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Volume 29, Issue 7
Displaying 1-6 of 6 articles from this issue
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Kazutaka Makino, Jusuke Hidaka, Haruhiko Maki, Shigeo Miwa, Thomas P. ...1982 Volume 29 Issue 7 Pages 229-235
Published: September 25, 1982
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFormation mechanism of particle existing density distribution in penetration testing of powder bed is fundamentally discussed. The particle existing density distribution change in penetration testing, of which geometrical the structure is simple and the physical meaning is easier to be understood, is observed by static X-ray radiographs. It is clearly shown that the particle existing density distributions around a plunger exhibit periodicity, reflection at wall, diffraction through a slit and interference between two slits. And the spacial distribution of displacement vector is pointed out to be one of the important factors which determine these phenomenon mentioned above.View full abstractDownload PDF (4870K) -
Initial pH and Dissolved Oxygen on Fe3O4 Formation by Aerial Oxidation of Fe(OH)2 suspensionsMasaki Kondo, Nobuaki Nakashima, Terutaka Hirasawa1982 Volume 29 Issue 7 Pages 236-240
Published: September 25, 1982
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe variation of DO (dissolved oxygen), pH and ORP in the course of Fe(OH)2 oxidation, the yields of Fe3O4 determined by measuring the concentrations of Fe(II) and total Fe ions in the suspension and the settling velocity of final oxidation products were studied.
Completion of Fe(II) oxidation was detected by measuring the DO concentration or ORP in alkaline suspensions. During the oxidation, DO value was not detected and the rate of Fe(II) oxidation was shown by the product of KLa (oxygen transfer coefficient) by the saturated concentration of oxygen in the suspension.
The initial pH suitable for Fe3O4 formation was 11.5-12.5 at 40°C or lower and 11.5-13 at 60°C or higher, whereas the settling velocity of the final products became faster as the initial pH was lower.View full abstractDownload PDF (319K) -
Effect of Fe(OH)2 oxidation Rate on Fe3O4 FormationMasaki Kondo, Nobuaki Nakashima, Terutaka Hirasawa1982 Volume 29 Issue 7 Pages 241-245
Published: September 25, 1982
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSThe aqueous suspensions containing 0.05, 0.10 and 0.20 M Fe(II) with pH 12 were subjected to oxidation with air at 20, 40, 60 and 80°C. The time duration, θe, needed for complete oxidation of Fe(II), which had been detected by the presence of dissolved oxygen in the suspension, was limited between 15 and 180 min by varing the oxidation rate.
Relation between the yield of Fe3O, (X) and θe was obtained as follows; dX/dθe =k(1-X )2 or 1/(1-X)=kθe+1, where k is a function of the oxidation temperature.
The Fe3O4 content of the oxidation product was affected by the oxidation rate and temperature. Settling velocity of the product became faster with increasing X for X≥0.6.View full abstractDownload PDF (312K) -
Hiroshi Nagai, Yoshiki Takebayashi, Takeshi Fujikawa, Keiichiro Shoji1982 Volume 29 Issue 7 Pages 246-249
Published: September 25, 1982
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe isothermal oxidation behavior of sintered Fe-20Cr alloys with various amounts of Y2O3 and La2O3 dispersion was investigated in the temperature range from 1273 to 1473 K in air. Dispersion of Y2O3 and La2O3 significantly improved the oxidation resistance. The amounts of Y2O3 and La2O3 dispersion needed to suppress the break-away oxidation increased with increasing oxidation temperature. The improvement effect of La2O3 on the oxidation resistance was stronger than that of Y2O3. The grain size of the alloy decreased with increasing the amounts of Y2O3 and La2O3 dispersion. However, there was no apparent correlation between the oxidation resistance and the grain size of the alloy. The results of IMA analyses showed that the composition of the Cr2O3 scale formed during the early stage of oxidation was strongly dependent on the amounts of Y2O2 and La2O3 in the alloy.View full abstractDownload PDF (2768K) -
Hiroshi Nagai, Yoshiki Takebayashi, Kazuhiro Watanabe, Keiichiro Shoji1982 Volume 29 Issue 7 Pages 250-255
Published: September 25, 1982
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe isothermal oxidation behavior of sintered Fe-20Cr alloys with a simultaneous addition of Y2O3-A1, Y2O3-Si and La2O3-Si was investigated in the temperature range from 1273 to 1523 K.
Simultaneous addition of Al and Si with rare earth oxides significantly reduced the oxidation rate of the alloy and suppressed the break-away oxidation. In the case of the simultaneous addition of rare earth oxides with Si, La2O3 was more effective than Y2O3, especially at higher temperatures. The spalling of the scale was also excellently suppressed by the simultaneous addition of Al and Si with rare earth oxides, although the singular addition of Al and Si accelerated the spalling of the scale.
Dense internal oxide layer of Al2O3 and SiO2 formed beneath the Cr2O3 scale in the alloys containing Al and Si. However, it seemed unlikely that the simultaneous addition of Al and Si with rare earth oxides enhanced the internal oxidation of Al and Si and changed the shape of the internal oxide layer. From the result obtained in this study, it seemed reasonable that the excellent improvement in the scale adhesion induced by the simultaneous addition of Al and Si with rare earth oxides was not explained only by "keying" and "vacancy sink" models.View full abstractDownload PDF (2802K) -
Hisashi Suzuki, Koji Hayashi, Yasuro Taniguchi1982 Volume 29 Issue 7 Pages 256-260
Published: September 25, 1982
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe high temperature oxidation tests for WC-14-Co alloy containing nitrogen, i.e., WC-β(N)-Co alloy (β: WC-TiC, β(N): WC-TiC-TiN solid solution) were made in air at 973-1173K and the results were compared with those of WC-Co, WC-β-Co, WC-β-TaC-Co alloys, etc.
The oxidation resistance of WC-fl-Co alloy was remarkably improved by the nitrogen addition. The beneficial effect of TaC addition on the resistance was confirmed. The oxidation of cemented carbides was found in common to be controlled by the reaction at the interface between oxide layer and alloy matrix. The improvement in oxidation resistance of the alloys containing nitrogen or TaC would be understood in view of the fact that β(N) or triple carbide particles, being considered to act as obstacles to the diffusion of oxygen, inclined to remain unoxidized in the scale near the interface.View full abstractDownload PDF (3438K)
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