Journal of the Society of Materials Science, Japan
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
Volume 17 , Issue 177
Showing 1-25 articles out of 25 articles from the selected issue
  • Yasumichi OISHI
    1968 Volume 17 Issue 177 Pages 454-458
    Published: June 15, 1968
    Released: August 20, 2009
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  • Hirotaro KAMBE
    1968 Volume 17 Issue 177 Pages 459-466
    Published: June 15, 1968
    Released: August 20, 2009
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  • Problems on the Ordinary Sedimentation Methods
    Akinori MUTA
    1968 Volume 17 Issue 177 Pages 467-474
    Published: June 15, 1968
    Released: August 20, 2009
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  • Yoshikazu SADAHIRO, Kiyoshi SHIMIZU
    1968 Volume 17 Issue 177 Pages 475-479
    Published: June 15, 1968
    Released: August 20, 2009
    The purpose of this study is to obtain the fundamental information of physico-chemical properties of commercial NiO powder in the grinding process. The effects of dry grinding by ball-milling for hundreds of hours on the physico-chemical properties of the powder have been studied by X-ray diffraction, BET adsorption, air permeability, spectroscopic reflection, and some other methods.
    The following results have been obtained:
    (1) As the grinding proceeds both the lattice distortion and the surface area determined by BET method increse gradually. During the early stage of grinding, both the crystallite dimension and the surface area determined by permeability method decrese, and the apparent density increases considerablly, but those take almost constant values in further grinding. It is suggested that a non-crystalline substance is not produced by dry grinding.
    (2) The catalytic activity increases with increasing lattice distortion in the early stage, but increases with increasing surface area determined by BET method in the final stage.
    (3) The reflection spectra of the ground NiO exhibit characteristic peaks at 420, and 670mμ. In an early stage, the absorption in the range of visible ray increases considerablly.
    (4) When the ground NiO powders are heated at various temperature for about 3 hours, both the lattice distortion and color tone become nearly the same as the original powder. Then occur both loss in weight on heating and increase in crystallite dimension.
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  • Akiko IKEKAWA, Nobuyoshi KANENIWA
    1968 Volume 17 Issue 177 Pages 480-483
    Published: June 15, 1968
    Released: August 20, 2009
    A new tapping folumula applicable both to coarse and fine particles was discussed in order to investigate the effect of internal friction and cohesive force among the powder particles on the tapping.
    Sodium borate and boric acid (40∼800μ of mean particle diameters) were tapped in solvents, and thirteen other kinds of organic and inorganic fine powders in air and in solvents.
    The following folumula was found to be applicable comparatively well to all the cases investigated.
    p, q, r: Constants
    In sodium borate and boric acid, parameters p and r remarkably decrease, and q increases, with the decrease of the particle size in the region smaller than the critical size obtained for the loosest packing in each solvent. In the case of fine powders, the same tendency is also found for the dependency of the parameters on the angles of the repose. The presence of critical particle size has been confirmed below which the angle of the repose and porosity in loosest packing increase remarkably with the decrease of the particle size. This phenomenon can be explained by the assumption that the cohesive force among the powder particles are negligibly small in the region above the size, but it influences on the angle and porosity in the region below that. It is considered that parameters p, q and r are related to the internal friction and the cohesive force among the powder particles.
    By the transformation of Kuno's and Kawakita's equations to the type representing -dεn/dn with the term of porosity, tapping constants k1 and b(1-a)/a are obtained, respectively. These constants have the similar property as parameter p that they decrease with the increase of the internal friction and the cohesive force among the particles in fine powders.
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  • Yoshiki SANOH, Kenji MITSUDA, Kenjiro MOTEGI, Eiichi TERADA
    1968 Volume 17 Issue 177 Pages 484-488
    Published: June 15, 1968
    Released: August 20, 2009
    The processes of segregation in binary particulate solid mixture were studied by photographing and comparison of the tapping curves. The steel ball, lead shot and spherical glass (these were coarse and regular shaped) were used in this tapping procedure for samples.
    The results obtained were as follows:
    (1) The tapping process of the binary particle mixture was classified into two types, that is, the non-segregation type as shown in Fig. 4 and Fig. 6, and the segregation type as shown in Fig. 5 and Fig. 7.
    (2) It seemed that the tapping process in the non-segregation type was regarded as simple packing process of one component system.
    (3) The concept of“critical diameter ratio of the small particles6)”proved right in the treatment of experimental results. The segregation proceeded when the diameter ratio was smaller than 0.4 and, when more than 0.5 the segregation did not proceed.
    (4) The concept of“critical mixing ratio7)”turned out wrong in this experiment, because the effect of the mixing ratio was more complicated than the particle size ratio.
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  • Kaoru UMEYA, Shigeki KOMATSUZAKI
    1968 Volume 17 Issue 177 Pages 489-494
    Published: June 15, 1968
    Released: August 20, 2009
    It is widely recognized that the three kinds of mechanism, the rearrangement, the elastic and plastic deformation and the cold working fragmentation of particles, take place during the compaction process of powder materials.
    Generally speaking, the compaction of powders is performed under considerably high pressure, and most reports on powder compaction refer to the results of that high pressure where plastic flow or fragmentation of particles predominats.
    In this paper the observation of compacting pressure P1 and of pressure on fixed piston P2 in low pressure range P1=15∼150kg/cm2 is reported, with its analysis based or these observed value according to Shaxby-Unkel equation. Shaxby-Unkel's equation P2/P1=exp[-4βμ(H/D)]is considered to be adequate for considerably high pressure as has so far been proved in many previous papers9)10)12), but it is proved that this equation is still useful if it is converted into the form P2/P1=Cexp[-4βμ(H/D)] even in the case of low pressure range where the process of rearranging particles is predominant. Moreover it depends upon the remarkable effect of internal friction and wall friction whether this equation is favorable or not.
    This converted Shaxby-Unkel's equation was applied to our study, and the product βμ was obtained from the slope of straight line (log P2/P1 vs. H/D) resulting from the compacting test.
    Accordingly, β was calculated using the valve of the product βμ from the compacting test, and the wall friction factor μ from the shearing test.
    β represents the ratio of radius to axial stress, and it is generally the function of internal friction factor μi and of wall friction factor μ.
    Here we confirmed, by substituting μi and μ from our shearing test for the formulas that have hitherto been reported, that the formula of β, derived by Unkel from the treatment using the theories of deformation, plastic and elastic, the theory of elastic deformation, is most suitable in case of graphite powder.
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  • Kunio MATSUI
    1968 Volume 17 Issue 177 Pages 495-498
    Published: June 15, 1968
    Released: August 20, 2009
    In this paper, an index of friability or grindability is discussed from the standpoint of the energy required.
    Until crushing is initiated, the strain energy Ue necessary to the fracturing of geometrically similar bodies is directly proportional to the volume V of these bodies. The values of V/Ue=CII (cm3/kg cm) are called the Crushing Initiation Index.
    The methods to measure the net energy input to crushing in case of impact crushing and the slow compression crushing of prismatic specimens and powdery layers are stated in this paper.
    The net energy input (Ar/W0) evaluated in these methods is directly proportional to the specific surface increase ΔS. The values of ΔS/(Ar/W0)=CEI (cm2/kg cm) are called the Crushing Extension Index.
    The values of CII are found to be the characteristic values of friability of the materials, and CEI are to be those of grindability.
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  • Kazuki MATUDA
    1968 Volume 17 Issue 177 Pages 499-503
    Published: June 15, 1968
    Released: August 20, 2009
    In order to utilize, in the design of continuous vibration mills, the results of the tests hitherto performed of batch vibration mills, in the way of collecting data for their grinding efficiency, an attempt was made to plot the tested samples on one graph, choosing five that were found fit for the comparative studies of both the vibration mills, batch and continuous, in respect of their respective grinding capacity, based on the parameter common to them.
    For this purpose the common parameters, τ=αωJ/U·t for batch grinding, and τ=αωJ·ρ'V/P for continuous grinding were introduced. In the case of continuous grinding, the mean retension time in the drum T was calculated by the relation T=WD/P, and WD was eliminated by using U=WD/ρ'V. This T was equalized with the batch grinding time t.
    By using the results of these operations, it was proved that the data of the batch grinding system and the continuous grinding system which had the strainer type outlet were plotted on one curve of ΔS-τ graph, although in some examples, the batch grinding data were slightly better.
    Then there was found coincidence to be in particle size distribution in both the grinding system, batch and continuous, having the same τ values.
    However, there are many problems to be solved, such as the negative size effect of scaled up drums, and their comparison at critical specific surface value.
    Further studies will be made to confirm this relationship by collecting necessary data.
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  • Shigeki NISHITAKE
    1968 Volume 17 Issue 177 Pages 504-508
    Published: June 15, 1968
    Released: August 20, 2009
    The batch delamination grinding of coarce filler grade kaolin was studied to produce clay of paper-coating grade having about 85per cent ingredient particles of minus 2 micron in spherical diameter. The coarce clay containing 42per cent particles of minus 2 micron in spherical diameter was ground in wet grinding process under the operation of the vibration mill of 2 litre drum for 3 hours. The effect that was made on the grinding efficiency by the quality of the material, the shapes and dimensions of the grinding medium, by the moisture ratio, by the slurry contents of the mill, and by the amplitude and frequency of the vibration, was studied. It was considered that, for the purpose of maintaining highest possible percentage of ingredient particles of minus 2 micron in spherical diameter, the highest efficiency would be realized by grinding the material by means of ceramic balls of 3φmm in diameter. The product containing 90per cent ingredient particles of minus 2 micron in spherical diameter was obtained on condition of moisture ratio 1, of the mill filled with 63per cent slurry, of amplitude 3.1mm, and of 1500 revolutions per minute. The hexagonal tabular crystals got deformed somewhat irregular. It was considered that, for the purpose of operating delamination, the highest efficiency would be realized by grinding the material by means of nylon pellets, but that it would entail reduction in the percentage of ingredient particles of desired fineness to one third as much as the product to be obtained by grinding the material by means of ceramic balls of 3φmm in diameter.
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  • Akinobu OTSUKA, Teruko MATSUMOTO
    1968 Volume 17 Issue 177 Pages 509-512
    Published: June 15, 1968
    Released: August 20, 2009
    The effect of synthetic aluminium silicate of different sizes, pore and mesh, on the adsorption of methylene blue (MB) from aqueous solution has been investigated. Two gels have been employed as the adsorbent, one containing 20.3% alumina (SA-I), and the other 5.2% alumina (SA-III). Between these two gels there is a marked difference in the distribution of pore volume. SA-I has many macropores and SA-III abounds in micropores.
    Adsorption of MB cations by SA-I reaches its equilibrium in relatively a short time. On the other hand, the adsorption by SA-III is at very low rate and takes many hours to attain its equilibrium. It is supposed that the low adsorption rate is due to the hindrance to the MB's penetration into the micropores of the gel.
    If the mesh size of adsorbent is reduced the rate of adsorption increases accordingly. Plots of x/x against t1/2 for SA-III of various mech sizes are linear, and the rate constant is inversely proportional to the particle's diameter. (x and x are the quantities of MB adsorbed after time t and at equilibrium.) The intercept on the axis of x/x (m) is also inversely proportional to the particle's diameter. This supports the view that m is related to the external surface area of the adsorbent.
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  • Adsorption of Acrylamide on Activated Carbon from Solution
    Hiroshi UTSUGI, Kozo SAKAMOTO, Taketoshi FUJITA, Akio KOBAYASHI
    1968 Volume 17 Issue 177 Pages 513-520
    Published: June 15, 1968
    Released: August 20, 2009
    Adsorption of acrylamide monomer on activated carbon has been measured in various solvents, i.e., water, methanol, chloroform and dioxane. Adsorption of n-butanol in aqueous phase has also been measured. The apparent adsorption isotherms against relative concentration belonged to the BET II type. In the case of aqueous solution, the rising portion of the isotherm was observed even within a relatively low concentration range, and lumpy polymer was observed in the sediment at 25°C in 48hrs. The yield of polymer showed the increase accompanying the increase in the amount of the activated carbon added and of the initial concentration of acrylamide. BET-type multilayer adsorption equation has been derived on the model in which the solute molecules adsorbed on the solute molecules in monolayer were regarded as the second layer molecules in adphase, etc., whilst the solvent molecules may form the only monolayer, because of the difference of structure and of potential in an adphase from those in the bulk solution phase, respectively. The reasonable agreement between the calculated and the experimental and also the reasonable surface areas were obtained in the region of the isotherm less than 0.4 in a relative concentration. These surface areas are remarkably smaller than the value obtained from the argon adsorption at 77°K. These may possibly be explained by the specificity in the structure of the activated carbon (like the turbostratic structure). Since the decrease of the surface area from the argon adsorption at 77°K has been shown by the activated carbon coexisting with the polymer as the sediment, the degree of the surface treatment of the activated carbon could be detected by measuring the surface area through the gas phase adsorption.
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  • Ryozo HAYAMI, Toru OGURA, Ryohei TERAI
    1968 Volume 17 Issue 177 Pages 521-526
    Published: June 15, 1968
    Released: August 20, 2009
    The development of lithium silicate by solid state reaction in mixed powders of Li2CO3 and SiO2 in various mole ratios is followed by thermogravimetric analysis (TGA) and quantitative X-ray diffraction measurement. The powders are used consisting of coarse particle of SiO2 in a fine grained matrix of Li2CO3. Isothermal TGA shows that reaction does not exactly follow either diffusion mechanism or boundary reaction mechanism at the temperature range 680-700°C. The results of X-ray diffraction measurement, however, suggest that reaction probably proceeds by diffusion controlled mechanism at the lower temperature range, 637-662°C. The activation energies obtained by TGA and X-ray measurement are 38 and 130kcal/mole respectively. Such difference of reaction mechanism and activation energy might be attributed, at least partially, to the formation of liquidus phase at the temperature range 680-700°C. Activation energy obtained by dynamic TGA at the temperature range 640-670°C is 87.5kcal/mole.
    In atmosphere, Li2O·SiO2 is primary reaction product and 2Li2O·SiO2 appears somewhat later. In vacuum, on the contrary, 2Li2O·SiO2 is predominant product and Li2O·SiO2 is scarcely detectable. Moreover, the rate of reaction is much smaller in vacuum than in air.
    The studies with the use of the reaction couple with platinum markers indicate that Li is the main diffusing species.
    When the reaction proceeds by the diffusion of Li ion, migration of oxygen ion should accompany it. Therefore, the reaction rate must be controlled not only by the diffusion of Li but by the diffusion of oxygen. The activation energies obtained experimentally are considered to be too high to be attributed to the diffusion of Li even if the lowest value, 38kcal/mole, is taken. Thus, it is probable that the activation energy is connected with the diffusion of oxygen. The driving force of the diffusion-controlled reaction is the concentration difference of the diffusing species between the surface of the reaction product layer and the reaction boundary. In vacuum, oxygen concentration on the surface of the product layer is so much lowered that the rate of reaction decreases considerably. Preferential formation of 2Li2O·SiO2 in vacuum may be the result of accumulation of Li2O on the reaction boundary which is caused by the slow migration of Li into SiO2.
    The whole aspect of reaction in air will be represented as follows:
    Li2CO3 2Li2O·SiO2 Li2O·SiO2 SiO2
    Diffusion 2Li++O2- 2Li++O2-
    Phase boundary Li2CO3 Li2O·SiO2 SiO2
    reactions -CO2 +Li2O +Li2O
    =Li2O =2Li2O·SiO2 =Li2O·SiO2
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  • Ryohei TERAI, Iwao SUGAE, Ryozo HAYAMI
    1968 Volume 17 Issue 177 Pages 527-530
    Published: June 15, 1968
    Released: August 20, 2009
    The reaction in a solid state of mixture of powdered sodium carbonate and silica systems in various mole ratios was followed by thermogravimetric analysis (TGA), X-ray diffraction and RI-tracer technique. The powders consisting of coarse particles of silica in a fine grained matrix of sodium carbonate were used.
    The isothaml TGA shows that the reaction does not exactly follow simple diffusion mechanism at the temperature range 750∼835°C. The rate data are best described by the Crank equation which is given to the reaction which is controlled both by the diffusion of one of the reactant through a product layer on the surface of the second spherical reactant and by the rate of phase boundary reaction at their reactant interface:
    where Mt/M is the fraction of reaction, D is the diffusion coefficient, βn are the positive root of the equation, βn·cotβn+L-1=0, L=a·k/D, a is the radius of the particle, k is the rate constant of the phase boundary reaction.
    The diffusion coefficient calculated from penetration of 22Na into the fused silica is 5, 0.10-11cm2/sec and well agrees with the diffusion coefficient calculated by the Crank equation from the present data. Since the self-diffusion coefficients of sodium ions in the glass Na2O-SiO2 system are in the order of 10-7-10-8cm2/sec at the temperature range 300∼450°C and their activation energies are about 15kcal/mole, it is found that the diffusion of sodium ions does not control this reaction.
    In atmosphere, meta-silicate is the primary reaction product but this disappears somewhat later. In vacuum, meta-silicate is scarcely detectable, and the rate of its reaction is much smaller than in air, and their behavior are similar to the reaction of Li2CO3-SiO2 system.
    The reaction scheme in air will be represented as follow:
    Na2CO3 2Na2O·SiO2 Na2O·SiO2 SiO2
    Diffusion 2Na++O2- 2Na++O2-
    Phase boundary Na2CO3 Na2O·SiO2 SiO2
    reactions -CO2 +Na2O + Na2O
    =Na2O =2Na2O·SiO2 =Na2O·SiO2
    It is inferable, therefore, that the diffusion of oxygen ions through the product layer of silicate and the phase boundary reaction control the whole reaction.
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  • Hisashi IMAI, Shinobu HOSAKA
    1968 Volume 17 Issue 177 Pages 531-535
    Published: June 15, 1968
    Released: August 20, 2009
    (1) Compacting effects on the reaction rate of mixed powders were studied. The effects of the apparent density, shape, specific surface area of compact, and of the particle-size of the starting materials were examined. The reaction employed for the study was the formation of thorium carbide, as follows.
    1) Thorium metal+Carbon→Thorium carbide. (Addition reaction)
    2) Thorium oxide+Carbon→Thorium carbide. (Exchange reaction with degassing)
    (2) The reactants were mixed to less than 0.2wt% standard deviation of C/ThO2 for the five sampling. Then, “tablet” compacts 1.25cm in diameter and weighing approximately 1.0g were produced under different pressures respectively. Moreover to study the shape effect, the compacts 0.63cm in diameter with different densities were formed.
    All the compacts having different densities were placed in a graphite crucible and heated to the specified temperature in a vacuum of 10-4mmHg. The degree of reaction was measured as the percentage of reacted thorium to total thorium.
    (3)-1 The effect of the apparent density: On the addition reaction, the reaction rate increased with the density of the compacts nearly in all of its range. However, this increase in the reaction rate became saturated beyond a certain value in the range. It was considered that the saturation was caused by the disappearance of active points in the compact.
    On the other hand, the reaction rate of the exchange reaction with degassing showed a minimum value at a certain value of compacting density.
    (3)-2 The shape effect of the compacts: This effect on the reaction rate was also observed. On the exchange reaction, the minimum value of reaction rate shifted to the lower density side for the cylindrical group than that of the tablet group. This was thought to have been caused by the difference of density distribution in the compacts.
    (3)-3 The effect of the particle-sizes of the starting materials: This effect on the reaction rate depended on the shape of the particle. The particle having a granular form had a size effect on the reaction rate, but this effect was not observed in the particle with a flaky form, such as graphite powder, possibly due to the layer arrangement of flaky particles in the compact.
    (3)-4 The effect of the specific surface area of the compacts: This effect on the reaction rate was observed in the exchange reaction with degassing.
    (4) For the study of the chemical kinetics for pressed mixture it was necessary to keep constant the apparent density, shape and size of the compacts. Unless this constancy was maintained it was not possible to obtain accurate activation energy for the reaction.
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  • Shinichi OTSUKI, Shoji HORI, Kanji MATSUO
    1968 Volume 17 Issue 177 Pages 536-539
    Published: June 15, 1968
    Released: August 20, 2009
    Graphitized carbon products contain anisotropy in their own properties. Its degree depends on the condition of filler and binder. Soft carbon such as petroleum coke, is used as filler material, and tends to become needlelike particles when crushed. The crystallites of graphite orient along its length. By extrusion, these coke particles line up selectively in the pressing direction, whereby anisotropy grows, and in molding process, those ones line up perpendicularly in the pressing direction.
    Meanwhile, the product kept under compression during carbonization get shrunk in its own volume, and then it shrinks again in graphitization process. Accordingly, such product results in possessing higher density than usual product.
    In this investigation, the carbonization under compression, purposed to increase in apparent density of carbon product, was carried out. The orientation of crystallite grown in the sample was estimated from the anisotropy in electrical resistance, thermal expansion, and X-ray diffraction obtained.
    The following results were obtained:
    (1) The products from carbonization under compression of mixture of petroleum coke powders and binder possessed more anisotropy than usual molded products. This fact suggests that the compression facilitated the flow of the particles.
    (2) The samples from the pre-extruded product, carbonized under compression, possessed less anisotropy than usual extruded products. It is considered that the effect of extrusion on orientation and that in molding interacted reciprocally.
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  • Genji JIMBO, Sadao ASAKAWA, Naoto SOGA
    1968 Volume 17 Issue 177 Pages 540-544
    Published: June 15, 1968
    Released: August 20, 2009
    The adhesion force of silica sand, limestone and copper powder beds were measured with the split cell type tensile strength measurement method, which had been developed by Ashton, Farley and Valentin4), and later modified by the authors. The effect of porosity change on the strength of powder bed, σz, was measured and correlated with the function of porosity, (1-ε) k, which had been proposed by Rumpf5)6) in Eq. (1).
    These results reveal that the relation between σz and (1-ε) k does not follow the proportionality which is shown in Eq. (1), and so the adhesion force at a contact point, H, is also affected quite severely by the compacting conditions as are shown in Figs. 4, 5, 6.
    The effect of compression force was investigated with two different compacting methods, compression and tapping. The results show that the adhesion force of the powder bed by compression is usually larger than that by tapping at same porosity as are shown in Figs. 4, 5.
    From these results and another consideration which the authors made4), it is suggested that the adhesion force of powder is affected not only by the factors which Rumpf analysed but also by the change of contacting condition, perhaps contact area, at the contact point of particles.
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  • Masafumi ARAKAWA, Misao NISHINO, Eiji SUITO
    1968 Volume 17 Issue 177 Pages 545-549
    Published: June 15, 1968
    Released: August 20, 2009
    The viscosity of powder was measured with the rotational viscometer in a vibrating state. In this experiment, the outer cylinder of Stomer viscometer was tightly connected to the vibrator which had constant frequency (120cps), and the amplitude was varied by changing the voltage applied to the vibrator. The α-alumina powders with several kinds of particle sizes were used as samples.
    The flow curves, obtained of powders of various particle sizes under different amplitudes and temperatures, were found to be similar to one of non-Newtonian liquids. When the amplitude decreased, each powder behaved like a continuous solid.
    The apparent viscosity was obtained from these flow curves in relation to the different amplitudes and particle sizes. At a constant rate of shear and large amplitude, the apparent viscosity decreased with decrease in particle size. When the amplitude was sufficiently small, the apparent viscosity reached its minimum at a definite particle size. It was considered that in the fine powders their coagulated secondary particles moved as flowing units, and that these coagulated particles were broken into primary particles with increase of amplitude.
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  • Jun'etsu SETO
    1968 Volume 17 Issue 177 Pages 550-554
    Published: June 15, 1968
    Released: August 20, 2009
    The interfacial electrokinetic potential (zeta potential) and the dielectric dispersion were measured as the electrical properties of precipitated CaCO3 suspension containing various electrolytes, and based on these data, the filtration behaviors were observed.
    The results obtained are as follows.
    (1) Concerning the stabilizing process of the suspending particles due to the addition of sodium hexameta-phosphate, the increment of average specific resistance α of filter cakes corresponds closely to the changes of the zeta potential ζ and the dielectric properties.
    (2) On the process to be unstable in the case of CaCl2 or Ca(OH)2 addition, the resistance α also relates closely to the interfacial electrical properties.
    From these observations, the following type of empirical equation can be derived.
    Here, α0 is the average specific resistance at ζ=0 and is inherent to the suspending system. k and s are constants representing the dependency of α on the zeta-potential.
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  • Shin ONO
    1968 Volume 17 Issue 177 Pages 555-559
    Published: June 15, 1968
    Released: August 20, 2009
    In this paper the author reports the effects of magnetic property on the dispersion of iron oxide powders in solvents. Acricular γ·Fe2O3 and α·Fe2O3 powders have been chosen for specimens. The dispersibility and its time variation have been measured by the size distribution of flocculated particles for various method of dispersion in solvents which are mostly hydrophobic type.
    The results of measurement show that α·Fe2O3 has far better dispersibility compared to that of γ· Fe2O3. The least effective diameters measured as median of the size distribution below 20μ which correspond to the best dispersion are 3.0μ and less than 0.7μ for γ·Fe2O3 and α·Fe2O3 respectively.
    It is found that the dispersibility of γ·Fe2O3 in the solvents is inversely related to the magnetic property, especially to the residual magnetization of the specimen. The unit particles of γ·Fe2O3 are considered to be composed of still smaller particles and to behave as a single domain magnet. The residual magnetization gives a measure of the magnetic attraction which sets the limitation and order of dispersibility.
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  • Yasushi SAWAHATA
    1968 Volume 17 Issue 177 Pages 560-563
    Published: June 15, 1968
    Released: August 20, 2009
    In the mixing of binary component system of fine powders which have different values of specific gravity, the value of the specific gravity of the mixture at its perfectly mixed state is predictable when the respective values of the specific gravity of the components and their mixing ratio are known. Therefore, using this predictable value of specific gravity of the perfectly mixed mixture as the representative value of the system and obtain the sample variances concerning the values of the specific gravity of the samples drawn from the mixture in the process of mixing, the variance value will become a measure to evaluate the mixedness of the mixture whose components have different values of specific gravity.
    On this consideration, the author proposes a new method devised on the values of the specific gravity of the mixed components to evaluate the mixedness of the mixture. The experimental study was carried out to determine the utility of this method and the usefulness in practical operation of mixing was confirmed.
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  • Masashi SUZUKI, Seiki WATANABE, Shoozoo HONGO, Tsutomu OOHATA
    1968 Volume 17 Issue 177 Pages 564-569
    Published: June 15, 1968
    Released: August 20, 2009
    In order to establish the method of experimental inhalation study of hazardous radioactive aerosol, including that of Pu compounds, studies have been made on a modified Dautrebande Aerosol Generator (Type D30a), with regard to the relation between the concentration of dispersing solution and that of dispersed aerosol as well as its size characteristics for some inorganic salts (NaCl, SrCl2, PrCl3, Ce (NO3)3.)
    Regardless of the difference of materials examined, the concentration of dispersed aerosol exactly depends on that of solution with linear relationship, when the flow rate of jet air is constant. The size distribution of dispersed aerosol is slightly diverged from the log-normal distribution, presumably because of the larger portion of the aerosol being cut off by the mechanism of generation and of other characteristics of the generator. Nevertheless, the mass median diameter of the solidified aerosol of a given salt directly measured on the cumulative mass distribution curve indicates linear relationship with cubic root of the concentration of solution of the salt. (Ce Nitrate is different, though.) The theoretical analysis of the case offers the following suggestions. Assuming that the total amount and size distribution of the mist at dispersion is always constant with one generator at the constant flow rate of air, regardless of kind and concentration of dispersing solution, the relation between MMD of the mist and that of corresponding solidified aerosol is expressed by the equation (D/2)3R=β(φ/2)n, since the mass of the salt included in a mist particle must be equal to that of the corresponding aerosol particle. Here D and φ are diameters of the mist and of the corresponding solidified particle, R being the concentration of the solution, while β is a constant related to the density of aerosol and n is a parameter related to the solidifying characteristics of aerosol. In case of chloride salts examined, n=3, indicating its solidifying tendency, equally applies to all directions. In case of Ce nitrate n seems to be less than 3 (about 2) that means that the solidifying tendency is different in some directions. Thus, in case of chloride salts, since D and β are constant for a given kind of solution, φ must be linearly proportional to 3R. (In case of Ce Nitrate, approximately proportional to 2R)
    Therefore it is concluded that we can easily obtain radioactive submicron aerosol and control the concentration and size characteristics of the dispersed radioactive aerosol of a given salt (solidified by evaporation), within certain limitations, by changing the concentration and specific activity of the salt solution, with the generation technique.
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  • Ayao TAKASAKA, Yasusi ABE
    1968 Volume 17 Issue 177 Pages 570-573
    Published: June 15, 1968
    Released: August 20, 2009
    Most of the existing gravitational sedimentation methods have shortcomings in the particle size determination of powders below about 2 microns.
    For example, 2 micron particles of kaolinite powder (density=2.65), require about 15.5 hours to settle 20cm in water under gravity at 20°C.
    Moreover convection and displacement current all tend to disturb the sedimentation.
    The centrifugal photo-extinction method is based upon the determination of the opacity of suitable dispersing liquid caused by the suspension of the powder in a centrifugal field.
    However, the lack of knowledge in the basic law of transmission of light through the suspension in a centrifugal field leaves the method still open to question.
    For this reason first we studied the centrifugal photo-extinction apparatus and the method of measurement by its means.
    Secondly we studied the effects that this centrifugal photo-extinction method of measurement would have on the particle size distribution of kaolinite in respect of the reproducibility, the dispersion agent and the concentration of powder, and made comparative studies of various other effects that other methods of measurement would have.
    We have found the centrifugal photo-extinction method to be adequate with considerable accuracy for the determination of the particle size of fine powders.
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  • 1968 Volume 17 Issue 177 Pages 574-577
    Published: June 15, 1968
    Released: August 20, 2009
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  • Introduction to Soil and Rock Mechanics
    K. Akai, T. Shibata, S. Sakurai
    1968 Volume 17 Issue 177 Pages 579-584
    Published: June 15, 1968
    Released: August 20, 2009
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