An Investigation on the Reduced Ability of IF-MoS2 Nanoparticles to Reduce Friction and Wear in the Presence of Dispersants
An Investigation on the Reduced Ability of IF-MoS2 Nanoparticles to Reduce Friction and Wear in the Presence of Dispersants
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DOI：
10.1007/s11249-014-0381-5
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发表时间：
2014-09-01
影响因子：
3.2
通讯作者：
Cavoret, Jerome
中科院分区：
文献类型：
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作者：
Rabaso, Pierre;Dassenoy, Fabrice;Cavoret, Jerome
无机类富勒烯二硫化钼（IF-MoS2）纳米颗粒在严格的边界润滑条件下，当单独添加到基础油中时，表现出极大的摩擦和减少磨损的能力。本研究研究了IF-MoS2纳米颗粒在全配方润滑油中的应用，发现在分散剂的存在下，IF-MoS2纳米颗粒的摩擦学优势消失了。为了了解琥珀酰亚胺类分散剂对纳米颗粒有效润滑所需的三个阶段的影响，即(1)纳米颗粒通过接触面(2)接触面内IF-MoS2的脱落(3)释放的MoS2薄片在摩擦表面的粘附。在三种参考油（仅含IF-MoS2的基础油，仅含分散剂和IF-MoS2和分散剂）上使用了各种实验技术。分散剂通过减少纳米颗粒的团聚来改善纳米颗粒在油中的分散，但阻止了低摩擦二硫化钼摩擦膜在钢表面的粘附。原位接触可视化显示，纳米颗粒通过接触，分散良好，摩擦学测试后观察到纳米颗粒脱落。这些结果表明，纳米颗粒分散本身似乎并不是影响纳米颗粒有效性的一个问题，尽管团聚体尺寸和惯性的减小可能会影响纳米颗粒在接触点附近的流动，以及接触点内的包裹和剥离条件。然而，琥珀酰亚胺类分散剂的使用可能会影响接触的摩擦化学性质，因为它会在钢表面过度吸附和/或封装释放的MoS2薄片，从而阻止摩擦膜的粘附。在分散剂浓度非常低且经过磨合期后，纳米颗粒分散和摩擦减少之间最终找到了平衡。在此基础上讨论了琥珀酰亚胺类分散剂的作用及其对纳米颗粒润滑的影响。
Inorganic fullerene-like molybdenum disulfide (IF-MoS2) nanoparticles are known to exhibit great friction and wear-reducing abilities in severe boundary lubrication regimes, when added to a base oil alone. Their use in fully formulated lubricants was investigated in this study, and the tribological benefits attributed to the IF-MoS2 nanoparticles were found to be lost in the presence of dispersants. Various experimental techniques were used on three reference oils (base oil containing only IF-MoS2, only dispersants and both IF-MoS2 and dispersants) in order to understand the effect of succinimide-based dispersants on the three phases needed for effective nanoparticle-based lubrication, namely (1) the passing of the nanoparticles through the contact (2) the exfoliation of the IF-MoS2 inside the contact and (3) the adhesion of the released MoS2 platelets on the friction surfaces. The dispersants were shown to improve the dispersion of the nanoparticles in the oil by reducing their agglomeration, but prevented the adhesion of a low-friction MoS2 tribofilm on the steel surfaces. In-situ contact visualization revealed that the well-dispersed nanoparticles passed through the contact and exfoliated nanoparticles were observed after tribological testing. These results imply that nanoparticle dispersion itself does not seem to be an issue concerning nanoparticle effectiveness, even though the reduced agglomerate size and inertia may have affected nanoparticle flow near the contact, as well as entrapment and exfoliation conditions inside the contact. The use of succinimide-based dispersants may, however, have affected the tribochemistry of the contact, by an excessive adsorption on the steel surfaces and/or by encapsulating the released MoS2 platelets, preventing tribofilm adhesion. A balance was finally found between nanoparticle dispersion and friction reduction, but for very low dispersant concentrations and after a running-in period. The role of succinimide-based dispersants and their effect on nanoparticle lubrication were discussed in the light of these results.