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Volume 26, Issue 3
Displaying 1-6 of 6 articles from this issue
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Norihiko Nakanishi, Mikio Takano, Chiyuki Yasuda, Hiroshi Kumito, Nobu ...1979 Volume 26 Issue 3 Pages 79-83
Published: April 25, 1979
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSPreparation of fine powders of a Cu-Al2O3 dispersion strengthened alloy has been tried by means of "Freeze-Drying Processing" (F.D.P.). Fine mixed powders of Cu-and Al-sulfates produced by F.D.P. were oxidized by heating up to 1000°C for 5 min and then reduced by hydrogen gas at 550°C for 2 hr, finally objective fine powders of a Cu-1.5 at% Al2O3 alloy being obtained. This alloy powder was further densified by hot isostatic pressing (H.I.P.).
In addition to several tests such as thermal gravimetry, differential thermal analysis and X-ray diffraction, scanning electron microscopy was applied to observe the structure of the sulfate powders obtained by F.D.P., the alloy powders obtained after the reduction of oxides and a high density alloy obtained by H.I.P.
A comparison of some basic powder properties such as particle size, particle shape, size distribution, etc among three kinds of Cu-Al2O3 powders obtained by freeze-drying process from aqueous solution, co-preci-pitation method and freezing process from molten salts was carried out and relative characters of these powders have been understood somewhat clearly.View full abstractDownload PDF (3109K) -
Nobumasa Ohshima, Yoshio Enoki1979 Volume 26 Issue 3 Pages 84-89
Published: April 25, 1979
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA new preparing process of photoconductive CdSe powders suitable for an EL-PC-type X-ray image converting panel was proposed.
The influence of parameters such as amount of flux and activator in the raw mixture, firing temperature and firing atmosphere on the photoconductive characteristics was investigated. To keep the amount of flux minimum was not only effective to improve the photosensitivity, threshold voltage and granularity of resultant photoconductive powders but also effective to make the preparing process simple and reliable.
Applying such improved photoconductive powders to a solid-state X-ray image converting panel, the brightness and resolution of the panel was remarkably improved.View full abstractDownload PDF (403K) -
Masaya Miyake, Akio Hara, Tadamasa Sho1979 Volume 26 Issue 3 Pages 90-95
Published: April 25, 1979
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA continuous two-stage carburization furnace whose first furnace has a nitrogen atmosphere and whose second one has a hydrogen atmosphere was developed. A mixture of WO3 and C was pelletized and resulting powders were heated continuously as they moved from the first furnace to the second furnace. The severe control of the carbon content of the product was possible by this two-step carburization method. The grain size of WC powder could easily be controlled by the heating temperatures of the first and the second furnaces. The grain size distribution thus obtained was uniform and narrow.View full abstractDownload PDF (2982K) -
Shiro Kohara, Kiyohiko Tatsuzawa1979 Volume 26 Issue 3 Pages 96-99
Published: April 25, 1979
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe relationship between tensile strength and porosity in sintered compacts of low density was investigated. Porosity dependence of tensile strength in the low density range was shown in a modified form of the exponential type equation for the middle porosity range. Thus, the relationship between tensile strength and porosity can be represented by the following equations. For the low density range,
S=(m-nP) exp(-bP) (P1<P≤P0),
for the middle density range,
S=S0 exp(-bP) (P2<P≤P1),
and for the high density range,
S=(Ss+kPa) exp(-bP) (P%le;P2),
where S is the tensile strength, P, the porosity, and S0, Ss, a, b, k, m, n, P0, P1 and P2, empirical constants.
The empirical constants were experimentally determined. The obtained equations for the low density range were as follows;
S=(62.3-197P) exp(-5.6P) [kg/mm2] (0.14<P≤0.23)
for sintered copper compacts, and
S=(281-1000P) exp(-3.7P) [kg/mm2] (0.24<P≤0.28)
for sintered iron compacts.View full abstractDownload PDF (1645K) -
Toshihiko Akiyama, Hidenori Yuasa, Hiromitsu Yamada, Keiichiro Shoji1979 Volume 26 Issue 3 Pages 100-104
Published: April 25, 1979
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSSintered Cr-steels containing 1-3% Cr were prepared from the mixtures of iron powder, Cr3C2 powder and graphite powder, by compacting and sintering at 1250°C in vacuum. Specimens were nitrided at 500°C in an ammonia gas atmosphere, and the nitrided layer was examined. The results obtained are as follows:
(1) Specimens containing more than 2%Cr give nearly same hardness distribution pattern after nitriding for 1 hr, compared with that of conventional Cr-steel nitrided for long time.
(2) Rapid nitriding is due to the penetration of nitriding gas through pores of specimen, therefore nitrides are formed on the inner surface of pores and grain boundaries connecting with pores.
(3) Although sintered specimens absorb large amounts of nitrogen, an X-ray diffraction pattern of the surface layers clearly shows a phase peak. This peak shifts to lower angle direction with an increase of Cr content, which shows lattice strain of a phase, and may contribute to the hardness increase.View full abstractDownload PDF (1749K) -
Hiroyasu Mitani, Masaru Yokota, Kenji Suzuki1979 Volume 26 Issue 3 Pages 105-109
Published: April 25, 1979
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIn the previous work we have already confirmed that the sintered Cu-14 wt%Al-8 wt%Ni ternary alloy composed of single γ′ martensite phase showed the highest damping capacity among these sintered ternary alloys. We are going to examine this alloy as a self-lubricating noiseless bearing in this paper.
The results obtained were as follows:
(1) It was confirmed that this sintered γ′ Ni Al-bronze had better performances as a bearing especially at higher speeds with heavier loads in the bearing performance test.
(2) Both the temperature increase (ΔT) and the friction coefficient (μ) of this alloy were lower than those of Cu-10 wt%Sn and Fe-10 wt%Cu sintered alloys having PV (load × velocity) values more than 1300 and 600 (kg/cm2·m/min) respectively.
(3) Comparing the vibration-pattern of γ′ Ni Al-bronze with those of Cu-l0 wt%Sn and Fe-10 wt%Cu sintered alloys, we can confirmed that the vibration absorption of γ′ Ni Al-bronze was better than those of the others.
(4) According to the results of internal friction measurements, the maximum damping of γ′ Ni Al-bronze is uncomparably higher than those of Cu-10 wt%Sn and Fe-10 wt%Cu alloys, and the damping capacity of the Cu-Sn alloy is a little higher than that of the Fe-Cu alloy. Since it is well known that the damping capa-city is proportional to the acoustic absorptivity, it may be considered that the noiseless pattern of γ′ Ni Al-bronze gives its good performance in acoustic behavior, judging from some similarities between the results of internal friction and vibration-patterns of the above three specimens.View full abstractDownload PDF (1421K)
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