Diffusion Equation for Spreading and Replenishment in Submonolayer Lubricant Film
Diffusion Equation for Spreading and Replenishment in Submonolayer Lubricant Film
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亚单层润滑油膜中扩散和补充的扩散方程
DOI：
10.1007/s11249-014-0455-4
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发表时间：
2015
影响因子：
3.2
通讯作者：
Kyosuke Ono
中科院分区：
文献类型：
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作者：
Kyosuke Ono
在磁头-磁盘界面技术领域，随着移动的润滑膜厚度减小到<0.3 nm，评估亚单层润滑膜的润滑效果变得越来越重要。虽然如果选择大的有效粘度值，亚单层润滑剂的扩散和补充速度可以通过常规扩散理论来评估，但是通常认为使用基于连续介质力学的常规扩散方程用于亚单层液膜是不合适的。本文提出了一个新的扩散方程，制定了平均流量的亚单层液膜与减少密度相比，堆积密度。亚单层液膜分离压力的Hamaker常数也被修改为与膜厚成正比。在亚单层膜的粘度和体积粘度之间的差异也被考虑在内。从导出的亚单层膜的扩散方程，润滑剂边界的扩展和补充过程的耗尽润滑剂表面的研究与使用传统的扩散方程得到的结果进行比较。对于具有0.24 nm厚的移动的层的Z-四醇润滑剂，亚单层润滑剂轮廓在耗尽槽中的补充过程可以从亚单层扩散理论通过使用与吹出实验测量的低粘度值一致的低粘度值来计算。
In the field of head–disk interface technology, evaluating the effects of lubrication of a submonolayer lubricant film is becoming increasingly important as the thickness of the mobile lubricant film is reduced to <0.3 nm. Although the spreading and replenishment speed of a submonolayer lubricant can be evaluated by conventional diffusion theory if a large effective viscosity value is selected, it is commonly considered inappropriate to use the conventional diffusion equation based on continuum mechanics for a submonolayer liquid film. This paper presents a new diffusion equation that formulates the averaged flow of a submonolayer liquid film with a reduced density compared to the bulk density. The Hamaker constant for disjoining pressure in the submonolayer liquid film is also modified to be proportional to the film thickness. The difference between the viscosity in the submonolayer film and the bulk viscosity is also taken into account. From the derived diffusion equation for a submonolayer film, the spreading of a lubricant boundary and replenishment process of a depleted lubricant surface are studied in comparison with the results obtained using the conventional diffusion equation. The replenishment process of submonolayer lubricant profiles in a depleted groove for the Z-tetraol lubricant with a 0.24-nm-thick mobile layer can be calculated from submonolayer diffusion theory by using a low viscosity value consistent with that measured by a blow-off experiment.