From a viewpoint of creation of a recycling society, it is essential to establish a method for recycling waste gypsum boards because large amount of gypsum board are scrapped with rehabilitation of architectural structure. In this study, we tried to reuse the gypsum board as a phosphorus adsorbent. Test pieces cut out from a commercial gypsum board were immersed in Na2CO3 aqueous solutions of various concentrations to precipitate CaCO3 as crystallization sites of calcium phosphate on the surface of the specimens. The amount of CaCO3 precipitated on the surface increased with increasing Na2CO3 concentrations. Therefore, the specimens carbonated in the highly concentrated Na2CO3 aqueous solution showed the higher removal ratio in the early stage of phosphorus removal, but the surface layer of the specimens peeled off after long-term immersion in the phosphorus solution due to the dissolution of gypsum. On the other hand, the specimens carbonated in a dilute Na2CO3 aqueous solution showed the lower phosphorus removal ratio in the early stage of phosphorus removal but kept the original shape even after long-term immersion in the phosphorus solution. The phosphorus removal efficiency after immersion in the phosphorus solution for 10 days was about 95% regardless of Na2CO3 concentration, that is, the amount of CaCO3 precipitate on the surface of the specimens.
Porous MgAl2O4 ceramics were fabricated by impregnating porous Al2O3 bodies calcined at 1250℃ with Mg(NO3)2 saturated aqueous solution under reduced pressure, followed by firing at 1500℃. Porous Al2O3 bodies with continuously long-ranged pore structure and cross-linked one were prepared by a unidirectional freeze casting using aqueous Al2O3 slurries containing urethane latex binder (ULB) and water-soluble binder (PVA), respectively. The effect of the micro structure of Al2O3 bodies on MgAl2O4 formation was investigated. In the case of the porous Al2O3 body with continuously long-ranged pore structure, the amount of MgAl2O4 formed on firing at 1500℃ was larger than that for the porous Al2O3 body with cross-linked pore structure and a single-phase MgAl2O4 porous ceramic was obtained by four times impregnation. However, in this case, the surface of the porous Al2O3 body peeled off gradually with repeating impregnation. On the other hand, in the case of the porous Al2O3 body with cross-linked pore structure, about 10% Al2O3 remained after four times impregnation, but the structural disintegration caused by repeating impregnation was not observed. The cross-linked pore wall was effective to increase the strength of the calcined porous Al2O3 bodies but it was difficult to make the solution of Mg(NO3)2・6H2O into the small pore, resulting in a decrease in the rate of formation of MgAl2O4.
Soft pastel, lightly pressed with body pigment, has various colors close to the color pigments. We built the hypothesis that a certain volume of body pigment provides delicate nuance of color, tone, and texture to soft pastels. We examined the effect brought by two types of body pigments regarding color and strength respectively. Experimental results supported our hypothesis. About color, we obtained lower numerical values of Value and Chroma when we used porcelain clay than calcium carbonate (CaCO3). In other words, calcium carbonate produces light and bright color, and porcelain clay produces tint or neutral color. Concerning strength, applying porcelain clay, fracture stress was further increased than CaCO3. Furthermore, we examined the relationship between the drawing medium (pastel) and the support medium (paper etc.). The result showed that the weaker the drawing medium strength becomes, the more the pigmenting (coloring) becomes capable with weak pressure. But easy pigmenting does not always mean generating rich and various color tones. Those facts suggested the possibility that optimum numeric value in medium strength would be found out, which enable us to perform broader expression.
An approximate permanent strain of 0.33% was observed in Ce-TZP/alumina nanocomposite (NanoZR) after static fatigue tests (4-point bending) carried out at room temperature under 865 MPa for 360h. For the deformed specimens, crystal phase transformation, ferroelastic domain orientation, and residual stresses were investigated by using small-area XRD with 2D detector. The monoclinic content of the ground (before testing) and tensile surface (after testing) were 17.2 vol% and 25.4 vol%, respectively. Small amount of crystalline orientation which resulted from ferroelectric domain orientation was observed at both tensile and compressive surfaces. The obtained results revealed that plastic deformation was attributed mainly to volume dilatation involved in t-m transformation on the tensile surface and partially to ferroelastic domain orientation on both surfaces. It was shown that residual stress associated with monoclinic content. Permanent strain and ferroelasticity from 4-point static fatigue test were completely disappeared after annealing at 1100°C. However, residual stress still remained which showed the relationship between the residual stress and monoclinic content in the specimen.
TiO2(110) surface is known as a model of heterogeneous catalyst. For more realistic and practical applications, understanding of both local structures and properties induced by niobium dopants, calcium contaminants and oxygen defects is necessary. We investigated the effect of such impurities and defects on surface structure of Nb-doped TiO2(110) with different Nb concentrations (0.05 and 0.5 mass%) by scanning tunneling microscopy (STM) in ultra-high vacuum (UHV). A variety of Ca-induced structures were observed on both sample surfaces. After Ar sputtering, the 1×1 structure appeared on both samples. After annealing at 1273 K for half a day, the cross-linked 1×2 surface structure appeared on the 0.05 mass% sample, while no structural change was observed on the 0.5 mass% one. This result suggests that in the case of low Nb concentration, charge transfer by oxygen ions as well as electrons become considerable while major carriers are exclusively electrons in the sample with high Nb concentration.
Structure and air-oxidation behavior of the isotropic pitch-based carbon fiber were investigated. The carbon fiber was heat-treated with various temperatures in the range from 1000 to 2500℃ under argon gas atmosphere. Lattice constant d002 of the carbon fiber obtained by powder X-ray diffraction analysis was significantly reduced by the heat-treatment from 1500 to 2000℃. The crystallite sizes of the carbon fiber Lc (002) and La (110) were only 3nm even after heat-treatment with 2000~2500℃. While the carbon fibers heat-treated with 1000 and 1500℃ showed broad peaks of D- and G-bands in Raman spectra, those peaks became sharp after heat-treatment with more than 2000℃. It was observed by thermogravimetry (TG) that both air-oxidation starting temperature of the carbon fiber and activation energy of the oxidation reaction became higher as the increase of heat-treatment temperature of the carbon fiber. In the air-oxidation test which was carried out at 550℃ under stagnant air, the carbon fiber heat-treated with 1000℃ lost its weight by 35% for 1 hour since starting the test. On the other hand, the carbon fibers heat-treated with 2000 and 2500℃ only lost their weights less than 0.1% for 1 hour since starting the test. After 3 hours from the start of the test, the rates of weight loss of the carbon fibers heat-treated with 2000 and 2500℃ increased about 5 times compared with that of initial 1 hour. It may be noticed that new active points in the carbon fiber were created by air-oxidation and these newly created points accelerated the air-oxidation reaction. For the carbon fibers heat-treated with 2000 and 2500℃, much higher peaks of D-band in Raman spectra were observed after 10% weight loss than those of before air-oxidation, and these findings are probably due to the newly created active points.
In the previous research the intensity of singular stress at the end of interface for bonded plate was discussed under arbitrary material combinations. Then it was found that the bonded strength of butt joint can be evaluated in terms of the singular stress in good accuracy. In this study the intensity of singular stress for bonded pipe is newly discussed in comparison with the one of bonded plate. The finite element method is applied to calculate the intensity of singular stress with varying the material combination systematically. This method focuses on the results of first node locating at the end of the interface. Until now few studies are available for bonded pipe, in this study, the effect of the material combination on the intensity of singular stress is discussed by changing the material combination systematically. It is found that the intensity of singular stress of bonded pipe is 0.8-1.5times larger than the one of bonded plate for almost material combinations. This investigation may contribute to a better understanding of the debonding strength and initial interfacial cracking of bonded pipe.
In this study μ-focus X-ray CT was applied to analyze a material flow due to diffusion in porous rocks. Here, one-dimensional diffusion tests were performed using solution of potassium iodate (KI) as a tracer. As representatives of porous rocks, Berea sandstone and Kimachi sandstone were applied, and the diffusion phenomena including pore structures in the pore scale were visualized. In order to extract the density information due to the diffusion, image subtraction method was applied to the CT images. By applying the method, the density increment due to the diffusion and its location was easily extracted. It was found that the KI solute mainly diffuses in the pore networks in the case of Berea sandstone. On the other hand, it was found that the KI migrates not only through pores but also micro pores/fractures in grains in the case of Kimachi sandstone. The difference of diffusion velocity in both samples was also discussed.