受限界面处流体分子行为的调控及相关分子热力学模型初探:基于高比表面氧化钛的研究进展

纳米受限界面处的流体由于受到界面性质的影响显著,且存在复杂的传递和反应机制耦合问题,其流体分子行为难以调控,成为了现代化工新技术(如膜过程、多相催化)突破的瓶颈。结合了近几年本课题组的相关工作进展,以化学性质稳定的高比表面氧化钛作为研究平台,对界面处流体分子受限行为进行分析,研究了传递和反应机制分别对界面处流体行为的影响,并探索其调控机制;同时对建立的相应分子热力学模型进行了初步探索,通过原子力显微镜技术将界面摩擦性质和分子间相互作用关联,为分子热力学模型提供分子参数。     

复杂流体-固体界面相互作用热力学机制

具有复杂结构的纳微界面往往是界面复杂作用和宏观实验现象的主导因素。要准确描述界面处复杂流体的行为,需要引入能描述复杂流体-固体界面相互作用的分子热力学模型。本综述围绕分子热力学模型化方法拓展至纳微界面传递问题,提出“分子热力学建模+分子模拟+纳微实验”三者有机配合新思路。并针对复杂流体-固体界面相互作用的定量研究,着重综述了作者在热力学建模,分子模拟以及采用原子力显微镜 (atomic force microscopy,AFM) 实验方面的研究进展,创新性地提出将AFM定量化分析作为桥梁,用于构建分子模拟模型,描述复杂界面作用,揭示分子热力学机制,为构建纳微界面传递模型以及分子热力学模型由体相拓展至界面提供了可能。     

复杂流体-固体界面相互作用热力学机制

具有复杂结构的纳微界面往往是界面复杂作用和宏观实验现象的主导因素。要准确描述界面处复杂流体的行为,需要引入能描述复杂流体-固体界面相互作用的分子热力学模型。本综述围绕分子热力学模型化方法拓展至纳微界面传递问题,提出"分子热力学建模+分子模拟+纳微实验"三者有机配合新思路。并针对复杂流体-固体界面相互作用的定量研究,着重综述了作者在热力学建模,分子模拟以及采用原子力显微镜(atomic force microscopy,AFM)实验方面的研究进展,创新性地提出将AFM定量化分析作为桥梁,用于构建分子模拟模型,描述复杂界面作用,揭示分子热力学机制,为构建纳微界面传递模型以及分子热力学模型由体相拓展至界面提供了可能。     

分子模拟在化学工程中的应用

总结了不同尺度分子模拟技术在化工中的发展现状,利用量化计算的方法,可以研究纳微尺度表界面的活性及其对催化反应的影响。采用分子动力学模拟可很方便地研究受限条件下流体行为,采用粗粒化模拟技术可研究介观结构。最后介绍了反应力场模拟这种涵盖反应和传递的模拟新方法。随着模拟理论和并行技术的进步,分子模拟的定量化程度越来越高,必将与化工应用的实验结果越来越有可比性,从而在化工生产和实践中担当更重要的角色。     

流体分子热力学

<正> 流体分子热力学是综合运用经典热力学、分子物理学和统计力学方法,构作理论的或半经验的模型,以解释、关联和预测流体及其混合物的热力学性质和相行为的一门学科。     

二维硬碟链流体的分子热力学

采用三维硬球链流体分子热力学模型构建思路,以单体缔合的统计力学理论为基础,获得了二维硬碟链流体剩余亥氏函数和压缩因子与空穴相关函数的关系。建立的模型已应用于线型硬碟链流体,并探索了模型在不同结构的硬碟链流体中的应用。研究结果显示,建立的模型能满意预测r=5的硬碟链流体的压缩因子,其预测精度优于现有模型。相同链长、相同对比链节密度下,线型硬碟链流体压缩因子最大、支链其次、环状最小,证明所建模型能较好区分结构对性质的影响。     

同核双原子分子流体液汽界面的分子动力学模拟研究

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…     

基于微量热法对多孔碳与双氧水相互作用过程的传质阻力分析

多孔材料作为催化剂对现代化学工业起到重要推动作用,但其纳米受限孔道造成的界面传递问题不容忽视。直接法合成双氧水（H₂O₂）过程中,揭示H₂O₂脱附过程传递与反应竞争博弈的介尺度机制是提高产率的关键。线性非平衡热力学为解耦界面扩散及反应提供了统一框架,但缺少合适通量测定方法。因此,本文设计多孔碳与H₂O₂相互作用的微量热实验,结合分子模拟及孔结构表征实验揭示多孔碳材料的界面传递结构,实现了非平衡热力学的定量传质阻力分析,进一步获取了表界面浓度场的动态变化。研究结果表明：微量热法是定量解耦并揭示扩散-反应机制的有效线性非平衡热力学阻力分析方法;介孔结构、生物骨架结构及担载1%（质量） Pd元素均能增强H₂O₂在多孔碳中的传质通量,但实现超高通量需要扩散与反应阻力的匹配;非平衡热力学阻力解耦方法是揭示多相反应过程介尺度机制的重要定量描述方法,有望为过程的调控及优化提供理论依据。     

材料化学工程科学内涵及方法初探:从介观尺度界面流体行为出发认知材料

作为一门新兴的交叉学科,材料化学工程科学内涵的进一步凝练和方法论的建立显得十分重要和迫切。介观尺度下界面流体的研究对于材料化学工程具有重要意义,材料化学工程的科学内涵在于通过认识介观尺度下界面处流体行为来"认知"材料,以期建立材料结构、性能(应用)与制备(生产)三者之间的关系。其中,弄清介观尺度下复杂作用和复杂结构对界面流体行为的影响,是"认知"材料的关键。分子模拟技术作为单因素遴选介观尺度各影响因素的有效手段,在实际应用中存在两大难点:如何同时获得界面流体反应和传递两个方面的信息;如何实现分子层面认识在材料应用层面的转化。基于此,初步讨论了材料化学工程研究方法的发展趋势。     

重油分子的孔内受限扩散研究进展

随着常规石油资源日趋紧张和原油重质化,重油加氢处理过程越来越受到重视。由于重油分子在催化剂孔道中的受限扩散阻力影响着催化加氢反应速率和催化剂的利用率,因此研究重油分子在催化剂孔道中的内扩散行为及规律对指导加氢催化剂优化设计和加氢催化剂有效利用具有重大意义。本文介绍了重油分子孔内受限扩散研究的膜池法、吸附-扩散法和扩散-反应动力学法,指出相较于膜池法和吸附-扩散法,由扩散-反应动力学法研究所得结果更能反映在反应条件下重油孔内的受限扩散行为及规律,具有更广泛的应用价值;并简述了重油分子孔内扩散受限因子的研究进展,分析了用于重油孔内扩散行为及规律研究的多孔材料,指出孔结构均一的模型催化剂是一种利于扩散研究的理想多孔材料。     

离子液体/硫酸催化C4烷基化反应过程强化——表界面特性研究

利用分子动力学（MD）模拟研究了不同支链长度以及官能团的Brønsted酸性离子液体（BILs）对H₂SO₄/C₄烷烯界面特性的调控。结果表明,BILs的加入可以明显增强C₄烷烯在两相界面处的溶解和扩散,有利于烷基化油品的提升。烷基链较长的阳离子表现出较强的界面密度富集现象,并且其支链倾向于伸入C₄烷烯相,有利于界面性质的增强。阳离子支链的增长能够促进C₄烷烯的溶解,同时增大了C₄烷烯的界面存留率,不利于其界面扩散。另外,相比于非磺酸功能化离子液体（non-SFILs）,磺酸功能化离子液体（SFILs）促进了C₄烷烯的溶解,但抑制了C₄烷烯的扩散。本文在C₄烷基化界面性质方面的研究有利于深入理解C₄烷基化过程,相关结果有望为烷基化过程强化和新型催化剂的优化和设计提供帮助。     

Reinforcement of adhesion and development of morphology at polymer–polymer interface via reactive compatibilization: A review

Polymer blending is a common and effective way to develop new materials with desirable physical and mechanical properties. Since most polymer pairs are immiscible, reactive compatibilization has been extensively studied to stabilize morphology of polymer blends and improve their mechanical properties. In the past several years, considerable interest has been expressed in understanding the fundamental kinetics and mechanisms of the interfacial reaction, investigating the reinforcement of the interfacial adhesion and the development of morphological structure at polymer–polymer interface induced by the interfacial reaction. The present review focused on some theoretical and experimental results that include the formation and growth of copolymers at the interface, and also the major factors such as reaction conditions, the concentration and bulk properties of the functionalized polymer, the thermodynamic interaction between the functionalized polymer and the matrix, which can influence the interfacial adhesion and morphological development. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

THE KINETICS OF COBALT(II) EXTRACTION WITH EHEHPA IN HEPTANE FROM ACETATE SYSTEM USING AN IMPROVED LEWIS CELL TECHNIQUE†

ABSTRACT

The cobalt(II) extraction kinetics and mechanism with EHEHPA (2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester) were investigated by an improved constant interfacial area stirred cell. The effects of the buffer species, stirring rate, temperature, specific interfacial area and surfactants on the extraction rate showed that the extraction regime was dependent on the extraction conditions and the most probable reaction zone was at the liquid-liquid interface. This extraction process was reaction controlled at lower concentration of the reactants, while it was mixed chemical reaction-diffusion or diffusion controlled only for higher concentration of the reactants. An interfacial extraction reaction model with diffusion was derived. The kinetics of the extraction process was simulated with this model.     

纳米颗粒与表面活性剂的自组装行为对硅油-水界面性质影响的分子动力学

采用耗散分子动力学模拟方法,研究了氨基修饰的表面活性剂聚二甲基硅氧烷与羧基修饰的二氧化硅纳米颗粒在硅油-水界面上的自组装行为,通过分析油-水界面性质（界面厚度和界面张力）和活性剂的结构性质（回转半径）,探讨了活性剂质量分数ω_S和纳米颗粒质量分数ω_N等对界面性质的影响,阐明了自组装过程中界面性质的影响因素。结果表明,纳米颗粒和表面活性剂在油-水界面上自发组装成纳米颗粒表面活性剂,当ω_S=0.005~0.2时,纳米颗粒表面活性剂可有效降低界面张力;而在ω_S=0.2~0.5时,该组装行为使界面张力随ω_S而提高。当ω_S=0.2时,活性剂的回转半径最大、随时间波动最小,表明活性剂分子被拉伸效果更明显,此时体系的界面张力最低。活性剂结构对界面张力影响较大,活性剂链长在8~17时,端氨基占比较大,即链长最短时,体系的界面张力最低,界面厚度最大。当纳米颗粒直径在2.44~12.21Å(1Å=0.1nm)时,界面张力随颗粒直径增大而降低;当ω_N=0.0165625~0.1325时,界面张力随ω_N而提高。当活性剂与颗粒的作用参数在9~21时,作用参数对界面性质无影响。     

Mechanism of the interfacial reaction between sapphire and Sn-3.5Ag-4Ti solder at a low temperature in air by ultrasound

The joining of sapphire at a low temperature is necessary for the packaging of temperature-sensitive components. In current processes, the sapphire was bonded to Sn-based Ti-activated solders by mechanical scraping and stirring. To improve the efficiency and the bonding strength, the joining of sapphire by ultrasonic-assisted hot dipping and soldering at 250 °C in air was investigated. The relationship between the interfacial structure and shear strength of the soldered joints was revealed. The joints dipped for different durations and soldered for 0.5 s had similar interface morphologies, while the shear strength of the joints was controlled by the dipping duration. The shear strength of the joints dipped for 100 s reached 33 MPa. An uneven reaction layer of Ti oxides was found at the interface by TEM and EDS. A physical model was established to explain the formation of the reaction layer and the evolution of the interface microstructure. The mechanism of the interfacial reaction was discussed based on thermodynamics. The results of the thermodynamic calculations show that the replacement reaction between Ti and sapphire could not occur at the joining temperature of 250 °C. The increasing temperature induced by ultrasound at the liquid/solid interface was calculated by bubble dynamics and thermal conduction methods. It could be inferred that the reaction may be dominated by a local high temperature at the interface. Our finding demonstrates that the ultrasonic effects promote and facilitate the interfacial reaction of sapphire and Sn-3.5Ag-4Ti.     

Polymer molecular behaviors at buried polymer/metal and polymer/polymer interfaces and their relations to adhesion in packaging

Packaging materials are widely used in modern microelectronics. The interfacial structures of packaging materials determine the adhesion properties of these materials. Weak adhesion or delamination at interfaces involving packaging materials can lead to failure of microelectronic devices. Therefore, it is important to investigate the molecular structures of such interfaces. However, it is difficult to study molecular structures of buried interfaces due to the lack of appropriate analytical techniques. Sum frequency generation (SFG) vibrational spectroscopy has recently been used to probe buried solid/solid interfaces to understand molecular structures and behaviors such as the presence, coverage, ordering, orientation, and diffusion of functional groups at buried interfaces and their relations to adhesion in situ in real time. In this review, we describe our recent progress in the development of nondestructive methodology to examine buried polymer/metal interfaces and summarize how the developed methodology has been used to elucidate adhesion mechanisms at buried polymer/metal interfaces using SFG. We also elucidated the molecular interactions between polymers and various model and commercial epoxy materials, and the correlations between such interactions and the interfacial adhesion, providing in-depth understanding on the adhesion mechanisms of polymer adhesives.     

Molecular thermodynamic understanding of transport behavior of CO2 at the ionic liquids-electrode interface

The transport behavior of CO₂ at the ionic liquids (ILs)-electrode interface was revealed from the thermodynamic view via molecular dynamics simulations. The hopping and self-diffusive mechanisms were identified in the interfacial and bulk region, and thereafter a hopping-diffusion model was developed to evaluate the transport resistance of CO₂ from bulk to the interface. Meanwhile, the vibrational spectrum and entropy change of CO₂ at the interface were calculated using the thermodynamic analysis method. For ILs with the same cation ([Emim]⁺), both transport resistance and entropy decrease follow the order: [BF₄]⁻ < [AC]⁻ < [NO₃]⁻, indicating [BF₄]⁻ possesses the faster CO₂ transport efficiency across the electrical double layer. Furthermore, the methyl substitution effect on transport and thermodynamic properties was clarified, indicating the coupling relation between the transport process and thermodynamic advantage. These findings can lay the ground for the molecule design of ILs-electrode interface in the applications in the chemical engineering field.     

Ternary fluid lattice Boltzmann simulation of dynamic interfacial tension induced by mixing inside microdroplets

A ternary fluid color-gradient lattice Boltzmann model is proposed to investigate the effect of mixing-induced dynamic interfacial tension on the diffusive mixing of two fluids inside microdroplets moving in a third continuous phase through a baffled channel. The diffusion coefficient of binary mixtures and dynamic interfacial tension in this model can be directly defined and independently adjusted. The simulation results show that the dynamic interfacial tension between miscible binary fluids at interfaces with ambient phase would lead to the motion of the interface and redistribution of solutes inside the droplet during mixing. The larger initial interfacial tension gradient would improve mixing efficiency at early stages by promoting faster solute flow. The present model can be easily applied to quantitatively characterize the mixing behavior inside droplets in the practical processes involving the dynamic interfacial tension phenomenon and inspire new designs for mixing intensification.     

利用二维变阱宽方阱链流体分子热力学模型计算吸附等温线

以二维硬碟流体为参考,借助现代分子热力学研究方法建立了一个二维变阱宽方阱链流体的分子热力学模型(SWCF-VR-2D),并将建立的模型用于气体在固体界面吸附的关联计算中,获得了相应吸附质和吸附剂的模型参数。发现模型能满意再现氮气、甲烷、乙烷、乙烯等气体在硅胶、活性炭、沸石、金属有机骨架(MOF)等不同固体界面上的吸附等温线,总的平均绝对偏差为3.42%,其中能量参数ε _w反映了吸附剂与吸附质之间的相互作用大小。