Superconductive oxide fine powders were prepared by spray pyrolysis using an ultrasonic atomizer. The as-prepared particles had spherical shape in submicron order with narrow size distribution. Fluorescence X-ray analysis and EDS analysis showed that the powder composition was in good agreement with the starting solution composition. Experimental factors (concentration, pyrolysis temperature and flow rate) influenced the powder characteristics such as particle size and crystal structure. The particle size distribution and particle morphology were independent of the experimental factors. Tc of YBa2Cu3O7-x ceramics was 92K, while those of Bi2Sr2CaCu2Ox and Bi2Sr2Ca2Cu3Ox ceramics were 86K and 110K, respectively. The addition of PbO modified the superconducting properties, and Tc of the ceramics was higher than that without PbO. Tc of PbO doped Bi2Sr2Ca2Cu3Ox ceramics was appreciably dependent on the sintering conditions.
A demand for fine or ultrafine particles is increasing in many industries. It is well known that the energy efficiency in a grinding process decreases with a decrease in produced particle size and with an increase in grinding time or input energy. Therefore, the evaluation of fine or ultrafine grinding of materials is essential. In this paper, ball mill grinding was carried out on silica-glass to get submicron particles and to evaluate the fine or ultrafine grinding process. The mill used was made of alumina with a diameter of 144mm and the inner length of 130mm. Its volume was about 2.1 liters. The grinding balls were also alumina with a diameter of 20mm. The effects of the mass of feed and the mass of balls on fine grinding were investigated at a constant rotatioal speed of the mill. The progress of grinding was evaluated by the mass of submicron particles and the surface area of ground porducts. The following results were obtained: (1) The final median particle size of ground products was independent of the mass of feed or balls. (2) The optimum grinding condition for production of submicron particles changed with grinding time in an early stage and it became constant in the later stage. (3) The surface area was proportional to the mass of submicron particles in the ground products.
Contamination content in ground powder from grinding media was examined using a media agitating wet mill. The effect of grinding condition was investigated on the contamination content and specific surface area of ground powders. Four sample powders were used; the two were CaCO3 and SiO2 which have lower Vickers hardness than grinding media i.e., ZrO2. The other two were Al2O3 and SiC which have higher Vickers hardness than zirconia. The followings are the results obtained. (1) The specific surface area of ground powders and the zirconia contamination content increased with increasing impeller velocity and with decreasing sample weight in the mill. At high impeller velocity and in low sample weight, the XRD profiles of ground Al2O3 contaminated with zirconia revealed the broad peaks for zirconia. (2) The contamination content significantly depended on the Vickers hardness of the sample powders. When the Vickers hardness of the sample powder was higher than that of the grinding media, the contamination content in the ground powder became very high. On the contrary, the contamination content in the ground powder with lower Vickers hardness was less than 1.0wt.%. (3) The ratio of dipole moment to molecular volume of grinding solvent, μ/V influenced the contamination content and the specific surface area in the ground powder. The specific surface area increased, but the contamination content did not alway increase with an increase in μ/V.
A semiconductive fine powder was prepared by mechano-chemical reaction with dry ball-milling of a powder mixture of SnO2 and Sb2O3. From the microstructural point of view, discussions were made on the effects of the following factors of (A) and (B) on the electrical conductivity of glass composites containing the ball-milled semiconductive powder; i.e., (A) ball-milling duration, and (B) firing temperature of powder compact. The results obtained were summarized as follows: (1) The electrical conductivity of the ball-milled powder mixture significantly increased with increasing ball-milling time. However, it was pointed out that the reaggregation of finer particles during milling induced a detrimental state to the homogenization of particle dispersion which determines the electrical conduction structure in the glass matrix. (2) It was found that firing at higher temperature was effective to increase the homogeneous dispersion of semiconductive SnO2 particles in the glass matrix, resulting in an increase in electrical conductivity of the glass composite.
The study was made on the adsorption of oxygen and nitrogen on natural zeolite (Itaya zeolite) products calcined at 500-700°C. The adsorption measurement was carried out at 5-25°C and under the pressure of 0-5atm. Natural zeolite calcined at 500°C adsorbed more nitrogen than oxygen. Oxygen enriched air (oxygen about 53 volume %) was obtained when natural zeolite was used in the PSA (pressure swing adsorption) process. Natural zeolite is useful to obtain oxygen less than 50 volume % in product gas. Natural zeolite needs to be improved for the supply of oxygen more than 50 volume % in product gas.
This study is concerned with the mechanical behavior of Japanese lacquer film coated on a steel ball in process of moisture absorption. Normal stress generated at the interface between film and steel ball was obtained as a function of time by simulation, when the film was exposed to atmosphere at given relative humidities. The normal stress at the interface increased with relative humidity, and steeply at humidity above 60 %RH. The stress at 100 %RH reached three times as much as that at 60 %RH. Furthermore, the stress increased with the film thickness and with the decrease of radius of steel ball.
This paper deals with the strength of nickel-foam reinforced aluminum Alloy (NFRA) and clarifies the influence of the thickness of intermetallic compound layer of NFRA. NFRA has two kinds of intermetallic compound layer between nickel-foam and base metal formed by artificial aging. In order to vary the thickness of intermetallic compound layer, three different heat treatment conditions were performed on three types of NFRA with different size of Ni skeletons and on AC8A aluminum alloy. Fatigue tests and tensile tests were carried out on NFRA and AC8A aluminum alloy. The fatigue life and tensile strength of NFRA decreased significantly as compared with those of AC8A. The thickness of intermetallic compound layer affects both the fatigue strength and tensile strength, since the intermetallic compound layer changes the bonding strength of the interface between nickel-foam and base metal.
It is desirable to design a structure and its members with a reasonable reliability. In the JSCE Code, it is defined that the designed strength of a RC-short column supported laterally at both ends under an axial load at a given eccentricity may be obtained by a simple method of neglecting an effect of lateral deformation of the member when the slenderness ratio is less than 35, using the reduction factor of 1/1.15. Here, a method to obtain a reduction factor for the strength of a double reinforced concrete member with a required reliability is proposed by using the probabilistic method of estimating the reliability, considering the variations in strength of both reinforcing bars and concrete, and taking account of an effect of lateral deformation. And, this study points out that in order to obtain a required reliability when applying this method to the combination of these two materials used in general, either the reduction factor of 1/1.15, prescribed in the JSCE Code, should be reduced appreciably, or the upper limit of the slenderness ratio, set at 35, of the member should be lowered by a large margin when employing the reduction factor 1/1.15 in the whole range of eccentricity.
The present paper describes a study on the effect of compressive strain holding on the high-temperature strength of Modified 9Cr-1Mo steel, a candidate steel for steam generator in a Japanese demonstrative fast breeder reactor, FBR. As usually known, the high-temperature fatigue strength of the Modified 9Cr-1Mo steel was significantly reduced by compressive strain holding. According to our observation by a scanning electron microscope, SEM, on the main-crack surface of the specimens failed under compressive strain holding, striations were clearly observed under compressive strain holding in air and tearing dimples in vacuum. It was guessed that compressive strain holding conditions gave a greater energy measure of fatigue damage to the specimens compared with no-holding conditions and this resulted in the reduction of the high temperature fatigue strength under compressive strain holding conditions.
In order to investigate the crack growth characteristics by thermal striping in sodium coolant used for FBR, the thermal striping tests in sodium have been conducted by using Type 304 stainless steel and its carburized material. The stress intensity factor, derived from the thermal stress analysis for the condition of plane stress, was effective for the estimation of the final crack length. It was found that the number of cycles, at which the cracks were produced in the carburized material, was smaller than that in the base metal. The final cracks in the carburized material were longer than those of the base metal. The loading condition of the termal striping was controlled by thermal strain, and the damage by thermal striping in a brittle material such as the carburized material was greater than the base metal. The range of stress intensity factor of the carburized material was increased by the change of property.
Fatigue crack propagation behaviour has been investigated on a Ti-6Al-4V alloy in 3%NaCl solution. Experiments were conducted on three different microstructures which were prepared with annealing at 705°C (AN705) and 850°C (AN850) and solution-treatment and aging (STA), and on two orientations. In T-L orientation for AN705 and AN850 and both orientations for STA, an abrupt increase in crack propagation rate took place at a certain ΔK value, ΔKscc, which was strongly related to SCC under cyclic loading. Fractographic examination revealed that the fracture surfaces consisted of extensive cleavage when ΔK>ΔKscc. A considerable anisotropy in crack propagation behaviour was observed for the annealed microstructures. Their crack paths in L-T orientation were suddenly changed toward the rolling direction, suggesting the strong sensitivity to corrosion fatigue crack propagation in T-L orientation. The pole figures showed that the annealed microstructures had a transverse texture in which (0002)-planes were parallel to the rolling direction. This indicates that the largest susceptibility to aqueous NaCl is found for loads acting perpendicular to these planes, since cleavage type fracture is known to be often observed on or near (0002)-planes.
In order to investigate the effects of various solutions on soda-lime-silica glass during cutting and after indentation, the observation of crack growth has been performed. Flaking length and micro-hair crack length were determined in 11 media including oil, alcohol, water and air by means of scoring and micro Vickers' method, respectively. It was suggested that the values of the maximum flaking length and the growth of micro-hair crack are related with the dielectric constant of media employed in this study.
By assuming that the time-to failure Tf in static fatigue tests of ceramics is controlled by the subcritical crack growth in Region I of trimodal KI-a curve, where loga∝nlogKI holds (a; the crack velocity, KI; the stress intensity factor and n: a constant), Evans formulated a simple but quite convenient formula for static data analysis (σanTf=constant). However, because not only oxide-ceramics show the trimodal curve but also logKI-loga relations are not always linear in non-oxide ceramics, the formula necessarily has some limitations in its applications. In the present paper, the applied load Po-Tf relations are formulated for bi-linear or tri-linear relation between logKI and loga, and the Po-Tf relation is numerically simulated for the trimodal curve. The simulation shows that a gap between Region I and Region III still appears in the logPo-logTf diagram, although the gap gets a little gentle. It is also cleared through the formulation that static fatigue data for various specimen geometries, sizes and initial crack length can be analyzed quite well by using a newly introduced “normalized time of failure”, (Tf)N=[Tf/(W/a*)]/∫1x0[√x0F(x0)/√xF(x)]ndx, where x0; the initial crack length, F(x); the geometry factor of the specimen and W; the specimen width.
In order to predict the fatigue life of machine equipment, the fatigue crack propagation law is usually investigated by using smooth specimens. However, few investigations of the crack propagation have been carried out on the specimens having the cross-section of complicated shape. In this study, the specimen with three grooves which were cut in the loading direction was used to clarify the crack propagation and the crack closure behavior at the suddenly changed site of the thickness. The crack propagation rate was observed to be once accelerated and then decelerated in the vicinity of the first groove. The variation of crack closure point was different between the grooved specimen and the smooth specimen. The stress intensity factor was evaluated using the calibration curve between the crack propagation rate and the effective stress intensity factor range obtained by the smooth specimen. The results showed that the stress intensity factor of the grooved specimen was higher in front of the first groove and lower behind it, compared to the smooth specimen. The crack propagation law evaluated with Kmax becomes complicated in the vicinity of the first groove due to the change of thickness. Thus, the crack propagation rate once increases and then decreases with the maximum value of stress intensity factor Kmax when the crack crosses the groove.
Heterojunction photovoltaic cells were fabricated with composite materials of TiO2 encapsulated in polymetylmethacrylate and p-type silicon (C-PMMA-TiO2/p-Si), and with TiO2 and p-Si (TiO2/p-Si), respectively, and their electrical and photovoltaic characteristics were investigated. As a result, the dark current vs. voltage characteristics indicated good rectification for the both cells. The rectification ratios were about 11 and 34 at 0.4V for TiO2/p-Si and C-PMMA-TiO2/p-Si heterojunction photovoltaic cells, respectively. However, the open-circuit voltage and the short-circuit current density of TiO2/p-Si heterojunction photovoltaic cell under light irradiation were extremely smaller than those of C-PMMA-TiO2/p-Si heterojunction photovoltaic cell. Under the light irradiation of wavelength 525nm with the intensity of 80μW/cm2, the photovoltaic properties of C-PMMA-TiO2/p-Si heterojunction photovoltaic cell were as follows: the open-circuit voltage Voc is 0.25V, the shortcircuit current density Jsc is 3.0μA/cm2, the fill factor F.F is 0.59 and the power conversion efficiency is 1.3%. Furthermore, the dark current vs. voltage and capacitance vs. voltage characteristics on C-PMMA-TiO2/p-Si heterojunction photovoltaic cell were studied, and the transport mechanisms were discussed.