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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 151
Displaying 1-8 of 8 articles from this issue
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Toshihiko Matsuda, Yoshio Suzuki, Naoki Sasanami1992 Volume 1992 Issue 151 Pages 2-7
Published: February 20, 1992
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThe dual-grade split brush is composed of a low-resistivity leading component and a high-resistivity trailing one. The commutating capability has been studied through the numerical analysis of sparkless zone and the running tests with a 3kW DC machine.
To do the numerical analysis, eight suppositive sample brushes which have the same contact resistance and the different ratio of Rb1 /Rb2 are used. Where Rbl is the contact resistance of the leading component and Rb2 the one of the trailing component. For the running tests, ten sample brushes are used. These brushes are made up from the various combination of four kinds of electrographite grades and one copper-graphite grade. And the sparkless zone of these brushes have been measured.
The results are the following. The commutating capability of the dual-grade split brush, like the monoblock one, becomes better as the contact resistance grows higher. With almost the same contact resistance, the dual-grade split brush shows better capability than the monoblock one. And under the same conditions, the abrasion of the former brush is about 1/2 of the latter one.View full abstractDownload PDF (763K) -
Minehiro Kamiyama, Toshiaki Sogabe1992 Volume 1992 Issue 151 Pages 8-12
Published: February 20, 1992
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSStudying gas permeability of carbon materials is very important to use the materials for some applications such as chemical reaction chambers, high vacuum vanes, seal rings, fuel cells and nuclear fusion devices. Although, the relationship between gas permeability and open pore is not fully understood.
Gas permeabilities were measured for various carbon materials with different mean pore radius and porosity. The materials include both self-sintering (meso-carbon based) and binder-sintering (binder and coke based) carbons. Empirical equations in which viscous flow permeability constant (Bo) and Knudsen flow permeability constant (Ko) are related to mean pore radius (a) and open porosity (V) are obtained: Bo=0.74a2.06 V2.51, Ko=6.18a0.96 V2.16. We have estimated the effectiv length of pores in unit volume. The lengths of pores contributed for viscous flow (lBo) and Knudsen flow (lKo) were calculated separately. It is considered that the ratio (lBo/lko) indicates a tortuosity of open pores.View full abstractDownload PDF (530K) -
Yoshio Suzuki, Naoki Sasanami, Toshihiko Matsuda, Mitsuhiko Yamaguchi1992 Volume 1992 Issue 151 Pages 13-19
Published: February 20, 1992
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSCommutating ability of two-grade double-layer brush, which is composed of the leading layer of low resistivity grade and the trailing layer of high resistivitygrade, is investigated by numerical analysis of commutation and by experiments using a testing apparatus of commutating ability of brushes and a 560w universal motor. The following results are obtained.
In case of the two-grade double-layer brush as well as monoblock brush, the higher the sliding contact resistance, the better the commutating ability has. If the contact resistance of both two-grade double-layer brush and monoblock brush with same size are nearly equal, the former has the better commutating ability than the latter.
And in case of both brushes having low contact resistance, this superiority of the twograde double-layer brush is conspicuous.
On the subject of the relation of commutation characteristics and the ratio of contactresistance of trailing layer to leading layer, the value of ratio of about 5 gives the best commutation quality.
And in case of both brushes having low contact resistance, this superiority of the two-of monoblock brush, if the sliding contact resistance as well as metal content ofboth brushes are almost same.View full abstractDownload PDF (833K) -
Kazuo Kobayashi, Kazutoshi Maeda, Hideaki Sano, Yasuo Uchiyama1992 Volume 1992 Issue 151 Pages 20-26
Published: February 20, 1992
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSHigh temperature oxidation tests of carbon/SiC/B4C composite made from mixed powders of coke (51.2 wt%), SiC (38.8 wt%) and B4C (10 wt%) were carried out in different atmospheres of dry air, dry oxygen and wet air at temperature range from 600 to 1400°C. The oxidation had three different behaviours depending on the oxidation temperature ranges of below 700°C, 800-1000°C and above about 1100°C. Below about 700°C oxidation was relatively suppressed due to probably B2O3 liquid phaseformed from B4C. At about 800-1000°C protective B2O3 layer vaporized easily, and dense and homogeneous protective oxide layer was difficult to form on the surface, and then active oxidation proceeded in dry oxygen atmosphere. Particularly in wet air condition oxidation became much more active at this temperature range and oxidation proceeded deeply into inner part of the sample, because denseprotective layer could not be formed. While above about 1100°C dense and uniform protective layer formed o thesurface and protected further oxidation. The protective oxide layer formed at about 1200°C was suggested to be SiO2 rich phase and was known remarkably stable for oxidation even in wet air at about 900°C.View full abstractDownload PDF (1344K) -
Kazuo Kobayashi, Hiroyuki Funabashi, Yasuo Uchiyama1992 Volume 1992 Issue 151 Pages 27-34
Published: February 20, 1992
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSMorphological change by air oxidation at high temperature was investigated for some kinds of mesophase pitch-based carbon fibers with different microstructures and different graphitization degrees and was compared with that of PAN-based carbon fiber. By oxidation striations and pits appeared on the fiber surface and the surface appearance of the oxidized fibers suggested that oxidation behaviour was affected strongly by microstructure of the fiber. That is, the region where edges of carbon basal planes concentrated on the surface was preferentially oxidized. Pits generally formed in array along striation parallel to the fiber axis. Morphology of the pit was a little different between the fiber with radial structure and the one with onion structure. V shape crack observed for some of the fiber with radial structure changed to larger U shape crevasse by oxidation. The oxidation temperature at which morphological change appeared shifted to higher temperature for the fiber with higher graphitization degree. While, pits formed irregularly and diameter of the fiber decreased gradually by oxidation in the case of PAN-based carbon fiber.View full abstractDownload PDF (1845K) -
6th Subcommittee (Evaluation Technology), New Carb, Yuji Yamamoto, Ke ...1992 Volume 1992 Issue 151 Pages 35-40
Published: February 20, 1992
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThe procedure for the measurement of lattice constants and crystallite sizes of artificial graphite materials was proposed by the 117th Committee (Carbon Materials) in Japan Society for the Promotion of Science and called “Gakushin method”. It has been used in many companies in Japan since 1963.
As a part of activity of New Carbon Forum, its usage in companies was explored by sending questionnaires. The several factors affecting on X-ray diffraction profiles, selection of slit system, mixing ratio of inner standard silicon, compaction of sample powder, etc., were studied.View full abstractDownload PDF (758K) -
Seiji Motojima, Masayuki Kawaguchi, Hiroshi Iwanaga1992 Volume 1992 Issue 151 Pages 41-50
Published: February 20, 1992
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSCoiled carbon fibers were prepared by catalytic pyrolysis of acetylene at 500-800°C using Ni powder as a catalyst. It was found that the presence of small amounts of impurity gas, such as H2S, PCl3, was indispensable for the growth of coiled carbon fibers with good yield and reproducibility. Maximum yield (about 80%) of the coiled carbon fibers were obtained using PCl3 as an impurity. Optimum flow rate of PCl3 was 0.05-0.1 ml/min, and coiled carbon fibers were not obtained at a flow rate of zero or above 0.15 ml/min. Morphology and growth mechanism of the coiled carbon fibers were discussed. The mechanical property of the coiled carbon fibers were examined.View full abstractDownload PDF (2229K) -
Susumu Yoshimura1992 Volume 1992 Issue 151 Pages 51-58
Published: February 20, 1992
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSSince delocalized π electrons can move about throughout a crystal or molecule without distorting it, π-electron materials have many peculiar characteristics such as extremely high electron mobility and superpolarization. The π-electron cloud is also a fundamental reaction field for organic and biological materials.
The Yoshimura π-Electron Materials Project will view the large space occupied by the freely-moving π electrons as domains of electron motion and materials transformation. The project will exploit and elucidate unique physical, chemical and biochemical phenomena which result from these domains. For this, the project will develop synthetic methods and processes for new organic and inorganic materials with extended π-electron systems and with high crystallinity. It will elucidate the mechanisms of superpolarization, high electron mobility and nonlinear phenomena. The project may propose new electronic devices based on unique features of π electrons. Other work will focus on selective and/or anomalous reactions in which the π-electron domains participate. This work may shed light on mechanisms of biocompatibility and proliferation on carbonacious materials in relation to electronic structures of the π-electron systems.View full abstractDownload PDF (1147K)
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