Synthesis of Highly Oriented K(Ta,Nb)O3 (Ta:Nb = 65:35) Film Using Metal Alkoxides

Highly oriented K(Ta,Nb)O₃ (Ta:Nb = 65:35) (KTN) thin films of perovskite structure were synthesized successfully on Pt(100)/MgO(100) substrates from a metal alkoxide solution through reaction control. Homogeneous KTN coating solutions prepared from KOC₂H₅, Ta(OC₂H₅)₅, and Nb(OC₂H₅)₅ in ethanol were analyzed by ¹H, ¹³C, and ⁹³Nb NMR spectroscopy. The KTN precursor included a molecular-level mixture of K[M(OC₂H₅)₆] (M = Ta, Nb) units interacting in ethanol solution. X-ray pole figure measurement showed that perovskite KTN films crystallized on Pt(100)/MgO(100) substrates had not only a (100) orientation but also a three-dimensional regularity of grains. The remanent polarization and coercive field of the KTN film (thickness, 1.0 μm) crystallized at 700°C were 1.5 μC/cm² and 8.7 kV/cm, respectively, at 225 K.     

The concept of uncertainty in animal experiments using aversive stimulation.

Reviews rat experiments using aversive stimuli in which some element of uncertainty was involved. Nine cases of conditions that produce uncertainty are described, and relevant experimental facts are examined. Rats were found to prefer situations involving certainty to those involving uncertainty, and the rats' basal rate of responding was found to be less in suppression situations involving uncertainty about aversive environmental events than in those involving relative certainty. Results are obtained when the aversive stimuli the rats received were physically matched in quantity among the conditions compared. Results are discussed with reference to the safety signal, preparatory response, time allocation, contextual fear, and information hypotheses. It is concluded that the function of the concept of uncertainty is to organize a class of studies that are otherwise unrelated. (59 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structure of molybdenum oxide clusters prepared in zeolite cages

Molybdenum hexacarbonyl entrapped in NaY zeolite was oxidized with molecular oxygen by UV-irradiation at room temperature or by thermal treatment at 343–373 K. Both oxidation procedures resulted in the identical molybdenum(VI) oxide; molybdenum dimer species (Mo-Mo distance: 0.321 nm). The Mo-Mo bonding of the oxide species was degraded on an evacuation at 673 K, while it was considerably stable in the presence of gaseous oxygen.     

Effect of fast-neutron irradiation on deformation twinning in zirconium deformed at 77 K

The effect of neutron irradiation on twinning deformation is investigated at 77 K using unirradiated and to a fluence of 4.1 × 10¹⁹n/cm² irradiated zirconium. The slip line density N_s, the twin volume fraction V_t and the twin density N_t for both specimens were determined as a function of strain by means of optical microscopy. The twins were determined using the diffraction profiles of {101̄2} twins at the early stages, as well as, {112̄2} and {112̄4} twins at the latter stages of deformation. It is shown that the nucleation of twins was affected more strongly than the growth by neutron irradiation.     

Modification of mckay-perring method for the calculation of mean activity coefficients of solutes in mixed solutions

formerly Graduate Student, Department of Metallurgy, Kyoto University, Japan     

Preparation of TiO2 hollow microparticles by spraying water droplets into an organic solution of titanium tetraisopropoxide

Hollow, spherical TiO₂ microparticles several tens of micrometers in diameter were prepared by spraying water into an organic phase containing titanium tetraisopropoxide (TTIP) as a titanium source. The rapid hydrolysis of TTIP at the water-oil interface resulted in the formation of a TiO₂ shell covering the water droplet. Hexane and cyclohexane were better solvents than isopropanol for fabricating hollow spherical microparticles, suggesting the importance of immiscibility of the solvent with water in this synthesis method. The average particle size increased as the distance from the nozzle to the surface of the TTIP solution was increased. The shell thickness was reduced by the addition of ethanol to the sprayed water droplet. These results demonstrate the controllability of the structure of TiO₂ hollow microparticles, including the diameter and the shell thickness.     

Mixing and separation characteristics of isobutane with refrigeration oil

This paper discusses the transient mixing and separation characteristics of isobutane with/from refrigeration oil. The mixing/separation processes are observed and investigated experimentally in a glass cylindrical vessel. Since liquid isobutane is less dense than refrigeration oil, the mixing process proceeds one dimensionally by diffusion from the interface between isobutane gas and refrigeration oil. The progress of mixing, therefore, is very slow compared with a combination of halocarbon refrigerant and refrigeration oil having convection flow during the mixing process. The diffusion process can be analyzed using a one-dimensional diffusion model with an appropriate diffusion coefficient, which increases linearly with temperature. The separation of isobutane from the oil–refrigerant mixture occurs at the interface and the denser oil from which isobutane is separated causes a convective flow. Bubble generation under the depressurized conditions is unstable, but in the most cases, it tends to start when a high super saturation degree is reached. The temperature change during the separation process is estimated using latent heat as the separation heat of refrigerant.     

Studies on aluminum-doped ZnO films for transparent electrode and antireflection coating of β-FeSi2 optoelectronic devices

β-FeSi₂ can be used for various optoelectronic devices owing to its superior material features including high optical absorption coefficient and direct band gap of about 0.8 eV. Due to its high refractive index (>5.6), however, suitable antireflection coating (ARC) is necessary for practical device applications. In order to increase the effective areas of optoelectronic devices, transparent electrodes should be also developed. In this work, Al-doped ZnO (AZO) films were fabricated by sputtering on β-FeSi₂ thin films and were found suitable for both transparent electrodes and ARC films. Choosing optimum substrate temperature and sputtering rate, high quality AZO films were formed. The conductivity of AZO films was as high as 3×10³ S/cm and ohmic contact was easily achieved between AZO and β-FeSi₂ films, indicating AZO film as an ideal transparent electrode for β-FeSi₂. The transmittance of 400-nm-thick AZO films was >80% and >70% in the wavelength ranges 400-1400 and 1400-1600 nm, respectively. By changing the thickness of AZO film, the central wavelength of minimum reflectance was adjusted to 1550 nm where the total reflectance of AZO/β-FeSi₂/Si structure was reduced below 2%.