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Volume 1991 (1991)
- Issue 150 Pages 266-
- Issue 149 Pages 191-
- Issue 148 Pages 134-
- Issue 147 Pages 57-
- Issue 146 Pages 2-
Volume 1991, Issue 150
Displaying 1-11 of 11 articles from this issue
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Tomoaki Hino, Yuji Takasugi, Toshiro Yamasina1991 Volume 1991 Issue 150 Pages 266-270
Published: December 25, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSFor radiation-enhanced sublimation (RES) of graphite, a simple model is proposed. The model shows that the produced interstitials which escape the recombination with vacancies can reach the surface and evaporate. Only a small fraction of interstitials contribute to the RES yield. The dependences on energy, mass and incident angle of ion are explained based on this mode. The changes of surface morphology and structure due to the RES are investigated. It is found that the interstitials and vacancies are completely mixed in the surface and thus the structure change becomes the same for every graphite material. From this result, it is suggested that the RES yield becomes the same even if the graphite texture is different. In order to suppress the RES, thus it is important to reduce the heat flux to the graphite wall in a fusion reactor.View full abstractDownload PDF (938K) -
Hirokazu Ugachi, Shintaro Ishiyama, Motokuni Eto, Masahiro Ishihara1991 Volume 1991 Issue 150 Pages 271-276
Published: December 25, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSTo investigate the effect of strain rate on fracture behavior for coarse grained nuclear graphite, PGX, a hydraulic servo type impact testing machine has been constructed and compressive impact strength test was performed at various strain rates up to more than 100 (1/s). From the results, the following conclusions were derived.
(1) Compressive impact strength of graphite increases with increasing of strain rate in the range of 10-3 to 100 (1/s).
(2) Compressive impact strength decreases drastically for strain rates more than 100 (1/s).
(3) Compressive impact strength dose not depend on specimen volume.View full abstractDownload PDF (727K) -
Toshio Tomikawa, Sugio Otani1991 Volume 1991 Issue 150 Pages 277-284
Published: December 25, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSA new secondary battery has been devised using an activated carbon fiber kni (ACF) as negative electrode material; the cell construction was ACF I KOH aqueous solution I NiOOH I Ni. The maximum discharge capacity as large as 1069C per one gram of ACF, was obtained for ACF electrode heat treated between 1673 and 1873 K. Form the amount of occluded potassium and hydrogen changing with the charge-discharge cycle, the ACF has been concluded to function as a specific hydrogen electrode.View full abstractDownload PDF (882K) -
Harald Bolt, Masato Akiba, Armin Benz, Jochen Linke1991 Volume 1991 Issue 150 Pages 285-289
Published: December 25, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSFor the design of next generation fusion devices, a data base for materials which are considered as prime candidates for plasma facing applications is needed. With regard to the material behaviour under off-normal operation conditions of the plasma, especially data on the performance of these materials under short heat pulses with an energy deposition of several MJ/m2 are required. In an initial test series, both electron beam and laser beam facilities were used to perform disruption simulation tests on graphites, pyrolytic carbon, carbon fiber reinforced carbon (CFCs), and boron doped carbon materials. After theex=periments, morphological changes on the specimens were examined and the thermal erosion loss of the materials under the applied heat loads was measured and compared to numerical predictions.View full abstractDownload PDF (905K) -
Changes in Dimension and Physical Properties Caused by Neutron Irradiation and Heat TreatmentHideto Matsuo1991 Volume 1991 Issue 150 Pages 290-302
Published: December 25, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSNuclear graphite and carbon material were irradiated in the JMTR, JRR-2 and HFR at 550-1335°C up to a maximum neutron fluence 6.8×1025 n/m2 (E>29fJ). Changes in dimension, thermal expansivity, thermal conductivity, electrical resistivity and Young's modulus were measured after the irradiation and the successive thermal annealin at each fixed temperature up to 2300°C.
Macroscopic dimensional shrinkages were observed, and the shrinkage rate were the smallest value at irradiation temperature of around 850°C, and carbon material showed larger shrinkage rate than that of nuclear graphite. Coefficient of thermal expansion increased in the initial small range of neutron fluence, followed by decrease with neutron fluence. After the irradiation thermal conductivity decreased and electrical resistivity and Young's modulus increased.
Heat treatment was done for irradiated nuclear graphite and carbon material, and property changes were measured. Significant difference in dimensional changes was observed for the samples of nuclear graphite and carbon material. Increase of thermal conductivity was observed for irradiated carbon material. A model of irradiation defects is given to explain the effects of irradiation and thermal annealing.View full abstractDownload PDF (1689K) -
Hiroko Kaneko, Takamichi Aoki, Akira Negishi, Ken Nozaki1991 Volume 1991 Issue 150 Pages 303-309
Published: December 25, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSWe propose a method for evaluating carbon clothes as a battery electrode, by using cyclic voltammetry. Carbon clothes and carbon felts are consisted of carbon fibers of micrometer order in diameter. Electrochemical behavior of each carbon fiber from the clothes, controlls electrochemical property of the clothes. We have made a microcylindrical electrode from the clothes and have evaluated carbon fibers as battery electrodes from the results of the following experiments.(1) Observation of carbon fibers by SEM photograph, (2) Blank currents on the fiber electrodes, (3) Hydrogen, Oxygen, chlorine gases evolution potentials, (4) Electrode reactions of ferri/ferrocyanide ions, (5) Electrode reactions of active materials (in this case, vanadium ions).
Electrochemical evaluation of the carbon fibers as flow-type battery electrodes are possible with this methode. This method is also useful for guide-line to make up and to select a new carbon cloth electrode or to improve carbon materials for the batteries.View full abstractDownload PDF (1203K) -
Akira Negishi, Ken Nozaki, Hiroko Kaneko1991 Volume 1991 Issue 150 Pages 310-318
Published: December 25, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSCarbon electrode materials for electrolyte flow type batteries, zinc-chlorine, zincbromine, and iron-chromium redox flow batteries, have been characterized by SEM observation, X-ray diffraction, and micro Raman spectroscopy. Most of the electrode materials characterized are same materials used in the practical batteries which have shown excellent performance. It is found that SEM is favorable to observe textures of the electrode materials. X-ray diffraction is able to imform macroscopic or average crystalline structures, and micro Raman spectroscopy can distinguish the crystalline structure of the surface from that of the bulk of the electrode materials, in order to evaluate the electrode performances.View full abstractDownload PDF (1878K) -
Morinobu Endo, Hidetoshi Nakamura, Akihiko Emori, Satoshi Ishida, Mich ...1991 Volume 1991 Issue 150 Pages 319-327
Published: December 25, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSIn order to develop Li secondary battery with high performances, various kind of graphite fibers were used as a positive electrode of Li secondary battery. The characteristics of Li/LiClO4-PC/graphite fibers battery, charging and discharging properties and discharging capacity were examined, and the battery performances were evaluated as functions of the structure of the fibers.
Highly ordered vapor-grown graphite fibers heat treated at 2700°C showed the cell potential as high as 4.5V (2mA out-put current, vs Li) with high out-put stability. More than 400 times of charge and discharge cycles were possible. The fibers heat-treated at 2740°C showed the 270C/g of capacity (at 5mA out-put current) and the out-put energy density of 310 Wh/kg. Other types of graphite fibers exhibited less performances than those of the well-ordered ones. It is shown that with increasing the crystallite thickness of the fibers, the performance is largely improved.View full abstractDownload PDF (2851K) -
Post-Graphite Fluoride CathodeHidekazu Touhara, Shigeaki Suganuma, Fujio Okino1991 Volume 1991 Issue 150 Pages 328-337
Published: December 25, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSWhen the recent papers on fluoro-graphite intercalation compounds are reviewed, it is noticed that it has become possible to control the crystallinity, physical properties and C-F bond character of the fluorine-graphite intercalation compounds CxF by designing and controlling the intercalation of fluorine in a wide range. The relationships have also become clear between the battery performances, such as open circuit voltage (OCV), discharge potential and stability, utilization of the cathode active mass, energy density, etc. and the crystallinity or the C-F bond character of the cathode materials. Because of the higher OCV and much lower overpotential compared with the conventional graphite fluoride cathodes, the CχF cathode with semi-ionic bonding between carbon and fluorine has high discharge potential and high energy density, and draw much attention as a candidate for the post-graphite fluoride cathode. The time has also come for the fluorinegraphite intercalation compounds CχF to be synthesized by designing the functionalities as cathode active material. The advent of a variety of post-graphite fluoride cathodes is expected.View full abstractDownload PDF (1335K) -
Tatsuo Oku1991 Volume 1991 Issue 150 Pages 338-353
Published: December 25, 1991
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSGraphite materials have been used in the nuclear fission reactors from the beginning of the reactor development for the speed reduction and reflection of neutron. Graphite materials are used both as a moderator and as a reflector in the core of high temperature gas-cooled reactors, and both as a radiation shielding material and as a reflector in the sur-rounding of the core for the fast breeder reactor. On the other hand, graphite materials are being positively used as a first wall of plasma as it is known that low Z materials are useful for holding high temperature plasma in the nuclear fusion devices. In this paper the present status of the application of graphite materials to the nuclear fission reactors and fusion devices (reactors) is presented. In addition, a part of results on the related pro-perties to the structural design and safety evaluation and results examined on the subjects that should be done in the future are also described.View full abstractDownload PDF (2027K) -
Toshiro Yamashina, Tomoaki Hino1991 Volume 1991 Issue 150 Pages 354-364
Published: December 25, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSIn order to systematically evaluate graphites (isotropic graphite, pyrolytic carbon, C/C composite) as fusion first wall material, the Graphite Project Team was organized in 1986 under the support of the Fusion Special Development Program, the Ministry of Education, Science and Culture in Japan. Apporoximately twenty institutions participated in this project and the following issues were investigated until the end of fiscal year of 1989;
(1) vacuum engineering properties (gas desorption, effective surface area, gas permeation),
(2) interactions with hydrogen ions (sputtering, retention, surface damage),
(3) thermal shock resistivity (heat load test, fracture toughness).
From the results of vacuum engineering and the thermal shock properties for isotropic graphites, it was found that the graphite with relatively low density was adequate as the first wall material. The erosion due to hydrogen ions and the retention properties were approximately same for every kinds of isotropic graphites. Gas desorption properties of C/C composites with high thermal shock resistance were very similar to that for the isotropic graphite. The gas desorption of the isotropic graphite was largely suppressed by the coatings of pyrolytic carbon. Based on the present results, the problems associated with the graphite as first wall of fusion reactors were pointed out.View full abstractDownload PDF (1273K)
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