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Volume 1997 (1997)
- Issue 180 Pages 217-
- Issue 179 Pages 145-
- Issue 178 Pages 101-
- Issue 177 Pages 59-
- Issue 176 Pages 2-
Volume 1997, Issue 179
Displaying 1-10 of 10 articles from this issue
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Electronic PropertiesH. A. Yu, T. Kaneko, S. Otani, Y. Sasaki, S. Yoshimura1997 Volume 1997 Issue 179 Pages 145-152
Published: October 31, 1997
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThe electrical conductivity, Hall coefficient, carrier density, carrier mobility and optical band-gap of carbonaceous films made by chemical vapor deposition (CVD) of 2, 5-dimethyl-p-benzoquinone between 500 and 1000°C were measured. Based on these results, the electronic properties for the carbonaceous films have been studied, and the following conclusions could be reached.(1) The carbonaceous film shows a higher electrical conductivity, 4.5×10-3 S·cm-1 for film made at 500°C and about 1×103 S·cm-1 for that made at 1000°C, than that of other carbon materials heat treated at the corresponding temperatures.(2) The carbonaceous films deposited below 700°C have a positive Hall coefficient characteristic of a p-type semiconductor, and above 700°C have a negative Hall coefficient of an n-type semiconductor.(3) At low temperatures of CVD below 700°C, the Hall-carrier density of the carbonaceous films increases with CVD temperature while the carriermobility decreases, the change of electrical conductivity being mainly caused by the increment of the Hall-carrier density.(4) At high temperatures of CVD above 700°C, the electron-carrier mobility of the carbonaceous films increases with CVD temperature while the carrier density was nearly unchanged, the change of electrical conductivity being mainly caused by increment of the electron-carrier mobility.(5) The carbonaceous film deposited at 500°C shows an optical band-gap of 0.25 eV and a mobility gap of 0.3 eV.View full abstractDownload PDF (1311K) -
Temperature and Pressure as CVI ParametersYoshio Sohda, Russell Judd Diefendorf1997 Volume 1997 Issue 179 Pages 153-158
Published: October 31, 1997
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSChemical Vapor Infiltration of carbon was studied in uniform bore capillary tubes using CH, as deposition gas. The relation between CVI parameters and the resultant deposition profile, rate and microstructure were examined. Higher temperature and pressure produce higher deposition rate and higher degree of prefferred orientation. Lower temperature and pressure yield better deposition uniformity along the capillary. Deposition profile along the furnace axis is determined by temperature profile of the furnace and the amount of deposition species in gas phase. Uniformity of deposition in the capillary depends on location of capillary in the furnace. Longer contact time gives higher rate at mouth of a capillary, and in-pore deposition profile depends on the relative ratioof the rate of diffusion of species and the rate of reaction. On the other hand, shorter residense time shows a better profile, and the profile within the capillary is controlled not only by diffusion/reaction relative ratio but by temperature gradient and by the concentration of deposition species within the capillary. Gas analysis suggests that microstructure along the furnace and within the capillary is affected by the ratio of aromatic species to acetylenic species in the gas phase.View full abstractDownload PDF (4208K) -
Norihiko Setoyama, Takaomi Suzuki, Katsumi Kaneko1997 Volume 1997 Issue 179 Pages 159-166
Published: October 31, 1997
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSA validity of the subtracting pore effect (SPE) method for the specific surface area (SSA) determination of activated carbons was investigated by the grand canonical Monte Carlo (GCMC) simulation of nitrogen adsorption isotherms on a model graphite slit-pore at 77K. The simulated adsorption isotherm changed sensitively with the micropore width. The αs-plot was constructed for the simulated adsorption isotherm and it showed the filling-and cooperative-swings, which were assigned to the enhanced surface-molecule and intermolecular interactions, respectively. The simulated as-plot gave a theoretical basis for the SPE method of the correct SSA determination for activated carbons. Also it was given that the shape analysis of the αs-plot can provide the pore size distribution.View full abstractDownload PDF (1456K) -
Yasuhiro TANABE, Ken-ichi SASAKI, Takashi AKATSU, Eiichi YASUDA1997 Volume 1997 Issue 179 Pages 167-175
Published: October 31, 1997
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSThree types of polycrystalline graphites and two 2D-C/C composites were impacted by a steel projectile of 4-mm diameter with a velocity of 0.7km/s to 1.7km/s. The damage behavior by impact, especially, spallation of the materials were investigated through the measurement of scattered and spalled volumes, formation and propagation of stress wave, shape of scattered fragments (debris), and the observation of debris by a high speed camera. The followings were concluded: (1) Critical velocity of spallation in graphites increased with increasing their static strength and thickness of the specimen, (2) weak-bonded layers in 2D-C/C composite was easily debonded (peel-off) at the interfaces by impact, (3) in C/C composites debonding region near the rear surface was larger in the case a projectile stopped in them than in the case it passed through them, (4) shock waves in graphites could be measured using acoustic emission sensor, (5) the size of the spalled fragments depended on the material properties even among polycrystalline graphites, and (6) a model of spalling process in a polycrystalline graphite was proposed.View full abstractDownload PDF (5791K) -
Hideaki Sano, Kou Nakayama, Yasuo Uchiyama, Kazuo Kobayashi1997 Volume 1997 Issue 179 Pages 176-183
Published: October 31, 1997
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSModifications by boron-treatments were done for a C/C composite and six types of modified C/C composites such as the as-received sample, the heat-treated sample, the sample with B (boron)-coating, the B-doped sample, the heat-treated sample with B-coating and the B-doped sample with B-coating were prepared to investigate the effects of B-coating and B-doping on the air oxidation behaviors. B-coating was carried out by dipping the sample in suspended solution of metallic boron powder with polyethylene glycol. B-doping was done by heat-treatment of the B-coated sample at 2000°C. The B-coating was found to be the most effective to prevent air oxidation of the C/C composites up to 950°C, while at 1000°C, B-doping gave lower oxidation loss. Formation of B2O3 glass film on the surface of the B-coated sample was observed above 600°C and covered the surface, which protect the sample from loss by oxidation, however, B2O3 on the surface began to vaporize above 800°C. Disappearance of boron on the surface became remarkable at 1000°C consequently, Bcoated sample lost its protective property against oxidation. It was found from morphological observation that oxidation of the sample proceeded from the surface to inside for the heat-treated sample. While for the B-coated sample, inside of the sample was firstly oxidized remaining outer region and for the B-doped sample matrix of the sample was firstly and then fiber was oxidized.View full abstractDownload PDF (6809K) -
O. P. Bahl1997 Volume 1997 Issue 179 Pages 184-188
Published: October 31, 1997
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSDownload PDF (873K) -
Eiichi Yasuda1997 Volume 1997 Issue 179 Pages 189-195
Published: October 31, 1997
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSGovernmental project of [Carbon Alloys] is started from April 1997 through three years, which is supported by the Ministry of Education, Science, Sports and Culture as a Grant-in-Aid for Scientific Research on Priority Areas. The details of application was reported in Tanso 1995 [No.170] previously. The project is organized by myself andcomposed of four teams. The title of the first team is “Space control in atomic and crystalline level”, the leader of it is Prof.M.Endo of Shinshu university. The second one is entitled as “Space control in boundary and microstructure level” (leader: myself), and the third one is “Space control in surface and rare surface level” (leader; Prof. K.Kaneko of Chiba University).The forth one is “Development of new functions” (Prof. A.Oya of Gunma university). In every group there are 5 scheduled members and 10 selected candidates in average.To save the research periods the project focused into four materials as graphite intercalation, porous material, C/C composite and new composite system in addition to the four teams.View full abstractDownload PDF (1925K) -
Yoichi Takahashi, Michio Inagaki1997 Volume 1997 Issue 179 Pages 196-199
Published: October 31, 1997
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSDownload PDF (764K) -
[in Japanese]1997 Volume 1997 Issue 179 Pages 206
Published: October 31, 1997
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSDownload PDF (1605K) -
[in Japanese]1997 Volume 1997 Issue 179 Pages 209
Published: October 31, 1997
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSDownload PDF (240K)
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