Effect of roughness on surface force distributions measured by newly developed surface force apparatus with ultra-high accuracy
Effect of roughness on surface force distributions measured by newly developed surface force apparatus with ultra-high accuracy
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DOI：
10.1177/1350650116632019
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发表时间：
2016-11-01
影响因子：
2
通讯作者：
Omata, Yukiko
中科院分区：
文献类型：
--
作者：
Kato, Takahisa;Inoue, Tomoyuki;Omata, Yukiko
利用一种新研制的表面力装置（SFA）精确地研究了球体与平板之间的拉脱力。在该系统中，（1）在真空中测量球形玻璃探针与样品板之间的拉脱力，（2）通过电磁力直接将探针从样品上拉脱，以及（3）分别以0.4nN和0.3nm的超高分辨率测量探针的拉脱力和位移，这是电噪声水平。该系统能够清晰地测量作为力曲线一部分的拔出过程，并且拔出力的测量具有较高的重现性和准确性。拉脱力分布的平面上的Si，SrTiO 3，玻璃碳，和类金刚石碳的测量。结果表明，尽管这些材料之间存在差异，但对于所有四种材料，其分布强烈依赖于表面粗糙度，因此拉脱力的相对标准偏差与表面粗糙度（R-a和R-z）成比例。然后使用Greenwood和威廉姆森（GW）模型分析拔出力。通过与SFA实验结果的比较，发现GW模型可以较好地预测拉脱力和分离位移，且拉脱力强烈依赖于表面高度的标准差，导致拉脱力在粗糙表面的分布范围较宽.
A pull-off force between a sphere and a flat plate is precisely investigated using a newly developed surface force apparatus (SFA). In this system, (1) a pull-off force between a spherical glass probe and a sample plate is measured in vacuum, (2) the probe is directly pulled off from the sample by an electromagnetic force, and (3) the pull-off force and displacement of the probe are measured with ultra-high resolution of 0.4 nN and 0.3nm, respectively, which are electrical noise levels. The pull-off process, which appears as a part of force curve, is clearly measured by this system, and pull-off force is measured with high reproducibility and accuracy. Pull-off force distributions on flat surfaces of Si, SrTiO3, glassy carbon, and diamond-like carbon are measured. It is shown that despite the differences between these materials, for all four for them, the distribution strongly depends on the surface roughness, such that the relative standard deviation of pull-off force is proportional to the surface roughness (R-a and R-z). The Greenwood and Williamson (GW) model is then used for the analysis of the pull-off force. Comparing with SFA experiments, it is shown that the pull-off force and separation displacement can be predicted by the GW model and that the pull-off force strongly depends on the standard deviation of surface height, causing the broad distribution of pull-off force at rough surfaces.