[en] This paper is a summary of the work conducted for the TOUGH2 runtime visualization in support of the modeling of the unsaturated flow regime at Yucca Mountain

[en] Electron energy loss spectra have been obtained on materials with the nominal compositions of Na_0.33CoO₂·yH₂O (y=0, 0.6, and 1.3). Spectral analysis revealed systematic changes in the low-loss energy region (<10 eV) and the core losses (O K, Co L_3,2) along with the water intercalation. The inter- (intra)band transitions and the relevant plasmon resonance were found to be sensitive to water content. Variations of the electronic structure and the Co valence states during hydration have been discussed based on our experimental results

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[en] A novel compound, tri-(4-methoxythphenyl) phosphate, was synthesized and investigated as a safety electrolyte additive for lithium-ion batteries. It was found that this additive could lower the flammability of the electrolyte, and thereby enhance the thermal stability of the Li-ion battery. Moreover, this molecule can also be polymerized at 4.35 V (vs. Li/Li⁺) to form a conducting polymer, which can protect the batteries from voltage runaway at overcharge by internal bypassing the overcharging current in the batteries. Thus, it is possible to use this electrolyte additive to provide both overcharge protection and flame retardancy for lithium-ion batteries without much influence on the battery performance

[en] Epitaxial Ba_0.5Sr_0.5TiO₃ thin films grown on the (001) LaAlO₃ substrates with a ferroelectric transition at about 250 K have been investigated by TEM and off-axis electron holography. Cross-sectional TEM observations show that the 350-nm-thick Ba_0.5Sr_0.5TiO₃ film has a sharp interface with notable misfit dislocations. Off-axis electron holographic measurements reveal that, at low temperatures, the ferroelectric polarization results in a remarkable positive potential on the interface and a negative potential on the film surface, and, at room temperature, certain charges could only accumulate at the interfacial dislocations and other defective areas

[en] The Raman spectra of the parent compound Na_xCoO₂ (x = 0.75) and the superconducting oxyhydrates Na_xCoO₂ · yH₂O with different superconducting temperatures (T_c) have been measured. Five Raman active phonons around 195 cm^-1 (E_1g), 482 cm^-1, 522 cm^-1, 616 cm^-1 (3E_2g), and 663 cm^-1 (A_1g) appear in all spectra. These spectra change systematically along with the intercalation of H₂O and superconducting properties. In particular, the Raman active phonons (A_1g and E_1g) involving the oxygen motions within the Co-O layers show up monotonous decrease in frequency along with superconducting temperature T_c. The fundamental properties and alternations of other active Raman phonons in the superconducting materials have also been discussed.

[en] The ionic conductivities of EC-based multi-component electrolytes in various solvent compositions were measured over a wide temperature range of +40 to -40 deg. C, and the factors affecting the low temperature conductivities of the electrolytes were discussed. It is revealed from the experimental results that the co-solvents with high dielectric constant and low viscosity can improve the ionic conductivity at room temperature, whereas, only the co-solvents which possess low melting points can effectively expand the operating temperature range of the electrolyte. The Li-ion batteries using the optimized electrolyte of 1M LiPF₆/EC-DMC-EMC (8.3:25:66.7) show the capacity retentions about 90.3% of their nominal capacities when discharged to 2.0V at -40 deg. C at 0.1C, demonstrating excellent low temperature performances

[en] The fine structures of the electron energy-loss spectra (EELS) for the B-K edge have been examined in NbB₂ and superconducting Nb_0.75Mg_0.25B₂. The experimental results are analyzed based on the calculations of density functional theory (DFT) using the Wien2k code. The results of the EELS spectra and the angular decomposition of the density of states (DOS) reveal that both the B p_z and B p_x+p_y states in NbB₂ have large weights at the Fermi energy due to intersheet covalent bonding with notable hybridization between the Nb 4d and B 2p states. This kind of hybridization also results in different core-hole behaviors for the B-K edge in two orthogonal crystallographic orientations. The best fit between experimental and theoretical data is achieved with consideration of the core-hole effect of the B 1 s states, in particular for the q-perpendicular c spectra. Analysis of the electronic structure of the Nb_1-xMg_xB₂ superconductors suggests that confinement of the intersheet covalent bonding is likely to be favorable for the improvement of superconductivity in this kind of materials

[en] Transmission electron microscopy (TEM) investigations on Nd_2/3-xLi_3xTiO₃ with x=0.14 reveal a rich variety of structural features in the samples prepared under different conditions, such as superstructures, anti-phase domains, and nano-chessboard structures. Our careful analysis shows that these structural phenomena can be fundamentally understood as the combination of structural effects of (Nd, Li)-ordering along the <001>_p direction and the spinodal decomposition along the <100>_p/<010>_p direction. The coexistence of phase separation and cation ordering can lead to visible nano-structural complexities in many crystals, as the typical results, the regular lamella structure, nano-chessboard structures and anti-phase boundaries have been extensively studied. - Graphical abstract: Transmission electron microscopy investigations on Nd_2/3-xLi_3xTiO₃ with x=0.14 reveal a rich variety of structural features in the samples prepared under different conditions, such as superstructures, anti-phase domains, one-dimensional lamella structure, nano-chessboard structures and circle-like pattern

[en] We prepared the metastable T'-phase La_2-xLn_xCuO₄ (Ln = Sm and Y) cuprates by a coprecipitation technology, which cannot be acquired by conventional solid-state reaction. The selective stabilization of T'- and T-phase was studied via altering synthesis temperature and pressure. The structural phase diagram for T- and T'-phase is obtained in La_2-xLn_xCuO₄ system. All these samples show semiconducting behavior, and no superconductivity was observed down to 2 K even after reduction. Magnetic measurement shows a Curie-Weiss-like paramagnetic behavior