We synthesized Eu doped (Zn2-yEuy)(TixSn1-x)O4 (0 ≤ x ≤ 1, 0 ≤ y ≤ 0.5) phosphors using polymerized-complex and coprecipitation methods. As a result, those synthesized by the polymerized-complex method emitted brighter. Red emission was observed around 600 nm by the 4f-4f transition of Eu3+ ion in the range from x = 0 to 0.7. With increasing the Ti content over x = 0.9, the emission color shifted to the green color. The green emission was caused by defects in the crystal of the host materials. The crystal structure and morphologies were characterized using powder X-ray diffraction (XRD) and a scanning electron microscope (SEM), respectively. We assumed that the difference in the emission color was caused by the difference in the occupation-site for Eu3+ ion in the crystal structure.
Eu- and Pr-doped ceria, Ce1-x-yEuxPryO2-δ (where x=0, 0.05, and 0.01, y=0, 0.0005, and 0.05) powder samples were synthesized by a coprecipitation method followed by heat treatment at 600°C for 3 h in air. The samples were characterized by XRD, color measurement, and UV-Vis diffuse reflectance spectroscopy. X-ray diffraction data indicated the formation of Ce1-x-yEuxPryO2-δ solid solution with fluorite-type structure. The powders of Ce1-yPryO2-δ (y=0, 0.0005, and 0.05) turn to dark brown color with increasing Pr content, where samples in a smaller amount of Pr content can get high brightness near yellow-brown. It was found that Eu- and Pr-codoped ceria samples，Ce0.9945Eu0.005 Pr0.0005O2-δ and Ce0.9895Eu0.01Pr0.0005O2-δ，exhibited change of time-dependent color behavior. The UV-vis versus time measurement showed clear photochromic properties depending on absorption due to Eu3+-Pr3+ center in CeO2.
As a research to explore the application of layered zinc hydroxide incorporated with ion exchangeable anions between layers as a phosphorus removal material, a layered zinc hydroxide containing sulfate ions between the layers was synthesized. Its chemical formula is Zn4SO4(OH)6･n H2O (ZHS). The effects of pH during the synthesis and of the aging temperature on crystal composition and phosphorus removal ability were investigated. From the XRD analysis, it was found that ZHSs with different numbers of crystal water were obtained depending on the pH during the synthesis and aging temperature. It was also found that zin oxide was more likely to be formed as the pH during the synthesis and the aging temperature were increased. The phosphorus removal capacity of each sample powder was evaluated by immersing each sample in a potassium dihydrogen phosphate aqueous solution adjusted to a phosphorus concentration of 100 ppm for 10 minutes. All samples showed phosphorus removal ratio of above 80%. Particularly, the ZHS powder synthesized at pH 6 showed the phosphorus removal ratio above 95% regardless of the aging temperature. In the case of ZHS synthesized at pH 7 or higher, zinc oxide was formed as the aging temperature increased, and thus, the phosphorus removal ratio decreased. However, for ZHS, the formation of zinc oxide by aging was extremely few compared with the layered zinc hydroxide containing nitrate ions between the layers, which was previously reported by the authors, and so the decrease in the phosphorus removal rate was also small.
Porous silica was synthesized by using denatured collagen as a template. The shape, pore characteristics and synthesis mechanism for porous silica synthesized by using denatured collagen (DC-PS) was compared with that synthesized by using collagen fibril (CF-PS) as a template. It was found from scanning electron microscopy observation that DC-PS had a structure in which particles of several micrometers were aggregated. We also carried out N2 adsorption / desorption isotherm measurement in order to evaluate the porous property of porous silica and revealed that both DC-PS and CF-PS possessed only micro pores. Detailed analysis of micro pores by using Saito-Foley method cleared that the pore size distribution of DC-PS was narrower than that of CF-PS. Moreover, it was revealed that silica sources interacted easier with denatured collagen than collagen fibril by thermogravimetric analysis. These results suggested that the arrangement of collagen molecules affected the porous properties of silica.
The crystallization and transformation behaviors from amorphous and crystalline silica to tridymite were investigated. Silica glass and precipitated silica as an amorphous silica and quartz as a crystalline silica were used for silica source. These silica were well mixed with tridymite as a seed crystal and fired at a temperature from 1100°C to 1400°C for 4, 6 and 12 h to form tridymite phase. The effect of CaO as a dopant on the formation of tridymite was also examined. Regardless to the presence or absence of CaO, the seed crystal tridymite was needed for phase transformation from amorphous silica or quartz to tridymite. In addition, it was found that silica glass was easier to transform to tridymite phase than precipitated silica and quartz. For samples without CaO, tridymite could be directly achieved from amorphous silica without the assistance of liquid phase. For samples doped with CaO, on the other hands, the dominant reaction for transformation to tridymite was the precipitation from liquid phase that was caused by the reaction between doped CaO and cristobalite crystallized from amorphous silica. The significant behaviors that occurred in the samples with CaO were (1) the formation of cristobalite and CaSiO3 which reduced tridymite amount and (2) the liquid phase formation which led the precipitation of tridymite.
The influence of pore structure on the water purification ability of microorganism-supported alumina body was investigated. Porous alumina bodies having various pore sizes and pore volumes were prepared by changing the amount of pore forming agent with different particle size added. Furthermore, the influence of firing temperature on microstructure was investigated. The loading of the microorganisms on the alumina porous body was carried out by immersing the alumina porous body in a culture solution containing yeast, lactic acid bacteria and Bacillus natto for 5 days. The water purification ability of the alumina porous body carrying microorganisms was evaluated by measuring the change in COD after immersion of the porous body for a predetermined time in model waste water having an initial COD value of 180 ppm prepared using glycine and D(+)-glucose. From the results of the SEM observation, adhesion of microorganisms and formation of biofilm were confirmed on the surface and near the pores of the alumina porous body. The decreasing ration of COD of model waste water was largely influenced by the pore volume rather than pore volume of the alumina porous body and increased as the pore volume increased. Moreover, in order to obtain a higher water purification ability, it is preferable that the pore volume of the alumina porous body is above 0.25 cm3/g. When the firing temperature is high, the surface of the alumina porous body became smooth, so microorganisms were less likely to adhere. As a result, the water purification ability of the porous alumina fired at high temperature tends to be lower as compared with that fired at lower temperature.
The removal of lead using calcium phosphate precipitated on the surface of a crystallization type phosphorus adsorbents which were composed mainly of gypsum and calcium carbonate was investigated. Since calcium hydrogen dehydrate(DCPD) precipitated on the surface of phosphorus adsorbent at the time of removing phosphorus did not have ion exchange ability, removal of lead ion was examined after transforming DCPD into hydroxyapatite(HAp) having ion exchange ability with heavy metal ion. The conversion of DCPD to hydroxyapatite was attempted by aging in aqueous solutions of various pHs and temperatures. As a result, it was found that the transformation of DCPD to hydroxyapatite was easy to proceed by aging in an aqueous solution with high temperature and pH. In this study, a phosphorus adsorbent aged in an aqueous solution adjusted to pH 6 with aqueous ammonia at 60 °C was subjected to lead removal experiment because DCPD precipitated on the surface of the phosphorus adsorbent was almost completely transformed into hydroxyapatite under this aging condition. It was revealed that removal of lead ions by a phosphorus adsorbent on which HAp was precipitated on the surface proceeded by ion exchange of HAp and formation of fine crystal particles containing lead. However, the removal ratio of lead ions was about 60 % of the initial concentration of 50 ppm, and about 40 % of lead ions remained in the solution. This result suggested that some of the lead ions formed complexes, such as [Pb(OH)4]2-, with the hydroxide ions eluted from HAp.
This work aimed to improve age-hardenable Cu-Ni-Sn=alloys that have high strengths, excellent stress relaxation resistances, and moderate electrical conductivities. A Cu-9wt%Ni-9wt%Sn alloy with proposed compositions of Ni and Sn, and Cu-9wt%Ni-6wt%Sn, Cu-15wt%Ni-8wt%Sn, and Cu-21wt%Ni-5.5wt%Sn alloys with almost the same compositions of Ni and Sn as commercial Cu-Ni-Sn alloys were first peak-aged at 400°C, then cold-rolled to 60% or 80%, and finally annealed at 400°C to improve the stress relaxation resistance of the four cold-rolled alloys ((9-9), (9-6), (15-8), and (21-5.5) alloys). The (15-8) and (21-5.5) alloys exhibited higher tensile strengths (σu≈1300 MPa) than the (9-9) and (9-6) alloys (σu≈1200 MPa), but lower electrical conductivities (E =9 and 6%IACS) than the latter alloys (E =12 and 11%IACS). The differences in the σu between the four alloys were caused by the differences in the dislocation density, deformation twin boundary spacing, and inter-precipitate spacing between them. The four alloys had good stress relaxation resistances. This was attributable to both the decrease in the density of mobile dislocations by the formation of Cottrell atmospheres of Sn atoms on the dislocations introduced by cold rolling during annealing, and the increase in resistance to moving dislocations by Cottrell atmospheres of Ni and Sn atoms on the moving dislocations caused by their chemical bonding. The stress relaxation resistance of the (21-5.5) alloy was the best of the four alloys (the lowest stress relaxation rate R=9%), and the (15-8) alloy exhibited the highest value of R=19. The differences in the R between the four alloys were mainly ascribed to the differences in the amounts of dissolution of Ni and Sn in the Cu matrix between them.
It is known that PTFE compacts fabricated using recycled PTFE powder which is melted once show much lower mechanical strength than those fabricated using virgin PTFE powder as-polymerized. However, the reason has not been clear still. Then, in this study, characters of virgin PTFE and recycled PTFE powders and properties of virgin PTFE and recycled PTFE compacts were investigated. The crystallinity and the melting point of the recycled PTFE powder were lower than those of the virgin PTFE powder, which are well-known differences between the recycled PTFE and the virgin PTFE powders. In addition, we first found that while the virgin PTFE powder had not only granular morphology but also fibrous morphology, the recycled PTFE powder did not have fibrous morphology. The fabricated recycled PTFE compacts had higher porosity and much lower mechanical strength than the fabricated virgin PTFE compacts. The fibrous morphology of the virgin PTFE powder was entangled with PTFE particles during compressing, which resulted in the higher packing structure, furthermore, during firing the densification and the fusion at the PTFE particle-interfaces where the entangled structure was formed proceeded much more, which resulted in the strong PTFE particle-interfaces. On the other side, because the recycled PTFE powder having no fibrous morphology could not formed the entangled structure, the densification and the fusion at the PTFE particle-interfaces did not almost proceed during firing and PTFE particle interfaces were not almost strengthened. So not only the higher porosity but also the week particle-interface where interlocking structure of fibrous morphology was not formed made the mechanical strength of recycled PTFE compacts lower.
It is an important subject to characterize creep strength property of long-term operated Mod.9Cr-1Mo welded joints which are widely used for pipes in USC power plants for accurate creep damage assessment. Miniature creep specimens with 1mm diameter were machined from base metal, weld metal and heat affected zone(HAZ) of an about 80,000 hours operated longitudinal welded pipe with X shape weld groove. Creep tests of these miniature specimens were performed in inert gas atmosphere by the specially developed creep testing machine. Creep strengths of the base metal and the HAZ in the long-term used welded pipe were similar to those in an undamaged welded joint. On the other hand, creep strain rate of the weld metal in used welded pipe is much faster than that in the undamaged welded joint indicating degradation of microstructure during operation. Standard size welded joint specimens were taken from near surface and X-shape regions of the welded pipe to understand creep rupture strength. Creep rupture time of the standard welded joint specimens taken from the used welded pipe was much shorter than that of the undamaged welded joint. The standard welded joint specimens taken from the X shape region ruptured at HAZ and those taken from the near surface region ruptured at weld metal. It was suggested by finite element creep analyses of the standard welded joint specimens that the highest axial stress occurred at HAZ in the specimen taken from X-region causing Type IV failure and that occurred at weld metal in the specimen taken from near surface region causing failure at the weld metal.
This paper is concerned with the mixed boundary-value problem of an infinite plate with an elliptic hole, into which a smooth elastic elliptic plate is inserted. Since the infinite plate is subjected to a uniaxial tension at infinity, separations are produced along the boundary between the inserted plate and the hole. The contact pressure between the inserted plate and the hole is expressed in a convergent series whose differential form is also convergent, so that the stress and displacement generated along the boundary can be numerically analyzed by the point-matching method. Using the numerical results for various elliptic shapes, the influence of fit tolerance condition and elastic moduli of plate and inserted elliptic plate is shown with the stress distribution around an elliptic hole. The effects of the magnitude of fit tolerance, load and the shape of an embedded elliptic plate on the condition of stress concentration are analytically clarified in this study. The main results are as follows: [Ⅰ] The contact region, stress, and the displacement depend only on the one parameter containing the magnitude of fit tolerance and load. [Ⅱ] When the fit tolerance is zero the contact region and stress distribution of elastic plate do not vary with the magnitude of load. [Ⅲ] When the fit tolerance is not zero, the contact region and stress distribution of the elastic plate vary with the magnitude of tensile load.
Micro Plasma Arc welding is used to remelt thin sheets of austenitic stainless steel (AISI 316L) 1mm. In this article the effects of micro plasma factors (2.4 mm electrode diameter) on fusion pool geometry parameters namely width, height and HAZ’s width of austenitic stainless steel sheets are analyzed. The mathematical models have been developed by response surface method, in which three factors, three levels and central composite design were used to develop mathematical models, incorporating micro plasma parameters and fusion pool geometry. The adequacy of the models was checked by ANOVA technique. Variations of output responses with input process variables were discussed in both effects: main and interaction. As a result, fusion pool geometry parameters can be estimated by using the developed mathematical models.