Preparation of new heteronuclear (NH4)RE[FeII(CN)6]·nH2O complexes (RE = La,Ce, Pr,Nd, Sm,Gd, Dy,Y, Er,Lu) and their low-temperature decomposition for perovskite-type oxide

New heteronuclear (NH₄)RE^III[Fe^II(CN)₆]·nH₂O complexes (RE = La, Ce, Pr, Nd, Sm, Gd, Dy, Y, Er, Lu) were synthesized and their thermal decomposition products were investigated. The crystal structure of (NH₄)RE[Fe^II(CN)₆]·nH₂O would be a hexagonal unit cell (space group: P6₃/m), which was the same as that of La[Fe^III(CN)₆]·5H₂O. The hydration number n = 4 was estimated by TG results for all the RE complexes. The lattice constants depended on the ionic radius of the RE³⁺ ion for the heteronuclear complexes. The single phase of the perovskite type materials was directly obtained by decomposition of the heteronuclear complexes for RE = La, Pr, Nd, Sm, and Gd. A mixture of CeO₂ and Fe₂O₃ was formed for RE = Ce because of its oxidation to Ce⁴⁺. In the case of RE = Dy, Y, Er, and Lu complexes, the perovskite type materials formed at higher temperature via. mixed oxides such as RE₂O₃ and RE₄Fe₅O₁₃ due to the small RE³⁺ ionic radius.     

STUDIES OF THE HYDROUS NIOBIUM(V) OXIDE ION EXCHANGER. VII.RATE OF THE ISOTOPIC EXCHANGE OF CESIUM IONS BETWEEN THE EXCHANGER IN THE Cs+ FORM AND AQUEOUS SOLUTION

ABSTRACT

The isotopic exchange rate of Cs⁺ between hydrous niobium(V) oxide in the Cs⁺ form and aqueous solutions was determined radiochemically. The rate was controlled by the diffusion of Cs⁺ in the exchanger particle at varying pH. The diffusion coefficients at 10°C increased with pH up to pH7; from 3.0x10^?11 m²s^?1 at pH6 to 4.0×10^?11 m²s^?1 at pH7, and became constant above pH8 (5.0x10^?11 m²s^?1). While the diffusion coefficients of Na⁺ monotonously decrease with increasing pH; from 7.9×l0^?11 m²s^?1 at pH6.5 to 2.8×l0^?11 m²s^?1 at pHll. The difference in the dependence of diffusion coefficients on pH between Cs⁺ and Na⁺ was interpreted in terms of strength of interaction between counterions and ion-exchange sites since hydrous niobium(V) oxide has selectivity higher for Cs⁺ than for Na⁺.     

Thermoelectric Properties of Ruddlesden–Popper Phase n-Type Semiconducting Oxides: La-, Nd-, and Nb-Doped Sr3Ti2O7

We report herein on Ruddlesden–Popper-type doped Sr _{n +1}Ti _n O_{3 n +1} ( n =2) as a potential candidate for n -type thermoelectric (TE) oxides. The TE properties of 5 at.% La-, Nd-, and Nb-doped Sr₃Ti₂O₇ polycrystalline ceramics were investigated and the origin of Seebeck coefficient was discussed from the viewpoint of the symmetry of TiO₆ octahedra. A significant reduction in the lattice thermal conductivity was observed by the enhancement of phonon scattering at SrO/(SrTiO₃) _n interfaces originating from the inherent superlattice structure, and the maximum dimensionless figure of merit, ZT ∼0.15, at a 1000 K value was obtained in 5 at.% La-doped Sr₃Ti₂O₇.     

Fabrication and thermoelectric properties of heavily rare-earth metal-doped SrO(SrTiO3)n (n = 1, 2) ceramics

To clarify the effect of substitutional electron doping on the thermoelectric figure of merit (ZT = S²σTκ⁻¹) of Ruddlesden–Popper phase SrO(SrTiO₃)_n (or Sr_n+1Ti_nO_3n+1), measurements were conducted for several thermoelectric parameters, e.g. electrical conductivity (σ), Seebeck coefficient (S) and thermal conductivity (κ), of (Sr_1−xRE_x)_n+1Ti_nO_3n+1 (n = 1 or 2, RE (rare earth): La or Nd, x = 0.05 and 0.1) dense ceramics prepared by a conventional solid-state reaction and hot-pressing technique. Crystal structures of the resultant ceramics were represented as (Sr_1−xRE_x)_n+1 Ti_nO_3n+1 evaluated by powder X-ray diffraction followed by the Rietveld analysis. All the ceramics exhibited electrical conductivity and the σ values simply depended on the dopant concentration, indicating that both La³⁺ and Nd³⁺ ions act as electron donors. The |S| values increased with temperature due to decrease in the chemical potential. Significant reduction of the κ values was observed as compared to cubic-perovskite SrTiO₃. The ZT value increased with temperature and reached 0.15 at 1000 K for (Sr_0.95La_0.05)₃Ti₂O₇.     

The synthesis of titanoniobate compound characteristic of various particle morphologies through a novel solvothermal route

Potassium titanoniobate (KTiNbO₅) polycrystalline powders were synthesized by the sol-gel method and a novel preparation route which was described as a combination technique of the sol-gel process and solvothermal treatment. The synthesis processes, the structure and morphology characterizations for the as-prepared KTiNbO₅ particles were investigated by using thermal analysis, X-ray powder diffraction, electron microscopy and other techniques. The KTiNbO₅ particles synthesized in this work showed various morphologies depending on the different reaction processes. The KTiNbO₅ compound obtained through 2-propanol solvothermal treatment exhibited unique particle morphology characteristic of sphere shape with the average size of 300 nm in diameter. In addition, the result that the formation of the spherical particle shape occurred during the solvothermal process was demonstrated.     

Hybrid configuration of Darrieus and Savonius rotors for stand‐alone wind turbine‐generator systems

The suitable hybrid configuration of Darrieus lift‐type and Savonius drag‐type rotors for stand‐alone wind turbine‐generator systems is discussed using our dynamic simulation model. Two types of hybrid configurations are taken up. Type A installs the Savonius rotor inside the Darrieus rotor and Type B installs the Savonius rotor outside the Darrieus rotor. The computed results of the output characteristics and the dynamic behavior of the system operated at the maximum power coefficient points show that Type A, which has fine operating behavior to wind speed changes and can be compactly designed because of a shorter rotational axis, is an effective way for stand‐alone small‐scale systems. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 150(4): 13–22, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20071     

Estrogenic activities of chemicals related to food contact plastics and rubbers tested by the yeast two-hybrid assay

Food contact plastics and rubbers possibly contain many kinds of chemicals such as monomers, oligomers, additives, degradation products of polymers and additives, and impurities. Among them, bisphenol A, nonylphenol, benzylbutyl phthalate, styrene oligomers and hydroxylated benzophenones have been reported to possess estrogenic activities. In this study, other chemicals related to food contact plastics and rubbers, and their metabolites induced by the S9-mixture were tested for their estrogenic activities using the yeast two-hybrid assay. Among the 150 chemicals, 10 chemicals such as bis(4-hydroxyphenyl) methane, 4-cyclohexylphenol, 4-phenylphenol, 4,4'-isopropylidenediphenol alkylphosphite, two type of styrenated phenol (including mono type), tris(nonylphenyl) phosphite, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone and 2,4-diphenyl-4-methyl-1-pentene, their metabolites and the metabolites of 6 other chemicals, such as 2-(phenylmethyl) phenol, styrenated phenol (di and tri type), 1-(N-phenylamino)naphthalene, 4-tert-butylphenylsalicylate, nonylphenol ethoxylates and 2-methyl-6-tert-butylphenol, displayed estrogenic activities. All of them contained a phenol group in their chemical structures or formed one easily by hydrolysis or metabolism. However, most of the chemicals related to food contact plastics and rubbers, and their metabolites did not show any estrogenicity.     

New Lanthanoid Metallofullerenes and their HPLC Elution Behavior

HPLC behaviors of metallofullerenes of 14 lanthanoid elements were studied by use of radiotracers, and the species of some of the metallofullerenes were identified by mass spectroscopy. From the HPLC elution behaviors, 14 lanthanoid elements forming metallofullerenes were found to be grouped into two, namely, Sm, Eu, Tm and Yb as one group and the rest of the elements as another. Some new species of metallofullerenes like La@C₇₄, and M@C_n (M=Eu, Tm, Yb; n=74, 82, 84, 88, 90, 92, 94) have been identified. The observed retention times of metallofullerenes are discussed in terms of the number of carbon atoms of the cage and from consideration of the electron donor and acceptor relation between the fullerene species and the HPLC stationary phases.     

Thermal conductivities of molten iron, cobalt, and nickel by laser flash method

New attempts were made for the measurement of thermal diffusivity of molten iron, cobalt, and nickel at temperatures close to 1900 K by a laser flash method. A simple but useful sample cell system was developed to keep the molten metal shape uniform for a given thickness. It is also necessary to consider the effect of not only the radiative heat loss but also the conductive heat loss at the interface between the molten metal sample and the sample cell material under the present experimental conditions. The conductive heat loss was found, through computational simulation, to be negligibly small for the present laser flash measurements. Thermal conductivity values of molten iron, cobalt, and nickel were calculated by combining the present thermal diffusivity data with specific heat and density, and the resulting values are given in the following equations (unit: W m⁻¹ K⁻¹)