B_2O_3-TiO_2-Mg-C体系燃烧反应热力学与产物结构变化过程研究

对B2 O3-TiO2 -Mg -C体系的燃烧反应热力学进行了研究 ,结果表明 ,该体系化学反应机理为 :Mg先还原B2 O3和TiO2 ,新生的Ti与B和C反应生成TiB2 和TiC ;TiO2 的还原经历了TiO2 Ti3O5TiOTi2 OTi的逐步过程 .对燃烧合成的产物结构形成机理进行了研究 ,表明当燃烧区的能量传到预反应区时 ,B2 O3首先熔化并均匀地包裹在Mg ,TiO2 和C周围 ,Mg熔化后通过扩散与B2 O3和TiO2 反应 ,随着预反应区温度的升高 ,B2 O3与Mg作用还原出B ,TiO2 与Mg作用还原出Ti,然后Ti与B或C反应形成TiB2 或TiC晶核 ,最后TiB2

Microstructure evolution and Al_3(Sc_(1-x)Zr_x) precipitates' kinetics in Al-Zn-Mg alloy during homogenization

The microstructure evolutions of two A1-Zn-Mg alloys, one of which was alloyed with Sc and Zr, and the kinetics of A13（SCl-xZrx） precipitates in the A1-Zn-Mg alloy during homogenization were investigated. Both alloys under as-cast condition with supersaturated, non-equilibrium T（Mg32（A1, Zn）49） phase and impurities phase were displayed. When the homogenization temperatures are below 350 ~C, Zn and Mg atoms precipitate from matrix; however, when the temperatures are above 400 ~C, T phase dissolves into matrix, enhancing solid-solution strengthening. Kinetics of A13（Scl.xZrx） precipitates was studied based on Jmat Pro software calculation and the difference values between the hardness of the two alloys in each homogenization condition. The calculations predict that the Sc and Zr solubilities in ct-A1 decline with the presence of Mg and Zn. Investigation of the difference values reveals that when the temperature is between 300 ~C and 350 ~C, the nucleation rate of A13（Sc1-xZrx） precipitates is the highest and the strengthening effect from A13（SCl_xZrx） precipitates is the best. After homogenization at 470℃ for 12 h, non-equilibrium T phase disappears, while impurity phase remains. The mean diameter of A13（Scl_xZrx） precipitates is around 18 urn. Ideas about better fulfilling the potentials of Sc and Zr were proposed at last.

Influence of Filtration Processes on Aqueous Nanostructures by NIR Spectroscopy

Filtration processes are worldwide used for sterilizing solutions and substrates. Filtration seems to induce the formation of aqueous nanostructures. The aim of this work was to verify the influence of filtration processes on water structure detected by spectral variations in NIR region. Samples of ultrapure water （MilliQ-Millipore, Vimodrone, Milan, Italy） before and after iterated filtrations were analyzed. NIR spectra were collected in transmission mode in the whole NIR range, by using NIRFIex N500 spectrometer at constant temperature （40 ± 1 ℃）. NIR data were processed using Unscrambler software v. 9.2 in evaluating qualitative differences between filtered and not filtered samples. The information related to possible solvent physical stresses were highlighted in the range 6500-7500 cm^-1. The shifts observed were ascribable to a different distribution of the number of water molecules involved in hydrogen bonds in filtered and not filtered water samples, at constant temperature. NIR spectroscopy, commonly used to study relationship between spectral changes and hydrogen bonds in water at increasing temperature values, was applied to evaluate effects of filtration processes on water structure. The obtained results are in agreement with literature data and allowed the improvement of the knowledge about pure water characteristics when some mechanical perturbations are applied.

Evolution of the vortex structures and turbulent spots at the late-stage of transitional boundary layers

The nonlinear evolution process of new vortex structures at the late-stage of the transition, including the 3-D spatial structure of barrel-shaped vortex and "dark spots" structure observed by experiment research, has been confirmed by our computational results. The formation mechanisms of these structures have been explored. It is revealed that the new vortex structures, the ring-like vortex chain and induced disturbance velocities play a dominant role in the generation of turbulent spots.

An InSAR scattering model for multi-layer snow based on QuasiCrystalline Approximation(QCA) theory

Snow-cover parameters are important indicator factors for hydrological models and climate change studies and have typical vertical stratification characteristics. Remote sensing can be used for large-scale monitoring of snow parameters. In SAR(Interferometric Synthetic Aperture Radar) technology has advantages in detecting the vertical structure of snow cover. As a basis of snow vertical structure detection using In SAR, a scattering model can reveal the physical process of interaction between electromagnetic waves and snow. In recent years, the In SAR scattering model for single-layer snow has been fully studied;however, it cannot be applied to the case of multi-layer snow. To solve this problem, a multi-layer snow scattering mode is proposed in this paper, which applies the QCA(Quad-Crystal Approximation) theory to describe the coherent scattering characteristics of snow and introduces a stratification factor to describe the influence of snow stratification on the crosscorrelation of SAR echoes. Based on the proposed model, we simulate an In SAR volumetric correlation of different types of multi-layer snow at the X band(9.6 GHz). The results show that this model is suitable for multi-layer snow, and the sequence of sub-layers of snow has a significant influence on the volumetric correlation. Compared to the single layer model, the multi-layer model can predict a polarization difference in the volumetric correlation more accurately and thus has a wider scope of application. To make the model more available for snow parameter inversion, a simplified multi-layer model was also developed.The model did not have polarization information compared to that of the full model but showed good consistency with the full model. The phase of the co-polarization In SAR volumetric correlation difference is more sensitive to snow parameters than that of the phase difference of the co-polarization In SAR volumetric correlation and more conducive to the development of a parameter-inversion algorithm. The model can be applied to deepen our understanding of In SAR scattering mechanisms and to develop a snow parameter inversion algorithm.

New insight into solvent engineering technology from evolution of intermediates via one-step spin-coating approach

The anti-polar solvent technique is an effec- tive way to improve the film quality in a perovskite solar cell. In this work, we reveal the reason why chloroben- zene （CBZ） plays an important role in controlling the crystallization process. By investigating the formation of intermediate phases in the precursor solution, we observed that the CH3NH3I （MAI）-PbI2-dimethylformamide （DMF） or MAI-PbI2-dimethylsulphoxide （DMSO） adducts have not yet formed until washed with non-polar solvent. The accelerated formation of intermediate phase yields high crystalline perovskite layers. Rapid solvent evaporation and retarded perovskite crystallization in one-step method are efficient to obtain high-quality perovskite films. Conse- quently, MAI-PbI2-DMSO intermediate shows neat rod-like structure with high crystallinity, which eventually transforms extremely dense and uniform perovskite films.