The CdS precipitates were prepared from aqueous solutions of cadmium chloride, bromide, nitrate, sulphate or acetate, and the relation between crystal structure and photoconductivity of these CdS precipitates was investigated. All CdS precipitates were found to be a mixture of hexagonal and cubic phases, and their mean particle sizes were about 1.5 to 4μm. All precipitates were found by chemical analysis to be slightly sulphur-rich. Using an interdigital electrode, the spectral response of photoconductivity and the rise and decay of photocurrent were measured. All specimens showed photoconductive response in the visible wavelength region, but the peak wavelength scattered in the wavelength region of 550∼570 nm from one specimen to another. The rise or decay time was very long for the specimens prepared from cadmium chloride and bromide. The specimen prepared from cadmium sulphate had the highest photoconductive sensitivity, while the one from cadmium bromide had the lowest sensitivity.
An experimental study on the liquid phase adsorption of crystal violet on the virgin surfaces of Soma-sand and Pyrex-glass particles produced by grinding with a mechanical mortar was carried out to investigate the adsorption properties of newly produced solid surface. In the experiment, the following two methods were employed. (1) Wet (C.V.): crystal violet is adsorbed during grinding in the solution. (2) Dry (C.V.): crystal violet is adsorbed immediately after grinding in air. The experimental results revealed the similar trend in the adsorption properties between the present system and the Soma-sand-methylene blue system reported previously by the authors. From both experimental results, it was confirmed that the adsorption on a virgin surface produced at the instant of the fracture has to be distinguished from the adsorption on an original surface of the particles before fracture.
In this paper proposed is a method of estimating the coefficient of earth pressure at rest in the granular or powder material which is supposed to lie in the state of elastic equiliblium. On the basis of an assumption that a relation equivalent to the Hvorslev's equation for the shear strength of saturated clays will come into existence not only in the state of plastic equiliblium but also in the one of elastic consolidation equiliblium, a theoretical equation was obtained by considering the equiliblium of stresses on a special plane, so called the mobilized plane, in the element of material. This proposed equation is characterized by the fact that we can consider the influence of stress history of material. The following conclusions were derived from the several calculation results of the proposed equation. (1) As the effective internal friction angle mobilized at the consolidation equiliblium state approaches at the value of plastic failure state, so the K0-value becomes smaller. (2) The larger the mobilized cohesive component during the consolidation equiliblium state is, the smaller the K0-value at the same value of effective friction angle inclines to become. (3) The K0-value of over-consolidated material in the active state increases a little with increasing over-consolidation ratio.
Constructing a packed bed of polystyrene beads in a test die, the axial compaction stress (σ1) and radial stress to a die wall (σ2) were measured over compaction procedure. After the piston was fixed on the way to compact, the stress relaxations of σ1 and σ2 were also investigated. These two kinds of experiments were performed under a loosely packed bed (experiment 1) and a pre-compacted closely packed bed (experiment 2). The measured temperature range was 25°C (beads behaved as an elastic body) to 95°C (beads behaved as a viscoelastic body). In the experiment 1, at low temperature, a small amount of stress relaxation was observed due to rearranging mechanisms of powder, because polystyrene beads behaved as an elastic body. However, at high temperature where a viscoelastic behavior was predominated enough, a conspicuous stress relaxation was observed. When the temperature was higher and the compaction speed was slower, the radial stress (σ2) was observed to be greater, which is recognized as the result of viscoelastic deformation of plastic beads. In the experiment 2, on the other hand, when the pre-compacted closely packed beds was investigated, higher ralaxation modulus was observed. In this case also, the decrease of axial stress (σ1) was observed during the relaxation period; however, the decreasing tendency of the radial stress (σ2) was not so remarkable in this case. At high temperature, the increase of the radial stress was observed due to the rearrangement accompanied viscoelastic deformation of contact parts of particles. However, after increasing period, σ2 decreased gradually and approached σ1.
The kinetics of the spherical agglomeration of the binary mixture composed of sand (76, 89 or 106μ) and calcium carbonate (3.8μ) in liquid suspension was investigated. By introducing some fine particles to a coarse particles system the agglomerate was compacted more closely during agglomeration than coarse particles alone. The compacting process of the agglomerate during agglomeration was expressed by the modified Kawakita's equation (2), relating the porosity of the agglomerate to the total agitation energy put into the suspension. The agglomeration rate increased with increasing the concentration of fine particles in the mixture until reaching to a critical value at which the agglomeration rate was maximum. An introduction of over-dose of fine particles into the system reduced the agglomeration rate or brought about the rapid secondary agglomeration which followed the ordinary slower agglomeration after a long induction period. The rate constant of agglomeration was maximum at the composition of the mixture corresponding to the closest binary packing in which fine particles just fill the interstices between coarse particles and to the case where fine particles just cover the surface of coarse particles. From the above results and the agreement of the agglomerate growth data with the coalescence model by Kapur, it was concluded that the ordinal slower agglomeration and the rapid secondary agglomeration may be controlled by preferential coalescence between fine and coarse particles and random coalescence, respectively.
Sulfisomidine was agglomerated or encapsulated by spray-drying its aqueous slurry or ammonium solution containing various kinds of binder i. e. acacia, gelatin, carboxymethylcellulose, methylcellulose or polyvinylpyrrolidone. The spray-dried products prepared from the aqueous slurries were encapsulated, acquiring a smooth film. On the other hand the products from the ammonium solution were characterized by forming a porous agglomerating crust due to the drastic evaporation of ammonia from spray droplet and changing the crystalline form to the amorphous or disordered form which resulted in increasing the solubility. The dissolution rates of the disks of spray-dried particles were grouped into two cases, one with the increased rate and the other with the reduced, as compared with that of the untreated original particles. This dissolution behavior depended on the type of feeding liquid, whether aqueous slurry or ammonium solution, binder and solvent used. Irrespective of the kind of binder and solvent, the product from the ammonium solution showed a prolonged release behavior. The action of delaying the dissolution rate of methylcellulose and carboxymethylcellulose product was strongest among the spray-dried products. The rate process of the increased and the reduced dissolution was analyzed by“capillary dissolution”and diffusional“three film”model, respectively.
The affinity of clay minerals for water has been investigated by determining their heat of immersion. Clay samples chosen are unground or ground kaolinite and dickite from the two layered-minerals, and ground pyrophyllite and talc from the three layered-minerals. The two layered-minerals showed higher heat of immersion values than the three layered-minerals, which probably results from the higher negative charge densities and the exposed OH ions in the structure of the former. Ground dickite, dry-ground one in particular, exhibited a markedly higher heat of immersion value than unground samples, suggesting that the newly produced edge surfaces have the highest affinity for water. Preadsorption of water reduced steeply the surface energies of Na-dickite and Na-pyrophyllite toward the surface energy of free water where nearly two molecular adsorption had been completed.
Silica gels were treated with optically active tartaric acid esters, i. e., L(+)tartaric acid dimethyl, diethyl and di-n-butyl esters. The numbers of surface group were estimated as 2∼3×1014cm-2 from the microanalysis and the argon surface areas of the surface-treated silica gels. The characteristic absorptions due to their surface groups were observed in their ir absorption spectra. These surface groups were easily hydrolysed and the aqueous solutions after hydrolysis of their surface-treated silica gels showed the same optically active and the same specific rotation as the ones of the tartaric acid esters used. From these results, the surface groups were confirmed to be composed of the tartaric acid esters used and they were also optically active. The reaction was also confirmed to proceed with the silyl fission as shown in the following scheme: _??_Si_??_OH+HC-ROCOCHOH H_??_OCOOR→_??_SiOC-CHOHCOOR COORH+H2O The surface-treated silica gels were dispersed into water. But these gels, except the silica gels treated with dimethyl tartarate, were flocculated and transferred into the interfacial region between the immiscible two liquids like n-hexane and water. The surface tensions of the surface-treated silica gels, γS, were estimated as γS>183erg/cm2 for the ones treated with dimethyl tartarate and 72.8>γS>80.9erg/cm2 for the other two kinds of silica gels.
The binary gel pellets were prepared in order to make clear the pore structure of silica-magnesia gel and the mechanism of the formation of solid acids or bases through a mixing process. Silica and magnesia hydrogels were mixed in their suspension, drained, molded in a cylindrical vessel of 5mmφ and 5mm height, dried at room temperature and calcined at 500°C for 2 to 3hrs. The pore volume distributions, surface areas and the amount of acids or bases were measured by the mercury penetration method, nitrogen adsorption method and titration method, respectively. The followings were recognized: (1) Macropore volume increased with increasing MgO content. (2) Specific surface area decreased linearly with increasing MgO content. (3) Formation of acid point or disappearance of base point seems to take place at the contact place of both gel particles. (4) In the mixing process, both SiO2 and MgO particles behaved as agglomerates, the former being the agglomerate with transitional structure between cubic and orthorhombic packings, the latter the one of petal-like thin film.
A method is described for preparing silica-alumina catalyst pellets having a controlled and enlarged pore volume and an improved effective diffusion coefficient by the addition of a powder diffusion promoter. Sieved silica-alumina xerogel powder as the promoter was mixed into the same mother hydrogel, and calcined at 500°C for 2 to 3hrs. The pore structure and effective diffusion coefficient of the sample pellet were measured by a mercury porosimeter, N2-adsorption, scanning electron microscope and diffusion cell. The results obtained were as follows: (1) Addition of the promoter caused increase of macropores. (2) Formation of macropores was due to the difference in drying shrinkage between the hydrogel and the xerogel promoter. (3) Effective diffusion coefficient was remarkably improved by the formation of macropores.
To examine the error in measuring particle concentration due to anisokinetic sampling over a wide range of inertia parameters, theoretical and experimental studies have been conducted by using methyleneblue-uranine aerosol generated by a spinning disk and lycopodium spores in the small and large inertia regions, respectively. The theoretical results obtained assuming potential flow agree well with the experimental values in the small inertia region. On the other hand, the experimental result is smaller than the theoretical one in the large inertia region. It is also recognized that the concentration error becomes smaller as the sampling velocity becomes extremely high. The amount of particles deposited in a probe is also examined to show that this amount cannot be ignored in practical applications.
There are few reports published on the state of pore distribution in tablets. Using a tablet machine and a compression testing instrument, the relation between the ejecting conditions and the pore distribution of tablets has been investigated and the following conclusion was obtained. The total volume of pores having 103∼104Å radius in the center of tablets was greater than that in the edge of tablets. Furthermore the similar phenomenon was observed when the powder was slowly compacted and then subjected to tensile stress. As for the tablets with less capping tendency, the total volume of pores in the center of tablets was comparatively reduced when the tablets were ejected with the suitable compressing force retained. Consequently, the effect of applied force was considered to give sufficient relaxation of stress, such as tensile stress, to the tablet during ejection.
To investigate ball mill grinding from the kinetic point of view, the effect of hardness of samples and feed weight on grinding rate constants has been studied. The samples used were silica glass, borosilicate glass, soda glass, quartz, feldspar, limestone, marble, gypsum and talc. The pebble mill consisted of a 12.8cm-diameter by 13.2cm-long cylinder and the grinding medium was 40 balls, each of which had a diameter of 3cm and their total weight was 1180g. The tests were done at the speed of 88.1% of critical one. The size analysis was done by 21/2 series of Tyler standard sieves in Rotap machine. The experiments were performed on -14+20 mesh feed size to obtain the grinding rate constants. In the previous paper, we had derived the following equation. K1=0.85HV-0.23·W1-1.5 (I) where K1 is the first order decreasing rate constant of feed size, HV dimensionless Vickers hardness and W1 dimensionless feed weight. On the basis of this concept, further investigation was made on the rate constant of under size increasing Kx of zero order kinetics, and the following results were obtained. (1) The correlation of particle size ratio x/x0, dimensionless feed weight W0, HV and Kx can be shown by Eq. (II). Kx=0.95x/x0·HV-0.47·W0-1.5 (II) (2) To obtain Kx from K1, the Eq. (III) can be used. Kx=1.1x/x0HV-0.24·(W0/W1)-1.5·K1 (III)
Mechanical degradation of polystyrene (PS) has been studied kinetically by a ball mill with various sizes of balls at a constant velocity of revolution (60rpm) and packing ratio (30%) at room temperature. The sizes of steel balls used were 91, 51, 31, and 26mm in diameter. The degree of degradation was determined by measuring the number-average chain length at various stages of mechanical degradation. The extent of degradation was represented by the rate constant of degradation and the final average chain length. The order of effective size of balls for the degradation of PS was 51>31>26>95mm. The mechanical degradation of polycarbonate (PC) was also carried out at the same conditions. The order of effective size of balls for the degradation of PC is 95>51≥31≥26mm. In order to know the interaction between PS and PC during the mechanical degradation in a ball mill, the mixtures of PS and PC with various mixing ratios were also ground with balls of 95 mm in size. The rate of degradation of PS was increased in the presence of PC, while that of PC was decreased. These results are used to discuss the grinding behaviors of polymer in a ball mill.
In order to investigate the effect of particle-permeation on the segregation of solid mixture in a rotating vessel, radial and axial segregations of spherical binary solid mixture were observed by using a horizontal rotating cylinder and a horizontal rotating conical vessel. The binary mixture used was made by combining glass beads, spherical alumina particles and spherical silica-gel particles having various sizes and densities. As a result, it was obtained that radial and axial segregations of binary solid mixture in a rotating vessel were closely related to the permeation effect (xT/xB) measured in a moving bed. On the basis of the permeation effect (xT/xB), it was tried to estimate the segregation pattern, degree and direction of the mixture cascading in a vessel rotated at lower speed of rotation.