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[en] Recent experiments have demonstrated that valence band dispersion may be observed on suitably prepared surfaces of quasicrystals. We present model calculations for optical transitions for one-dimensional a periodic lattices, and show that these calculations are consistent with the experimental photoemission results. We estimate the total number of bands which can be observed in such an experiment is reduced from infinite, to just two to three bands in a typical experiment

[en] The crystallographic and electronic structure of UFe2Al10 was studied as a function of pressure by combining X-ray diffraction results with the full potential linearized augmented plane wave (LAPW) calculations method. The volume-pressure reduction measured at 23.5 GPa is V/V0 = 0.87, with a B0 value of 132 ± 8 GPa. The uranium 5f electrons in this compound are located in a narrow and well-defined band above EFermi, having a very weak interaction with the iron 3d band located below EFermi. Consequently, the DOS at EFermi is close to zero, indicating a close to zero-magnetic moment of the uranium atom at low temperature up to a pressure of 23.5 GPa, as expected from the layered crystallographic structure of this compound. The above assumption is supported by preliminary neutron diffraction data, where no long-range magnetic order was detected down to 3 K.

[en] The morphological and electrical properties of Ba_1-xSr_xCe_0.8Y_0.2O_3-δ with x varying from 0 to 1 prepared by a modified Pechini method were investigated as potential high temperature proton conductors. Dense microstructures were achieved for all the samples upon sintering at 1500 C for 5 h. The phase structure analysis indicated that perovskite phase was formed for 0 (le) x (le) 0.2, while for x larger than 0.5, impurity phases of Sr₂CeO₄ and Y₂O₃ appeared. The tolerance to H₂O for the samples improved with the increase in Sr content when exposed to boiling water, while the electrical conductivity decreased from x = 0 to 1. However, the resistance to CO₂ attack at elevated temperatures was not improved within the whole x range studied.

[en] In order to elucidate the role of total strain and strain rate during high pressure torsion of Al₈₅Ce₈Ni₅Co₂ metallic glass, different deformation conditions were applied to devitrify the as-quenched alloy. The disk-shaped specimens were characterized by X-ray diffraction, transmission electron microscopy and thermal analysis.

[en] It has been demonstrated that high magnetic field is a very powerful tool in controlling microstructures of materials. In this work, the effect of high magnetic field on the crystallization of Zr_46.75Ti_8.25Cu_7.5Ni₁₀Be_27.5 bulk metallic glass has been investigated. The isothermal crystallization of the bulk metallic glass was performed at the temperatures ranging from 643 to 713 K with or without a high magnetic field. The direction of the magnetic field is parallel or perpendicular to the sample surfaces. The annealed samples were characterized by X-ray diffraction and differential scanning calorimeter. It has been found that the crystallization of the bulk metallic glasses depends not only on the annealing temperatures, but also on the direction and the intensity of the high magnetic field. The high magnetic field significantly retards the crystallization of the bulk metallic glass at certain annealing temperatures. The possible mechanisms of high magnetic field effect on the crystallization have been discussed.

[en] This study employs a direct synthesis method to prepare alumina/water (Al₂O₃/water) nanofluid working fluid for a multi-channel heat exchanger (MCHE) experiment, and then simulates its application to electronic chip cooling system to evaluate the practicability of its actual performance. The experimental variables included nanofluids of different weight concentrations (0, 0.5, and 1.0 wt.%) and the inlet water temperature at different flow values. Results show that the overall heat transfer coefficient ratio was higher at higher nanoparticle concentrations. In other words, the overall heat transfer coefficient ratio was higher when the probability of collision between nanoparticles and the wall of the heat exchanger was increased under higher concentration, confirming that nanofluids have considerable potential for use in electronic chip cooling systems.

[en] In the present paper we report the investigations by scanning electron microscopy of Al thin films prepared by pulsed laser ablation deposition experiments in vacuum. Laser parametric studies show that the poor thickness uniformity of Al films arises from surface roughening and structure formation on the irradiated Al target surface. Moreover, it has been confirmed that the plume deflection effect, the morphological changes of the irradiated target surfaces and of the deposited films strongly depend on the laser fluence (4.6-14.7 J/cm²). At low laser fluence, plume deflection angles up to 12^o and columnar structures on the target surface have been observed. The variation in the target morphology and in the droplets density of the deposited films can be associated with competitive ablation processes related to different values of local incident laser fluence. Systematic profilometric investigations of the deposited Al films revealed a strong asymmetry during the deposition process. These results confirm once again our previous achievements obtained with Si laser ablation experiments.

[en] Highlights: ► The BaTiO₃/SrTiO₃ superlattices with embedded Ni NCs were successfully fabricated by L-MBE. ► The influence with the various concentrations of Ni nanocrystals embedded in BaTiO₃/SrTiO₃ superlattices was also discussed. ► The BaTiO₃/SrTiO₃ superlattices with lower concentration of embedded Ni NCs had higher permittivity and dielectric loss compared with the pure BaTiO₃/SrTiO₃ superlattices. ► The dielectric enhancement of BaTiO₃/SrTiO₃ superlattices with embedded Ni NCs was proposed to explained by Drude quasi-free-electron theory. - Abstract: The self-organized Ni nanocrystals (NCs) were embedded in BaTiO₃/SrTiO₃ superlattices using laser molecular beam epitaxy (L-MBE). The stress of the composite films was increased with the increasing concentration of embedded Ni NCs, as investigation in stress calculation. The influence with the various concentrations of Ni NCs embedded in BaTiO₃/SrTiO₃ superlattices was also discussed. The internal stress of the films was too strong to epitaxial growth of BaTiO₃/SrTiO₃ superlattices. Compared with the pure BaTiO₃/SrTiO₃ superlattices, the BaTiO₃/SrTiO₃ superlattices with lower concentration of embedded Ni NCs had higher permittivity and dielectric loss. Furthermore, the dielectric enhancement of BaTiO₃/SrTiO₃ superlattices with embedded Ni NCs was proposed to explained by Drude quasi-free-electron theory.

[en] Highlights: ► Microwave-assisted Zn layers onto Li₄Ti₅O₁₂ crystals serves as superior anode materials. ► Microwave heating is capable of depositing Zn layers over the surface of spinel Li₄Ti₅O₁₂ within 6 min. ► The thickness of Zn layer is an increasing function of zinc nitrate concentration. ► The deposition of Zn coating shows a positive effect on the rate-capability improvement of anodes. - Abstract: In this study, the deposition of microwave-assisted Zn layers onto spinel lithium titanate (Li₄Ti₅O₁₂) crystals as superior anode materials for Li-ion batteries has been investigated. Microwave heating is capable of rapidly depositing Zn layers over the surface of spinel Li₄Ti₅O₁₂ within 6 min. The thickness of Zn layer (i.e., 1–10 nm) is an increasing function of zinc nitrate concentration under the microwave irradiation. The charge–discharge curve of Zn–Li₄Ti₅O₁₂ anode still maintains the plateau at 1.5 V, contributing to the major portion in the overall specific capacity. The presence of Zn coating significantly facilitates the capacity retention (78.1% at 10 C/0.2 C) of the composite anodes with high Coulombic efficiency (>99.9%), indicating an excellent reversibility of insertion/de-insertion of Li ions. This can be ascribed to the fact that well-dispersed Zn layer offers an electronic pathway over the Li₄Ti₅O₁₂ powder, thus imparting electronic conduction and reducing cell polarization. Accordingly, the deposition of Zn coating, prepared by the rapid microwave heating, shows a positive effect on the rate-capability improvement of Li₄Ti₅O₁₂ anodes.