The Behavior of Amphiphile at Oil-Water Interface by Monte Carlo Simulation

A novel simple two-dimensional square-lattice model of amphiphile at oil-water interface is developed,in which oil and water act as solvent and occupy empty sites and amphiphile occupies chains of sites. In this model, the oil-water interface is fixed, And amphiphile molecules will be enriched at the oil-water interface. The interfacial concentration of amphiphile calculated by Monte Carlo method shows that it is easier for the hydrophilic-hydrophobic balanced amphiphile to stay at the interface. And the adsorption of amphiphile increases with the increase of amphiphile concentration and the decrease with temperature.

Synergistic Effect of Amphiphiles at Oil-Water Interface: By Monte Carlo Simulation

Amphiphile-oil-water system is complicated. The real behavior of amphiphile in the interface is still undnown despite that this behavior is very important in determining the stability of emulsion system. In this paper, the interface properties of amphiphile at oil-water interface were investigated by a square-lattice model Monte Carlo simulation method. The synergistic effect was found for hydrophobic and hydrophilic amphiphile mixture systems; and the synergistic effect disappears or was weakened as the amphiphile at the interface region became dilute with the increasing of temperature.

The effect of anisotropic surface tension on the morphological stability of planar interface during directional solidification

This paper considers the effect of the anisotropic surface tension on the morphological stability of the planar interface during directional solidification. When the expression exhibiting the four-fold symmetry is included, the modified absolute stability criterion is obtained by employing the multi-variable expansion method. The linear stability analysis reveals that for the given temperature gradient, as the anisotropic surface tension parameter increases, the stability zone tends to decrease.

A Kinetic Model for Describing the Effect of Proteins on the Air-Water Interface Tension

The main objective of this work was to develop a kinetic model to describe the variation of the surface tension in an air-water interface due to the adsorption of proteins from different origins and to identify quantitatively the relevant parameters, it was considered that the processes of adsorption, unfolding and reordering of the protein molecule in the interface occur simultaneously. The model used in the present work to calculate the surface tension postulates the existence of two simultaneous processes, adsorption and protein rearrangement represented with an equation of first order with two exponential components. The relevant parameter of the equation are ka and kr-the rate constants of the two first order kinetic phases that correspond to both conformational states of the protein, adsorption and rearrangement during the process of variation of the surface tension, and the amplitude parameters Aa and Ar. The results suggest that the kinetic model for the variation of the surface tension of protein solutions proposed in this work, with two simultaneous first order processes, is more appropriate than previous models to describe such variation.

Phase field modeling of ferroelastic variant switching in yttria-stabilized t'zirconia with strain gradient elasticity and interface tension

The 6–8 wt%yttria-stabilized zirconia with a tetragonal structure(t’-YSZ)is extensively employed in thermal barrier coatings.The exceptional fracture toughness of t’-YSZ can be attributed to its distinctive ferroelastic toughening mechanism.Microstructure and interface tension play a critical role in ferroelastic variant switching at the micro-and nano-scale.This paper presents an original thermodynamically consistent phase field(PF)theory for analyzing ferroelastic variant switching at the micro-and nano-scale of t’-YSZ.The theory incorporates strain gradient elasticity using higher-order elastic energy and interface tension tensor via geometric nonlinearity to represent biaxial tension resulting from interface energy.Subsequently,a mixed-type formulation is employed to implement the higher-order theory through the finite element method.For an interface in equilibrium,the effects of strain gradient elasticity result in a more uniform distribution of stresses,whereas the presence of interface tension tensor significantly amplifies the stress magnitude at the interface.The introduction of an interface tension tensor increases the maximum value of stress at the interface by a factor of 4 to 10.The nucleation and evolution of variants at a pre-existing crack tip in a mono-phase t’-YSZ have also been studied.The strain gradient elasticity is capable of capturing the size effect of ferroelastic variant switching associated with microstructures in experiments.Specifically,when the grain size approaches that of the specimen,the critical load required for variant switching at the crack tip increases,resulting in greater dissipation of elastic energy during ferroelastic variant switching.Moreover,the interface tension accelerates the evolution of variants.The presented framework exhibits significant potential in modeling ferroelastic variant switching at the micro-and nano-scale.

Diffusion-controlled Adsorption Kinetics of Surfactant at Air/Solution Interface

For the diffusion-controlled adsorption, the expression of dynamic surface adsorption P（t） was ob- tained by solving the diffusion equation. Two cases, i.e. the short and long time limits, were mainly discussed in this paper. From the measured dynamic surface tension of aqueous surfactant sodium dodecyl sulfate （SDS） solutions at 25 ℃, the adsorption kinetics of SDS at air/solution interface was studied. It was proved that for both of the short and long time limits, the adsorption process of SDS was controlled by diffusion.

Modeling Methods and Test Verification of Root Insert Contact Interface for Wind Turbine Blade

Two modeling methods of the root insert for wind turbine blade are presented,i.e.,the local mesh optimization method(LMOM)and the global modeling method(GMM).Based on the optimized mesh of the local model for the metal contact interface,LMOM is proposed to analyze the load path and stress distribution characteristics,while GMM is used to calculate and analyze the stress distribution characteristics of the resin layer established between the bushing and composite layers of root insert.To validate the GMM,a tension test is carried out.The result successfully shows that the shear strain expresses a similar strain distribution tendency with the GMM′s results.

Apparent Active Adsorption Force at a Solid-Liquid Interface with Active Adsorption

The paper presents a new relationship between the three surface tensions on the solid-liquid-vapor interface, γ_(sl)-γ_(sv)+γ_(lv)cosθ=βin order to understand the wetting on the liquid-solid interface in the case of active adsorption.The authors suggest a new force“apparent active adsorption force”βto take part in the balance at the three interface lines of contact in the solid-liquid-vapor phases,its dimen- sion isβ=Σα_iRT(Γ_i^(sl)-Γ_i^(sv)+Γ_i^(lv)cosθ),and its direction is dependent on the sign of β,whenβis a positive, the direction is agree with surface tension of the sol- id-vapor interface γ and vice versa.

PREPARATION OF PERFLUOROOCTANOYL-MODIFIED POLY(VINYL-ALCOHOL)S AND THEIR ADSORPTION AT AN AIR-WATER INTERFACE

Perfluorooctanoyl modified poly(vinyl alcohol)s (FPVA) were prepared by means of substituting a small amount of hydroxyl groups on the backbone of poly(vinyl alcohol), for which the initial degree of polymerization is equal to 1750. The substitution extent, defined by the number of substituting units in a chain, for the four FPVA samples was in the range of 0.5-5 perfluorooctanoyl groups per chain. The FPVA samples with the highest substitution extent still had good solubility in water. It was shown by experimental measurement at 30.0 +/- 0.1 degreesC that the surface tension of the aqueous solution of the highest substituted FPVA decreased to 16.6 mN/m at a higher concentration, e.g. about 0.1 g/mL. Obviously, macromolecules of FPVA exhibit a very strong tendency to adsorb at the air-water interface, because the hydrophobic perfluorooctanoyl groups in FPVA have a very high surface activity as they are in small molecular fluorinated surfactants. The chain conformation of such a model polymer adsorbed on the air-water interface was also discussed.

DEVELOPMENT OF A PRECISE ELECTRO CHEMICAL INTERFACE

Based on the circuit principle of 1186 Electro Chemical Interface preduced by Solartron Electronic Group Ltd., a precise electro chemical interface (ECI) unit, which can provide the interfacing requirements for the control and measurement of characteristics of electro chemical cell, was developed by means of some essential improvements. Not only can it be used to control and measure the steady and non-steady state characteristics, but also it can be directly connected with Solartron 1170 series or 1250 Frequency Response Analysers (FRA) to measure the AC impedance. Besides,the EC1 can also be connected with two- or three-electrode electro chemical cell systems to test convenlently and correctly their DC and AC characteristics, and used as a four-electrode potentlostat combined with four-electrode electro chernical cell system which contains two reference electrodes (RES) for researches on the electro chemical characteristics of oil-water interface, etc.

页岩油藏渗吸驱油剂体系性能评价

由于页岩油藏的超低渗透率和复杂的孔隙结构,从页岩油储层中采油仍然是一个重大挑战。表面活性剂作为一种潜在的解决方案,通过降低界面张力和改变润湿性来提高非常规油藏的原油采收率。本研究旨在通过研究页岩油储层的自发渗吸行为,评价表面活性剂在页岩油藏中的应用潜力。结果表明,复配渗吸驱油体系0.15 wt%CA-90+0.15 wt%SDS,在地层条件下界面张力降低至1.03×10^(-2)mN/m;亲油岩心片润湿接触角降低了86°,岩石润湿性由油湿转变为水湿,毛管力由油渗吸驱油阻力转变为渗吸驱油动力;在含水率为70%时,乳状液黏度降低至23.4 mPa·s,其黏度接近原油黏度,但流动性更强,更有利于提高采收率;0.15 wt%CA-90和0.15 wt%SDS的动态吸附量分别为0.85和0.97 mg/g,具有较好的抗吸附能力,对页岩渗透率伤害率低于8%;滑溜水+复配体系的渗吸采收率可以达到31.27%,相比滑溜水体系中自发渗吸采收率(19.43%)提高了11.84%,渗吸驱油效率提高了60.94%,极大地提高了页岩油藏的采收率。

耐盐型阴/阳离子表面活性剂高效渗吸体系构筑及性能评价

针对长庆安塞油田油藏条件,构建了阴离子表活剂APGSHS和双十八烷基阳离子表活剂复配的耐盐型高效渗吸体系。在矿化度为74.11 g·L^(-1)、温度为50℃的条件下,通过界面张力优选出适合该油田的最佳渗吸体系,并研究了该渗吸体系的润湿性能、乳化性能以及渗吸采油效果。结果表明:复配体系可将油水界面张力维持在10^(-3)mN·m^(-1)数量级;同时,该体系具有优异的润湿反转能力以及较佳的乳化性能,该复配体系针对0.3~30.0 mD的岩心渗吸采收率可达40%以上。

两亲SiO_(2)纳米颗粒的制备和界面扩张流变行为研究

制备了一种两亲SiO_(2)纳米颗粒,借助红外光谱及接触角测量证实了相关基团在SiO_(2)纳米颗粒表面的成功接枝,探究了其界面活性和界面扩张流变行为。通过动态界面张力测量及小幅正弦振荡实验发现,两亲SiO_(2)纳米颗粒相比亲水和疏水SiO_(2)纳米颗粒能够更稳定地吸附在界面形成一层吸附膜,降低界面张力,同时由于其扩散交换速度较慢,界面扩张模量大于亲水和疏水SiO_(2)纳米颗粒。进一步的大幅线性压缩实验发现两亲SiO_(2)纳米颗粒在表面比为0.35时其界面吸附量会发生激增,扩张模量迅速增大,其形成的界面膜具有抵抗较大程度形变的能力。

采空区碳封存条件下CO_(2)-水界面特性及溶解传质规律

采空区CO_(2)封存作为解决煤炭行业碳排放难题的重要负碳技术储备,在采空区废弃资源二次利用、CO_(2)封存等方面具有广泛的应用前景。利用原位界面张力测定仪开展了不同温压、地层水矿化度及阳离子溶液类型对CO_(2)地层水系统的界面张力(IFT)影响规律实验,明晰了CO_(2)注入含水碎胀煤岩体中的气液界面扩散效应,并将基于统计缔合理论结合兰纳−琼斯势能模型的状态方程(SAFT-LJ状态方程)与密度梯度理论(DGT)结合预测了IFT理论值;利用自主研发的地质封存地化反应模拟实验平台对相同条件下的CO_(2)溶解性进行了探究实验,得到了采空区储层环境下CO_(2)溶解度变化特征,采用D-S模型计算了对应CO_(2)溶解度理论值。实验结果表明:环境温度一定时,采空区储层压力与IFT呈线性负相关关系,储层温度升高,IFT相应增加,但变化幅度较小;温压条件一定时,矿化度与IFT存在正相关性,且在本实验范围内,低压、高温、高矿化度会促使IFT升高;CO_(2)−盐溶液之间的IFT呈现出随着阳离子价态升高而增大的现象(K^(+)<Na^(+)<Ca^(2+)<Mg^(2+));采空区储层压力与CO_(2)溶解度呈正相关关系,当温度为25℃、纯水条件下,压力由0.5 MPa增至2.5 MPa,对应CO_(2)溶解度由0.1627 mol/kg升至0.7141 mol/kg;CO_(2)溶解度随着温度与矿化度的升高而降低;相同质量分数下,一价阳离子溶液(NaCl、KCl)比二价阳离子溶液(CaCl_(2)、MgCl_(2))可溶解更多的CO_(2)。注入采空区中的游离相CO_(2)克服界面张力通过扩散溶解传质作用打破了采空区地层的地球化学平衡,通过明确环境温压条件、采空区水环境对IFT及CO_(2)溶解度的影响规律,阐明CO_(2)地层水气液界面效应及溶解传质机理,以期为采空区CO_(2)封存安全性及封存量评估提供理论基础。

偏远井场油水分离与原油降凝技术研究

为解决延长油田部分偏远井场含水原油在井场脱水困难,冬季原油凝固流动性差外运难的问题,开展破乳剂类型、温度、浓度影响的破乳特性实验、微观形貌采集以及降凝流变特性实验,寻求高效脱水与降凝方案,通过实验结果制定生产改造方案实现高效脱水与降凝。研究表明井场破乳脱水与降凝的关键在于药剂与产液的充分融合,同时破乳剂的加入使活性水的界面张力明显下降,浓度为100ppm时,活性水的界面张力达到了最低值。通过微观形貌观察,随着破乳剂浓度的增加,油滴的粒径先增大后减小,油滴分布先稀疏后密集,在浓度为100ppm时油滴的粒径达到最大,此时界面张力最低,活性较高,破乳剂能够快速取代天然表面活性物质,导致原油破乳,破乳率达到97%以上。当破乳后未加降凝剂时原油最优热处理温度在60至70℃之间,添加浓度为150ppm的J2降凝剂,加热至50℃,凝点降低至-2~4℃。

拉压复合型锚杆锚固机理的数值及模型试验应用研究

针对全长注浆锚杆在深部隧洞中支护作用的局限性,为有效控制隧洞围岩变形、增强锚杆承载性能,本文采用有限元数值模拟法深入研究拉压复合型锚杆支护结构在岩石隧道加固过程中受到拉拔荷载作用下的界面失效特征及力学传递机制,并将锚杆应用在超载模型试验中,探究锚杆的支护性能。研究结果表明:锚固体与围岩相互作用接触界面的力学演化共经历了弹性阶段、塑性软化阶段、完全滑移阶段的渐进式失效过程。界面剪切力的传递也是从拉拔荷载较小时出现在承载板处,随拉拔荷载增大,向锚固段两侧转移,呈现双峰趋势。根据锚杆界面剪切力分布规律,提出了复合锚杆在低荷载和高荷载拉拔作用下的剪切力分布模型,此模型具有普遍性,进行的室内超载模型试验得出复合锚杆支护效果优于普通锚杆的结论,此研究可为复合锚杆在深埋隧洞等地下工程中的应用提供一定的参考价值。

铝粒尺寸及入炉高度对运动轨迹的影响

二次精炼过程中,铝是钢液进行脱氧及合金化的主要物料之一,但纯铝的密度小于钢液,能否穿越渣层与钢液接触及接触时间对铝的脱氧效果和钢中溶解铝的含量有直接影响。在忽略铝的熔化、溶解及化学反应的情况下,通过对铝粒运动过程受力分析,建立铝粒在气-渣-钢相内的三维运动数学模型,明晰铝粒尺寸及入炉高度对铝粒运动轨迹的影响。结果表明:在渣层厚度为70 mm且入炉高度为1~1.5 m的情况下,1 mm和5 mm的铝粒在渣钢界面处波动;入炉高度为1 m时,粒径为10 mm的铝粒停留在渣钢界面处,但在入炉高度为1.5 m及以上时可以进入钢液;20 mm及以上尺寸的铝粒可以进入钢液。在入炉高度为1 m时、30 mm尺寸的铝粒在钢液中的停留时间与深度相较于20 mm的基础上分别增加22.86%和50.00%;在铝粒尺寸为20 mm时、入炉高度为1.5 m时的铝粒在钢液中的停留时间与深度在1 m的基础上分别增加5.71%和10.00%。增加钢渣界面张力、减小钢铝界面张力或增加渣铝界面张力有利于铝粒进入钢液,而铝粒的尺寸大于20 mm,界面张力对铝块运动几乎没有影响;增大密度会使钢芯铝在钢液中停留更长时间,有利于钢液脱氧。

桥梁施工中钢抱箍滑移原因与防滑措施研究

为研究桥梁施工中钢抱箍滑移原因并提出针对性的应对措施,对钢抱箍受力进行理论分析。针对钢-混界面进水及螺栓施拧不足造成的滑移,进行钢-混界面摩擦系数和螺栓拧紧力矩系数测试及定量分析,根据测试结果并结合现场经验提出钢抱箍防滑措施。结果表明:实测干燥状态下钢-混界面的静摩擦系数为0.62,大于常用设计值(0.3~0.4),钢抱箍偏安全;界面润湿后,静摩擦系数有所降低,但仍高于常用设计值,说明钢-混界面进水会降低钢抱箍承载能力,但降低程度还不足以导致钢抱箍滑移。螺栓拧紧力矩系数取值不当是钢抱箍滑移的主要原因,拧紧力矩系数常用设计值仅为测试值的1/1.7~1/3.6,偏不安全;拧紧力矩系数取值跟螺栓轴线与承压板法线间的夹角有关,建议现场对其进行实测,以保证螺栓预紧力与设计相符。钢抱箍设计时,摩擦系数可偏安全地取0.45,螺栓拧紧力矩系数可在参考范围内取大值,并结合1.5~2.0的安全系数确定螺栓数量,以避免钢抱箍滑移。

表面活性剂化学性能分析及提高致密油田采收率实验研究

自制了一种适用于致密砂岩油藏驱采的表面活性剂FDP,利用X射线衍射仪、扫描电镜及界面张力仪等手段分析了目标油藏的储层特性,测试了FDP对岩石界面张力与润湿性的影响特性,利用岩心驱替实验装置评价了表面活性剂FDP与SDS溶液驱油时静态吸附与动态吸附特性,对比分析了其在渗吸采收率方面的效用。结果表明:表面活性剂FDP在多孔介质中可有效通过改变岩石润湿性、降低油水界面张力及乳化作用实现驱油效果。目标区块油藏孔隙类型主要为长石溶孔,其间连通性差,整体表现为弱亲水性。0.02%FDP体系,其油水界面张力仅为2.33 mN·m^(-1),三相接触角低于30°,其在静态渗吸与动态渗吸中的渗吸采收率均显著高于SDS体系,可有效提高致密砂岩油藏采收率。

基于分子动力学方法的致密砂岩储层CO_(2)驱油研究进展

随着致密砂岩储层CO_(2)-EOR项目的不断增加,亟需对CO_(2)与致密砂岩储层流体在孔隙介质中的相互作用机理进行研究,但室内实验难以观察到CO_(2)与流体在孔隙通道中的动态过程,而分子动力学模拟则可以弥补传统实验和数值方法的不足。为此,围绕该方法在CO_(2)-EOR研究中的2大重点——界面行为与受限空间运移行为,对包括萃取、溶胀、降黏、降低界面张力、最小混相压力、润湿性等6个方面界面行为的相关研究成果进行了系统梳理,结合前人对CO_(2)与致密砂岩储层流体在受限空间中运移行为的研究成果,提出了分子动力学在致密砂岩储层CO_(2)-EOR研究中的关键科学问题。研究结果表明:①分子动力学能够很好地将CO_(2)萃取原油中—轻烃组分的过程进行可视化,建议根据原油实际组分构成分析CO_(2)的萃取能力,从而弄清CO_(2)萃取原油中各组分的优先顺序及效率;②有关CO_(2)分子对原油溶胀降黏作用的研究,大多数成果中的原油组分体系较为单一,建议根据实际储层的原油组分,系统探讨高温高压条件下CO_(2)的溶胀降黏作用;③对于CO_(2)与油水两相之间界面张力的研究更多是在体相中进行展开,而在纳米受限空间界面行为的研究还有待完善;④有关地层水在孔隙壁面的润湿性研究,对不同因素之间的协同效应影响润湿性的机理尚不明确。结论认为,随着量子力学研究的不断深入以及计算性能的日益强大,该方法可以在更大尺度上进行复杂体系的计算,以其为基础的油藏、页岩油气藏CO_(2)-EOR机理等研究将会取得较大的突破。