Borate glasses containing Ag2O were prepared and their emission spectra were measured. The glasses showed blue emission by the excitation at 260nm and white emission at 320nm. The solubility of Ag2O decreases by the addition of SiO2 and the effect of SiO2 is similar to that of Na2O. The intensity of blue emission shows no dependence on SiO2 content, but that of white emission shows. Since the intensity of white emission also depends on Ag2O content, it is considered that this emission is caused by nano clusters of silver atoms formed by the reduction of Ag2O.
Iron oxide-doped ceria Ce1-yFeyO2-δ (where y=0, 0.01, 0.05, 0.10, and 0.20) and iron oxide-doped ceria-zirconia ZrxCe0.95-xFe0.05O2-δ (where x=0, 0.20, 0.40, 0.60, 0.80, and 0.95) powder samples were synthesized by a coprecipitation method and heated at 900℃ and 1230℃. The samples were characterized by XRD, colorimetric assessment and UV-Vis diffuse reflectance spectroscopy. Furthermore, the color glazes obtained by adding the samples to the basic glaze were heated at 1230℃ in air, and evaluated by colorimetric assessment. X-ray diffraction data revealed that Ce1-yFeyO2-δ samples with y ≥ 0.05 were composed of Fe-doped CeO2 solid solution and Fe2O3. The powders of Ce1-yFeyO2-δ showed dark red color and the glazes containing them also showed yellowish red color. In Fe-doped ceria zirconia samples heated at 900℃, the red color varied to orange and yellow with increasing x in ZrxCe0.95-xFe0.05O2-δ. However, the glazes containing them (with Zr) changed from warm color into pale like celadon. These warm colored materials show high durability against high temperature and environmental friendly properties, so the application as ceramic pigments can be expected.
Porous ZrO2 ceramic was prepared by a unidirectional freeze casting using aqueous slurries containing PVA. The effects of PVA content on the microstructure of sintered bodies were investigated by a scanning electron microscopy and a mercury intrusion porosimetry. Porous ZrO2 ceramic with continuously long-ranged pore structure was obtained by the unidirectional freeze casting of the aqueous ZrO2 slurry, followed by sublimation of ice and firing at 1400℃ for 1h in air. The PVA loading of the slurry scarcely affected the pore volume of sintered bodies. However, the pore size decreased and the compressive strength increased with increasing PVA loading in the slurry. When PVA was added, branch and ladder structures occurred in pore walls. Therefore, three dimensional pore structures developed due to the increased in the connectivities of the pore walls, resulting in the decrease in pore size and the increase in compressive strength.
Previously, we reported that on immersing the composite of crashed scallop shells and gypsum into KH2PO4 aqueous solution, DCPD(CaHPO4・2H2O) crystal precipitated on the surface of the composite and grew with increasing immersion time. In this study, the feasibility of using the scallop shells with DCPD precipitate after phosphate ion removal as an adsorbent of lead in waste water was evaluated. When the scallop shells with DCPD precipitate were immersed in an aqueous solution containing 50ppm Pb2+ at pH3, the concentration of Pb2+ in the solution deceased with increasing immersion time. The Pb2+ removal rate largely depended on the amount of DCPD precipitate on the surface of the scallop shells and increased with the amount of DCPD precipitate. From the results of SEM observation, EDX and XRD analysis, it was found that after immersing scallop shells with DCPD precipitate in the Pb2+ aqueous solution, DCPD converted into HAP(Ca10(PO4)6(OH)2) and hydroxypyromophite(Pb5PO4)3OH, HPY) whisker precipitated on the surface of HAP crystal. When DCPD converts into HAP, surplus PO43- ions dissolve into the solution and react with Pb2+ ions to form Pb5PO4)3OH. There results show that the scallop shells used for the adsorbent of phosphate ions would be reused as the adsorbent of lead in wastewater.
Zeolite A exhibits superior moisture-absorption characteristic because zeolite A has a high hydrophilicity and a lot of micropores in its crystal structure. So zeolite A is recognized to be one of excellent humidity conditioning materials. In conventional production method, however, zeolite A is produced as powders with a diameter of a few micrometers. In the present study, the bulky consolidated zeolite A was synthesized with sodium silicate solution, metakaolin, sodium aluminates, and sodium hydroxide at heat-treatment temperatures from 40℃ to 100℃. Characteristics of humidity conditioning were estimated. The consolidated monolithic zeolite A could be synthesized at a temperature of 50℃. The consolidated zeolite exhibited poor moisture-desorption characteristics, compared with excellent moisture-absorption characteristics. In order to improve the moisture-desorption characteristics, furthermore, the microstructure of consolidated zeolite A was controlled by foam formation technique due to the reaction between Al and sodium silicate solution. In consequence of the porous treating, the obtained porous zeolite A with pores diameter from 5 to 110 micrometer improved its moisture-desorption characteristics and had good humidity response.
Degradation of lining concrete happens naturally in the tunnels that have been commissioned for several decades, which require proper maintenance to ensure their safety and effective functions. The PCM shotcrete method by means of FRP grid, with the characters of high strength, low weight, high workability, strong resistance to corrosion, and negligible influence on the existing structures, has been used in tunnel maintenance to repair the damaged lining of some aged tunnels. Up to now, the construction cases are still few, and the design routine of this method based on quantitative evaluation on the reinforcement effect has not been established. In this study, the shear bond strength and the shear stiffness of typical FRP grids were estimated by conducting direct shear tests on FRP-PCM specimens. Those parameters were input into a numerical model of tunnel to quantitatively estimate the displacement control effect of the FRP-PCM method on tunnel lining. The experiment and numerical simulation results show that the FRP-PCM method has good reinforcement effect on tunnel lining and has high potential to be applied extensively in the maintenance of aged tunnels.
The composite wall made of a gutter, a pre-cast embedded mold and cast-in-place concrete looks like as if it is one unit structure. However, the boundary of gutter's sidewall and basal plate, which is made of a pre-cast embedded mold and cast-in-place concrete, is not strengthened by reinforcement bars, metal fixtures and etc. Therefore the wall exhibits very complicated deformation behavior when horizontal loading is applied. Furthermore, it is difficult to calculate yield strength and deformation by existing design procedures. In this study, the strength and deformation were measured directly using a trial product. Then, the possibility of evaluating the strength and deformation characteristics through 3D FEM frame analyses and 2D RBSM (Rigid Bodies Spring Model) is studied on the basis of experimental results.
Fracture behavior transition due to strain rate change in Fe-5%Si alloy with dislocation microstructures was studied to investigate the effect of pre-deformation on toughness. The Fe-5%Si alloy was multi-passed rolled (pre-deformed) at 1073K to various reductions up to 50% to introduce dislocation microstructure. The room temperature tensile deformation was conducted at various strain rates from 10-5 to 100/s. Electron backscattering diffraction measurements clarified that the dislocations were successfully introduced within the grains. All rolled alloys were fractured with local elongation (necking) at slower strain rate. When strain rate was faster, the local elongation disappeared and the fracture manner was turned to brittle. The strain rate at which fracture behavior changed increased with increasing of the reduction. On the other hand, the almost fully recrystallized Si steel was fractured in the brittle manner at any strain rate and the transition strain rate was not found. The fractured tensile specimen with no local elongations contains deformation twins ; however, these deformation twins were not observed in the fractured specimen with local elongations. This result indicates that the dislocation structure evolved during rolling suppressed the twinning and that the dislocation structure is effective for the enhancement of both ductility and toughness in Fe-5%Si alloy.
In this work, the ultra-high cycle fatigue behavior of Zr55Al10Ni5Cu30 metallic glass was investigated by using an ultrasonic fatigue testing method. Test alloy rods with a diameter of 8mm were prepared by tilt-casting with a copper mold. Test specimens were machined to hourglass shape (the minimum diameter ; 2.0mm), and then manually polished with polishing paste. They were tested at a frequency of 20kHz under a stress ratio of -1. The fatigue limit (σw) (half a total stress amplitude) and fatigue ratio (σw/σB) of the alloy were 893MPa and 0.53, respectively. Furthermore, no fish-eye like crack-growth morphology was seen on the fracture surfaces. The initiation region of fatigue cracking was always observed on the side surface of the specimens. A viscous-flow fracture region with large dimples between the fatigue crack-growth region and the final unstable fracture region was observed. This peculiar fracture morphology may be due to adiabatic heating of the metallic glass specimens during the fracturing, resulting in transition to supercooled liquid, under extremely high frequency of fatigue stress using ultrasonic loading.