共查询到18条相似文献,搜索用时 171 毫秒
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采用EPM2二氧化碳分子势能模型,以二氧化碳分子内各原子作为统计对象进行统计计算,探讨温度、薄层切片数及截断半径对其汽—液界面特性参数的影响规律。结果表明,随着截断半径的增大,液相主体密度逐渐增大,汽相主体密度逐渐减小,界面层厚度有所减小;薄层切片数对界面层厚度、液相主体和汽相主体的密度影响不大;随着温度的升高,汽相主体密度增加,液相主体密度降低,汽—液界面厚度增大,界面张力逐渐减小。 相似文献
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采用分子动力学模拟技术,对水及其表面活性剂体系的汽—液界面行为进行了研究。模拟结果表明,随着温度的升高,纯水体系液相主体密度降低,气—液界面厚度增大,界面张力逐渐减小;水—十二烷基硫酸钠体系与纯水体系相比,汽—液界面厚度明显增大,汽—液界面张力明显减小,其随温度的变化规律和纯水体系一致。 相似文献
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采用分子动力学模拟技术,研究了纳米水滴在光滑壁面上的润湿行为规律。模拟结果表明,壁面宽度、厚度以及水分子数对接触角及汽—液界面厚度的影响不大。随着壁面作用势能的减小,接触角线性增大;当壁面作用势能为1.674 k J/mol时,接触角约为90°。随着温度的提高,汽—液界面厚度逐渐增大;疏水壁面的接触角随温度的提高而逐渐增大;对于中性壁面,温度对接触角影响不大;亲水壁面的接触角随温度的提高而逐渐减小。 相似文献
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引言流体的界面性质是化工、冶金、材料等工业生产和设计过程中所需的重要基础物性,近年来采用分子模拟方法从微观角度考察流体界面性质的研究日趋活跃。界面体系的分子模拟较为复杂、费时。目前对简单的球形单原子模型流体及其二元混合物液汽界面体系的研究已较为深入,如Holcomb等采用分子动力学(MD)模拟方法较系统地对Lennard-Jones(LJ)流体的液汽界面进行了研究;郭明学和李以圭采用等概率扰动MonteCarlo(MC)模拟方法考察了方阱流体的液汽界面,但对多原子非球形分子模型流体液汽界面体系的研究报道则很少,只有Thompson,Gu… 相似文献
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Xiuyan SunAchilleas Constantinou Asterios Gavriilidis 《Chemical Engineering and Processing: Process Intensification》2011,50(10):991-997
Stripping of acetone from isopropanol utilizing nitrogen as a sweeping gas was conducted in gas/liquid contactors with slit type microchannels and containing flat sheet, metal and Teflon tortuous pore membranes or microfabricated metal meshes with straight pores. The contactor consisted of parallel metal plates, gaskets, and the membrane or the microstructured mesh so that passages for gas and liquid phases were formed. These slit type microchannels were 200 μm thick for both gas and liquid phases. All the membranes/meshes were wetted by the isopropanol solution. Breakthrough of one phase into the other was successfully described if contortion of the gas/liquid interface was considered at the pore ends. Various conditions during acetone stripping were investigated such as membrane type, gas and liquid flowrates and inlet acetone concentration. A contactor employing a Micro-Etch metal mesh with 76 μm openings and thickness of 50 μm offered the lowest mass transfer resistance and resulted to the best acetone stripping performance. The separation efficiency increased by increasing the gas/liquid flowrate ratio, but was not affected when increasing the inlet acetone concentration. Good agreement between the experiments and an one-dimensional model with no adjustable parameters was observed. 相似文献
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The ionic dissociation step of the nucleophilic substitution reaction: t-BuCl → t-Bu+ + Cl− is studied at the water/dichloroethane (DCE) interface using molecular dynamics computer simulations. The t-BuCl is modeled using an empirical valence bond method where two diabatic states, covalent and ionic, are coupled in the electronically adiabatic limit. Umbrella sampling is used to determine the potential of mean force (PMF) along the reaction coordinate R (defined as the t-Bu to Cl distance) in several interfacial regions of varying distances from the Gibbs dividing surface. The results at the water/DCE interface are compared to previous molecular dynamics calculations of t-BuCl at the water liquid/vapor and water/carbon tetrachloride interfaces. As in the other systems, the transition state shifts to larger R values, and the activation barrier and ΔGrxn increase with decreasing solvent polarity. In contrast with the water/carbon tetrachloride interface, a well-defined transition state exists at the water/DCE interface and persists even as the solute is moved 3 to 6 Å into the DCE phase. Dynamical flux correlation calculations reveal larger deviation of the rate from TST than in bulk water due to slower vibrational relaxation of the product ions. However, the increased density at the water/DCE interface increases the rate of dissociation relative to the water liquid/vapor interface. The transmission coefficient at the water/DCE interface was found to be 25% of the TST rate prediction, or about twice the rate at the water liquid/vapor interface. 相似文献
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A. Adnan 《The Journal of Adhesion》2013,89(5):401-420
Recent studies suggest that adhesion in thin joints depends on several factors including temperature, interface toughness, strain rate, surface roughness of adherends, bondline thickness of adhesives, and many others. Influence of thickness on joint properties is surprising but experimentally well documented without reasonable explanations. In this study, we attempt to address the mechanical behavior of polymer adhesives by molecular dynamics (MD) simulation. We show that interfacial strength of the joints in tensile, shear, or combined loading significantly depends on the coupling strength between adhesives and adherends. Failure of joints is always at the interface when coupling strength is weaker. With stronger interfaces, cohesive failure occurs by cavitation or by bulk shear depending on the loading condition. When joints are loaded in tension, it requires an exceedingly stronger interface to realize pure shear failure, otherwise failure is through interface slip. Under a mixed mode condition, interface slip is difficult to avoid. As long as failure is not at the interface alone, the yield strength of joints improves significantly with the reduction of thickness. Increase in bulk density and change in polymer configurations with the reduction of adhesive thickness are believed to be the two key factors in improving mechanical behavior of adhesives. 相似文献
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Core‐shell particles preserve the bulk properties (e.g., magnetic and optical) of the core while its surface is modified by a shell material. Continuous aerosol coating of core TiO2 nanoparticles with nanothin silicon dioxide shells by jet injection of hexamethyldisiloxane precursor vapor downstream of titania particle formation is elucidated by combining computational fluid and aerosol dynamics. The effect of inlet coating vapor concentration and mixing intensity on product shell thickness distribution is presented. Rapid mixing of the core aerosol with the shell precursor vapor facilitates efficient synthesis of hermetically coated core‐shell nanoparticles. The predicted extent of hermetic coating shells is compared with the measured photocatalytic oxidation of isopropanol by such particles as hermetic SiO2 shells prevent the photocatalytic activity of titania. Finally, the performance of a simpler, plug‐flow coating model is assessed by comparisons with the present detailed computational fluid dynamics (CFD) model in terms of coating efficiency and silica average shell thickness and texture. © 2011 American Institute of Chemical Engineers AIChE J, 2011 相似文献
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采用分子动力学方法对微尺度下赤藓糖醇的固液相变及热传导现象进行了模拟研究。首先选用GROMOS力场计算了赤藓糖醇固液两相的密度并将预测结果与实测值进行对比,验证了该力场的适用性。采用界面/NPT法模拟了赤藓糖醇的微观熔化过程,通过体系的体积突变得到预测熔点约为400 K,和实测值(392±1) K较为吻合。与直接加热纯固态赤藓糖醇的方法相比,该方法由于引入固液界面降低了成核自由能位垒,使得微观熔化过程的模拟更准确。此外,基于非平衡分子动力学方法研究了赤藓糖醇分子间的微观热传导现象。模拟得到液态赤藓糖醇的热导率为0.33~0.35 Wm-1K-1,与宏观实测值(0.33±0.02) Wm-1K-1保持一致。因为处于液态时赤藓糖醇的分子分布具有无序性,所以其热导率预测值几乎不随模拟系统的尺寸而变化。 相似文献