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Volume 1992 (1992)
- Issue 155 Pages 282-
- Issue 154 Pages 213-
- Issue 153 Pages 149-
- Issue 152 Pages 67-
- Issue 151 Pages 2-
Volume 1992, Issue 153
Displaying 1-11 of 11 articles from this issue
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Chifei Wu, Kenichi Suzuki, Shigeo Asai, Masao Sumita, Keizo Miyasaka1992 Volume 1992 Issue 153 Pages 149-154
Published: July 31, 1992
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThe purpose of the present study is to shed light on the electrical conduction mechanism and temperaturedependence of conductivity in polymer filled with conductive particles.
The electrical resistivity of crystalline polymer composite shows a large positive temperature coefficient (PTC) below the melting temperature (Tm) and a rapid decrease above it. This property is due to the thermalexpansion of polymers accompanied with melting of crystalline phase and forming of conductive path in themolten state, and depends on the crystallinity of the matrix polymer and filler content. A lattice model composedof aggregated carbon particles and thermal-fluctuation-induced-tunneling mechanism can successfully explain themagnitude of electrical conductivity of these composite systems and their temperature dependence. The electricalconductivity of these materials is found to be determined by about (12-17Å) inter grain gaps based on tunnelingmechanism. The change of electrical conductivity with temperature below Tm was reasonably explained by thechange of inter grain gaps accompanied with thermal expansion of polymers.View full abstractDownload PDF (748K) -
Shintarou Ishiyama, Motokuni Eto, Tatuo Oku1992 Volume 1992 Issue 153 Pages 155-162
Published: July 31, 1992
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSSince graphite components in the HTGR (=High Temperature Gas-cooled Reactor) are subjected to cyclic stress under the condition of the reactor start-up, operation or shut-down, data on the fracture toughness and resistance against crack extension of graphites under the cyclic stress will be utilized for the design and safety analysis of the reactor. However, graphite materials behave as brittle material during its fracture process, so that, it is very difficult to detect crack on-set point and crack extension during fracture toughness test. Therefore, it is necessary to develop the detecting methods of crack on-set point and crack extension in graphite.
In this paper, six techniques including electrical potential, ultrasonic, unloading compliance, optical observation, dye and crack gage methods were applied to fracture toughness test and discussed to determine the best methods for crack on-set point and crack extension among those techniques, comparing with the accuracy of detecting crack on-set point and crack extension in graphite. It was concluded that electrical potential method is the most sensitive one.View full abstractDownload PDF (1075K) -
Akira Kojima, Shinsuke Hoshii, Tetsuaki Akaishi, Sugio Otani, Tasuku S ...1992 Volume 1992 Issue 153 Pages 163-170
Published: July 31, 1992
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSDiphenylborosiloxane (PBS), a kind of organometallic compound, was compounded with carbon fiber (CF) to form CF/ceramics composites. These composites have excellent mechanical properties with a possibility of their use at high temperatures. So the CF/ ceramics composites were heat-treated at high temperatures, and the change of their structure and the behavior of interface were investigated.
The CF/ceramics composites were prepared by impregnating pitch-type or PAN-basedCF strand with acetone solution of PBS containing SiC powder (as a filler), and by heattreatingthem at 1000°C. Then they were heat-treated at high temperatures of 1250°, 1500°, 1750° and 2000°C. The weight decreasing rates of the composite at 1250°Cwere 4% for that prepared from pitch-type CF, and 8% for that from PAN-based CF.
In the X-ray diffraction patterns of the composites prepared from pitch-type CF and from PAN-based CF, when heat-treated at high temperatures up to 2000°C, only the diffraction peaks by carbon and β-SiC were observed. The higher the treating temperature was, the greater the intensity of diffraction peak by carbon (002) was. The graphitization was more noticeable with pitch-type CF than with PAN-based CF. For any treating temperature, no diffraction peaks by boron or its compounds, such as B4C, were noticed.
Moreover, the diffusion profile of silicon into CF in the composites heat-treated at high temperatures, was inspected by X-ray microanalyzer. The results showed that the existence of silicon was slightly observed only in the vicinity of CF surface, which indicated no diffusion of silicon into CF regardless of its kind and the treating temperature.View full abstractDownload PDF (3565K) -
Hiroshi Iwanaga, Takeshi Iwasaki1992 Volume 1992 Issue 153 Pages 171-175
Published: July 31, 1992
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSA method of measuring tensile strength of a filament with a diameter of μ m order has been devised. The method allows us to measure the tensile load in the range of 20 to 1500mg with an accuracy of about 1 mg under optical-microscope observation. In oder to measure the tensile strength, the cross sectional area of the specimen is estimated from a SEM micrograph of the fractured surface taken parallel to the specimen axis. Srtain is calculated by comparing the distance of markers, i.e. tiny whiskers distriduted on a specimen, on micrographs taken at each stage of loading. The Young's modulus and the tensils strength of a pitch-based isotropic carbon filament thus obtained were about 60GPa and 850MPa, respectively.View full abstractDownload PDF (3527K) -
Masaki Okada, Shin Fukuda, Toshiro Yamashina1992 Volume 1992 Issue 153 Pages 176-183
Published: July 31, 1992
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSCorbon materials have been widely used for the first wall components of fusion devices, jigs and components in semiconductor element-manufacturing furnaces, because of their good resistancefor chemical erosion and high heat flux. Since carbon materials adsorb gases existing in the atmosphere and desorb them at elevated temperatures, it is one of the prime importance to study outgassing behavior and to reduce outgassing rate of carbon materials from the view points of vacuum technology and of producing materials without impurities.
We have developed a compact and complex apparatus (1) with main chamder for measuring thermal desorption spectra (TDS) up to 1500°C and (2) with subchamber capable of measuring outgassing rate below 10-8Pa·m3·s-1·m-2 at room temperature and prebaking up to 400°C. The obtained data can be computerized by using a personal computer.
TDS spectra from isotropic graphites IG-11, IG-110 and IG-110U are shown. It was found that the less the desorption gas from graphite, the less the impurity content in it. The outgassing rate of IG-430U, which is now used for the first wall in the Tokamak fusion device, JT-60U, in JAERI, was foundto be 5.8×10-9 Pa·m3·s-1·m-2 (9.8×10-10 Pa·m3·S-1·kg-1) after baking at 400°C for 26 hours and cooled down for 8 hours.View full abstractDownload PDF (1059K) -
Michio Inagaki, Zheng-De Wang1992 Volume 1992 Issue 153 Pages 184-196
Published: July 31, 1992
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThe intercalation process of metal chlorides into graphite and the formation of stage structures of intercalation compounds in the molten salts of various metal chlorides, and also the state of intercalated metal chlorides in the compounds were summarized on the basis of experimental results. Advantages and disadvantages of the synthesis of metal chloride-graphite intercalation compounds in their molten salt systems were discussed.
1. Introduction
2. Synthesis procedure and controlling factors
3. Formation process of graphite intercalation compounds
4. Control of stage structure in moten salts
5. State analysis of intercalates
6. Exfoliation of graphite films and electrical conductivity
7. Advantages and disadvantages of molten salt methodView full abstractDownload PDF (1650K) -
Hiroshi Shioyama, Masaki Narisawa, Kenji Adachi, Kuniaki Tatsumi, Isao ...1992 Volume 1992 Issue 153 Pages 197-200
Published: July 31, 1992
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSCarbon fiber/carbon composites were prepared from carbon fibers intercalated with AlCl3 as reinforcements, and coal tar pitch or phenol resin as matrix precursor. A1C13, which is known to have a catalytic effect on the carbonization process, was de-intercalated from carbon fibers during the preparation of composites, i.e. impregnation of matrix precursor and carbonization. Hence carbonization of the matrix was affected by AlCl 3, and the bending strength of the composites increased compared with that of composites with pristine carbon fibers.View full abstractDownload PDF (1879K) -
[in Japanese]1992 Volume 1992 Issue 153 Pages 201
Published: July 31, 1992
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSDownload PDF (95K) -
[in Japanese]1992 Volume 1992 Issue 153 Pages 202-207
Published: July 31, 1992
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSDownload PDF (780K) -
1992 Volume 1992 Issue 153 Pages 212a
Published: 1992
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSDownload PDF (81K) -
1992 Volume 1992 Issue 153 Pages 212b
Published: 1992
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSDownload PDF (81K)
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