The search for new materials that could improve the energy density of Li-ion batteries is one of today's most challenging issues. Many families of transition metal oxides as well as transition metal ...polyanionic frameworks have been proposed during the past twenty years. Among them, manganese oxides, such as the LiMn2O4 spinel or the overlithiated oxide LiLi1/3Mn2/3O2, have been intensively studied owing to the low toxicity of manganese-based materials and the high redox potential of the Mn(3+)/Mn(4+) couple. In this work, we report on a new electrochemically active compound with the 'Li4Mn2O5' composition, prepared by direct mechanochemical synthesis at room temperature. This rock-salt-type nanostructured material shows a discharge capacity of 355 mAh g(-1), which is the highest yet reported among the known lithium manganese oxide electrode materials. According to the magnetic measurements, this exceptional capacity results from the electrochemical activity of the Mn(3+)/Mn(4+) and O(2-)/O(-) redox couples, and, importantly, of the Mn(4+)/Mn(5+) couple also.
Silicon dominates the electronics industry, but its poor optical properties mean that III-V compound semiconductors are preferred for photonics applications. Photoluminescence at visible wavelengths ...was observed from porous Si at room temperature in 1990, but the origin of these photons (do they arise from highly localized defect states or quantum confinement effects?) has been the subject of intense debate ever since. Attention has subsequently shifted from porous Si to Si nanocrystals, but the same fundamental question about the origin of the photoluminescence has remained. Here we show, based on measurements in high magnetic fields, that defects are the dominant source of light from Si nanocrystals. Moreover, we show that it is possible to control the origin of the photoluminescence in a single sample: passivation with hydrogen removes the defects, resulting in photoluminescence from quantum-confined states, but subsequent ultraviolet illumination reintroduces the defects, making them the origin of the light again.
The magnetic properties of manganile bilayers composed of G-type antiferromagnetic (AFM) SrMnO sub(3) and double-exchange ferromagnetic (FM) La sub(0.7) Sr sub(0.3) MnO sub(3) are studied. A ...spin-glass state is observed as a result of competing magnetic orders and spin frustration at the La sub(0.7) Sr sub(0.3) MnO sub(3)/SrMnO sub(3) interface. The dependence of the irreversible temperature on the cooling magnetic field follows the Almeida-Thouless line. Although an ideal G-type AFM SrMnO sub(3) is featured with a compensated spin configuration, the bilayers exhibit exchange bias below the spin glass freezing temperature, which is much lower than the Neel temperature of SMO, indicating that the exchange bias is strongly correlated with the spin glass state. The results indicate that the spin frustration that originates from the competition between the AFM super-exchange and the FM double-exchange interactions can induce a strong magnetic anisotropy at the La sub(0.7) Sr sub(0.3) MnO sub(3)/SrMnO sub(3) interface.
•Role of high Bi-content on magnetic properties of La2MnCoO6 is investigated.•Both the ferromagnetic TC and magnetization decrease with increase in Bi-content.•Ferromagnetic Mn4+—O—Co2+ superexchange ...becomes weaker in Bi-content phases.•Evolution of Mn3+—O—Co3+ vibronic ferromagnetism of smaller exchange stabilization.•Stereoactive 6s2-electrons of Bi3+ facilitate to stabilize vibronic ferromagnetism.
The crucial role of high Bi-content on magnetic properties of ambient pressure synthesized double perovskite La2−xBixMnCoO6 (x = 0, 0.5 and 1) has been investigated. Structural characterization was carried out using X-ray and electron diffraction analyses as well as HAADF-STEM imaging, which confirm the monoclinic structure with P21/n space group for all compositions. A comprehensive dc-magnetization and ac-susceptibility studies unravel the complex magnetic features of parent La2MnCoO6 and its associated changes upon substitution of La by Bi. Both the ferromagnetic TC and reduced magnetization with increase in Bi-content, originated from weakening of ordered Mn4+—O—Co2+ superexchange interactions. Bi-substitution also leads to suppression in magnetic disordering, which should strengthen the ferromagnetic state. These antagonist effects i.e. suppression of disordering and lowering of TC can be related to the evolution of Mn3+—O—Co3+ (e1—O—e1) vibronic ferromagnetism of smaller exchange stabilization. The local lattice distortion due to stereoactive 6s2-electron pairs of Bi3+ possibly results in cooperative lattice distortion favouring the stabilization of Jahn-Teller active intermediate-spin state Co3+ and high spin Mn3+. It is suggested that Bi-substitution favours the reaction Co2+ + Mn4+ = Co3+ + Mn3+ to the right side, which is otherwise biased to left by 0.2 eV.
Abstract
Determination of the ship’s course width necessary for the ships safe operation is an urgent task due to the increase in the modern ships’ dimensions. The existing methods for assessing the ...fairway are calculated with a full re-positioning of the propulsion-rudder complex, according to the maximum drift angle. The vessel movement is considered to be steady, that is, the speed, the drift angles do not depend on time. The relevance of this study is associated with the assessment of determining the width of the fairway at any time interval. This is due to the fact that when passing the river sections, the vessels perform maneuvering with the rudder gear shifted for short periods of time and not at the maximum shift angle. Determination of the parameters of the ship’s movement over time when the navigator manipulates the ship’s controls (control of the rudder device, changing the parameters of the main engines) can be determined by the mathematical model of the ship’s movement. This article discusses the issues of creating a model that adequately describe the processes of vessel movement, including in the conditions of vessel movement along a limited ship’s course. The adequacy of the model was verified using the data of field and model experiments. According to the compiled mathematical model, the calculations were made for various projects of dry cargo ships.
Order-disorder-order phase transitions in the clathrate-I Ba8Cu16P30 were induced and controlled by aliovalent substitutions of Zn into the framework. Unaltered Ba8Cu16P30 crystallizes in an ordered ...orthorhombic (Pbcn) clathrate-I superstructure that maintains complete segregation of metal and phosphorus atoms over 23 different crystallographic positions in the clathrate framework. The driving force for the formation of this Pbcn superstructure is the avoidance of Cu-Cu bonds. This superstructure is preserved upon aliovalent substitution of Zn for Cu in Ba8Cu16-xZnxP30 with 0 < x < 1.6 (10% Zn/Mtotal), but vanishes at greater substitution concentrations. Higher Zn concentrations (up to 35% Zn/Mtotal) resulted in the additional substitution of Zn for P in Ba8M16+yP30-y (M = Cu, Zn) with 0 less than or equal to y less than or equal to 1. This causes the formation of Cu-Zn bonds in the framework, leading to a collapse of the orthorhombic superstructure into the more common cubic subcell of clathrate-I (Pm3&cmb.macr; n). In the resulting cubic phases, each clathrate framework position is jointly occupied by three different elements: Cu, Zn, and P. Detailed structural characterization of the Ba-Cu-Zn-P clathrates-I via single crystal X-ray diffraction, joint synchrotron X-ray and neutron powder diffractions, pair distribution function analysis, electron diffraction and high-resolution electron microscopy, along with elemental analysis, indicates that local ordering is present in the cubic clathrate framework, suggesting the evolution of Cu-Zn bonds. For the compounds with the highest Zn content, a disorder-order transformation is detected due to the formation of another superstructure with trigonal symmetry and Cu-Zn bonds in the clathrate-I framework. It is shown that small changes in the composition, synthesis, and crystal structure have significant impacts on the structural and transport properties of Zn-substituted Ba8Cu16P30.
Although good progress was made by two international benchmark exercises on in-plane permeability, existing methods have not yet been standardized. This paper presents the results of a third ...benchmark exercise using in-plane permeability measurement, based on systems applying the radial unsaturated injection method. 19 participants using 20 systems characterized a non-crimp and a woven fabric at three different fiber volume contents, using a commercially available silicone oil as impregnating fluid. They followed a detailed characterization procedure and also completed a questionnaire on their set-up and analysis methods. Excluding outliers (2 of 20), the average coefficient of variation (cv) between the participant’s results was 32% and 44% (non-crimp and woven fabric), while the average cv for individual participants was 8% and 12%, respectively. This indicates statistically significant variations between the measurement systems. Cavity deformation was identified as a major influence, besides fluid pressure/viscosity measurement, textile variations, and data analysis.
Abstract
The most common and reliable method of protecting a ship’s hull from corrosion is paint coatings. Paint coatings can be used to paint products of any size. In case of complete or partial ...destruction, the paintwork can be easily restored by tinting or completely repainting the surface. Paints and varnishes are easily combined with other methods of corrosion protection. The use of paint coatings is more economical in comparison with other types of corrosion protection. Therefore, it is currently the most common method of protecting ship hulls. In order to determine the quality, the experimental studies of various paints and varnishes were carried out. Experimental prototypes were made. The effect of low temperatures and the effect of an impending water flow on paint and coatings were considered. The main conclusions were drawn from the results of the experiments. For long-term protection from the external environment, it is necessary that the coating film should maintain high adhesion to the surface maintain continuous, have minimal water absorption, devoid of pores and be solid. Samples with a two-layer and three-layer coating of Jotun paint have the best adhesion. Satisfactory results were also obtained on samples with a three-layer coating of XC-436 enamel and with a two-layer coating of stone red.
Riboflavin (Rf) is a vitamin and endogenous photosensitizer capable to generate reactive oxygen species (ROS) under UV-blue irradiation and kill cancer cells, which are characterized by the enhanced ...uptake of Rf. We confirmed its phototoxicity on human breast adenocarcinoma cells SK-BR-3 preincubated with 30-μM Rf and irradiated with ultraviolet light, and proved that such Rf concentrations (60 μM) are attainable in vivo in tumour site by systemic intravascular injection. In order to extend the Rf photosensitization depth in cancer tissue to 6 mm in depth, we purpose-designed core/shell upconversion nanoparticles (UCNPs, NaYF
:Yb
:Tm
/NaYF
) capable to convert 2% of the deeply-penetrating excitation at 975 nm to ultraviolet-blue power. This power was expended to photosensitise Rf and kill SK-BR-3 cells preincubated with UCNPs and Rf, where the UCNP-Rf energy transfer was photon-mediated with ~14% Förster process contribution. SK-BR-3 xenograft regression in mice was observed for 50 days, following the Rf-UCNPs peritumoural injection and near-infrared light photodynamic treatment of the lesions.
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