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[en] Purpose: To measure the radiation permeation rate of a reprocessing process solution with respect to a plurality kinds of radiation-ray energy thereby measuring the concentration of uranium and plutonium at the same time. Constitution: The measuring device comprises a measuring mechanism for radiation ray permeation rate including a solution measuring section for containing a solution to be measured, a disc attached with two radiation sources (for example, Am-241, Co-57) and a detector for detecting gamma-rays from the radiation sources which are opposed on both sides thereof, as well as a density calculation mechanism to which the signal from the detector is inputted. Since the thickness of the solution measuring section and the mass absorption coefficient of gamma-rays from the radiation sources are known, in the case of measuring the reprocessing process solution mostly composed of uranium and plutonium, concentrations of uranium and plutonium can be calculated by measuring the radiation ray permeation rates of the two kinds of radiation ray sources. The object for the density measurement and the nuclides of the radiation sources are not restricted only to those described above. (Kawakami, Y.)
[en] The copper-based polyanion compounds Li_6CuB_4O_1_0 and Li_2CuP_2O_7 were synthesized using a conventional solid-state reaction, and their electrochemical properties were determined. Li_6CuB_4O_1_0 showed reversible capacity of 340 mA g"−"1 at the first discharge–charge process, while Li_2CuP_2O_7 showed large irreversible capacity and thus low charge capacity. Ex situ X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES) measurements revealed that the electrochemical Li"+ intercalation/deintercalation reaction in Li_6CuB_4O_1_0 occurred via reversible Cu"2"+/Cu"+ reduction/oxidation reaction. These differences in their discharge/charge mechanisms are discussed based on the strength of the Cu–O covalency via their inductive effects. - Graphical abstract: Electrochemical properties for Cu-based polyanion compounds were investigated. The electrochemical reaction mechanisms are strongly affected by their Cu–O covalentcy. - Highlights: • Electrochemical properties of Cu-based polyanion compounds were investigated. • The Li"+ intercalation/deintercalation reaction progressed in Li_6CuB_4O_1_0. • The electrochemical displacement reaction progressed in Li_2CuP_2O_7. • The strength of Cu–O covalency affects the reaction mechanism.
[en] Highlights: ► 40-nm-sized O3-LiFeO2 exhibits higher discharge capacities and rate characteristics than 400-nm-sized O3-LiFeO2. ► The cation disorder of Li and Fe ions might have affected the electrochemical activity of the O3-LiFeO2 nanoparticles. ► A phase change from a layered structure to a cubic structure during electrochemical cycling. ► The new cubic phase allowed a stable electrochemical reaction between 4.5 and 1.0 V. -- Abstract: Layered rocksalt-type LiFeO2 particles (O3-LiFeO2) with average particle sizes of ca. 40 and 400 nm were synthesized by an ion exchange reaction from α-NaFeO2 precursors. X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images confirmed the formation of nanosized O3-LiFeO2. 40-nm LiFeO2 exhibited a higher discharge capacity (115 mAh g−1) than 400-nm LiFeO2 (80 mAh g−1), and also had better rate characteristics. The downsizing effect and cation disorder between the lithium and iron layers may have improved the electrochemical activity of the LiFeO2 particles. Transmission electron microscopy (TEM) observation indicated a phase transition from O3-LiFeO2 to a cubic lattice system during the electrochemical process. The cubic lithium iron oxide exhibited stable electrochemical reactions based on the Fe2+/Fe3+ and Fe2+/Fe0 redox couples at voltages between 4.5 and 1.0 V. The discharge capacities of 40-nm LiFeO2 were ca. 115, 210, and 390 mAh g−1 under cutoff voltages of 4.5–2.0 V, 4.5–1.5 V, and 4.5–1.0 V, respectively.
[en] The electrode surface of a lithium battery was characterized using in situ reflectivity techniques and epitaxial thin films. Epitaxial LiFePO4 thin films were fabricated by pulsed laser deposition. Changes in interfacial structures on the surface are determined by X-ray and neutron reflectivity (NR) measurements using an X-ray-transmission electrochemical cell. The LiFePO4 surface is stable during the first charge/discharge process. NR analysis indicates a reversible change in the concentration gradient of lithium ions at the LiFePO4/electrolyte interface on lithium de-intercalation. (author)
[en] The electrochemical properties of lithium manganese hydroxyphosphate, LiMnPO4(OH), with the tavorite structure have been investigated to assess its suitability as a cathode material for lithium batteries. Stoichiometric LiMnPO4(OH) was synthesized by an ion-exchange reaction with MnPO4·H2O and LiNO3. Lithium (de)intercalation reaction was observed for the first time in the trivalent LiMnPO4(OH), and it exhibited a reversible capacity of 110 mA h g−1 with an average cell voltage of 3.4 V (vs. Li) after an irreversible phase change during the first charge process. The crystal structure has been refined at room temperature by neutron and synchrotron X-ray diffraction data using Rietveld method with a space group of P−1. The hydroxy group at a bottleneck may reduce the attraction force between lithium and the bottleneck oxygen ions that thus increase the ion mobility along the lithium diffusion tunnel. - Graphical abstract: Tavorite-type material LiMnPO4(OH) shows lithium intercalation at an average voltage of 3.4 V (vs. Li) after a phase transition during the first charge–discharge. Highlights: ► Tavorite-type LiMnPO4(OH) nanoparticles as a cathode material for lithium battery. ► Synchrotron XRD and neutron diffraction refinement of LiMnPO4(OH). ► Lithium intercalation reaction occurs in LiMnPO4(OH) during charge–discharge. ► A phase transition in the first charge, followed by a reversible reaction.
[en] Eu-doped pyrochlores, La2M2O7 (M=Zr, Hf, Sn), were synthesized by solid-state reaction at a temperature range of 1473 and 1673 K, and their structures and optical properties were characterized by X-ray Rietveld analysis, field emission scanning electron microscope (FE-SEM), and photoluminescent spectroscopy. The Rietveld analysis indicated that the distortion of the (EuO8)n- scalenohedra increased with decreasing ionic radii of the M4+ ion, and the crystallinity increased with the sintering temperature. The splitting width of 5D0-7F1 transition of Eu3+ ions increased with the distortion of the (EuO8)n- scalenohedra. The luminescent intensity ratio of magnetic dipole transitions to electronic dipole transitions decreased with the crystallinity, and the chromaticity changed from deep-red to orange-red. The relationship between the chromaticity of phosphors and the crystallinity was clarified, and the control of crystallinity is an important factor that provides phosphors with required chromaticity