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Volume 10 (1963)
- Issue 6 Pages 231-
- Issue 5 Pages 184-
- Issue 4 Pages 138-
- Issue 3 Pages 83-
- Issue 2 Pages 44-
- Issue 1 Pages 3-
Volume 10, Issue 6
Displaying 1-4 of 4 articles from this issue
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Syoichi Mochizuki1963 Volume 10 Issue 6 Pages 231-235
Published: December 25, 1963
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSIn order to estimate the behaviour of particle shape on determination of particle size by sedimentation method, effective diameters of some typical shaped specimens such as sphere, cylinder and plate were compared with equivalent and projective diameters. And the deviations between effective and projective diameters of some metal, powder (sphere, granular and plate) 'were studied by comparing with the results of model specimens. For the spherical and granular specimens, the deviations of effective diameter from equivalent or projective diameter were none or negligible, but the results of long cylinder and thin plate specimens vary greatly by the elongation of cylinder or the flakiness of plate.
These results, which could be adapted to metal powder, were showed graphically in this paper.View full abstractDownload PDF (1420K) -
(I) The Compression Equation and the Anomaly of Infrared Spectra of Pellet MethodKimio Kawakita1963 Volume 10 Issue 6 Pages 236-246
Published: December 25, 1963
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSWhen powders are compressed statically by the piston compression the porosity decreases. The typical example of the process of po-wder compression indicates the various forms according to the nature of powder as shown in Fig. 1. In the previous reports the author already confirmed that the relationship between ratio of compressed volume C=(V O-V)/V O and pressure P is represented in the following equation :
C=(V O-V)/V O=ab P/(1+b P),
where V O= initial volume of powder, V O= volume of powder under static load P, a and b are the characteristic constants of powder.
"a" corresponds to the limiting value of ratio of compressed volume C ∞, that is the initial porosity. "b" corresponds to the coefficient of compression and has the meaning related to the rheological behavior of powders. In the case of ordinary powders "a" indicates the value 30 to 800 (Table 1).
From the above equation we get
P/C=1/ab+1/aP.
The plot of P/C against P from this equation will give a straight line of positive slope 1/a, with an intercept 1/ab. It is as shown in Fig. 2. The applicability of this equation is of a wide range of compression process. This equation comprises the Athy's equation and also the applicability is better than the equations of Balshin and Nutting as shown in Fig. 4. When compressed powders became free from load, the volume expansion took place as shown in Table 1.
Concerning the relation between the porosity and the shape of particles of powders the author examined the difference of spherical and non-spherical powders as shown in Table 2.
In the case of tapping compression, if we take the tapping number instead of P, the good applicability of its process was observed as shown in Fig. 5.
Besides these, in relation to the anomaly in the infrared spectra, the author observed that the double decomposition reaction between oxalic acid or some oxalates and alkali halide took place by the powder compression (Table 4, Fig. 6, 7, 8.). In this case it was confirmed that the presence of water vapor played an important part in these reactions.View full abstractDownload PDF (625K) -
Tadashi Ogura, Itsuo Kawasaki, Kosho Watanabe1963 Volume 10 Issue 6 Pages 248-257
Published: December 25, 1963
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSChanges of the properties of UO2 compacts such as density, porosity, weight, O/U ratio and average grain size, with increasing sintering temperature were determined for three different kinds of UO2 powder, varying the sintering atmosphere. Hydrogen, vacuum and several combinations of these were compared. Conditions of compacting, sintering time, both heating and cooling rates were fixed constant throughout the experiment.
In the intermediate stage of sintering, it was revealed that the temperature range where the pronounced progress of densification occured was 200 to 300°C lower and that more marked grain growth was encountered in vacuum, compared with in hydrogen. As the kinetics of such acceleration of sintering, the followings were suggested. In. hydrogen atmosphere, the finer the particle size of the powder, the higher the surface energy, and thus the easier the sintering. In vacuum, the relation was similar so far as the particle size of the powder was concerned. Furthermore, it was concluded that the retention of higher excess oxygen content to the temperature higher than 1, 000°C, the activation of the surface layer of the powder by the low pressure, and the cleaning of the powder surface by the desorption of adsorbed gas could be the main mechanisms of acceleration of sintering in vacuum.
In the last stage of sintering, however, more closed pores were inclined to appear in vacuum compared with in hydrogen, which inhibited the grain growth, and the weight loss by mass evaporation became remarkable.View full abstractDownload PDF (4105K) -
Tamotsu Fukatsu, Tsuneo Sasahara1963 Volume 10 Issue 6 Pages 258-265
Published: December 25, 1963
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSIt is stated that the technique termed Electron Microfractography may become an important tool in an analysis on metal fracture. In the present work an application of this technique was examined to reveal the details of failure phenomena of sintered WC-Co alloy. Characteristics of failures were classified in three types from the feature of fracture surfaces. They are type A of cleavage steps fractured in WC grain, type BC of flat or lined face fractured in WC-WC grain boundaries or WC-Co inte-rfaces and type D of tear drops fractured in cobalt layer. On the basis of this classification, a model diagram of the fractures associated with WC grain size and cobalt content was drawn. 1) Type A appeared in the region where WC grain size is larger than about 5μ and Co con-tents are less than about 15%, 2) Type BC appeared in the region where WC grain size is smaller than about 2μ and Co contents are less than about 7%, 3) Type D appeared in the region where WC grain size is smaller than about 4μ and Co contents are more than about 20% and 4) Mixed types of fractures appeared in the intermediate regions between above three regions. This diagram was very useful for the Electron Microfractography of sintered WC-Co alloys.View full abstractDownload PDF (10031K)
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