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Volume 1976 (1976)
- Issue 87 Pages 123-
- Issue 86 Pages 93-
- Issue 85 Pages 47-
- Issue 84 Pages 2-
Volume 1976, Issue 84
Displaying 1-6 of 6 articles from this issue
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Nobuatsu WATANABE, Yasushi KITA1976 Volume 1976 Issue 84 Pages 2-6
Published: February 10, 1976
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThe effect has been studied of reaction conditions such as temperature, fluorine pressure and time on the crystal structure of graphite fluoride by differential thermal analysis (DTA) method and X-ray diffractmetry. The natural graphite from Madagascar ores ground to 200-250 mesh was used for the substrate of fluorination. The experiments have been carried out under fluorine pressure 100 to 400 mmHg at temperatures in the range 500-600°C. Since there was found a close correlation among β001, d100 and d001, the crystallinity of graphite fluoride was evaluated by d001 values.
Since the result of DTA agreed well with that of X-ray diffractmetry, the thermal property of graphite fluoride could be correlated to its crystal structure. Until the sample was completely fluorinated, the crystallinity of graphite fluoride increased with increasing temperature and decreasing fluorine pressure. After the complete fluorination (C: F=1: 1), the crystallinity of graphite fluoride increased linearly with the logarithm of time, the slope of which was dependent on the temperature but not on fluorine pressure. The lattice strain of carbon layer accelerated the crystallization, which took longer time than that required for the formation of graphite fluoride.View full abstractDownload PDF (783K) -
S. Marinkovic, P.W. Whang, A. Navarrete, P.L. Walker1976 Volume 1976 Issue 84 Pages 7-13
Published: February 10, 1976
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSCarbon-carbon composites have been fabricated using a cellulose powder which is molded at low pressures, carbonized at 800°C and infiltrated by a CVD technique at 700°C using propylene as a source of carbon. Infiltration rate at time t is governed by the amount of open porosity existing in the sample at this time. These composites are then treated at temperatures ranging from 1000°C to 2400°C. Flexural strength, elastic modulus, Knoop hardness and electrical conductivity of the composites are progressively changed with increasing apparent density (d), following expressions of the type Y=adb. Coefficient of thermal expansion, wear resistance and oxidation resistance increase with infiltration time, while surface area sharply drops to a low value after initial infiltration. Heat treatment (HT) of the composites considerably changes their properties, but not monotonically with increasing HTT. Rather they show maxima or minima at 1500-2000°C HTT. However, propertydensity relationships of the same type (but with different constants a and b) as for non-heat-treated samples are generally preserved after HT. Comparison of the densest composites with corresponding commercial glassy carbons heat treated to similar temperatures shows that oxidation rate and coefficient of thermal expansion of the composites are lower, flexural strength and electrical conductivity are similar, while Young's modulus, wear resistance and hardness are greater for the glassy carbons.View full abstractDownload PDF (1209K) -
Hiroshi TSUTSUI, Yasuhiro YAMADA, Hidemasa HONDA1976 Volume 1976 Issue 84 Pages 14-19
Published: February 10, 1976
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSBinder pitch for the production of carbon materials was prepared by adding meso-carbon microbeads (Type-M) to straight coal-tar pitch.
The straight coal-tar pitch containing 0-20 wt% Type-M microbeads was heat-treated at temperatures between 300 and 400°C. The amounts of fixed carbon (FC), benzene insolubles (BI) and quinoline insolubles (QI), and softening Point (SP) of the pitch were measured. Then, the capability in using the pitch as bmder for carbon materials was examined by measuring compressive strength of the carbon blocks prepared by using the pitch.
Values of FC, BI, QI and SP of the pitch increased linearly with increasing of additional amounts of Type-M microbeads and could be estimated from its additional amounts. The compressive strength of carbon blocks prepared from the mixture of the 35 wt% pitch with 65 wt% coke powder was measured. The compressive strength of carbon blocks had high values when the pitch containing 3-10 wt% Type-M microbeads were used, and these values were higher than those of the carbon blocks produced by using commercial binder pitch.
These results show that the characteristics of pitches can be controlled easily by additional amounts of meso-carbon microbeads and that the carbon blocks in which these pitches are used as a binder have high compressive strength.View full abstractDownload PDF (1202K) -
Kiyoshi NOTO, Takuro TSUZUKU1976 Volume 1976 Issue 84 Pages 20-25
Published: February 10, 1976
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThe magnetoresistance (Δρ/ρ0) of graphite is discussed into details with an emphasis on the magnetic field dependence systematically deviating from the so-called quadratic law. A two-band theory developed on the basis of the ellipsoidal approximation for the Fermi surfaces has yielded a success in the formulation ofΔρ/ρ0 as a function not only of the field intensity (H) but of its azimuth with respect to the c-axis; which reveals that the deviation is an intrinsic nature of the majority carrier system of graphite, rather than a result of the presence of the low-mobility minority carriers. Therefore, the conduction parameters (carrier density and mobility) have to be consistently determined with such a non-quadratic H-dependence ofΔρ/ρ0; appropriate methods for the evaluation are described in connection with the foregoing two-band theory, McClure's conductivity tensor analysis and modified Kohler's rule respectively.View full abstractDownload PDF (990K) -
Kiyoshi KAWAMURA, Hisashi OHSHIMA, Takuro TSUZUKU1976 Volume 1976 Issue 84 Pages 26-28
Published: February 10, 1976
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESS -
[in Japanese], [in Japanese]1976 Volume 1976 Issue 84 Pages 29-36
Published: February 10, 1976
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSDownload PDF (1407K)
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