Colloidal suspension of NiGa2O4 nanoparticles was synthesized by gel-sol method. Starting from an aqueous solution of Ni(NO3)2∙6H2O, Ga(NO3)3∙nH2O and a β-diketone ligand (acetylacetone), a precursory hydrogel was obtained through an epoxide-mediated alkalization. Then, a mild thermal treatment at 80 °C induces the deflocculation of the hydrogel, resulting in the formation of NiGa2O4 nanoparticles which is stably suspended in a solvent. The formation mechanism of the colloidal suspension was closely studied, revealing that chelation of acetylacetone to Ni cation with the formation of NiGa2O4 nanoparticles plays a key role to impart dispersion stability.
Zeolite is a microporous material that has various functions such as cation exchange capacity, adsorption ability, and so on. Zeolite is usually produced as a fine powder. A binder is generally used to prepare a bulky consolidated zeolite. In this conventional method, however, the content of zeolite is reduced, and the manufacturing process is complicated. Our research group has reported that Linde F zeolite can be directly synthesized as a binder-less consolidated body by using mechanochemical activated aluminum hydroxide as an Al source. Nevertheless, mechanochemical processing requires high costs and a lot of time. In the present study, the bulky consolidated Linde F zeolite was successfully synthesized by using no materials mechanochemically treated. Linde F zeolite was obtained at lower temperatures by increasing the amount of alkali addition. It was revealed that consolidated Linde F zeolite has the ability to remove cadmium ions. Furthermore, the foamed Linde F zeolite was produced by a hydrogen foaming reaction to improve the removability of heavy metal ions. It was also proved that the microstructure of consolidated zeolite was controlled by adding Al powder and zinc stearate. The foamed zeolite exhibited faster and better removability of cadmium ion than the unfoamed zeolite. Therefore, it was suggested that the synthesized Linde F zeolite could be applied to water purification materials.
In order to prevent the eutrophication phenomenon in closed waters such as lakes and inner bays, it is essential to establish a method for removing substances such as phosphorus and nitrogen which cause eutrophication. We have developed a crystallization type phosphorus remover on gypsum and CaCO3. In this study, the effects of the amount of calcium ion concentration in water and removal environment temperature at the time of removal on the phosphorus removal capacity were investigated. The phosphorus remover was obtained from a CaCO3-Ca(OH)2-gypsum composite by carbonating under CO2 gas pressure of 0.4 MPa after impregnation with a saturated aqueous solution of NaHCO3. When the amount of calcium concentration in water was large, the phosphorus removal rate was high in the initial stage of phosphorus removal, but the rate decreased with the passage of the removal time. In the initial stage of phosphorus removal, large amount of calcium ions increased the degree of supersaturation of calcium phosphate, and therefore nucleation and crystal growth of calcium phosphate on the surface of calcium carbonate was probably promoted, resulting in the increase in phosphorus removal rate. However, the phosphorus removal rate would decrease with the passage of the removal time due to the rapid decreased in the phosphate ion concentration in the initial stage. As removal environment temperature increased, the phosphorus removal rate increased in the initial stage of phosphorus removal, but the rate decreased as the phosphorus removal progressed, and consequently the lower the removal environment temperature, the higher the removal rate. When the temperature is high, the amount of dissolved calcium was large, and as a result, the phosphorus removal rate would increase in the initial stage of removal. However, the rapid consumption of phosphate ions in the initial stage would lead to the decrease in the removal rate with the progress of phosphorus removal.
The effect of the surface microstructure on the organic matter removal ability of the microorganism-supported alumina sintered body was investigated. Porous alumina body having various pore sizes and pore volumes were prepared by changing the amount of pore-forming agents having different particle sizes. Furthermore, the effect of the firing temperature on the microstructure of alumina sintered body, was investigated. The microorganisms were supported on the sintered alumina body by immersing the sintered alumina body in a culture solution containing yeast, lactic acid bacteria, and natto bacteria for 5 days. Regarding the organic matter removal ability of the microorganism-supported sintered alumina body, the change in the COD decreasing ratio after immersion in model sewage which was prepared with glycine and glucose having an initial COD value of 180 ppm, for a predetermined time, was examined. The COD decreasing ratio was less affected by the pore size of the sintered alumina body, but, increased as the pore volume increased. When the firing temperature is low, due to poor densification of alumina, a lot of voids are formed between the alumina particles, resulting in surface undulations that is advantageous for the adhesion of microorganisms. As a result, the organic matter removal ability of the sintered alumina body fired at a low temperature tends to be higher than that of the sintered alumina body fired at a higher temperature. In order to improve the organic matter removal ability of the sintered body in which the pore-forming agent is added only to the upper surface of the sample, the porous layer formed by the pores formed by the pore-forming agent needs to have a thickness of above 0.01 cm.
Alumina-magnesia castable refractory is used for the inner wall of molten steel ladle. The main cause of damage to this refractory is thermal shock caused by a sudden temperature change when putting in and out molten steel. Therefore, there is a thermal shock damage resistance coefficient R'''' as a parameter that represents the resistance of refractory materials to thermal shock, and the evaluation of effective fracture energy is important for improving R''''. The purpose of this study is to evaluate the effect of ZnO addition on the effective fracture energy of alumina-magnesia castable refractories. ZnO is reported to improve the mechanical properties of spinel (MgAl2O4). Samples containing 0 to 3 mass% ZnO were prepared, and the effective fracture energy, crystalline phase, microstructure, and apparent porosity were evaluated. The effective fracture energy increased with the increase of the amount of ZnO added. The apparent porosity shows a constant value regardless of the amount of ZnO added, and the promotion of spinel sintering and the increase of spinel amount by the solid solution of zinc oxide contributed to the improvement of the effective fracture energy.
Damage behavior of spread carbon fiber (SCF)/epoxy (EP) laminates containing microcapsules for self-healing was investigated experimentally. The SCF/EP laminates with the microcapsules containing a healing agent mixed with a UV fluorescent dye were fabricated. The apparent interlaminar shear strength and the healing efficiency of the laminates were evaluated by short beam shear tests. Damage areas of tested specimens were observed under UV light to investigate the relation between the damage behavior and the strength recovery of the laminates. Results showed that the cracks propagating through microcapsules could be visually observed under UV light because the healing agent containing the UV fluorescent dye flowed out from broken microcapsules into cracks. It can be considered that the damage behavior of the laminates affected the apparent interlaminar shear strength and the healing efficiency.
The purpose of this study is to estimate the acceptable defect size αmax after needle peening (NP) and laser peening (LP) for a high tensile steel welded joint containing a surface defect on a weld toe. The magnitude of the relationship between the positive value of the stress intensity factor range ΔKT and the threshold stress intensity factor range ΔKth was compared to determine whether the semi-circular crack propagated or not. The value of ΔKT was evaluated from the applied stress distribution and residual stress distribution using the finite element analysis method. The value of ΔKth was evaluated considering a local stress ratio in addition to a crack size. The estimation results of αmax of post NP and LP treatment were both consistent with experimental results. The new estimation method could provide safer αmax than that of former method.
Push-pull fatigue tests of rolled magnesium alloys AZ31 and AZX912 were performed with a side-notch plate specimen to examine the effect of a single overload on the crack growth behavior under a stress ratio of -1. The behavior in retardation of crack growth was unclear in the case of AZ31 because the crack growth rate was relatively higher at the overload point. However, this was observed clearly, when the branching of the crack tip happened in the case of AZX912. The geometry of the fracture surface and the changes in crack growth path were related to the crack growth behavior. The crack opening level became higher when the crack growth rate was lower. Therefore, the crack closure is related to the retardation of the crack growth rate. When the branching of a crack tip occurred, not only the residual compression stress at crack front but also the variation of local crack growth direction after overload affected the fatigue crack growth behavior.
Surgery, radiation therapy, and chemical therapy have been reported as main treatments for cancer that is one of the worst diseases reported. However, because of high invasiveness on patients, cancer hyperthermia has been studied as non-invasive treatment. Hyperthermia uses a difference of thermal tolerance between normal and cancer cells and gives an affected part thermal stimulation to kill cancer cells selectively. For developing effective conditions of hyperthermia, in vitro study to evaluate the thermal tolerance have been required. However, since existing cell culture vessels cannot control the culture temperature, genuine thermal tolerance of cells cannot be investigated appropriately. To reveal critical temperature proper for hyperthermia, we developed a culture device controlling culture temperature. With the developed device, culture temperature was regulated far more quickly than conventional method with existing vessels, which enable us to study the thermal tolerance of cells appropriately. For the control of culture temperature, the device has a titanium culture substrate where a peltier element adhered. Since a biocompatibility of the device was confirmed, a difference of thermal tolerance between normal and cancer cells was, then, investigated with the developed device by using Normal Human Dermal Fibroblasts and Michigan Cancer Foundation-7 as model cell species. As a result, it was confirmed that cancer cells were more sensitive to thermal stimulation than normal cells, which was qualitatively consistent with previous researches. Thus, we conclude our developed device can be used for investigation of thermal tolerance of each cell specie, which will contribute for the development of cancer hyperthermia.