多孔建材中VOC扩散系数的两尺度模型

基于对建材微观结构的分析和压汞实验,提出了预测建材中有机挥发物(VOC)扩散系数的宏观一介观两尺度模型.和传统的从压汞实验计算扩散系数方法不同的是,本模型不仅考虑了孔隙率,还对孔的尺度分布和孔的连接方式进行了研究和分析.三种不同中密度板中VOC的散发实验表明,采用新模型计算的扩散系数比文献中的传统模型更好地吻合实验数据.     

Water confined in two-dimensions: Fundamentals and applications

The behavior of water in close proximity to other materials under ambient conditions is of great significance due to its importance in a broad range of daily applications and scientific research. The structure and dynamics of water at an interface or in a nanopore are often significantly different from those of its bulk counterpart. Until recently, experimental access to these interfacial water structures was difficult to realize. The advent of two-dimensional materials, especially graphene, and the availability of various scanning probe microscopies were instrumental to visualize, characterize and provide fundamental knowledge of confined water. This review article summarizes the recent experimental and theoretical progress in a better understanding of water confined between layered Van der Waals materials. These results reveal that the structure and stability of the hydrogen bonded networks are determined by the elegant balance between water-surface and water-water interactions. The water-surface interactions often lead to structures that differ significantly from the conventional bilayer model of natural ice. Here, we review the current knowledge of water adsorption in different environments and intercalation within various confinements. In addition, we extend this review to cover the influence of interfacial water on the two-dimensional material cover and summarize the use of these systems in potential novel applications. Finally, we discuss emerged issues and identify some flaws in the present understanding.     

Low-Temperature Anti-Stokes Luminescence in Zn1-xMgxSe Mixed Crystals

Investigations of photoluminescence and Raman scattering in the ternary Zn_1-xMg_xSe compounds at 4.2 K were performed both in the Stokes and anti-Stokes regions using cw laser excitation with various wavelengths within the transparency band of the crystals. The anti-Stokes luminescence was observed for the first time in the ternary Zn_1-xMg_xSe compounds. We have found variations in the shape and position of the Stokes and anti-Stokes luminescence bands with an increase in the band gap energy, which depends on magnesium content. We assume that the anti-Stokes emission is generated by two-step excitation via deep-level centers. It is shown that the low-temperature anti-Stokes photoluminescence can probe the spatial distribution profiles of impurities in the bulk of crystals.     

Thermodynamic modeling of Fe–Ni pentlandite

Gibbs energy modeling of iron–nickel pentlandite has been performed using experimental data of ternary phase equilibria. A three-sublattice approach in the framework of the Compound Energy Formalism is developed to refine a two-sublattice model of pentlandite recently applied within a complete assessment of the Fe–Ni–S system. Experimental data about the iron site fraction on the octahedral sublattice at 523.15 K for the composition Fe₅Ni₄S₈ as well as the enthalpy of formation at 298.15 K for the composition Fe_4.5Ni_4.5S₈ are predicted satisfactorily by the novel model. New possibilities to interpret experimental phase equilibrium data on complex phase relations with pentlandite are discussed together on the basis of the recent extension of a second high-temperature heazlewoodite phase to a ternary solution phase.     

A theoretical study of thiophenic compounds adsorption on cation-exchanged Y zeolites

A density functional theory (DFT) method has been applied to study the adsorption of thiophenic compounds such as thiophene (TP), benzothiophene (BT), dibenzothiophene (DBT) on cation-exchanged Cu(I)Y, Ni(II)Y, Ce(III)Y zeolites. All of calculations were carried out by the generalized gradient approximation (GGA) with the BLYP exchange-correlation functional and DNP basis set. The calculated results indicate that the stable adsorption configuration of TP molecule adsorbed on the Cu(I)Y is the η5 adsorption mode, whereas for BT and DBT, the η1S adsorption mode was found for the both molecules. Only the η1S adsorption mode can be obtained for the three thiophenic compounds adsorbed on the Ni(II)Y. The η5 adsorption mode can be ascribed to the adsorption of thiophene molecules on the Ce(III)Y, but the competition of different adsorption modes could possibly occur during the adsorption process of BT and DBT on the Ce(III)Y. Moreover, the selectivity of TP adsorbed on the adsorbents is in the order of Cu(I)Y > Ce(III)Y > Ni(II)Y, while for BT and DBT, the order is Cu(I)Y > Ni(II)Y > Ce(III)Y.     

Structural and short-range order analysis of glassy system

To understand the effects of structural features and to locate their signatures in the As-Ag-Te glassy system, various properties were studied as a function of average coordination number, 〈r〉. The structure of the sample is analyzed by X-ray diffraction technique and is found to be crystalline. The d-spacing and the lattice parameters of the samples were calculated. The structural parameters were discussed on the basis of Ag (silver) effect on As-Ag-Te glassy system. Structural investigations on these compositions revealed the polycrystalline nature of compositions with the presence of hexagonal As-Ag-Te phases. Grain size increased with the Ag content and parameters of unit cell are determined. The variations in the mean atomic volume, V, and the glass transition temperature, T_g, for glass transition, with composition have been reported. The change in thermal parameters was measured using differential thermal analysis (DTA). The results of the program are in agreement with those of analytical method and realized by binding energy represented by the cohesive energy values. The generalized ‘8-n’ rule was used to estimate the average coordination number. Obtained results were treated in the frame of chemical bond approach. We estimated some of physical parameters viz. mean bond energy, glass transition temperature, cohesive energy, average single bond energy, density, compactness and molar volume of all bulk samples. Our experimental and theoretical results were discussed in light of the topological bonding structure, which involves a hierarchy of correlation ranges in short-range order.     

Ab-initio calculations of electronic structure and optical properties of TiAl alloy

The electronic structures and optical properties of TiAl intermetallic alloy system are studied by the first-principle orthogonalized linear combination of atomic orbitals method. Results on the band structure, total and partial density of states, localization index, effective atomic charges, and optical conductivity are presented and discussed in detail. Total density of states spectra reveal that (near the Fermi level) the majority of the contribution is from Ti-3d states. The effective charge calculations show an average charge transfer of 0.52 electrons from Ti to Al in primitive cell calculations of TiAl alloy. On the other hand, calculations using supercell approach reveal an average charge transfer of 0.48 electrons from Ti to Al. The localization index calculations, of primitive cell as well as of supercell, show the presence of relatively localized states even above the Fermi level for this alloy. The calculated optical conductivity spectra of TiAl alloy are rich in structures, showing the highest peak at 5.73 eV for supercell calculations. Calculations of the imaginary part of the linear dielectric function show a prominent peak at 5.71 eV and a plateau in the range 1.1-3.5 eV.     

毛细管电泳分离-激光诱导荧光检测血清中的巴氯芬

首次将新合成的柱前衍生试剂6-氧-（N-琥珀酰亚胺乙酸酯）-9-（2′-甲氧羰基）荧光素（SAM F）用于巴氯芬（B aclofen）的衍生标记,并采用毛细管电泳分离-激光诱导荧光（CE-L IF）法分离检测衍生物。研究表明,在磷酸盐缓冲溶液（pH=7.5）介质中,30℃下10m in即可完成衍生反应。反应物在pH 5.6,35mm o.lL-1的磷酸盐缓冲溶液中12m in内达到分离,检出限为6×10-10m o.lL-1。本法用于血清中巴氯芬的分析测定,回收率为95.8%—101.0%。     

Fusion cross section for the system6Li+28Si atE ∼ 36 MeV

The fusion cross section for the system⁶Li+²⁸Si has been measured atE∼36 MeV. Combining this with the data available at lower energies, the nucleus-nucleus real potentials have been determined for a range of interaction distances.     

Frequency combinations in the magnetoresistance oscillations spectrum of a linear chain of coupled orbits with a high scattering rate

The oscillatory magnetoresistance spectrum of the organic metal (BEDO)₅Ni(CN)₄. 3C₂H₄(OH)₂ has been studied up to 50 T, in the temperature range from 1.5 K to 4.2 K. In high magnetic field, its Fermi surface corresponds to a linear chain of quasi-two-dimensional orbits coupled by magnetic breakdown (MB). The scattering rate consistently deduced from the data relevant to the basic α and the MB-induced β orbits is very large which points to a significant reduction of the chemical potential oscillation. Despite of this feature, the oscillations spectrum exhibits many frequency combinations. Their effective masses and (or) Dingle temperature are not in agreement with either the predictions of the quantum interference model or the semiclassical model of Falicov and Stachowiak.