ZnO is widely used as a raw material of various electronic parts and cosmetics. The properties of ZnO particles depend on the morphologies of the crystals. So, it is important to control the morphology of ZnO particles to obtain desired properties. Layered zinc hydroxides are known as the precursor of ZnO because it can be easily synthesized and transformed to ZnO by aging in aqueous solution at relatively low temperature. Moreover, ZnO particles derived from the layered zinc hydroxides by aging in aqueous solutions show various forms which in difficult to obtain by the direct thermal decomposition of zinc hydroxides at a high temperature. In this report, ZnO was synthesized from a layered zinc hydroxide containing nitrate ions between layers, Zn5(OH)8(NO3)2 •2H2O (ZHN), as a precursor by aging under various conditions. Effects of the amount of deionized water, the concentrations of NaNO3 aqueous solutions and the temperature were investigated on the transition of ZHN to ZnO during aging. The formation ratio of ZnO increased with increasing the amount of deionized water and aging temperature. When the ZHN was aged in 200 mL deionized water, the formation ratio of ZnO was 70% even at 60°C and increased to 95% at 90°C and 120°C. The aging in NaNO3 aqueous solutions enhanced the formation of ZnO but the formation ratio largely decreased by aging in a 0.1 mol/L NaNO3 aqueous solution. When aging was carried out in NaNO3 aqueous solutions of 1×10-2 to 1×10-6 mol/L at 90°C and 120°C, the ZnO formation ratio was almost above 95%. In the case of high formation ratio of ZnO, well crystalized rod-shaped particles, which is characteristic shape of ZnO, was obtained and the aspect ratios of ZnO particles decreased with increasing NaNO3 concentrations.
Self-sustaining Ce0.9Gd0.1O1.95 film was fabricated by aqueous tape casting method. An aqueous tape casting of dispersion was performed using poly acrylic acid (PAA) as dispersant, poly carboxylate ammonium (PCA) as binder, poly ethylene glycol (PEG) as plasticize, and deionized water as solvent. The rheology of the slurries was evaluated with cone-plate method. The conditions for preparing stable slurries were studied, regarding with solid concentration and ball-milling period, and optimized by viscosity measurements and aging experiments. Green tapes with thickness in the range of 65 to 130 µm were prepared by conditions; solid concentration of 25～26 vol% and gap width of 0.2～0.3mm with moving rate of 45 cm min-1. Conventional sintering techniques were available for densification, and semitransparent Ce0.9Gd0.1O1.95 film was successfully fabricated by heating a green sheet at 1500 °C in air.
Recently, carbon-containing silica has attracted much attention due to its white photoluminescence property under UV light irradiation at room temperature. We have previously reported that microporous silica was successfully synthesized by using collagen as a template. In the removal process of collagen used as a template by calcination at high temperature, we confirmed that carbon-containing microporous silica could be synthesized by controlling calcination temperature and time. In the present study, carbon-containing microporous silica with various carbon contents were synthesized by calcination of collagen / silica composite and their white photoluminescence property was investigated. The carbon-containing microporous silica exhibited broad fluorescence spectra in the visible light region by excitation of UV light. As the carbon content decreases, the white photoluminescence property of the samples became higher, and when the carbon content was about 0.1 wt%, the sample showed the highest performance, while silica without carbon did not show the white photoluminescence property. This result suggested that carbon present into micropore of porous silica is an important role for the white photoluminescence property. It was also suggested from various spectroscopic measurements that small carbon clusters were presented in the micropore of porous silica.
We previously reported that water purification materials with high phosphorus removal capacity made from PVB-coated gypsum board. In this study, we tried to prepare the material removes phosphorus and organic substances with silica-coated gypsum boards. Test pieces cut out from commercial gypsum board was coated by immersing in silica sol and drying in the air at 50°C. Microorganisms were supported on the silica-coated samples by immersing in a culture solution containing lactobacillus, bacillus natto and saccharomyces. For gypsum board silica coated two or three times the surface did not collapse after long-term removal phosphorus. From the results of SEM observation, precipitation of calcium carbonate and adhesion of microorganisms were confirmed on the surface of the silica-coated samples. The silica-coated sample immersing in a culture solution was able to remove organic substances. However, the phosphorus removal performance decreased. In the sample immersed in a culture solution, although calcium ion dissolved enough, the amount of calcium carbonate decreased. From this result, it was found that the amount of calcium carbonate greatly contributes to the phosphorus removing ability in this study. Therefore, high phosphorus removal performance was obtained by the sample carbonated by 0.5 mol/L sodium carbonate aqueous solution. In addition, the phosphorus removal ratio in the sample immersed in a culture solution was lower on 5 days than on 3 days. This result is because calcium phosphate was dissolved in lactic acid produced by lactobacillus.
Alumina-magnesia monolithic refractories are mainly used to line the inner wall of steel ladles. The refractories are damaged by the thermal shock while using on its wall and the spalling of them occurs. Therefore, it is very important to evaluate the thermal shock resistance of refractories. The effective fracture energy (γeff) is known as the parameter which affects to the thermal shock resistance. The objective of this study is to identify the effect of adding fine particles on the γeff. The samples were prepared by changing the fraction of fine alumina (average particle size is 3.4 µm) against coarse alumina (average particle size is 550 µm) and the effect of adding fine particles on the γeff was evaluated. The γeff was measured by Work of Fracture method. The value of γeff was enhanced to a maximum when the fine alumina fraction was 20-30 mass%. The reason could be explained by the apparent porosity and the roughness of the surface. Adding appropriate amount of fine alumina brought lower apparent porosity and rougher surface, leading to higher γeff.
For the applications of CFRTP to car components in the automotive industry, it is necessary to reduce the cost of the molding process. Recently, a heating method of the mold by using high frequency direct resistance heating, which heats only the mold surface by joule heating is attracting a great deal of attention, as it enables fast mold heating for cost reduction. When the high frequency alternative current is applied to the upper and lower molds in the same direction, however, the temperature of the press surface of the mold is inefficiently heated due to the attenuation of magnetic field. Furthermore, although the CFRTP molding method using the proximity effect was developed, in which the high frequency alternative current is applied to the upper and lower molds in the opposite direction, electric short circuit of the molds by current difference is one of the issues to be solved. In this study, the CFRTP molding method was developed by applying alternating current to only the lower mold in which the lower mold was heated with direct resistance heating and the upper mold and carbon fiber fabric were heated by induction heating. One pair of rectangular solids was used as the simplest mold system and FEM analysis of the electromagnetic field and heat transfer were compared with the experimental results. The upper mold and carbon fiber fabric were successfully heated by induction heating from the applied alternating current to the lower mold. The mold was efficiently heated by reducing the thickness and using materials with relatively higher magnetic permeability.
In a series of studies, it is aimed to develop fillings for holes formed by pulling-out piles. Cement-bentonite is used as a filling in general. Although cement-bentonite has an advantage of being able to perform blending according to circumstance of work on site, cement and water cause segregation, so uniform filling is difficult. In addition, there is a disadvantage that cement-bentonite cannot perform a predetermined strength when diluted by penetration of groundwater and so on. Sodium carbonate (Na2CO3) is a substance expected to suppress the segregation of cement-bentonite and to speed up the development of strength. In this study, we conducted an indoor mixing test on fillings mixed with Na2CO3 into cement-bentonite which is a mixture consisting of water, cement and bentonite, and examined various characteristics from the viewpoint of physical and chemical aspects. The following two points were clarified; (i) by mixing Na2CO3, bleeding of cement-bentonite is suppressed and (ii) by mixing Na2CO3, the strength development time of the cement-bentonite becomes faster and the long-term strength also increases. These two points are considered to be due to the improvement of the swelling property of bentonite, the early strength development of cement and the formation of calcium carbonate (CaCO3).
Expecting improvement of resistance against cracking and durability, short fibers such as steel fibers and organic fibers have been mixed into spray mortar for slope protection. On the other hand, in order to promote proper management of bamboo forests, it is necessary to develop effective application of bamboo materials. For these reasons, in this research, the tensile strength and the bond strength of a bamboo fiber used for spray mortar were investigated by laboratory experiments. After that, the mechanical properties, under the cyclic wet and dry condition and the resistance against freezing and thawing of spray mortar containing bamboo fibers were examined by spraying experiment. As a result, it was confirmed that mixing of bamboo fibers as 0.75% improved mechanical properties and durability of spray mortar, such as flexural toughness, adhesion strength to the base surface after cyclic wet and dry, and resistance against freezing and thawing. In addition, higher flexural toughness and adhesion strength to the base surface were obtained by mixing both of bamboo fibers and vinylon fibers or by admixing of fly ash.
The purposes of this study are to investigate the design equations for the bond strength and the pull-out bearing capacity of a post-installed screw anchor with an epoxy resin adhesion and correlation between the pull-out bearing capacity and the torque capacity. In the previous study, the pull-out and torque tests have been carried out for the post-installed screw anchor embedded into concrete slabs. In this study, the same tests were carried out with two levels of compressive strength of concrete. From the results of the pull-out tests, each equation for the bond strength and the pull-out bearing capacity failed in the cone failure and combined failure modes was proposed based on the empirical equation. Furthermore, the correlation between the pull-out bearing capacity and the torque capacity was evaluated. Then, they had a linear trend as well as the previous study.