Authors:Y. Ichiyanagi, T. Uehashi, S. Yamada, Y. Kanazawa, and T. Yamada
Summary Ni1-xZnxFe2O4 (0≤x≤1) mixed ferrite nanoparticles encapsulated with amorphous-SiO2 were prepared by a wet chemical method. Particle sizes were controlled to range from 2.6 to 33.7 nm by heat treatment, and the particle size dependence of saturation magnetization Ms was investigated for the x=0.5 region. The Ms value decreased abruptly for particle sizes below about 6 nm. From the temperature dependence of the magnetization under field-cooled and zero-field-cooled conditions, blocking temperatures Tb were observed to be between 28 and 245 K depending on the particle size. At the blocking temperature, the superparamagnetic spins in the particle are supposed to be blocked against the thermal fluctuation energy. A smaller particle volume causes a lower blocking temperature; so an extremely small particle would be strongly affected by thermal fluctuation.
Seawater samples were collected from the Yamato Basin and the Tsushima Basin in the Japan Sea and analyzed for their239+240Pu and137Cs concentrations. The concentration of239+240Pu was 7.4 mBq/m3 in the surface water and increased with depth to a maximum value of 38.6 mBq/m3 at 500 m at the Yamato Basin station. The subsurface maximum may be produced by scavenging of239+240Pu in surface water and release of239+240Pu from settling particles. The239+240Pu inventories in the water column were 86.6 and 85.2 Bq/m2 at the two basin stations, suggesting that 90% of239+240Pu delivered to the Japan Sea is still present in the water column.
The influences of atmospheric CO2 and H2O on the kinetics of the thermal decomposition of zinc carbonate hydroxide, Zn5(CO3)2(OH)6, were investigated by means of controlled rate evolved gas analysis (CREGA) coupled with TG. Although CO2 and H2O were evolved simultaneously in a single mass-loss step of the thermal decomposition, different effects of those evolved
gases on the kinetic rate behavior were observed. No distinguished effect of atmospheric CO2 was detected within the possible range of self-generated CO2 concentration. On the other hand, apparent acceleration effect by the increase in the concentration of atmospheric H2O was observed as the reduction of reaction temperature during the course of constant rate thermal decomposition. The catalytic
effect was characterized by the decrease in the apparent activation energy for the established reaction with increasing the
concentration of atmospheric H2O, accompanied by the partially compensating decrease in the pre-exponential factor.
Authors:R. Matsushita, M. Koyama, S. Yamada, M. Kobayashi, and H. Moriyama
In order to improve the accuracy of reactor neutron activation analysis, flux gradients and spectrum changes in the irradiation capsule have been studied at the Kyoto University Reactor (KUR). The flux and spectrum monitoring samples of Fe, Co, Au, Sb, U and Ni were placed at several positions in a polyethylene irradiation capsule of 24 mm inner diameter and 98 mm length, and were irradiated in a pneumatic irradiation facility (Pn-2). The flux gradients were found to be rather negligible in the vertical (axial) direction while they were considerable in the radial one. The flux gradient was around 5%/cm for thermal neutrons and 10%/cm for epithermal and fast neutrons. The spectrum changes were dependent on the materials (polyethylene and silica) filled in the capsule. Based on these observations, the effect of the flux gradients and spectrum changes on the accuracy of reactor neutron activation analysis was discussed.
Authors:T. Omori, Y. Yamada, S. Iino, and K. Yoshihara
Reaction mechanism of base hydrolysis of halobis/8-quinolinolato/oxotechnetium (V) /TcOX (ox)2 X=Cl and Br/ was investigated by means of solvent extraction and spectrophotometric methods. Furthermore, distribution coefficients of tris/acetylacetonato/technetium/III/, dichlorobis/8-quinolinolato/technetium/IV/ and TcOX/ox/2 between chloroform and aqueous solutions were determined. In an alkaline solution, TcOX/ox/2 decomposed to pertechnetate as a final product. On the basis of the established base hydrolysis, the respective rate constants were determined.
Authors:J. Michalik, J. Sadlo, T. Kodaira, S. Shimomura, and H. Yamada
Silver cationic clusters formed in γ-irradiated AgCs-rho zeolites in hydrated and dehydrated forms have been studied by electron
spin resonance (ESR) spectroscopy and diffuse reflectance spectrophotometry. It was found that tetrameric silver clusters,
in dehydrated zeolites and Ag
in hydrated samples, are stabilized at room temperature. Tetrameric silver is trapped inside octagonal prism of zeolite framework
and does not show any noticeable decay as far as samples are evacuated.
Authors:T. Yamada, S. Boyer, T. Iyoda, H. Yoshida, and J. Grolier
The effects of nitrogen (N2) pressure on amphiphilic di-block copolymer, PEO114-b-PMA(Az)40, were investigated by scanning transitiometry. The isotropic transition temperature increased with the increase of pressure
above 20 MPa. The hydrostatic pressure effects evaluated with the Clapeyron equation were smaller than the value obtained
by mercury as a pressurizing medium because the amount of absorbed gas decreases the volume change at the isotropic transition.
Authors:T. Yamada, S. Boyer, T. Iyoda, H. Yoshida, and J. Grolier
The effects of high pressure carbon dioxide (CO2) on the isotropic transition of three different amphiphilic di-block copolymers, PEOm-b-PMA(Az)n, namely PEO114-b-PMA(Az)40, PEO272-b-PMA(Az)46 and PEO454-b-PMA(Az)47, and on PMA(Az)30 homopolymer have been investigated by scanning transitiometry. Under CO2 pressure, the isotropic transition temperature decreased with the increase of pressure up to around 30 MPa due to CO2 sorption and increased above 40 MPa. Transition entropy of the isotropic transition indicated that the depression of the
isotropic transition temperature was caused by the adsorption of CO2 into the azobenzene moieties and that the increase above 40 MPa was caused by the desorption of CO2 into the azobenzene moieties. Comparison between PEOm-b-PMA(Az)n copolymers and PMA(Az) homopolymer clarified PEO domain acted CO2 pathway to approach the equilibrium state rapidly.
Authors:S. Y. Jung, T. Yamada, H. Yoshida, and T. Iyoda
Summary The mixing state of amphiphilic di-block copolymers consisted of poly(ethylene oxide) and poly(methacrylate) having azobenzene moieties in the side chains p(EO)114pMA(Az)24 and poly(ethylene oxide) p(EO)114 was investigated from the viewpoints of isothermal crystallization and nano-scale ordered structure. The chemical potential, which required establishing the constant crystal growth rate, decreased with the p(EO) content up to 60%. The hexagonal packed cylinder structure was observed for the blends with the p(EO) content up to 60% and the lattice spacing of (100) and (110) planes increased with the p(EO) content up to 60%. The blends of amphiphilic p(EO)114pMA(Az)24 and p(EO)114 were miscible without in the p(EO) content below 60%.