An attempt made to intreduce particle size distribution (PSD) into Carter's equation on solid-state reaction kinetics is herein reported. The PSD introduced into this equation is described as follows: the solid particles to participate in solid-state reaction are sorted into groups n in number, each group consisting of particles of particular size range, and the sizes in each group being arranged in geometrical series. By thus introducing the PSD system into Carter's equations for the n-numberd groups, it is found possible to apply the over-all reacted fraction determined by quantative analysis mathematically to the reacted fractions for each group. Carter's equation modified as above by the introduction of the PSD system has then been applied to the analysis of the reaction The measurements of PSD with the use of ZrO2 and the chemical determination of the over- all reacted fraction as a function of reaction time and temperature have recorded about 100kcal per mole as an activation energy for the reaction.
There has been but little investigation so far made on the rheological behavior of the viscous fluid-solid powder system. This system considerably concerns the field of the electrode technology, the basic refractory engineering and some rubber industry in recent years. The creep characteristics of the pitch-magnesia powder system are observed in this paper, using the creep tester illustrated in Fig 1. The permanent viscosity coefiicient, the retarded elastic com-pliance and the distribution function of retardation time are herein revealed, using the test system of the pitch-magnesia powder system containing the fluid ranging 21.9%-73.7%. When the higher concentration of the solid material is employed, the peak point, in which the distribution function of the retardation time show it's maximum value, is located in the higher value of the retardation time. The maximum value itself, however, is not affected by the concen-tration of the solid matter. The distribution function of the retardation time is affected enormously by the value of ηi and its correlation can be formulated as follows, where, K' stands for the numerical constant, t for the test time, and T for the degree of the absolute temperature. Some additional considerations have been made on the correlation between the per-manent viscosity, the reciprocal equilibrium compliance and the concentration of the solid materials.
Investigation was made of thermal decomposition process of Barium Titanyl Oxalate, a starting material of Barium Titanate. From the results of TGA, DTA and powder X-ray diffraction, the thermal decomposition process of the compound can be represented as follows. (Crystalline state) Amorphous state) (Crystalline state) The powder of Barium Titanate obtained by the process is of very fine particle size. The rate of decomposition can be expressed as the first order reaction between 700°C and 850°C, and expressed as the 1/2 th order reaction above 850°C. The activation energy of the thermal de-composition is estimated at about 13Kca1/mole from Arrhenius plots.
It is well known that the properties of ceramic capacitors are greatly affected by particle size, composition, forming pressure, impurity and firing temperature. Though there have been many reports made concerning these factors, but little is not known of the method to recover the BaTiO3 once vitrified, and of the effect of using such materials on the propertis of BaTiO3. This experiment was carried out to reveal the effect of such materials on the properties of the capacitor. In this experiment, the crushed and classified powder of BaTiO3 once vitrified were used as raw materials. The classified powder (100-150 mesh, 150-200 mesh, 200-270 mesh, 270-400 mesh, ) pressed 17.5mmφ. 1.2mm thick were fired at various temperatures. The dielectric constant, the dielectric loss, the change of lattice constant, the water absorption, the shrinkage and the curie point were respectively measured. The results obtaind are summarized as follows: 1. The dielectric constant, the dielectric loss and the shrinkage increased with increased temperature. 2. The water absorption dccreased with increased temperature. 3. The curie point was lowerd with increased temperature. 4. The lattice was expanded with increased temperature. 5. The effect on the bubbles of the classified particles growing large was equal to the rise of the firing temperature. 6. The porosity of the specimens calculated from the dimension and that calculated from the dielectric constant did not agree with each other.
In our previous paper, the flocculating effect of anionic polyelectrolyte on clay particles suspended in water was studied in relation to the mechanism of the formation of polyanion linkage among the clay particles. A new theory on the bridging mechanism has been proposed. The purpose of this paper is to provide satisfactory evidences for the theory. Aqueous suspension of clay (a mixture of quartz and pyrophillite) used in this work was treated with sodium polyacrylate, a typical polyanion, and one of the following reagents: sodium hydroxide, aluminium chloride, hydrochloric acid, or positively charged colloid of ferric hydroxide. For each suspension the pH value, the turbidity, and the amount of waterstable floc formed by the polymer linkage were determined. The experimental results on clay suspension with aluminium chloride showed that, in the range of pH 5.6-7, clay flocculation occurred through the interparticle bridging by polymer chains. The maximum amount of water-stable floc was obtained at pH of about 6.2 Above pH 7, the clay particles became deflocculated owing to the disappearance of the polymer linkage and the electrostatic repulsion among the particles. At the acid pH, below 5.5, polyanions could not participate in the bridging, because they were combined with free aluminium, resulting into a firmly coiled state inactive to the linkage. However, in the clay suspension treated with hydrochloric acid, it was found that the increase of acidity increased the formation of polymer linkage, unless the polymer was curled by the free aluminium produced by the dissociation of the clay lattice. In the case of the interparticle bridging, the polymer chain could be expected to be anchored by positively charged sites on the clay surface through chemical bond, maybe a co-ordinated sort. From the result on the clay suspension treated with colloidal ferric hydroxide, such positively charged sites were estimated to be the colloids of ferric-and/or aluminium-hydroxide fixed on the clay surface, as well as the lattice aluminium on the brocken edges of the clay. Further experiments were carried out concerning the order of addition of sodium polyacrylate and another reagent, aluminium chloride or colloidal ferric hydroxide. These results might also be interpreted by the above mentioned mechanism.
A new measuring method of shearing and normal stresses in a granular bed, and between a granular bed and a smooth, or rough plate has been herein developed, using a strain meter. The shearing strength obtained by this method is almost proportional to the normal stress, and the, kinds of friction factors, statical, maximum statical, and dynamical friction factor, are defiined by the use of the shearing diagrams from a granular bed test and a rough plate to the granular bed test. The ratio of dynamical friction factor of a rough plate to that of a smooth plate can be correlated to a modified Froude number (1-εp)U2/Dpg and the relative roughness S/Dp in an empirical equation.
The particles of pneumoconiosis minerals in dustpolluted air are below 5 microns in size of inorganic particulate matters. The pneumoconiosis mineral particles of about 0.5 micron in size seem to be particularly active in causing pneumoconiosis. The particles below 0.1 micron are too small to be retained in the lungs, and the particles below 5 micron in size can pass from the lungs to blood vessels and thence may reach the lymphatic system. Many important problems on pneumoconiosis are left unsolved yet. The study on the pneumoconiosis-mineralogical composition is therefore of vital importance in attempting to solve those problem. Investigations have been made in this line, and the results are summarized as follows: 1) The composition of pneumoconiosis minerals of below 5 micron is of kaolinite, montmorillonite, Biotite, plagioclase and quartz. 2) The compositition of the specimens below 2 micron is of kaolinite and montmorillonite. 3) The composition of the specimens below 0.5 micron is only of montmorillonite.
It is the aim of this paper to discuss the physical imports of the sieve analysis, with respect to the sedimentation methods. In view of the theory of sieving process by proposed Fagerholt, that the cut size of the sieved residue obtained in the time (t) can be determined as the average particle size of the fraction in a continued sieving process under the same condition from the time (t) to the time (3t), it is inferred from experimental results, that: 1. The effective opening of the sieve depends on the residue on that sieve, and it is represented in Eq. (9). 2. When the cumulative residue retained on each sieve are plotted against the effective opening line, for example Fig. 5, 6 and 7, the particle size distribution line is independent of the error of the opening of the sieve or any other sieving condition. 3. The particle size distribution obtained by sieve analysis is related to the diameter of equivalent spheres having the same volume of particles of the cut size. In the case of spherical particles, it is approximately equal to the opening of the sieve, and in the irregularly shaped particles, it is somewhat greater than the opening of the sieve, Eq. (11). 4. The particle size distributions obtained by the sedimentation methods, whether the particles are spherical or irregular, corresponds to the effective opening of the sieve for spherical particles.
There are various methods for grain size measurement. A new method is proposed in which the grain size can be obtained rapidly, simply and precisely by its direct measurement in the electron micrograph negatives. The grains are transparent on the photographic negative; therefore the larger the grains are the higher will be the rate of their mean transmittance, provided the grain number is kept constant. The mean grain size (a) expressed in the mean projection area is related to the mean transmittance T according to the formula where S represents the total area measured in the negative, n the number of the grains, Ta the transmittance of the grain part, Tb the transmittance of the back ground and m the magnification of the negative. A convenient apparatus has been made which will carry this principle into practice. Good agree-ments were obtained between the results hereby obtained and those by the conventional rule-method for both silver halide dispersions and model patterns
In chemical industries, the determination of particle size of fine powders play an important part in crushing fine particles its classifying and mixing, its transportation by air and other unit operations. The photo-extinction method is based upon the determination of the opacity of a suitable dis-persing liquid caused by the suspension of the powder in it. However, the lack of knowledge of the basic laws of transmission of light through the suspension leaves the method still open to question. For this reason first we studied the interrelations of optical density, the concentration of the powder, the length of light path through the suspension, the diameter of the particles and the density of the soild particles. The optical density of the suspension, which is the logarithm of the ratio of intensities of the incident and the transmitted light (I0/I) is proportional to the concentration of the powder (c) and the length of the light path (l) through the suspension, and inverse to the particle size (dx) and the density of the particles. (ρs). The relationship is expressed by the equation Secondly, we studied by this photo-extinction method the effects of the dispersion agent, the concentration of powder, the optical filter, the depth of the centre of the beam below the liquid surface, and viscosity, on the particle size distribution of kaolinite. We have found the photoextinction method to be adequate for the determination of particle size with considerable accuracy.
The sedimentation velocity of a particle is in proportion to the square of the partical size. Therefore, the particle size distribution can be determined from the changes of concentration with the depths of the suspension at the time selected according to the sample. In this instrument, the concentration gradient with depth is measured by means of specific gravity balance, and the cumu-lative curve of the particle size distribution is automatically recorded as the detection of the change of buoyancy with the square root of the depth that is in proportion to the particle size. The measurement is rapid, simple and reproducible. A few samples were measured, the results agreeing with those obtained by other methods. (Received Jun. 2, 1964)
The specific surface measured with Blaine air permeability apparatus, using Carman's equation, Eq. (3), decreases with the porosity of the powder bed as shown in Fig. 1. (3) In this paper, a method of determination of the specific surface not influenced by porosity adopted in the test is discussed for several sorts of cement and cement raw materials. The relation between porosity and the time required for air to pass through the powder bed is shown in Fig. 2, with conclusion that C and D in Eq. (6) are constants not influenced by the characteristics of powders. (6) Consequently, the specific surface not influenced by porosity adopted in the test is calculated from Eq. (7), though permeability can be tested at any porosity. (7) The graphical procedure of calculation is summarized in Fig. 3. (Received May 4, 1964)