超疏水聚合物表面的水滴蒸发模拟

基于质量守恒和Fick第一定律，模拟了水滴在超疏水聚合物表面的蒸发全过程．研究从以往的接触角<90±扩展到>150±，液滴形貌扩展为椭球球帽模型进行疏水表面蒸发模拟．水滴在超疏水PC和FPU/PMMA表面蒸发的实验结果显示，计算的椭球球帽模型可以更好的反映出液滴接触角和高度的变化情况，并且不同聚合物表面接触角的相同变化趋势也揭示出微-纳二级结构表面结构不仅影响液滴接触角，也影响液滴蒸发模式．     

On the decay of hot metallic clusters by evaporation

Starting from the Weisskopf theory decay rates for the evaporation of cluster atoms from hot liquid alkali metal clusters are derived. The crucial input quantity is the level density which is determined from empirical properties of the bulk, namely from the specific heat and the thermal expansion coefficient. The resulting rate expression is compared with decay rate formulas given by Engelking, Klots and Gspann. Furthermore, critical (appearance) sizes of multiply charged clusters are calculated by equating the rates for neutral monomer and light charged particle emission. Also shrinking and cooling rates of large hot clusters are determined by treating multiple emission of cluster atoms, thus establishing a time scale for the decay of clusters theoretically.     

Water diffusion through hydrogel membranes: A novel evaporation cell free of external mass-transfer resistance

A novel evaporative cell is used to measure steady-state gradient-driven diffusion rates of water through hydrogel membranes in the absence of external mass-transfer resistance. In this cell, the bottom surface of a hydrogel membrane is exposed to pure water vapor at known activity (a_w) less than unity, while a sealed liquid-water reservoir bathes the upper membrane surface. Induced by the chemical-potential gradient between the two surfaces, the water evaporation rate is monitored by the rate of weight loss of the water reservoir.Results at ambient temperature are compared with those from measured water flux through soft-contact-lens (SCL) materials and with other published experimental results. Concentration-dependent water diffusivities are obtained by interpreting measured water fluxes for 0.11 ≤ a_w ≤ 0.93 with extended Maxwell–Stefan (EMS) diffusion theory. Thermodynamic non-ideality is taken into account through Flory–Rehner polymer–solution theory. Shrinking/swelling is modeled by conservation of the total polymer mass assuming volume additivity. In spite of correction for thermodynamic non-ideality, EMS–water-diffusion coefficients increase with the water volume fraction, especially strongly for those hydrogel materials with low liquid-saturated water contents. The evaporation cell described here provides a simple robust method to establish water transport rates through soft-contact-lenses and other hydrogel membranes without the need to correct for external mass-transfer resistance.     

Patterns from drying drops

The objective of this review is to investigate different deposition patterns from dried droplets of a range of fluids: paints, polymers and biological fluids. This includes looking at mechanisms controlling the patterns and how they can be manipulated for use in certain applications such as medical diagnostics and nanotechnology.     

CALCULATION OF VAPOR PRESSURES FROM MODEL FRAGRANCE EMULSIONS DURING EVAPORATION

The vapor pressure data from previous publications of a model fragrance emulsion system consisting of water, an aromatic fragrance phenethyl alcohol, an aliphatic one limonene, and a nonionic surfactant Laureth 4, were used to calculate the variation in vapor pressures of both fragrances and water during free evaporation. The evaporation path in a three-dimensional four-component phase diagram was estimated from the vapor pressures.

The results showed as expected that the high note fragrance compound evaporates first followed by water and the low note one. Unexpectedly, it was found that vapor pressure of low note fragrance, phenethyl alcohol, is significantly increased during evaporation.     

Solvent atmosphere controlled self-assembly of unmodified C60： A facile approach for constructing various architectures

A facile approach for constructing diverse architectures of unmodified C60 was developed via simple evaporation of pure C60 solution in CS2 under various poor solvent atmospheres. Diverse architectures such as belts, sheets, and starfishes were successfully constructed under different experimental conditions. C60 belts obtained under EtOH atmosphere were confirmed to be a face-centered cubic （fcc） structure. The solvent atmospheres not only slowed clown the evaporation speed, but also could reorganize the self-assembly of C60 by partially re-dissolving the initially formed architectures. This concept represents a novel method for preparation of nanostructures of C60 and could also be applied for controlling of the self-assembly of other functional organic molecules.     

Enhancement of evaporation and combustion of liquid fuels through porous media

Existing designs of most conventional liquid fuel burners have relied solely on spray atomizers, with a large amount of very fine droplets forming in a relatively large combustion chamber, resulting in a relatively low combustion intensity. Against this background, a novel down-flow compact porous burner system was developed for burning kerosene without the need of using a spray atomizer. Successive development on this burner research is important in view of the need to create energy by an efficient device based on simple technology. The focus has been on the introduction of the packed bed emitter installed downstream of the porous burner. The evaporation process and combustion phenomena that occurred are described through the coupled interaction of the solid phase (porous burner), the liquid phase (kerosene) and the gas phase. Enhancement of evaporation and combustion are evaluated through the measured thermal structures in terms of temperature distribution along the burner length and emission characteristics at the burner exit. Stable combustion with low emission of pollutants was realized even though the combustion flame was confined in-between the porous burner and the packed bed emitter with an increase in the back-pressure. The effects of various parameters including heat input and equivalence ratio on the combustion characteristics were clarified to confirm improvement in mixing of the fuel vapor/air mixture and turn-down ratio of the burner. The effect of the introduced packed bed emitter with suitable bed length and its installation location is investigated as an efficient method for enhancement of evaporation and combustion of the liquid fuels without a spray atomizer. Future applications of this type of burner system are suggested.     

Quasifission and difference in formation of evaporation residues in the O + W and F + Ta reactions

The role of the entrance channel has been studied to ascertain a cause of the observed difference between the evaporation residue cross sections normalized to the fusion cross sections in the ¹⁹F + ¹⁸¹Ta and ¹⁶O + ¹⁸⁴W reactions at high excitation energies. The theoretical analysis performed in the framework of the dinuclear system and advanced statistical models showed that the more intense yield of evaporation residues in the ¹⁶O + ¹⁸⁴W reaction in comparison with that in the ¹⁹F + ¹⁸¹Ta reaction was explained by the large capture and fusion cross sections in the former reaction, which is in agreement with the experimental data. The observed decrease in the evaporation residue cross section normalized to the fusion cross section in the ¹⁹F + ¹⁸¹Ta reaction, in comparison with one in the ¹⁶O + ¹⁸⁴W reaction at large excitation energies, is caused by the unintentional inclusion of the quasifission and fast fission contributions in the fissionlike fragment yields that were used in reconstructing the experimental fusion cross section in the normalizing procedure. The range of the angular momentum distribution for both systems was similar, but the partial cross sections are different, showing the presence of a difference in the hindrance to complete fusion in both reactions.     

Phase transitions in solid-liquid-gas systems with applications to alkali metal generators

Motivated by physical applications we consider a mathematical model describing the evaporation process in solid-liquid-gas systems with two moving boundaries of the phase transition. An alkali metal generator with a working substance in the form of an intermetallic compound and the evaporation of a volatile component into a vacuum is considered. Explicit analytical solutions of the problem under consideration are constructed in three different geometries of the process. We demonstrate that the evaporation boundary moves much more slowly than the dissolution boundary and the liquid layer thickness increases with time. The role of the evaporation coefficient on the evaporation stream and the nonlinear dynamics of the process is studied. An approach developed in the present study can be used for solutions of mathematical models describing similar Stefan-type processes met in other areas of applied physics.