Hydrogen reduction experiments were carried out on the unirradiated and the γ-irradiated nickel oxide (NiO) in order to interpret their mechanism at the initial stage of reduction, i.e. the induc-tion period. The reduction velocities were found to decrease with the radiation dose, being remark-able over a total dose of 5.8×107γ. These phenomena are similar to the increase in the excess oxygen in the nickel oxide by irradiation. From the experimental results of the effect of the preevacuation at various temperatures on the initial reduction kinetics, it was concluded that the reduction kinetics of nickel oxide was associated with the amount of surface excess oxygen by γ-irradiation. It was suggested that the increase ofinduetion period by irradiation was due to the water vapor on the surface of nickel oxide acting as a barrier-layer against the diffusion of hydrogen.
The adhesive property of powder is known to be very variable and also to be affected by the surface condition of the particle. In this experiment, the relation between the surface states of par ticles and the adhesive property of powders has been studied. The white alundum, calcium carbonate and kaolin clay were used as sample powders. The surface condition of white alundum and calcium carbonate were varied by adsorption of capric acid or sodium stearate, and kaolin clay were heat-treated. The adhesive property has been measured by final packing density ρf and coe fficient K1 in Kunos' equation at the first stage of packing or cons tant b in Kawakitas' equation by the same tapping compress method. The attraction force between the particles at the contact point were measured by shearing test of powder bed. The results obtained are summarized as follows: The effect of surface adsorbed layer of capric acid on white alundum is very small compared with the influence of the particle size. But the treatment of calcium carbonate by sodium stearate is effective, and especially the packing density is affected largely, at humid atmosphere. The effbct of this distinction of surface treatment upon both the powders is presumed to be due to the difference of mechanism of surface adsorption. The adhesive property of kaolin clay when heattreated, has changed remarkably at the fall of temperature of the crystal structure. The observed variation of the adhesive property has been compared with the reduction of the surface active site. The adhesive force at the contact point between the particles is not influenced by the surface adsorption layer on the white alundum.
The present paper is concerned with the effects upon durability, of the bond of antacid, magnesium silicate. On the correlation between the durability and structure of antacids, Armstrong et al. reported that the more amorphous magnesium silicate was the more durable it was. Scarecely, however, have studies been made yet upon the kind of factors for durability such as the interaction, bonding state and surface chemistry between silica and magnesia. In the antacid activity test, magnesium silicate showed variation from the theoretical HCI consumption quantity, and this variation was considered to be directly connected with durability. The authors paid special attention to the bond between silica and magnesia as an important factor, and conducted measurements of the differential thermal analysis, IR-ray absorption, X-ray diffraction and surface area with the samples differing in calcining temperature and composition, and also with the comparative specimens (silica-magnesia mixture). On the other hand, studies were conducted on the kinetics of the antacid activity test, irreversible adsorption and exchange reaction of H36Cl gas over the surface of the samples, in order toexamine the mechanism and structure of indicating durability. It is concluded that the durability is influenced by the weak bonding nature between silica and magnesia especially in the region of, in the stable state.
The objective of this investigation was to study the pulvarization effect of the grinding process of γ-Fe2O3 powders, which was used in magnetic tapes. In general, the particles of these powder were in acicular shape. The initial sizes, varying from 0.3 to 0.4 microns in length were reduced in 312 hours of grinding to average particle sizes about 0.14μ, and the particles turned cubic in shape. The coercivity, saturation induction and residual induction of the powders were reduced through-out the run. The magnetic tapes which were produced by using these ground powders have shown the decrease of frequency sensitivity and layer-to-layer signal transfer with increase of grinding time.
It is important, in order to understand the mechanical behavior of powdered materials in the operation of mixing, kneading, transporting and forming procedures, that we should be acquainted, among others, with the properties of their internal friction. For the measurement of internal friction of powdered materials, direct shear tests of various sorts have hitherto been performed. This work was undertaken to determine the relationships between the vertical load σ and the shear stress τ of the consolidated powder beds by a direct shear test. The powders were consolidated into cylindrical forms each of 2cm in diameter and 3cm in length by pressure up to 191kg/cmcm2 for lactose and magnesia clinker powders and 955kg/cmcm2 for aluminapowders. These powder beds were measured, the shear stresses τ against the various vertical loads σ, by direct shear test a pparatus which was equipped with a vertical loading system (hydraulic press), a shear cell, a shear force measuring device (loop gauge) and a shearing force device. It was found that the σ-τ relationships can be represented by the formula where k, σ0 and n are constants. Discussion is made on the influence of the degree of consolidation, water content and particle size, on these constants, with necessary descriptions.
The theoretical considerations on the packing characteristics of powder bed, using the components so called "gap grading" powder systems, were already performed by Westman and Hugill in 1930.McGeary investigated these properties more accurately in 1961, using many sphere-like powders. These investigations were limited to the study of the relation between the groups having equal diameters respectively. The study of the relation having continuous grading has in this way beenrarely made hitherto. In this paper, observation has been made of the packing characteristics of the two-component powder systems having a diameter ratio nearly of unity. The theoretical equation (3) was delivered in the range of high concentration of the coarser grains, and the equation (4) was determined too in their low concentration respectively. To ascertain the validity of there equations, several powders illustrated in Table I and II, were used, and the results obtained from these measurements perfectly agreed with the tendency concluded from the equations (3) and (4).
Studies have been made of the adsorption of some organic vapours on various powders and solid supports for gas chromatography by the elution method with Shimadzu Sorptograph Model ADS 1A, and also about nitrogen by the continuous flow method, which required a slight modification of the flow line in the instrument. The results give a typical BET type adsorption. It was obserbed that the surface areas of the solid supports for gas chromatography decreased to 1/5-1/10 through calcination with some flux, and that many of the micro pores were covered by HMDS (Hexamethyldisilazane) silanization; this led to a presumption that big molecules such as acetone, are adsorbed only to its outer surface.
The ultrafine particles in the ashes of burnt pulverized coal are man made minerals, They are the product of burnt pulverized coal used as fuel in modern power plants. About 25 samples of the raw coals and their ashes produced by pulverizing and burning them were collected from 5 different modern power plants in Japan and were studied in the light of pneumoconiosis mineralogy by means of an electron microscope, and by micron photo tub methods and X ray powder methods, and through differential thermal and chemical analyses and Spectrum analyses. The following results have been obtained. (1) The particles of pneumoconiosis minerals in pulverized coals are from 10 to 0.5 micron in size. Their pneumoconiosis mineralogical composition is of non crystalline Carbon and clay minereals in kaoline group and quartz. (2) The particles of pneumoconiosis minerals in the ashes of burnt pulverized coal are from 5 to 0.5 micron in size, and all spherical in shape. Their pneumoconiosis mineralogical composition is of non crystalline alumino silicates and mullite, quartz and feldspar. (3) Pulverized coal yields 6-10% volume of ashes by burning. (4) The volume of SiO2 found in the ashes of burnt pulverized coal varies in proportion to the volume of the ashes. (5) Fe2O3. Al2O3. CaO. MgO. R2O and MnO are found in the ashes of burnt pulverized coal in volume respectively in inverse proportion to the volume of the SiO2 in the ashes. (6) B2O3 is contained in volumes in the ultrafine particles below 1 rnicron in the ashes of burnt pulverized coal, varying in.inverse proportion to the volume of the ashes.