超临界流体化学热力学

本文简要介绍了超临界流体的基本概念和性质，评述了化学热力学在超临界萃取、超临界态化学反应、超临界流体制备材料等方面的作用和研究进展，讨论了二氧化碳-离子液体两相体系的热力学行为。     

分子模拟在超临界流体领域中的应用

"分子模拟作为一种全新的研究手段已经在化学、化工、材料、生物等领域受到了广泛的关注。特别是在超临界流体技术方面,其应用不但可以获得许多结构、传递以及热力学信息,而且可以部分取代昂贵的超临界实验。本文从超临界流体在主体相和受限空间中的特性以及超临界萃取、反应等几个方面对现有的分子模拟方法和成果进行总结与评述,并对进一步发展的方向和面临的困难进行了讨论。     

超临界流体色谱中溶质的保留行为

超临界流体色谱中热力学参数最佳化和动力学最佳化同等重要。溶质的保留行为和物质对的分离受柱固定相和流动相各种参数的影响。在本研究中,使用纯CO_2作为流动相,饱和烃、芳烃、以及它们的硝基取代物作为溶质,对上述影响进行了系统地考察。结果发现影响物质对分离的(以分离系数,α,表示)最主要因素是流体的密度。而温度的影响并不明显。柱固定相的性质也有一定程度的影响。在柱固定相相同的情况下,改变操作参数,溶质峰的洗馏顺序可能出现倒置。表明在超临界流体色谱中流动相溶解能力的重要作用。实验结果为了解和优化超临界流体色谱热力学参数提供了依据。     

超临界流体色谱的研究进展

超临界流体色谱作为气相色谱和液相色谱的有力补充可用于热不稳定和低挥发性物质的分析分离和制备,也可用于超临界流体中分子间相互作用的研究。本文从色谱的流动相、固定相、检测系统及应用几方面综述了超临界流体色谱近年来的研究进展。     

超临界流体沉积技术在纳米复合材料制备中的应用*

本文综述了超临界流体沉积法在纳米复合材料制备领域的进展,介绍了利用超临界流体的溶剂化特性、表面张力为零、性质随压力与温度的变化敏感等性质,制备高质量的纳米粒子、薄膜及多孔纳米材料,讨论了超临界流体沉积过程中的吸附、热力学平衡及扩散动力学等问题,总结了不同学者对该方法制备复合材料的机理研究,认为超临界流体沉积法是制备纳米复合材料的有效方法。最后,对深入开展此项研究工作需要努力的方向和解决的关键问题提出了建议。     

超临界流体技术制备超细粒子

超临界流体用于制备超细粒子是一项新技术，本文综述了两种形成微粒的方法；超临界快速膨胀法和超临界反溶剂法，并着重介绍了其在研究和应用方面的进展。     

分子烙印聚合物作超临界流体萃取后处理用固体吸附剂

利用离线超临界流体萃取与高效毛细管电泳相结合，分析了标准添加样品中的除草剂（2，4－二氯苯氧乙酸（2，4－D）），探讨了温度、压力和改性剂对萃取的影响，考察了在不同条件下合成的2，4－D为烙印分子的子烙印聚合物对2，4－D在不同极性溶剂中的吸附能力，并将分子烙印聚合物作为超临界流流体萃取后处理用固体吸附剂，结果表明，在甲醇和水的混合极性溶剂中制备的分子烙印聚合物对提高分析选择性的效果最佳。     

超临界流体色谱仪在天然产物研究中的应用

超临界流体可以用做色谱的流动相，使混合物质在色谱柱上得到分离，这种分离方法被称为超临界流体色谱(Supercdtical Fluid Chromatography,简称SFC)。作为色谱流动相的超临界流体，其作用与超临界流体萃取(Supercritical Fluid Extraction，简称SFE)类似。超临界流体对物质的溶解能力远比一般气体大的多，     

金属离子的超临界流体萃取技术的进展

超临界流体萃取技术在分离方面发展迅速,应用前景十分广泛。文中综述了超临界流体技术的萃取机理及对金属离子萃取的研究。     

超临界流体技术研究进展

本文综述了超临界流体技术在萃取、材料制备、化学反应及相转移催化等方面的应用, 介绍了有代表性的超临界萃取和反应装置。对今后工作提出了一些建议。     

Prandtl Number in Classical Hard-Sphere and One-Component Plasma Fluids

The Prandtl number is evaluated for the three-dimensional hard-sphere and one-component plasma fluids, from the dilute weakly coupled regime up to a dense strongly coupled regime near the fluid-solid phase transition. In both cases, numerical values of order unity are obtained. The Prandtl number increases on approaching the freezing point, where it reaches a quasi-universal value for simple dielectric fluids of about ≃1.7. Relations to two-dimensional fluids are briefly discussed.     

电流变液体的研究进展

电流变液体自从20世纪40年代首次发现以来,由于其广泛的工程应用前景以及潜在的巨大经济和社会效益,已经成为众多研究领域的一个热点.本文综述了电流变液体的组成、电流变材料的研究进展、影响电流变效应的主要因素以及电流变液体研究的应用进展.     

基于链化分析的磁流变液剪切屈服应力模型

Under an external magnetic field, the particles in a magnetorheological fluids (MRFs) aggregated into chains of dipoles aligned in the direction of the magnetic field so that the MRFs exhibited solidlike mechanical behavior with a yield shear stress. Based on a microscopic analysis and making use of the statistical approach, a micro-to-macroscopic model is proposed for the constitutive behavior of MRFs and the main influencing factors, such as the intensity of magnetic induction, the size of particles, volume fraction of particles, shear strain rate and saturation magnetization. The effects of the influencing factors on the macroscopic behavior of MRFs are investigated and compared with the experimental data. It is found that the proposed model can efficiently describe the mechanical properties of MRFs and can be easily applied to solve practical engineering problems.     

Solution Association Characterization of Hydrophobically Associating Polyacrylamide Obtained from Produced Fluids

The hydrophobically associating polyacrylamide (HAPAM) obtained from produced fluids with compositional homogeneity was systematically investigated by zero-shear viscosity, fluorescence, sand-pipes experiment and adsorption behavior. The results showed that HAPAM obtained from produced solution through porous media has been possession in hydrophobic association character. The critical association concentration (CAC) determined by viscosity method, fluorescence spectroscopy method and micro-pore method have no obvious change compared with the original polymer. The hydrophobic associative capability of HAPAM obtained from produced fluids was smaller than that of original HAPAM. Compared to original PAM and PAM obtained from produced fluids, HAPAM obtained from produced fluids still exhibits promising applied potential. It reveals the possibility that HAPAM obtained from produced could be re-used for enhance oil recovery.     

聚合物流体的范德华凝聚行为

研究了由聚合物的范德华作用导致的凝聚行为. 研究发现, 尽管聚合物同小分子的相行为的形成原因不同(聚合物体系的相行为是由动能、构象熵项和范德华作用能三项相互竞争的结果, 而小分子的相行为是由动能和范德华作用能相互竞争的结果), 但是它们表现出了极为相似的相行为.     

Study on Non-Newtonian Behaviors of Lennard-Jones Fluids via Molecular Dynamics Simulations

Using nonequilibrium molecular dynamics simulations, we study the non-Newtonian rheological behaviors of a monoatomic fluid governed by the Lennard-Jones potential. Both steady Couette and oscillatory shear flows are investigated. Shear thinning and normal stress effects are observed in the steady Couette flow simulations. The radial distribution function is calculated at different shear rates to exhibit the change of the microscopic structure of molecules due to shear. We observe that for a larger shear rate the repulsion between molecules is more powerful while the attraction is weaker, and the above phenomena can also be confirmed by the analyses of the potential energy. By applying an oscillatory shear to the system, several findings are worth mentioning here:First, the phase difference between the shear stress and shear rate increases with the frequency. Second, the real part of complex viscosity first increases and then decreases while the imaginary part tends to increase monotonically, which results in the increase of the proportion of the imaginary part to the real part with the increasing frequency. Third, the ratio of the elastic modulus to the viscous modulus also increases with the frequency. These phenomena all indicate the appearance of viscoelasticity and the domination of elasticity over viscosity at high oscillation frequency for Lennard-Jones fluids.     

镝钴铁氧磁流体的制备与性质研究(英文)

为了提高磁流体的抗氧化能力,制备了镝钴铁氧磁流体.利用古埃磁天平研究了温度对磁性和稳定性的影响;研究了稀土镝磁性能的改性、表面活性剂的表面改性,并从理论上进行了分析.利用X射线衍射仪(XRD)、透射电镜(TEM)对制得的磁粒子的组成、结构及粒径进行了分析.     

超临界流体萃取分离离子液体与有机物及其相平衡的研究

离子液体具有一些优良的物理和化学性质,非常有希望成为传统有机溶剂的替代溶剂.但是如何从过程物流中分离和回收离子液体将是其工业化应用的一个很大挑战.蒸馏、液液萃取和超临界萃取是目前已知的三个可行的方法.其中超临界萃取可应用于离子液体与挥发的或相对不挥发的有机物的分离,而且不存在相间交叉污染.本文从二元体系相平衡、三元体系相平衡、模型化研究和萃取实验结果方面介绍了超临界萃取方法的最新研究进展,在此基础上提出了用超临界丙烷替代超临界二氧化碳作为萃取溶剂的新思路,并探讨了该领域今后的研究方向和工业化前景.     

Chromatography with Supercritical Fluids

Chromatography with supercritical fluids unites the features of both gas chromatography and liquid chromatography, yet retains special characteristics of its own. The diffusion coefficient and particularly the viscosity of fluid phases may approach values for low-pressure gases, while the solvent power may be similar to that of liquids. However, with supercritical fluids it is possible to control chromatographic separations very effectively by pressure programming, since the solubility increases with increasing density. Temperature programming, on the other hand, can have the opposite effect to that in gas- or liquid-chromatography since the density decreases with increasing temperature at a given pressure. Supercritical fluid chromatography is primarily of interest for the separation of higher molecular weight compounds. The efficiency of this method of separation is demonstrated on several homologous series. Thus, a styrene oligomer with nominal M_w=2200 can be resolved by a pressure and temperature program into 40 species.