The solidification behaviors of Sn-Zn alloy under rotating magnetic field (RMF) with different magnetic intensities and different rotating frequencies were investigated, and the velocity of the convection induced by RMF was calculated. It is found that the trunk length of the precipitated phase reduces with the increase of magnetic intensity and rotating frequency, and the precipitated-phase distribution is more uniform. The tangential rate increases with increasing the magnetic intensity and rotating frequency, and reaches the maximum value at about 0.55r0. All the results indicate that the solidification microstructure is attributed to the effect of RMF on the nucleation, temperature fluctuation and fluid convection in the solidification process. It predicts that RMF presents obvious advantages on controlling solidification microstructure.
Solidification behaviour of Pb-Bi alloys under rotating magnetic field (RMF) was investigated experimentally to understand the effect of the frequency of RMF on the nucleation and growth behaviour. It was found that, as the increase of the rotating frequency, the grains are fragmented and refined gradually until a transition from columnar to equiaxed microstructures happens at a rotating frequency of 40 Hz. Moreover, the Bi concentration of the primary phase decreases and macrosegregation is eliminated effectively with RMF. These are due to the effect of RMF on the nucleation, growth and fluid flow in the solidification process.
(001) interfaces are considered by performing generalized gradient approximation plus on-site Coulomb correction calculations. A potential antiferromagnetic alignment between the interface layer and bulk is conjectured for the b-type LSMO/STO (001) interface where the atomic-layer stacking near interface is Á Á ÁLaO-MnO 2 -LaO-MnO 2 -SrO-MnO 2 -SrO-TiO 2 Á Á Á (SrO termination). This is in qualitative agreement with the fact that suppression of ferromagnetism at the SrO-terminated (001) interface is found at some experiments. The small magnetic exchange energies, for the SrO-terminated LSMO/STO (001) interfaces, suggest that Mn spins at the interface are likely to reverse as the temperature changes. Hence, possible magnetic reconstructions will be expected to occur at the SrO-terminated (001) interfaces when temperature increases. Under thermodynamic equilibrium, the calculated phase diagrams show that, with the exception of the c-type (001) interface where the atomic-layer stacking near interface is Á Á ÁLa 2/3 Sr 1/3 O-MnO 2 -SrO-TiO 2 Á Á Á (SrO termination), all other considered LSMO/STO (001) interfaces may be stabilized in the proper conditions. The spin-resolved density of states shows that high spin-transport behaviors could be achieved at the ferromagnetic TiO 2 -terminated (001) interfaces. The results of the calculations can compare favorably with the experimental results for the LSMO/STO (001) junctions.
Anatase TiO2- thin films on glass substrates were prepared by sol-gel dip-coating method. We designed a multi-round annealing process which was under the air pressure of 5 Pa and then 5×10-2 Pa for one hour each at 550 °C, and such process was repeated for three times. The special designed annealing process can obviously improve the conductivity of the udoped TiO2- thin films. The minimum resistivity of the undoped TiO2- thin films reached 0.8 Ω cm after being treated by the multi-round annealing process. It was demonstrated that such annealing process was an effective way to increase the defects in TiO2- thin films such as oxygen vacancies. The average transmittances of the films were approximately 60~80% in the visible range with the forbidden gaps of 3.25~3.35 eV. After the multi-round annealing process, the optical forbidden gaps of the films became narrowed slightly, which might be also related to the defects introduced during the multi-annealing process.
The sol-gel method was employed to prepare the Eu3+-doped TiO2 thin films. The influence of doping concentration and annealing temperature on the structures and photoluminescence (PL) properties was investigated. The result of X-ray diffraction revealed that all the films are of anatase phase. It is shown that the PL intensities of the films increased with Eu3+ concentration and reached the maximum at 1.4 mol%, then decreased with the concentration. Observed anatase phase appeared at temperature above 400 °C, and the luminescence intensity increased with the increase of annealing temperature.
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