[en] Partial substitution of Mn in lithium manganese oxide spinel materials by Cu and Ni greatly affects the electrochemistry and the cycle life characteristics of the cathode. Substitution with either metal or a combination of both metals in the spinel lattice structure reduces the 3.9-4.2 V potential plateaus associated with the conversion of Mn³⁺ to Mn⁴⁺. Higher potential plateau associated with oxidation of the substituted transition elements is also observed. These substituents also significantly alter the onset of Jahn-Teller distortions in the 3 V potential plateau. Synchrotron based in situ X-ray absorption (XAS) was used to determine the exact nature of the oxidation state changes in order to explain the overall observed capacities at different potential plateaus. The studies on LiCu_0.5Mn_1.5O₄ show single phase behavior in the 4-5 V potential region with a good cycle life. Lower cycle life characteristic observed in cycling LiNi_0.5Mn_1.5O₄ and LiNi_0.25Cu_0.25Mn_1.5O₄ versus Li metal are ascribed to coexistence of several phases in this potential region. However, LiCu_0.5Mn_1.5O₄ shows onset of Jahn-Teller distortions in the 3 V potential plateau, in contrast to LiNi_0.5Mn_1.5O₄ and LiNi_0.25Cu_0.25Mn_1.5O₄ cathode materials

[en] An integrated oil spill model for microcomputers is developed for simulating fate and transport of spilled oil in rivers. This model can simulate the oil slick transformation in transient flow conditions with varying wind and air temperature. This paper reports on the model which consists of fixed data files, and execution of all modules; an unsteady flow model to simulate the flow conditions along the river as a function of time; a two-dimensional two layer model that can simulate advection, horizontal diffusion, spreading, evaporation, dissolution, vertical mixing, emulsification, and shoreline deposition; a graphics interface for visualizing the results from the oil spill model

[en] We have measured the XAFS spectra of tin-based composite oxide (TCO) glass with nominal composition of Sn_1.0B_0.56P_0.40Al_0.42O₃ during the discharge and charge cycles in a non-aqueous cell. Our results confirm the amorphous nature of TCO material and show that Sn in TCO is coordinated with 3 oxygen atoms at a distance of 2.12 Angstrom. Upon discharge (i.e., Li insertion), initially, Li interacts with the electrochemically active Sn-O center forming metallic Sn, most likely in the form of highly dispersed clusters, and Li₂O. Upon further discharge, our results are consistent with a model in which additional Li alloys with Sn forming various alloys with composition dependent on the amount of Li inserted. The formed alloys appear to be in the form of highly dispersed clusters and/or amorphous in nature. Their local structure differs somewhat from the crystalline structure of the known Li-Sn alloys such as LiSn, Li₇Sn₃, or Li₇Sn₂. Upon charging (i.e., Li removal), metallic Sn is reversibly produced with a Sn-Sn distance intermediate to those of gray and white Sn. (au)

[en] Highlights: • Fast water phase transitions appear in a tandem carbon nanotube. • The occupancy and transfer rate of water molecules can be tuned by the transverse electric field. Due to the electric shielding effect, achieving water wet-dry phase transitions in a one-dimensional (1D) CNT is difficult. In this article, water properties in the tandem carbon nanotubes (TCNTs) are studied and discussed with molecular dynamics simulations. Compared with water molecules in a single CNT, water molecules in the TCNT can achieve fast wet-dry phase transitions under the transverse electric field. Water occupancy in the TCNT increases with the increase of the nanojunction under no or a weak electric field. However, water occupancy in the TCNT decreases with the increase of the nanojunction under a strong electric field. With increasing the electric field, the transfer rate through the TCNT with a large nanojunction decreases sharply, while the transfer rate through the TCNT with a small nanojunction changes slightly. The interaction between water molecules and the TCNT is adopted to explain the fast wet-dry phase transitions under the transverse electric field.

[en] Highlights: ► The second ICRF antenna of EAST is capable of coupling higher power than the former ICRF antenna due to it has been designed with four current straps. ► Many cooling channels have been designed for the key components of faraday shied, current strap, baffles and transmission lines, which can remove the dissipated RF loss power and incoming heat loads on them and make ICRF antenna being capable of coupling higher power in constant wave operation. ► Extra structure via cantilever support beam has been designed to support the forepart of the ICRF antenna. ► Numerical analysis by applying the thermo-mechanical coupling method have been applied to analyze for the key components of ICRF antenna. - Abstract: In order to satisfy the requirements of heating plasma on EAST project, 3 MW ion cyclotron range of frequency (ICRF) heating system will be available at the second stage. Based on this requirement, the second ICRF antenna, has been designed for EAST. The antenna which is planned to operate with a frequency ranging from 30 MHz to 110 MHz, comprises four poloidal current straps. The antenna has many cooling channels inside the current straps, faraday shield and baffle to remove the dissipated RF loss power and incoming plasma heat loads. The antenna is supported via a cantilever support box to the external support structure. Its assembly is plugged in the port and fixed on the support box. External slideway and bellows allow the antenna to be able to move in the radial direction. The key components of the second ICRF antenna has been designed together with structural and thermal analysis presented.

No abstract available

[en] A Synchrotron x-ray source was used for In Situ x-ray diffraction studies during charge on a new LiMg_0.125Ti_0.125Ni_0.75 cathode material synthesized by FMC Corp. It had been demonstrated by Gao that this new material has superior thermal stability than LiNiO₂ and LiCo_0.2Ni_0.8O₂ at over-charged state. In this current paper, studies on the relationship between the structural changes and thermal stability at over-charged state for these materials are presented. For the first time, the thermal stability of these materials are related to their structural changes during charge, especially to the formation and lattice constant change of a hexagonal phase (H3). The spectral evidence support the hypothesis that the improvement of thermal stability is obtained by suppressing the formation of H3 phase and reducing the shrinkage of its lattice constant c when charged above 4.3 V

[en] Hard x rays from a synchrotron source were utilized in diffraction experiments which probed the bulk of electrode materials while they were operating in situ in battery cells. Two technologically relevant electrode materials were examined; an AB₂-type anode in a nickel endash metal endash hydride cell and a LiMn₂O₄ cathode in a Li-ion open-quote open-quote rocking chair close-quote close-quote cell. Structural features such as lattice expansions and contractions, phase transitions, and the formation of multiple phases were easily observed as either hydrogen or lithium was electrochemically intercalated in and out of the electrode materials. The relevance of this technique for future studies of battery electrode materials is discussed. copyright 1996 American Institute of Physics

[en] Raman spectroscopy, FTIR and scanning tunneling microscopy (STM) were used to study diamond-like nanocomposite (DLN) and metal containing DLN (Me-DLN) films. The FTIR spectra showed no appreciable absorption from the C-H stretch vibration band in DLN when 1 kV rf bias voltage was applied. Thermal annealing (450 degrees C for 2 hrs) of (a) DLN and Cr-DLN films caused no change in the Raman spectra while (b) for Pt-DLN films there was a blue shift of both the crystalline (G) and microcrystalline (D) graphite-like features, an increase in the I_D/I_G intensity ratio and a decrease in the linewidths. The changes observed were more pronounced in the film with the highest Pt concentration. The STM image of this Pt-DLN film revealed a structure of aromatic graphite rings

[en] Perovskites of the composition La_1-xSr_xFeO_3-δ (x = 0.0, 0.1, 0.5, 0.9, 1.0) were prepared by the conventional solid state reaction route. The single phase behaviour was assessed by XRD analysis, the electronic properties were investigated by Fe K-edge X-ray absorption spectroscopy. The work is focused on the valence state of iron and the oxygen vacancies of the perovskites investigated. The XRD measurements revealed that the solid state reaction yields cubic perovskites for x = 1, 0.9, rhombohedral perovskites for x = 0.5, and orthorhombic perovskites for x = 0, 0.1. The X-ray absorption data are discussed in detail with respect to Fe K-edge shift, white-line intensity, pre-edge features, and the EXAFS data. The first peak in the Fourier transform of the Chi x k³ and Chi x k² functions was simulated for a detailed analysis of scattering contributions from the first oxygen shell to evaluate the Fe-O bond length. The substitution of lanthanum by strontium leads to a corresponding increase of the iron valence state and thus to the formation of the Jahn-Teller Fe⁴⁺ ion. This is causing disorder in the first coordination shell and thus an increase of the Debye-Waller factor with increasing x. The Fe-O bond length obtained from XRD and especially from X-ray absorption data are consistent with δ-values close to zero.