Influence of Tetragonality on Tetragonal-to-Monoclinic Phase Transformation during Hydrothermal Aging in Plasma-Sprayed Yttria-Stabilized Zirconia Coatings

The influence of tetragonality, which is defined as the lattice parameter ratio c / a , on the tetragonal-to-monoclinic phase transformation during hydrothermal aging was investigated in yttria-stabilized zirconia coatings. The yttria content was adjusted in the range of 4–8 mass% (denoted as x YZ, where x = 4–8 and YZ represents the yttria-stabilized zirconia). The tetragonality of the zirconia in the as-sprayed coatings was less than that in the powders. To change the tetragonality for each yttria content, the coatings were annealed at 1273 K before aging. Without annealing, the phase transformation was prevented only in 8YZ. When annealing was applied, an increase of the tetragonality (i.e., recovery of the tetragonality) was observed, and transformation during hydrothermal aging was also suppressed in 6YZ. It was concluded that the increase in tetragonality that occurred without a change in the yttria content was suggested to be caused by the lattice relaxation of the tetragonal phase, and this relaxation is believed to cause a reduction of the critical yttria concentration, thus preventing the phase transformation.     

Degradation analysis of dye-sensitized solar cell module after long-term stability test under outdoor working condition

Using Raman spectroscopy in addition to electrochemical impedance spectroscopy, we have clarified the deteriorated components of dye-sensitized solar cells (DSCs) module after the longest durability test in the world under outdoor working condition for ～2.5 years. It was confirmed that the N719 dye-adsorbed TiO₂ electrode and carbon counter electrode were almost stable; therefore, the photocurrent (Jsc) was maintained during the outdoor working. The photovoltages (Voc) and the filling factors (FF) slightly decreased due to the increase of the Nernst diffusion impedance of triiodide (I₃^?), resulting from the change of the components in the electrolyte.     

Development and Application of Sintering Dynamics Simulation for Automotive Catalyst

Sintering behavior of Pt/γ-Al₂O₃, Pt/ZrO₂ and Pt/CeO₂ catalyst was studied using an originally developed 3D sintering simulator. Experimental results were well reproduced. While Pt on the γ-Al₂O₃ sintered significantly, Pt on CeO₂ presented the highest stability against sintering. On the other hand, grain growth of supports was significant in the order; ZrO₂ > CeO₂ > γ-Al₂O₃.     

The effect of growth atmosphere and Ir contamination on electric properties of La<Subscript>3</Subscript>Ta<Subscript>0.5</Subscript>Ga<Subscript>5.5</Subscript>O<Subscript>14</Subscript> single crystal grown by the floating zone and Czochralski method

The influence of growth atmosphere and Ir contamination on electrical resistivity of langatate (La₃Ta_0.5Ga_5.5O₁₄; LTG) was studied. LTG single crystals were grown via the Czochralski method under different oxygen partial pressures with Ir contamination from the Ir crucible. In addition, LTG crystals were grown by the floating zone method and they were not contaminated by Ir. The electrical resistivity and ionic transport number of these crystals were measured in the temperature range 300–1000°C. The conduction mechanism of LTG changed at about 720°C. At T < 720°C, electronic conduction was dominant, and the resistivity was affected by growth atmosphere as well as Ir contamination. In contrast, at T > 720°C, ionic conduction was dominant, and the resistivity was affected only by Ir contamination. In both temperature regions, Ir contamination decreased the resistivity by an order of magnitude.     

Preparation of lithium aluminosilicate glass-ceramic monolith from metal-alkoxide solution

Crack-free dried gel monoliths of the composition Li₂O · Al₂O₃ · 4SiO₂ have been prepared as a precursor of lithium aluminosilicate glass-ceramics by the hydrolysis and polycondensation of mixed metal alkoxides in solutions containing LiOCH₃, Al(O-secC₄H₉)₃, Si(OC₂H₅)₄, alcohols and water. Higher concentrations of water in the starting solution, close control of reaction conditions and slow drying rates produced crack-free gel monoliths of cylinder shape, 37 mm in diameter and 35 mm in height. Properties of the gel monolith and their change with heating have also been examined.     

Tri-phasic zirconia electrolyte for the in-situ determinations of silicon activities in hot metal

Tri-phasic zirconia electrolyte, which consists of cubic ZrO₂–MgO solid solution, monoclinic ZrO₂ and 2MgO · SiO₂, was applied to solid state electrochemical sensor for rapid determinations of silicon activities in hot metal. The performance of the cell: Mo + MoO₂ / tri-phasic zirconia electrolyte / Fe + Si + C was tested with molten iron at 1723 K. The cell potentials showed good sensitivity to the variation of silicon content in the melt.     

Sol-gel synthesis of silica gel disc as applied to supports of organic molecules with optical functions

In order to synthesize transparent, crack-free silica-gel bodies used as supports for organic substances with optical functions such as fluorescent, lasing, photochromic, photochemical hole burning and non-linear optical functions via the sol-gel route, the effects of the composition of the starting solution on the transparency of the gel, the occurrence of cracks and the bulk density of the gel have been investigated for Si (OCH₃)₄-H₂O-CH₃OH-HCl and Si (OCH₃)₄-H₂O-CH₃OH-HNO₃ solutions. It was found that the addition of specific amounts of water and acid gave transparent, crack-free silica gel bodies, which could be used as supports for optically functional organic substances. It was also found that organic substances such as quinizarin and rhodamine B incorporated into these gels were uniformly dispersed at the molecular level.     

Changes in levels of monoamines and their metabolites in incompletely ischemic brains of spontaneously hypertensive rats

In order to investigate changes in levels of monoamines and their related substances together with those of other neurotransmitters (acetylcholine and GABA), choline and substances related to energy metabolism (ATP, lactate and glucose) accompanying incomplete cerebral ischemia, a bilateral common carotid artery occlusion model of spontaneously hypertensive rats (SHR) was utilized. Animals were subjected to 1 or 2 h ischemia. Then the concentrations of substances were measured in the cerebral cortex, hippocampus and striatum and compared with control values. Due to the incomplete ischemia, ATP showed a moderate decrease, while lactate and choline increased remarkably, and GABA underwent a moderate increase. With regard to monoamines, both noradrenaline and serotonin levels were reduced in the cerebral cortex and hippocampus, whereas dopamine levels increased in the hippocampus. All monoamine metabolites, i.e. metabolites by monoamine oxidase (MAO), metabolites by catechol-O-methyltransferase (COMT), and metabolites by both MAO and COMT, underwent increases. The 3-methoxytyramine level in particular showed marked increases. Furthermore levels of precursor amino acids as well as 5-hydroxytryptophan rose. Acetylcholine decreased moderately only in the cerebral cortex. Among these changes, sustained increases in all the monoamine metabolites were characteristic of changes in the incompletely ischemic brain, suggesting that both COMT and MAO retain their activities in the incompletely ischemic brain.     

Optimal structure of sensor systems composed of nonidentical sensors

The sensor system has two types of contradictory failures; a fail-dangerous failure and a fail-safe failure. A method of obtaining the optimal structure is developed for the sensor system which is composed of general components. The optimal structure minimizes an expected damage, considering all possible boolean structures including noncoherent systems. A simple optimality criterion is obtained and several properties of the optimal structures are derived; a noncoherent structure can be optimal in some cases. A simple systematic search algorithm can be used effectively to determine the optimal system. Analytic solutions are obtained for systems composed of identical components. Illustrative examples are given.