivity again increased after the plateau and finally returned to the original value. Several experiments including SEM and X-ray diffraction measurements showed that the resistivity change is closely related to the intercalation and de-intercalation of sodium. For HTT-2400 and -2800 cathode graphite, sodium concentration fixed in the matrix after electrolysis was less than that of HTT-2000.View full abstractDownload PDF (1329K) -
Masato Oshima, Kaoru Takeda, Yusuke Okabe, Rika Matsumoto2008 Volume 2008 Issue 233 Pages 124-130
Published: June 16, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSTo analyze the electronic state of alkaline metal-graphite intercalation compounds (AM-GIC), model complexes where two aromatic molecules coordinate to an alkaline metal center (Li, K, Rb, and Cs) were employed, and their geometry optimization, population analysis, and donor-accepter interaction analysis were performed using the density functional theory (DFT) with B3LYP level and Natural Bond Orbital (NBO). The distance of two aromatic ligands of each model complexes showed good agreement with the corresponding identity period of stage 1 AM-GIC. The electronic charges on alkali metal of model complexes and stabilization energies by electron donation from aromatic ligand to alkali metal were calculated by the population analysis.
The theoretical study of the mechanism of ethylene origomerization that proceeds inside the graphite layers was also carried out at DFT with B3LYP level. The Cs-C bond formation through the combination of two cationic Cs+ (η2-H2C=CH2) while accepting electrons from graphite layers is proposed as the initiation reaction of the origomerization. Additionally, we found that the carbon chain elongation reaction holds promise to proceed smoothly with a free energy of activation (ΔG‡) 16.29 [kcal/mol] under the presence of the chemical species having Cs-C bond.View full abstractDownload PDF (1619K) -
Asami Takenaka, Tomoki Tsumura, Masahiro Toyoda2008 Volume 2008 Issue 233 Pages 131-135
Published: June 16, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSTernary graphite intercalation compounds from pitch-based carbon fibers (ICCF) were synthesized. Alkali metal (Li, Na or K) and organic solvent [Tetrahydrofuran (THF) or 1, 2-dimethoxyethane (DME)] were used as intercalates. In the case of alkali metal-DME-ICCF, stage-1 and random stage were synthesized with all of carbon fibers used. In the case of using THF solvent, K-THF-ICCF showing stage-1 and random stage structure was also similarly synthesized. However, Li-and Na-THF-ICCF showing random stage structure were synthesized by using carbon fibers with small Lc size and wide d-spacing. From these results, it was shown that synthesis of the ternary graphite intercalation compounds using CF was sensitive in the steric hindrance of intercalated complexes and crystallinity of carbon fibers, because the texture of carbon fibers prevent the expansion of interlayer spacing. Significant exfoliation could not be recognized, when their ICCFs were rapidly heat-treated at 1000°C. However, miniaturized carbon fibers were obtained by stirring it in HCl.View full abstractDownload PDF (1769K) -
Wataru Ishida, Hiroki Miyaoka, Takayuki Ichikawa, Yoshitsugu Kojima2008 Volume 2008 Issue 233 Pages 136-139
Published: June 16, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSTwo kinds of nano-structural graphite were prepared from graphite powder by ball-milling under hydrogen or argon atmosphere, where each product is denoted as HG or AG, respectively. And then, non-treated graphite powder (G), HG or AG was milled with Li to synthesize lithium-graphite intercalation compounds, which are denoted as Li-G, Li-HG and Li-AG, respectively. In XRD profiles of Li-G and Li-HG, it was revealed that the peaks correspond to LiC6 and LiCl2, while no peaks were observed in the case of Li-AG. However, similar thermal decomposition reactions were observed for all compounds at about 450°C under an inert gas, indicating that Li-AG includes the lithium-carbon (Li-C) compound. After heat treatment under hydrogen pressure, the formation of LiH was confirmed by XRD measurements for all compounds, indicating that the intercalated lithium reacted with hydrogen. Furthermore, all hydrogenated compounds desorbed hydrogen with heating up to 500°C. In addition, the hydrogenated Li-HG and Li-AG formed lithium carbide (LiC) after hydrogen desorption. On the other hand, in the case of the hydrogenated Li-G, it is confirmed that not only LiC but also LiC12 were formed after dehydrogenation.View full abstractDownload PDF (955K) -
Yoshimi Ohzawa, Rieko Minamikawa, Takumi Okabe, Tsuyoshi Nakajima2008 Volume 2008 Issue 233 Pages 140-144
Published: June 16, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSUsing pressure-pulsed chemical vapor infiltration (PCVI) technique, pyrolytic carbon (pyrocarbon) was infiltrated at 950°C from C3H8 (30%)-H2 gas system into the carbonized paper substrate. Carbon fibers in the carbonized paper were coated with dense pyrocarbon films having a laminar texture oriented parallel to the surface of carbonized fibers. It was revealed from XRD and Raman spectroscopy that the crystallinity of pyrocarbon was higher than that of carbonized fiber. BET surface area was decreased from 210 m2g-1 of the original substrate to 1.9 m2 g-1 of the pyrocarbon-coated sample.Reversible capacity of the sample coated with 8 mass % pyrocarbon was 500 mA h g-1, which were nearly close to that of the original carbonized paper. High irreversible capacity of 180 mA h g-1 was observed in the original carbonized paper, reflecting the disordered structure and high surface area. Irreversible capacity was reduced to 100 mA h g-1 by coating with 8 mass % pyrocarbon, which would be attributed to high crystallinity, laminar structure and low surface area of pyrocar-bon. Irreversible capacity was further decreased with increasing the mass fraction of pyrocarbon, however, reversible capacity was also decreased.View full abstractDownload PDF (1656K) -
Masayuki Kawaguchi, Katsuya Ohnishi, Hiroyuki Yagi2008 Volume 2008 Issue 233 Pages 145-147
Published: June 16, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSGraphite like layered material of composition BC2N was prepared by CVD reaction of acetonitrile with boron trichloride at a temperature between 1470 K and 2070 K. Potassium (K) could be intercalated by vapor phase reaction with BC2N and the obtained material was compared with graphite intercalation compound (GIC). The 1st stage K-GIC was brown in color, while almost no change in color for the 1st stage K intercalated BC2N was observed after the K intercalation. Lithium (Li) was also intercalated into BC2N and graphite by electrochemical method. Both 1 st stage Li intercalated BC2N (Li-BC2N) and Li-GIC were brown in color. They showed similar X-ray diffraction patterns except a stronger relative intensity of (100) diffraction for Li-BC2N than that of Li-GIC, probably because of a stronger interaction between the host BC2N and the intercalated Li.View full abstractDownload PDF (654K) -
Masahiro Toyoda, Asami Takenaka, Yoshihiko Takano, Noboru Akuzawa, Aki ...2008 Volume 2008 Issue 233 Pages 148-150
Published: June 16, 2008
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSBinary intercalation compound CaC6 was synthesized by soaking the platelet of HOPG into the molten Li-Ca alloy (Li/Ca=4.0) at 350°C for a long soaking (more than 10 days). The C ompound CaC6 thus synthesized was confirmed to be superconductive with the critical temperature of about 10 K. For the synthesis of the superconductive intercalation compound CaC6, the crystallinity of the host graphite has to be selected and long soaking in molten Li-Ca alloy is also required. Superconductivity of CaC6 was supposed to belong in second type.View full abstractDownload PDF (797K) -
Hiroshi Shioyama2008 Volume 2008 Issue 233 Pages 151-156
Published: June 16, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSGraphite intercalation compounds (GICs) are of interest to chemists and physicists because of their unusual properties. In recent years, much attention has been focused on the preparation and the properties of GICs and on their utilization. The present paper attempts to summarize recent experimental results relating to the novel methods to control precisely the stage structure of metal chloride-GICs. For vapor phase intercalation of AlCl3, the activity of halogens or CrO3 as additives was found to control the stage structure of obtained GICs. The extent of EuCl3 and TbCl3 intercalation could be controlled through adjustment of the pressure of chlorine: increasing pressure tends to increase the extent of intercalation. On the other hand the stage structure of CuCl2-GIC could be controlled by adjusting the pressure of argon gas in the reaction tube: argon gas tend to inhibit the extent of CuCl2 intercalation.View full abstractDownload PDF (1391K) -
Masahiro Toyoda2008 Volume 2008 Issue 233 Pages 157-165
Published: June 16, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSExfoliated graphite (EG) has been manufactured as a pristine material for flexible graphite sheets (FGS) in huge amount in the world. It is produced through rapid heat-treatment of residue compounds of natural graphite flakes with sulfuric acid up to a high temperature around 1000°C. After its heat-treatment, it consists of fragile worm-like particles, which are formed by exfoliating perpendicularly to the basal plane of graphite. FGS have been manufactured through compression without any binder of the EG. This FGS is widely used as electronic components heat radiation material, gasket and packing materials of all fields from the high temperature to low temperature. Recently, FGS is also used for the gasket and packing material as a replacement of the asbestos. One of another applications in the EG, it shows a large amount of sorption capacity of heavy oils very quickly, 1 g of lump of the EG sorbed more than 80 g heavy oil. It is much larger than the package of adsorbents ever used. Estimation of pore structure for EG was carried out through mercury porosimetry. Its large sorption capacity relates to the pore structure of EG. Inside pores in the worm like particles were determined from the analysis of fractured surface of the EG particles which are prepared by cleaving, with the aid of image processing by assuming ellipsoidal form. As a consequence, the large sorption capacity strongly relates to large space in the worm like particles. It is considered that a demand of graphite particles to prepare the EG will be increased in future because of replacement of asbestos and increasing in demand for electronic components.View full abstractDownload PDF (4921K) -
Claire Hérold, Nicolas Emery, Jean-Francois Marêché ...2008 Volume 2008 Issue 233 Pages 166-173
Published: June 16, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSAmong graphite intercalation compounds, the CaC6 binary phase exhibits superconducting properties with the highest critical temperature of 11.5 K. The samples are synthesised using a liquid-solid method allowing the preparation of pure bulk samples, auspicious for crystallographic and magnetic measurements. Thecrystal structure of CaC6 was entirely specified, this compound crystallises in the Om space group.The magnetic properties of this phase were studied with a magnetic field successively applied parallel and perpendicular to the graphene sheets. The magnetic phase diagram indicates that the CaC6 binary compound is a type II superconducting material slightly anisotropic in spite of its lamellar structure. The in-plane magnetic penetration depth measurements show a clear exponential behaviour at low temperature, consistent with an s-wave symmetry of the gap function, well fitted by the standard BCS theory in the dirty limit.View full abstractDownload PDF (1807K) -
Naoto Ohta, Yoko Nishi, Takahiro Morishita, Tetsuro Tojo, Michio Inaga ...2008 Volume 2008 Issue 233 Pages 174-180
Published: June 16, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSImidization and carbonization behaviors of various aromatic polyimide films synthesized from an anhydride with different diamines were investigated by FTIR and TG/DTG methods. Imidization of poly (amic acid) s with pendant -CH3 and-CF3 groups directly bonded to phenyl ring required long times for curing at 300°C. Pyrolysis and carbonization of polyimides having pendant groups occurred over a little wider temperature range than those having no pendant groups. The carbonize films were of ultramicroporous character with pore width of ca. 0.5 nm. Pore development in carbon films was found to depend strongly on whether the precursor polyimide contains fluorine or not ; fluorine containing polyimide gave a high microporous surface area of 1400 m2/g and micropore volume of 0.39 mL/g.View full abstractDownload PDF (1455K) -
Tetsuro Hirasaki, Takeshi Meguro, Toru Wakihara, Toru Wakihara, Junich ...2008 Volume 2008 Issue 233 Pages 181-186
Published: June 16, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThe effect of ultrasonic irradiation for the polymerization of furfuryl alcohol (FA) with a pore-forming agent on the microstructure of the carbons derived from the furan resin was investigated. Tetra ethylene glycol (TEG) and ethylene glycol (EG) were examined as the pore-forming agents. In the system of FA-TEG, atendency for the surface area to increase with increasing power of ultrasonic wave was recognized. The irradiation under 400 W and 500 W gave the surface areas larger than 900 m2/g. The micropore volume and the surface area were the larges in the carbon derived from the furan resin made from the mixture with equivalent amounts of FA and TEG.
A comparison of the numbers of ethyl group between TEG and EG showed that the morphology and the microstructure were significantly different. The effect of TEG in terms of pore development was confirmed to bemore effective than EG.View full abstractDownload PDF (1852K) -
Masaru Kimura2008 Volume 2008 Issue 233 Pages 187-196
Published: June 16, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSDownload PDF (4917K) -
[in Japanese]2008 Volume 2008 Issue 233 Pages 205
Published: June 16, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSDownload PDF (248K)
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