Structural modification of Li[Li0.27Co0.20Mn0.53]O2 by lithium extraction and its electrochemical property as the positive electrode for Li-ion batteries

In our previous report, we have synthesized Li₂MnO₃-LiCoO₂ solid solutions and have investigated electrochemical properties [J.-M. Kim, T. Sho, N. Kumagai, Electrochem. Commun. 9 (2007) 103]. These materials have showed a long charge plateau at above 4.5 V during the first charge, which disappears with the subsequent cycles. This phenomenon is usually observed in Li₂MnO₃ and Li₂MnO₃-LiMeO₂ system (Me = Ni_1/2Mn_1/2 [Z. Lu, D.D. MacNeil, J.R. Dahn, Electrochem. Solid State Lett. 4 (2001) 191], Co [K. Numata, C. Sakaki, S. Yamanaka, Solid State Ionics 117 (1999) 257; Y.J. Park, Y.-S. Hong, X. Wu, M.K. Kim, K.S. Ryu, S.H. Chang, J. Electrochem. Soc. 151 (2004) A720], Fe [M. Tabuchi, A. Nakashima, H. Shigemura, K. Ado, H. Kobayashi, H. Sakaebe, H. Kageyama, T. Nakamura, M. Kohzaki, A. Hirano, R. Kanno, J. Electrochem. Soc. 149 (2002) A509], or Cr [B. Ammundsen, J. Paulsen, Adv. Mater. 13 (2001) 943]). In this study, we investigate the relationship between the first lithium extraction process and the electrochemical property of the synthesized Li[Li_0.27Co_0.2Mn_0.53]O₂ material. The crystal structure and electrochemical performance of the synthesized Li[Li_0.27Co_0.20Mn_0.53]O₂ are modified by the Li⁺ extraction.     

Neutron shielding material based on colemanite and epoxy resin

In recent years, there has been a need for compact shielding design such as self-shielding of a PET cyclotron or upgradation of radiation machinery in existing facilities. In these cases, high performance shielding materials are needed. Concrete or polyethylene have been used for a neutron shield. However, for compact shielding, they fall short in terms of performance or durability. Therefore, a new type of neutron shielding material based on epoxy resin and colemanite has been developed. Slab attenuation experiments up to 40 cm for the new shielding material were carried out using a 252Cf neutron source. Measurement was carried out using a REM-counter, and compared with calculation. The results show that the shielding performance is better than concrete and polyethylene mixed with 10 wt% boron oxide. From the result, we confirmed that the performance of the new material is suitable for practical use.     

Qualitative map learning based on covisibility of objects.

Autonomous map construction is one of the most fundamental and significant issues in intelligent mobile robot research. While a variety of map construction methods have been proposed, most require some quantitative measurements of the environment and a mechanism of precise self-localization. This paper proposes a novel map construction method using only qualitative information about "how often two objects are observed simultaneously." This method is based on heuristics--"closely located objects are likely to be seen simultaneously more often than distant objects" and a well-known multivariate data analysis technique-multidimensional scaling. A significant feature of this method is that it requires neither quantitative sensor measurements nor information about the robot's own position. Simulation and experimental results demonstrated that this method is sufficiently practical for capturing a qualitative spatial relationship among identifiable landmark objects rapidly.     

Thermal and fluid mechanical problems in space flight

In this paper the basic research activities being carried out in the Institute of Space and Aeronautical Sciences, University of Tokyo and other establishments have been discussed. Four problems of space flight, namely, thermal design of spacecraft, thermal protection during. planetary entry, surface contamination of spacecraft and microgravity effects in space have been specifically highlighted.     

Polyolefins containing 1,3‐disubstituted cyclopentane units as nucleating agents for isotactic polypropylene

Polyolefins containing 1,3‐disubstituted cyclopentane units in the main chain have been synthesized by 1,3‐polymerization of cyclopentene (PCP), cyclization polymerization of 1,5‐hexadiene (PHD), and ring‐opening metathesis polymerization of norbornene following hydrogenation of the unsaturated main chain (H‐PNB) with various transition metal catalysts. These polyolefins were applied to nucleating agents for isotactic polypropylene, and relationship between the structure of the polyolefins and nucleating effect was studied by DSC, polarized optical microscope, and WAXD. All the polyolefins had an effect of nucleation for isotactic polypropylene (PP). Of the polymeric nucleating agents, H‐PNB showed the most effective nucleation. Addition of PCP, which was obtained with a nickel catalyst with diimine ligand, to PP induced β‐modification. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2953–2958, 2006     

Controlled growth and shape formation of platinum nanoparticles and their electrochemical properties

Cubic Pt nanoparticles were prepared from a solution of K₂PtCl₄ containing sodium polyacrylate as a capping reagent. The effects of the Pt/polymer molar ratio, the average molecular weight (M_w) of the polymer, and reaction temperature on the shape and size were investigated. When the polymer of M_w = 5100 was added at a molar ratio of Pt/polymer = 1/12, cubic platinum nanoparticles of an average size of 10.3 nm were predominantly formed (ca. 50% in number) at 25 °C. The electron diffraction pattern of the cubic nanoparticles revealed that they are single crystals with Pt {1 0 0} faces on the surface.The cubic nanoparticles were electrochemically active, and showed strong features of Pt {1 0 0} faces on cyclic voltammogram under argon atmosphere. After repeated potential cycling in the range 0.05-1.4 V, the features of Pt {1 0 0} were gradually lost, and changed to those of polycrystalline Pt. Rotating ring disk electrode measurements in O₂-saturated H₂SO₄ solution revealed that the cubic nanoparticles had a high catalytic activity for oxygen reduction reaction (ORR). After polycrystallization by repeated potential cycling, the activity for ORR and hydrogen peroxide formation decreased slightly, which were attributed to the surface structural change from Pt {1 0 0} to polycrystalline.     

Biodegradation and fish toxicity of nonionic surfactants

In order to investigate the fate and toxicity to fish of nonionic surfactants in the environment, biodegradation tests of river sediments and river water were carried out. In the biodegradation test of river sediments, residual surfactants in the water phase and sediments were analyzed by the colorimetric cobalt-thiocyanate method (CTAS) and high performance liquid chromatography (HPLC) with a fluorimetric detector. Two kinds of nonionic surfactants, polyoxyethylene nonylphenol ether (C₉APE₉) and polyoxyethylene alcohol ether (C₁₂AE₇), were degraded by river sediments under both stirring and standing conditions, detected by CTAS and HPLC measurements. There was little difference between the time-course of both surfactants measured by CTAS and HPLC in the water phase. Although the adsorption of both surfactants on sediments was low, most of both surfactants adsorbed on sediments were biodegraded during the test period. Nonylphenolmonoethoxy acetate (Met 2) and nonylphenolacetate (Met 1) were identified as biodegradation intermediates using preparative HPLC and mass spectrometric analysis. In the river die-away test of C₉APF₉, the reduction of toxicity to fish of C₉APE₉ was observed in the course of biodegradation (after 10 days). LC₅₀ of primary biodegradation intermediates, Met 1 and 2, was almost at the same level as that of C₉APE₉. This result suggests that the reduction of toxicity to fish is due to further biodegradation of C₉APE₉ through Met 1 and 2.     

The reduction of pressure drop due to dust loading in a conventional cyclone

Experiments have been conducted to examine the effect of dust loading on pressure drop in a conventional cyclone. The presence of dust in the air stream reduced the cyclone pressure drop by as much as 30%, even at extremely low concentrations, such as 0.2 g/m³. In the range of 1.5–50 g/m³, the pressure drop ratio (the ratio of the pressure drop of dusty air to that of pure air with the same inlet velocity) was independent of dust concentration, and kept nearly constant; but it decreased as the concentration increased above 50g/m³. It was observed that the presence of dust reduced the tangential velocity. However the radii of a cross section of the cyclone, where the pressures are equal to those of the entrance and the exit, did not change noticeably. Calculating the pressure drop by integrating the term due to centrifugal force is also examined.