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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 149
Displaying 1-12 of 12 articles from this issue
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Isao Mochida, Yozo Korai, Akemi Azuma, Eiji Kitajima1991 Volume 1991 Issue 149 Pages 191-196
Published: September 30, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSA mesophase pitch of low stabilization reactivity because of highly condensed structure was blended to enhance the stabilization reactivity with some mesophase pitches of higher reactivity which carry more amount of naphthenic and methyl groups. The blending of the latter pitches in 30-50% improved the spinning properties and shortened the time required for the stabilization. The rate of oxygen up-take in the stabilization of the blended pitch was same to the average one of two component pitches, however, the amount necessary for the complete stabilization was smaller than the averaged one.
The pitches were dissolved well each other without significant reactions between them to reduce the viscosity of fused pitch. The blended pitches appeared to be oxidized independently to up-take oxygen, however, the sufficient stabilization of the pitch of lower reactivity was achieved when the partner of higher reactivity was enough stabilized. The mesogen molecules in the more reactive mesophase pitch which is stabilized earlier may inhibit softening of the whole blended mesophase pitch including not-sufficient stabilized mesogens in the less reactive mesophase pitch. Significant amount of additives is necessary in such a mechanism of the stabilization enhancement because the mesogens of lower reactivity should be surrounded by those of higher reactivity.View full abstractDownload PDF (628K) -
Shintarou Ishiyama, Motokuni Eto, Tatsuo Oku1991 Volume 1991 Issue 149 Pages 197-203
Published: September 30, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSNuclear graphite materials behave as a brittle material during their fracture, so that, properties of higher fracture toughness and crack extension resistance have been required for graphites. The knowledge of fracture behavior of graphites must be needed for its modification, however, those behavior of graphites has not been examined in detail considering to its mechanical and physical properties.
In this paper, fracture toughness tests were performed for nuclear graphites and properties of fracture toughness and crack extension resistance of graphites were examined as a function of mechanical and physical properties of graphites. From the results, the following conclusions were derived:
(1) 3-point strength of graphites increases as Young's modulus increases.
(2) Relationship between density and Jic was not found.
(3) Jic increases as Young's modulus increases for lower Young's modulus materials, however, for high Young's modulus materials, Jic decreases as Young's modulus increases.
(4) The graphites consisted of larger grain have larger crack extension resistance.
(5) The value of JICE/π σsb2 is related to mean grain size of graphites, where E and σsb were Young's modulus and 3-point bending strength respectively.View full abstractDownload PDF (820K) -
Norio Iwashita, Michio Inagaki1991 Volume 1991 Issue 149 Pages 204-210
Published: September 30, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSFour kinds of “mesophase”-pitch-based carbon fibers with different textures in their cross-sections were used as host materials for graphite intercalation compounds with sulfuric acid. Sulfuric acid could intercalate into only fibers having positive value of magnetoresistance by chemical oxidation with nitric acid. This seemed to be a criterion for the intercalation. The potential change during the intercalation was found to depend on texture of fibers; the ones with radial texture increasing their potentials rapidly, probably due to their large edge surface area of graphite structure, and the ones with concentric texture showing stepwise increase of potential, almost the same as the case of flaky natural graphite powder with a large particle size.View full abstractDownload PDF (740K) -
Yoshio Yamada, Yuichi Sekine, Takeshi Furuta, Minoru Shiraishi, Suehik ...1991 Volume 1991 Issue 149 Pages 211-219
Published: September 30, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSPitch (CTP)-anthraquinone (AQ) and hydrogenated pitch (HCTP)-AQ condensates were prepared by reacting the pitch and AQ in the presence of polyphosphoric acid with various mixing ratios. The reaction mechanism of the pitch and AQ was investigated by use of some model compounds. These condensates obtained were characterized in terms of solubility for solvents, thermogravimetric analysis and observation of optical textures of the heat-treated products. The condensates prepared with a mixing ratio of 7/3-6/4 for CTP to AQ gave a maximum carbonization yield (76%) at 1000°C and the carbonized products showed a mozaic texture. In the case of HCTP-AQ, a comparable high yield and a similar texture were obtained for the condensate prepared with an equal amount of HCTP and AQ. It was found that the hydrogenation of pitch to be condensated with AQ is important to improve the solubilization of the condensates for solvents and also to develop the anisotropic textures. Both condensates with the high carbonization yield gave a large interlayer spacing of about 0.34nm on the heat-treatment up to 2200°C, but the graphitizability was considerably enhanced when they were heat-treated above 2500°C.View full abstractDownload PDF (1562K) -
Takeshi Tanamura, Hiroshi Shioyama, Shigeru Ikeda, Masakazu Adachi, Ro ...1991 Volume 1991 Issue 149 Pages 220-224
Published: September 30, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThe influence of carbon fiber type on the thermal conductivity of carbon-carbon composite (C/C) were measured for Uni-directional C/C (UD-C/C) with three types of carbon fiber as the reinforcement. The relationship between thermal conductivity and fiber orientation were measured for six different fiber content in each direction for three dimensional carbon-carbon composites (3D-C/C).
Thermal conductivity of C/C is dependent on not only matrix structure but also fiber type. The matrix structure has strong effect on carbon fiber type. Thus, the carbon fiber type is one of the important parameter for thermal conductivity.
Moreover, thermal conductivity has strong effect on fiber content in measurement direction. Therefore, 3D-C/C could be tailored to have the requirement property for thermal conductivity.View full abstractDownload PDF (689K) -
in situ ESR StudyTomohiko Kaneko, Tetsuro Yokono, Yuzo Sanada1991 Volume 1991 Issue 149 Pages 225-230
Published: September 30, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThe early stage of carbonization of synthetic pitches derived from aromatic hydrocarbons such as naphthalene, anthracene, phenanthrene and 9, 10-dihydroanthracene, with trifluoromethanesulfonic acid as a catalyst were investigated by means of high temperature ESR.
Temperature dependence of radical concentration of synthetic pitches observed with in situ ESR showed the following three distinct stages in common; 1st stage, from 100°C to 200°C, where radical concentration increases: 2nd stage, from 200°C to 400°C, in which decreases: and 3rd stage, above 400°C, where again increases. Especially, the change in radical concentration in the 2nd stage is closely related to the form of optical anisotropic texture of derived carbon.
The radical concentration of pitches measured at room temperature increased with increasing of average molecular weight, and good correlation was found.View full abstractDownload PDF (1881K) -
Akira Kojima, Shinsuke Hoshii, Tetsuaki Akaishi, Sugio Otani, Tasuku S ...1991 Volume 1991 Issue 149 Pages 231-238
Published: September 30, 1991
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSThe unidirectional carbon fiber/ceramic composites (CFRC) were prepared from high performance carbon fiber (CF) and diphenylborosiloxane.
The CF strand impregnated with diphenylborosiloxane containing SiC micro powder (0.26μm in size) were heated at 500°C in air, and reheated at 1000°C in N2.
The influences of the following factors on the mechanical properties of CFRC wereinvestigated; (1) amounts of SiC powder, (2) CF contents, (3) diphenylborosiloxane concentration of infiltration solution, and (4) numbers of infiltration.
The mechanical properties of CFRC were mainly influenced by the diphenylborosiloxane concentration of infiltration solution.
The prepared CFRC rod (3mm in diameter) showed the bulk density of 1.67g/cm3, the bending strength of 320MPa and the Young's modulus of 130GPa.
The stress-strain curve of this prepared CFRC indicates a high toughness.View full abstractDownload PDF (2774K) -
Kazuro Kawamura, Seiji Yamanaka, Jyoji Koga, Mikiya Ono1991 Volume 1991 Issue 149 Pages 239-243
Published: September 30, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSA slurry was prepared by the mixture of carbosilane polymer, binder and plasticizer. This slurry was formed to a sheet by the doctor blade method, and heated to create a SiC sheet. As the result, SiC sheet of 0.3-0.4mm thickness and 25mm×25mm wide was obtained. The SiC sheet which was obtained by the heat-treatment at the temperature at 1260°C gave the values as follows; specific gravity was 2.03, bending strength 281 MPa and electrical resistivity for the direction of thickness was 1.8×103Ω·cm.View full abstractDownload PDF (4377K) -
Yasuhisa Maeda, Daisuke Sugimori, Michio Inagaki1991 Volume 1991 Issue 149 Pages 244-247
Published: September 30, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThe cyclic voltammograms of the graphite in LiClO4-DMSO, NaClO4-DMSO, KClO4-DMSO and RbClO4-DMSO solutions showed the cathodic current and the anodic current peaks corresponding to the intercalation and deintercalation processes of alkali metal ions, respectively. The x-ray diffraction patterns indicated the formation of the second stage intercalation compounds due to the cathodic reduction (electrode potential: 2.5V vs. SCE, electric quantity: 40 C) of graphite in each solution. The change of the electrode potential with time after cathodic reduction showed less self-discharge of K+-compound than other compounds.View full abstractDownload PDF (382K) -
Masahiro Anzai, Toru Sudo, Takeo Nakagawa1991 Volume 1991 Issue 149 Pages 248-250
Published: September 30, 1991
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSNew magnetic abrasive finishing process for mold surface has been done by authors. In this study, the new type magnetic abrasive was made by mixing with Fe powder and SiC whiskers. This fabrication process is so very easy that Fe powder-SiC whisker abrasive has comfortable grindability in comparison with magnetic abrasives using other fabrication process. This Fe powder-SiC whisker mixing abrasive is fit for the purpose to have a high grindability abrasive in the field of magnetic finishing.View full abstractDownload PDF (3555K) -
Yoichiro Nakanishi, Kanenaga Fujii, Yoshihiro Sawada1991 Volume 1991 Issue 149 Pages 251-255
Published: September 30, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSCharcoal flowers had been used at tea ceremony in Edo era in Japan by the name of “Ohanazumi”, but they remained in the literature only its name without any description on their preparation method. In the present study a preparation of charcoal flowers was tried by the application of pre-oxidation process. Flowers were dried at first and then oxidized in a furnace or in an air oven at temperatures between 200°C and 300°C. The flowers thus oxidized were put into a quartz vessel and carbonized by heating in a crucible furnace from 250°Cd to 600°C in a flow of argon gas with a heating rate of 120°C/hr. The charcoal flowers could easily be prepared by this method in a short time of four hours or so. The charcoal flowers obtained in the present study were those from chrysanthemum, babies-breath, sazanka, fuyou (a kind of rose mallow) and etc. Art charcoals from leaves of Japanese holly and ginkgo, mandarin oranges and dried mushrooms (Shiitake) were also made.View full abstractDownload PDF (1122K) -
Isao Mochida, Yozo Korai, Nobuhiro Akashi, Takatsugu Fujiura, Katsunor ...1991 Volume 1991 Issue 149 Pages 256-259
Published: September 30, 1991
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSMechanical strength of MgO bricks bound with mesophase pitches was studied. Grinding and moulding of MgO-Mesophase powder provided the strength over 80 kg/cm2 by the baking at 600°C when mesophase pitches of moderate softening points was blended by 5 wt%. It should be noted that the calcination above 900°C decreased the strength due to the oxidation of binder by contaminated air during the calcination. High pressure for moulding and more pitch increased the strength significantly.
Impregnation of pitch on to MgO from aromatic solvent was very effective to increase the strength. The fluidity at 300-400°C and high coking value of the mesophase pitch may be origins for the high strength of the brick, allowing the homogeneous dispersion of the binding pitch on MgO surface and thick binding coke among the MgO particles.View full abstractDownload PDF (493K)
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