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The kinetics of the shear-induced surface-to-bulk transport of methyl thiolate species formed from dimethyl disulfide (DMDS) on a copper surface are explored. It is found that the loss of surface species as a function of the number of rubbing cycles can be modeled by assuming that the adsorbed layer penetrates the subsurface a distance of ~0.7 nm per scan. Adding wear to this model does not improve the fit to the experimental data providing an upper limit for the wear rate of ~0.06 nm/scan. This model is applied to analyzing the depth distribution of sulfur within the subsurface region as a function of the number of rubbing cycles, measured by Auger depth profiling when continually dosing the copper sample with DMDS. It is found that the shape of the experimental depth profile is in agreement with the model developed to analyze the surface-to-bulk transport kinetics of the adsorbed layer. However, the profiles are almost identical for surfaces that have been rubbed 130 and 360 times, so that the surface-to-bulk transport kinetics are self limiting. 相似文献
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M. Yanagisawa 《摩擦学汇刊》2013,56(3):629-635
Mobility of molecularly thin lubricant film is an important issue in understanding boundary lubrication mechanisms and to develop reliable magnetic disk media. Intra-molecular mobility for a perfluorinated poly ether (PFPE), which is used as a disk lubricant, with two hydroxyl groups on a sol-gel SiO2 surface, which is used for a protective overcoat for plated magnetic disks, was studied using nuclear magnetic resonance (NMR). Thin film viscosities for molecular segments were derived from a relaxation time. The viscosity for the hydroxyl segment is 1.8 to 11 times as much as that for a bulk lubricant at room temperature, and the viscosity rate increased with increasing temperature. For example, it increased 15 times at 100°C. The viscosities for the segments in a main chain were not different from that of bulk PFPE. A spin-off calculation for the molecularly thin lubricant film with thin film viscosity, derived from the NMR method, shows that there is no thickness decrease after seven years. 相似文献
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Under the effects of high shear rate and confinement between solid surfaces, the behavior of a thin lubricant film deviates
from that of the bulk, resulting in significant increases of lubricant viscosity and interfacial slip. A semi-empirical model
accounting for the breakdown of continuum theory at the nanoscale is proposed—based on film morphology and chemistry from
available experimental and molecular dynamics simulation data—to describe lubricant behavior under shear. Viscosity stiffening
and interfacial slip models are introduced into the formulations of the normal (bearing) and shear forces acting on a sphere
that moves within a thin lubricant film parallel to a rigid plane. The experimentally measured ‘apparent’ viscosity confounding
the effects of both stiffening and slip is used to predict the hydrodynamic forces acting on a fully or partially submerged
sphere for the purposes of describing lubricant contact in magnetic storage. The proposed sphere-on-flat model forms the basis
of a future, dynamic contact with friction model that will account for lubricant contact in the context of molecularly thin
lubricated rough surface contact. 相似文献
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尼古丁印迹聚合物分子识别特性的光谱研究 总被引:1,自引:0,他引:1
以尼古丁为模板分子,甲基丙烯酸为功能单体,乙二醇二甲基丙烯酸酯为交联剂,合成尼古丁分子印迹聚合物。采用紫外光谱和1H核磁共振波谱研究了该印迹聚合物的结合位点和识别机理。结果表明,该聚合物中尼古丁与甲基丙烯酸通过协同氢键作用形成1:2型配合物。甲基丙烯酸分子中羧基氢原子是氢键的质子给予体;尼古丁分子吡啶环和四氢吡咯环上的两个氮原子是接受质子的识别位点。该印迹聚合物通过协同氢键作用选择性的识别尼古丁分子。 相似文献
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分析了薄膜吹塑模芯螺旋槽的特点,用通用模具软件进行了设计造型和加工仿真,并在四轴数控加工中心机上生产出模芯,已应用于多层吹塑模具产品中。 相似文献
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基于尺度分离理论,近壁微液膜波动特性对临界热负荷的产生有至关重要的影响。针对水平管内分层流动近壁微液膜在气流剪切应力作用下的波动特性进行研究,分析声学法,射线法,电学法和光学法等不同检测方法在近壁薄液膜厚度测量上的应用,并比较各种方法的优缺点。最终采用光学法,即利用光谱共焦位移传感器,对不同气、液流速条件下近壁微液膜进行测量,分析剪切夹带对液膜厚度变化的影响规律,获得液膜撕裂的临界条件。研究结果表明:微液膜平均厚度在气流剪切夹带影响下随气速的增大而减小。由于液滴夹带现象影响程度的不同,在不同气、液流速条件下,试验段出口处液膜平均厚度液膜呈现线性或非线性的变化趋势。气流剪切应力增大时,液膜厚度超过临界厚度即发生撕裂现象,液膜撕裂存在随机性,当壁面条件一定时,临界液膜厚度不随气、液流速的变化而变化,但在高气、液流速条件下液膜波动加剧。 相似文献
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本文提出了压电薄膜微马达的工作原理,介绍了该马达的优良性能、结构形式和加工工艺,最后指出了该马达研制的关键技术以及应用前景。 相似文献
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The sliding contact between two rough surfaces in the presence of a molecularly thin lubricant layer is investigated. Under
very high shear rates, the lubricant is treated as a semi-solid layer with normal and lateral shear-dependent stiffness components
obtained from experimental data. The adhesive force in the presence of lubricant is also adapted from the Sub-boundary lubrication
model and improved to account for variation in surface energy with penetration into the lubricant layer. A model is then proposed,
based on the Improved sub-boundary lubrication model, which accounts for lubricant contact and adhesion and its validity is
discussed. The model is in good agreement with published experimental measurements of friction in the presence of molecularly
thin lubricant layers and suggests that a molecularly thin lubricant bearing could be successfully used to reduce solid substrate
damage at the interface. 相似文献
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Interferometry has been widely utilized in elastohydrodynamic lubrication (EHL) film measurement since the 1960s. In-depth
optical analyses are required to get more fundamentals of optical EHL film tests. In this paper, a stratified-layer model
of optical EHL contact is numerically analyzed by the multi-beam interference approach. It is revealed that the high reflectance
of the beam-splitter and the steel interface generate a deviation of the intensity profile from the two-beam interference.
Previous experimental results about fringe contrast are reproduced, and the determination of the beam-splitter layer is theoretically
clarified. Furthermore, some characteristics of spectrometry for ultra-thin film measurement are studied, and the dependence
of the interference spectrum on the spacer layer thickness is displayed. The measurement simulation has theoretically confirmed
the constant initial phase change assumed in practical measurement. It is theoretically demonstrated that in the spectrometry
approach, TiO2 layer can generate spectrum with high finesse and may be used in the future application. The theoretical results in this
paper are correlated with previous experimental practices, and the optical EHL technique can therefore be much better theoretically
understood. 相似文献
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This paper discusses the effect of the electric double layer on a very thin water lubricating film with and without consideration of the elastic deformation of the opposing surfaces. A modified Reynolds equation that considers the electric double layer is used in a numerical analysis. The effect of zeta potential on the film thickness and pressure is numerically calculated. For both hydrodynamic and elastohydrodynamic cases, the electric double layer significantly increases the lubricating film thickness. The pressure is also marginally increased, as illustrated in the hydrodynamic analysis. However, the effect on pressure is almost unnoticeable in the elastohydrodynamic analysis. Overall, the electric-double-layer effect is only significant for a water-film thickness of less than approximately 100 nanometers. 相似文献
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