【作者】 左启阳；

【导师】 黄平；

【作者基本信息】 华南理工大学 ， 机械设计及理论， 2012， 博士

【摘要】 双电层是在固／液界面处普遍存在的一种现象,它的影响范围大致是在几十纳米之间。一个润滑系统有两个固／液界面,因此通常就存在两个双电层。研究表明：当润滑膜厚度小于100nm时,润滑性能将会受到双电层的明显影响。双电层对纳米尺度润滑的影响通常来自于两大方面：一方面是润滑区中两个双电层间的相互吸引或排斥作用,这相当于给润滑系统额外增加或减小了载荷；另一方面是双电层引发的动电效应,在润滑区中产生所谓的电粘度和电粘滞力现象。相应地,本文的研究范畴也就涉及了双电层间相互作用力和动电效应这两大方面对纳米级薄膜润滑的影响。首先,针对早前已有的研究均是基于对称双电层结构的不足之处,本文建立了考虑非对称双电层效应的薄膜润滑数学模型。基于非对称双电层的相互作用理论,从新的角度出发推导得出摩擦副的两个非对称双电层在流体动压润滑区中所引发的流动电势的计算公式,进而建立了考虑非对称双电层影响的修正的Reynolds方程和得到相应的电粘度计算公式。本文所建立的数学模型揭示了双电层对薄膜润滑性能影响所表现出来的“合效应”现象,其成果使相关的研究范畴由早前的双电层对称结构延伸至非对称结构领域。接着,利用本文所建立的非对称双电层薄膜润滑数学模型进行的详细数值分析,揭示了双电层在流体动压润滑区中引发的电粘度和流动电势的分布规律,同时也进一步发现了在弹流润滑区中双电层的存在令较薄润滑膜的厚度显著增加,但对润滑膜压力分布的影响不大等现象。此外,本文的另一大研究成果是考察了双电层厚度和双电层引发的电粘度这两者分别随电解质浓度和温度的变化规律,并以陶瓷水润滑作为分析对象,结合双电层厚度与电粘度随浓度和温度变化的复合函数关系来分析各类陶瓷材料点、线接触热弹流润滑的膜厚和压力分布受双电层的影响情况。把热弹流润滑区中的热现象与热效应影响考虑进了双电层效应的研究当中,是本文对双电层薄膜润滑理论研究的重大深化。最后,本文根据原子力显微镜的曲线测量模式的基本原理,制定了利用原子力显微镜的“力-距离曲线”模式测量双电层间作用力和“振幅-距离曲线”测量双电层动电效应的实验方案,并通过由同种材料和不同种材料的探针和样品来构建对称与非对称双电层的方法来展开实验研究,在高精度和高分辨率的实验平台下观察到了双电层间相互作用在不同介质情况下的各种表现。本文所开展的实验工作是对双电层效应研究的一次新的尝试，是本文理论研究的重要补充，并为今后的相关研究提供了新的思路，所得的实验结果也会对受双电层效应影响下的纳米尺度润滑控制具有一定指导意义。更多还原

【Abstract】 The electric double layer (EDL) about dozens of nanometres thick widely exists in thesolid/liquid interface. In general, there are two solid/lubricant interfaces in a lubricationsystem, i.e. two EDLs accordingly. Some previous studies showed that the influence of theEDLs on the lubrication properties is significant under the condition of lubricating film lessthan100nanometers.The influence of the EDLs on the nano-scale lubrication is usually caused by thefollowing two factors. One is the attractive or repulsive interaction between the two EDLs oflubrication regime which is equivalent to increase or decrease the load. The other is theelectrokinetic effect caused by the EDLs which lead to the phenomena of the electro-viscosityand electro-viscous force. Accordingly, the study of this paper focuses on the influences ofthe interaction between the two EDLs and the electrokinetic effect on the nano-scale thin filmlubrication (TFL).Firstly, a new mathematical model of TFL considering the asymmetrical EDLs effect isdeveloped in the light of the shortcomings of the previous related models, which were usuallybased on the hypothesis that the structures of the two EDLs are symmetrical. Based on therelated researches of the interaction of asymmertrical EDLs, a computational formula of thestreaming potential induced by the asymmetrical EDLs of the two friction surfaces is derivedfrom a new perspective. Then, a modified Reynolds equation with consideration of theasymmetrical EDLs effect containing the corresponding computational formula of theelectro-viscosity is developed. The mathematical model developed in this paper reveals thatthe effect of EDLs actually originates from the “combined action” of the two EDLs regardlessof the respective EDL structures of two friction surfaces. Therefore, the present theory isconcerned with an extension of the EDLs structures from the symmetrical to theasymmetrical.Then, the detailed numerical analyses are carried out by taking the advantage of themathematical model concerning the asymmetrical EDLs effect. The analysis results reveal theregularities of both distributions of the electro-viscosity and the streaming potential which isinduced by the asymmetrical EDLs in the lubrication regime. The results also show that theexistence of the EDLs leads to a noticeable increase in the film thickness of EHL, but theEDLs effect on the EHL pressure is minimal.Besides, there are another achievement that the variations both of the EDL thickness andthe electro-viscosity induced by EDLs with the electrolyte concentration and the temperature were respectively investigated. Then, the EDLs effect on the film thickness and the pressuredistribution of the thermal EHL system consisting of all kinds of ceramic or metallic pointand line contacts with aqueous solution is evaluated by the numerical analysis. It is a greatinnovation in the study of EDLs effect on TFL that considers the thermal phenomenon andheat effect generated in the thermal EHL regime in this paper.Finally, according to the principle of the curve-measurement modes of AFM, theexperimental programs have been planned in order to measure the interaction between twoEDLs by using the force-vs-distance curve mode and the electrokinetic effect caused by EDLsusing the amplitude-vs-distance curve mode of AFM. In addtion, the experimental programsinvolving the symmetrical and the asymmetrical structures of EDLs are established by theprobes and samples which both are the same or the different materials respectively.Subsequently, taking advantage of the apparatus that possess the feature of high precision andhigh resolution, i.e. AFM, the experimental researchs have been carried out to observe thevarious performances of the interaction of EDLs and the electrokinetic effect under thedifferent aqueous solution conditions. The experimental work presented in this paper is aninnovation in the study of the EDLs effects and a significant supplement of the theoreticalresearch of this paper. Furthermore, it provides a new idea for the future related study, and theexperimental results may guide the nano-scale lubricating control under the influence ofEDLs effect.更多还原